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Sample records for savanna landscape developing

  1. Ecological Thresholds in the Savanna Landscape: Developing a Protocol for Monitoring the Change in Composition and Utilisation of Large Trees

    PubMed Central

    Druce, Dave J.; Shannon, Graeme; Page, Bruce R.; Grant, Rina; Slotow, Rob

    2008-01-01

    Background Acquiring greater understanding of the factors causing changes in vegetation structure - particularly with the potential to cause regime shifts - is important in adaptively managed conservation areas. Large trees (≥5 m in height) play an important ecosystem function, and are associated with a stable ecological state in the African savanna. There is concern that large tree densities are declining in a number of protected areas, including the Kruger National Park, South Africa. In this paper the results of a field study designed to monitor change in a savanna system are presented and discussed. Methodology/Principal Findings Developing the first phase of a monitoring protocol to measure the change in tree species composition, density and size distribution, whilst also identifying factors driving change. A central issue is the discrete spatial distribution of large trees in the landscape, making point sampling approaches relatively ineffective. Accordingly, fourteen 10 m wide transects were aligned perpendicular to large rivers (3.0–6.6 km in length) and eight transects were located at fixed-point photographic locations (1.0–1.6 km in length). Using accumulation curves, we established that the majority of tree species were sampled within 3 km. Furthermore, the key ecological drivers (e.g. fire, herbivory, drought and disease) which influence large tree use and impact were also recorded within 3 km. Conclusions/Significance The technique presented provides an effective method for monitoring changes in large tree abundance, size distribution and use by the main ecological drivers across the savanna landscape. However, the monitoring of rare tree species would require individual marking approaches due to their low densities and specific habitat requirements. Repeat sampling intervals would vary depending on the factor of concern and proposed management mitigation. Once a monitoring protocol has been identified and evaluated, the next stage is to

  2. Fire in Australian savannas: from leaf to landscape

    PubMed Central

    Beringer, Jason; Hutley, Lindsay B; Abramson, David; Arndt, Stefan K; Briggs, Peter; Bristow, Mila; Canadell, Josep G; Cernusak, Lucas A; Eamus, Derek; Edwards, Andrew C; Evans, Bradley J; Fest, Benedikt; Goergen, Klaus; Grover, Samantha P; Hacker, Jorg; Haverd, Vanessa; Kanniah, Kasturi; Livesley, Stephen J; Lynch, Amanda; Maier, Stefan; Moore, Caitlin; Raupach, Michael; Russell-Smith, Jeremy; Scheiter, Simon; Tapper, Nigel J; Uotila, Petteri

    2015-01-01

    Savanna ecosystems comprise 22% of the global terrestrial surface and 25% of Australia (almost 1.9 million km2) and provide significant ecosystem services through carbon and water cycles and the maintenance of biodiversity. The current structure, composition and distribution of Australian savannas have coevolved with fire, yet remain driven by the dynamic constraints of their bioclimatic niche. Fire in Australian savannas influences both the biophysical and biogeochemical processes at multiple scales from leaf to landscape. Here, we present the latest emission estimates from Australian savanna biomass burning and their contribution to global greenhouse gas budgets. We then review our understanding of the impacts of fire on ecosystem function and local surface water and heat balances, which in turn influence regional climate. We show how savanna fires are coupled to the global climate through the carbon cycle and fire regimes. We present new research that climate change is likely to alter the structure and function of savannas through shifts in moisture availability and increases in atmospheric carbon dioxide, in turn altering fire regimes with further feedbacks to climate. We explore opportunities to reduce net greenhouse gas emissions from savanna ecosystems through changes in savanna fire management. PMID:25044767

  3. Fire in Australian savannas: from leaf to landscape.

    PubMed

    Beringer, Jason; Hutley, Lindsay B; Abramson, David; Arndt, Stefan K; Briggs, Peter; Bristow, Mila; Canadell, Josep G; Cernusak, Lucas A; Eamus, Derek; Edwards, Andrew C; Evans, Bradley J; Fest, Benedikt; Goergen, Klaus; Grover, Samantha P; Hacker, Jorg; Haverd, Vanessa; Kanniah, Kasturi; Livesley, Stephen J; Lynch, Amanda; Maier, Stefan; Moore, Caitlin; Raupach, Michael; Russell-Smith, Jeremy; Scheiter, Simon; Tapper, Nigel J; Uotila, Petteri

    2015-01-01

    Savanna ecosystems comprise 22% of the global terrestrial surface and 25% of Australia (almost 1.9 million km2) and provide significant ecosystem services through carbon and water cycles and the maintenance of biodiversity. The current structure, composition and distribution of Australian savannas have coevolved with fire, yet remain driven by the dynamic constraints of their bioclimatic niche. Fire in Australian savannas influences both the biophysical and biogeochemical processes at multiple scales from leaf to landscape. Here, we present the latest emission estimates from Australian savanna biomass burning and their contribution to global greenhouse gas budgets. We then review our understanding of the impacts of fire on ecosystem function and local surface water and heat balances, which in turn influence regional climate. We show how savanna fires are coupled to the global climate through the carbon cycle and fire regimes. We present new research that climate change is likely to alter the structure and function of savannas through shifts in moisture availability and increases in atmospheric carbon dioxide, in turn altering fire regimes with further feedbacks to climate. We explore opportunities to reduce net greenhouse gas emissions from savanna ecosystems through changes in savanna fire management.

  4. Fire in Australian Savannas: from leaf to landscape

    NASA Astrophysics Data System (ADS)

    Beringer, J.

    2015-12-01

    Savanna ecosystems comprise 22% of the global terrestrial surface and 25% of Australia (almost 1.9 million km2) and provide significant ecosystem services through carbon and water cycles and the maintenance of biodiversity. The current structure, composition and distribution of Australian savannas have co-evolved with fire, yet remain driven by the dynamic constraints of their bioclimatic niche. Fire in Australian savannas influences both the biophysical and biogeochemical processes at multiple scales from leaf to landscape. Here we present the latest emission estimates from Australian savanna biomass burning and their contribution to global greenhouse gas budgets. We then review our understanding of the impacts of fire on ecosystem function and local surface water and heat balances, which in turn influence regional climate. We show how savanna fires are coupled to the global climate through the carbon cycle and fire regimes. We present new research that climate change is likely to alter the structure and function of savannas through shifts in moisture availability and increases in atmospheric carbon dioxide (CO2), in turn altering fire regimes with further feedbacks to climate. We explore opportunities to reduce net greenhouse gas emissions from savanna ecosystems through changes in savanna fire management.

  5. A spatio-temporal analysis of landscape dynamics under changing environmental regimes in southern African savannas

    NASA Astrophysics Data System (ADS)

    Bunting, Erin L.

    The United Nations and Intergovernmental Panel on Climate Change (IPCC) deem many regions of southern Africa as vulnerable landscapes due to changing climatic regimes, ecological condition, and low adaptive capacity. The savanna ecosystems of southern Africa are of great ecological importance due to the high biodiversity they sustain, their high level of productivity, and the great role they play in the global carbon cycle. Given the dependence of humans on the lands it is essential to explore landscape level trends in patterns and processes in an effort to inform management practices. Even if climate change mitigation strategies were put in place, this is still a region heavily dependent on rain-fed agriculture and tourism of the biological diverse lands. Therefore analysis of climate variability, both interannual and intra-annual, and the changing role it plays on the landscape is critical. This body of research analyzes the role of climate variability and climate on environmental condition and socio-economic development via research on (1) spatial and temporal vegetation patterns, (2) the underlying processes that influence savanna ecosystem resilience, (3) local perception of risk to livelihood development, and (4) potential consequences of climate change on vegetation patterns. As a whole this demonstrates the key role that climate plays on savanna landscapes, which would be highly beneficial when developing conservation or mitigation strategies. Increased climate variability is occurring, but what is still open to debate is the resilience of savanna landscape and vulnerability of socio-economic development.

  6. Soil carbon in savanna landscapes - spatial pattern, uncertainty, and scaling

    NASA Astrophysics Data System (ADS)

    Wu, X. B.; Liu, F.; Bai, E.; Boutton, T. W.; Archer, S.

    2008-12-01

    Woody plant invasion into grasslands and savannas has significant impacts on soil organic carbon (SOC) storage and its spatial heterogeneity. However, our understanding of spatial heterogeneity and uncertainty of SOC and its relationship to spatial patterns of vegetation in savanna landscapes remains limited. This understanding is essential for effective assessment and monitoring of SOC storage, turnover, and vulnerability in savanna landscapes. In this study, we investigated the spatial pattern of SOC and its relationship to that of vegetation patterns in a subtropical savanna in south Texas using spatially-explicit intensive sampling and spatial statistical analysis. We found that the spatial distribution of SOC was closely related to the spatial distribution of woody vegetation, and that there were strong within-patch patterns related to past dynamics of the woody vegetation. Results of conditional stochastic simulations showed significantly greater levels of uncertainty of SOC estimations in larger woody patches than in smaller woody patches and grassland, likely caused by complex canopy structure, root distribution and animal disturbance. Assessment of alternative sampling designs demonstrated the effect of spatial uncertainty on estimation accuracy of SOC storage, and helped generate effective sampling strategies to improve SOC estimation accuracy. This understanding of spatial uncertainty of SOC enabled improved approaches to estimate and monitor soil carbon storage over large landscapes based on remote sensing.

  7. Disentangling how landscape spatial and temporal heterogeneity affects Savanna birds.

    PubMed

    Price, Bronwyn; McAlpine, Clive A; Kutt, Alex S; Ward, Doug; Phinn, Stuart R; Ludwig, John A

    2013-01-01

    In highly seasonal tropical environments, temporal changes in habitat and resources are a significant determinant of the spatial distribution of species. This study disentangles the effects of spatial and mid to long-term temporal heterogeneity in habitat on the diversity and abundance of savanna birds by testing four competing conceptual models of varying complexity. Focussing on sites in northeast Australia over a 20 year time period, we used ground cover and foliage projected cover surfaces derived from a time series of Landsat Thematic Mapper imagery, rainfall data and site-level vegetation surveys to derive measures of habitat structure at local (1-100 ha) and landscape (100-1000s ha) scales. We used generalised linear models and an information theoretic approach to test the independent effects of spatial and temporal influences on savanna bird diversity and the abundance of eight species with different life-history behaviours. Of four competing models defining influences on assemblages of savanna birds, the most parsimonious included temporal and spatial variability in vegetation cover and site-scale vegetation structure, suggesting savanna bird species respond to spatial and temporal habitat heterogeneity at both the broader landscape scale and at the fine-scale. The relative weight, strength and direction of the explanatory variables changed with each of the eight species, reflecting their different ecology and behavioural traits. This study demonstrates that variations in the spatial pattern of savanna vegetation over periods of 10 to 20 years at the local and landscape scale strongly affect bird diversity and abundance. Thus, it is essential to monitor and manage both spatial and temporal variability in avian habitat to achieve long-term biodiversity outcomes.

  8. Disentangling How Landscape Spatial and Temporal Heterogeneity Affects Savanna Birds

    PubMed Central

    Price, Bronwyn; McAlpine, Clive A.; Kutt, Alex S.; Ward, Doug; Phinn, Stuart R.; Ludwig, John A.

    2013-01-01

    In highly seasonal tropical environments, temporal changes in habitat and resources are a significant determinant of the spatial distribution of species. This study disentangles the effects of spatial and mid to long-term temporal heterogeneity in habitat on the diversity and abundance of savanna birds by testing four competing conceptual models of varying complexity. Focussing on sites in northeast Australia over a 20 year time period, we used ground cover and foliage projected cover surfaces derived from a time series of Landsat Thematic Mapper imagery, rainfall data and site-level vegetation surveys to derive measures of habitat structure at local (1–100 ha) and landscape (100–1000s ha) scales. We used generalised linear models and an information theoretic approach to test the independent effects of spatial and temporal influences on savanna bird diversity and the abundance of eight species with different life-history behaviours. Of four competing models defining influences on assemblages of savanna birds, the most parsimonious included temporal and spatial variability in vegetation cover and site-scale vegetation structure, suggesting savanna bird species respond to spatial and temporal habitat heterogeneity at both the broader landscape scale and at the fine-scale. The relative weight, strength and direction of the explanatory variables changed with each of the eight species, reflecting their different ecology and behavioural traits. This study demonstrates that variations in the spatial pattern of savanna vegetation over periods of 10 to 20 years at the local and landscape scale strongly affect bird diversity and abundance. Thus, it is essential to monitor and manage both spatial and temporal variability in avian habitat to achieve long-term biodiversity outcomes. PMID:24066138

  9. Climate and the landscape of fear in an African savanna.

    PubMed

    Riginos, Corinna

    2015-01-01

    Herbivores frequently have to make trade-offs between two basic needs: the need to acquire forage and the need to avoid predation. One manifestation of this trade-off is the 'landscape of fear' phenomenon - wherein herbivores avoid areas of high perceived predation risk even if forage is abundant or of high quality in those areas. Although this phenomenon is well established among invertebrates, its applicability to terrestrial large herbivores remains debated, in part because experimental evidence is scarce. This study was designed to (i) experimentally test the effects of tree density - a key landscape feature associated with predation risk for African ungulates - on herbivore habitat use and (ii) establish whether habitat use patterns could be explained by trade-offs between foraging opportunities and predation risk avoidance. In a Kenyan savanna system, replicate plots dominated by the tree Acacia drepanolobium were cleared, thinned or left intact. Ungulate responses were measured over four years, which included years of moderate rainfall as well as a severe drought. Under average rainfall conditions, most herbivores (primarily plains zebra, Grant's gazelle and hartebeest) favoured sites with fewer trees and higher visibility - regardless of grass production - while elephants (too large to be vulnerable to predation) favoured sites with many trees. During the drought, however, herbivores favoured sites that had high grass biomass, but not high visibility. Thus, during the drought, herbivores sought areas where food was more abundant, despite probable higher risk of predation. These results illustrate that the 'landscape of fear', and the associated interactions between top-down and bottom-up effects, is not static, but rather shifts markedly under different conditions. Climate thus has the potential to alter the strength and spatial dynamics of behaviourally mediated cascades in large herbivore systems.

  10. Climate and the landscape of fear in an African savanna.

    PubMed

    Riginos, Corinna

    2015-01-01

    Herbivores frequently have to make trade-offs between two basic needs: the need to acquire forage and the need to avoid predation. One manifestation of this trade-off is the 'landscape of fear' phenomenon - wherein herbivores avoid areas of high perceived predation risk even if forage is abundant or of high quality in those areas. Although this phenomenon is well established among invertebrates, its applicability to terrestrial large herbivores remains debated, in part because experimental evidence is scarce. This study was designed to (i) experimentally test the effects of tree density - a key landscape feature associated with predation risk for African ungulates - on herbivore habitat use and (ii) establish whether habitat use patterns could be explained by trade-offs between foraging opportunities and predation risk avoidance. In a Kenyan savanna system, replicate plots dominated by the tree Acacia drepanolobium were cleared, thinned or left intact. Ungulate responses were measured over four years, which included years of moderate rainfall as well as a severe drought. Under average rainfall conditions, most herbivores (primarily plains zebra, Grant's gazelle and hartebeest) favoured sites with fewer trees and higher visibility - regardless of grass production - while elephants (too large to be vulnerable to predation) favoured sites with many trees. During the drought, however, herbivores favoured sites that had high grass biomass, but not high visibility. Thus, during the drought, herbivores sought areas where food was more abundant, despite probable higher risk of predation. These results illustrate that the 'landscape of fear', and the associated interactions between top-down and bottom-up effects, is not static, but rather shifts markedly under different conditions. Climate thus has the potential to alter the strength and spatial dynamics of behaviourally mediated cascades in large herbivore systems. PMID:24942250

  11. Opposing resonses to ecological gradients structure amphibian and reptile communities across a temperate grassland-savanna-forest landscape

    USGS Publications Warehouse

    Grundel, Ralph; Beamer, David; Glowacki, Gary A.; Frohnapple, Krystal; Pavlovic, Noel B.

    2014-01-01

    Temperate savannas are threatened across the globe. If we prioritize savanna restoration, we should ask how savanna animal communities differ from communities in related open habitats and forests. We documented distribution of amphibian and reptile species across an open-savanna–forest gradient in the Midwest U.S. to determine how fire history and habitat structure affected herpetofaunal community composition. The transition from open habitats to forests was a transition from higher reptile abundance to higher amphibian abundance and the intermediate savanna landscape supported the most species overall. These differences warn against assuming that amphibian and reptile communities will have similar ecological responses to habitat structure. Richness and abundance also often responded in opposite directions to some habitat characteristics, such as cover of bare ground or litter. Herpetofaunal community species composition changed along a fire gradient from infrequent and recent fires to frequent but less recent fires. Nearby (200-m) wetland cover was relatively unimportant in predicting overall herpetofaunal community composition while fire history and fire-related canopy and ground cover were more important predictors of composition, diversity, and abundance. Increased developed cover was negatively related to richness and abundance. This indicates the importance of fire history and fire related landscape characteristics, and the negative effects of development, in shaping the upland herpetofaunal community along the native grassland–forest continuum.

  12. Using conservation value to assess land restoration and management alternatives across a degraded oak savanna landscape

    USGS Publications Warehouse

    Grundel, R.; Pavlovic, N.B.

    2008-01-01

    1. Managers considering restoration of landscapes often face a fundamental challenge - what should be the habitat composition of the restored landscape? We present a method for evaluating an important conservation trade-off inherent in making that decision. 2. Oak savannas and grasslands were historically widespread across central North America but are now rare. Today, in north-west Indiana, USA, habitats spanning a range of woody vegetation density, from nearly treeless open habitats to forests, occur across the conserved landscape where savannas probably once dominated. To understand the benefits of different potential landscape compositions, we evaluated how different proportions of five habitats - open, savanna, woodland, scrub and forest - might affect the conservation value of the north-west Indiana landscape for birds. Two variables of potential conservation importance were examined: species diversity, a measure of avian community richness, and conservation index, the percentage of a bird species' global population occurring on a hectare of landscape, summed across all bird species present. Higher values of conservation index were associated with higher local densities of globally more rare and more threatened species. 3. Conservation index and species diversity were correlated negatively across hypothetical landscapes composed of different proportions of the five habitats. Therefore, a management trade-off existed between conservation index and species diversity because landscapes that maximized species diversity differed from landscapes that maximized conservation index. 4. A landscape of 50% open, 22% savanna, 15% scrub and 13% forest was predicted to represent a compromise at which conservation index and species diversity reached the same percentage of their maxima. In contrast, the current landscape is dominated by forest. 5. Synthesis and applications. We quantified the trade-off between two potential aspects of a landscape's conservation value for

  13. Local versus landscape-scale effects of savanna trees on grasses

    USGS Publications Warehouse

    Riginos, C.; Grace, J.B.; Augustine, D.J.; Young, T.P.

    2009-01-01

    1. Savanna ecosystems - defined by the coexistence of trees and grasses - cover more than one-fifth the world's land surface and harbour most of the world's rangelands, livestock and large mammal diversity. Savanna trees can have a variety of effects on grasses, with consequences for the wild and domestic herbivores that depend on them. 2.Studies of these effects have focused on two different spatial scales. At the scale of individual trees, many studies have shown net positive effects of trees on sub-canopy grass nutrient concentrations and biomass. At the landscape scale, other studies have shown negative effects of high tree densities on grass productivity. These disparate results have led to different conclusions about the effects of trees on forage quality and ungulate nutrition in savannas. 3.We integrate these approaches by examining the effects of trees on grasses at both spatial scales and across a range of landscape-scale tree densities. 4.We quantified grass biomass, species composition and nutrient concentrations in these different contexts in an Acacia drepanolobium savanna in Laikipia, Kenya. Individual trees had positive effects on grass biomass, most likely because trees enrich soil nitrogen. Grass leaf phosphorus in sub-canopy areas, however, was depressed. The effects of individual trees could explain the effects of increasing landscape-scale tree cover for the biomass of only two of the four dominant grass species. 5.The negative effects of trees on grass and soil phosphorus, combined with depressed grass productivity in areas of high tree cover, suggest that ungulate nutrition may be compromised in areas with many trees. 6.Synthesis. We conclude that few, isolated trees may have positive local effects on savanna grasses and forage, but in areas of high tree density the negative landscape-scale effects of trees are likely to outweigh these positive effects. In savannas and other patchy landscapes, attempts to predict the consequences of changes

  14. Landscape-scale effects of herbivores on treefall in African savannas.

    PubMed

    Asner, Gregory P; Levick, Shaun R

    2012-11-01

    Herbivores cause treefalls in African savannas, but rates are unknown at large scales required to forecast changes in biodiversity and ecosystem processes. We combined landscape-scale herbivore exclosures with repeat airborne Light Detection and Ranging of 58 429 trees in Kruger National Park, South Africa, to assess sources of savanna treefall across nested gradients of climate, topography, and soil fertility. Elephants were revealed as the primary agent of treefall across widely varying savanna conditions, and a large-scale 'elephant trap' predominantly removes maturing savanna trees in the 5-9 m height range. Treefall rates averaged 6 times higher in areas accessible to elephants, but proportionally more treefall occurred on high-nutrient basalts and in lowland catena areas. These patterns were superimposed on a climate-mediated regime of increasing treefall with precipitation in the absence of herbivores. These landscape-scale patterns reveal environmental controls underpinning herbivore-mediated tree turnover, highlighting the need for context-dependent science and management.

  15. Defensive plant-ants stabilize megaherbivore-driven landscape change in an African savanna.

    PubMed

    Goheen, Jacob R; Palmer, Todd M

    2010-10-12

    Tree cover in savanna ecosystems is usually regarded as unstable, varying with rainfall, fire, and herbivory. In sub-Saharan Africa, elephants (Loxodonta africana) suppress tree cover, thereby maintaining landscape heterogeneity by promoting tree-grass coexistence. In the absence of elephants, tree encroachment may convert savannas into closed-canopy woodlands; when elephants increase in abundance, intensified browsing pressure can transform savannas into open grasslands. We show that symbiotic ants stabilize tree cover across landscapes in Kenya by protecting a dominant tree from elephants. In feeding trials, elephants avoided plants with ants and did not distinguish between a myrmecophyte (the whistling-thorn tree [Acacia drepanolobium]) from which ants had been removed and a highly palatable, nonmyrmecophytic congener. In field experiments, elephants inflicted severe damage on whistling-thorn trees from which ants had been removed. Across two properties on which elephants increased between 2003 and 2008, cover of whistling-thorn did not change significantly inside versus outside large-scale elephant exclusion fences; over the same period of time, cover of nonmyrmecophytes differed profoundly inside versus outside exclusion fences. These results highlight the powerful role that symbioses and plant defense play in driving tree growth and survival in savannas, ecosystems of global economic and ecological importance.

  16. Seasonality of fire weather strongly influences fire regimes in South Florida savanna-grassland landscapes.

    PubMed

    Platt, William J; Orzell, Steve L; Slocum, Matthew G

    2015-01-01

    Fire seasonality, an important characteristic of fire regimes, commonly is delineated using seasons based on single weather variables (rainfall or temperature). We used nonparametric cluster analyses of a 17-year (1993-2009) data set of weather variables that influence likelihoods and spread of fires (relative humidity, air temperature, solar radiation, wind speed, soil moisture) to explore seasonality of fire in pine savanna-grassland landscapes at the Avon Park Air Force Range in southern Florida. A four-variable, three-season model explained more variation within fire weather variables than models with more seasons. The three-season model also delineated intra-annual timing of fire more accurately than a conventional rainfall-based two-season model. Two seasons coincided roughly with dry and wet seasons based on rainfall. The third season, which we labeled the fire season, occurred between dry and wet seasons and was characterized by fire-promoting conditions present annually: drought, intense solar radiation, low humidity, and warm air temperatures. Fine fuels consisting of variable combinations of pyrogenic pine needles, abundant C4 grasses, and flammable shrubs, coupled with low soil moisture, and lightning ignitions early in the fire season facilitate natural landscape-scale wildfires that burn uplands and across wetlands. We related our three season model to fires with different ignition sources (lightning, military missions, and prescribed fires) over a 13-year period with fire records (1997-2009). Largest wildfires originate from lightning and military ignitions that occur within the early fire season substantially prior to the peak of lightning strikes in the wet season. Prescribed ignitions, in contrast, largely occur outside the fire season. Our delineation of a pronounced fire season provides insight into the extent to which different human-derived fire regimes mimic lightning fire regimes. Delineation of a fire season associated with timing of

  17. Seasonality of fire weather strongly influences fire regimes in South Florida savanna-grassland landscapes.

    PubMed

    Platt, William J; Orzell, Steve L; Slocum, Matthew G

    2015-01-01

    Fire seasonality, an important characteristic of fire regimes, commonly is delineated using seasons based on single weather variables (rainfall or temperature). We used nonparametric cluster analyses of a 17-year (1993-2009) data set of weather variables that influence likelihoods and spread of fires (relative humidity, air temperature, solar radiation, wind speed, soil moisture) to explore seasonality of fire in pine savanna-grassland landscapes at the Avon Park Air Force Range in southern Florida. A four-variable, three-season model explained more variation within fire weather variables than models with more seasons. The three-season model also delineated intra-annual timing of fire more accurately than a conventional rainfall-based two-season model. Two seasons coincided roughly with dry and wet seasons based on rainfall. The third season, which we labeled the fire season, occurred between dry and wet seasons and was characterized by fire-promoting conditions present annually: drought, intense solar radiation, low humidity, and warm air temperatures. Fine fuels consisting of variable combinations of pyrogenic pine needles, abundant C4 grasses, and flammable shrubs, coupled with low soil moisture, and lightning ignitions early in the fire season facilitate natural landscape-scale wildfires that burn uplands and across wetlands. We related our three season model to fires with different ignition sources (lightning, military missions, and prescribed fires) over a 13-year period with fire records (1997-2009). Largest wildfires originate from lightning and military ignitions that occur within the early fire season substantially prior to the peak of lightning strikes in the wet season. Prescribed ignitions, in contrast, largely occur outside the fire season. Our delineation of a pronounced fire season provides insight into the extent to which different human-derived fire regimes mimic lightning fire regimes. Delineation of a fire season associated with timing of

  18. Seasonality of Fire Weather Strongly Influences Fire Regimes in South Florida Savanna-Grassland Landscapes

    PubMed Central

    Platt, William J.; Orzell, Steve L.; Slocum, Matthew G.

    2015-01-01

    Fire seasonality, an important characteristic of fire regimes, commonly is delineated using seasons based on single weather variables (rainfall or temperature). We used nonparametric cluster analyses of a 17-year (1993–2009) data set of weather variables that influence likelihoods and spread of fires (relative humidity, air temperature, solar radiation, wind speed, soil moisture) to explore seasonality of fire in pine savanna-grassland landscapes at the Avon Park Air Force Range in southern Florida. A four-variable, three-season model explained more variation within fire weather variables than models with more seasons. The three-season model also delineated intra-annual timing of fire more accurately than a conventional rainfall-based two-season model. Two seasons coincided roughly with dry and wet seasons based on rainfall. The third season, which we labeled the fire season, occurred between dry and wet seasons and was characterized by fire-promoting conditions present annually: drought, intense solar radiation, low humidity, and warm air temperatures. Fine fuels consisting of variable combinations of pyrogenic pine needles, abundant C4 grasses, and flammable shrubs, coupled with low soil moisture, and lightning ignitions early in the fire season facilitate natural landscape-scale wildfires that burn uplands and across wetlands. We related our three season model to fires with different ignition sources (lightning, military missions, and prescribed fires) over a 13-year period with fire records (1997–2009). Largest wildfires originate from lightning and military ignitions that occur within the early fire season substantially prior to the peak of lightning strikes in the wet season. Prescribed ignitions, in contrast, largely occur outside the fire season. Our delineation of a pronounced fire season provides insight into the extent to which different human-derived fire regimes mimic lightning fire regimes. Delineation of a fire season associated with timing of

  19. Comparison of the driving forces of spring phenology among savanna landscapes by including combined spatial and temporal heterogeneity.

    PubMed

    Zhu, Likai; Southworth, Jane; Meng, Jijun

    2015-10-01

    Understanding spatial and temporal dynamics of land surface phenology (LSP) and its driving forces are critical for providing information relevant to short- and long-term decision making, particularly as it relates to climate response planning. With the third generation Global Inventory Monitoring and Modeling System (GIMMS3g) Normalized Difference Vegetation Index (NDVI) data and environmental data from multiple sources, we investigated the spatio-temporal changes in the start of the growing season (SOS) in southern African savannas from 1982 through 2010 and determined its linkage to environmental factors using spatial panel data models. Overall, the SOS occurs earlier in the north compared to the south. This relates in part to the differences in ecosystems, with northern areas representing high rainfall and dense tree cover (mainly tree savannas), whereas the south has lower rainfall and sparse tree cover (mainly bush and grass savannas). From 1982 to 2010, an advanced trend was observed predominantly in the tree savanna areas of the north, whereas a delayed trend was chiefly found in the floodplain of the north and bush/grass savannas of the south. Different environmental drivers were detected within tree- and grass-dominated savannas, with a critical division being represented by the 800 mm isohyet. Our results supported the importance of water as a driver in this water-limited system, specifically preseason soil moisture, in determining the SOS in these water-limited, grass-dominated savannas. In addition, the research pointed to other, often overlooked, effects of preseason maximum and minimum temperatures on the SOS across the entire region. Higher preseason maximum temperatures led to an advance of the SOS, whereas the opposite effects of preseason minimum temperature were observed. With the rapid increase in global change research, this work will prove helpful for managing savanna landscapes and key to predicting how projected climate changes will affect

  20. Comparison of the driving forces of spring phenology among savanna landscapes by including combined spatial and temporal heterogeneity

    NASA Astrophysics Data System (ADS)

    Zhu, Likai; Southworth, Jane; Meng, Jijun

    2015-10-01

    Understanding spatial and temporal dynamics of land surface phenology (LSP) and its driving forces are critical for providing information relevant to short- and long-term decision making, particularly as it relates to climate response planning. With the third generation Global Inventory Monitoring and Modeling System (GIMMS3g) Normalized Difference Vegetation Index (NDVI) data and environmental data from multiple sources, we investigated the spatio-temporal changes in the start of the growing season (SOS) in southern African savannas from 1982 through 2010 and determined its linkage to environmental factors using spatial panel data models. Overall, the SOS occurs earlier in the north compared to the south. This relates in part to the differences in ecosystems, with northern areas representing high rainfall and dense tree cover (mainly tree savannas), whereas the south has lower rainfall and sparse tree cover (mainly bush and grass savannas). From 1982 to 2010, an advanced trend was observed predominantly in the tree savanna areas of the north, whereas a delayed trend was chiefly found in the floodplain of the north and bush/grass savannas of the south. Different environmental drivers were detected within tree- and grass-dominated savannas, with a critical division being represented by the 800 mm isohyet. Our results supported the importance of water as a driver in this water-limited system, specifically preseason soil moisture, in determining the SOS in these water-limited, grass-dominated savannas. In addition, the research pointed to other, often overlooked, effects of preseason maximum and minimum temperatures on the SOS across the entire region. Higher preseason maximum temperatures led to an advance of the SOS, whereas the opposite effects of preseason minimum temperature were observed. With the rapid increase in global change research, this work will prove helpful for managing savanna landscapes and key to predicting how projected climate changes will affect

  1. Monitoring contrasting land management in the savanna landscapes of northern Australia.

    PubMed

    Franklin, Donald C; Petty, Aaron M; Williamson, Grant J; Brook, Barry W; Bowman, David M J S

    2008-04-01

    We compared measures of ecosystem state across six adjacent land-tenure groups in the intact tropical savanna landscapes of northern Australia. Tenure groups include two managed by Aboriginal owners, two national parks, a cluster of pastoral leases, and a military training area. This information is of relevance to the debate about the role of indigenous lands in the Australian conservation estate. The timing and frequency of fire was determined by satellite imagery; the biomass and composition of the herb-layer and the abundance of large feral herbivores by field surveys; and weediness by analysis of a Herbarium database. European tenures varied greatly in fire frequencies but were consistently burnt earlier in the dry season than the two Aboriginal tenures, the latter having intermediate fire frequencies. Weeds were more frequent in the European tenures, whilst feral animals were most abundant in the Aboriginal tenures. This variation strongly implies a signature of current management and/or recent environmental history. We identify indices suitable for monitoring of management outcomes in an extensive and sparsely populated landscape. Aboriginal land offers a unique opportunity for the conservation of biodiversity through the maintenance of traditional fire regimes. However, without financial support, traditional practices may prove unsustainable both economically and because exotic weeds and feral animals will alter fire regimes. An additional return on investment in Aboriginal land management is likely to be improved livelihoods and health outcomes for these disadvantaged communities.

  2. Monitoring Contrasting Land Management in the Savanna Landscapes of Northern Australia

    NASA Astrophysics Data System (ADS)

    Franklin, Donald C.; Petty, Aaron M.; Williamson, Grant J.; Brook, Barry W.; Bowman, David M. J. S.

    2008-04-01

    We compared measures of ecosystem state across six adjacent land-tenure groups in the intact tropical savanna landscapes of northern Australia. Tenure groups include two managed by Aboriginal owners, two national parks, a cluster of pastoral leases, and a military training area. This information is of relevance to the debate about the role of indigenous lands in the Australian conservation estate. The timing and frequency of fire was determined by satellite imagery; the biomass and composition of the herb-layer and the abundance of large feral herbivores by field surveys; and weediness by analysis of a Herbarium database. European tenures varied greatly in fire frequencies but were consistently burnt earlier in the dry season than the two Aboriginal tenures, the latter having intermediate fire frequencies. Weeds were more frequent in the European tenures, whilst feral animals were most abundant in the Aboriginal tenures. This variation strongly implies a signature of current management and/or recent environmental history. We identify indices suitable for monitoring of management outcomes in an extensive and sparsely populated landscape. Aboriginal land offers a unique opportunity for the conservation of biodiversity through the maintenance of traditional fire regimes. However, without financial support, traditional practices may prove unsustainable both economically and because exotic weeds and feral animals will alter fire regimes. An additional return on investment in Aboriginal land management is likely to be improved livelihoods and health outcomes for these disadvantaged communities.

  3. A Multi-scale Spatial Analysis of Native and Exotic Plant Species Richness Within a Mixed-Disturbance Oak Savanna Landscape

    NASA Astrophysics Data System (ADS)

    Schetter, Timothy A.; Walters, Timothy L.; Root, Karen V.

    2013-09-01

    Impacts of human land use pose an increasing threat to global biodiversity. Resource managers must respond rapidly to this threat by assessing existing natural areas and prioritizing conservation actions across multiple spatial scales. Plant species richness is a useful measure of biodiversity but typically can only be evaluated on small portions of a given landscape. Modeling relationships between spatial heterogeneity and species richness may allow conservation planners to make predictions of species richness patterns within unsampled areas. We utilized a combination of field data, remotely sensed data, and landscape pattern metrics to develop models of native and exotic plant species richness at two spatial extents (60- and 120-m windows) and at four ecological levels for northwestern Ohio's Oak Openings region. Multiple regression models explained 37-77 % of the variation in plant species richness. These models consistently explained more variation in exotic richness than in native richness. Exotic richness was better explained at the 120-m extent while native richness was better explained at the 60-m extent. Land cover composition of the surrounding landscape was an important component of all models. We found that percentage of human-modified land cover (negatively correlated with native richness and positively correlated with exotic richness) was a particularly useful predictor of plant species richness and that human-caused disturbances exert a strong influence on species richness patterns within a mixed-disturbance oak savanna landscape. Our results emphasize the importance of using a multi-scale approach to examine the complex relationships between spatial heterogeneity and plant species richness.

  4. Spatial Patterns of Plant δ13C and δ15N Along a Topoedaphic Gradient in a Subtropical Savanna Landscape

    NASA Astrophysics Data System (ADS)

    Bai, E.; Boutton, T. W.; Liu, F.; Wu, B.; Archer, S. R.

    2005-12-01

    δ13C and δ15N values of plants are powerful tools in physiological ecology, ecosystem science, and global biogeochemistry, yet we know relatively little about their variation and controls at the landscape scale. In this study, we investigated landscape-scale spatial variations in the foliar isotopic composition of 3 woody plant species across a 308 m topoedaphic gradient, along which soil texture and plant resources (water and nitrogen availability) varied from upland (86 m) to lowland (84 m) portions of the landscape. The study was conducted in a subtropical savanna at the La Copita Research Area, approximately 60 km west of Corpus Christi, TX. Foliar δ13C, δ15N, leaf nitrogen concentration ([N]), and specific leaf area (SLA) were measured on all individuals of Prosopis glandulosa, Condalia hookeri, and Zanthoxylum fagara present within a belt transect 308 m long x 12 m wide. Soil texture, available soil moisture, and total N were measured at 1 m intervals along the center-line of the belt transect. Clay content, available soil moisture, and soil total N were all negatively correlated with elevation along the transect. Leaf δ13C and δ15N values for all 3 species increased by 1-4 o/oo with decreasing elevation along the transect. Contrary to theory and previous studies, δ13C values were highest where soil water was most available, suggesting that some other variable could be overriding or interacting with water availability. Foliar [N] appeared to exert the strongest control over landscape-level variation, and was positively correlated with δ13C of all species (R 2 = 0.58, p<0.0001). Since leaf [N] is positively related to photosynthetic capacity, plants with high [N] are likely to have low Ci/Ca ratios and therefore higher δ13C values. δ15N values of Zanthoxylum and Condalia were positively correlated with leaf [N] and soil water availability; however, these relationships were absent for Prosopis, an N-fixing tree legume. We speculate that the

  5. Burning, fire prevention and landscape productions among the Pemon, Gran Sabana, Venezuela: toward an intercultural approach to wildland fire management in Neotropical Savannas.

    PubMed

    Sletto, Bjørn; Rodriguez, Iokiñe

    2013-01-30

    Wildland fire management in savanna landscapes increasingly incorporates indigenous knowledge to pursue strategies of controlled, prescriptive burning to control fuel loads. However, such participatory approaches are fraught with challenges because of contrasting views on the role of fire and the practices of prescribed burning between indigenous and state fire managers. Also, indigenous and state systems of knowledge and meanings associated with fire are not monolithic but instead characterized by conflicts and inconsistencies, which require new, communicative strategies in order to develop successful, intercultural approaches to fire management. This paper is based on long-term research on indigenous Pemon social constructs, rules and regulations regarding fire use, and traditional system of prescribed burning in the Gran Sabana, Venezuela. The authors review factors that act as constraints against successful intercultural fire management in the Gran Sabana, including conflicting perspectives on fire use within state agencies and in indigenous communities, and propose strategies for research and communicative planning to guide future efforts for more participatory and effective fire management. PMID:23246908

  6. Burning, fire prevention and landscape productions among the Pemon, Gran Sabana, Venezuela: toward an intercultural approach to wildland fire management in Neotropical Savannas.

    PubMed

    Sletto, Bjørn; Rodriguez, Iokiñe

    2013-01-30

    Wildland fire management in savanna landscapes increasingly incorporates indigenous knowledge to pursue strategies of controlled, prescriptive burning to control fuel loads. However, such participatory approaches are fraught with challenges because of contrasting views on the role of fire and the practices of prescribed burning between indigenous and state fire managers. Also, indigenous and state systems of knowledge and meanings associated with fire are not monolithic but instead characterized by conflicts and inconsistencies, which require new, communicative strategies in order to develop successful, intercultural approaches to fire management. This paper is based on long-term research on indigenous Pemon social constructs, rules and regulations regarding fire use, and traditional system of prescribed burning in the Gran Sabana, Venezuela. The authors review factors that act as constraints against successful intercultural fire management in the Gran Sabana, including conflicting perspectives on fire use within state agencies and in indigenous communities, and propose strategies for research and communicative planning to guide future efforts for more participatory and effective fire management.

  7. 23 CFR 752.4 - Landscape development.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 23 Highways 1 2011-04-01 2011-04-01 false Landscape development. 752.4 Section 752.4 Highways FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RIGHT-OF-WAY AND ENVIRONMENT LANDSCAPE AND ROADSIDE DEVELOPMENT § 752.4 Landscape development. (a) Landscape development, which includes...

  8. 23 CFR 752.4 - Landscape development.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 23 Highways 1 2013-04-01 2013-04-01 false Landscape development. 752.4 Section 752.4 Highways FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RIGHT-OF-WAY AND ENVIRONMENT LANDSCAPE AND ROADSIDE DEVELOPMENT § 752.4 Landscape development. (a) Landscape development, which includes...

  9. 23 CFR 752.4 - Landscape development.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 23 Highways 1 2014-04-01 2014-04-01 false Landscape development. 752.4 Section 752.4 Highways FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RIGHT-OF-WAY AND ENVIRONMENT LANDSCAPE AND ROADSIDE DEVELOPMENT § 752.4 Landscape development. (a) Landscape development, which includes...

  10. 23 CFR 752.4 - Landscape development.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 23 Highways 1 2012-04-01 2012-04-01 false Landscape development. 752.4 Section 752.4 Highways FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RIGHT-OF-WAY AND ENVIRONMENT LANDSCAPE AND ROADSIDE DEVELOPMENT § 752.4 Landscape development. (a) Landscape development, which includes...

  11. [Landscape classification: research progress and development trend].

    PubMed

    Liang, Fa-Chao; Liu, Li-Ming

    2011-06-01

    Landscape classification is the basis of the researches on landscape structure, process, and function, and also, the prerequisite for landscape evaluation, planning, protection, and management, directly affecting the precision and practicability of landscape research. This paper reviewed the research progress on the landscape classification system, theory, and methodology, and summarized the key problems and deficiencies of current researches. Some major landscape classification systems, e. g. , LANMAP and MUFIC, were introduced and discussed. It was suggested that a qualitative and quantitative comprehensive classification based on the ideology of functional structure shape and on the integral consideration of landscape classification utility, landscape function, landscape structure, physiogeographical factors, and human disturbance intensity should be the major research directions in the future. The integration of mapping, 3S technology, quantitative mathematics modeling, computer artificial intelligence, and professional knowledge to enhance the precision of landscape classification would be the key issues and the development trend in the researches of landscape classification.

  12. Development of grasslands and savannas in East Africa during the Neogene

    NASA Astrophysics Data System (ADS)

    Serling, T. E.

    1992-03-01

    The development of savanna-type grasslands is a relatively recent phenomena in East Africa. The stable carbon isotopic composition of paleosol carbonates from fossil localities in East Africa show that C 4 vegetation was present by amout 8-9 Ma but made up only a relatively small proportion of the total biomass. Although the proportion of C 4 vegetation increased in the Pliocene and Pleistocene there is no evidence for the development of virtually pure C 4 grasslands, as is characterized by tropical grasslands today, until Middle Pleistocene times. This has important implications concerning the evolution of mammals in Africa, including hominids.

  13. Quantification of Canopy Structure and its Implication on Radiative Transfer, Carbon Dioxide and Energy Flux Densities in a Heterogeneous Oak-Grass Savanna Ecosystem at the Landscape Scale

    NASA Astrophysics Data System (ADS)

    Sonnentag, O.; Ryu, Y.; Vargas, R.; Baldocchi, D.

    2008-12-01

    Oak-grass savanna ecosystems are characterized by pronounced heterogeneity in canopy structure at the landscape scale. Due to this heterogeneity the accurate quantification of canopy structure still remains a major challenge. The objectives of this study are to quantify clumping index, leaf area index (LAI) and the leaf inclination angle distribution function (LIADF) to describe the canopy structure of an oak-grass savanna ecosystem in California, USA. This information is critical for utilizing a radiative transfer model to compute CO2 and energy flux densities. We used four established techniques (LAI-2000 Plant Canopy Analyzer, digital hemispherical photography, the Tracing Radiation and Architecture of Canopies (TRAC) instrument, and a robotics railroad radiometer) to measure clumping index and LAI within a 300 x 300 m plot centered at an eddy covariance (EC) tower. Leaf inclination angle distributions were assessed from digital photographs at multiple height intervals through analysis with a public domain image processing software. Preliminary analysis of the data showed that mean values for clumping index and LAI obtained from the various instruments are in good agreement, thus reducing the uncertainty inherent in the measurements. Our leaf angle measurements revealed the canopy to be predominantly erectophile at all height intervals, an ecological consequence of the fact that oak leaves must be erect to reduce thermal load.

  14. A Landscape-Scale, Applied Fire Management Experiment Promotes Recovery of a Population of the Threatened Gouldian Finch, Erythrura gouldiae, in Australia's Tropical Savannas.

    PubMed

    Legge, Sarah; Garnett, Stephen; Maute, Kim; Heathcote, Joanne; Murphy, Steve; Woinarski, John C Z; Astheimer, Lee

    2015-01-01

    Fire is an integral part of savanna ecology and changes in fire patterns are linked to biodiversity loss in savannas worldwide. In Australia, changed fire regimes are implicated in the contemporary declines of small mammals, riparian species, obligate-seeding plants and grass seed-eating birds. Translating this knowledge into management to recover threatened species has proved elusive. We report here on a landscape-scale experiment carried out by the Australian Wildlife Conservancy (AWC) on Mornington Wildlife Sanctuary in northwest Australia. The experiment was designed to understand the response of a key savanna bird guild to fire, and to use that information to manage fire with the aim of recovering a threatened species population. We compared condition indices among three seed-eating bird species--one endangered (Gouldian finch) and two non-threatened (long-tailed finch and double-barred finch)--from two large areas (> 2,830 km2) with initial contrasting fire regimes ('extreme': frequent, extensive, intense fire; versus 'benign': less frequent, smaller, lower intensity fires). Populations of all three species living with the extreme fire regime had condition indices that differed from their counterparts living with the benign fire regime, including higher haematocrit levels in some seasons (suggesting higher levels of activity required to find food), different seasonal haematocrit profiles, higher fat scores in the early wet season (suggesting greater food uncertainty), and then lower muscle scores later in the wet season (suggesting prolonged food deprivation). Gouldian finches also showed seasonally increasing stress hormone concentrations with the extreme fire regime. Cumulatively, these patterns indicated greater nutritional stress over many months for seed-eating birds exposed to extreme fire regimes. We tested these relationships by monitoring finch condition over the following years, as AWC implemented fire management to produce the 'benign' fire regime

  15. A Landscape-Scale, Applied Fire Management Experiment Promotes Recovery of a Population of the Threatened Gouldian Finch, Erythrura gouldiae, in Australia's Tropical Savannas.

    PubMed

    Legge, Sarah; Garnett, Stephen; Maute, Kim; Heathcote, Joanne; Murphy, Steve; Woinarski, John C Z; Astheimer, Lee

    2015-01-01

    Fire is an integral part of savanna ecology and changes in fire patterns are linked to biodiversity loss in savannas worldwide. In Australia, changed fire regimes are implicated in the contemporary declines of small mammals, riparian species, obligate-seeding plants and grass seed-eating birds. Translating this knowledge into management to recover threatened species has proved elusive. We report here on a landscape-scale experiment carried out by the Australian Wildlife Conservancy (AWC) on Mornington Wildlife Sanctuary in northwest Australia. The experiment was designed to understand the response of a key savanna bird guild to fire, and to use that information to manage fire with the aim of recovering a threatened species population. We compared condition indices among three seed-eating bird species--one endangered (Gouldian finch) and two non-threatened (long-tailed finch and double-barred finch)--from two large areas (> 2,830 km2) with initial contrasting fire regimes ('extreme': frequent, extensive, intense fire; versus 'benign': less frequent, smaller, lower intensity fires). Populations of all three species living with the extreme fire regime had condition indices that differed from their counterparts living with the benign fire regime, including higher haematocrit levels in some seasons (suggesting higher levels of activity required to find food), different seasonal haematocrit profiles, higher fat scores in the early wet season (suggesting greater food uncertainty), and then lower muscle scores later in the wet season (suggesting prolonged food deprivation). Gouldian finches also showed seasonally increasing stress hormone concentrations with the extreme fire regime. Cumulatively, these patterns indicated greater nutritional stress over many months for seed-eating birds exposed to extreme fire regimes. We tested these relationships by monitoring finch condition over the following years, as AWC implemented fire management to produce the 'benign' fire regime

  16. A Landscape-Scale, Applied Fire Management Experiment Promotes Recovery of a Population of the Threatened Gouldian Finch, Erythrura gouldiae, in Australia’s Tropical Savannas

    PubMed Central

    Legge, Sarah; Garnett, Stephen; Maute, Kim; Heathcote, Joanne; Murphy, Steve; Woinarski, John C. Z.; Astheimer, Lee

    2015-01-01

    Fire is an integral part of savanna ecology and changes in fire patterns are linked to biodiversity loss in savannas worldwide. In Australia, changed fire regimes are implicated in the contemporary declines of small mammals, riparian species, obligate-seeding plants and grass seed-eating birds. Translating this knowledge into management to recover threatened species has proved elusive. We report here on a landscape-scale experiment carried out by the Australian Wildlife Conservancy (AWC) on Mornington Wildlife Sanctuary in northwest Australia. The experiment was designed to understand the response of a key savanna bird guild to fire, and to use that information to manage fire with the aim of recovering a threatened species population. We compared condition indices among three seed-eating bird species–one endangered (Gouldian finch) and two non-threatened (long-tailed finch and double-barred finch)—from two large areas (> 2,830 km2) with initial contrasting fire regimes (‘extreme’: frequent, extensive, intense fire; versus ‘benign’: less frequent, smaller, lower intensity fires). Populations of all three species living with the extreme fire regime had condition indices that differed from their counterparts living with the benign fire regime, including higher haematocrit levels in some seasons (suggesting higher levels of activity required to find food), different seasonal haematocrit profiles, higher fat scores in the early wet season (suggesting greater food uncertainty), and then lower muscle scores later in the wet season (suggesting prolonged food deprivation). Gouldian finches also showed seasonally increasing stress hormone concentrations with the extreme fire regime. Cumulatively, these patterns indicated greater nutritional stress over many months for seed-eating birds exposed to extreme fire regimes. We tested these relationships by monitoring finch condition over the following years, as AWC implemented fire management to produce the

  17. 23 CFR 752.4 - Landscape development.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... landscaping and environmental design. (b) Landscape development should have provisions for plant establishment periods of a duration sufficient for expected survival in the highway environment. Normal 1-year plant... for natural regeneration of native growth and the management of that growth. (e) Landscaping...

  18. Deciphering the distribution of the savanna biome.

    PubMed

    Lehmann, Caroline E R; Archibald, Sally A; Hoffmann, William A; Bond, William J

    2011-07-01

    • We aimed to identify the limits of savanna across Africa, Australia and South America. We based our investigation on the rich history of hypotheses previously examined: that the limits of savanna are variously determined by rainfall, rainfall seasonality, soil fertility and disturbance. • We categorized vegetation on all continents as 'savanna' (open habitats with a C(4) grass layer) or 'not-savanna' (closed habitats with no C(4) grass layer) and used a combination of statistical approaches to examine how the presence of savanna varied as a function of five environmental correlates. • The presence of savanna is constrained by effective rainfall and rainfall seasonality. Soil fertility is regionally important, although the direction of its effect changes relative to rainfall. We identified three continental divergences in the limits of savanna that could not be explained by environment. • Climate and soils do not have a deterministic effect on the distribution of savanna. Over the range of savanna, some proportion of the land is always 'not-savanna'. We reconciled previous contradictory views of savanna limits by developing a new conceptual framework for understanding these limits by categorizing environmental factors into whether they had a positive or negative effect on woody growth and the frequency of disturbance.

  19. Effects of fire on woody vegetation structure in African savanna.

    PubMed

    Smit, Izak P J; Asner, Gregory P; Govender, Navashni; Kennedy-Bowdoin, Ty; Knapp, David E; Jacobson, James

    2010-10-01

    Despite the importance of fire in shaping savannas, it remains poorly understood how the frequency, seasonality, and intensity of fire interact to influence woody vegetation structure, which is a key determinant of savanna biodiversity. We provide a comprehensive analysis of vertical and horizontal woody vegetation structure across one of the oldest savanna fire experiments, using new airborne Light Detection and Ranging (LiDAR) technology. We developed and compared high-resolution woody vegetation height surfaces for a series of large experimental burn plots in the Kruger National Park, South Africa. These 7-ha plots (total area approximately 1500 ha) have been subjected to fire in different seasons and at different frequencies, as well as no-burn areas, for 54 years. Long-term exposure to fire caused a reduction in woody vegetation up to the 5.0-7.5 m height class, although most reduction was observed up to 4 m. Average fire intensity was positively correlated with changes in woody vegetation structure. More frequent fires reduced woody vegetation cover more than less frequent fires, and dry-season fires reduced woody vegetation more than wet-season fires. Spring fires from the late dry season reduced woody vegetation cover the most, and summer fires from the wet season reduced it the least. Fire had a large effect on structure in the densely wooded granitic landscapes as compared to the more open basaltic landscapes, although proportionally, the woody vegetation was more reduced in the drier than in the wetter landscapes. We show that fire frequency and fire season influence patterns of vegetation three-dimensional structure, which may have cascading consequences for biodiversity. Managers of savannas can therefore use fire frequency and season in concert to achieve specific vegetation structural objectives.

  20. Effects of fire on woody vegetation structure in African savanna.

    PubMed

    Smit, Izak P J; Asner, Gregory P; Govender, Navashni; Kennedy-Bowdoin, Ty; Knapp, David E; Jacobson, James

    2010-10-01

    Despite the importance of fire in shaping savannas, it remains poorly understood how the frequency, seasonality, and intensity of fire interact to influence woody vegetation structure, which is a key determinant of savanna biodiversity. We provide a comprehensive analysis of vertical and horizontal woody vegetation structure across one of the oldest savanna fire experiments, using new airborne Light Detection and Ranging (LiDAR) technology. We developed and compared high-resolution woody vegetation height surfaces for a series of large experimental burn plots in the Kruger National Park, South Africa. These 7-ha plots (total area approximately 1500 ha) have been subjected to fire in different seasons and at different frequencies, as well as no-burn areas, for 54 years. Long-term exposure to fire caused a reduction in woody vegetation up to the 5.0-7.5 m height class, although most reduction was observed up to 4 m. Average fire intensity was positively correlated with changes in woody vegetation structure. More frequent fires reduced woody vegetation cover more than less frequent fires, and dry-season fires reduced woody vegetation more than wet-season fires. Spring fires from the late dry season reduced woody vegetation cover the most, and summer fires from the wet season reduced it the least. Fire had a large effect on structure in the densely wooded granitic landscapes as compared to the more open basaltic landscapes, although proportionally, the woody vegetation was more reduced in the drier than in the wetter landscapes. We show that fire frequency and fire season influence patterns of vegetation three-dimensional structure, which may have cascading consequences for biodiversity. Managers of savannas can therefore use fire frequency and season in concert to achieve specific vegetation structural objectives. PMID:21049875

  1. Developing Remote Sensing Methodology to Characterize Savanna Vegetation Structure and Composition for Rangeland Monitoring and Conservation Applications

    NASA Astrophysics Data System (ADS)

    Tsalyuk, M.; Kelly, M.; Getz, W.

    2012-12-01

    Rangeland ecosystems cover more than fifty percent of earth's land surface, host considerable biodiversity and provide vital ecosystem services. However, rangelands around the world face degradation due to climate change, land use change and overgrazing. Human-driven changes to fire and grazing regimes enhance degradation processes. The purpose of this research is to develop a remote sensing methodology to characterize the structure and composition of savanna vegetation, in order to improve the ability of conservation managers to monitor and address such degradation processes. Our study site, Etosha National Park, is a 22,270 km^2 semi-arid savanna located in north-central Namibia. Fencing and provision of artificial water sources for wildlife have changed the natural grazing patterns, which has caused bush encroachment and vegetation degradation across the park. We used MODIS and Landsat ETM+ 7 satellite imagery to map the vegetation type, dominant species, density, cover and biomass of herbaceous and woody vegetation in Etosha. We used imagery for 2007-2012 together with extensive field sampling, both in the wet and the dry seasons. At each sampling point, we identified the dominant species and measured the density, canopy size, height and diameter of the trees and shrubs. At only 31% of the sampling points, the identified vegetation type matched the class assigned at the 1996 classification. This may indicate significant habitat modifications in Etosha. We used two parallel analytical approaches to correlate between radiometric and field data. First, we show that traditional supervised classification identifies well five classes: bare soil, grassland, steppe, shrub savanna and tree savanna. We then refined this classification to enable us to identify the species composition in an area utilizing the phenological differences in timing and duration of greenness of the dominant tree and shrub species in Etosha. Specifically, using multi-date images we were able to

  2. DNA Methylation Landscapes of Human Fetal Development.

    PubMed

    Slieker, Roderick C; Roost, Matthias S; van Iperen, Liesbeth; Suchiman, H Eka D; Tobi, Elmar W; Carlotti, Françoise; de Koning, Eelco J P; Slagboom, P Eline; Heijmans, Bastiaan T; Chuva de Sousa Lopes, Susana M

    2015-10-01

    Remodelling the methylome is a hallmark of mammalian development and cell differentiation. However, current knowledge of DNA methylation dynamics in human tissue specification and organ development largely stems from the extrapolation of studies in vitro and animal models. Here, we report on the DNA methylation landscape using the 450k array of four human tissues (amnion, muscle, adrenal and pancreas) during the first and second trimester of gestation (9,18 and 22 weeks). We show that a tissue-specific signature, constituted by tissue-specific hypomethylated CpG sites, was already present at 9 weeks of gestation (W9). Furthermore, we report large-scale remodelling of DNA methylation from W9 to W22. Gain of DNA methylation preferentially occurred near genes involved in general developmental processes, whereas loss of DNA methylation mapped to genes with tissue-specific functions. Dynamic DNA methylation was associated with enhancers, but not promoters. Comparison of our data with external fetal adrenal, brain and liver revealed striking similarities in the trajectory of DNA methylation during fetal development. The analysis of gene expression data indicated that dynamic DNA methylation was associated with the progressive repression of developmental programs and the activation of genes involved in tissue-specific processes. The DNA methylation landscape of human fetal development provides insight into regulatory elements that guide tissue specification and lead to organ functionality.

  3. Carbon Accumulation and Nitrogen Pool Recovery during Transitions from Savanna to Forest in Central Brazil

    NASA Astrophysics Data System (ADS)

    Pellegrini, A.; Hoffmann, W. A.; Franco, A. C.

    2014-12-01

    landscapes. In turn, the link between forest development and nitrogen pool recovery creates a framework for evaluating potential positive feedbacks on savanna-forest boundaries.

  4. Influence of Fire Mosaics, Habitat Characteristics and Cattle Disturbance on Mammals in Fire-Prone Savanna Landscapes of the Northern Kimberley.

    PubMed

    Radford, Ian J; Gibson, Lesley A; Corey, Ben; Carnes, Karin; Fairman, Richard

    2015-01-01

    Patch mosaic burning, in which fire is used to produce a mosaic of habitat patches representative of a range of fire histories ('pyrodiversity'), has been widely advocated to promote greater biodiversity. However, the details of desired fire mosaics for prescribed burning programs are often unspecified. Threatened small to medium-sized mammals (35 g to 5.5 kg) in the fire-prone tropical savannas of Australia appear to be particularly fire-sensitive. Consequently, a clear understanding of which properties of fire mosaics are most instrumental in influencing savanna mammal populations is critical. Here we use mammal capture data, remotely sensed fire information (i.e. time since last fire, fire frequency, frequency of late dry season fires, diversity of post-fire ages in 3 km radius, and spatial extent of recently burnt, intermediate and long unburnt habitat) and structural habitat attributes (including an index of cattle disturbance) to examine which characteristics of fire mosaics most influence mammals in the north-west Kimberley. We used general linear models to examine the relationship between fire mosaic and habitat attributes on total mammal abundance and richness, and the abundance of the most commonly detected species. Strong negative associations of mammal abundance and richness with frequency of late dry season fires, the spatial extent of recently burnt habitat (post-fire age <1 year within 3 km radius) and level of cattle disturbance were observed. Shrub cover was positively related to both mammal abundance and richness, and availability of rock crevices, ground vegetation cover and spatial extent of ≥4 years unburnt habitat were all positively associated with at least some of the mammal species modelled. We found little support for diversity of post-fire age classes in the models. Our results indicate that both a high frequency of intense late dry season fires and extensive, recently burnt vegetation are likely to be detrimental to mammals in the

  5. Influence of Fire Mosaics, Habitat Characteristics and Cattle Disturbance on Mammals in Fire-Prone Savanna Landscapes of the Northern Kimberley

    PubMed Central

    Radford, Ian J.; Gibson, Lesley A.; Corey, Ben; Carnes, Karin; Fairman, Richard

    2015-01-01

    Patch mosaic burning, in which fire is used to produce a mosaic of habitat patches representative of a range of fire histories (‘pyrodiversity’), has been widely advocated to promote greater biodiversity. However, the details of desired fire mosaics for prescribed burning programs are often unspecified. Threatened small to medium-sized mammals (35 g to 5.5 kg) in the fire-prone tropical savannas of Australia appear to be particularly fire-sensitive. Consequently, a clear understanding of which properties of fire mosaics are most instrumental in influencing savanna mammal populations is critical. Here we use mammal capture data, remotely sensed fire information (i.e. time since last fire, fire frequency, frequency of late dry season fires, diversity of post-fire ages in 3 km radius, and spatial extent of recently burnt, intermediate and long unburnt habitat) and structural habitat attributes (including an index of cattle disturbance) to examine which characteristics of fire mosaics most influence mammals in the north-west Kimberley. We used general linear models to examine the relationship between fire mosaic and habitat attributes on total mammal abundance and richness, and the abundance of the most commonly detected species. Strong negative associations of mammal abundance and richness with frequency of late dry season fires, the spatial extent of recently burnt habitat (post-fire age <1 year within 3 km radius) and level of cattle disturbance were observed. Shrub cover was positively related to both mammal abundance and richness, and availability of rock crevices, ground vegetation cover and spatial extent of ≥4 years unburnt habitat were all positively associated with at least some of the mammal species modelled. We found little support for diversity of post-fire age classes in the models. Our results indicate that both a high frequency of intense late dry season fires and extensive, recently burnt vegetation are likely to be detrimental to mammals in the

  6. Genomic Landscape of Developing Male Germ Cells

    PubMed Central

    Lee, Tin-Lap; Pang, Alan Lap-Yin; Rennert, Owen M.; Chan, Wai-Yee

    2010-01-01

    Spermatogenesis is a highly orchestrated developmental process by which spermatogonia develop into mature spermatozoa. This process involves many testis- or male germ cell-specific gene products whose expressions are strictly regulated. In the past decade the advent of high-throughput gene expression analytical techniques has made functional genomic studies of this process, particularly in model animals such as mice and rats, feasible and practical. These studies have just begun to reveal the complexity of the genomic landscape of the developing male germ cells. Over 50% of the mouse and rat genome are expressed during testicular development. Among transcripts present in germ cells, 40% – 60% are uncharacterized. A number of genes, and consequently their associated biological pathways, are differentially expressed at different stages of spermatogenesis. Developing male germ cells present a rich repertoire of genetic processes. Tissue-specific as well as spermatogenesis stage-specific alternative splicing of genes exemplifies the complexity of genome expression. In addition to this layer of control, discoveries of abundant presence of antisense transcripts, expressed psuedogenes, non-coding RNAs (ncRNA) including long ncRNAs, microRNAs (miRNAs) and Piwi-interacting RNAs (piRNAs), and retrogenes all point to the presence of multiple layers of expression and functional regulation in male germ cells. It is anticipated that application of systems biology approaches will further our understanding of the regulatory mechanism of spermatogenesis.† PMID:19306351

  7. Fire drives functional thresholds on the savanna-forest transition.

    PubMed

    Dantas, Vinícius de L; Batalha, Marco A; Pausas, Juli G

    2013-11-01

    In tropical landscapes, vegetation patches with contrasting tree densities are distributed as mosaics. However, the locations of patches and densities of trees within them cannot be predicted by climate models alone. It has been proposed that plant-fire feedbacks drive functional thresholds at a landscape scale, thereby maintaining open (savanna) and closed (forest) communities as two distinct stable states. However, there is little rigorous field evidence for this threshold model. Here we aim to provide support for such a model from a field perspective and to analyze the functional and phylogenetic consequences of fire in a Brazilian savanna landscape (Cerrado). We hypothesize that, in tropical landscapes, savanna and forest are two stable states maintained by plant-fire feedbacks. If so, their functional and diversity attributes should change abruptly along a community closure gradient. We set 98 plots along a gradient from open savanna to closed forest in the Brazilian Cerrado and tested for a threshold pattern in nine functional traits, five soil features, and seven diversity indicators. We then tested whether the threshold pattern was associated with different fire regimes. Most community attributes presented a threshold pattern on the savanna-forest transition with coinciding breakpoints. The thresholds separated two community states: (1) open environments with low-diversity communities growing in poor soils and dominated by plants that are highly resistant to high-intensity fires; and (2) closed environments with highly diverse plant communities growing in more fertile soils and dominated by shade-tolerant species that efficiently prevent light from reaching the understory. In addition, each state was associated with contrasting fire regimes. Our results are consistent with the hypothesis that forests and savannas are two coexisting stable states with contrasting patterns of function and diversity that are regulated by fire-plant feedbacks; our results also

  8. EFFECTS OF PRESCRIBED FIRES ON NITROGEN FLUXES IN SAVANNA FORMATIONS OF CENTRAL BRAZIL

    EPA Science Inventory

    Savanna ecosystems are controlled by the interactions between water and nutrient availability. The savannas of Central Brazil (Cerrado) are the second most extensive plant formation in tropical South America with two million km2 of area. The Cerrado landscape contains different ...

  9. Landscape development, forest fires, and wilderness management.

    PubMed

    Wright, H E

    1974-11-01

    Both the landforms and the vegetation of the earth develop to states that are maintained in dynamic equilibrium. Short-term equilibrium of a hillslope or river valley results from intersection between erosional and depositional tendencies, controlled by gravitational force and the efficiency of the transporting medium. Long-term equilibrium of major landforms depends on crustal uplift and the resistance of the rock to weathering. In most parts of the world landscape evolves toward a peneplain, but the reduction rate approaches zero as the cycle progresses, and the counteracting force of crustal uplift intercedes before the end form is reached. Davis described this theoretical model in elegant terms. Leopold and Hack have provided a new and quantitative understanding of short-range geomorphic interactions that tend to discredit the Davisian model in the eyes of many. However, the substitute models of quasi-equilibrium or dynamic equilibrium merely describe short-range situations in which this or that Davisian stage is maintained despite uplift or downwasting. Given crustal stability and an unchanging climate, landforms would presumably still evolve through Davisian stages. However, the Davis model cannot be tested, for despite tremendous inventions in geochronology and impressive advances in stratigraphic knowledge, we cannot yet establish the rates or even the fact of crustal uplift in most areas. We are left with an unresolvable problem, for the sedimentary records of erosional history are largely inaccessible, undatable, and indecipherable, at least in the detail necessary to describe long-term evolution of the landscape. We know more about the evolution and maintenance of vegetation assemblages than about landform evolution, for even long-term vegetation sequences are within the scope of radiocarbon dating, and the biostratigraphic record is detailed. Even here, however, distinctions between short-term and long-term situations must be made, so that Clements

  10. Landscape development, forest fires, and wilderness management.

    PubMed

    Wright, H E

    1974-11-01

    Both the landforms and the vegetation of the earth develop to states that are maintained in dynamic equilibrium. Short-term equilibrium of a hillslope or river valley results from intersection between erosional and depositional tendencies, controlled by gravitational force and the efficiency of the transporting medium. Long-term equilibrium of major landforms depends on crustal uplift and the resistance of the rock to weathering. In most parts of the world landscape evolves toward a peneplain, but the reduction rate approaches zero as the cycle progresses, and the counteracting force of crustal uplift intercedes before the end form is reached. Davis described this theoretical model in elegant terms. Leopold and Hack have provided a new and quantitative understanding of short-range geomorphic interactions that tend to discredit the Davisian model in the eyes of many. However, the substitute models of quasi-equilibrium or dynamic equilibrium merely describe short-range situations in which this or that Davisian stage is maintained despite uplift or downwasting. Given crustal stability and an unchanging climate, landforms would presumably still evolve through Davisian stages. However, the Davis model cannot be tested, for despite tremendous inventions in geochronology and impressive advances in stratigraphic knowledge, we cannot yet establish the rates or even the fact of crustal uplift in most areas. We are left with an unresolvable problem, for the sedimentary records of erosional history are largely inaccessible, undatable, and indecipherable, at least in the detail necessary to describe long-term evolution of the landscape. We know more about the evolution and maintenance of vegetation assemblages than about landform evolution, for even long-term vegetation sequences are within the scope of radiocarbon dating, and the biostratigraphic record is detailed. Even here, however, distinctions between short-term and long-term situations must be made, so that Clements

  11. Lidar remote sensing of savanna biophysical attributes

    NASA Astrophysics Data System (ADS)

    Gwenzi, David

    plot level biomass into wall-to-wall maps that provide more ecological information. We evaluated the utility of three spatial modeling approaches to address this problem: deterministic methods, geostatistical methods and an image segmentation approach. Overall, the mean pixel biomass estimated by the 3 approaches did not differ significantly but the output maps showed marked differences in the estimation precision and ability of each model to mimic the primary variable's trend across the landscape. The results emphasized the need for future satellite lidar missions to consider increasing the sampling intensity across track so that biomass observations are made and characterized at the scale at which they vary. We used data from the Multiple Altimeter Beam Experimental Lidar (MABEL), an airborne photon counting lidar sensor developed by NASA Goddard to simulate ICESat-2 data. We segmented each transect into different block sizes and calculated canopy top and mean ground elevation based on the structure of the histogram of the block's aggregated photons. Our algorithm was able to compute canopy height and generate visually meaningful vegetation profiles at MABEL's signal and noise levels but a simulation of the expected performance of ICESat-2 by adjusting MABEL data's detected number of signal and noise photons to that predicted using ATLAS instrument model design cases indicated that signal photons will be substantially lower. The lower data resolution reduces canopy height estimation precision especially in areas of low density vegetation cover. Given the clear difficulties in processing simulated ATLAS data, it appears unlikely that it will provide the kind of data required for mapping of the biophysical properties of savanna vegetation. Rather, resources are better concentrated on preparing for the Global Ecosystem Dynamics Investigation (GEDI) mission, a waveform lidar mission scheduled to launch by the end of this decade. In addition to the full waveform technique

  12. Lidar remote sensing of savanna biophysical attributes

    NASA Astrophysics Data System (ADS)

    Gwenzi, David

    plot level biomass into wall-to-wall maps that provide more ecological information. We evaluated the utility of three spatial modeling approaches to address this problem: deterministic methods, geostatistical methods and an image segmentation approach. Overall, the mean pixel biomass estimated by the 3 approaches did not differ significantly but the output maps showed marked differences in the estimation precision and ability of each model to mimic the primary variable's trend across the landscape. The results emphasized the need for future satellite lidar missions to consider increasing the sampling intensity across track so that biomass observations are made and characterized at the scale at which they vary. We used data from the Multiple Altimeter Beam Experimental Lidar (MABEL), an airborne photon counting lidar sensor developed by NASA Goddard to simulate ICESat-2 data. We segmented each transect into different block sizes and calculated canopy top and mean ground elevation based on the structure of the histogram of the block's aggregated photons. Our algorithm was able to compute canopy height and generate visually meaningful vegetation profiles at MABEL's signal and noise levels but a simulation of the expected performance of ICESat-2 by adjusting MABEL data's detected number of signal and noise photons to that predicted using ATLAS instrument model design cases indicated that signal photons will be substantially lower. The lower data resolution reduces canopy height estimation precision especially in areas of low density vegetation cover. Given the clear difficulties in processing simulated ATLAS data, it appears unlikely that it will provide the kind of data required for mapping of the biophysical properties of savanna vegetation. Rather, resources are better concentrated on preparing for the Global Ecosystem Dynamics Investigation (GEDI) mission, a waveform lidar mission scheduled to launch by the end of this decade. In addition to the full waveform technique

  13. Towards developing Kentucky's landscape change maps

    USGS Publications Warehouse

    Zourarakis, D.P.; Lambert, S.C.; Palmer, M.

    2003-01-01

    The Kentucky Landscape Snapshot Project, a NASA-funded project, was established to provide a first baseline land cover/land use map for Kentucky. Through this endeavor, change detection will be institutionalized, thus aiding in decision-making at the local, state, and federal planning levels. 2002 Landsat 7 imaginery was classified following and Anderson Level III scheme, providing an enhancement over the 1992 USGS National Land Cover Data Set. Also as part of the deliverables, imperviousness and canopy closure layers were produced with the aid of IKONOS high resolution, multispectral imagery.

  14. Nutrient limitation in tropical savannas across multiple scales and mechanisms.

    PubMed

    Pellegrini, Adam F A

    2016-02-01

    Nutrients have been hypothesized to influence the distribution of the savanna biome through two possible mechanisms. Low nutrient availability may restrict growth rates of trees, thereby allowing for intermittent fires to maintain low tree cover; alternatively, nutrient deficiency may even place an absolute constraint on the ability of forests to form, independent of fire. However, we have little understanding of the scales at which nutrient limitation operates, what nutrients are limiting, and the mechanisms that influence how nutrient limitation regulates savanna-forest transitions. Here, I review literature, synthesize existing data, and present a simple calculation of nutrient demand to evaluate how nutrient limitation may regulate the distribution of the savanna biome. The literature primarily supports the hypothesis that nutrients may interact dynamically with fire to restrict the transition of savanna into forest. A compilation of indirect metrics of nutrient limitation suggest that nitrogen and phosphorus are both in short supply and may limit plants. Nutrient demand calculations provided a number of insights. First, trees required high rates of nitrogen and phosphorus supply relative to empirically determined inputs. Second, nutrient demand increased as landscapes approached the transition point between savanna and forest. Third, the potential for fire-driven nutrient losses remained high throughout transitions, which may exaggerate limitation and could be a key feedback stabilizing the savanna biome. Fourth, nutrient limitation varied between functional groups, with fast-growing forest species having substantially greater nutrient demand and a higher susceptibility to fire-driven nutrient losses. Finally, African savanna trees required substantially larger amounts of nutrients supplied at greater rates, although this varied across plant functional groups. In summary, the ability of nutrients to control transitions emerges at individual and landscape

  15. Nutrient limitation in tropical savannas across multiple scales and mechanisms.

    PubMed

    Pellegrini, Adam F A

    2016-02-01

    Nutrients have been hypothesized to influence the distribution of the savanna biome through two possible mechanisms. Low nutrient availability may restrict growth rates of trees, thereby allowing for intermittent fires to maintain low tree cover; alternatively, nutrient deficiency may even place an absolute constraint on the ability of forests to form, independent of fire. However, we have little understanding of the scales at which nutrient limitation operates, what nutrients are limiting, and the mechanisms that influence how nutrient limitation regulates savanna-forest transitions. Here, I review literature, synthesize existing data, and present a simple calculation of nutrient demand to evaluate how nutrient limitation may regulate the distribution of the savanna biome. The literature primarily supports the hypothesis that nutrients may interact dynamically with fire to restrict the transition of savanna into forest. A compilation of indirect metrics of nutrient limitation suggest that nitrogen and phosphorus are both in short supply and may limit plants. Nutrient demand calculations provided a number of insights. First, trees required high rates of nitrogen and phosphorus supply relative to empirically determined inputs. Second, nutrient demand increased as landscapes approached the transition point between savanna and forest. Third, the potential for fire-driven nutrient losses remained high throughout transitions, which may exaggerate limitation and could be a key feedback stabilizing the savanna biome. Fourth, nutrient limitation varied between functional groups, with fast-growing forest species having substantially greater nutrient demand and a higher susceptibility to fire-driven nutrient losses. Finally, African savanna trees required substantially larger amounts of nutrients supplied at greater rates, although this varied across plant functional groups. In summary, the ability of nutrients to control transitions emerges at individual and landscape

  16. The application of local measures of spatial autocorrelation for describing pattern in north Australian landscapes.

    PubMed

    Pearson, Diane M

    2002-01-01

    This paper tests the use of a spatial analysis technique, based on the calculation of local spatial autocorrelation, as a possible approach for modelling and quantifying structure in northern Australian savanna landscapes. Unlike many landscapes in the world, northern Australian savanna landscapes appear on the surface to be intact. They have not experienced the same large-scale land clearance and intensive land management as other landscapes across Australia. Despite this, natural resource managers are beginning to notice that processes are breaking down and declines in species are becoming more evident. With future declines of species looking more imminent it is particularly important that models are available that can help to assess landscape health, and quantify any structural change that takes place. GIS and landscape ecology provide a useful way of describing landscapes both spatially and temporally and have proved to be particularly useful for understanding vegetation structure or pattern in landscapes across the world. There are many measures that examine spatial structure in the landscape and most of these are now available in a GIS environment (e.g. FRAGSTATS* ARC, r.le, and Patch Analyst). All these methods depend on a landscape described in terms of patches, corridors and matrix. However, since landscapes in northern Australia appear to be relatively intact they tend to exist as surfaces of continuous variation rather than in clearly defined homogeneous units. As a result they cannot be easily described using entity-based models requiring patches and other essentially cartographic approaches. This means that more appropriate methods need to be developed and explored. The approach examined in this paper enables clustering and local pattern in the data to be identified and forms a generic method for conceptualising the landscape structure where patches are not obvious and where boundaries between landscape features are difficult to determine. Two sites

  17. Climatic Limits on Landscape Development in the Northwestern Himalaya

    PubMed

    Brozović; Burbank; Meigs

    1997-04-25

    The interaction between tectonism and erosion produces rugged landscapes in actively deforming regions. In the northwestern Himalaya, the form of the landscape was found to be largely independent of exhumation rates, but regional trends in mean and modal elevations, hypsometry (frequency distribution of altitude), and slope distributions were correlated with the extent of glaciation. These observations imply that in mountain belts that intersect the snowline, glacial and periglacial processes place an upper limit on altitude, relief, and the development of topography irrespective of the rate of tectonic processes operating.

  18. Career Development in Canada: A Changing Landscape.

    ERIC Educational Resources Information Center

    Kellett, Ralph

    In Canada, responsibility for the career development delivery system is divided among federal, provincial/territorial, and municipal levels of government. Education comes under provincial/territorial jurisdiction. Career development varies across provinces and often from school to school. There are eight transition points throughout the school…

  19. Tree and stand transpiration in a Midwestern bur oak savanna after elm encroachment and restoration thinning

    USGS Publications Warehouse

    Asbjornsen, H.; Tomer, M.D.; Gomez-Cardenas, M.; Brudvig, L.A.; Greenan, C.M.; Schilling, K.

    2007-01-01

    Oak savannas, once common in the Midwest, are now isolated remnants within agricultural landscapes. Savanna remnants are frequently encroached by invasive trees to become woodlands. Thinning and prescribed burning can restore savanna structure, but the ecohydrological effects of managing these remnants are poorly understood. In this study, we measured sap flow (Js) to quantify transpiration in an Iowa bur oak (Quercus macrocarpa) savanna woodland encroached by elms (Ulmus americana), and in an adjacent restored savanna after thinning to remove elms, during summer 2004. Savanna oaks had greater mean daily Js (35.9 L dm-2 day-1) than woodland oaks (20.7 L dm-2 day-1) and elms (12.4 L dm-2 day-1). The response of Js to vapor pressure deficit (D) was unexpectedly weak, although oaks in both stands showed negative correlation between daily Js and D for D > 0.4 kPa. An earlier daily peak in Js in the elm trees showed a possible advantage for water uptake. As anticipated, the woodland's stand transpiration was greater (1.23 mm day-1) than the savanna's (0.35 mm day-1), yet the savanna achieved 30% of the woodland's transpiration with only 11% of its sapwood area. The difference in transpiration influenced water table depths, which were 2 m in the savanna and 6.5 m in the woodland. Regionally, row-crop agriculture has increased groundwater recharge and raised water tables, providing surplus water that perhaps facilitated elm encroachment. This has implications for restoration of savanna remnants. If achieving a savanna ecohydrology is an aim of restoration, then restoration strategies may require buffers, or targeting of large or hydrologically isolated remnants. ?? 2007.

  20. The dynamic landscape of exceptional language development.

    PubMed

    Peltzer-Karpf, Annemarie

    2012-06-01

    Developmental neurocognitive studies have shown that the brain systems supporting the emergence of sensory and cognitive abilities display different profiles of neuroplasticity. The research question posed here is to what extent sensory deprivation influences the dynamics of language development. The findings reported are grounded in studies with vision-impaired children with sighted peers featured as controls (age range 18 months to 3 years). Their data are matched against findings on advanced language development in blind children (age range: from 6 to 10 years; N = 12) and hearing-impaired and deaf children (age range: from 5 to 11 years; N = 20). The data give evidence that language acquisition in sensory-impaired children follows the same overall developmental path with respect to macrostructural changes and the succession of phase-shifts. System-specific temporal discrepancies expressed in protracted phase-shifts and delayed increases of variability are most evident in the early phases. Self-organizing maps (SOMs) help to visualize individual and group-specific variation. The dynamic framework used (1) shows a higher sensibility to system-specific changes, (2) enhances the informative value of the data assessed, and (3) facilitates reliable prognoses concerning the child's cognitive and linguistic future.

  1. Hillslope Chromatography in Savannas

    NASA Astrophysics Data System (ADS)

    Hartshorn, A.; Khomo, L.; Chadwick, O.; Rogers, K.; Kurtz, A.; Heimsath, A.

    2005-12-01

    In semiarid ecosystems, vegetation patterns are controlled in part by soil water availability. Along hillslopes in Kruger National Park, South Africa, water availability is strongly dependent on soil texture and textural differences with depth, which are a function of landscape position (convergent or divergent crests, midslopes, and footslopes) and parent material. We are studying weathering and landscape development on the western side of the park, which is underlain by granitic gneisses. Hillslopes in the park are often described as catenas, where rainfall catalyzes chemical weathering and drives the downslope transport of clays and weathering products, forming a predictable sequence of soil types. Sandy crest soils grade to midslope soils where sandy surface horizons overlie clayey subsurface horizons; footslopes generally have higher volumetric clay contents. The boundary between the sandy and clayey soils is of ecological significance because this is the location where run-on from upslope landscape positions is diverted to the surface, initiating overland flow and reducing infiltration. In a geochemical sense these hillslopes can be thought of as chromatographic columns that accentuate differential solute mobility along the long (~1-2 km) potential flowpaths. We use the compound topographic index (a terrain attribute that indexes soil wetness by dividing the upslope contributing area by the slope) to predict the redistribution of clays across these semiarid hillslopes and hope to demonstrate that landscape positions occupying comparable plan and profile curvatures contain clay and organic carbon in proportion to contributing area. Thus far, we have derived contributing area values for 40 soil pits using LiDAR-based digital elevation models and then tested how well contributing area and other terrain attributes predicted clay and carbon content for 218 horizons at these 40 locations. Depth-weighted soil clay ranged from 3 to 25% and total soil carbon ranged

  2. From Forest Landscape to Agricultural Landscape in the Developing Tropical Country of Malaysia: Pattern, Process, and Their Significance on Policy

    NASA Astrophysics Data System (ADS)

    Abdullah, Saiful Arif; Hezri, Adnan A.

    2008-11-01

    Agricultural expansion and deforestation are spatial processes of land transformation that impact on landscape pattern. In peninsular Malaysia, the conversion of forested areas into two major cash crops—rubber and oil palm plantations—has been identified as driving significant environmental change. To date, there has been insufficient literature studying the link between changes in landscape patterns and land-related development policies. Therefore, this paper examines: (i) the links between development policies and changes in land use/land cover and landscape pattern and (ii) the significance and implications of these links for future development policies. The objective is to generate insights on the changing process of land use/land cover and landscape pattern as a functional response to development policies and their consequences for environmental conditions. Over the last century, the development of cash crops has changed the country from one dominated by natural landscapes to one dominated by agricultural landscapes. But the last decade of the century saw urbanization beginning to impact significantly. This process aligned with the establishment of various development policies, from land development for agriculture between the mid 1950s and the 1970s to an emphasis on manufacturing from the 1980s onward. Based on a case study in Selangor, peninsular Malaysia, a model of landscape pattern change is presented. It contains three stages according to the relative importance of rubber (first stage: 1900-1950s), oil palm (second stage: 1960s-1970s), and urban (third stage: 1980s-1990s) development that influenced landscape fragmentation and heterogeneity. The environmental consequences of this change have been depicted through loss of biodiversity, geohazard incidences, and the spread of vector-borne diseases. The spatial ecological information can be useful to development policy formulation, allowing diagnosis of the country’s “health” and sustainability

  3. From forest landscape to agricultural landscape in the developing tropical country of Malaysia: pattern, process, and their significance on policy.

    PubMed

    Abdullah, Saiful Arif; Hezri, Adnan A

    2008-11-01

    Agricultural expansion and deforestation are spatial processes of land transformation that impact on landscape pattern. In peninsular Malaysia, the conversion of forested areas into two major cash crops--rubber and oil palm plantations--has been identified as driving significant environmental change. To date, there has been insufficient literature studying the link between changes in landscape patterns and land-related development policies. Therefore, this paper examines: (i) the links between development policies and changes in land use/land cover and landscape pattern and (ii) the significance and implications of these links for future development policies. The objective is to generate insights on the changing process of land use/land cover and landscape pattern as a functional response to development policies and their consequences for environmental conditions. Over the last century, the development of cash crops has changed the country from one dominated by natural landscapes to one dominated by agricultural landscapes. But the last decade of the century saw urbanization beginning to impact significantly. This process aligned with the establishment of various development policies, from land development for agriculture between the mid 1950s and the 1970s to an emphasis on manufacturing from the 1980s onward. Based on a case study in Selangor, peninsular Malaysia, a model of landscape pattern change is presented. It contains three stages according to the relative importance of rubber (first stage: 1900--1950s), oil palm (second stage: 1960s--1970s), and urban (third stage: 1980s--1990s) development that influenced landscape fragmentation and heterogeneity. The environmental consequences of this change have been depicted through loss of biodiversity, geohazard incidences, and the spread of vector-borne diseases. The spatial ecological information can be useful to development policy formulation, allowing diagnosis of the country's "health" and sustainability. The

  4. The contribution of trees and grasses to productivity of an Australian tropical savanna

    NASA Astrophysics Data System (ADS)

    Moore, Caitlin E.; Beringer, Jason; Evans, Bradley; Hutley, Lindsay B.; McHugh, Ian; Tapper, Nigel J.

    2016-04-01

    Savanna ecosystems cover 20 % of the global land surface and account for 25 % of global terrestrial carbon uptake. They support one fifth of the world's human population and are one of the most important ecosystems on our planet. Savanna productivity is a product of the interplay between trees and grass that co-dominate savanna landscapes and are maintained through interactions with climate and disturbance (fire, land use change, herbivory). In this study, we evaluate the temporally dynamic partitioning of overstory and understory carbon dioxide fluxes in Australian tropical savanna using overstory and understory eddy covariance measurements. Over a 2-year period (September 2012 to October 2014) the overall net ecosystem productivity (NEP) of the savanna was 506.2 (±22 SE) g C m-2 yr-1. The total gross primary productivity (GPP) was 2267.1 (±80 SE) g C m-2 yr-1, of which the understory contributed 32 %. The understory contribution was strongly seasonal, with most GPP occurring in the wet season (40 % of total ecosystem in the wet season and 18 % in the dry). This study is the first to elucidate the temporal dynamics of savanna understory and overstory carbon flux components explicitly using observational information. Understanding grass productivity is crucial for evaluating fuel loads, as is tree productivity for quantifying the tree carbon sink. This information will contribute to a significant refinement of the representation of savannas in models, as well as improved understanding of relative tree-grass productivity and competition for resources.

  5. The contribution of trees and grasses to productivity of an Australian tropical savanna

    NASA Astrophysics Data System (ADS)

    Moore, C. E.; Beringer, J.; Evans, B.; Hutley, L. B.; McHugh, I.; Tapper, N. J.

    2015-12-01

    Savanna ecosystems cover 20 % of the global land surface and account for 25 % of global terrestrial carbon uptake. They support one fifth of the world's human population and are one of the most important ecosystems on our planet. Savanna productivity is a product of the interplay between trees and grass that co-dominate savanna landscapes and are maintained through interactions with climate and disturbance (fire, land use change, herbivory). In this study, we evaluate the temporally dynamic partitioning of overstory and understory carbon dioxide fluxes in Australian tropical savanna using overstory and understory eddy covariance measurements. Over a two year period (September 2012 to October 2014) the overall net ecosystem productivity (NEP) of the savanna was 506.2 (±22 SE) g C m-2 yr-1. The total gross primary productivity (GPP) was 2267.1 (±80 SE) g C m-2 yr-1, of which the understory contributed 32 %. The understory contribution was strongly seasonal, with most GPP occurring in the wet season (40 % of total ecosystem in the wet season and 18 % in the dry). This study is the first to elucidate the temporal dynamics of savanna understory and overstory carbon flux components explicitly using observational information. Understanding grass productivity is crucial for evaluating fuel loads, as is tree productivity for quantifying the tree carbon sink. This information will contribute to a significant refinement of the representation of savannas in models, as well as improved understanding of relative tree-grass productivity and competition for resources.

  6. Land use scenarios development and impacts assessment on vegetation carbon/nitrogen sequestration in the West African Sudan savanna watershed, Benin

    NASA Astrophysics Data System (ADS)

    Chabi, A.

    2015-12-01

    AbstractBackground: Reduced Emissions from Deforestation and Degradation (REDD+), being developed through the United Nations Framework Convention on Climate Change (UNFCCC) requires information on the carbon/nitrogen stocks in the plant biomass for predicting future climate under scenarios development. The development of land use scenarios in West Africa is needed to predict future impacts of change in the environment and the socio-economic status of rural communities. The study aims at developing land use scenario based on mitigation strategy to climate change as an issue of contributing for carbon and nitrogen sequestration, the condition 'food focused' as a scenario based crop production and 'financial investment' as scenario based on an economic development pathway, and to explore the possible future temporal and spatial impacts on vegetation carbon/nitrogen sequestration/emission and socio-economic status of rural communities. Preliminary results: BEN-LUDAS (Benin-Land Use DyNamic Simulator) model, carbon and nitrogen equations, remote sensing and socio-economic data were used to predict the future impacts of each scenario in the environment and human systems. The preliminary results which are under analysis will be presented soon. Conclusion: The proposed BEN-LUDAS models will help to contribute to policy decision making at the local and regional scale and to predict future impacts of change in the environment and socio-economic status of the rural communities. Keywords: Land use scenarios development, BEN-LUDAS, socio-economic status of rural communities, future impacts of change, assessment, West African Sudan savanna watershed, Benin

  7. Land use scenarios development and impacts assessment on vegetation carbon/nitrogen sequestration in the West African Sudan savanna watershed, Benin

    NASA Astrophysics Data System (ADS)

    Chabi, A.

    2015-12-01

    ackground: Reduced Emissions from Deforestation and Degradation (REDD+), being developed through the United Nations Framework Convention on Climate Change (UNFCCC) requires information on the carbon/nitrogen stocks in the plant biomass for predicting future climate under scenarios development. The development of land use scenarios in West Africa is needed to predict future impacts of change in the environment and the socio-economic status of rural communities. The study aims at developing land use scenario based on mitigation strategy to climate change as an issue of contributing for carbon and nitrogen sequestration, the condition 'food focused' as a scenario based crop production and 'financial investment' as scenario based on an economic development pathway, and to explore the possible future temporal and spatial impacts on vegetation carbon/nitrogen sequestration/emission and socio-economic status of rural communities. Preliminary results: BEN-LUDAS (Benin-Land Use DyNamic Simulator) model, carbon and nitrogen equations, remote sensing and socio-economic data were used to predict the future impacts of each scenario in the environment and human systems. The preliminary results which are under analysis will be presented soon. Conclusion: The proposed BEN-LUDAS models will help to contribute to policy decision making at the local and regional scale and to predict future impacts of change in the environment and socio-economic status of the rural communities. Keywords: Land use scenarios development, BEN-LUDAS, socio-economic status of rural communities, future impacts of change, assessment, West African Sudan savanna watershed, Benin

  8. Tectonic and Climatic Controls on Landscape Development of Puerto Rico

    NASA Astrophysics Data System (ADS)

    Rogers, R. D.; Salas, M.; Colon, A.

    2007-12-01

    The northeastern Caribbean island of Puerto Rico is an exhumed Cenozoic island arc situated between the inactive Muertos trench to the south and the highly oblique Puerto Rican Trench to the north that forms the left- lateral strike-slip plate margin with North America. The rectangular island's long axis of 175 km parallels the east trending strike of the trenches with a near constant width of between 50 and 60 km. Puerto Rico receives the NE trade winds and has a tropical monsoonal climate. Puerto Rico has a distinct midline asymmetry with north draining watershed about twice the length and five times as large as south draining watershed. This midline asymmetry is more pronounced along the islands eastern third than the central or western thirds. River outlet spacing, mountain front sinuosity, and comparative hypsometry display similar east to west variability consistent with greater denudation in the eastern parts of the island. The southwestern fifth of the island is underlain by serpentinized ocean crust that forms the large diapiric Monte del Estado uplift. Active diapirism is indicated by highly asymmetric watersheds of the surrounding rivers and tributaries. Stream length gradient index calculated from 1:20,000 scale map data and compared to fault locations show little correlation suggesting that active faults does not significantly control Puerto Rico's landscape. Quantified morphologic data from the eastern two-thirds of Puerto Rico are consistent with a landscape developed in response to the precipitation derived from NE trade winds while serpentinite diapirism dominates the western third of the island. Individual active faults of Puerto Rico do not control the landscape development.

  9. Transposon tools: worldwide landscape of intellectual property and technological developments.

    PubMed

    Palazzoli, Fabien; Testu, François-Xavier; Merly, Franck; Bigot, Yves

    2010-03-01

    DNA transposons are considered to be good candidates for developing tools for genome engineering, insertional mutagenesis and gene delivery for therapeutic purposes, as illustrated by the recent first clinical trial of a transposon. In this article we set out to highlight the interest of patent information, and to develop a strategy for the technological development of transposon tools, similar to what has been done in many other fields. We propose a patent landscape for transposon tools, including the changes in international patent applications, and review the leading inventors and applicants. We also provide an overview of the potential patent portfolio for the prokaryotic and eukaryotic transposons that are exploited by spin-off companies. Finally, we discuss the difficulties involved in tracing relevant state-of-the-art of articles and patent documents, based on the example of one of the most promising transposon systems, including all the impacts on the technological development of transposon tools.

  10. 36 CFR 219.12 - Collaboration and cooperatively developed landscape goals.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Collaborative Planning for Sustainability § 219.12 Collaboration and cooperatively developed landscape goals. (a) Collaboration. To promote sustainability, the responsible official must actively engage the American...

  11. 36 CFR 219.12 - Collaboration and cooperatively developed landscape goals.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Collaborative Planning for Sustainability § 219.12 Collaboration and cooperatively developed landscape goals. (a) Collaboration. To promote sustainability, the responsible official must actively engage the American...

  12. Contributions of woody and herbaceous vegetation to tropical savanna ecosystem productivity: a quasi-global estimate.

    PubMed

    Lloyd, Jon; Bird, Michael I; Vellen, Lins; Miranda, Antonio Carlos; Veenendaal, Elmar M; Djagbletey, Gloria; Miranda, Heloisa S; Cook, Garry; Farquhar, Graham D

    2008-03-01

    To estimate the relative contributions of woody and herbaceous vegetation to savanna productivity, we measured the 13C/12C isotopic ratios of leaves from trees, shrubs, grasses and the surface soil carbon pool for 22 savannas in Australia, Brazil and Ghana covering the full savanna spectrum ranging from almost pure grassland to closed woodlands on all three continents. All trees and shrubs sampled were of the C3 pathway and all grasses of the C4 pathway with the exception of Echinolaena inflexa (Poir.) Chase, a common C3 grass of the Brazilian cerrado. By comparing the carbon isotopic compositions of the plant and carbon pools, a simple model relating soil delta 13C to the relative abundances of trees + shrubs (woody plants) and grasses was developed. The model suggests that the relative proportions of a savanna ecosystem's total foliar projected cover attributable to grasses versus woody plants is a simple and reliable index of the relative contributions of grasses and woody plants to savanna net productivity. Model calibrations against woody tree canopy cover made it possible to estimate the proportion of savanna productivity in the major regions of the world attributable to trees + shrubs and grasses from ground-based observational maps of savanna woodiness. Overall, it was estimated that 59% of the net primary productivity (Np) of tropical savannas is attributable to C4 grasses, but that this proportion varies significantly within and between regions. The C4 grasses make their greatest relative contribution to savanna Np in the Neotropics, whereas in African regions, a greater proportion of savanna Np is attributable to woody plants. The relative contribution of C4 grasses in Australian savannas is intermediate between those in the Neotropics and Africa. These differences can be broadly ascribed to large scale differences in soil fertility and rainfall. PMID:18171668

  13. Relationship between tourism development and vegetated landscapes in Luya Mountain Nature Reserve, Shanxi, China.

    PubMed

    Cheng, Zhan-Hong; Zhang, Jin-Tun

    2005-09-01

    The relationship between tourism development and vegetated landscapes is analyzed for the Luya Mountain Nature Reserve (LMNR), Shanxi, China, in this study. Indices such as Sensitive Level (SL), Landscape Importance Value (LIV), information index of biodiversity (H'), Shade-tolerant Species Proportion (SSP), and Tourism Influencing Index (TII) are used to characterize vegetated landscapes, the impact of tourism, and their relationship. Their relationship is studied by Two-Way Indicator Species Analysis (TWINSPAN) and Detrended Correspondence Analysis (DCA). TWINSPAN gives correct and rapid partition to the classification, and DCA ordination shows the changing tendency of all vegetation types based on tourism development. These results reflect the ecological relationship between tourism development and vegetated landscapes. In Luya Mountain Nature Reserve, most plant communities are in good or medium condition, which shows that these vegetated landscapes can support more tourism. However, the occurrence of the bad condition shows that there is a severe contradiction between tourism development and vegetated landscapes.

  14. Spatial patterns in the effects of fire on savanna vegetation three-dimensional structure.

    PubMed

    Levick, Shaun R; Asner, Gregory P; Smit, Izak P J

    2012-12-01

    Spatial variability in the effects of fire on savanna vegetation structure is seldom considered in ecology, despite the inherent heterogeneity of savanna landscapes. Much has been learned about the effects of fire on vegetation structure from long-term field experiments, but these are often of limited spatial extent and do not encompass different hillslope catena elements. We mapped vegetation three-dimensional (3-D) structure over 21 000 ha in nine savanna landscapes (six on granite, three on basalt), each with contrasting long-term fire histories (higher and lower fire frequency), as defined from a combination of satellite imagery and 67 years of management records. Higher fire frequency areas contained less woody canopy cover than their lower fire frequency counterparts in all landscapes, and woody cover reduction increased linearly with increasing difference in fire frequency (r2 = 0.58, P = 0.004). Vegetation height displayed a more heterogeneous response to difference in fire frequency, with taller canopies present in the higher fire frequency areas of the wetter sites. Vegetation 3-D structural differences between areas of higher and lower fire frequency differed between geological substrates and varied spatially across hillslopes. Fire had the greatest relative impact on vegetation structure on nutrient-rich basalt substrates, and it imparted different structural responses upon vegetation in upland, midslope, and lowland topographic positions. These results highlight the complexity of fire vegetation relationships in savanna systems, and they suggest that underlying landscape heterogeneity needs more explicit incorporation into fire management policies. PMID:23387113

  15. Spatial patterns in the effects of fire on savanna vegetation three-dimensional structure.

    PubMed

    Levick, Shaun R; Asner, Gregory P; Smit, Izak P J

    2012-12-01

    Spatial variability in the effects of fire on savanna vegetation structure is seldom considered in ecology, despite the inherent heterogeneity of savanna landscapes. Much has been learned about the effects of fire on vegetation structure from long-term field experiments, but these are often of limited spatial extent and do not encompass different hillslope catena elements. We mapped vegetation three-dimensional (3-D) structure over 21 000 ha in nine savanna landscapes (six on granite, three on basalt), each with contrasting long-term fire histories (higher and lower fire frequency), as defined from a combination of satellite imagery and 67 years of management records. Higher fire frequency areas contained less woody canopy cover than their lower fire frequency counterparts in all landscapes, and woody cover reduction increased linearly with increasing difference in fire frequency (r2 = 0.58, P = 0.004). Vegetation height displayed a more heterogeneous response to difference in fire frequency, with taller canopies present in the higher fire frequency areas of the wetter sites. Vegetation 3-D structural differences between areas of higher and lower fire frequency differed between geological substrates and varied spatially across hillslopes. Fire had the greatest relative impact on vegetation structure on nutrient-rich basalt substrates, and it imparted different structural responses upon vegetation in upland, midslope, and lowland topographic positions. These results highlight the complexity of fire vegetation relationships in savanna systems, and they suggest that underlying landscape heterogeneity needs more explicit incorporation into fire management policies.

  16. Hydraulic Lift As a Determinant of Tree-Grass Coexistence on Savannas

    NASA Astrophysics Data System (ADS)

    Yu, K.; D'Odorico, P.

    2014-12-01

    The coexistence of woody plants and grasses in savannas is determined by a complex set of interacting factors, including resource availability and disturbance. Existing theories explaining coexistence focus on competitive relations or disturbances preventing the system from attaining a state with complete grass or tree dominance. The effect of hydraulic lift on interactions between woody plants and grasses and the dynamics of savanna ecosystems remains poorly understood. Here, we develop a mechanistic model to investigate the role of hydraulic lift on the stability of savannas. The model accounts both for competition for soil water in the shallow soil layer and fire-induced disturbance. We find that hydraulic lift expands the parameter range in which savannas are stable at the expense of woodlands. Our study shows that hydraulic lift can be an important mechanism responsible for coexistence of woody plants and grasses in savannas.

  17. Landscape development in the context of soil distribution in Jordan

    NASA Astrophysics Data System (ADS)

    Lucke, Bernhard

    2016-04-01

    Processes of landscape change can be assessed by studying the distribution of soil types and their connection to climate, the geology, and land use. In this context, even in areas where no virgin soils are available, paleosols pre-dating the introduction of agriculture can be utilized for estimating potential soil development without human impact. Soil distribution in Jordan follows closely the climate and topography: specific soil orders can be found within the dry and hot subtropical, subhumid-semiarid, semiarid-arid, and arid regions. The pattern of soil and paleosol distribution in Jordan points to an important role of the geology (bedrock and relief), and of climate in their formation, both locally such as in the vicinity of the ancient site of Abila, and regionally in the whole country. In contrast, the impact of land use appears relatively limited: overall erosion has been estimated not to exceed the expected geological rate, and Jordan is considered to be in the stable state of completed geologic erosion. This is further supported by strongly varying soil properties and archaeological material on agricultural fields, which suggests that overall erosion processes during historical periods were limited. The presence of a quite uniform 4 m thick loess cover around the site of Umm el-Jimal in north-east Jordan suggests that aeolian deposits are probably the by far dominating parent material of current soils in northern Jordan. In this context, an apparent division of some soil profiles into subsoil and topsoil could correspond to dominant in-situ soil formation out of bedrock weathering at the bottom, while the upper part of the profiles could correspond to aeolian dust as main parent material. A stone line or lithological discontinuity separating these two parts of the profile might refer to a major erosion event. If true, this could indicate that current soils in Jordan might represent a mixture of at least two phases of soil development with probably

  18. The ongoing development of a pragmatic and adaptive fire management policy in a large African savanna protected area.

    PubMed

    van Wilgen, Brian W; Govender, Navashni; Smit, Izak P J; MacFadyen, Sandra

    2014-01-01

    This paper describes recent changes to the fire management policy of the 1.9 million ha Kruger National Park in South Africa. It provides a real-life example of adaptive learning in an environment where understanding is incomplete, but where management nonetheless has to proceed. The previous policy called for the application of fire to meet burnt area targets that were set for administrative subdivisions, and that were assessed at the scale of the entire park. This was problematic because the park is large and heterogeneous, and because sound ecological motivations that could link burning prescriptions to ecological objectives were missing. The new policy divides the park into five fire management zones on the basis of differences in mean annual rainfall, historic fire return periods, and geology. In addition, it proposes fire management actions designed to achieve specified ecological objectives in each zone, and includes fire-regime related thresholds and associated ecological outcomes against which to assess the effectiveness of management. The new policy is an improvement over previous iterations, but several challenges remain. Most important among these would be to continually improve the understanding of the effects of fire, and to develop frameworks for assessing the impacts of fire together with other ecosystem drivers that interact strongly with fire to influence the attainment of ecological objectives.

  19. Recent developments in computer modeling add ecological realism to landscape genetics

    EPA Science Inventory

    Background / Question / Methods A factor limiting the rate of progress in landscape genetics has been the shortage of spatial models capable of linking life history attributes such as dispersal behavior to complex dynamic landscape features. The recent development of new models...

  20. The SLMTA programme: Transforming the laboratory landscape in developing countries

    PubMed Central

    Yao, Katy; Maruta, Talkmore; Luman, Elizabeth T.; Nkengasong, John N.

    2015-01-01

    Background Efficient and reliable laboratory services are essential to effective and well-functioning health systems. Laboratory managers play a critical role in ensuring the quality and timeliness of these services. However, few laboratory management programmes focus on the competencies required for the daily operations of a laboratory in resource-limited settings. This report provides a detailed description of an innovative laboratory management training tool called Strengthening Laboratory Management Toward Accreditation (SLMTA) and highlights some challenges, achievements and lessons learned during the first five years of implementation (2009–2013) in developing countries. Programme SLMTA is a competency-based programme that uses a series of short courses and work-based learning projects to effect immediate and measurable laboratory improvement, while empowering laboratory managers to implement practical quality management systems to ensure better patient care. A SLMTA training programme spans from 12 to 18 months; after each workshop, participants implement improvement projects supported by regular supervisory visits or on-site mentoring. In order to assess strengths, weaknesses and progress made by the laboratory, audits are conducted using the World Health Organization’s Regional Office for Africa (WHO AFRO) Stepwise Laboratory Quality Improvement Process Towards Accreditation (SLIPTA) checklist, which is based on International Organization for Standardization (ISO) 15189 requirements. These internal audits are conducted at the beginning and end of the SLMTA training programme. Conclusion Within five years, SLMTA had been implemented in 617 laboratories in 47 countries, transforming the laboratory landscape in developing countries. To our knowledge, SLMTA is the first programme that makes an explicit connection between the performance of specific management behaviours and routines and ISO 15189 requirements. Because of this close relationship, SLMTA is

  1. Prospects of photon counting lidar for savanna ecosystem structural studies

    NASA Astrophysics Data System (ADS)

    Gwenzi, D.; Lefsky, M. A.

    2014-11-01

    Discrete return and waveform lidar have demonstrated a capability to measure vegetation height and the associated structural attributes such as aboveground biomass and carbon storage. Since discrete return lidar (DRL) is mainly suitable for small scale studies and the only existing spaceborne lidar sensor (ICESat-GLAS) has been decommissioned, the current question is what the future holds in terms of large scale lidar remote sensing studies. The earliest planned future spaceborne lidar mission is ICESat-2, which will use a photon counting technique. To pre-validate the capability of this mission for studying three dimensional vegetation structure in savannas, we assessed the potential of the measurement approach to estimate canopy height in a typical savanna landscape. We used data from the Multiple Altimeter Beam Experimental Lidar (MABEL), an airborne photon counting lidar sensor developed by NASA Goddard. MABEL fires laser pulses in the green (532 nm) and near infrared (1064 nm) bands at a nominal repetition rate of 10 kHz and records the travel time of individual photons that are reflected back to the sensor. The photons' time of arrival and the instrument's GPS positions and Inertial Measurement Unit (IMU) orientation are used to calculate the distance the light travelled and hence the elevation of the surface below. A few transects flown over the Tejon ranch conservancy in Kern County, California, USA were used for this work. For each transect we extracted the data from one near infrared channel that had the highest number of photons. We segmented each transect into 50 m, 25 m and 10 m long blocks and aggregated the photons in each block into a histogram based on their elevation values. We then used an expansion window algorithm to identify cut off points where the cumulative density of photons from the highest elevation resembles the canopy top and likewise where such cumulative density from the lowest elevation resembles mean ground elevation. These cut off

  2. LORICA - A new model for linking landscape and soil profile evolution: Development and sensitivity analysis

    NASA Astrophysics Data System (ADS)

    Temme, Arnaud J. A. M.; Vanwalleghem, Tom

    2016-05-01

    Soils and landscapes evolve in tandem. Landscape position is a strong determinant of vertical soil development, which has often been formalized in the catena concept. At the same time, soil properties are strong determinants of geomorphic processes such as overland erosion, landsliding and creep. We present a new soilscape evolution model; LORICA, to study these numerous interactions between soil and landscape development. The model is based on the existing landscape evolution model LAPSUS and the soil formation model MILESD. The model includes similar soil formation processes as MILESD, but the main novelties include the consideration of more layers and the dynamic adaption of the number of layers as a function of the soil profile's heterogeneity. New processes in the landscape evolution component include a negative feedback of vegetation and armouring and particle size selectivity of the erosion-deposition process. In order to quantify these different interactions, we present a full sensitivity analysis of the input parameters. First results show that the model successfully simulates various soil-landscape interactions, leading to outputs where the surface changes in the landscape clearly depend on soil development, and soil changes depend on landscape location. Sensitivity analysis of the model confirms that soil and landscape interact: variables controlling amount and position of fine clay have the largest effect on erosion, and erosion variables control among others the amount of chemical weathering. These results show the importance of particle size distribution, and especially processes controlling the presence of finer clay particles that are easily eroded, both for the resulting landscape form as for the resulting soil profiles. Further research will have to show whether this is specific to the boundary conditions of this study or a general phenomenon.

  3. Development of a catchment/landscape erosion prediction model (MINErosion 4) for post-mining landscapes in Central Queensland, Australia.

    NASA Astrophysics Data System (ADS)

    Khalifa, Ashraf; Yu, Bofu; Ghadiri, Hossain; Carroll, Chris; So, Hwat-Bing

    2010-05-01

    Open-cut coal mining in Central Queensland involves the breaking up of overburden that overlies the coal seams using explosives, followed by removal with draglines which results in the formation of extensive overburden spoil-piles with steep slopes at the angle of repose (approximately 75 % or 37o). These spoil-piles are found in long multiple rows, with heights of up to 60 or 70 m above the original landscapes. They are generally highly saline and dispersive and hence highly erosive. Legislation requires that these spoil-piles be rehabilitated into a stable self sustaining ecosystem with no off-site pollution. The first stage in the rehabilitation of these landscapes is the lowering of slopes to create a landscape that is stable against geotechnical failure and erosion. This is followed by revegetation generally with grasses as pioneer vegetation to further reduce erosion and a mixture of native shrubs and trees. Minimizing erosion and excessive on-site discharges of sediment into the working areas may result in the temporary cessation of mining operation with significant financial consequences, while off site discharges may breach the mining lease conditions. The average cost of rehabilitation is approximately 22,000 per ha. With more than 50,000 ha of such spoil-piles in Queensland at present, the total cost of rehabilitation facing the industry is very high. Most of this comprised the cost of reshaping the landscape, largely associated with the amount of material movement necessary to achieve the desired landscape. Since soil and spoil-piles vary greatly in their erodibilities, a hillslope erosion model MINErosion 3 (this conference) was developed to determine a cost effective combination of slope length, slope gradient and vegetation that will result in acceptable rates of erosion. This model was useful to determine the design parameters for the construction of a suitable post-mining landscape that meets the required erosion criteria. However, the mining

  4. EXTINCTION DEBT OF PROTECTED AREAS IN DEVELOPING LANDSCAPES

    EPA Science Inventory

    To conserve biological diversity, protected-area networks must be based not only upon current species distributions but also the landscape's long-term capacity to support populations. We used spatially-explicit population models requiring detailed habitat and demographic data to ...

  5. Farmers' contribution to landscape services in the Netherlands under different rural development scenarios.

    PubMed

    Pfeifer, Catherine; Sonneveld, Marthijn P W; Stoorvogel, Jetse J

    2012-11-30

    Landscape services represent the benefits human populations derive, directly or indirectly, from (agro-)ecosystem functions at the landscape scale. Many of these services are the result of farmers' decision making to allocate resources to other activities than food production and therefore are the result of farm the adoption of on-farm rural activities. With changing agricultural and rural policies, the future provision of landscape services to fulfill societal demands is not guaranteed. This study aims at mapping the spatial distribution of the adoption of on-farm rural activities under different explorative scenarios. For a Dutch landscape, storylines at the landscape scale were developed by combining global storylines, resulting from the Global Environmental Outlook, with local storylines resulting from key informant interviews. Subsequently these storylines were translated into quantitative scenarios that were implemented into a simulation procedure based on spatially explicit econometric models of farmer's decision making. Results show that further market liberalization leads to a decrease of landscape services in the study area. In our study, only increased cooperation between government, farmers and citizens appears to result in a general increase of all landscape services across the entire landscape.

  6. Implications of the spatial dynamics of fire spread for the bistability of savanna and forest.

    PubMed

    Schertzer, E; Staver, A C; Levin, S A

    2015-01-01

    The role of fire in expanding the global distribution of savanna is well recognized. Empirical observations and modeling suggest that fire spread has a threshold response to fuel-layer continuity, which sets up a positive feedback that maintains savanna-forest bistability. However, modeling has so far failed to examine fire spread as a spatial process that interacts with vegetation. Here, we use simple, well-supported assumptions about fire spread as an infection process and its effects on trees to ask whether spatial dynamics qualitatively change the potential for savanna-forest bistability. We show that the spatial effects of fire spread are the fundamental reason that bistability is possible: because fire spread is an infection process, it exhibits a threshold response to fuel continuity followed by a rapid increase in fire size. Other ecological processes affecting fire spread may also contribute including temporal variability in demography or fire spread. Finally, including the potential for spatial aggregation increases the potential both for savanna-forest bistability and for savanna and forest to coexist in a landscape mosaic.

  7. Abandoned pastoral settlements provide concentrations of resources for savanna birds

    NASA Astrophysics Data System (ADS)

    Söderström, Bo; Reid, Robin S.

    2010-03-01

    Knowledge is poor of how fertilization affects birds in grasslands. We investigated the impact on birds of abandoned pastoral settlements that historically received very high levels of livestock dung. A total of 28 abandoned settlements and 74 landscape controls - in Koyake Group Ranch and Maasai Mara National Reserve in Kenya - were surveyed for birds during the wet and/or dry season. Our results showed that bird species richness and total abundance increased within 200 m of abandoned pastoral settlements, particularly during the dry season when foraging resources on the savanna are limited. The high concentrations of nutrients inside abandoned settlements favoured the abundance of Diptera and Coleoptera, as shown by invertebrate surveys performed during the dry season on a subset of 32 sites. Both total numbers and dry biomass of these two invertebrate orders were higher on abandoned settlements in comparison with the surrounding landscape. We conclude that higher fertilization levels cause a temporal and spatial redistribution of birds on the savanna. Livestock fertilization and bird abundance are probably linked through an increase in abundance of invertebrate food upon which birds feed in an opportunistic fashion.

  8. Landscape development during a glacial cycle: modeling ecosystems from the past into the future.

    PubMed

    Lindborg, Tobias; Brydsten, Lars; Sohlenius, Gustav; Strömgren, Mårten; Andersson, Eva; Löfgren, Anders

    2013-05-01

    Understanding how long-term abiotic and biotic processes are linked at a landscape level is of major interest for analyzing future impact on humans and the environment from present-day societal planning. This article uses results derived from multidisciplinary work at a coastal site in Sweden, with the aim of describing future landscape development. First, based on current and historical data, we identified climate change, shoreline displacement, and accumulation/erosion processes as the main drivers of landscape development. Second, site-specific information was combined with data from the Scandinavian region to build models that describe how the identified processes may affect the site development through time. Finally, the process models were combined to describe a whole interglacial period. With this article, we show how the landscape and ecosystem boundaries are affected by changing permafrost conditions, peat formation, sedimentation, human land use, and shoreline displacement.

  9. Landscape development during a glacial cycle: modeling ecosystems from the past into the future.

    PubMed

    Lindborg, Tobias; Brydsten, Lars; Sohlenius, Gustav; Strömgren, Mårten; Andersson, Eva; Löfgren, Anders

    2013-05-01

    Understanding how long-term abiotic and biotic processes are linked at a landscape level is of major interest for analyzing future impact on humans and the environment from present-day societal planning. This article uses results derived from multidisciplinary work at a coastal site in Sweden, with the aim of describing future landscape development. First, based on current and historical data, we identified climate change, shoreline displacement, and accumulation/erosion processes as the main drivers of landscape development. Second, site-specific information was combined with data from the Scandinavian region to build models that describe how the identified processes may affect the site development through time. Finally, the process models were combined to describe a whole interglacial period. With this article, we show how the landscape and ecosystem boundaries are affected by changing permafrost conditions, peat formation, sedimentation, human land use, and shoreline displacement. PMID:23619798

  10. Spatial pattern enhances ecosystem functioning in an African savanna.

    PubMed

    Pringle, Robert M; Doak, Daniel F; Brody, Alison K; Jocqué, Rudy; Palmer, Todd M

    2010-05-25

    The finding that regular spatial patterns can emerge in nature from local interactions between organisms has prompted a search for the ecological importance of these patterns. Theoretical models have predicted that patterning may have positive emergent effects on fundamental ecosystem functions, such as productivity. We provide empirical support for this prediction. In dryland ecosystems, termite mounds are often hotspots of plant growth (primary productivity). Using detailed observations and manipulative experiments in an African savanna, we show that these mounds are also local hotspots of animal abundance (secondary and tertiary productivity): insect abundance and biomass decreased with distance from the nearest termite mound, as did the abundance, biomass, and reproductive output of insect-eating predators. Null-model analyses indicated that at the landscape scale, the evenly spaced distribution of termite mounds produced dramatically greater abundance, biomass, and reproductive output of consumers across trophic levels than would be obtained in landscapes with randomly distributed mounds. These emergent properties of spatial pattern arose because the average distance from an arbitrarily chosen point to the nearest feature in a landscape is minimized in landscapes where the features are hyper-dispersed (i.e., uniformly spaced). This suggests that the linkage between patterning and ecosystem functioning will be common to systems spanning the range of human management intensities. The centrality of spatial pattern to system-wide biomass accumulation underscores the need to conserve pattern-generating organisms and mechanisms, and to incorporate landscape patterning in efforts to restore degraded habitats and maximize the delivery of ecosystem services.

  11. An overview of nitrogen cycling in a semiarid savanna: some implications for management and conservation in a large African park.

    PubMed

    Coetsee, Corli; Jacobs, Shayne; Govender, Navashni

    2012-02-01

    Nitrogen (N) is a major control on primary productivity and hence on the productivity and diversity of secondary producers and consumers. As such, ecosystem structure and function cannot be understood without a comprehensive understanding of N cycling and dynamics. This overview describes the factors that govern N distribution and dynamics and the consequences that variable N dynamics have for structure, function and thresholds of potential concern (TPCs) for management of a semiarid southern African savanna. We focus on the Kruger National Park (KNP), a relatively intact savanna, noted for its wide array of animal and plant species and a prized tourist destination. KNP's large size ensures integrity of most ecosystem processes and much can be learned about drivers of ecosystem structure and function using this park as a baseline. Our overview shows that large scale variability in substrates exists, but do not necessarily have predictable consequences for N cycling. The impact of major drivers such as fire is complex; at a landscape scale little differences in stocks and cycling were found, though at a smaller scale changes in woody cover can lead to concomitant changes in total N. Contrasting impacts of browsers and grazers on N turnover has been recorded. Due to the complexity of this ecosystem, we conclude that it will be complicated to draw up TPCs for most transformations and pools involved with the N cycle. However, we highlight in which cases the development of TPCs will be possible. PMID:22057696

  12. An Overview of Nitrogen Cycling in a Semiarid Savanna: Some Implications for Management and Conservation in a Large African Park

    NASA Astrophysics Data System (ADS)

    Coetsee, Corli; Jacobs, Shayne; Govender, Navashni

    2012-02-01

    Nitrogen (N) is a major control on primary productivity and hence on the productivity and diversity of secondary producers and consumers. As such, ecosystem structure and function cannot be understood without a comprehensive understanding of N cycling and dynamics. This overview describes the factors that govern N distribution and dynamics and the consequences that variable N dynamics have for structure, function and thresholds of potential concern (TPCs) for management of a semiarid southern African savanna. We focus on the Kruger National Park (KNP), a relatively intact savanna, noted for its wide array of animal and plant species and a prized tourist destination. KNP's large size ensures integrity of most ecosystem processes and much can be learned about drivers of ecosystem structure and function using this park as a baseline. Our overview shows that large scale variability in substrates exists, but do not necessarily have predictable consequences for N cycling. The impact of major drivers such as fire is complex; at a landscape scale little differences in stocks and cycling were found, though at a smaller scale changes in woody cover can lead to concomitant changes in total N. Contrasting impacts of browsers and grazers on N turnover has been recorded. Due to the complexity of this ecosystem, we conclude that it will be complicated to draw up TPCs for most transformations and pools involved with the N cycle. However, we highlight in which cases the development of TPCs will be possible.

  13. An overview of nitrogen cycling in a semiarid savanna: some implications for management and conservation in a large African park.

    PubMed

    Coetsee, Corli; Jacobs, Shayne; Govender, Navashni

    2012-02-01

    Nitrogen (N) is a major control on primary productivity and hence on the productivity and diversity of secondary producers and consumers. As such, ecosystem structure and function cannot be understood without a comprehensive understanding of N cycling and dynamics. This overview describes the factors that govern N distribution and dynamics and the consequences that variable N dynamics have for structure, function and thresholds of potential concern (TPCs) for management of a semiarid southern African savanna. We focus on the Kruger National Park (KNP), a relatively intact savanna, noted for its wide array of animal and plant species and a prized tourist destination. KNP's large size ensures integrity of most ecosystem processes and much can be learned about drivers of ecosystem structure and function using this park as a baseline. Our overview shows that large scale variability in substrates exists, but do not necessarily have predictable consequences for N cycling. The impact of major drivers such as fire is complex; at a landscape scale little differences in stocks and cycling were found, though at a smaller scale changes in woody cover can lead to concomitant changes in total N. Contrasting impacts of browsers and grazers on N turnover has been recorded. Due to the complexity of this ecosystem, we conclude that it will be complicated to draw up TPCs for most transformations and pools involved with the N cycle. However, we highlight in which cases the development of TPCs will be possible.

  14. Plot-level aboveground woody biomass modeling using canopy height and auxiliary remote sensing data in a heterogeneous savanna

    NASA Astrophysics Data System (ADS)

    Gwenzi, David; Lefsky, Michael Andrew

    2016-01-01

    Remote sensing studies aiming at assessing woody biomass have demonstrated a strong relationship between canopy height and plot-level aboveground biomass, but most of these studies focused on closed canopy forests. To date, a few studies have examined the strength and reliability of this relationship using large footprint lidar in savannas. Furthermore, there have been few studies of appropriate methods for the comparison of models that relate aboveground biomass to canopy height metrics without consideration of variation in species composition (generic models) to models developed for individual species composition or vegetation types. We developed generic models using the classical least-squares regression modeling approach to relate selected canopy height metrics to aboveground woody biomass in a savanna landscape. Hierarchical Bayesian analysis (HBA) was then used to explore the implications of using generic or composition-specific models. Our study used the estimates of aboveground biomass from field data, canopy height estimates from airborne discrete return lidar, and a proxy for canopy cover (the Normalized Difference Vegetation Index) from Landsat 5 Thematic Mapper data, collected from the oak savannas of Tejon Ranch Conservancy in Kern County, California. Models were developed and analyzed using estimates of canopy height and aboveground biomass calculated at the level of 50-m diameter plots, comparable with footprint diameter of existing large footprint spaceborne lidar data. The two generic models that incorporated canopy cover proxies performed better than one model that did not use canopy cover information. From the HBA, we found out that for all models both the intercept and slope had interspecific variability. The valley oak dominated plots consistently had higher slopes and intercepts, whereas the plots dominated by blue oaks had the lowest. However, the intercept and slope values of the composition-specific models did not differ much from the

  15. Forecasting spatial plant dynamics under future climate change in a semiarid savanna ecosystem with complex topography

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Fatichi, S.; Istanbulluoglu, E.; Vivoni, E. R.

    2011-12-01

    The space and time dynamics of savanna ecosystems in semiarid regions is tightly related to fluctuations and changes in the climate, and the competition strategies of individual plants for resources. In most parts of the southwest U.S., various General Circulation Models (GCMs) predict general warming trends with reduced annual precipitation amounts, and increased frequency of extreme droughts and wet periods in the 21st century. Despite the potential risks posed by climate change on vegetation patterns and hydrology, our ability to predict such changes at the catchment and regional scales is limited. In this study, we used a recently developed spatially explicit Cellular Automata Tree-Grass-Shrub Simulator (CATGraSS) to investigate the impacts of climate change on plant dynamics in a semiarid catchment (>3km2) located in the Sevilleta National Wildlife Refuge (SNWR) in central New Mexico, USA. In the catchment north-facing slopes are characterized by a juniper-grass savanna, and south-facing slopes by creosote bush and grass species. Initialized by LIDAR-derived tree locations and simulated grass and shrub patterns obtained from model calibration, CATGraSS is forced by a weather generator, AWE-GEN, used to downscale an ensemble of eight different GCM outputs at the study basin, producing multiple stochastic realizations of a transient climate scenario for the next hundred years. The ensemble simulations are used to examine the uncertainty in vegetation response and develop probabilistic plant distribution maps in relation to landscape morphology. This study highlights the importance of understanding local scale plant-to-plant interactions and the role of climate variability in determining climate change impacts on vegetation dynamics at varying spatial scales.

  16. Nesting success of grassland and savanna birds on reclaimed surface coal mines of the midwestern United States

    SciTech Connect

    Galligan, E.W.; DeVault, T.L.; Lima, S.L.

    2006-12-15

    Reclaimed surface coal mines in southwestern Indiana support many grassland and shrub/savanna bird species of conservation concern. We examined the nesting success of birds on these reclaimed mines to assess whether such 'unnatural' places represent productive breeding habitats for such species. We established eight study sites on two large, grassland-dominated mines in southwestern Indiana and classified them into three categories (open grassland, shrub/savanna, and a mixture of grassland and shrub/savanna) based on broad vegetation and landscape characteristics. During the 1999 and 2000 breeding seasons, we found and monitored 911 nests of 31 species. Daily nest survival for the most commonly monitored grassland species ranged from 0.903 (Dickcissel, Spiza americana) to 0.961 (Grasshopper Sparrow, Ammodramus savannarum). Daily survival estimates for the dominant shrub/savanna nesting species ranged from 0.932 (Brown Thrasher, Toxostoma rufum) to 0.982 (Willow Flycatcher, Empidonax traillii). Vegetation and landscape effects on nesting success were minimal, and only Eastern Meadowlarks (Sturnella magna) showed a clear time-of-season effect, with greater nesting success in the first half of the breeding season. Rates of Brown-headed Cowbird (Molothrus ater) parasitism were only 2.1% for grassland species and 12.0% for shrub/savanna species. The nesting success of birds on reclaimed mine sites was comparable to that in other habitats, indicating that reclaimed habitats on surface mines do not necessarily represent reproductive traps for birds.

  17. Carbon, Water, and Energy Dynamics in a Savanna Mosaic: Results From an African Field Campaign

    NASA Astrophysics Data System (ADS)

    Williams, C. A.; Albertson, J. D.

    2002-12-01

    Savanna ecosystems cover a large fraction of the terrestrial landscape with a shifting mosaic of vegetation that is poorly understood. Vegetation dynamics in savannas are believed to be triggered by variation in climate forcing with potential local and regional scale feedbacks on climate and with nonlinear behavior, such as self-organization. Recent debate has brought attention to uncertainty regarding the role of savannas in global carbon and water cycles, identifying the need for data that can address the coupled water and carbon dynamics of these sensitive ecosystems. We report results from a 30-day field campaign conducted in southern Africa near Ghanzi, Botswana along the Kalahari Transect. This water-limited site is ideal for studies of soil and plant water relations because high spatial and temporal variability in rainfall has direct effects on vegetation function, extent, and composition. We characterized the functional response of tree/grass/bare soil mosaics during a prolonged drydown following a large rain event (85 mm) at the end of the 2002 wet season. Net radiation, sensible, latent and soil heat fluxes, carbon dioxide exchange, soil moisture, soil temperature, and vegetation temperatures were measured at two sites, one dominated by woody vegetation (Acacia and Terminalia) and the other composed of native grasses, shrubs, and bare soil. We characterized the vegetation structure within the footprints of both towers with measurements of leaf area, fractional vegetation cover, and profiles of aboveground and belowground biomass. Additionally, leaf-level gas exchange measurements were conducted on dominant species. Soil moisture decayed from a peak of 0.28 after the storm to 0.05, measured 5 cm below the soil surface. The drydown resulted in a continual increase in the daytime Bowen ratio, a decrease of leaf-level evapotranspiration, and reduced net ecosystem exchange of CO2. Biophysical differences between C3 trees and C4 grasses were evident from vapor

  18. Tropical Forests, Savannas and Grasslands: Bridging the Knowledge Gap Between Ecology and Dynamic Global Vegetation Models

    NASA Astrophysics Data System (ADS)

    Baudena, M.; Dekker, S. C.; van Bodegom, P. M.; Cuesta, B.; Higgins, S. I.; Lehsten, V.; Reick, C. H.; Rietkerk, M.; Scheiter, S.; Yin, Z.; Zavala, M. A.; Brovkin, V.

    2014-12-01

    Due to global climate change, tropical forest, savanna, and grassland biomes, and the transitions between them, are expected to undergo major changes in the future. Dynamic Global Vegetation Models (DGVMs) are largely used to understand vegetation dynamics under present climate, and to predict its changes under future conditions. However, several DGVMs display high uncertainty in predicting vegetation in tropical areas. Here we present the results of a comparative analysis of three different DGVMs (JSBACH, LPJ-GUESS-SPITFIRE and aDGVM) with regard to their different representations of the ecological mechanisms and feedbacks that determine the forest, savanna and grassland biomes, in an attempt to bridge the knowledge gap between ecology and global modelling. We compared model outcomes to observed tree cover along a mean annual precipitation gradient in Africa. Through these comparisons, and by drawing on the large number of recent studies that have delivered new insights into the ecology of tropical ecosystems in general, and of savannas in particular, we identify two main mechanisms that need an improved representation in the DGVMs. The first mechanism encompasses water limitation to tree growth, and tree-grass competition for water, which are key factors in determining savanna occurrence in arid and semi-arid areas. The second is a grass-fire feedback, which maintains both forest and savannas in mesic areas. Grasses constitute the majority of the fuel load, and at the same time benefit from the openness of the landscape after fires, since they recover faster than trees. Additionally, these two mechanisms are better represented when the models also include tree life stages (adults and seedlings), and distinguish between fire-prone and shade-tolerant savanna trees, and fire-resistant and shade-intolerant forest trees. Including these basic elements could improve the predictive ability of the DGVMs, not only under current climate conditions but also and especially

  19. Forests, savannas, and grasslands: bridging the knowledge gap between ecology and Dynamic Global Vegetation Models

    NASA Astrophysics Data System (ADS)

    Baudena, M.; Dekker, S. C.; van Bodegom, P. M.; Cuesta, B.; Higgins, S. I.; Lehsten, V.; Reick, C. H.; Rietkerk, M.; Scheiter, S.; Yin, Z.; Zavala, M. A.; Brovkin, V.

    2015-03-01

    The forest, savanna, and grassland biomes, and the transitions between them, are expected to undergo major changes in the future due to global climate change. Dynamic global vegetation models (DGVMs) are very useful for understanding vegetation dynamics under the present climate, and for predicting its changes under future conditions. However, several DGVMs display high uncertainty in predicting vegetation in tropical areas. Here we perform a comparative analysis of three different DGVMs (JSBACH, LPJ-GUESS-SPITFIRE and aDGVM) with regard to their representation of the ecological mechanisms and feedbacks that determine the forest, savanna, and grassland biomes, in an attempt to bridge the knowledge gap between ecology and global modeling. The outcomes of the models, which include different mechanisms, are compared to observed tree cover along a mean annual precipitation gradient in Africa. By drawing on the large number of recent studies that have delivered new insights into the ecology of tropical ecosystems in general, and of savannas in particular, we identify two main mechanisms that need improved representation in the examined DGVMs. The first mechanism includes water limitation to tree growth, and tree-grass competition for water, which are key factors in determining savanna presence in arid and semi-arid areas. The second is a grass-fire feedback, which maintains both forest and savanna presence in mesic areas. Grasses constitute the majority of the fuel load, and at the same time benefit from the openness of the landscape after fires, since they recover faster than trees. Additionally, these two mechanisms are better represented when the models also include tree life stages (adults and seedlings), and distinguish between fire-prone and shade-tolerant forest trees, and fire-resistant and shade-intolerant savanna trees. Including these basic elements could improve the predictive ability of the DGVMs, not only under current climate conditions but also and

  20. Mapping Brazilian savanna vegetation gradients with Landsat time series

    NASA Astrophysics Data System (ADS)

    Schwieder, Marcel; Leitão, Pedro J.; da Cunha Bustamante, Mercedes Maria; Ferreira, Laerte Guimarães; Rabe, Andreas; Hostert, Patrick

    2016-10-01

    Global change has tremendous impacts on savanna systems around the world. Processes related to climate change or agricultural expansion threaten the ecosystem's state, function and the services it provides. A prominent example is the Brazilian Cerrado that has an extent of around 2 million km2 and features high biodiversity with many endemic species. It is characterized by landscape patterns from open grasslands to dense forests, defining a heterogeneous gradient in vegetation structure throughout the biome. While it is undisputed that the Cerrado provides a multitude of valuable ecosystem services, it is exposed to changes, e.g. through large scale land conversions or climatic changes. Monitoring of the Cerrado is thus urgently needed to assess the state of the system as well as to analyze and further understand ecosystem responses and adaptations to ongoing changes. Therefore we explored the potential of dense Landsat time series to derive phenological information for mapping vegetation gradients in the Cerrado. Frequent data gaps, e.g. due to cloud contamination, impose a serious challenge for such time series analyses. We synthetically filled data gaps based on Radial Basis Function convolution filters to derive continuous pixel-wise temporal profiles capable of representing Land Surface Phenology (LSP). Derived phenological parameters revealed differences in the seasonal cycle between the main Cerrado physiognomies and could thus be used to calibrate a Support Vector Classification model to map their spatial distribution. Our results show that it is possible to map the main spatial patterns of the observed physiognomies based on their phenological differences, whereat inaccuracies occurred especially between similar classes and data-scarce areas. The outcome emphasizes the need for remote sensing based time series analyses at fine scales. Mapping heterogeneous ecosystems such as savannas requires spatial detail, as well as the ability to derive important

  1. Using remote sensing and biogeographic modeling to understand the oak savannas of the Sheyenne National Grassland, North Dakota, USA

    NASA Astrophysics Data System (ADS)

    SigdelPhuyal, Mandira

    Oak savannas are valuable and complex ecosystems that provide multiple ecosystem goods and services, including grazing for livestock, watershed regulation, and recreation. These ecosystems of the woodland-prairie ecoregion of the Midwestern United States are, however, in danger of disappearing. The Sheyenne National Grassland, North Dakota, a protected Prairie grassland-savanna, is a representative of such rare habitats, where oak savanna is found at the landscape scale. In this research, I map the distribution patterns of oak savanna in the Sheyenne using a combination of remote sensing and geospatial datasets, including landscape topography, soils, and fire disturbance. Further, I interpret the performance of a suite of advanced Species Distribution Modeling approaches including Maximum Entropy, Random Forest, Generalized Boosted Model, and Classification Tree to analyze the primary environmental and management factors influencing oak distributions at landscape scales. Woody canopy cover was estimated with high classification accuracy (80-95%) for two study areas of the Sheyenne National Grassland. Among the four species distribution modeling approaches tested, the Random Forest (RF) approach provided the best predictive model. RF model parameters indicate that oak trees favor gently sloping locations, on well-drained upland and sandy soils, with north-facing aspect. While no direct data on water relationships were possible in this research, the importance of the topographic and soil variables in the SDM presumably reflect oak preference for locations and soils that are not prone to water saturation, with milder summer temperatures (i.e. northern aspects), providing conditions suitable for seedling establishment and growth. This research increases our understanding of the biogeography of Midwestern tall-grass oak savannas and provides a decision-support tool for oak savanna management.

  2. Hydraulic lift as a determinant of tree-grass coexistence on savannas.

    PubMed

    Yu, Kailiang; D'Odorico, Paolo

    2015-09-01

    The coexistence of woody plants and grasses in savannas is determined by a complex set of interacting factors that determine access to resources and demographic dynamics, under the control of external drivers and vegetation feedbacks with the physical environment. Existing theories explain coexistence mainly as an effect of competitive relations and/or disturbances. However, theoretical studies on the way facilitative interactions resulting from hydraulic lift affect tree-grass coexistence and the range of environmental conditions in which savannas are stable are still lacking. We investigated the role of hydraulic lift in the stability of tree-grass coexistence in savannas. To that end, we developed a new mechanistic model that accounts for both competition for soil water in the shallow soil and fire-induced disturbance. We found that hydraulic lift favors grasses, which scavenge the water lifted by woody plants. Thus, hydraulic lift expands (at the expenses of woodlands) the range of environmental conditions in which savannas are stable. These results indicate that hydraulic lift can be an important mechanism responsible for the coexistence of woody plants and grasses in savannas. Grass facilitation by trees through the process of hydraulic lift could allow savannas to persist stably in mesic regions that would otherwise exhibit a forest cover. PMID:25925655

  3. Hydraulic lift as a determinant of tree-grass coexistence on savannas.

    PubMed

    Yu, Kailiang; D'Odorico, Paolo

    2015-09-01

    The coexistence of woody plants and grasses in savannas is determined by a complex set of interacting factors that determine access to resources and demographic dynamics, under the control of external drivers and vegetation feedbacks with the physical environment. Existing theories explain coexistence mainly as an effect of competitive relations and/or disturbances. However, theoretical studies on the way facilitative interactions resulting from hydraulic lift affect tree-grass coexistence and the range of environmental conditions in which savannas are stable are still lacking. We investigated the role of hydraulic lift in the stability of tree-grass coexistence in savannas. To that end, we developed a new mechanistic model that accounts for both competition for soil water in the shallow soil and fire-induced disturbance. We found that hydraulic lift favors grasses, which scavenge the water lifted by woody plants. Thus, hydraulic lift expands (at the expenses of woodlands) the range of environmental conditions in which savannas are stable. These results indicate that hydraulic lift can be an important mechanism responsible for the coexistence of woody plants and grasses in savannas. Grass facilitation by trees through the process of hydraulic lift could allow savannas to persist stably in mesic regions that would otherwise exhibit a forest cover.

  4. Overdeepening development in a glacial landscape evolution model with quarrying

    NASA Astrophysics Data System (ADS)

    Ugelvig, S. V.; Egholm, D. L.; Brædstrup, C. F.; Iverson, N. R.

    2013-12-01

    In glacial landscape evolution models, subglacial erosion rates are often related to basal sliding or ice discharge by a power-law. This relation can be justified when considering bed abrasion, where rock debris transported in the basal ice drives erosion. However, the relation is not well supported when considering models for quarrying of rock blocks from the bed. Field observations indicate that the principal mechanism of glacial erosion is quarrying, which emphasize the importance of a better way of implementing erosion by quarrying in glacial landscape evolution models. Iverson (2012) introduced a new model for subglacial erosion by quarrying that operates from the theory of adhesive wear. The model is based on the fact that cavities, with a high level of bedrock differential stress, form in the lee of bed obstacles when the sliding velocity is too high to allow for the ice to creep around the obstacles. The erosion rate is quantified by considering the likelihood of rock fracturing on topographic bumps. The model includes a statistical treatment of the bedrock weakness, which is neglected in previous quarrying models. Sliding rate, effective pressure, and average bedslope are the primary factors influencing the erosion rate of this new quarrying model [Iverson, 2012]. We have implemented the quarrying model in a depth-integrated higher-order ice-sheet model [Egholm et al. 2011], coupled to a model for glacial hydrology. In order to also include the effects of cavitation on the subglacial sliding rate, we use a sliding law proposed by Schoof (2005), which includes an upper limit for the stress that can be supported at the bed. Computational experiments show that the combined influence of pressure, sliding rate and bed slope leads to realistically looking landforms such as U-shaped valleys, cirques, hanging valleys and overdeepenings. The influence of the effective pressure leads naturally to overdeepenings. However, in contrast to previously used erosion models

  5. Developing a simplified river landscape assessment model: examples from the Chungkang and Touchien rivers, Taiwan.

    PubMed

    Chen, Shiang-Yuarn; Lin, Jen-Yang

    2007-04-01

    Currently, river landscape evaluations cannot be conducted by the general public, due to their lack of professional training. However, consulting professionals is time consuming and costly. The research conducted addresses both problems by (1) developing suitable criteria for assessing river environments, and (2) formulating a strategy for using the proposed criteria, thereby creating an effective method for river management by non-professionals. This research was carried out, in accordance with Visual Resource Management theory, at 12 survey sites along the ChungKang River. The landscape quality sequences acquired were then evaluated using a revised and simplified assessment model. The same process was repeated on the Touchien River to verify its feasibility. This research developed both specific criteria as well a method for evaluating river landscapes, which can be employed by non-professional river project managers. Ultimately, the aim of this research is to develop and promote sustainable river resource management.

  6. Effects of exurban development on trophic interactions in a desert landscape

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Context Mechanisms of ecosystem change in urbanizing landscapes are poorly understood, especially in exurban areas featuring residential or commercial development set in a matrix of modified and natural vegetation. We asked how development altered trophic interactions and ecosystem processes in the ...

  7. Design-with-Nature for Multifunctional Landscapes: Environmental Benefits and Social Barriers in Community Development

    PubMed Central

    Yang, Bo; Li, Ming-Han; Li, Shujuan

    2013-01-01

    Since the early 1970s, Ian McHarg’s design-with-nature concept has been inspiring landscape architects, community and regional planners, and liked-minded professionals to create designs that take advantage of ecosystem services and promote environmental and public health. This study bridges the gap in the literature that has resulted from a lack of empirical examinations on the multiple performance benefits derived through design-with-nature and the under-investigated social aspect emanated from McHarg’s Ecological Determinism design approach. The Woodlands, TX, USA, an ecologically designed community development under McHarg’s approach, is compared with two adjacent communities that follow the conventional design approach. Using national environmental databases and multiple-year residents’ survey information, this study assesses three landscape performance metrics of McHarg’s approach: stormwater runoff, urban heat island effect, and social acceptance. Geographic Information Systems (GIS) was used to assess the development extent and land surface temperature distribution. Results show that McHarg’s approach demonstrates benefits in reducing runoff and urban heat island effect, whereas it confronts challenges with the general acceptance of manicured landscapes and thus results in a low safety perception level when residents interact with naturally designed landscapes. The authors argue that design-with-nature warrants multifunctionality because of its intrinsic interdisciplinary approach. Moreover, education and dissemination of successful examples can achieve a greater level of awareness among the public and further promote multifunctional design for landscape sustainability. PMID:24169408

  8. Design-with-nature for multifunctional landscapes: environmental benefits and social barriers in community development.

    PubMed

    Yang, Bo; Li, Ming-Han; Li, Shujuan

    2013-11-01

    Since the early 1970s, Ian McHarg's design-with-nature concept has been inspiring landscape architects, community and regional planners, and liked-minded professionals to create designs that take advantage of ecosystem services and promote environmental and public health. This study bridges the gap in the literature that has resulted from a lack of empirical examinations on the multiple performance benefits derived through design-with-nature and the under-investigated social aspect emanated from McHarg's Ecological Determinism design approach. The Woodlands, TX, USA, an ecologically designed community development under McHarg's approach, is compared with two adjacent communities that follow the conventional design approach. Using national environmental databases and multiple-year residents' survey information, this study assesses three landscape performance metrics of McHarg's approach: stormwater runoff, urban heat island effect, and social acceptance. Geographic Information Systems (GIS) was used to assess the development extent and land surface temperature distribution. Results show that McHarg's approach demonstrates benefits in reducing runoff and urban heat island effect, whereas it confronts challenges with the general acceptance of manicured landscapes and thus results in a low safety perception level when residents interact with naturally designed landscapes. The authors argue that design-with-nature warrants multifunctionality because of its intrinsic interdisciplinary approach. Moreover, education and dissemination of successful examples can achieve a greater level of awareness among the public and further promote multifunctional design for landscape sustainability. PMID:24169408

  9. Landscape ecological assessment and eco-tourism development in the South Dongting Lake Wetland, China.

    PubMed

    He, Ping; Wang, Bao-zhong

    2003-03-01

    As an important resource and the living environment of mankind, wetland has become gradually a highlight, strongly concerned and intensively studied by scientists and sociologists. The governments in the world and the whole society have been paying more and more attention on it. The Dongting Lake of China is regarded as an internationally important wetland. For a rational development and protection of the wetland, an investigation and studied on its resources and its value to tourism in the South Dongting Lake was conducted, to create an assessment system of the ecological landscapes, and to evaluate qualitatively and quantitatively the value of wetland landscape to the ecotourism. The results showed that the scenic value of the South Dongting Lake Wetland satisfied the criterion of AAAA grade of China national scenic attraction. The eco-tourism value of the landscape cultures in the South Dongting Lake Wetland was discussed with emphasis. It were formulated that a principle and frame of sustainable exploitation of the wetland landscapes and it was proposed as well that establishing a Wetland Park and developing eco-tourism in the South Dongting Lake Wetland is a fragile ecosystem with low resistance to the impact of the exploitation. Thus, we must pay intensively attention to the influence of exploitation on the landscape, take the ecological risk in account to employ a right countermeasure and avoid the negative affection.

  10. Design-with-nature for multifunctional landscapes: environmental benefits and social barriers in community development.

    PubMed

    Yang, Bo; Li, Ming-Han; Li, Shujuan

    2013-11-01

    Since the early 1970s, Ian McHarg's design-with-nature concept has been inspiring landscape architects, community and regional planners, and liked-minded professionals to create designs that take advantage of ecosystem services and promote environmental and public health. This study bridges the gap in the literature that has resulted from a lack of empirical examinations on the multiple performance benefits derived through design-with-nature and the under-investigated social aspect emanated from McHarg's Ecological Determinism design approach. The Woodlands, TX, USA, an ecologically designed community development under McHarg's approach, is compared with two adjacent communities that follow the conventional design approach. Using national environmental databases and multiple-year residents' survey information, this study assesses three landscape performance metrics of McHarg's approach: stormwater runoff, urban heat island effect, and social acceptance. Geographic Information Systems (GIS) was used to assess the development extent and land surface temperature distribution. Results show that McHarg's approach demonstrates benefits in reducing runoff and urban heat island effect, whereas it confronts challenges with the general acceptance of manicured landscapes and thus results in a low safety perception level when residents interact with naturally designed landscapes. The authors argue that design-with-nature warrants multifunctionality because of its intrinsic interdisciplinary approach. Moreover, education and dissemination of successful examples can achieve a greater level of awareness among the public and further promote multifunctional design for landscape sustainability.

  11. From understanding the development landscape of the canonical fate-switch pair to constructing a dynamic landscape for two-step neural differentiation.

    PubMed

    Qiu, Xiaojie; Ding, Shanshan; Shi, Tieliu

    2012-12-20

    Recent progress in stem cell biology, notably cell fate conversion, calls for novel theoretical understanding for cell differentiation. The existing qualitative concept of Waddington's "epigenetic landscape" has attracted particular attention because it captures subsequent fate decision points, thus manifesting the hierarchical ("tree-like") nature of cell fate diversification. Here, we generalized a recent work and explored such a developmental landscape for a two-gene fate decision circuit by integrating the underlying probability landscapes with different parameters (corresponding to distinct developmental stages). The change of entropy production rate along the parameter changes indicates which parameter changes can represent a normal developmental process while other parameters' change can not. The transdifferentiation paths over the landscape under certain conditions reveal the possibility of a direct and reversible phenotypic conversion. As the intensity of noise increases, we found that the landscape becomes flatter and the dominant paths more straight, implying the importance of biological noise processing mechanism in development and reprogramming. We further extended the landscape of the one-step fate decision to that for two-step decisions in central nervous system (CNS) differentiation. A minimal network and dynamic model for CNS differentiation was firstly constructed where two three-gene motifs are coupled. We then implemented the SDEs (Stochastic Differentiation Equations) simulation for the validity of the network and model. By integrating the two landscapes for the two switch gene pairs, we constructed the two-step development landscape for CNS differentiation. Our work provides new insights into cellular differentiation and important clues for better reprogramming strategies.

  12. Determinants of woody cover in African savannas

    USGS Publications Warehouse

    Sankaran, M.; Hanan, N.P.; Scholes, R.J.; Ratnam, J.; Augustine, D.J.; Cade, B.S.; Gignoux, J.; Higgins, S.I.; Le, Roux X.; Ludwig, F.; Ardo, J.; Banyikwa, F.; Bronn, A.; Bucini, G.; Caylor, K.K.; Coughenour, M.B.; Diouf, A.; Ekaya, W.; Feral, C.J.; February, E.C.; Frost, P.G.H.; Hiernaux, P.; Hrabar, H.; Metzger, K.L.; Prins, H.H.T.; Ringrose, S.; Sea, W.; Tews, J.; Worden, J.; Zambatis, N.

    2005-01-01

    Savannas are globally important ecosystems of great significance to human economies. In these biomes, which are characterized by the co-dominance of trees and grasses, woody cover is a chief determinant of ecosystem properties 1-3. The availability of resources (water, nutrients) and disturbance regimes (fire, herbivory) are thought to be important in regulating woody cover1,2,4,5, but perceptions differ on which of these are the primary drivers of savanna structure. Here we show, using data from 854 sites across Africa, that maximum woody cover in savannas receiving a mean annual precipitation (MAP) of less than ???650 mm is constrained by, and increases linearly with, MAP. These arid and semi-arid savannas may be considered 'stable' systems in which water constrains woody cover and permits grasses to coexist, while fire, herbivory and soil properties interact to reduce woody cover below the MAP-controlled upper bound. Above a MAP of ???650 mm, savannas are 'unstable' systems in which MAP is sufficient for woody canopy closure, and disturbances (fire, herbivory) are required for the coexistence of trees and grass. These results provide insights into the nature of African savannas and suggest that future changes in precipitation 6 may considerably affect their distribution and dynamics. ?? 2005 Nature Publishing Group.

  13. Disaggregating tree and grass phenology in tropical savannas

    NASA Astrophysics Data System (ADS)

    Zhou, Qiang

    Savannas are mixed tree-grass systems and as one of the world's largest biomes represent an important component of the Earth system affecting water and energy balances, carbon sequestration and biodiversity as well as supporting large human populations. Savanna vegetation structure and its distribution, however, may change because of major anthropogenic disturbances from climate change, wildfire, agriculture, and livestock production. The overstory and understory may have different water use strategies, different nutrient requirements and have different responses to fire and climate variation. The accurate measurement of the spatial distribution and structure of the overstory and understory are essential for understanding the savanna ecosystem. This project developed a workflow for separating the dynamics of the overstory and understory fractional cover in savannas at the continental scale (Australia, South America, and Africa). Previous studies have successfully separated the phenology of Australian savanna vegetation into persistent and seasonal greenness using time series decomposition, and into fractions of photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV) and bare soil (BS) using linear unmixing. This study combined these methods to separate the understory and overstory signal in both the green and senescent phenological stages using remotely sensed imagery from the MODIS (MODerate resolution Imaging Spectroradiometer) sensor. The methods and parameters were adjusted based on the vegetation variation. The workflow was first tested at the Australian site. Here the PV estimates for overstory and understory showed best performance, however NPV estimates exhibited spatial variation in validation relationships. At the South American site (Cerrado), an additional method based on frequency unmixing was developed to separate green vegetation components with similar phenology. When the decomposition and frequency methods were compared, the frequency

  14. Large carnivores make savanna tree communities less thorny.

    PubMed

    Ford, Adam T; Goheen, Jacob R; Otieno, Tobias O; Bidner, Laura; Isbell, Lynne A; Palmer, Todd M; Ward, David; Woodroffe, Rosie; Pringle, Robert M

    2014-10-17

    Understanding how predation risk and plant defenses interactively shape plant distributions is a core challenge in ecology. By combining global positioning system telemetry of an abundant antelope (impala) and its main predators (leopards and wild dogs) with a series of manipulative field experiments, we showed that herbivores' risk-avoidance behavior and plants' antiherbivore defenses interact to determine tree distributions in an African savanna. Well-defended thorny Acacia trees (A. etbaica) were abundant in low-risk areas where impala aggregated but rare in high-risk areas that impala avoided. In contrast, poorly defended trees (A. brevispica) were more abundant in high- than in low-risk areas. Our results suggest that plants can persist in landscapes characterized by intense herbivory, either by defending themselves or by thriving in risky areas where carnivores hunt. PMID:25324387

  15. A model inter-comparison study to examine limiting factors in modelling Australian tropical savannas

    NASA Astrophysics Data System (ADS)

    Whitley, R.; Beringer, J.; Hutley, L.; Abramowitz, G.; De Kauwe, M. G.; Duursma, R.; Evans, B.; Haverd, V.; Li, L.; Ryu, Y.; Smith, B.; Wang, Y.-P.; Williams, M.; Yu, Q.

    2015-12-01

    Savanna ecosystems are one of the most dominant and complex terrestrial biomes that derives from a distinct vegetative surface comprised of co-dominant tree and grass populations. While these two vegetation types co-exist functionally, demographically they are not static, but are dynamically changing in response to environmental forces such as annual fire events and rainfall variability. Modelling savanna environments with the current generation of terrestrial biosphere models (TBMs) has presented many problems, particularly describing fire frequency and intensity, phenology, leaf biochemistry of C3 and C4 photosynthesis vegetation, and root water uptake. In order to better understand why TBMs perform so poorly in savannas, we conducted a model inter-comparison of 6 TBMs and assessed their performance at simulating latent energy (LE) and gross primary productivity (GPP) for five savanna sites along a rainfall gradient in northern Australia. Performance in predicting LE and GPP was measured using an empirical benchmarking system, which ranks models by their ability to utilise meteorological driving information to predict the fluxes. On average, the TBMs performed as well as a multi-linear regression of the fluxes against solar radiation, temperature and vapour pressure deficit, but were outperformed by a more complicated nonlinear response model that also included the leaf area index (LAI). This identified that the TBMs are not fully utilising their input information effectively in determining savanna LE and GPP, and highlights that savanna dynamics cannot be calibrated into models and that there are problems in underlying model processes. We identified key weaknesses in a model's ability to simulate savanna fluxes and their seasonal variation, related to the representation of vegetation by the models and root water uptake. We underline these weaknesses in terms of three critical areas for development. First, prescribed tree-rooting depths must be deep enough

  16. A model inter-comparison study to examine limiting factors in modelling Australian tropical savannas

    NASA Astrophysics Data System (ADS)

    Whitley, Rhys; Beringer, Jason; Hutley, Lindsay B.; Abramowitz, Gab; De Kauwe, Martin G.; Duursma, Remko; Evans, Bradley; Haverd, Vanessa; Li, Longhui; Ryu, Youngryel; Smith, Benjamin; Wang, Ying-Ping; Williams, Mathew; Yu, Qiang

    2016-06-01

    The savanna ecosystem is one of the most dominant and complex terrestrial biomes, deriving from a distinct vegetative surface comprised of co-dominant tree and grass populations. While these two vegetation types co-exist functionally, demographically they are not static but are dynamically changing in response to environmental forces such as annual fire events and rainfall variability. Modelling savanna environments with the current generation of terrestrial biosphere models (TBMs) has presented many problems, particularly describing fire frequency and intensity, phenology, leaf biochemistry of C3 and C4 photosynthesis vegetation, and root-water uptake. In order to better understand why TBMs perform so poorly in savannas, we conducted a model inter-comparison of six TBMs and assessed their performance at simulating latent energy (LE) and gross primary productivity (GPP) for five savanna sites along a rainfall gradient in northern Australia. Performance in predicting LE and GPP was measured using an empirical benchmarking system, which ranks models by their ability to utilise meteorological driving information to predict the fluxes. On average, the TBMs performed as well as a multi-linear regression of the fluxes against solar radiation, temperature and vapour pressure deficit but were outperformed by a more complicated nonlinear response model that also included the leaf area index (LAI). This identified that the TBMs are not fully utilising their input information effectively in determining savanna LE and GPP and highlights that savanna dynamics cannot be calibrated into models and that there are problems in underlying model processes. We identified key weaknesses in a model's ability to simulate savanna fluxes and their seasonal variation, related to the representation of vegetation by the models and root-water uptake. We underline these weaknesses in terms of three critical areas for development. First, prescribed tree-rooting depths must be deep enough

  17. A LANDSCAPE DEVELOPMENT INTENSITY MAP OF MARYLAND, USA

    EPA Science Inventory

    We present a map of human development intensity for central and eastern Maryland using an index derived from energy systems principles. Brown and Vivas developed a measure of the intensity of human development based on the nonrenewable energy use per unit area as an index to exp...

  18. Spatial Pattern Enhances Ecosystem Functioning in an African Savanna

    PubMed Central

    Pringle, Robert M.; Doak, Daniel F.; Brody, Alison K.; Jocqué, Rudy; Palmer, Todd M.

    2010-01-01

    The finding that regular spatial patterns can emerge in nature from local interactions between organisms has prompted a search for the ecological importance of these patterns. Theoretical models have predicted that patterning may have positive emergent effects on fundamental ecosystem functions, such as productivity. We provide empirical support for this prediction. In dryland ecosystems, termite mounds are often hotspots of plant growth (primary productivity). Using detailed observations and manipulative experiments in an African savanna, we show that these mounds are also local hotspots of animal abundance (secondary and tertiary productivity): insect abundance and biomass decreased with distance from the nearest termite mound, as did the abundance, biomass, and reproductive output of insect-eating predators. Null-model analyses indicated that at the landscape scale, the evenly spaced distribution of termite mounds produced dramatically greater abundance, biomass, and reproductive output of consumers across trophic levels than would be obtained in landscapes with randomly distributed mounds. These emergent properties of spatial pattern arose because the average distance from an arbitrarily chosen point to the nearest feature in a landscape is minimized in landscapes where the features are hyper-dispersed (i.e., uniformly spaced). This suggests that the linkage between patterning and ecosystem functioning will be common to systems spanning the range of human management intensities. The centrality of spatial pattern to system-wide biomass accumulation underscores the need to conserve pattern-generating organisms and mechanisms, and to incorporate landscape patterning in efforts to restore degraded habitats and maximize the delivery of ecosystem services. PMID:20520846

  19. The epigenetic landscape of mammary gland development and functional differentiation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Most of the development and functional differentiation in the mammary gland occur after birth. Epigenetics is defined as the stable alterations in gene expression potential that arise during development and proliferation. Epigenetic changes are mediated at the biochemical level by the chromatin conf...

  20. Large-scale impacts of herbivores on the structural diversity of African savannas.

    PubMed

    Asner, Gregory P; Levick, Shaun R; Kennedy-Bowdoin, Ty; Knapp, David E; Emerson, Ruth; Jacobson, James; Colgan, Matthew S; Martin, Roberta E

    2009-03-24

    African savannas are undergoing management intensification, and decision makers are increasingly challenged to balance the needs of large herbivore populations with the maintenance of vegetation and ecosystem diversity. Ensuring the sustainability of Africa's natural protected areas requires information on the efficacy of management decisions at large spatial scales, but often neither experimental treatments nor large-scale responses are available for analysis. Using a new airborne remote sensing system, we mapped the three-dimensional (3-D) structure of vegetation at a spatial resolution of 56 cm throughout 1640 ha of savanna after 6-, 22-, 35-, and 41-year exclusions of herbivores, as well as in unprotected areas, across Kruger National Park in South Africa. Areas in which herbivores were excluded over the short term (6 years) contained 38%-80% less bare ground compared with those that were exposed to mammalian herbivory. In the longer-term (> 22 years), the 3-D structure of woody vegetation differed significantly between protected and accessible landscapes, with up to 11-fold greater woody canopy cover in the areas without herbivores. Our maps revealed 2 scales of ecosystem response to herbivore consumption, one broadly mediated by geologic substrate and the other mediated by hillslope-scale variation in soil nutrient availability and moisture conditions. Our results are the first to quantitatively illustrate the extent to which herbivores can affect the 3-D structural diversity of vegetation across large savanna landscapes.

  1. Deriving Multiple Benefits from Carbon Market-Based Savanna Fire Management: An Australian Example.

    PubMed

    Russell-Smith, Jeremy; Yates, Cameron P; Edwards, Andrew C; Whitehead, Peter J; Murphy, Brett P; Lawes, Michael J

    2015-01-01

    Carbon markets afford potentially useful opportunities for supporting socially and environmentally sustainable land management programs but, to date, have been little applied in globally significant fire-prone savanna settings. While fire is intrinsic to regulating the composition, structure and dynamics of savanna systems, in north Australian savannas frequent and extensive late dry season wildfires incur significant environmental, production and social impacts. Here we assess the potential of market-based savanna burning greenhouse gas emissions abatement and allied carbon biosequestration projects to deliver compatible environmental and broader socio-economic benefits in a highly biodiverse north Australian setting. Drawing on extensive regional ecological knowledge of fire regime effects on fire-vulnerable taxa and communities, we compare three fire regime metrics (seasonal fire frequency, proportion of long-unburnt vegetation, fire patch-size distribution) over a 15-year period for three national parks with an indigenously (Aboriginal) owned and managed market-based emissions abatement enterprise. Our assessment indicates improved fire management outcomes under the emissions abatement program, and mostly little change or declining outcomes on the parks. We attribute improved outcomes and putative biodiversity benefits under the abatement program to enhanced strategic management made possible by the market-based mitigation arrangement. For these same sites we estimate quanta of carbon credits that could be delivered under realistic enhanced fire management practice, using currently available and developing accredited Australian savanna burning accounting methods. We conclude that, in appropriate situations, market-based savanna burning activities can provide transformative climate change mitigation, ecosystem health, and community benefits in northern Australia, and, despite significant challenges, potentially in other fire-prone savanna settings. PMID:26630453

  2. Deriving Multiple Benefits from Carbon Market-Based Savanna Fire Management: An Australian Example.

    PubMed

    Russell-Smith, Jeremy; Yates, Cameron P; Edwards, Andrew C; Whitehead, Peter J; Murphy, Brett P; Lawes, Michael J

    2015-01-01

    Carbon markets afford potentially useful opportunities for supporting socially and environmentally sustainable land management programs but, to date, have been little applied in globally significant fire-prone savanna settings. While fire is intrinsic to regulating the composition, structure and dynamics of savanna systems, in north Australian savannas frequent and extensive late dry season wildfires incur significant environmental, production and social impacts. Here we assess the potential of market-based savanna burning greenhouse gas emissions abatement and allied carbon biosequestration projects to deliver compatible environmental and broader socio-economic benefits in a highly biodiverse north Australian setting. Drawing on extensive regional ecological knowledge of fire regime effects on fire-vulnerable taxa and communities, we compare three fire regime metrics (seasonal fire frequency, proportion of long-unburnt vegetation, fire patch-size distribution) over a 15-year period for three national parks with an indigenously (Aboriginal) owned and managed market-based emissions abatement enterprise. Our assessment indicates improved fire management outcomes under the emissions abatement program, and mostly little change or declining outcomes on the parks. We attribute improved outcomes and putative biodiversity benefits under the abatement program to enhanced strategic management made possible by the market-based mitigation arrangement. For these same sites we estimate quanta of carbon credits that could be delivered under realistic enhanced fire management practice, using currently available and developing accredited Australian savanna burning accounting methods. We conclude that, in appropriate situations, market-based savanna burning activities can provide transformative climate change mitigation, ecosystem health, and community benefits in northern Australia, and, despite significant challenges, potentially in other fire-prone savanna settings.

  3. Deriving Multiple Benefits from Carbon Market-Based Savanna Fire Management: An Australian Example

    PubMed Central

    Russell-Smith, Jeremy; Yates, Cameron P.; Edwards, Andrew C.; Whitehead, Peter J.; Murphy, Brett P.; Lawes, Michael J.

    2015-01-01

    Carbon markets afford potentially useful opportunities for supporting socially and environmentally sustainable land management programs but, to date, have been little applied in globally significant fire-prone savanna settings. While fire is intrinsic to regulating the composition, structure and dynamics of savanna systems, in north Australian savannas frequent and extensive late dry season wildfires incur significant environmental, production and social impacts. Here we assess the potential of market-based savanna burning greenhouse gas emissions abatement and allied carbon biosequestration projects to deliver compatible environmental and broader socio-economic benefits in a highly biodiverse north Australian setting. Drawing on extensive regional ecological knowledge of fire regime effects on fire-vulnerable taxa and communities, we compare three fire regime metrics (seasonal fire frequency, proportion of long-unburnt vegetation, fire patch-size distribution) over a 15-year period for three national parks with an indigenously (Aboriginal) owned and managed market-based emissions abatement enterprise. Our assessment indicates improved fire management outcomes under the emissions abatement program, and mostly little change or declining outcomes on the parks. We attribute improved outcomes and putative biodiversity benefits under the abatement program to enhanced strategic management made possible by the market-based mitigation arrangement. For these same sites we estimate quanta of carbon credits that could be delivered under realistic enhanced fire management practice, using currently available and developing accredited Australian savanna burning accounting methods. We conclude that, in appropriate situations, market-based savanna burning activities can provide transformative climate change mitigation, ecosystem health, and community benefits in northern Australia, and, despite significant challenges, potentially in other fire-prone savanna settings. PMID:26630453

  4. Seasonal Distribution of African Savanna Fires

    NASA Technical Reports Server (NTRS)

    Cahoon, Donald R.; Stocks, Brian J.; Levine, Joel S.; Cofer, Wesley R., III; O'Neill, Katherine P.

    1992-01-01

    Savannas consist of a continuous layer of grass interspersed with scattered trees or shrubs, and cover approx. 10 million square kilometers of tropical Africa. African savanna fires, almost all resulting from human activities, may produce as much as a third of the total global emissions from biomass burning. Little is known, however, about the frequency and location of these fires, and the area burned each year. Emissions from African savanna burning are known to be transported over the mid-Atlantic, south Pacific and Indian oceans; but to study fully the transport of regional savanna burning and the seasonality of the atmospheric circulation must be considered simultaneously. Here we describe the temporal and spatial distribution of savanna fires over the entire African continent, as determined from night-time satellite imagery. We find that, contrary to expectations, most fires are left to burn uncontrolled, so that there is no strong diurnal cycle in the fire frequency. The knowledge gained from this study regarding the distribution and variability of fires will aid monitoring of the climatically important trace gases emitted from burning biomass.

  5. Soil development on stable landforms and implications for landscape studies

    USGS Publications Warehouse

    Harden, J.W.

    1990-01-01

    Soil development parameters include a wide variety of morphological, chemical, and mineralogical parameters, but some of the best indicators of time and surface stability are derived from field morphology. Over long time-spans, the most common time function for soil development is exponential or logarithmic, in which rates decrease with increasing age. Over shorter time-spans in semi-arid and moister climates, Holocene and Pleistocene soil development functions appear as linear segments, with Holocene rates about 10 to 50 times those of Pleistocene rates. In contrast to significant temporal variation in rates, geographical variation in rates within (a) the southern Great Basin and (b) the east Central Valley of California is on the order of 2 or 3 times. When comparing soil development indices of the semi-arid Great Basin to those of moister central California, Holocene rates are similar, but Pleistocene rates are more than 10 times slower in the Great Basin. In a range of climatic settings, the reasons for declining rates over time are several and are complexly related to erosional history, fluxes in water and dust related to climatic changes, rates of primary mineral dissolution, and intrinsic soil processes. ?? 1990.

  6. Development of a Digital Aquifer Permeability Map for the Pacific Southwest in Support of Hydrologic Landscape Classification: Methods

    EPA Science Inventory

    Researchers at the U.S. Environmental Protection Agency’s Western Ecology Division have been developing hydrologic landscape maps for selected U.S. states in an effort to create a method to identify the intrinsic watershed attributes of landscapes in regions with little dat...

  7. Dynamic landscape of tandem 3' UTRs during zebrafish development.

    PubMed

    Li, Yuxin; Sun, Yu; Fu, Yonggui; Li, Mengzhen; Huang, Guangrui; Zhang, Chenxu; Liang, Jiahui; Huang, Shengfeng; Shen, Gaoyang; Yuan, Shaochun; Chen, Liangfu; Chen, Shangwu; Xu, Anlong

    2012-10-01

    Tandem 3' untranslated regions (UTRs), produced by alternative polyadenylation (APA) in the terminal exon of a gene, could have critical roles in regulating gene networks. Here we profiled tandem poly(A) events on a genome-wide scale during the embryonic development of zebrafish (Danio rerio) using a recently developed SAPAS method. We showed that 43% of the expressed protein-coding genes have tandem 3' UTRs. The average 3' UTR length follows a V-shaped dynamic pattern during early embryogenesis, in which the 3' UTRs are first shortened at zygotic genome activation, and then quickly lengthened during gastrulation. Over 4000 genes are found to switch tandem APA sites, and the distinct functional roles of these genes are indicated by Gene Ontology analysis. Three families of cis-elements, including miR-430 seed, U-rich element, and canonical poly(A) signal, are enriched in 3' UTR-shortened/lengthened genes in a stage-specific manner, suggesting temporal regulation coordinated by APA and trans-acting factors. Our results highlight the regulatory role of tandem 3' UTR control in early embryogenesis and suggest that APA may represent a new epigenetic paradigm of physiological regulations.

  8. Development of a reproducible method for determining quantity of water and its configuration in a marsh landscape

    USGS Publications Warehouse

    Suir, Glenn M.; Evers, D. Elaine; Steyer, Gregory D.; Sasser, Charles E.

    2013-01-01

    Coastal Louisiana is a dynamic and ever-changing landscape. From 1956 to 2010, over 3,734 km2 of Louisiana's coastal wetlands have been lost due to a combination of natural and human-induced activities. The resulting landscape constitutes a mosaic of conditions from highly deteriorated to relatively stable with intact landmasses. Understanding how and why coastal landscapes change over time is critical to restoration and rehabilitation efforts. Historically, changes in marsh pattern (i.e., size and spatial distribution of marsh landmasses and water bodies) have been distinguished using visual identification by individual researchers. Difficulties associated with this approach include subjective interpretation, uncertain reproducibility, and laborious techniques. In order to minimize these limitations, this study aims to expand existing tools and techniques via a computer-based method, which uses geospatial technologies for determining shifts in landscape patterns. Our method is based on a raster framework and uses landscape statistics to develop conditions and thresholds for a marsh classification scheme. The classification scheme incorporates land and water classified imagery and a two-part classification system: (1) ratio of water to land, and (2) configuration and connectivity of water within wetland landscapes to evaluate changes in marsh patterns. This analysis system can also be used to trace trajectories in landscape patterns through space and time. Overall, our method provides a more automated means of quantifying landscape patterns and may serve as a reliable landscape evaluation tool for future investigations of wetland ecosystem processes in the northern Gulf of Mexico.

  9. The Holocene landscape development of the Gareja region in eastern Georgia (Caucasus region) - an interdisciplinary approach

    NASA Astrophysics Data System (ADS)

    Elashvili, M.; Sukhishvili, L.; Navrozashvili, L.; Kikvadze, B.; Janelidze, Z.; von Suchodoletz, H.

    2014-12-01

    Recognizing the fact that we are living in a constantly changing world became actual during the last decades, and promoted numerous studies related to the environmental consequences of climate change and human impact. In this context, the study of human- and naturally-triggered palaeoenvironmental changes leads to a better understanding of possible changes during the future. Human impact became progressively important during the last millenia, and caused dramatic changes of the natural environment especially in fragile landscapes. The semi-arid Gareja region in the Iori Highland in the eastern part of the Republic of Georgia is characterized by an annual precipitation < 600 mm and shows an open steppic landscape today. As is known from historical sources, the landscape showed the same character already during the 6th century AD when the Gareja monastery located in the center of the region was founded by Assyrian monks. However, archaeological research carried out during the Soviet Period showed the existence of numerous settlements of bronze and iron age in this region almost devoid of water resources today, hinting to some sources of fresh water allowing people to live there during those periods. Furthermore, former archaeo-botanical studies assume that the region was covered by forests instead of steppes during the past, although there is no final proof yet. The goal of this study is to shed light on the development of the Gareja landscape during the prehistoric period and thus to address some of the issues described above. To do so, our work is based on the spatial pattern of prehistoric settlements derived from archaeologic data of the Soviet period, GIS stream modelling and the analysis of fluvial and slope deposits from the area using a multi-proxy approach. Altogether, these data indicate a dramatic palaeoenvironmental change in the Gareja region ca. 3 ka ago, leading to the recent steppe and almost unpopulated character of the landscape.

  10. NO x emissions from African savanna fires

    NASA Astrophysics Data System (ADS)

    Lacaux, J. P.; Delmas, R.; Jambert, C.; Kuhlbusch, T. A. J.

    1996-10-01

    Fire of Savanna/Dynamique et Chimie Atmosphèrique en Forêt Equatoriale (FOS/DECAFE-91) and Southern African Fire-Atmosphere Research Initiative (SAFARI-92) were two multidisciplinary experiments organized in Africa to determine the gas and aerosol emissions due to prescribed savanna fires. These two experiments took place in two types of savannas which have very different ecological properties: Lamto, Ivory Coast (FOS/DECAFE-91), in the Guinean area, is wet (80% moisture content) and dense (9 to 10 t ha-1) and has little litter (2 to 5% of total biomass); Kruger Park, in South Africa (SAFARI-92), on the contrary, is dry (10 to 20% moisture) and has a low biomass (3 to 6 t ha-1) and 40% of its total biomass in the form of litter. The experimental strategy used to determine the emission ratios ΔCO/ΔCO2 and ΔNOx/ΔCO2 was to measure at ground level, in the same volume of the plume above the fire, the CO, CO2 and NOx concentrations. The mean carbon content of the two savannas was similar (about 43%), and the ΔCO/ΔCO2 ratio, the indicator of the burning process, was comparable in back and head fires with mean ratios between 4.5 and 6.1%. These ΔCO/ΔCO2 ratios were characteristic of intense flaming combustion with the formation of mainly fully oxidized compounds for both savannas. The ΔCO/ΔCO2 ratio for the head fires can be divided into two distinct phases: a flaming period and a smoke period which immediately follows. Nitrogen concentration of the two savannas varied from as low as 0.3% in Lamto to 0.80% of dry mass in the Kruger Park in the Faai plot. In this study we could clearly identify a linear dependency between the nitrogen concentration of the dry and wet savannas of Africa and the NOx/CO2 emission ratio, ΔNOx/ΔCO2 = 0.66 N% - 0.01, with a correlation coefficient of 0.93, statistically significant at a confidence level better than 99%. This result enables the quantification of the emissions of NOx from African savanna burning by measuring the

  11. A landscape ecology approach to assessing development impacts in the tropics: A geothermal energy example in Hawaii

    USGS Publications Warehouse

    Griffith, J.A.; Trettin, C.C.; O'Neill, R. V.

    2002-01-01

    Geographic information systems (GIS) are increasingly being used in environmental impact assessments (EIA) because GIS is useful for analysing spatial impacts of various development scenarios. Spatially representing these impacts provides another tool for landscape ecology in environmental and geographical investigations by facilitating analysis of the effects of landscape patterns on ecological processes and examining change over time. Landscape ecological principles are applied in this study to a hypothetical geothermal development project on the Island of Hawaii. Some common landscape pattern metrics were used to analyse dispersed versus condensed development scenarios and their effect on landscape pattern. Indices of fragmentation and patch shape did not appreciably change with additional development. The amount of forest to open edge, however, greatly increased with the dispersed development scenario. In addition, landscape metrics showed that a human disturbance had a greater simplifying effect on patch shape and also increased fragmentation than a natural disturbance. The use of these landscape pattern metrics can advance the methodology of applying GIS to EIA.

  12. The impact of industrial oil development on a protected area landscape: A case study on human population growth and landscape level change in Murchison Falls Conservation Area, Uganda.

    NASA Astrophysics Data System (ADS)

    Dowhaniuk, Nicholas; Hartter, Joel; Congalton, Russell G.; Palace, Michael W.; Ryan, Sadie J.

    2016-04-01

    Protected areas in Sub-Saharan Africa are sanctuaries for rich biodiversity and are important economic engines for African nations, but they are becoming increasingly threatened by discoveries of mineral deposits within and nearby their boundaries. In 2006, viable oil reserves were discovered in Murchison Falls Conservation Area (MFCA) in northern Uganda. Exploratory and appraisal activities concluded in 2014, and production is expected to begin in 2016. The oil development is associated with a substantial increase in human population outside MFCA, with people seeking jobs, land, and economic opportunity. Concomitant with this change is increased truck traffic, a sprawling and denser road network, and infrastructure within the park, which could have large impacts on both the flora and fauna. We examined the broader protected area landscape and the potential feedbacks from resource development on the ecosystem and local livelihoods. Our analysis combines a land cover analysis using Object Based Image Analysis of Landsat data (2002 and 2014), migration patterns and population change (1959-2014), and qualitative interview data. Our results suggest that most of the larger-scale impacts on the landscape and people are occurring in the western and northern sections, both inside and outside of the park. Additionally, oil development is not the only factor in the region influencing population growth and landscape change. Post conflict regrowth in the north, sugarcane production in the south, and migration to this region from conflict-ridden neighboring countries are also playing a vital role in human migration shaping the MFCA Landscape. Understanding the social and environmental changes and impacts in the MFCA and its surrounding areas will add to limited literature on the impacts of resource extraction on local, subsistence communities and landscape level change, which will be important as access and pressure for oil and minerals within protected areas continues to rise.

  13. Carbon, Water and Energy Fluxes in an African Savanna Ecosystem

    NASA Astrophysics Data System (ADS)

    Hanan, N. P.; Scholes, R. J.; Privette, J. L.

    2001-12-01

    Eddy covariance measurements of the turbulent fluxes of CO2, water and energy, and associated micrometeorological and biophysical measurements, have been made at a site in the Kruger National Park (KNP), South Africa, since April 2000. The study site is located in the southern region of KNP in a gently undulating landscape on granite substrate, with drainage lines 2-3 km apart and ridge tops 30-40 meters above the valley floors. The climate is semi-arid subtropical, with hot, rainy summers, warm dry winters and annual average rainfall of 550-650 mm. The soils of the catena vary between coarse-textured sand near the ridge-tops and finer-textured loamy-sand on the mid-slope and valley floors. The vegetation also differs along the catena, with broad-leaved tree species and low palatability grasses on the sandy soil and bi-pinnate tree species and more palatable grasses on the loam soils. The natural disturbance regime of the site includes fire, at return intervals of 3-8 years, as well as grazing and browsing by numerous species of wild ungulate. Results from the first 18 months of flux measurements are presented, contrasting an unusually wet growing season (1999-2000), followed by a dry-season fire, and a growing season with more average rainfall (2000-2001). The functional and phenological differences between broad-leaf and fine-leaf savanna are explored, and the carbon and water dynamics of the savanna systems interpreted in the context of seasonal weather variation, soil type and nutrient status.

  14. Prospects of the ICESat-2 laser altimetry mission for savanna ecosystem structural studies based on airborne simulation data

    NASA Astrophysics Data System (ADS)

    Gwenzi, David; Lefsky, Michael A.; Suchdeo, Vijay P.; Harding, David J.

    2016-08-01

    The next planned spaceborne lidar mission is the Ice, Cloud and land Elevation Satellite 2 (ICESat-2), which will use the Advanced Topographic Laser Altimeter System (ATLAS) sensor, a photon counting technique. To pre-validate the capability of this mission for studying three dimensional vegetation structure in savannas, we assessed the potential of the measurement approach to estimate canopy height in an oak savanna landscape. We used data from the Multiple Altimeter Beam Experimental Lidar (MABEL), an airborne photon counting lidar sensor developed by NASA's Goddard Space Flight Center. ATLAS-like data was generated using the MATLAS simulator, which adjusts MABEL data's detected number of signal and noise photons to that expected from the ATLAS instrument. Transects flown over the Tejon ranch conservancy in Kern County, California, USA were used for this work. For each transect we chose to use data from the near infrared channel that had the highest number of photons. We segmented each transect into 50 m, 25 m and 14 m long blocks and aggregated the photons in each block into a histogram based on their elevation values. We then used an automated algorithm to identify cut off points where the cumulative density of photons from the highest elevation indicates the presence of the canopy top and likewise where such cumulative density from the lowest elevation indicates the mean terrain elevation. MABEL derived height metrics were moderately correlated to discrete return lidar (DRL) derived height metrics (r2 and RMSE values ranging from 0.60 to 0.73 and 2.9 m to 4.4 m respectively) but MATLAS simulation resulted in more modest correlations with DRL indices (r2 ranging from 0.5 to 0.64 and RMSE from 3.6 m to 4.6 m). Simulations also indicated that the expected number of signal photons from ATLAS will be substantially lower, a situation that reduces canopy height estimation precision especially in areas of low density vegetation cover. On the basis of the simulated

  15. Broad-scale assessments of ecological landscapes: developing methods and applications

    USGS Publications Warehouse

    Carr, Natasha B.; Wood, David J. A.; Bowen, Zachary H.; Haby, Travis S.

    2015-01-01

    A major component of the BLM Landscape Approach is the Rapid Ecoregional Assessment (REA) program. REAs identify important ecosystems and wildlife habitats at broad spatial scales and determine where these resources are at risk from environmental stressors that can affect the integrity of ecological systems. Building on the lessons learned from completed or current REAs, the BLM, in partnership with the U.S. Geological Survey, will perform systematic comparisons of REA methods to identify the most promising suite of landscape-level analysis tools. In addition, the BLM and USGS will develop practical applications that demonstrate how to incorporate assessment information to address existing management issues, such as cumulative effects of proposed management actions. The outcome of these efforts will be a set of comprehensive technical guidance documents for conducting and applying broad-scale assessments.

  16. The Development of the Sacred Landscape of Saqqara in the Old Kingdom

    NASA Astrophysics Data System (ADS)

    Magli, Giulio

    2015-05-01

    Saqqara is one of the most important Necropolis in Egypt. In the course of the third millennium BC many Pharaohs choose Saqqara for their tombs. As a consequence the landscape constantly grew with the addition of new monuments, from the mastaba tombs of the first dynasty to the last pyramid of the Old Kingdom, that of Pepi II. The monuments were constructed respecting a series of topographical constraints which are not due to the morphology of the area but rather reflect symbolic - dynastic or astronomical - motivations. The analysis of these connections gives a better understanding of the choices made by the kings' architects in order to keep Maat - order - in the development of the site. Further, the way in which the sacred landscape came to be structured at the end of the Old Kingdom allows us to formulate a proposal for the possible location of the unique pyramid of the sixth dynasty which is still to be found: that of Userkare.

  17. Advancing environmental flow science: Developing frameworks for altered landscapes and integrating efforts across disciplines.

    USGS Publications Warehouse

    Brewer, Shannon K.; McManamay, Ryan A.; Miller, Andrew D.; Mollenhauer, Robert; Worthington, Thomas A.; Arsuffi, Tom

    2016-01-01

    Environmental flows represent a legal mechanism to balance existing and future water uses and sustain non-use values. Here, we identify current challenges, provide examples where they are important, and suggest research advances that would benefit environmental flow science. Specifically, environmental flow science would benefit by (1) developing approaches to address streamflow needs in highly modified landscapes where historic flows do not provide reasonable comparisons, (2) integrating water quality needs where interactions are apparent with quantity but not necessarily the proximate factor of the ecological degradation, especially as frequency and magnitudes of inflows to bays and estuaries, (3) providing a better understanding of the ecological needs of native species to offset the often unintended consequences of benefiting non-native species or their impact on flows, (4) improving our understanding of the non-use economic value to balance consumptive economic values, and (5) increasing our understanding of the stakeholder socioeconomic spatial distribution of attitudes and perceptions across the landscape. Environmental flow science is still an emerging interdisciplinary field and by integrating socioeconomic disciplines and developing new frameworks to accommodate our altered landscapes, we should help advance environmental flow science and likely increase successful implementation of flow standards.

  18. Advancing Environmental Flow Science: Developing Frameworks for Altered Landscapes and Integrating Efforts Across Disciplines

    NASA Astrophysics Data System (ADS)

    Brewer, Shannon K.; McManamay, Ryan A.; Miller, Andrew D.; Mollenhauer, Robert; Worthington, Thomas A.; Arsuffi, Tom

    2016-08-01

    Environmental flows represent a legal mechanism to balance existing and future water uses and sustain non-use values. Here, we identify current challenges, provide examples where they are important, and suggest research advances that would benefit environmental flow science. Specifically, environmental flow science would benefit by (1) developing approaches to address streamflow needs in highly modified landscapes where historic flows do not provide reasonable comparisons, (2) integrating water quality needs where interactions are apparent with quantity but not necessarily the proximate factor of the ecological degradation, especially as frequency and magnitudes of inflows to bays and estuaries, (3) providing a better understanding of the ecological needs of native species to offset the often unintended consequences of benefiting non-native species or their impact on flows, (4) improving our understanding of the non-use economic value to balance consumptive economic values, and (5) increasing our understanding of the stakeholder socioeconomic spatial distribution of attitudes and perceptions across the landscape. Environmental flow science is still an emerging interdisciplinary field and by integrating socioeconomic disciplines and developing new frameworks to accommodate our altered landscapes, we should help advance environmental flow science and likely increase successful implementation of flow standards.

  19. Advancing Environmental Flow Science: Developing Frameworks for Altered Landscapes and Integrating Efforts Across Disciplines.

    PubMed

    Brewer, Shannon K; McManamay, Ryan A; Miller, Andrew D; Mollenhauer, Robert; Worthington, Thomas A; Arsuffi, Tom

    2016-08-01

    Environmental flows represent a legal mechanism to balance existing and future water uses and sustain non-use values. Here, we identify current challenges, provide examples where they are important, and suggest research advances that would benefit environmental flow science. Specifically, environmental flow science would benefit by (1) developing approaches to address streamflow needs in highly modified landscapes where historic flows do not provide reasonable comparisons, (2) integrating water quality needs where interactions are apparent with quantity but not necessarily the proximate factor of the ecological degradation, especially as frequency and magnitudes of inflows to bays and estuaries, (3) providing a better understanding of the ecological needs of native species to offset the often unintended consequences of benefiting non-native species or their impact on flows, (4) improving our understanding of the non-use economic value to balance consumptive economic values, and (5) increasing our understanding of the stakeholder socioeconomic spatial distribution of attitudes and perceptions across the landscape. Environmental flow science is still an emerging interdisciplinary field and by integrating socioeconomic disciplines and developing new frameworks to accommodate our altered landscapes, we should help advance environmental flow science and likely increase successful implementation of flow standards.

  20. Basement Fracturing and Weathering On- and Offshore Norway - Genesis, Age, and Landscape Development

    NASA Astrophysics Data System (ADS)

    Knies, J.; van der Lelij, R.; Faust, J.; Scheiber, T.; Broenner, M.; Fredin, O.; Mueller, A.; Viola, G.

    2014-12-01

    Saprolite remnants onshore Scandinavia have been investigated only sporadically. The nature and age of the deeply weathered material thus remains only loosely constrained. The type and degree of weathering of in situ weathered soils are indicative of the environmental conditions during their formation. When external forcing changes, properties related to previous weathering conditions are usually preserved, for example in clay mineral assemblages. By constraining the age and rate of weathering onshore and by isotopically dating selected faults determined to be intimately linked to weathered basement blocks, the influence of climate development, brittle deformation and landscape processes on weathering can be quantified. The "BASE" project aims to establish a temporal and conceptual framework for brittle tectonics, weathering patterns and landscape evolution affecting the basement onshore and offshore Norway. We will study the formation of saprolite in pre-Quaternary times, the influence of deep weathering on landscape development and establish a conceptual structural template of the evolution of the brittle deformational features that are exposed on onshore (weathered) basement blocks. Moreover, saprolitic material may have been eroded and preserved along the Norwegian continental margin during Cenozoic times. By studying both the onshore remnants and offshore erosional products deposited during periods of extreme changes of climate and tectonic boundary conditions (e..g Miocene-Pliocene), new inferences on the timing and controlling mechanisms of denudation, and on the relevance of deep weathering on Late Cenozoic global cooling can be drawn.

  1. Advancing Environmental Flow Science: Developing Frameworks for Altered Landscapes and Integrating Efforts Across Disciplines

    DOE PAGES

    Brewer, Shannon; McManamay, Ryan A.; Miller, Andrew D.; Mollenhauer, Robert; Worthington, Thomas A.; Arsuffi, Tom

    2016-05-13

    Environmental flows represent a legal mechanism to balance existing and future water uses and sustain non-use values. Here, we identify current challenges, provide examples where they are important, and suggest research advances that would benefit environmental flow science. Specifically, environmental flow science would benefit by (1) developing approaches to address streamflow needs in highly modified landscapes where historic flows do not provide reasonable comparisons, (2) integrating water quality needs where interactions are apparent with quantity but not necessarily the proximate factor of the ecological degradation, especially as frequency and magnitudes of inflows to bays and estuaries, (3) providing a bettermore » understanding of the ecological needs of native species to offset the often unintended consequences of benefiting non-native species or their impact on flows, (4) improving our understanding of the non-use economic value to balance consumptive economic values, and (5) increasing our understanding of the stakeholder socioeconomic spatial distribution of attitudes and perceptions across the landscape. Environmental flow science is still an emerging interdisciplinary field and by integrating socioeconomic disciplines and developing new frameworks to accommodate our altered landscapes, we should help advance environmental flow science and likely increase successful implementation of flow standards.« less

  2. Advancing Environmental Flow Science: Developing Frameworks for Altered Landscapes and Integrating Efforts Across Disciplines.

    PubMed

    Brewer, Shannon K; McManamay, Ryan A; Miller, Andrew D; Mollenhauer, Robert; Worthington, Thomas A; Arsuffi, Tom

    2016-08-01

    Environmental flows represent a legal mechanism to balance existing and future water uses and sustain non-use values. Here, we identify current challenges, provide examples where they are important, and suggest research advances that would benefit environmental flow science. Specifically, environmental flow science would benefit by (1) developing approaches to address streamflow needs in highly modified landscapes where historic flows do not provide reasonable comparisons, (2) integrating water quality needs where interactions are apparent with quantity but not necessarily the proximate factor of the ecological degradation, especially as frequency and magnitudes of inflows to bays and estuaries, (3) providing a better understanding of the ecological needs of native species to offset the often unintended consequences of benefiting non-native species or their impact on flows, (4) improving our understanding of the non-use economic value to balance consumptive economic values, and (5) increasing our understanding of the stakeholder socioeconomic spatial distribution of attitudes and perceptions across the landscape. Environmental flow science is still an emerging interdisciplinary field and by integrating socioeconomic disciplines and developing new frameworks to accommodate our altered landscapes, we should help advance environmental flow science and likely increase successful implementation of flow standards. PMID:27177541

  3. Fuel model selection for BEHAVE in midwestern oak savannas

    USGS Publications Warehouse

    Grabner, K.W.; Dwyer, J.P.; Cutter, B.E.

    2001-01-01

    BEHAVE, a fire behavior prediction system, can be a useful tool for managing areas with prescribed fire. However, the proper choice of fuel models can be critical in developing management scenarios. BEHAVE predictions were evaluated using four standardized fuel models that partially described oak savanna fuel conditions: Fuel Model 1 (Short Grass), 2 (Timber and Grass), 3 (Tall Grass), and 9 (Hardwood Litter). Although all four models yielded regressions with R2 in excess of 0.8, Fuel Model 2 produced the most reliable fire behavior predictions.

  4. Origin and dynamics of the northern South American coastal savanna belt during the Holocene - the role of climate, sea-level, fire and humans

    NASA Astrophysics Data System (ADS)

    Alizadeh, Kamaleddin; Cohen, Marcelo; Behling, Hermann

    2015-08-01

    Presence of a coastal savanna belt expanding from British Guiana to northeastern Brazil cannot be explained by present-day climate. Using pollen and charcoal analyses on an 11.6 k old sediment core from a coastal depression in the savanna belt near the mouth of the Amazon River we investigated the paleoenvironmental history to shed light on this question. Results indicate that small areas of savanna accompanied by a forest type composed primarily by the genus Micropholis (Sapotaceae) that has no modern analog existed at the beginning of the Holocene. After 11,200 cal yr BP, savanna accompanied by few trees replaced the forest. In depressions swamp forest developed and by ca 10,000 cal yr BP replaced by Mauritia swamps. Between 8500 and 5600 cal yr BP gallery forest (composed mainly of Euphorbiaceae) and swamp forest succeeded the treeless savanna. The modern vegetation with alternating gallery forest and savanna developed after 5600 cal yr BP. We suggest that the early Holocene no-analog forest is a relict of previously more extensive forest under cooler and moister Lateglacial conditions. The early Holocene savanna expansion indicates a drier phase probably related to the shift of the Intertropical Convergence Zone (ITCZ) towards its northernmost position. The mid-Holocene forest expansion is probably a result of the combined influence of equatorwards shift of ITCZ joining the South Atlantic Convergence Zone (SACZ). The ecosystem variability during the last 5600 cal yr BP, formed perhaps under influence of intensified ENSO condition. High charcoal concentrations, especially during the early Holocene, indicate that natural and/or anthropogenic fires may have maintained the savanna. However, our results propose that climate change is the main driving factor for the formation of the coastal savanna in this region. Our results also show that the early Holocene sea level rise established mangroves near the study site until 7500 cal yr BP and promoted swamp formation in

  5. Self-thinning Concepts Applied to Savannas

    NASA Astrophysics Data System (ADS)

    Sea, W. B.; Hanan, N. P.

    2005-12-01

    Most investigations into savanna vegetation dynamics have focused either on tree-grass partitioning of water resources or on the effects of disturbances such as fire and herbivory on vegetation structure. Few studies have focused exclusively on tree-tree competition as a mechanism structuring savanna vegetation. The studies that have considered tree-tree competition have used nearest neighborhood methods to infer competition from the spatial pattern of trees, and the results of these studies for savannas have been mixed. However, no substantive work has studied tree-tree competition in savannas using the self-thinning concept, which is surprising since the concept is so heavily used in forest ecology. The self-thinning concept is a power law scaling relationship between mean size and density, with the intercept characterizing the carrying capacity of the system and the slope relating size-dependent resource use. Sankaran et al. (2005) have recently shown a pronounced linear relationship between average annual precipitation and maximum tree cover for a large number of savanna sites in Africa. We propose that tree-tree competition may be a likely mechanism generating the precipitation-rainfall pattern and that a self-thinning analysis can be helpful to further explain the relationship. Here, we examine self-thinning in savannas along a strong rainfall gradient in Kruger National Park, South Africa. The rainfall gradient varies from 750 mm annual average precipitation in the southeastern portion of the park to approximately 350 mm in the far north. The park also has a pronounced soil divide, with the western half of the park largely existing on granitic substrate and the eastern portion of the park on basalt. The study makes use of long-term fire-suppressed plots, where fire has been excluded for over 50 years but canopy cover levels are as low as 30 percent. Results presented show that the intercept increases uniformly along the rainfall gradient, but that the

  6. The independent and interactive effects of tree-tree establishment competition and fire on savanna structure and dynamics.

    PubMed

    Calabrese, Justin M; Vazquez, Federico; López, Cristóbal; San Miguel, Maxi; Grimm, Volker

    2010-03-01

    Savanna ecosystems are widespread and economically important and harbor considerable biodiversity. Despite extensive study, the mechanisms regulating savanna tree populations are not well understood. Recent empirical work suggests that both tree-tree competition and fire are key factors in semiarid to mesic savannas, but the potential for competition to structure savannas, particularly in interaction with fire, has received little theoretical attention. We develop a minimalistic and analytically tractable stochastic cellular automaton to study the individual and combined effects of these two factors on savannas. We find that while competition often substantially depresses tree density, fire generally has little effect but can drive tree extinction in extreme scenarios. When combined, competition and fire interact nonlinearly with strong negative consequences for tree density. This novel result may help explain observed variability among apparently similar savannas in their response to fire. Paradoxically, this interaction could also render the presence of competition more difficult to detect in empirical studies because fire can override the characteristic regular spacing driven by competition and lead instead to clustering.

  7. Tree-grass competition for soil water in arid and semiarid savannas: The role of rainfall intermittency

    NASA Astrophysics Data System (ADS)

    D'Onofrio, Donatella; Baudena, Mara; D'Andrea, Fabio; Rietkerk, Max; Provenzale, Antonello

    2015-01-01

    Arid and semiarid savannas are characterized by the coexistence of trees and grasses in water limited conditions. As in all dry lands, also in these savannas rainfall is highly intermittent. In this work, we develop and use a simple implicit-space model to conceptually explore how precipitation intermittency influences tree-grass competition and savanna occurrence. The model explicitly includes soil moisture dynamics, and life-stage structure of the trees. Assuming that water availability affects the ability of both plant functional types to colonize new space and that grasses outcompete tree seedlings, the model is able to predict the expected sequence of grassland, savanna, and forest along a range of mean annual rainfall. In addition, rainfall intermittency allows for tree-grass coexistence at lower mean annual rainfall values than for constant precipitation. Comparison with observations indicates that the model, albeit very simple, is able to capture some of the essential dynamical processes of natural savannas. The results suggest that precipitation intermittency affects savanna occurrence and structure, indicating a new point of view for reanalyzing observational data from the literature.

  8. The Holocene landscape development of the Gareja region in eastern Georgia - a fluvial approach

    NASA Astrophysics Data System (ADS)

    Sukhishvili, Lasha; Elashvili, Mikheil; Janelidze, Zurab; Kikvadze, Bagrat; Navrozashvili, Levan; von Suchodoletz, Hans

    2013-04-01

    The semi-arid Gareja region in the Iori Highland in the southeastern part of the Republic of Georgia is characterized by an annual precipitation < 500 mm and shows an open steppic landscape today. As is known from historical sources, the landscape showed the same character already during the 6th century AD when the Gareja monastery located in the center of the region was founded by Assyrian monks. However, archaeological research carried out during the Soviet Period showed that there were dozens of settlements of bronze and iron age in this region almost devoid of water resources today, hinting to some sources of fresh water allowing people to live there during those periods. Furthermore, former archaeobotanical studies assume that the region was covered by forests instead of steppes during the past, although there is no final proof yet. The goal of this study is to shed light on the development of the palaeo-landscape during the prehistoric period and thus to address some of the issues described above. To do so, our work is based on the network of episodic streams that cross the region, running from the Iori mountains towards the Mtkvari (Kura) river as the main gaining stream of the region. Using rain water flow direction modeling in GIS we determined the main fluvial courses according to their. This pattern was compared with that of prehistoric settlements known from archaeologic studies, in order to get information about the possible perennial character of some rivers during the past. Furthermore, we did first investigations of outcrops with fluvial sediments found along some of such fluvial courses: Based on stratigraphic observations, pedologic investigations of potential palaeosols as indicators of landscape stability as well as on first numerical datings, we started to unravel the fluvial pattern of that region.

  9. Predicted avian responses to bioenergy development scenarios in an intensive agricultural landscape

    USGS Publications Warehouse

    Uden, Daniel R.; Allen, Craig R.; Mitchell, Rob B.; McCoy, Tim D.; Guan, Qingfeng

    2015-01-01

    Conversion of native prairie to agriculture has increased food and bioenergy production but decreased wildlife habitat. However, enrollment of highly erodible cropland in conservation programs has compensated for some grassland loss. In the future, climate change and production of second-generation perennial biofuel crops could further transform agricultural landscapes and increase or decrease grassland area. Switchgrass (Panicum virgatum) is an alternative biofuel feedstock that may be economically and environmentally superior to maize (Zea mays) grain for ethanol production on marginally productive lands. Switchgrass could benefit farmers economically and increase grassland area, but there is uncertainty as to how conversions between rowcrops, switchgrass monocultures and conservation grasslands might occur and affect wildlife. To explore potential impacts on grassland birds, we developed four agricultural land-use change scenarios for an intensively cultivated landscape, each driven by potential future climatic changes and ensuing irrigation limitations, ethanol demand, commodity prices, and continuation of a conservation program. For each scenario, we calculated changes in area for landcover classes and predicted changes in grassland bird abundances. Overall, birds responded positively to the replacement of rowcrops with switchgrass and negatively to the conversion of conservation grasslands to switchgrass or rowcrops. Landscape context and interactions between climate, crop water use, and irrigation availability could influence future land-use, and subsequently, avian habitat quality and quantity. Switchgrass is likely to provide higher quality avian habitat than rowcrops but lower quality habitat than conservation grasslands, and therefore, may most benefit birds in heavily cultivated, irrigation dependent landscapes under warmer and drier conditions, where economic profitability may also encourage conversions to drought tolerant bioenergy feedstocks.

  10. Modeling the distribution of migratory bird stopovers to inform landscape-scale siting of wind development.

    PubMed

    Pocewicz, Amy; Estes-Zumpf, Wendy A; Andersen, Mark D; Copeland, Holly E; Keinath, Douglas A; Griscom, Hannah R

    2013-01-01

    Conservation of migratory birds requires understanding the distribution of and potential threats to their migratory habitats. However, although migratory birds are protected under international treaties, few maps have been available to represent migration at a landscape scale useful to target conservation efforts or inform the siting of wind energy developments that may affect migratory birds. To fill this gap, we developed models that predict where four groups of birds concentrate or stopover during their migration through the state of Wyoming, USA: raptors, wetland, riparian and sparse grassland birds. The models were based on existing literature and expert knowledge concerning bird migration behavior and ecology and validated using expert ratings and known occurrences. There was significant agreement between migratory occurrence data and migration models for all groups except raptors, and all models ranked well with experts. We measured the overlap between the migration concentration models and a predictive model of wind energy development to assess the potential exposure of migratory birds to wind development and illustrate the utility of migratory concentration models for landscape-scale planning. Wind development potential is high across 15% of Wyoming, and 73% of this high potential area intersects important migration concentration areas. From 5.2% to 18.8% of each group's important migration areas was represented within this high wind potential area, with the highest exposures for sparse grassland birds and the lowest for riparian birds. Our approach could be replicated elsewhere to fill critical data gaps and better inform conservation priorities and landscape-scale planning for migratory birds.

  11. Modeling the Distribution of Migratory Bird Stopovers to Inform Landscape-Scale Siting of Wind Development

    PubMed Central

    Pocewicz, Amy; Estes-Zumpf, Wendy A.; Andersen, Mark D.; Copeland, Holly E.; Keinath, Douglas A.; Griscom, Hannah R.

    2013-01-01

    Conservation of migratory birds requires understanding the distribution of and potential threats to their migratory habitats. However, although migratory birds are protected under international treaties, few maps have been available to represent migration at a landscape scale useful to target conservation efforts or inform the siting of wind energy developments that may affect migratory birds. To fill this gap, we developed models that predict where four groups of birds concentrate or stopover during their migration through the state of Wyoming, USA: raptors, wetland, riparian and sparse grassland birds. The models were based on existing literature and expert knowledge concerning bird migration behavior and ecology and validated using expert ratings and known occurrences. There was significant agreement between migratory occurrence data and migration models for all groups except raptors, and all models ranked well with experts. We measured the overlap between the migration concentration models and a predictive model of wind energy development to assess the potential exposure of migratory birds to wind development and illustrate the utility of migratory concentration models for landscape-scale planning. Wind development potential is high across 15% of Wyoming, and 73% of this high potential area intersects important migration concentration areas. From 5.2% to 18.8% of each group’s important migration areas was represented within this high wind potential area, with the highest exposures for sparse grassland birds and the lowest for riparian birds. Our approach could be replicated elsewhere to fill critical data gaps and better inform conservation priorities and landscape-scale planning for migratory birds. PMID:24098379

  12. Bud protection: a key trait for species sorting in a forest-savanna mosaic.

    PubMed

    Charles-Dominique, Tristan; Beckett, Heath; Midgley, Guy F; Bond, William J

    2015-09-01

    Contrasting fire regimes maintain patch mosaics of savanna, thicket and forest biomes in many African subtropical landscapes. Species dominating each biome are thus expected to display distinct fire-related traits, commonly thought to be bark related. Recent Australian savanna research suggests that bud position, not bark protection alone, determines fire resilience via resprouting. We tested first how bud position influences resprouting ability in 17 tree species. We then compared the effect of both bark-related protection and bud position on the distribution of 63 tree species in 253 transects in all three biomes. Tree species with buds positioned deep under bark had a higher proportion of post-fire aboveground shoot resprouting. Species with low bud protection occurred in fire-prone biomes only if they could root-sucker. The effect of bud protection was supported by a good relationship between species bud protection and distribution across a gradient of fire frequency. Bud protection and high bark production are required to survive frequent fires in savanna. Forests are fire refugia hosting species with little or no bud protection and thin bark. Root-suckering species occur in the three biomes, suggesting that fire is not the only factor filtering this functional type.

  13. Bud protection: a key trait for species sorting in a forest-savanna mosaic.

    PubMed

    Charles-Dominique, Tristan; Beckett, Heath; Midgley, Guy F; Bond, William J

    2015-09-01

    Contrasting fire regimes maintain patch mosaics of savanna, thicket and forest biomes in many African subtropical landscapes. Species dominating each biome are thus expected to display distinct fire-related traits, commonly thought to be bark related. Recent Australian savanna research suggests that bud position, not bark protection alone, determines fire resilience via resprouting. We tested first how bud position influences resprouting ability in 17 tree species. We then compared the effect of both bark-related protection and bud position on the distribution of 63 tree species in 253 transects in all three biomes. Tree species with buds positioned deep under bark had a higher proportion of post-fire aboveground shoot resprouting. Species with low bud protection occurred in fire-prone biomes only if they could root-sucker. The effect of bud protection was supported by a good relationship between species bud protection and distribution across a gradient of fire frequency. Bud protection and high bark production are required to survive frequent fires in savanna. Forests are fire refugia hosting species with little or no bud protection and thin bark. Root-suckering species occur in the three biomes, suggesting that fire is not the only factor filtering this functional type. PMID:25856385

  14. Wyoming Landscape Conservation Initiative—A case study in partnership development

    USGS Publications Warehouse

    D'Erchia, Frank

    2016-10-21

    The Wyoming Landscape Conservation Initiative (WLCI) is a successful example of collaboration between science and natural resource management at the landscape scale. In southwestern Wyoming, expanding energy and mineral development, urban growth, and other changes in land use over recent decades, combined with landscape-scale drivers such as climate change and invasive species, have presented compelling challenges to resource managers and a diverse group of Federal, State, industry, and non-governmental organizations, as well as citizen stakeholders. To address these challenges, the WLCI was established as a collaborative forum and interagency partnership to develop and implement science-based conservation actions. About a decade after being established, this report documents the establishment and history of the WLCI, focusing on the path to success of the initiative and providing insights and details that may be useful in developing similar partnerships in other locations. Not merely retrospective, the elements of the WLCI that are presented herein are still in play, still evolving, and still contributing to the resolution of compelling conservation challenges in the Western United States.The U.S. Geological Survey has developed many successful longstanding partnerships, of which the WLCI is one example.“As the Nation’s largest water, earth, and biological science and civilian mapping agency, the U.S. Geological Survey collects, monitors, analyzes, and provides scientific understanding about natural resource conditions, issues, and problems. The diversity of our scientific expertise enables us to carry out large-scale, multi-disciplinary investigations and provide impartial scientific information to resource managers, planners, and other customers” (U.S. Geological Survey, 2016).

  15. Field Investigations of Landscape Development in southeast Spain for use in Modeling Holocene (8,000 - 1,500 yr) Agropastoral Landuse and Landscape Interactions

    NASA Astrophysics Data System (ADS)

    Dimaggio, E. N.; La Roca, N.; Arrowsmith, J. R.; Diez-Castillo, A.; Bernabeu, J.; Barton, C. M.

    2007-12-01

    Dramatic changes in land use were associated with the rise of agriculture in the mid Holocene in the Mediterranean region. Both the surface properties and the drainage networks were changed. Along with the direct modifications to surface properties (vegetation removal and change, sediment liberation and compaction) and consequent drainage alteration (terracing, canals), up and downstream responses in the watersheds communicated these changes throughout the landscape. The magnitude, rate, and feedbacks with the growing human populations are critical questions in our effort to assess human-landscape interactions. To investigate these relationships, recent field work in the Penaguila Valley in southeast Spain included landform mapping, alluvial deposit description, and sample collection emphasizing areas of active erosion, remnant land surfaces and their relation to archaeological sites. We have updated our geomorphic maps by refining the delineation of alluvial terraces, steep-walled (40m deep) drainages ("barrancos"), and hollows ("barrancos de fondo plano"). Hollows are curved, elongate, flat-bottomed gullies with steep walls (2-30m tall) and extend headward from the main barrancos. This work enables more accurate terrace correlations necessary for both landscape evolution modeling and interpretation of the development history of the basin. Alluvial terraces are crucial to this research because they record periods of past stable topography. In the Penaguila, sites dating back to late Mesolithic and early Neolithic (around 6600 BP) and subsequent periods (Chalcolithic and Bronze Age) are exposed on a prominent terrace surface mapped as Terrace A. This broad low relief surface is scarred by deep barrancos and hollow formation that expose bedrock marls and overlying alluvial deposits. Stratigraphic profiles and texture analyses of Terrace A deposits reveal overland flow facies and channel networks in reworked and CaCO3-encrusted marls, and several organic

  16. Grassland, shrubland and savanna stewardship: where do we go from here?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Scientific efforts to understand grasslands, shrublands and savannas and thereby develop sustainable management practices are roughly 100 years old. What have we learned in that time? Several assumptions made by scientists and policymakers early in the 20th century have proved mistaken, resulting in...

  17. Relationships between brittle deformation, weathering and landscape development during the Mesozoic in Scandinavia

    NASA Astrophysics Data System (ADS)

    Viola, Giulio; Fredin, Ola; Scheiber, Thomas; Brönner, Marco; Zwingmann, Horst; Knies, Jochen

    2015-04-01

    Pre-Quaternary weathering is generally considered responsible for the formation of rather common, yet poorly constrained, saprolite remnants onshore Scandinavia. Understanding the genesis of these weathering products and placing them into an adequate tectonic and climatic framework is currently of great interest for two reasons. First, the origin of the landscape in Scandinavia, where deep weathering is thought to have played a fundamental role, is the subject of a lively debate hinged around the number and age of episodes of regional uplift and denudation. Second, there have been recent discoveries of major hydrocarbon reserves within weathered basement highs in the North Sea immediately offshore Norway. Invariably, these basement highs are also severely fractured and faulted and a genetic relationship between brittle deformation, weathering and landscape development is suggested by a number of observations. Within the recently launched BASE project, we aim to establish a temporal and conceptual framework for brittle tectonics, weathering patterns and landscape evolution by constraining the age and rate of weathering and by isotopically dating selected faults intimately linked to weathered basement blocks. Initial efforts have focused on fractured and weathered granitoid rocks of Caledonian age exposed in western Norway. There, saprolites are found as small pockets within a joint valley landscape, which was likely stripped by Quaternary glaciations. Saprolite distribution is mostly structurally controlled as deep weathering and alteration occur predominantly in association with fractures and along faulted corridors. Structural analysis has allowed the geometric and kinematic interpretation of the exposed fracture and fault patterns and we could assign them to a number of distinct brittle deformation episodes characterised by robust paleostress tensors. The K-Ar dating of illites separated from structurally constrained faults indicates a long strain localization

  18. Ranking landscape development scenarios affecting natterjack toad (Bufo calamita) population dynamics in Central Poland.

    PubMed

    Franz, Kamila W; Romanowski, Jerzy; Johst, Karin; Grimm, Volker

    2013-01-01

    When data are limited it is difficult for conservation managers to assess alternative management scenarios and make decisions. The natterjack toad (Bufo calamita) is declining at the edges of its distribution range in Europe and little is known about its current distribution and abundance in Poland. Although different landscape management plans for central Poland exist, it is unclear to what extent they impact this species. Based on these plans, we investigated how four alternative landscape development scenarios would affect the total carrying capacity and population dynamics of the natterjack toad. To facilitate decision-making, we first ranked the scenarios according to their total carrying capacity. We used the software RAMAS GIS to determine the size and location of habitat patches in the landscape. The estimated carrying capacities were very similar for each scenario, and clear ranking was not possible. Only the reforestation scenario showed a marked loss in carrying capacity. We therefore simulated metapopulation dynamics with RAMAS taking into account dynamical processes such as reproduction and dispersal and ranked the scenarios according to the resulting species abundance. In this case, we could clearly rank the development scenarios. We identified road mortality of adults as a key process governing the dynamics and separating the different scenarios. The renaturalisation scenario clearly ranked highest due to its decreased road mortality. Taken together our results suggest that road infrastructure development might be much more important for natterjack toad conservation than changes in the amount of habitat in the semi-natural river valley. We gained these insights by considering both the resulting metapopulation structure and dynamics in the form of a PVA. We conclude that the consideration of dynamic processes in amphibian conservation management may be indispensable for ranking management scenarios.

  19. Ranking Landscape Development Scenarios Affecting Natterjack Toad (Bufo calamita) Population Dynamics in Central Poland

    PubMed Central

    Franz, Kamila W.; Romanowski, Jerzy; Johst, Karin; Grimm, Volker

    2013-01-01

    When data are limited it is difficult for conservation managers to assess alternative management scenarios and make decisions. The natterjack toad (Bufo calamita) is declining at the edges of its distribution range in Europe and little is known about its current distribution and abundance in Poland. Although different landscape management plans for central Poland exist, it is unclear to what extent they impact this species. Based on these plans, we investigated how four alternative landscape development scenarios would affect the total carrying capacity and population dynamics of the natterjack toad. To facilitate decision-making, we first ranked the scenarios according to their total carrying capacity. We used the software RAMAS GIS to determine the size and location of habitat patches in the landscape. The estimated carrying capacities were very similar for each scenario, and clear ranking was not possible. Only the reforestation scenario showed a marked loss in carrying capacity. We therefore simulated metapopulation dynamics with RAMAS taking into account dynamical processes such as reproduction and dispersal and ranked the scenarios according to the resulting species abundance. In this case, we could clearly rank the development scenarios. We identified road mortality of adults as a key process governing the dynamics and separating the different scenarios. The renaturalisation scenario clearly ranked highest due to its decreased road mortality. Taken together our results suggest that road infrastructure development might be much more important for natterjack toad conservation than changes in the amount of habitat in the semi-natural river valley. We gained these insights by considering both the resulting metapopulation structure and dynamics in the form of a PVA. We conclude that the consideration of dynamic processes in amphibian conservation management may be indispensable for ranking management scenarios. PMID:23734223

  20. Window area and development drive spatial variation in bird-window collisions in an urban landscape.

    PubMed

    Hager, Stephen B; Cosentino, Bradley J; McKay, Kelly J; Monson, Cathleen; Zuurdeeg, Walt; Blevins, Brian

    2013-01-01

    Collisions with windows are an important human-related threat to birds in urban landscapes. However, the proximate drivers of collisions are not well understood, and no study has examined spatial variation in mortality in an urban setting. We hypothesized that the number of fatalities at buildings varies with window area and habitat features that influence avian community structure. In 2010 we documented bird-window collisions (BWCs) and characterized avian community structure at 20 buildings in an urban landscape in northwestern Illinois, USA. For each building and season, we conducted 21 daily surveys for carcasses and nine point count surveys to estimate relative abundance, richness, and diversity. Our sampling design was informed by experimentally estimated carcass persistence times and detection probabilities. We used linear and generalized linear mixed models to evaluate how habitat features influenced community structure and how mortality was affected by window area and factors that correlated with community structure. The most-supported model was consistent for all community indices and included effects of season, development, and distance to vegetated lots. BWCs were related positively to window area and negatively to development. We documented mortalities for 16/72 (22%) species (34 total carcasses) recorded at buildings, and BWCs were greater for juveniles than adults. Based on the most-supported model of BWCs, the median number of annual predicted fatalities at study buildings was 3 (range = 0-52). These results suggest that patchily distributed environmental resources and levels of window area in buildings create spatial variation in BWCs within and among urban areas. Current mortality estimates place little emphasis on spatial variation, which precludes a fundamental understanding of the issue. To focus conservation efforts, we illustrate how knowledge of the structural and environmental factors that influence bird-window collisions can be used to

  1. Window area and development drive spatial variation in bird-window collisions in an urban landscape.

    PubMed

    Hager, Stephen B; Cosentino, Bradley J; McKay, Kelly J; Monson, Cathleen; Zuurdeeg, Walt; Blevins, Brian

    2013-01-01

    Collisions with windows are an important human-related threat to birds in urban landscapes. However, the proximate drivers of collisions are not well understood, and no study has examined spatial variation in mortality in an urban setting. We hypothesized that the number of fatalities at buildings varies with window area and habitat features that influence avian community structure. In 2010 we documented bird-window collisions (BWCs) and characterized avian community structure at 20 buildings in an urban landscape in northwestern Illinois, USA. For each building and season, we conducted 21 daily surveys for carcasses and nine point count surveys to estimate relative abundance, richness, and diversity. Our sampling design was informed by experimentally estimated carcass persistence times and detection probabilities. We used linear and generalized linear mixed models to evaluate how habitat features influenced community structure and how mortality was affected by window area and factors that correlated with community structure. The most-supported model was consistent for all community indices and included effects of season, development, and distance to vegetated lots. BWCs were related positively to window area and negatively to development. We documented mortalities for 16/72 (22%) species (34 total carcasses) recorded at buildings, and BWCs were greater for juveniles than adults. Based on the most-supported model of BWCs, the median number of annual predicted fatalities at study buildings was 3 (range = 0-52). These results suggest that patchily distributed environmental resources and levels of window area in buildings create spatial variation in BWCs within and among urban areas. Current mortality estimates place little emphasis on spatial variation, which precludes a fundamental understanding of the issue. To focus conservation efforts, we illustrate how knowledge of the structural and environmental factors that influence bird-window collisions can be used to

  2. Window Area and Development Drive Spatial Variation in Bird-Window Collisions in an Urban Landscape

    PubMed Central

    Hager, Stephen B.; Cosentino, Bradley J.; McKay, Kelly J.; Monson, Cathleen; Zuurdeeg, Walt; Blevins, Brian

    2013-01-01

    Collisions with windows are an important human-related threat to birds in urban landscapes. However, the proximate drivers of collisions are not well understood, and no study has examined spatial variation in mortality in an urban setting. We hypothesized that the number of fatalities at buildings varies with window area and habitat features that influence avian community structure. In 2010 we documented bird-window collisions (BWCs) and characterized avian community structure at 20 buildings in an urban landscape in northwestern Illinois, USA. For each building and season, we conducted 21 daily surveys for carcasses and nine point count surveys to estimate relative abundance, richness, and diversity. Our sampling design was informed by experimentally estimated carcass persistence times and detection probabilities. We used linear and generalized linear mixed models to evaluate how habitat features influenced community structure and how mortality was affected by window area and factors that correlated with community structure. The most-supported model was consistent for all community indices and included effects of season, development, and distance to vegetated lots. BWCs were related positively to window area and negatively to development. We documented mortalities for 16/72 (22%) species (34 total carcasses) recorded at buildings, and BWCs were greater for juveniles than adults. Based on the most-supported model of BWCs, the median number of annual predicted fatalities at study buildings was 3 (range = 0–52). These results suggest that patchily distributed environmental resources and levels of window area in buildings create spatial variation in BWCs within and among urban areas. Current mortality estimates place little emphasis on spatial variation, which precludes a fundamental understanding of the issue. To focus conservation efforts, we illustrate how knowledge of the structural and environmental factors that influence bird-window collisions can be used

  3. Management and development of land in the name of the Green Economy: planning, landscape, efficiency, biodiversity

    NASA Astrophysics Data System (ADS)

    Benvenuti, Paolo

    2016-04-01

    Promoting sustainable economic development is the basis of the Green Economy: a new vision of Agriculture, Environmental and Regional policy, shared by the wine sector, especially on some crucial issues, such as reducing the consumption of agricultural land, recognition as economically important of the green agricultural production space, spreading of organic farming, adoption of good agricultural practices. Sustainability, in fact , is not just about the use of analysis tools (carbonfoot print, Waterfoot print, etc .) but is about innovations to be introduced in the entire production process, protection of biodiversity, ethic work in the vineyard and winery. It means to disseminate as much as possible all those practices that can enable a more efficient land management also considering the recent climate changes: introduction of agro-energy and precision agriculture, rational use of water resources, creation of an observatory on temperatures and an interactive mapping system, viticultural zoning and municipal planning to make concrete balance between vitality in agronomic sector and landscape quality. Realizing such a regional geopedological mapping about agricultural soil, will allow companies to display a real-time access to all the data needed for a sustainable management of the funds, not only it would be an important tool to support the technical choices of farmers, enhancing their potential and optimizing production in relation to the current climate crisis, but would have a strong impact in terms of managing and saving water and energy resources. A strong efficacy in this context should be recognized at the "Urban Regulation Plans of the Wine Cities", which have developed since 2007 on the base of the guidelines promoted by the Italian Association Città del Vino, in order to enhance the quality of wine districts. The foundations of this multidisciplinary tool are based on: • in-depth knowledge of the characteristics of the wine territory; • unity and

  4. Environmental resource management of the Munduruku savanna

    SciTech Connect

    Sheffler, E.M.; Southwick, E.E.

    1984-05-01

    For 13 years, the Munduruku were observed living in the savanna region located in South America in the Brazilian state of Para. The area is near the point where the states of Para, Amazonas, and Mato Grosso join their borders, and is utilized by about 200-300 Munduruku Amerindians. Their subsistence staple is manioc (a cassava), with fruits and meat included in the diet. Gold mining by Brazilians is a disruptive element in the resource management of the savanna habitat on the rim of the Amazon Basin. Direct and indirect results of mining interference are described. A study of the manner in which the Munduruku on the Cururu River (a tributary of the Tapajos) have handled the potentially disruptive rubber tapping suggests possible ways of reversing the interference. Several courses of action are discussed. 14 references, 3 figures, 2 tables.

  5. Environmental resource management on the Munduruku savanna

    NASA Astrophysics Data System (ADS)

    Sheffler, E. Margaret; Southwick, Edward E.

    1984-05-01

    For 13 years, the Munduruku were observed living in the savanna region located in South America in the Brazilian state of Pará. The area is near the point where the states of Pará, Amazonas, and Mato Grosso join their borders, and is utilized by about 200 300 Munduruku Amerindians. Their subsistence staple is manioc (a cassava), with fruits and meat included in the diet. Gold mining by Brazilians is a disruptive element in the resource management of the savanna habitat on the rim of the Amazon Basin. Direct and indirect results of mining interference are described. A study of the manner in which the Munduruku on the Cururu River (a tributary of the Tapajós) have handled the potentially disruptive rubber tapping suggests possible ways of reversing the interference. Several courses of action are discussed.

  6. The Campus Landscape.

    ERIC Educational Resources Information Center

    du Von, Jay

    1966-01-01

    All across the country, landscaping and site development are coming to the fore as essential and integral parts of university planning and development. This reprint concentrates on the function of landscape architecture, and briefly examines some of the major responsibilities of the landscape architect in planning a campus. Included are--(1)…

  7. Examining cultural drifts in artworks through history and development: cultural comparisons between Japanese and western landscape paintings and drawings

    PubMed Central

    Nand, Kristina; Masuda, Takahiko; Senzaki, Sawa; Ishii, Keiko

    2014-01-01

    Research on cultural products suggest that there are substantial cultural variations between East Asian and European landscape masterpieces and contemporary members' landscape artwork (Masuda et al., 2008c), and that these cultural differences in drawing styles emerge around the age of 8 (Senzaki et al., 2014b). However, culture is not static. To explore the dynamics of historical and ontogenetic influence on artistic expressions, we examined (1) 17–20th century Japanese and Western landscape masterpieces, and (2) cross-sectional adolescent data in landscape artworks alongside previous findings of elementary school-aged children, and undergraduates. The results showed cultural variations in artworks and masterpieces as well as substantial “cultural drifts” (Herskovits, 1948) where at certain time periods in history and in development, people's expressions deviated from culturally default patterns but occasionally returned to its previous state. The bidirectional influence of culture and implications for furthering the discipline of cultural psychology will be discussed. PMID:25285085

  8. Examining cultural drifts in artworks through history and development: cultural comparisons between Japanese and western landscape paintings and drawings.

    PubMed

    Nand, Kristina; Masuda, Takahiko; Senzaki, Sawa; Ishii, Keiko

    2014-01-01

    Research on cultural products suggest that there are substantial cultural variations between East Asian and European landscape masterpieces and contemporary members' landscape artwork (Masuda et al., 2008c), and that these cultural differences in drawing styles emerge around the age of 8 (Senzaki et al., 2014b). However, culture is not static. To explore the dynamics of historical and ontogenetic influence on artistic expressions, we examined (1) 17-20th century Japanese and Western landscape masterpieces, and (2) cross-sectional adolescent data in landscape artworks alongside previous findings of elementary school-aged children, and undergraduates. The results showed cultural variations in artworks and masterpieces as well as substantial "cultural drifts" (Herskovits, 1948) where at certain time periods in history and in development, people's expressions deviated from culturally default patterns but occasionally returned to its previous state. The bidirectional influence of culture and implications for furthering the discipline of cultural psychology will be discussed. PMID:25285085

  9. Crown cover chart for oak savannas. Forest Service technical brief

    SciTech Connect

    Law, J.R.; Johnson, P.S.; Houf, G.

    1994-07-01

    Although oak savannas have been defined in many ways, they are characterized by scattered trees, largely comprised of oaks, and a sparse ground layer rich in grasses and forbs. The crown cover chart can be used to estimate the crown cover of trees as a percent of total area. Potential applications of the chart include monitoring changes in savanna crown cover, determining needed reductions in crown cover, and defining the savanna state. in restoring savannas that have grown into closed canopy stands, one can use the chart to estimate initial crown cover before restoration work is begun and again after crown cover has been reduced.

  10. Seasonal distribution of African savanna fires

    NASA Technical Reports Server (NTRS)

    Cahoon, Donald R., Jr.; Stocks, Brian J.; Levine, Joel S.; Cofer, Wesley R., III; O'Neill, Katherine P.

    1992-01-01

    The temporal and spatial distribution of savanna fires over the entire African continent, as determined from nighttime satellite imagery, is described. It is found that, contrary to expectations, most fires are left to burn uncontrolled, so that there is no strong diurnal cycle in the fire frequency. The knowledge gained from this study regarding the distribution and variability of fires is helpful in the monitoring of climatically important trace gases emitted from burning biomass.

  11. Influences of roads and development on bird communities in protected Chihuahuan Desert landscapes

    USGS Publications Warehouse

    Gutzwiller, K.J.; Barrow, W.C.

    2003-01-01

    Our objective was to improve knowledge about effects of broad-scale road and development variables on bird communities in protected desert landscapes. Bird species richness and the relative abundance or probability of occurrence of many species were significantly associated with total length of roads within each of two spatial extents (1- and 2-km radii), distance to the nearest road, distance to the nearest development, or the two-way interactions of these variables. Regression models reflected non-linear relations, interaction effects, spatial-extent effects, and interannual variation. Road and development effects warrant special attention in protected areas because such places may be important sources of indigenous bird communities in a region.

  12. A temporary focus of savanna species of the Simulium damnosum complex in the forest zone of Liberia.

    PubMed

    Garms, R; Cheke, R A; Sachs, R

    1991-09-01

    Savanna species of the Simulium damnosum complex, the major vectors of the blinding savanna type of onchocerciasis, were considered to be rare in Liberia, until the dry season of 1988. In 1988 they became a serious nuisance, biting people at the Bong iron ore mine within the rain forest zone. S. damnosum s.str. and S. sirbanum were found breeding, in association with S. adersi a non man-biting savanna species, in a stream emerging from the mine's tailings pond. The local forest species were extremely rare in this stream. The water of the stream was characterized by an increased hardness and higher temperatures in comparison with those of natural watercourses in the area. The mass occurrence of flies was probably related to expansions of the tailings ponds, when rich nutrition was provided for the blackfly larvae by the decaying forests submerged by the rising water levels. The phenomenon did not recur in 1989 when only a few savanna flies were caught, and none were seen in the dry season of 1990. Although it is not known why the artificial environment of the tailings ponds was so attractive for the savanna species the events clearly demonstrated that savanna flies seasonally invading the area, possibly aided by the northeasterly harmattan winds, can become established in the rain forest zone if suitable conditions are met. No infections with Onchocerca volvulus were found in more than 1000 flies caught by vector collectors but, after experimental infection with the local forest strain, a few parasites developed to the infective stage. As yet there is no evidence that the occurrence of savanna flies in the rain forest zone of Liberia was of epidemiological significance.

  13. Evaluation of urban sprawl and urban landscape pattern in a rapidly developing region.

    PubMed

    Lv, Zhi-Qiang; Dai, Fu-Qiang; Sun, Cheng

    2012-10-01

    Urban sprawl is a worldwide phenomenon happening particularly in rapidly developing regions. A study on the spatiotemporal characteristics of urban sprawl and urban pattern is useful for the sustainable management of land management and urban land planning. The present research explores the spatiotemporal dynamics of urban sprawl in the context of a rapid urbanization process in a booming economic region of southern China from 1979 to 2005. Three urban sprawl types are distinguished by analyzing overlaid urban area maps of two adjacent study years which originated from the interpretation of remote sensed images and vector land use maps. Landscape metrics are used to analyze the spatiotemporal pattern of urban sprawl for each study period. Study results show that urban areas have expanded dramatically, and the spatiotemporal landscape pattern configured by the three sprawl types changed obviously. The different sprawl type patterns in five study periods have transformed significantly, with their proportions altered both in terms of quantity and of location. The present research proves that urban sprawl quantification and pattern analysis can provide a clear perspective of the urbanization process during a long time period. Particularly, the present study on urban sprawl and sprawl patterns can be used by land use and urban planners.

  14. Evaluation of urban sprawl and urban landscape pattern in a rapidly developing region.

    PubMed

    Lv, Zhi-Qiang; Dai, Fu-Qiang; Sun, Cheng

    2012-10-01

    Urban sprawl is a worldwide phenomenon happening particularly in rapidly developing regions. A study on the spatiotemporal characteristics of urban sprawl and urban pattern is useful for the sustainable management of land management and urban land planning. The present research explores the spatiotemporal dynamics of urban sprawl in the context of a rapid urbanization process in a booming economic region of southern China from 1979 to 2005. Three urban sprawl types are distinguished by analyzing overlaid urban area maps of two adjacent study years which originated from the interpretation of remote sensed images and vector land use maps. Landscape metrics are used to analyze the spatiotemporal pattern of urban sprawl for each study period. Study results show that urban areas have expanded dramatically, and the spatiotemporal landscape pattern configured by the three sprawl types changed obviously. The different sprawl type patterns in five study periods have transformed significantly, with their proportions altered both in terms of quantity and of location. The present research proves that urban sprawl quantification and pattern analysis can provide a clear perspective of the urbanization process during a long time period. Particularly, the present study on urban sprawl and sprawl patterns can be used by land use and urban planners. PMID:22095203

  15. Developing a participatory process to include ecosystem services in landscape planing

    NASA Astrophysics Data System (ADS)

    Onaindia, Miren; Palacios-Agundez, Igone; Rodríguez-Loinaz, Gloria; Peña, Lorena; Madariaga, Iosu; Ametzaga, Ibone

    2015-04-01

    This work develops an approach that integrates scientific knowledge on ecosystem services and stakeholders demands to get guidelines for landscape planning strategies in the region of Biscay (Basque Country, northern Spain). In the conducted participatory process, forest multi-functionality was considered as a practicable good alternative. This process identified also a knowledge gap on the synergies and trade-offs between biodiversity, timber production and carbon storage, guiding the directions of the research actions. The results from developed spatial analysis converged with those from the participatory process in the adequacy of promoting, where possible and appropriate, natural forest ecosystems restoration. The ongoing stepwise learning strategy is already showing its effectiveness for decision making, with concrete examples of how the results obtained with the applied approach are being included in planning and decision-making processes.

  16. Learning Landscapes

    ERIC Educational Resources Information Center

    Noyes, Andrew

    2004-01-01

    This article explores the metaphor of learning landscapes, a tool developed in order to map children's experiences of, and attitudes to, learning (mathematics) before and after the transfer from primary to secondary school. Firstly, the continuing problems surrounding school transfer and why a re-examination of this is required are considered.…

  17. Comparing the Ecological Impacts of Wind and Oil & Gas Development: A Landscape Scale Assessment

    PubMed Central

    Jones, Nathan F.; Pejchar, Liba

    2013-01-01

    Energy production in the United States is in transition as the demand for clean and domestic power increases. Wind energy offers the benefit of reduced emissions, yet, like oil and natural gas, it also contributes to energy sprawl. We used a diverse set of indicators to quantify the ecological impacts of oil, natural gas, and wind energy development in Colorado and Wyoming. Aerial imagery was supplemented with empirical data to estimate habitat loss, fragmentation, potential for wildlife mortality, susceptibility to invasion, biomass carbon lost, and water resources. To quantify these impacts we digitized the land-use footprint within 375 plots, stratified by energy type. We quantified the change in impacts per unit area and per unit energy produced, compared wind energy to oil and gas, and compared landscapes with and without energy development. We found substantial differences in impacts between energy types for most indicators, although the magnitude and direction of the differences varied. Oil and gas generally resulted in greater impacts per unit area but fewer impacts per unit energy compared with wind. Biologically important and policy-relevant outcomes of this study include: 1) regardless of energy type, underlying land-use matters and development in already disturbed areas resulted in fewer total impacts; 2) the number and source of potential mortality varied between energy types, however, the lack of robust mortality data limits our ability to use this information to estimate and mitigate impacts; and 3) per unit energy produced, oil and gas extraction was less impactful on an annual basis but is likely to have a much larger cumulative footprint than wind energy over time. This rapid evaluation of landscape-scale energy development impacts could be replicated in other regions, and our specific findings can help meet the challenge of balancing land conservation with society’s demand for energy. PMID:24312296

  18. Comparing the ecological impacts of wind and oil & gas development: a landscape scale assessment.

    PubMed

    Jones, Nathan F; Pejchar, Liba

    2013-01-01

    Energy production in the United States is in transition as the demand for clean and domestic power increases. Wind energy offers the benefit of reduced emissions, yet, like oil and natural gas, it also contributes to energy sprawl. We used a diverse set of indicators to quantify the ecological impacts of oil, natural gas, and wind energy development in Colorado and Wyoming. Aerial imagery was supplemented with empirical data to estimate habitat loss, fragmentation, potential for wildlife mortality, susceptibility to invasion, biomass carbon lost, and water resources. To quantify these impacts we digitized the land-use footprint within 375 plots, stratified by energy type. We quantified the change in impacts per unit area and per unit energy produced, compared wind energy to oil and gas, and compared landscapes with and without energy development. We found substantial differences in impacts between energy types for most indicators, although the magnitude and direction of the differences varied. Oil and gas generally resulted in greater impacts per unit area but fewer impacts per unit energy compared with wind. Biologically important and policy-relevant outcomes of this study include: 1) regardless of energy type, underlying land-use matters and development in already disturbed areas resulted in fewer total impacts; 2) the number and source of potential mortality varied between energy types, however, the lack of robust mortality data limits our ability to use this information to estimate and mitigate impacts; and 3) per unit energy produced, oil and gas extraction was less impactful on an annual basis but is likely to have a much larger cumulative footprint than wind energy over time. This rapid evaluation of landscape-scale energy development impacts could be replicated in other regions, and our specific findings can help meet the challenge of balancing land conservation with society's demand for energy. PMID:24312296

  19. Comparing the ecological impacts of wind and oil & gas development: a landscape scale assessment.

    PubMed

    Jones, Nathan F; Pejchar, Liba

    2013-01-01

    Energy production in the United States is in transition as the demand for clean and domestic power increases. Wind energy offers the benefit of reduced emissions, yet, like oil and natural gas, it also contributes to energy sprawl. We used a diverse set of indicators to quantify the ecological impacts of oil, natural gas, and wind energy development in Colorado and Wyoming. Aerial imagery was supplemented with empirical data to estimate habitat loss, fragmentation, potential for wildlife mortality, susceptibility to invasion, biomass carbon lost, and water resources. To quantify these impacts we digitized the land-use footprint within 375 plots, stratified by energy type. We quantified the change in impacts per unit area and per unit energy produced, compared wind energy to oil and gas, and compared landscapes with and without energy development. We found substantial differences in impacts between energy types for most indicators, although the magnitude and direction of the differences varied. Oil and gas generally resulted in greater impacts per unit area but fewer impacts per unit energy compared with wind. Biologically important and policy-relevant outcomes of this study include: 1) regardless of energy type, underlying land-use matters and development in already disturbed areas resulted in fewer total impacts; 2) the number and source of potential mortality varied between energy types, however, the lack of robust mortality data limits our ability to use this information to estimate and mitigate impacts; and 3) per unit energy produced, oil and gas extraction was less impactful on an annual basis but is likely to have a much larger cumulative footprint than wind energy over time. This rapid evaluation of landscape-scale energy development impacts could be replicated in other regions, and our specific findings can help meet the challenge of balancing land conservation with society's demand for energy.

  20. Drivers of Intensity and Prevalence of Flea Parasitism on Small Mammals in East African Savanna Ecosystems.

    PubMed

    Young, Hillary S; Dirzo, Rodolfo; McCauley, Douglas J; Agwanda, Bernard; Cattaneo, Lia; Dittmar, Katharina; Eckerlin, Ralph P; Fleischer, Robert C; Helgen, Lauren E; Hintz, Ashley; Montinieri, John; Zhao, Serena; Helgen, Kristofer M

    2015-06-01

    The relative importance of environmental factors and host factors in explaining variation in prevalence and intensity of flea parasitism in small mammal communities is poorly established. We examined these relationships in an East African savanna landscape, considering multiple host levels: across individuals within a local population, across populations within species, and across species within a landscape. We sampled fleas from 2,672 small mammals of 27 species. This included a total of 8,283 fleas, with 5 genera and 12 species identified. Across individual hosts within a site, both rodent body mass and season affected total intensity of flea infestation, although the explanatory power of these factors was generally modest (<10%). Across host populations in the landscape, we found consistently positive effects of host density and negative effects of vegetation cover on the intensity of flea infestation. Other factors explored (host diversity, annual rainfall, anthropogenic disturbance, and soil properties) tended to have lower and less consistent explanatory power. Across host species in the landscape, we found that host body mass was strongly positively correlated with both prevalence and intensity of flea parasitism, while average robustness of a host species to disturbance was not correlated with flea parasitism. Cumulatively, these results provide insight into the intricate roles of both host and environmental factors in explaining complex patterns of flea parasitism across landscape mosaics.

  1. Anticipating forest and range land development in central Oregon (USA) for landscape analysis, with an example application involving mule deer.

    PubMed

    Kline, Jeffrey D; Moses, Alissa; Burcsu, Theresa

    2010-05-01

    Forest policymakers, public lands managers, and scientists in the Pacific Northwest (USA) seek ways to evaluate the landscape-level effects of policies and management through the multidisciplinary development and application of spatially explicit methods and models. The Interagency Mapping and Analysis Project (IMAP) is an ongoing effort to generate landscape-wide vegetation data and models to evaluate the integrated effects of disturbances and management activities on natural resource conditions in Oregon and Washington (USA). In this initial analysis, we characterized the spatial distribution of forest and range land development in a four-county pilot study region in central Oregon. The empirical model describes the spatial distribution of buildings and new building construction as a function of population growth, existing development, topography, land-use zoning, and other factors. We used the model to create geographic information system maps of likely future development based on human population projections to inform complementary landscape analyses underway involving vegetation, habitat, and wildfire interactions. In an example application, we use the model and resulting maps to show the potential impacts of future forest and range land development on mule deer (Odocoileus hemionus) winter range. Results indicate significant development encroachment and habitat loss already in 2000 with development located along key migration routes and increasing through the projection period to 2040. The example application illustrates a simple way for policymakers and public lands managers to combine existing data and preliminary model outputs to begin to consider the potential effects of development on future landscape conditions.

  2. Anticipating Forest and Range Land Development in Central Oregon (USA) for Landscape Analysis, with an Example Application Involving Mule Deer

    NASA Astrophysics Data System (ADS)

    Kline, Jeffrey D.; Moses, Alissa; Burcsu, Theresa

    2010-05-01

    Forest policymakers, public lands managers, and scientists in the Pacific Northwest (USA) seek ways to evaluate the landscape-level effects of policies and management through the multidisciplinary development and application of spatially explicit methods and models. The Interagency Mapping and Analysis Project (IMAP) is an ongoing effort to generate landscape-wide vegetation data and models to evaluate the integrated effects of disturbances and management activities on natural resource conditions in Oregon and Washington (USA). In this initial analysis, we characterized the spatial distribution of forest and range land development in a four-county pilot study region in central Oregon. The empirical model describes the spatial distribution of buildings and new building construction as a function of population growth, existing development, topography, land-use zoning, and other factors. We used the model to create geographic information system maps of likely future development based on human population projections to inform complementary landscape analyses underway involving vegetation, habitat, and wildfire interactions. In an example application, we use the model and resulting maps to show the potential impacts of future forest and range land development on mule deer ( Odocoileus hemionus) winter range. Results indicate significant development encroachment and habitat loss already in 2000 with development located along key migration routes and increasing through the projection period to 2040. The example application illustrates a simple way for policymakers and public lands managers to combine existing data and preliminary model outputs to begin to consider the potential effects of development on future landscape conditions.

  3. A model of late quaternary landscape development in the Delaware Valley, New Jersey and Pennsylvania

    NASA Astrophysics Data System (ADS)

    Ridge, John C.; Evenson, Edward B.; Sevon, William D.

    1992-03-01

    In the Delaware Valley of New Jersey and eastern Pennsylvania the late Quaternary history of colluviation, fluvial adjustment, and soil formation is based on the ages of pre-Wisconsinan soils and glacial deposits which are indicated by feld relationships and inferred from mid-latitude climate changes indicated by marine oxygen-isotope records. The area is divided into four terranes characterized by sandstone, gneiss, slate and carbonate rocks. Since the last pre-Wisconsinan glaciation (> 130 ka, inferred to be late Illinoian), each terrane responded differently to chemical and mechanical weathering. During the Sangamon interglacial stage (˜ 130-75 ka) in situ weathering is inferred to have occurred at rates greater than transportation of material which resulted in the formation of deep, highly weathered soil and saprolite, and dissolution of carbonate rocks. Cold climatic conditions during the Wisconsinan, on the other hand, induced erosion of the landscape at rates faster than soil development. Upland erosion during the Wisconsinan removed pre-Wisconsinan soil and glacial sediment and bedrock to produce muddy to blocky colluvium, grézes litées, and alluvial fans on footslopes. Fluvial gravel and overlying colluvium in the Delaware Valley, both buried by late Wisconsinan outwash, are inferred to represent episodes of early and middle Wisconsinan (˜ 75-25 ka) upland erosion and river aggradiation followed by river degradation and colluvium deposition. Early-middle Wisconsinan colluvium is more voluminous than later colluvium despite colder, possibly permafrost conditions during the late Wisconsinan ˜ 25-10 ka). Extensive colluviation during the early and middle Wisconsinan resulted from a longer (50 kyr), generally cold interval of erosion with a greater availability of easily eroded pre-Wisconsinan surficial materials on uplands than during the late Wisconsinan. After recession of late Wisconsinan ice from its terminal position, soil formation and landscape

  4. A model of late quaternary landscape development in the Delaware Valley, New Jersey and Pennsylvania

    USGS Publications Warehouse

    Ridge, J.C.; Evenson, E.B.; Sevon, W.D.

    1992-01-01

    In the Delaware Valley of New Jersey and eastern Pennsylvania the late Quaternary history of colluviation, fluvial adjustment, and soil formation is based on the ages of pre-Wisconsinan soils and glacial deposits which are indicated by feld relationships and inferred from mid-latitude climate changes indicated by marine oxygen-isotope records. The area is divided into four terranes characterized by sandstone, gneiss, slate and carbonate rocks. Since the last pre-Wisconsinan glaciation (> 130 ka, inferred to be late Illinoian), each terrane responded differently to chemical and mechanical weathering. During the Sangamon interglacial stage (??? 130-75 ka) in situ weathering is inferred to have occurred at rates greater than transportation of material which resulted in the formation of deep, highly weathered soil and saprolite, and dissolution of carbonate rocks. Cold climatic conditions during the Wisconsinan, on the other hand, induced erosion of the landscape at rates faster than soil development. Upland erosion during the Wisconsinan removed pre-Wisconsinan soil and glacial sediment and bedrock to produce muddy to blocky colluvium, gre??zes lite??es, and alluvial fans on footslopes. Fluvial gravel and overlying colluvium in the Delaware Valley, both buried by late Wisconsinan outwash, are inferred to represent episodes of early and middle Wisconsinan (??? 75-25 ka) upland erosion and river aggradiation followed by river degradation and colluvium deposition. Early-middle Wisconsinan colluvium is more voluminous than later colluvium despite colder, possibly permafrost conditions during the late Wisconsinan ??? 25-10 ka). Extensive colluviation during the early and middle Wisconsinan resulted from a longer (50 kyr), generally cold interval of erosion with a greater availability of easily eroded pre-Wisconsinan surficial materials on uplands than during the late Wisconsinan. After recession of late Wisconsinan ice from its terminal position, soil formation and

  5. Cretaceous-Eocene (Laramide) landscape development and Oligocene- Pliocene drainage reorganization of transition zone and Colorado Plateau, Arizona

    USGS Publications Warehouse

    Elston, D.P.; Young, R.A.

    1991-01-01

    Landscape development of central and northern Arizona can no longer be ascribed mainly to events of Miocene and Pliocene age. New information on the age and distribution of older Cenozoic deposits has led to the recognition of a regional Cretaceous-Paleocene(?) surface of erosion that conforms to major elements on this regional surface of erosion. These relations cast new light on the history of evolution of the landscape and indicate a much greater age for the main landscape elements and a more complicated and prolonged history of erosion and deposition than has been previously supposed. The timing of events postulated for development of drainage on the Colorado Plateau can now be compared and partly reconciled with events recognized in the adjacent closely related Mountain Region (Transition Zone) of central Arizona. An understanding of this Tertiary structural, erosional, and depositional history can be important for the geological analysis of geophysical transects across the region. -from Authors

  6. Fire-free land use in pre-1492 Amazonian savannas.

    PubMed

    Iriarte, José; Power, Mitchell J; Rostain, Stéphen; Mayle, Francis E; Jones, Huw; Watling, Jennifer; Whitney, Bronwen S; McKey, Doyle B

    2012-04-24

    The nature and scale of pre-Columbian land use and the consequences of the 1492 "Columbian Encounter" (CE) on Amazonia are among the more debated topics in New World archaeology and paleoecology. However, pre-Columbian human impact in Amazonian savannas remains poorly understood. Most paleoecological studies have been conducted in neotropical forest contexts. Of studies done in Amazonian savannas, none has the temporal resolution needed to detect changes induced by either climate or humans before and after A.D. 1492, and only a few closely integrate paleoecological and archaeological data. We report a high-resolution 2,150-y paleoecological record from a French Guianan coastal savanna that forces reconsideration of how pre-Columbian savanna peoples practiced raised-field agriculture and how the CE impacted these societies and environments. Our combined pollen, phytolith, and charcoal analyses reveal unexpectedly low levels of biomass burning associated with pre-A.D. 1492 savanna raised-field agriculture and a sharp increase in fires following the arrival of Europeans. We show that pre-Columbian raised-field farmers limited burning to improve agricultural production, contrasting with extensive use of fire in pre-Columbian tropical forest and Central American savanna environments, as well as in present-day savannas. The charcoal record indicates that extensive fires in the seasonally flooded savannas of French Guiana are a post-Columbian phenomenon, postdating the collapse of indigenous populations. The discovery that pre-Columbian farmers practiced fire-free savanna management calls into question the widely held assumption that pre-Columbian Amazonian farmers pervasively used fire to manage and alter ecosystems and offers fresh perspectives on an emerging alternative approach to savanna land use and conservation that can help reduce carbon emissions.

  7. Fire-free land use in pre-1492 Amazonian savannas

    PubMed Central

    Iriarte, José; Power, Mitchell J.; Rostain, Stéphen; Mayle, Francis E.; Jones, Huw; Watling, Jennifer; Whitney, Bronwen S.; McKey, Doyle B.

    2012-01-01

    The nature and scale of pre-Columbian land use and the consequences of the 1492 “Columbian Encounter” (CE) on Amazonia are among the more debated topics in New World archaeology and paleoecology. However, pre-Columbian human impact in Amazonian savannas remains poorly understood. Most paleoecological studies have been conducted in neotropical forest contexts. Of studies done in Amazonian savannas, none has the temporal resolution needed to detect changes induced by either climate or humans before and after A.D. 1492, and only a few closely integrate paleoecological and archaeological data. We report a high-resolution 2,150-y paleoecological record from a French Guianan coastal savanna that forces reconsideration of how pre-Columbian savanna peoples practiced raised-field agriculture and how the CE impacted these societies and environments. Our combined pollen, phytolith, and charcoal analyses reveal unexpectedly low levels of biomass burning associated with pre-A.D. 1492 savanna raised-field agriculture and a sharp increase in fires following the arrival of Europeans. We show that pre-Columbian raised-field farmers limited burning to improve agricultural production, contrasting with extensive use of fire in pre-Columbian tropical forest and Central American savanna environments, as well as in present-day savannas. The charcoal record indicates that extensive fires in the seasonally flooded savannas of French Guiana are a post-Columbian phenomenon, postdating the collapse of indigenous populations. The discovery that pre-Columbian farmers practiced fire-free savanna management calls into question the widely held assumption that pre-Columbian Amazonian farmers pervasively used fire to manage and alter ecosystems and offers fresh perspectives on an emerging alternative approach to savanna land use and conservation that can help reduce carbon emissions. PMID:22493248

  8. Managing the matrix: decadal responses of eucalypt-dominated savanna to ambient fire regimes.

    PubMed

    Russell-Smith, Jeremy; Price, Owen F; Murphy, Brett P

    2010-09-01

    Much of our understanding of the response of savanna systems to fire disturbance relies on observations derived from manipulative fire plot studies. Equivocal findings from both recent Australian and African savanna fire plot assessments have significant implications for informing conservation management and reliable estimation of biomass stocks and dynamics. Influential northern Australian replicated fire plot studies include the 24-year plot-scale Munmarlary and the five-year catchment-scale Kapalga, mesic savanna (> 1000 mm/yr of rainfall) experiments in present-day Kakadu National Park. At Munmarlary, under low-to-moderate-intensity fire treatments, woody vegetation dominated by mature eucalypts was found to be structurally stable. At Kapalga, substantial declines in woody biomass were observed under more intense fire treatments, and modeling assessments implicate early-season fires as having adverse effects on longer-term tree recruitment. Given these contrasting perspectives, here we take advantage of a landscape-scale fire response monitoring program established on three major northern Australian conservation reserves (Kakadu, Litchfield, and Nitmiluk National Parks). Using statistical modeling we assess the decadal effects of ambient fire regime parameters (fire frequency, severity, seasonality, time since fire) on 32 vegetation structure components and abundance of 21 tree and 16 grass species from 122 monitoring plots. Over the study period the mean annual frequency of burning of plots was 0.53, comprising mostly early-dry-season, low-severity fires. Structural and species responses were variable but often substantial, notably resulting in stem recruitment and declines in juveniles, but only weakly explained by fire regime and habitat variables. Modeling of these observations under three realistic scenarios (increased fire severity under projected worsening climate change; modest and significant reductions in fire frequency to meet conservation criteria

  9. Managing the matrix: decadal responses of eucalypt-dominated savanna to ambient fire regimes.

    PubMed

    Russell-Smith, Jeremy; Price, Owen F; Murphy, Brett P

    2010-09-01

    Much of our understanding of the response of savanna systems to fire disturbance relies on observations derived from manipulative fire plot studies. Equivocal findings from both recent Australian and African savanna fire plot assessments have significant implications for informing conservation management and reliable estimation of biomass stocks and dynamics. Influential northern Australian replicated fire plot studies include the 24-year plot-scale Munmarlary and the five-year catchment-scale Kapalga, mesic savanna (> 1000 mm/yr of rainfall) experiments in present-day Kakadu National Park. At Munmarlary, under low-to-moderate-intensity fire treatments, woody vegetation dominated by mature eucalypts was found to be structurally stable. At Kapalga, substantial declines in woody biomass were observed under more intense fire treatments, and modeling assessments implicate early-season fires as having adverse effects on longer-term tree recruitment. Given these contrasting perspectives, here we take advantage of a landscape-scale fire response monitoring program established on three major northern Australian conservation reserves (Kakadu, Litchfield, and Nitmiluk National Parks). Using statistical modeling we assess the decadal effects of ambient fire regime parameters (fire frequency, severity, seasonality, time since fire) on 32 vegetation structure components and abundance of 21 tree and 16 grass species from 122 monitoring plots. Over the study period the mean annual frequency of burning of plots was 0.53, comprising mostly early-dry-season, low-severity fires. Structural and species responses were variable but often substantial, notably resulting in stem recruitment and declines in juveniles, but only weakly explained by fire regime and habitat variables. Modeling of these observations under three realistic scenarios (increased fire severity under projected worsening climate change; modest and significant reductions in fire frequency to meet conservation criteria

  10. Trade-offs between biodiversity conservation and economic development in five tropical forest landscapes.

    PubMed

    Sandker, Marieke; Ruiz-Perez, Manuel; Campbell, Bruce M

    2012-10-01

    This study explores how conservation and development are interlinked and quantifies their reciprocal trade-offs. It identifies interventions which hold a promise to improve both conservation and development outcomes. The study finds that development trajectories can either be at the cost of conservation or can benefit conservation, but in all cases sustained poverty negatively affects conservation in the long term. Most scenarios with better outcomes for conservation come at a cost for development and the financial benefits of payments for environmental services (PES) are not sufficient to compensate for lost opportunities to earn cash. However, implementation of strategies for reducing emissions from deforestation and forest degradation in locations with low population densities come close to overcoming opportunity costs. Environmental services and subsistence income enhance the attractiveness of conservation scenarios to local people and in situations where these benefits are obvious, PES may provide the extra cash incentive to tip the balance in favor of such a scenario. The paper stresses the importance of external factors (such as industrial investments and the development of the national economy) in determining landscape scale outcomes, and suggests a negotiating and visioning role for conservation agencies.

  11. Mitigating the effects of landscape development on streams in urbanizing watersheds

    USGS Publications Warehouse

    Hogan, Dianna M.; Jarnagin, S. Taylor; Loperfido, John V.; Van Ness, Keith

    2013-01-01

    This collaborative study examined urbanization and impacts on area streams while using the best available sediment and erosion control (S&EC) practices in developing watersheds in Maryland, United States. During conversion of the agricultural and forested watersheds to urban land use, land surface topography was graded and vegetation was removed creating a high potential for sediment generation and release during storm events. The currently best available S&EC facilities were used during the development process to mitigate storm runoff water quality, quantity, and timing before entering area streams. Detailed Geographic Information System (GIS) maps were created to visualize changing land use and S&EC practices, five temporal collections of LiDAR (light detection and ranging) imagery were used to map the changing landscape topography, and streamflow, physical geomorphology, and habitat data were used to assess the ability of the S&EC facilities to protect receiving streams during development. Despite the use of the best available S&EC facilities, receiving streams experienced altered flow, geomorphology, and decreased biotic community health. These impacts on small streams during watershed development affect sediment and nutrient loads to larger downstream aquatic ecosystems such as the Chesapeake Bay.

  12. Luminous Landscapes.

    ERIC Educational Resources Information Center

    Okrent, Inez

    2000-01-01

    Describes an activity for third-grade students in which they learn about early American landscape painters, specifically Frederick Church, Thomas Moran, and Albert Bierstadt. Students create natural landscapes, using the basic elements of landscape compositions. Discusses the process. (CMK)

  13. Long-term development of the Czech landscape studied on the basis of old topographic maps

    NASA Astrophysics Data System (ADS)

    Skokanová, H.; Havlíček, M.

    2009-04-01

    The paper deals with long-term land use changes in the Czech Republic with the help of old topographic maps. Departments of Landscape Ecology and GIS Applications from the Silva Tarouca Research Institute for Landscape and Ornamental Gardening, v.v.i. study these changes mainly in the research project MSM 6293359101 Research into sources and indicators of biodiversity in cultural landscape in the context of its fragmentation dynamics, the subpart Quantitative analysis of the dynamics of the Czech landscape development. In this paper, the authors concentrate mainly on map sources, which were acquired for the purpose of the project and also introduce partial results. Maps, which are the sources for the analyses, are following: maps from 2nd Austrian military survey in the scale 1:28 800 (created for the territory of the Czech Republic in the period 1836-1852), maps from 3rd Austrian military survey in the scale 1:25 000 (created for the Czech Republic in the period 1876-1880), Czechoslovak military topographic maps in the scale 1:25 000 from 1950s and 1990s, and Czech topographic base maps in the scale 1:10 000 from 2002-2006. It is necessary to complete maps of the 2nd and 3rd Austrian military survey thanks to their incompleteness, mainly along state borders. Also maps from 1nd Austrian military survey in the scale 1:28 800 (created for the Czech Republic in the period 1764-1783) are available; however, their usage for the accurate analyses in the GIS environment is restricted by their poor cartographic accuracy. Apart of the above mentioned maps, there has been progress in collecting maps from the interwar and war period (revised maps of the 3rd Austrian military survey maps, maps of the provisional military survey from 1923-1933, maps of definitive military survey from 1934-1938 and maps from survey of Moravian part of the Protectorate of Bohemia and Moravia, so called Messtischblätter from 1939-1945). Maps from five periods are manually vectorised in the GIS

  14. Using Digital Technologies in Mathematics Teaching: Developing an Understanding of the Landscape Using Three "Grand Challenge" Themes

    ERIC Educational Resources Information Center

    Joubert, Marie

    2013-01-01

    This paper develops an understanding of the issues, interests and concerns within the mathematics education community related to the use of computers and other digital technologies in the teaching and learning of mathematics. It begins by arguing for the importance of understanding this landscape of interests and concerns, and then turns to the…

  15. Evaluating governance for sustainable development - Insights from experiences in the Dutch fen landscape.

    PubMed

    den Uyl, Roos M; Driessen, Peter P J

    2015-11-01

    Prominent strands of discussion in the literature on governance for sustainable development debate how change can be induced to enhance sustainability, and how to evaluate the interventions aimed at prompting such change. Strikingly, there are few contributions about how prominent ideas of inducing change deal with multiple governance criteria for pursuing sustainable development. Moreover, the way ideas about inducing change relate to criteria of governance for sustainable development is not yet studied in an empirical context. This paper therefore comparatively analyses how three prominent modes of sustainable development governance - adaptive management, transition management and payments for environmental services - relate to a set of five prominent criteria reported in the literature, namely: equity, democracy, legitimacy, the handling of scale issues and the handling of uncertainty issues. It finds that the academic debates on these three modes address these criteria with varying attention and rather fragmented, while in the empirical setting of the Dutch fen landscape several aspects relating to the studied criteria were present and substantially influenced the functioning of the three modes of sustainable development. Together, the analysis of the literature debate and the empirical data are able to show that a narrow evaluation perspective may fail to diagnose and capture relevant struggles and complexities coming along with governance for sustainable development relevant issues. The study shows that in order to advance our understanding of governance for sustainable development, it is indeed important to include multiple criteria in studying these modes. Moreover, the study shows the importance of including empirical experiences which manifest when different modes for sustainable development are applied in real-world settings. PMID:26320012

  16. Evaluating governance for sustainable development - Insights from experiences in the Dutch fen landscape.

    PubMed

    den Uyl, Roos M; Driessen, Peter P J

    2015-11-01

    Prominent strands of discussion in the literature on governance for sustainable development debate how change can be induced to enhance sustainability, and how to evaluate the interventions aimed at prompting such change. Strikingly, there are few contributions about how prominent ideas of inducing change deal with multiple governance criteria for pursuing sustainable development. Moreover, the way ideas about inducing change relate to criteria of governance for sustainable development is not yet studied in an empirical context. This paper therefore comparatively analyses how three prominent modes of sustainable development governance - adaptive management, transition management and payments for environmental services - relate to a set of five prominent criteria reported in the literature, namely: equity, democracy, legitimacy, the handling of scale issues and the handling of uncertainty issues. It finds that the academic debates on these three modes address these criteria with varying attention and rather fragmented, while in the empirical setting of the Dutch fen landscape several aspects relating to the studied criteria were present and substantially influenced the functioning of the three modes of sustainable development. Together, the analysis of the literature debate and the empirical data are able to show that a narrow evaluation perspective may fail to diagnose and capture relevant struggles and complexities coming along with governance for sustainable development relevant issues. The study shows that in order to advance our understanding of governance for sustainable development, it is indeed important to include multiple criteria in studying these modes. Moreover, the study shows the importance of including empirical experiences which manifest when different modes for sustainable development are applied in real-world settings.

  17. Threshold responses of forest birds to landscape changes around exurban development.

    PubMed

    Suarez-Rubio, Marcela; Wilson, Scott; Leimgruber, Peter; Lookingbill, Todd

    2013-01-01

    Low-density residential development (i.e., exurban development) is often embedded within a matrix of protected areas and natural amenities, raising concern about its ecological consequences. Forest-dependent species are particularly susceptible to human settlement even at low housing densities typical of exurban areas. However, few studies have examined the response of forest birds to this increasingly common form of land conversion. The aim of this study was to assess whether, how, and at what scale forest birds respond to changes in habitat due to exurban growth. We evaluated changes in habitat composition (amount) and configuration (arrangement) for forest and forest-edge species around North America Breeding Bird Survey (BBS) stops between 1986 and 2009. We used Threshold Indicator Taxa Analysis to detect change points in species occurrence at two spatial extents (400-m and 1-km radius buffer). Our results show that exurban development reduced forest cover and increased habitat fragmentation around BBS stops. Forest birds responded nonlinearly to most measures of habitat loss and fragmentation at both the local and landscape extents. However, the strength and even direction of the response changed with the extent for several of the metrics. The majority of forest birds' responses could be predicted by their habitat preferences indicating that management practices in exurban areas might target the maintenance of forested habitats, for example through easements or more focused management for birds within existing or new protected areas.

  18. Threshold Responses of Forest Birds to Landscape Changes around Exurban Development

    PubMed Central

    Suarez-Rubio, Marcela; Wilson, Scott; Leimgruber, Peter; Lookingbill, Todd

    2013-01-01

    Low-density residential development (i.e., exurban development) is often embedded within a matrix of protected areas and natural amenities, raising concern about its ecological consequences. Forest-dependent species are particularly susceptible to human settlement even at low housing densities typical of exurban areas. However, few studies have examined the response of forest birds to this increasingly common form of land conversion. The aim of this study was to assess whether, how, and at what scale forest birds respond to changes in habitat due to exurban growth. We evaluated changes in habitat composition (amount) and configuration (arrangement) for forest and forest-edge species around North America Breeding Bird Survey (BBS) stops between 1986 and 2009. We used Threshold Indicator Taxa Analysis to detect change points in species occurrence at two spatial extents (400-m and 1-km radius buffer). Our results show that exurban development reduced forest cover and increased habitat fragmentation around BBS stops. Forest birds responded nonlinearly to most measures of habitat loss and fragmentation at both the local and landscape extents. However, the strength and even direction of the response changed with the extent for several of the metrics. The majority of forest birds’ responses could be predicted by their habitat preferences indicating that management practices in exurban areas might target the maintenance of forested habitats, for example through easements or more focused management for birds within existing or new protected areas. PMID:23826325

  19. Savanna vegetation-fire-climate relationships differ among continents.

    PubMed

    Lehmann, Caroline E R; Anderson, T Michael; Sankaran, Mahesh; Higgins, Steven I; Archibald, Sally; Hoffmann, William A; Hanan, Niall P; Williams, Richard J; Fensham, Roderick J; Felfili, Jeanine; Hutley, Lindsay B; Ratnam, Jayashree; San Jose, Jose; Montes, Ruben; Franklin, Don; Russell-Smith, Jeremy; Ryan, Casey M; Durigan, Giselda; Hiernaux, Pierre; Haidar, Ricardo; Bowman, David M J S; Bond, William J

    2014-01-31

    Ecologists have long sought to understand the factors controlling the structure of savanna vegetation. Using data from 2154 sites in savannas across Africa, Australia, and South America, we found that increasing moisture availability drives increases in fire and tree basal area, whereas fire reduces tree basal area. However, among continents, the magnitude of these effects varied substantially, so that a single model cannot adequately represent savanna woody biomass across these regions. Historical and environmental differences drive the regional variation in the functional relationships between woody vegetation, fire, and climate. These same differences will determine the regional responses of vegetation to future climates, with implications for global carbon stocks.

  20. Change in the forested and developed landscape of the Lake Tahoe basin, California and Nevada, USA, 1940-2002

    USGS Publications Warehouse

    Raumann, C.G.; Cablk, M.E.

    2008-01-01

    The current ecological state of the Lake Tahoe basin has been shaped by significant landscape-altering human activity and management practices since the mid-1850s; first through widespread timber harvesting from the 1850s to 1920s followed by urban development from the 1950s to the present. Consequences of landscape change, both from development and forest management practices including fire suppression, have prompted rising levels of concern for the ecological integrity of the region. The impacts from these activities include decreased water quality, degraded biotic communities, and increased fire hazard. To establish an understanding of the Lake Tahoe basin's landscape change in the context of forest management and development we mapped, quantified, and described the spatial and temporal distribution and variability of historical changes in land use and land cover in the southern Lake Tahoe basin (279 km2) from 1940 to 2002. Our assessment relied on post-classification change detection of multi-temporal land-use/cover and impervious-surface-area data that were derived through manual interpretation, image processing, and GIS data integration for four dates of imagery: 1940, 1969, 1987, and 2002. The most significant land conversion during the 62-year study period was an increase in developed lands with a corresponding decrease in forests, wetlands, and shrublands. Forest stand densities increased throughout the 62-year study period, and modern thinning efforts resulted in localized stand density decreases in the latter part of the study period. Additionally forests were gained from succession, and towards the end of the study period extensive tree mortality occurred. The highest rates of change occurred between 1940 and 1969, corresponding with dramatic development, then rates declined through 2002 for all observed landscape changes except forest density decrease and tree mortality. Causes of landscape change included regional population growth, tourism demands

  1. GSK3beta: role in therapeutic landscape and development of modulators.

    PubMed

    Phukan, S; Babu, V S; Kannoji, A; Hariharan, R; Balaji, V N

    2010-05-01

    Glycogen synthase kinase-3 beta (GSK3beta) is a multifunctional serine/threonine kinase which was originally identified as a regulator of glycogen metabolism. It plays a key role in the regulation of numerous signalling pathways including cellular process such as cell cycle, inflammation and cell proliferation. Over the last few years there is a considerable rise in the number of journals and patents publication by different workers worldwide. Many pharmaceutical companies are focusing on GSK3beta as a therapeutic target for the treatment of disease conditions. The present review is focused on signalling pathways of different disease conditions where GSK3beta is implicated. In this review, we present a comprehensive map of GSK3beta signalling pathways in disease physiologies. Structural analysis of GSK3beta along with molecular modelling reports from numerous workers are reviewed in context of design and development of GSK3beta inhibitors. Patent landscape of the small molecule modulators is profiled. The chemo space for small molecule modulators extracted from public and proprietary Kinase Chembiobase for GSK3beta are discussed. Compounds in different clinical phases of discovery are analysed. The review ends with the overall status of this important therapeutic target and challenges in development of its modulators.

  2. The evolving drug development landscape: from blockbusters to niche busters in the orphan drug space.

    PubMed

    Kumar Kakkar, Ashish; Dahiya, Neha

    2014-06-01

    Strategy, Management and Health Policy Large pharmaceutical companies have traditionally focused on the development of blockbuster drugs that target disease states with large patient populations. However, with large-scale patent expirations and competition from generics and biosimilars, anemic pipelines, escalating clinical trial costs, and global health-care reform, the blockbuster model has become less viable. Orphan drug initiatives and the incentives accompanied by these have fostered renewed research efforts in the area of rare diseases and have led to the approval of more than 400 orphan products. Despite targeting much smaller patient populations, the revenue-generating potential of orphan drugs has been shown to be huge, with a greater return on investment than non-orphan drugs. The success of these "niche buster" therapeutics has led to a renewed interest from "Big Pharma" in the rare disease landscape. This article reviews the key drivers for orphan drug research and development, their profitability, and issues surrounding the emergence of large pharmaceutical firms into the orphan drug space.

  3. GSK3β: role in therapeutic landscape and development of modulators

    PubMed Central

    Phukan, S; Babu, VS; Kannoji, A; Hariharan, R; Balaji, VN

    2010-01-01

    Glycogen synthase kinase-3 beta (GSK3β) is a multifunctional serine/threonine kinase which was originally identified as a regulator of glycogen metabolism. It plays a key role in the regulation of numerous signalling pathways including cellular process such as cell cycle, inflammation and cell proliferation. Over the last few years there is a considerable rise in the number of journals and patents publication by different workers worldwide. Many pharmaceutical companies are focusing on GSK3β as a therapeutic target for the treatment of disease conditions. The present review is focused on signalling pathways of different disease conditions where GSK3β is implicated. In this review, we present a comprehensive map of GSK3β signalling pathways in disease physiologies. Structural analysis of GSK3β along with molecular modelling reports from numerous workers are reviewed in context of design and development of GSK3β inhibitors. Patent landscape of the small molecule modulators is profiled. The chemo space for small molecule modulators extracted from public and proprietary Kinase Chembiobase for GSK3β are discussed. Compounds in different clinical phases of discovery are analysed. The review ends with the overall status of this important therapeutic target and challenges in development of its modulators. PMID:20331603

  4. Desert pavement development and landscape stability on the Eastern Libyan Plateau, Egypt

    NASA Astrophysics Data System (ADS)

    Adelsberger, Katherine A.; Smith, Jennifer R.

    2009-06-01

    Desert pavement surfaces of the eastern Libyan Plateau in central Egypt represent a stable landscape preserving Middle and Upper Paleolithic artifacts. Detailed measurements of pavement clasts indicate significant variability in clast size, density, lithology and orientation between pavements, but no spatial relationship among any of these pavement variables over the study area. Pavement characteristics are unrelated to local geomorphic features including slope gradient and aspect, suggesting a desert pavement surface that has developed without significant influence from transporting mechanisms such as overland flow and slope failure. Meridional vertical cracks in surface clasts implicate thermal stresses due to diurnal solar variation as a mechanical weathering process, whereas the presence of a clast-free silty layer within all soil profiles indicates that these are accretionary pavement surfaces that have grown upward over time. The desert pavement in this region has likely developed in situ through mechanical breakdown of surface clasts and desert pedogenesis, indicating long-term stability for this region and minimal taphonomic effects on artifacts > 2 cm in diameter deposited on this surface over the last ca. 100 ka.

  5. Development of a landscape unit delineation framework for ecoy-hydrologic models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A spatially distributed representation of basin hydrology and transport processes in eco-hydrological models facilitates the identification of critical source areas and the placement of management and conservation measures. Especially floodplains are critical landscape features that differ from nei...

  6. Assessing the Impact of Landscape Development on Ecosystem Services Value in Tropical Watershed

    NASA Astrophysics Data System (ADS)

    Foo, Y. S.; Hashim, M.

    2014-02-01

    As development increases with demand, more forest lands are replaced with cropland, commercial plantation, and infrastructures for being able to accommodate the excessive growth in world's population. Environments were destroyed without considering their values in sustaining life on Earth.This phenomenon is still an ongoing scenario in most of the developing countries in the tropical region including Malaysia. Such unrestricted conversion may cause food or water crisis along with irreparable consequences to local and regional climate as the natural ecosystem is not only the main resources generator but also the climate stabilizer. Contrary to this, a study was conducted in Pahang Watershed, the largest watershed in Peninsular Malaysia with forest as the dominant land cover, to investigate the effect of landscape development on the ecosystem in terms of the erosion and ecosystem service value. Results of soil loss based on USLE indicated a direct relationship between development and total soil loss where total annual soil loss in year 2005 and 2010 showed a significant increase compare to year 2000. Meanwhile, developed and agricultural lands were discovered to be the main contributor whereas forest land produce the least soil loss (<10ton/ ha/yr). Apart from this, this study also reports a degrading trend in the overall ecological service value and goods (ESVG). Although oil palm had become the main commercial plantation in current years, the commercial profit brought by oil palm still insufficient to cover losses referring to overall estimated ESVG due to the forest clearance and soil degradation. In addition, for a destroyed ecosystem to be equilibrium again requires years. Therefore, ESVG of the tropical forest are expected to increase continuously in future which mean that the roles of the forest in conserving the environment stabilization and sustainability of life are getting more critical.

  7. Forest ecosystem development in post-mining landscapes: a case study of the Lusatian lignite district.

    PubMed

    Hüttl, R F; Weber, E

    2001-08-01

    The restoration of surface mining landscapes requries the (re)creation of ecosystems. In Lusatia (eastern Germany), large-scale open-cast lignite mining operations generated spoil dumps widely consisting of acidified, phytotoxic substrates. Amelioration and rehabilitation measures have been developed and applied to these substrates since the 1950s. However, it is still not clear whether these approaches are sustainable. This paper reports on collaborative research work into the ecological potential of forest ecosystem development on typical minesites in the Lusatian lignite district. At first sight, pine stands on minesites along a chronosequence comprising about 35 years did not show differences when compared with stands on non-mined sites of the general region. Furthermore, with some modification, conceptual models for flora and fauna succession in forest stands on non-mined sites seem to be applicable, at least for the early stages of forest ecosystem development. For example, soil organism abundance and activity at minesites had already reached levels typical of non-mined sites after about 20-30 years. In contrast, mine soils are very different from non-mined soils of the test region. Chemically, mine soil development is dominated by processes originating from pyrite oxidation. Geogenic, i.e. lignitic, soil organic carbon was shown to substitute for some functions of pedogenic soil organic matter. Rooting was hampered but not completely impeded in strongly acidified soil compartments. Roots and mycorrhizae are apparently able to make use of the characteristic heterogeneity of young mine soils. Considering these recent results and the knowledge accumulated during more than 30 years of research on minesite rehabilitation internationally, it can be stated that minesite restoration might be used as an ideal case study for forest ecosystem development starting at "point zero" on "terra nova".

  8. Emissions from savanna fires in southern Africa

    NASA Astrophysics Data System (ADS)

    Sinha, Parikhit

    2004-12-01

    Airborne measurements are presented of emissions from savanna fires in southern Africa during the dry season. Measurements were obtained aboard the University of Washington Convair-580 research aircraft during the SAFARI 2000 field project in August and September 2000. Savanna fires in southern Africa emit a wide range of gaseous and particulate species including carbon, sulfur, nitrogen, halogen, and oxygenated compounds. Emission factors, emission ratios, and regional emissions of fifty trace gas and particulate species were derived, including eight species not previously reported in the literature (dimethyl sulfide, methyl nitrate, five species of hydrocarbons, and particles with diameters from 0.1--3 mum diameter). The physical, chemical, and radiative properties of the plume from a large savanna fire in South Africa are characterized, including plume dimensions, secondary formation of ozone and organic acids, oxidation of hydrocarbons, coagulation of particles, and gas-to-particle conversion in aged smoke. Numerous fires, thermodynamically stable layers aloft, and large-scale anticylonic flow result in high concentrations of air pollution distributed throughout the lower troposphere over southern Africa during the dry season. Average regional concentrations of CO (261 +/- 81 ppbv), SO2 (2.5 +/- 1.6 ppbv), O3 (64 +/- 13 ppbv), black particulate carbon (2.3 +/- 1.9 mug m-3), organic particulate carbon (6.2 +/- 5.2 mug m-3), total particle mass (26.0 +/- 4.7 mug m-3) are comparable to those found in polluted urban environments. The GEOS-CHEM model of tropospheric chemistry is used to characterize the transport of biomass burning emissions from southern Africa to the neighboring Atlantic and Indian Oceans during the dry season (May--October) of 2000. A large quantity of biomass burning emissions from southern Africa is transported westward over the latitudes 0--20°S to the southern Atlantic Ocean (˜40 Tg CO from May--October), contributing to a pollution anomaly

  9. From the Field to the Classroom: A Web-Based Teaching Tool on Depositional Environments and Landscape Development

    NASA Astrophysics Data System (ADS)

    Krzic, M.; Watson, K.; Grand, S.; Crowley, C.; Dyanatkar, S.; Bomke, A.; Smith, S.

    2012-04-01

    The relationship between sedimentary deposits, landforms and soil profile development is difficult for students to grasp in a conventional classroom setting. The ideal way to solve this is to take the students on extended field trips; however, field trips are expensive, have to be conducted during specific time periods, and can only handle a limited number of students. The objective of this project was to bring the field to the classroom via a virtual, dynamic web-based teaching tool illustrating common depositional environments and associated landforms and soils. The teaching tool was largely based on video footage obtained in the Canadian Rocky Mountains and in the grasslands of the southern interior of British Columbia. The Canadian Rockies are undergoing rapid deglaciation and provided excellent examples of new glacial deposits and early landscape development processes. On the other hand, British Columbia's grasslands became ice-free about 10,000 years ago and were used to illustrate landscape evolution and post-glaciation soil profile development. To bring these two environments together, video footage of corresponding landforms was shot at both locations and edited into a series of short video clips illustrating the link between depositional processes, resulting landforms and soils and their post-glacial evolution. Soil scientists, survey specialists and geomorphologists provided live commentary. The teaching tool (http://soilweb.landfood.ubc.ca/landscape/) is an open-access website merging video clips, sound recordings, text, photos and graphics intended to help students situate landforms within their geomorphologic context. This online teaching resource allows students to observe, on their own time, conditions under which sediments are deposited and soils are formed, and to witness the transformation of a barren, glacial landscape into a vegetated soil landscape. The tool can be used in various geomorphology, soil, agriculture, forestry, and natural

  10. Evaluation of multi-level social learning for sustainable landscapes: perspective of a development initiative in Bergslagen, Sweden.

    PubMed

    Axelsson, Robert; Angelstam, Per; Myhrman, Lennart; Sädbom, Stefan; Ivarsson, Milis; Elbakidze, Marine; Andersson, Kenneth; Cupa, Petr; Diry, Christian; Doyon, Frederic; Drotz, Marcus K; Hjorth, Arne; Hermansson, Jan Olof; Kullberg, Thomas; Lickers, F Henry; McTaggart, Johanna; Olsson, Anders; Pautov, Yurij; Svensson, Lennart; Törnblom, Johan

    2013-03-01

    To implement policies about sustainable landscapes and rural development necessitates social learning about states and trends of sustainability indicators, norms that define sustainability, and adaptive multi-level governance. We evaluate the extent to which social learning at multiple governance levels for sustainable landscapes occur in 18 local development initiatives in the network of Sustainable Bergslagen in Sweden. We mapped activities over time, and interviewed key actors in the network about social learning. While activities resulted in exchange of experiences and some local solutions, a major challenge was to secure systematic social learning and make new knowledge explicit at multiple levels. None of the development initiatives used a systematic approach to secure social learning, and sustainability assessments were not made systematically. We discuss how social learning can be improved, and how a learning network of development initiatives could be realized. PMID:23475659

  11. Evaluation of multi-level social learning for sustainable landscapes: perspective of a development initiative in Bergslagen, Sweden.

    PubMed

    Axelsson, Robert; Angelstam, Per; Myhrman, Lennart; Sädbom, Stefan; Ivarsson, Milis; Elbakidze, Marine; Andersson, Kenneth; Cupa, Petr; Diry, Christian; Doyon, Frederic; Drotz, Marcus K; Hjorth, Arne; Hermansson, Jan Olof; Kullberg, Thomas; Lickers, F Henry; McTaggart, Johanna; Olsson, Anders; Pautov, Yurij; Svensson, Lennart; Törnblom, Johan

    2013-03-01

    To implement policies about sustainable landscapes and rural development necessitates social learning about states and trends of sustainability indicators, norms that define sustainability, and adaptive multi-level governance. We evaluate the extent to which social learning at multiple governance levels for sustainable landscapes occur in 18 local development initiatives in the network of Sustainable Bergslagen in Sweden. We mapped activities over time, and interviewed key actors in the network about social learning. While activities resulted in exchange of experiences and some local solutions, a major challenge was to secure systematic social learning and make new knowledge explicit at multiple levels. None of the development initiatives used a systematic approach to secure social learning, and sustainability assessments were not made systematically. We discuss how social learning can be improved, and how a learning network of development initiatives could be realized.

  12. Rates of surface lowering and landscape development in southern South Africa: a cosmogenic view

    NASA Astrophysics Data System (ADS)

    Richardson, Janet; Vanacker, Veerle; Lang, Andreas; Hodgson, David

    2016-04-01

    The landscape of southern South Africa is characterised by large-scale erosion surfaces, including extensive pediments and multiple strath terraces, which document discordant river evolution through resistant quarzitic lithologies of the Cape Fold Belt (CFB). The timing and rate of erosion is poorly constrained. New cosmogenic ages from surfaces in South Africa are presented using in situ produced 10Be. Strath terraces in deeply incised rivers at two sites within the CFB indicate slow rates of erosion (1.54 - 11.79 m/Ma), which are some of the lowest rates recorded globally. Four pediment surfaces and a depth profile of the thickest pediment were also dated, and the results indicate that there are low rates of surface lowering on the pediments (0.44 - 1.24 m/Ma). The pediments are long-lived features (minimum exposure ages of 0.47 - 1.09 Ma), and are now deeply dissected. Given the minimum exposure ages, calculated river incision rates (42- 203 m/Ma) suggest that after a long period of geomorphic stability during pediment formation there was a discrete phase of increased geomorphic activity. The calculated minimum exposure ages are considered dubious because: 1) known rates of surrounding river incision (published and ours); 2) the climate conditions and time necessary for ferricrete formation on the pediment surfaces and; 3) the deeply incised catchments in the CFB on which the pediments sit, which all point to the pediments being much older. The pediments are fossilised remnants of a much larger geomorphic surface that formed after the main phase of exhumation in southern Africa. They form a store of sediment that currently sit above the surrounding rivers that have some of the lowest erosion rates in the world. These results indicate that steep topography can prevail even in areas of low erosion and tectonic quiescence, and that whilst cosmogenic dating of landscapes is an exciting development in earth sciences, care is needed especially in ancient settings. We

  13. Linking landscape development intensity within watersheds to methyl-mercury accumulation in river sediments.

    PubMed

    Bonzongo, Jean-Claude J; Donkor, Augustine K; Attibayeba, Attibayeba; Gao, Jie

    2016-03-01

    An indicator of the disturbance of natural systems, the landscape development intensity (LDI) index, was used to assess the potential for land-use within watersheds to influence the production/accumulation of methyl-mercury (MeHg) in river sediments. Sediment samples were collected from locations impacted by well-identified land-use types within the Mobile-Alabama River Basin in Southeastern USA. The samples were analyzed for total-Hg (THg) and MeHg concentrations and the obtained values correlated to the calculated LDI indexes of the sampled watersheds to assess the impact of prevalent land use/land cover on MeHg accumulation in sediments. The results show that unlike THg, levels of MeHg found in sediments are impacted by the LDI indexes. Overall, certain combinations of land-use types within a given watershed appear to be more conducive to MeHg accumulation than others, therefore, pointing to the possibility of targeting land-use practices as potential means for reducing MeHg accumulation in sediments, and ultimately, fish contamination. PMID:26427848

  14. The challenges associated with developing science-based landscape scale management plans

    USGS Publications Warehouse

    Szaro, R.C.; Boyce, D.A.; Puchlerz, T.

    2005-01-01

    Planning activities over large landscapes poses a complex of challenges when trying to balance the implementation of a conservation strategy while still allowing for a variety of consumptive and nonconsumptive uses. We examine a case in southeast Alaska to illustrate the breadth of these challenges and an approach to developing a science-based resource plan. Not only was the planning area, the Tongass National Forest, USA, exceptionally large (approximately 17 million acres or 6.9 million ha), but it also is primarily an island archipelago environment. The water system surrounding and going through much of the forest provides access to facilitate the movement of people, animals, and plants but at the same time functions as a barrier to others. This largest temperate rainforest in the world is an exceptional example of the complexity of managing at such a scale but also illustrates the role of science in the planning process. As we enter the 21st century, the list of questions needing scientific investigation has not only changed dramatically, but the character of the questions also has changed. Questions are contentious, cover broad scales in space and time, and are highly complex and interdependent. The provision of unbiased and objective information to all stakeholders is an important step in informed decision-making.

  15. The interactions of fire regimes, land management, vegetation dynamics and the atmosphere in northern Australian savannas

    NASA Astrophysics Data System (ADS)

    Cook, Garry; Meyer, Mick

    2014-05-01

    The Australian tropical savannas burn with frequencies ranging from one in five to one in two years. Uniquely for an OECD country, these fires contribute substantially to accountable national greenhouse gas emissions. Concern about those emissions has led to the development of approaches to imprive fire management to reduce emissions and increase carbon sequestration. Savanna dyanmics are however, also determined by interactions with rainfall regimes. In this paper, we present an overview of fire regimes in northern Australia, their effects on the greenhouse gas emissions and how management of those fires interacts with climatic variability and likely climate change. Data will be presented from on-ground measurements of emissions, vegetation dyanamics as well as interpretation of satellite imagery of fire scars.

  16. Emissions from Miombo Woodland and Dambo Grassland Savanna Fires

    NASA Technical Reports Server (NTRS)

    Sinha, Parikhit; Hobbs, Peter V.; Yokelson, Robert J.; Blake, Donald R.; Gao, Song; Kirchstetter, Thomas W.

    2004-01-01

    Airborne measurements of trace gases and particles over and downwind of two prescribed savanna fires in Zambia are described. The measurements include profiles through the smoke plumes of condensation nucleus concentrations and normalized excess mixing ratios of particles and gases, emission factors for 42 trace gases and seven particulate species, and vertical profiles of ambient conditions. The fires were ignited in plots of miombo woodland savanna, the most prevalent savanna type in southern Africa, and dambo grassland savanna, an important enclave of miombo woodland ecosystems. Emission factors for the two fires are combined with measurements of fuel loading, combustion factors, and burned area (derived from satellite burn scar retrievals) to estimate the emissions of trace gases and particles from woodland and grassland savanna fires in Zambia and southern Africa during the dry season (May-October) of 2000. It is estimated that the emissions of CO2, CO, total hydrocarbons, nitrogen oxides (NOx as NO), sulfur dioxide (SO2), formaldehyde, methyl bromide, total particulate matter, and black carbon from woodland and grassland savanna fires during the dry season of 2000 in southern Africa contributed 12.3%, 12.6%, 5.9%, 10.3%, 7.5%, 24.2%, 2.8%, 17.5%, and 11.1%, respectively, of the average annual emissions from all types of savanna fires worldwide. In 2000 the average annual emissions of methane, ethane, ethene, acetylene, propene, formaldehyde, methanol, and acetic acid from the use of biofuels in Zambia were comparable to or exceeded dry season emissions of these species from woodland and grassland savanna fires in Zambia.

  17. Acceptability of residential development in a regional landscape: Potential effects on wildlife occupancy patterns

    USGS Publications Warehouse

    Bettigole, Charles A.; Donovan, Therese; Manning, Robert; Austin, John; Long, Robert

    2014-01-01

    The conversion of natural lands to developed uses may pose the single greatest human threat to global terrestrial biodiversity. Continued human growth and development over the next century will further exacerbate these effects of habitat loss and fragmentation. Natural resource managers are tasked with managing wildlife as a public trust, yet often have little say in land use decisions. Generally speaking, decision makers could benefit from an understanding of what different regulations mean in terms of wildlife distribution. In a previous paper (Bettigole et al., 2013), we surveyed town residents throughout Vermont to measure how respondents feel about a range of development levels within their town boundaries. We estimated the “social carrying capacity for development” – orSKd – for 251 towns in Vermont. SKd provides an estimate of the level of developed land cover classes that town residents deem “acceptable” within their town boundaries. In this paper, we design a framework for linking the town-specific SKd estimates with the wildlife distribution patterns for three wide-ranging mammalian species: American black bear (Ursus americanus), fisher (Martes pennanti), and bobcat (Lynx rufus). We simulated landscape conditions at SKd for each town in Vermont, and then used existing occupancy models for the three target species to spatially map and compare occupancy rates in the baseline year 2000 with occupancy rates at SKd. With nearly 90% of Vermont towns willing to increase developed landcover classes within town boundaries compared to baseline levels, significant state-wide changes in occupancy rates were predicted for all three focal species. Average occupancy rates declined by −15.9% and −3.1% for black bear and bobcats, respectively. Average occupancy rates for fisher increased by 9.0%. This study provides a method for linking development standards within a town with wildlife occurrence. Across towns, the methodology spatially identifies

  18. Spiny plants, mammal browsers, and the origin of African savannas.

    PubMed

    Charles-Dominique, Tristan; Davies, T Jonathan; Hempson, Gareth P; Bezeng, Bezeng S; Daru, Barnabas H; Kabongo, Ronny M; Maurin, Olivier; Muasya, A Muthama; van der Bank, Michelle; Bond, William J

    2016-09-20

    Savannas first began to spread across Africa during the Miocene. A major hypothesis for explaining this vegetation change is the increase in C4 grasses, promoting fire. We investigated whether mammals could also have contributed to savanna expansion by using spinescence as a marker of mammal herbivory. Looking at the present distribution of 1,852 tree species, we established that spinescence is mainly associated with two functional types of mammals: large browsers and medium-sized mixed feeders. Using a dated phylogeny for the same tree species, we found that spinescence evolved at least 55 times. The diversification of spiny plants occurred long after the evolution of Afrotherian proboscideans and hyracoids. However, it is remarkably congruent with diversification of bovids, the lineage including the antelope that predominantly browse these plants today. Our findings suggest that herbivore-adapted savannas evolved several million years before fire-maintained savannas and probably, in different environmental conditions. Spiny savannas with abundant mammal herbivores occur in drier climates and on nutrient-rich soils, whereas fire-maintained savannas occur in wetter climates on nutrient-poor soils.

  19. Spiny plants, mammal browsers, and the origin of African savannas.

    PubMed

    Charles-Dominique, Tristan; Davies, T Jonathan; Hempson, Gareth P; Bezeng, Bezeng S; Daru, Barnabas H; Kabongo, Ronny M; Maurin, Olivier; Muasya, A Muthama; van der Bank, Michelle; Bond, William J

    2016-09-20

    Savannas first began to spread across Africa during the Miocene. A major hypothesis for explaining this vegetation change is the increase in C4 grasses, promoting fire. We investigated whether mammals could also have contributed to savanna expansion by using spinescence as a marker of mammal herbivory. Looking at the present distribution of 1,852 tree species, we established that spinescence is mainly associated with two functional types of mammals: large browsers and medium-sized mixed feeders. Using a dated phylogeny for the same tree species, we found that spinescence evolved at least 55 times. The diversification of spiny plants occurred long after the evolution of Afrotherian proboscideans and hyracoids. However, it is remarkably congruent with diversification of bovids, the lineage including the antelope that predominantly browse these plants today. Our findings suggest that herbivore-adapted savannas evolved several million years before fire-maintained savannas and probably, in different environmental conditions. Spiny savannas with abundant mammal herbivores occur in drier climates and on nutrient-rich soils, whereas fire-maintained savannas occur in wetter climates on nutrient-poor soils. PMID:27601649

  20. Seasonal Controls on Water and Carbon Fluxes Responding to Pulse Precipitation Events in Dryland Systems: Examples from Southern African Savannas

    NASA Astrophysics Data System (ADS)

    Williams, C. A.; Hanan, N. P.; Scholes, R. J.

    2005-12-01

    Water and carbon fluxes from savanna landscapes are tightly coupled to soil water availability through physiological limitation from plant water stress. This general principle has been used to broadly characterize savanna vegetation distributions based almost solely on rainfall or soil moisture. However, a number of other physical and biotic drivers vary seasonally and interannually, including radiation, humidity, leaf area, and plant functional type. It remains unclear to what degree these other drivers limit our ability to accurately predict vegetation distributions in water-limited systems. In this study, we analyze five years of eddy flux data collected at Kruger National Park, South Africa, to investigate the degree to which these other drivers modulate soil moisture control of water and carbon fluxes. Our analysis focuses on what controls seasonal variation in the response of canopy-scale fluxes to pulse precipitation events and subsequent drydown. From more than thirty drydown response curves, we find pronounced seasonal variation in the time rate of decay of soil moisture and evapotranspiration, which are both well represented as either a logarithm or power of time since a rainfall pulse. Radiation and humidity explain most of the residuals in the response of evapotranspiration to soil moisture, with only weak explanatory power of leaf area. We also find little difference in the drydown responses of Combretum versus Acacia dominated savannas. Marked seasonal shifts in canopy-scale water use efficiency (carbon / water fluxes) documents transitions from early wet season greening, to dry season moisture stress, to dormancy and decay prior to first rains. These results suggest that generalized relations between soil moisture, evapotranspiration, and carbon exchange are robust when adjusted to incorporate seasonal dependence on radiation and humidty. Broader implications for modeling savanna vegetation distributions will be discussed.

  1. Origin and dynamics of the northern South American coastal savanna belt during the Holocene - the role of climate, sea-level, fire and humans

    NASA Astrophysics Data System (ADS)

    Alizadeh, Kamaleddin; Cohen, Marcelo; Behling, Hermann

    2015-08-01

    Presence of a coastal savanna belt expanding from British Guiana to northeastern Brazil cannot be explained by present-day climate. Using pollen and charcoal analyses on an 11.6 k old sediment core from a coastal depression in the savanna belt near the mouth of the Amazon River we investigated the paleoenvironmental history to shed light on this question. Results indicate that small areas of savanna accompanied by a forest type composed primarily by the genus Micropholis (Sapotaceae) that has no modern analog existed at the beginning of the Holocene. After 11,200 cal yr BP, savanna accompanied by few trees replaced the forest. In depressions swamp forest developed and by ca 10,000 cal yr BP replaced by Mauritia swamps. Between 8500 and 5600 cal yr BP gallery forest (composed mainly of Euphorbiaceae) and swamp forest succeeded the treeless savanna. The modern vegetation with alternating gallery forest and savanna developed after 5600 cal yr BP. We suggest that the early Holocene no-analog forest is a relict of previously more extensive forest under cooler and moister Lateglacial conditions. The early Holocene savanna expansion indicates a drier phase probably related to the shift of the Intertropical Convergence Zone (ITCZ) towards its northernmost position. The mid-Holocene forest expansion is probably a result of the combined influence of equatorwards shift of ITCZ joining the South Atlantic Convergence Zone (SACZ). The ecosystem variability during the last 5600 cal yr BP, formed perhaps under influence of intensified ENSO condition. High charcoal concentrations, especially during the early Holocene, indicate that natural and/or anthropogenic fires may have maintained the savanna. However, our results propose that climate change is the main driving factor for the formation of the coastal savanna in this region. Our results also show that the early Holocene sea level rise established mangroves near the study site until 7500 cal yr BP and promoted

  2. Post-glacial coast development and human settling of the North European Ice Marginal Landscape (IML)

    NASA Astrophysics Data System (ADS)

    Bregman, I. Kant Baltic Federal State University, Kaliningrad, Russia, E. P. H.; Netherlands, Utrecht University, the; Druzhinina, I. Kant Baltic Federal State University, Kaliningrad, Russia, O. A.

    2012-04-01

    In North Europe, in the Ice Marginal Landscapes (IML) from the Netherlands to Estonia, human settling is in the Late-Pleistocene - Holocene strongly influenced by post-glacial relative coast development(MESO, 2010; SINCOS, 2002-2009; Machu, 2006-2009, IGCP project 346, CoPaF, 2009-2012) and glacio-isostasy. Geological processes like updoming and tectonic block displacements not only influenced sedimentation of river systems in delta's (e.g. Cohen, 2003), but influenced coastal development and human settling too in the North Sea area (e.g. Peeters, 2009; Hijma e.a., 2011) the Wadden areas (e.g. de Langen, 2011) and lagoons (e.g. Druzhinina, 2010). An overview of shoreline development at the distal side of the Late Glacial forbulge related to glaciological and geophysical processes however does not exist and coastal development models are also not correlated with human settling. Our project( 2012 - 2018) has the aim to describe the influence of shifting coast on the way of settling and living of ancient man in the IML. The main questions to be answered are as follow: (i) Is coast development influenced by glaciations a result of interaction between endo- and exogenic (glaciological-, geological-, and geophysical) forces in general and at the local scale of morphological elements? (ii) Did ancient man adept to changes in natural circumstances and what did that mean for his social behavior and economy? (iii) Were forms of human society and economy in the IML primarily dependent on the natural environment with regard to geophysical and geological differences and related to post-glacial response of the earth crust? Detailed integrated studying of "key-areas", with attention to deep geology, will allow to get new insight of the impact of post-glacial shoreline changes and history of man on the coast in the IML with focus on his past (history of relations) and future (impact of climate change. The project is an international project, with participation of institutes all

  3. Savanna chimpanzees use tools to harvest the underground storage organs of plants.

    PubMed

    Hernandez-Aguilar, R Adriana; Moore, Jim; Pickering, Travis Rayne

    2007-12-01

    It has been hypothesized that plant underground storage organs (USOs) played key roles in the initial hominin colonization of savanna habitats, the development of the distinctive skull and tooth morphology of the genus Australopithecus, and the evolution of the genus Homo by serving as "fallback foods" exploited during periods of food shortage. These hypotheses have been tested mostly by morphological, isotopic, and microwear analyses of hominin bones and teeth. Archaeological evidence of USO digging technology is equivocal. Until now relevant data from studies of chimpanzees, useful in behavioral models of early hominins because of their phylogenetic proximity and anatomical similarities, have been lacking. Here we report on the first evidence of chimpanzees using tools to dig for USOs, suggesting that exploitation of such resources was within the cognitive and technological reach of the earliest hominins. Consistent with scenarios of hominin adaptation to savannas, these data come from Ugalla (Tanzania), one of the driest, most open and seasonal chimpanzee habitats. USOs are, however, exploited during the rainy season, well after the period of most likely food shortage, contradicting the specific prediction of fallback food hypotheses. The discovery that savanna chimpanzees use tools to obtain USOs contradicts yet another claim of human uniqueness and provides a model for the study of variables influencing USO use among early hominins.

  4. Surficial Geology and Landscape Development in Northern Frenchman Flat, Interim Summary and Soil Data

    SciTech Connect

    Raytheon Services Nevada Environmental Restoration and Waste Management Division

    1995-09-01

    This report summarizes geologic studies by Raytheon Services Nevada near the Area 5 Radioactive Waste Management Site at the Nevada Test Site. These studies are part of a program to satisfy data needs of (1) the Greater Confinement Disposal (GCD) Program Performance Assessment (PA), (2) the low-level waste (LLW) PA, and (3) the Resource Conservation and Recovery Act (RCRA) permit application. The geologic studies were integrated into a single program that worked toward a landscape evolution model of northern Frenchman Flat, with more detailed geologic studies of particular topics as needed. Only the Holocene tectonism and surficial geology components of the landscape model are presented in this report.

  5. From landscape to domain: Soils role in landscape classifications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil landscape classifications are designed to divide landscapes into units with significance for the provisioning and regulating of ecosystem services and the development of conservation plans for natural resources. More specifically, such classifications serve as the basis for stratifying manageme...

  6. Constraining landscape development of the Sri Lankan escarpment with cosmogenic nuclides in river sediment

    NASA Astrophysics Data System (ADS)

    Vanacker, V.; von Blanckenburg, F.; Hewawasam, T.; Kubik, P. W.

    2007-01-01

    Escarpments are prominent morphological features along high-elevation passive margins. Recent studies integrating geomorphology, thermochronology, and cosmogenic nuclide-based denudation rate estimates suggest a rapid phase of denudation immediately after the earliest stages of seafloor spreading, and subsequent slow denudation rates since. To constrain the geomorphic evolution of passive margins, we have examined the development of the Sri Lankan escarpment. Cosmogenic nuclide data on river sediment along a north-south transect across the southern escarpment reveal that the landscape is eroding ten times more rapidly in the escarpment zone (26 to 71 mm kyr - 1 ) than in the high-elevation plateau above it and in the lowland plain beneath it (2.6 to 6.2 mm kyr - 1 ). Unlike these low denudation rate areas, the escarpment denudation is strongly and linearly hill slope-dependent. This shows that denudation and retreat are tightly interlinked within the escarpment, which suggests that the escarpment is evolving by rift-parallel retreat, rather than by escarpment downwearing. Supporting evidence is provided by the morphology of rivers draining the escarpment zone. These have steep bedrock channels which show sharp and prominent knickpoints along their longitudinal profiles. It appears that fluvial processes are driving escarpment retreat, as rivers migrate headwards were they incise into the high-elevation plateau. However, the average catchment-wide denudation rates of the escarpment zone are low compared to the denudation rates that are estimated for constant escarpment retreat since rifting. In common with other escarpments worldwide, causes for this slow down can be tectonic change related to flexural bending of the lithosphere, climate change that would vary the degree of precipitation focused into the escarpment, or the decrease in the contributing catchment area, which would reduce the stream power available for fluvial erosion.

  7. The chromatin landscape of the moss Physcomitrella patens and its dynamics during development and drought stress.

    PubMed

    Widiez, Thomas; Symeonidi, Aikaterini; Luo, Chongyuan; Lam, Eric; Lawton, Michael; Rensing, Stefan A

    2014-07-01

    The moss Physcomitrella patens is an important model organism for evo-devo studies. Here, we determined the genome-wide chromatin landscape of five important histone three (H3) modifications (H3K4me3, H3K27me3, H3K27Ac, H3K9Ac and H3K9me2) and describe the changes to these histone marks in two contrasted situations, developmental transition and abiotic (drought) stress. Integrative analysis of these histone H3 modifications revealed their preferential association into 15 chromatin states (CS) in genic regions of the P. patens genome. Synergistic relationships that influence expression levels were revealed for the three activating marks H3K4me3, H3K27Ac and H3K9Ac, while an antagonistic relationship was found between CS containing the H3K27me3 and H3K27Ac marks, suggesting that H3K27 is a key indexing residue regarding transcriptional output. Concerning the alteration of histone marks in response to developmental transition (juvenile to adult) and drought stress, the three activating marks H3K4me3, H3K27Ac and H3K9Ac show significant changes in both situations. However, changes to H3K27me3 are central only for genes differentially expressed during development. Interestingly, genes induced during drought stress show significant histone mark toggling during developmental transition. This situation suggests that drought induced adult (gametophore expressed) genes are primed to respond to this stress during the juvenile to adult transition.

  8. Late Quaternary landscape development at the margin of the Pomeranian phase (MIS 2) near Lake Wygonin (Northern Poland)

    NASA Astrophysics Data System (ADS)

    Hirsch, Florian; Schneider, Anna; Nicolay, Alexander; Błaszkiewicz, Mirosław; Kordowski, Jarosław; Noryskiewicz, Agnieszka M.; Tyszkowski, Sebastian; Raab, Alexandra; Raab, Thomas

    2015-04-01

    In Central Europe, Late Quaternary landscapes experienced multiple phases of geomorphologic activity. In this study,we used a combined geomorphological, pedological, sedimentological and palynological approach to characterize landscape development after the Last Glacial Maximum (LGM) near Lake Wygonin in Northern Poland. The pedostratigraphical findings from soil pits and drillings were extrapolated using ground-penetrating radar (GPR) and electric resistivity tomography (ERT). During the Pomeranian phase, glacial and fluvioglacial processes dominated the landscape near Lake Wygonin. At the end of the glacial period, periglacial processes became relevant and caused the formation of ventifacts and coversands containing coated sand grains. At approximately 15,290-14,800 cal yr BP, a small pond formed in a kettle hole (profile BWI2). The lacustrine sediments lack eolian sand components and therefore indicate the decline of eolian processes during that time. The increase of Juniperus and rock-rose (Helianthemum) in the pollen diagram is a prominent marker of the Younger Dryas. At the end of the Younger Dryas, a partial reshaping of the landscape is indicated by abundant charcoal fragments in disturbed lake sediments. No geomorphologic activity since the beginning of the Holocene is documented in the terrestrial and wetland archives. The anthropogenic impact is reflected in the pollen diagram by the occurrence of rye pollen grains (Cerealia type, Secale cereale) and translocated soil sediments dated to 1560-1410 cal yr BP, proving agricultural use of the immediate vicinity. With the onset of land use, gully incision and the accumulation of colluvial fans reshaped the landscape locally. Since 540-460 cal yr BP, further gully incision in the steep forest tracks has been associated with the intensification of forestry. Outside of the gully catchments, the weakly podzolized Rubic Brunic Arenosols show no features of Holocene soil erosion. Reprinted from CATENA, Volume 124

  9. Development of hydrologic landscape regions for classifying hydrologic permanace and hydrological-ecological interactions

    EPA Science Inventory

    In a 2001 paper, Winter proposed the concept of the hydrologic landscape unit as a fundamental unit composed of an upland and lowland separated by a steeper slope. Winter suggested that this concept could be useful for hydrologic research, data analysis, and comparing hydrologic...

  10. Changing Pedagogic Codes in a Class of Landscape Architects Learning "Ecologically Sustainable Development"

    ERIC Educational Resources Information Center

    Lawson, G. M.

    2010-01-01

    Professional discourse in education has been the focus of research conducted mostly with teachers and professional practitioners, but the work of students in the built environment has largely been ignored. This article presents an analysis of students' visual discourse in the final professional year of a landscape architecture course in Brisbane,…

  11. Studying Wildlife at Local and Landscape Scales: Bachman's Sparrow at the Savannah River Site

    SciTech Connect

    Dunning, J.B.; Danielson, B.J.; Watts, B.D.; Liu, J.; Krementz, D.R.

    2000-10-01

    Mutual interests between land managers at SRS and scientists resulted in a landscape ecology study of Bachman's sparrow. The species is declining throughout it's range. The distribution of suitable habitats across the landscape may provide an explanation. The species occupies early successional and late successional savanna habitat. Modeling was closely linked to field observations to demonstrate how the species demographics change with the distribution and dynamics of habitats.

  12. Soil-landscape development and late Quaternary environmental change in coastal Estremadura, Portugal

    NASA Astrophysics Data System (ADS)

    Daniels, Michael; Haws, Jonathan; Benedetti, Michael; Bicho, Nuno

    2015-04-01

    This poster integrates soil-landscape analysis with archaeological survey and paleoenvironmental reconstruction. Soils in surface and buried contexts in Estremadura, Portugal, provide evidence of landscape stability and instability, relative age relationships between landforms, and general paleoenvironmental conditions during the late Quaternary. These factors provide insight into the distribution and condition of Paleolithic archaeological sites and help understand the record of human settlement in the region. Late Pleistocene and Holocene dunes extend inland approximately 10 km from coastal source regions. Surface soils in Holocene dunes under maritime pine (Pinus pinaster) forest exhibit A, E, C/Bh and A, C horizon sequences and classify as Quartzipsamments. Surface soils in late Pleistocene dunes exhibit A, E, Bh, Bhs, Bs horizon sequences and classify as Haplorthods. Both Pleistocene and Holocene dunes commonly bury a heavily weathered soil formed in calcareous sandstone. The boundary between underlying buried soils and overlying surface soils is characterized by a lag deposit of medium to coarse, moderately-rounded gravels, underlain immediately by subsurface Bt and Bss horizons. The lag deposit and absence of buried A horizons both indicate intense and/or prolonged surface erosion prior to burial by late Quaternary dunes. Soil-geomorphic relationships therefore suggest at least two distinct episodes of dune emplacement and subsequent landscape stability following an extensive episode late Pleistocene landscape instability and soil erosion. A conceptual model of soil-landscape evolution through the late Quaternary and Holocene results from the integration of soil profile data, proxy paleoenvironmental data, and the partial record of human settled as revealed in the archaeological record.

  13. Aerosol emissions by tropical forest and savanna biomass burning: Characteristic trace elements and fluxes

    SciTech Connect

    Echalar, F.; Gaudichet, A.; Cachier, H.

    1995-11-15

    This report characterizes and compares trace element emissions from fires of three different types of savannas and from the southwestern amazonian rain forest. This study tries to verify a fingerprint that may characterize savanna fires or tropical biomass burning.

  14. Implication of Forest-Savanna Dynamics on Biomass and Carbon Stock: Effectiveness of an Amazonian Ecological Station

    NASA Astrophysics Data System (ADS)

    Couto-Santos, F. R.; Luizao, F. J.

    2014-12-01

    The forests-savanna advancement/retraction process seems to play an important role in the global carbon cycle and in the climate-vegetation balance maintenance in the Amazon. To contribute with long term carbon dynamics and assess effectiveness of a protected area in reduce carbon emissions in Brazilian Amazon transitional areas, variations in forest-savanna mosaics biomass and carbon stock within Maraca Ecological Station (MES), Roraima/Brazil, and its outskirts non-protected areas were compared. Composite surface soil samples and indirect methods based on regression models were used to estimate aboveground tree biomass accumulation and assess vegetation and soil carbon stock along eleven 0.6 ha transects perpendicular to the forest-savanna limits. Aboveground biomass and carbon accumulation were influenced by vegetation structure, showing higher values within protected area, with great contribution of trees above 40 cm in diameter. In the savanna environments of protected areas, a higher tree density and carbon stock up to 30 m from the border confirmed a forest encroachment. This pointed that MES acts as carbon sink, even under variations in soil fertility gradient, with a potential increase of the total carbon stock from 9 to 150 Mg C ha-1. Under 20 years of fire and disturbance management, the results indicated the effectiveness of this protected area to reduce carbon emissions and mitigate greenhouse and climate change effects in a forest-savanna transitional area in Brazilian Northern Amazon. The contribution of this study in understanding rates and reasons for biomass and carbon variation, under different management strategies, should be considered the first approximation to assist policies of reducing emissions from deforestation and forest degradation (REDD) from underresearched Amazonian ecotone; despite further efforts in this direction are still needed. FINANCIAL SUPPORT: Boticário Group Foundation (Fundação Grupo Boticário); National Council for

  15. The role of savannas in the terrestrial Si cycle: A case-study from Lamto, Ivory Coast

    NASA Astrophysics Data System (ADS)

    Alexandre, Anne; Bouvet, Mickael; Abbadie, Luc

    2011-08-01

    Savannas currently occupy a fifth of the earth's land surface and are predicted to expand in the next few centuries at the expense of tropical forests, mainly as a result of deforestation and human fires. Can such a vegetation trend impact, through changes in plant Si cycling, the lithogenic silicon (LSi) release into soils (through chemical weathering) and the net dissolved Si (DSi) outputs from soils to stream water (through chemical denudation)? The first step of an investigation requires quantifying the net Si fluxes involved in the plant/soil system. Here, a schematic steady-state Si cycle, established for a tropical humid savanna (Lamto, Ivory Coast) that developed on a ferruginous soil and is subjected to annual fires, is presented. Erosion was assumed to be insignificant. LSi and biogenic Si (BSi under the form of phytoliths) pools were measured, and Si fluxes were estimated from Si concentrations and mass balance calculation. Identification of plant and soil phytoliths indicated that the soil BSi pool is in equilibrium with the current BSi input by the savanna. In the soil column, mixing between a young rapidly recycled BSi pool and an old stable BSi pool is attested by a mixing line equation. Storage of the old BSi pool is assimilated as a BSi output from the plant/soil system. A BSi output additionally occurs after annual fires, when ashes are exported. Both BSi outputs decrease as much the BSi dissolution. In order to uptake constant DSi flux, the savanna increases by three to eight times the net LSi release, depending upon the post-fire ash exportation scenario. A comparison between savanna and rainforest Si cycles that maximizes the differences in plant/soil systems and minimizes differences in climate is presented. The comparison revealed that BSi storage is higher in the savanna soil than in the rainforest soil, mainly due to BSi production that is twice higher in the savanna (127 vs 67 kg/ha/yr). The resulting LSi release that is enhanced by plant

  16. The role of savannas in the terrestrial Si cycle: A case-study from Lamto, Ivory Coast

    NASA Astrophysics Data System (ADS)

    Alexandre, A. E.; Abbadie, L.

    2011-12-01

    Savannas currently occupy a fifth of the earth's land surface and are predicted to expand in the next few centuries at the expense of tropical forests, mainly as a result of deforestation and human fires. Can such a vegetation trend impact, through changes in plant Si cycling, the lithogenic silicon (LSi) release into soils (through chemical weathering) and the net dissolved Si (DSi) outputs from soils to stream water (through chemical denudation)? The first step of an investigation requires quantifying the net Si fluxes involved in the plant/soil system. Here, a schematic steady-state Si cycle, established for a tropical humid savanna (Lamto, Ivory Coast) that developed on a ferruginous soil and is subjected to annual fires, is presented. Erosion was assumed to be insignificant. LSi and biogenic Si (BSi under the form of phytoliths) pools were measured, and Si fluxes were estimated from Si concentrations and mass balance calculation. Identification of plant and soil phytoliths indicated that the soil BSi pool is in equilibrium with the current BSi input by the savanna. In the soil column, mixing between a young rapidly recycled BSi pool and an old stable BSi pool is attested by a mixing line equation. Storage of the old BSi pool is assimilated as a BSi output from the plant/soil system. A BSi output additionally occurs after annual fires, when ashes are exported. Both BSi outputs decrease as much the BSi dissolution. In order to uptake constant DSi flux, the savanna increases by three to eight times the net LSi release, depending upon the post-fire ash exportation scenario. A comparison between savanna and rainforest Si cycles that maximizes the differences in plant/soil systems and minimizes differences in climate is presented. The comparison revealed that BSi storage is higher in the savanna soil than in the rainforest soil, mainly due to BSi production that is twice higher in the savanna (127 vs 67 kg/ha/yr). The resulting LSi release that is enhanced by plant

  17. Landscape disturbance from unconventional and conventional oil and gas development in the Marcellus Shale region of Pennsylvania, USA

    USGS Publications Warehouse

    Slonecker, Terry E.; Milheim, Lesley E.

    2015-01-01

    The spatial footprint of unconventional (hydraulic fracturing) and conventional oil and gas development in the Marcellus Shale region of the State of Pennsylvania was digitized from high-resolution, ortho-rectified, digital aerial photography, from 2004 to 2010. We used these data to measure the spatial extent of oil and gas development and to assess the exposure of the extant natural resources across the landscape of the watersheds in the study area. We found that either form of development: (1) occurred in ~50% of the 930 watersheds that defined the study area; (2) was closer to streams than the recommended safe distance in ~50% of the watersheds; (3) was in some places closer to impaired streams and state-defined wildland trout streams than the recommended safe distance; (4) was within 10 upstream kilometers of surface drinking water intakes in ~45% of the watersheds that had surface drinking water intakes; (5) occurred in ~10% of state-defined exceptional value watersheds; (6) occurred in ~30% of the watersheds with resident populations defined as disproportionately exposed to pollutants; (7) tended to occur at interior forest locations; and (8) had >100 residents within 3 km for ~30% of the unconventional oil and gas development sites. Further, we found that exposure to the potential effects of landscape disturbance attributable to conventional oil and gas development was more prevalent than its unconventional counterpart.

  18. Eco-hydrology driven fire regime in savanna.

    PubMed

    Ursino, Nadia

    2014-08-21

    Fire is an important evolutionary force and ecosystem consumer that shapes savanna composition. However, ecologists have not comprehensively explained the functioning and maintenance of flammable savannas. A new minimal model accounting for the interdependence between soil saturation, biomass growth, fuel availability and fire has been used to predict the increasing tree density and fire frequency along a Mean Annual Rainfall (MAR) gradient for a typical savanna. Cyclic fire recurrence is reproduced using a predator prey approach in which fire is the "predator" and vegetation is the "prey". For the first time, fire frequency is not defined a priori but rather arises from the composition of vegetation, which determines fuel availability and water limitation. Soil aridity affects fuel production and fuel composition, thus indirectly affecting the ecosystem vulnerability to fire and fire frequency. The model demonstrates that two distinct eco-hydrological states correspond to different fire frequencies: (i) at low MAR, grass is abundant and the impact of fire on the environment is enhanced by the large fuel availability, (ii) at higher MAR, tree density progressively increases and provides less fuel for fire, leading to more frequent and less destructive fires, and (iii) the threshold MAR that determines the transition between the two states and the fire frequency at high MAR are affected by the vulnerability of trees to grass fire. The eco-hydrology-driven predator-prey model originally predicts that the transition between dry and wet savanna is characterized by a shift in wildfire frequency driven by major differences in soil moisture available for plants and savanna structure. The shift and the role of fire in conserving savanna ecosystems could not have been predicted if fire was considered as an external forcing rather than an intrinsic property of the ecosystem. PMID:24727188

  19. Eco-hydrology driven fire regime in savanna.

    PubMed

    Ursino, Nadia

    2014-08-21

    Fire is an important evolutionary force and ecosystem consumer that shapes savanna composition. However, ecologists have not comprehensively explained the functioning and maintenance of flammable savannas. A new minimal model accounting for the interdependence between soil saturation, biomass growth, fuel availability and fire has been used to predict the increasing tree density and fire frequency along a Mean Annual Rainfall (MAR) gradient for a typical savanna. Cyclic fire recurrence is reproduced using a predator prey approach in which fire is the "predator" and vegetation is the "prey". For the first time, fire frequency is not defined a priori but rather arises from the composition of vegetation, which determines fuel availability and water limitation. Soil aridity affects fuel production and fuel composition, thus indirectly affecting the ecosystem vulnerability to fire and fire frequency. The model demonstrates that two distinct eco-hydrological states correspond to different fire frequencies: (i) at low MAR, grass is abundant and the impact of fire on the environment is enhanced by the large fuel availability, (ii) at higher MAR, tree density progressively increases and provides less fuel for fire, leading to more frequent and less destructive fires, and (iii) the threshold MAR that determines the transition between the two states and the fire frequency at high MAR are affected by the vulnerability of trees to grass fire. The eco-hydrology-driven predator-prey model originally predicts that the transition between dry and wet savanna is characterized by a shift in wildfire frequency driven by major differences in soil moisture available for plants and savanna structure. The shift and the role of fire in conserving savanna ecosystems could not have been predicted if fire was considered as an external forcing rather than an intrinsic property of the ecosystem.

  20. Impact of natural climate change and historical land use on landscape development in the Atlantic Forest of Rio de Janeiro, Brazil.

    PubMed

    Nehren, Udo; Kirchner, André; Sattler, Dietmar; Turetta, Ana Paula; Heinrich, Jürgen

    2013-01-01

    Climate variations and historical land use had a major impact on landscape development in the Brazilian Atlantic Forest (Mata Atlântica). In southeast Brazil, rainforest expanded under warm-humid climate conditions in the late Holocene, but have been dramatically reduced in historical times. Nevertheless, the numerous remaining forest fragments are of outstanding biological richness. In our research in the Atlantic Forest of Rio de Janeiro we aim at the reconstruction of the late Quaternary landscape evolution and an assessment of human impact on landscapes and rainforests. In this context, special focus is given on (a) effects of climate variations on vegetation cover, soil development, and geomorphological processes, and (b) spatial and temporal land use and landscape degradation patterns. In this paper we present some new results of our interdisciplinary research in the Serra dos Órgãos mountain range, state of Rio de Janeiro.

  1. Erosion and landscape development decouple strontium and sulfur in the transition to dominance by atmospheric inputs

    USGS Publications Warehouse

    Bern, C.R.; Porder, S.; Townsend, A.R.

    2007-01-01

    Weathering and leaching can progressively deplete the pools of soluble, rock-derived elements in soils and ecosystems over millennial time-scales, such that productivity increasingly relies on inputs from atmospheric deposition. This transition has been explored using strontium isotopes, which have been widely assumed to be a proxy for the provenance of other rock-derived elements. We compared rock versus atmospheric proportions of strontium to those for sulfur, a plant macronutrient, at several tropical forest sites in Hawaii and Costa Rica. Isotopic analyses reveal that sulfur is often decoupled from strontium in the transition to atmospheric dependence. Decoupling is likely the result of differences in chemical factors such as atmospheric input rates, mobility in the soil environment, and mineral weathering susceptibility. Strontium and sulfur decoupling appears to be accentuated by the physical process of erosion. Erosion rates are presumed to be high on the Osa Peninsula of Costa Rica, where the recent onset of rapid tectonic uplift has placed the landscape in a transient state. Decoupling is strong there, as erosion has rejuvenated the supply of rock-derived strontium but not sulfur. The landscape response to changes in tectonic uplift on the Osa Peninsula has produced decoupling at the landscape scale. Decoupling is more variable along a Hawaiian catena, presumably due to smaller scale variations in erosion rates and their influence on rejuvenation of rock-strontium inputs. These results illustrate how chemical and physical processes can interact to produce contrasting origins for different nutrient elements in soils and the ecosystems they support. ?? 2007 Elsevier B.V. All rights reserved.

  2. Seasonal Habitat Use by Greater Sage-Grouse (Centrocercus urophasianus) on a Landscape with Low Density Oil and Gas Development

    PubMed Central

    2016-01-01

    Fragmentation of the sagebrush (Artemisia spp.) ecosystem has led to concern about a variety of sagebrush obligates including the greater sage-grouse (Centrocercus urophasianus). Given the increase of energy development within greater sage-grouse habitats, mapping seasonal habitats in pre-development populations is critical. The North Park population in Colorado is one of the largest and most stable in the state and provides a unique case study for investigating resource selection at a relatively low level of energy development compared to other populations both within and outside the state. We used locations from 117 radio-marked female greater sage-grouse in North Park, Colorado to develop seasonal resource selection models. We then added energy development variables to the base models at both a landscape and local scale to determine if energy variables improved the fit of the seasonal models. The base models for breeding and winter resource selection predicted greater use in large expanses of sagebrush whereas the base summer model predicted greater use along the edge of riparian areas. Energy development variables did not improve the winter or the summer models at either scale of analysis, but distance to oil/gas roads slightly improved model fit at both scales in the breeding season, albeit in opposite ways. At the landscape scale, greater sage-grouse were closer to oil/gas roads whereas they were further from oil/gas roads at the local scale during the breeding season. Although we found limited effects from low level energy development in the breeding season, the scale of analysis can influence the interpretation of effects. The lack of strong effects from energy development may be indicative that energy development at current levels are not impacting greater sage-grouse in North Park. Our baseline seasonal resource selection maps can be used for conservation to help identify ways of minimizing the effects of energy development. PMID:27788202

  3. Phytolith analysis as a tool for palaeo-environmental studies: a case study of the reconstruction of the historical extent of oak savanna in the Willamette Valley, Oregon

    NASA Astrophysics Data System (ADS)

    Kirchholtes, Renske; van Mourik, Jan; Johnson, Bart

    2014-05-01

    Landscape-level restorations can be costly, so the effectiveness of the approach and the objectives of the restoration should be supported by a comprehensive investigation. The goal of the research presented here is to provide the basis for such a restoration effort using phytolith analyses. Fire suppression and loss of indigenous burning in the Willamette Valley, Oregon (USA) has led to near disappearance of the Oregon white oak savanna. Under suppressed fire regimes the shade-intolerant Garry oaks (Quercus garryana) are outcompeted by Douglas-fir (Pseudotsuga menziesii). As a consequence, the Oregon white oak savanna has been reduced to <5% of its former extent. This range contraction has had significant impacts on regional biodiversity due to habitat loss and fragmentation of the many savanna-dependent plant and animal species. Landscape-level restorations of oak savannas are needed to conserve biodiversity. Creating a more open landscape in which wildfires play a vital role, ties in with efforts to reduce fuel loads. Under a warming climate and changing precipitation patterns, reducing fire risk, fire intensity and fuel loading is critical. Frequent, low-intensity burning of both natural and Native American origin created open spaces in the otherwise densely forested hills and mountains of the Cascade Range. Thus, determining an appropriate "restoration point" (estimate of percent forest cover,) requires a pre-settlement paleoenvironmental reconstruction. However, the conventional indicators used in floristic reconstructions (pollen and spores) are seldom preserved in the dry, oxidized sediments of savannahs, meaning an alternative line of evidence is required for their historical study. Phytoliths are small yet robust silica particles produced by most plants. Many phytoliths take on cell shapes diagnostic of specific plant lineages, acting as indicators of their past presence. Unlike pollen grains, phytoliths readily preserve in well-drained soils during

  4. Effects of tree harvest on the stable-state dynamics of savanna and forest.

    PubMed

    Tredennick, Andrew T; Hanan, Niall P

    2015-05-01

    Contemporary theory on the maintenance and stability of the savanna biome has focused extensively on how climate and disturbances interact to affect tree growth and demography. In particular, the role of fire in reducing tree cover from climatic maxima is now well appreciated, and in certain cases, herbivory also strongly affects tree cover. However, in African savannas and forests, harvest of trees by humans for cooking and heating is an oft overlooked disturbance. Thus, we incorporate tree harvest into a population dynamic model of grasses, savanna saplings, savanna trees, and forest trees. We use assumptions about the differential demographic responses of savanna trees and forest trees to harvest to show how tree harvest influences tree cover, demography, and community composition. Tree harvest can erode the intrinsic basin of attraction for forest and make a state transition via fire to savanna more likely. The savanna state is generally resilient to all but high levels of tree harvest because of the resprouting abilities of savanna trees. In the absence of active fire suppression, our analysis suggests that we can expect to see large and potentially irreversible shifts from forest to savanna as demand increases for charcoal in sub-Saharan Africa. On the other hand, savanna tree species' traits promote savanna stability in the face of low to moderate harvest pressure. PMID:25905514

  5. Oil and Gas Development in Southwestern Wyoming - Energy Data and Services for the Wyoming Landscape Conservation Initiative (WLCI)

    USGS Publications Warehouse

    Biewick, Laura R.H.

    2009-01-01

    The purpose of this report is to explore current oil and gas energy development in the area encompassing the Wyoming Landscape Conservation Initiative. The Wyoming Landscape Conservation Initiative is a long-term science-based effort to ensure southwestern Wyoming's wildlife and habitat remain viable in areas facing development pressure. Wyoming encompasses some of the highest quality wildlife habitats in the Intermountain West. At the same time, this region is an important source of natural gas. Using Geographic Information System technology, energy data pertinent to the conservation decision-making process have been assembled to show historical oil and gas exploration and production in southwestern Wyoming. In addition to historical data, estimates of undiscovered oil and gas are included from the 2002 U.S. Geological Survey National Assessment of Oil and Gas in the Southwestern Wyoming Province. This report is meant to facilitate the integration of existing data with new knowledge and technologies to analyze energy resources development and to assist in habitat conservation planning. The well and assessment data can be accessed and shared among many different clients including, but not limited to, an online web-service for scientists and resource managers engaged in the Initiative.

  6. Indirect effects of domestic and wild herbivores on butterflies in an African savanna.

    PubMed

    Wilkerson, Marit L; Roche, Leslie M; Young, Truman P

    2013-10-01

    Indirect interactions driven by livestock and wild herbivores are increasingly recognized as important aspects of community dynamics in savannas and rangelands. Large ungulate herbivores can both directly and indirectly impact the reproductive structures of plants, which in turn can affect the pollinators of those plants. We examined how wild herbivores and cattle each indirectly affect the abundance of a common pollinator butterfly taxon, Colotis spp., at a set of long-term, large herbivore exclosure plots in a semiarid savanna in central Kenya. We also examined effects of herbivore exclusion on the main food plant of Colotis spp., which was also the most common flowering species in our plots: the shrub Cadaba farinosa. The study was conducted in four types of experimental plots: cattle-only, wildlife-only, cattle and wildlife (all large herbivores), and no large herbivores. Across all plots, Colotis spp. abundances were positively correlated with both Cadaba flower numbers (adult food resources) and total Cadaba canopy area (larval food resources). Structural equation modeling (SEM) revealed that floral resources drove the abundance of Colotis butterflies. Excluding browsing wildlife increased the abundances of both Cadaba flowers and Colotis butterflies. However, flower numbers and Colotis spp. abundances were greater in plots with cattle herbivory than in plots that excluded all large herbivores. Our results suggest that wild browsing herbivores can suppress pollinator species whereas well-managed cattle use may benefit important pollinators and the plants that depend on them. This study documents a novel set of ecological interactions that demonstrate how both conservation and livelihood goals can be met in a working landscape with abundant wildlife and livestock.

  7. Savanna fires increase rates and distances of seed dispersal by ants.

    PubMed

    Parr, C L; Andersen, A N; Chastagnol, C; Duffaud, C

    2007-02-01

    Myrmecochory (seed dispersal by ants) is a prominent dispersal mechanism in many environments, and can play a key role in local vegetation dynamics. Here we investigate its interaction with another key process in vegetation dynamics-fire. We examine ant dispersal of seeds immediately before and after experimental burning in an Australian tropical savanna, one of the world's most fire-prone ecosystems. Specifically, our study addressed the effects of burning on: (1) the composition of ants removing seeds, (2) number of seed removals, and (3) distance of seed dispersal. Fire led to higher rates of seed removal post-fire when compared with unburnt habitat, and markedly altered dispersal distance, with mean dispersal distance increasing more than twofold (from 1.6 to 3.8 m), and many distance dispersal events greater than the pre-fire maximum (7.55 m) being recorded. These changes were due primarily to longer foraging ranges of species of Iridomyrmex, most likely in response to the simplification of their foraging landscape. The significance of enhanced seed-removal rates and distance dispersal for seedling establishment is unclear because the benefits to plants in having their seeds dispersed by ants in northern Australia are poorly known. However, an enhanced removal rate would enhance any benefit of reduced predation by rodents. Similarly, the broader range of dispersal distances would appear to benefit plants in terms of reduced parent-offspring conflict and sibling competition, and the location of favourable seedling microsites. Given the high frequency of fire in Australian tropical savannas, enhanced benefits of seed dispersal by ants would apply for much of the year. PMID:17033801

  8. Geomorpho-Landscapes

    NASA Astrophysics Data System (ADS)

    Farabollini, Piero; Lugeri, Francesca; Amadio, Vittorio

    2014-05-01

    Landscape is the object of human perceptions, being the image of spatial organization of elements and structures: mankind lives the first approach with the environment, viewing and feeling the landscape. Many definitions of landscape have been given over time: in this case we refer to the Landscape defined as the result of interaction among physical, biotic and anthropic phenomena acting in a different spatial-temporal scale (Foreman & Godron) Following an Aristotelic approach in studying nature, we can assert that " Shape is synthesis": so it is possible to read the land features as the expression of the endogenous and exogenous processes that mould earth surfaces; moreover, Landscape is the result of the interaction of natural and cultural components, and conditions the spatial-temporal development of a region. The study of the Landscape offers results useful in order to promote sustainable development, ecotourism, enhancement of natural and cultural heritage, popularization of the scientific knowledge. In Italy, a very important GIS-based tool to represent the territory is the "Carta della Natura" ("Map of Nature", presently coordinated by the ISPRA) that aims at assessing the state of the whole Italian territory, analyzing Landscape. The methodology follows a holistic approach, taking into consideration all the components of a landscape and then integrating the information. Each individual landscape, studied at different scales, shows distinctive elements: structural, which depend on physical form and specific spatial organization; functional, which depend on relationships created between biotic and abiotic elements, and dynamic, which depend on the successive evolution of the structure. The identification of the landscape units, recognized at different scales of analysis, allows an evaluation of the state of the land, referring to the dual risk/resource which characterizes the Italian country. An interesting opportunity is to discover those areas of unusual

  9. Fuels and fire behavior dynamics on large-scale savanna fires in Kruger National Park, South Africa

    NASA Astrophysics Data System (ADS)

    Stocks, B. J.; van Wilgen, B. W.; Trollope, W. S. W.; McRae, D. J.; Mason, J. A.; Weirich, F.; Potgieter, A. L. F.

    1996-10-01

    Biomass characterization and fire behavior documentation were carried out on two large (>2000 ha) experimental fires conducted in arid savanna fuels in Kruger National Park in September 1992. Prefire fuel loads, fuel consumption, spread rates, flame zone characteristics, and in-fire and perimeter wind field dynamics were measured in order to determine overall energy release rates for each fire. Convection column dynamics were also measured in support of airborne trace gas and particulate measurements. Energy release rates varied significantly between the two fires, and this was strongly reflected in convection column development. The lower-intensity fire produced a weak, poorly defined smoke plume, while a well-developed column with a capping cumulus top developed during the higher intensity fire. Further experimental burning studies, in savannas with higher fuel loads, are recommended to further explore the fire behavior-convection column dynamics relationship investigated in this study.

  10. Developing a decision support tool for landscape planning and management to minimize land and water degradation in Volta basin

    NASA Astrophysics Data System (ADS)

    Vlek, Lulseged Tamene, Quang Bao Le, Jens Liebe, Paul L. G.

    2009-04-01

    Although many soil/water-landscape studies have been published in the last two decades, progress in developing operational tools for supporting landscape planning to minimize land and water degradation in developing regions is still modest. Some of the existing tools are very data demanding and/or too complicated to be useful to data scarce regions. A research group at the Center for Development Research (ZEF), University of Bonn has developed a LAndscape Management and Planning Tool (LAMPT) to facilitate land management decision making and landscape planning by optimization. Firstly, we used the Revised Universal Soil Loss Equation (RUSLE) and a Distributed Sediment Delivery Model (DSDM) in a GIS environment to estimate the spatial distribution of areas experiencing different levels of soil loss in the White Volta basin. The RUSLE is employed to map the spatial patterns of major sediment source areas based on data calibrated for the study region. As RUSLE only estimates the potential gross erosion of each grid cell, a DSDM is used to estimate the sediment delivery efficiency of each cell using flow distance and velocity along the flow path. The combined models allow a classification of sub-watersheds experiencing different levels of soil loss using a soil tolerance threshold suitable for the study areas (Burkina Faso and Ghana). The result shows that the majority of areas around north-eastern and eastern parts of the White Volta basin (mainly south-eastern Burkina Faso and upper east region of Ghana) are associated with high levels of sediment yield (over 15 t ha-1 yr-1). The main reason could be high population pressure, poor surface cover and relatively high slope of some of the areas in Ghana. On the other hand, the north-western and southern parts of the basin experience low levels of sediment yield (less than 5 t ha-1 yr-1) mainly due to their flat terrain and good surface cover that encourage sediment deposition rather than erosion. We revealed that a GIS

  11. Post-Gondwana geomorphic evolution of southwestern Africa: Implications for hte controls on landscape development from observations and numerical experiments

    NASA Technical Reports Server (NTRS)

    Gilchrist, Alan R.; Kooi, Henk; Beaumont, Christopher

    1994-01-01

    The relationship between morphology and surficial geology is used to quantify the denudation that has occurred across southwestern Africa sicne the fragmentation of Gondwana during the Early Mesozoic. Two main points emerge. Signficant denudation, of the order of kilometers, is widespread except in the Kalahari region of the continental interior. The denudation is systematically distributed so that the continental exterior catchment, draining directly to the Cape basin, is denuded to a greater depth than the interior catchment inland of the Great Escarpment. The analysis also implies tha the majority of the denudation occurred before the beginning of the Cenozoic for both teh exerior and interior catchments. Existing models of landscape development are reviewed, and implications of the denudation chronology are incorporated into a revised conceptual model. This revision implies tha thte primary effect of rifting on the subsequent landscape evolution is that it generates two distinct drainage regimes. A marginal upwarp, or rift flank uplift, separates rejuvenated rivers that drain into the subsiding rift from rivers in the continetal interior that are deflected but not rejuvenated. The two catchments evolve independently unless they are integrated by breaching of hte marginal upwarp. If this occurs, the exterior baselevel is communicated to the interior catchment that is denuded accordingly. Denudation rates generally decrease as the margin evolves, and this decrease is reinforced by the exposure of substrate that is resistant to denudation and/or a change to a more arid climate. The observations do not reveal a particular style of smaller-scale landscape evolution, sucha s escarpment retreat, that is responsible for the differential denudation across the region. It is proposed that numerical model experiments, which reflect the observational insights at the large scale, may identify the smaller-scale controls on escarpment development if the model and natural

  12. A New Application to Facilitate Post-Fire Recovery and Rehabilitation in Savanna Ecosystems

    NASA Technical Reports Server (NTRS)

    Carroll, Mark L.; Schnase, John L.; Weber, Keith T.; Brown, Molly E.; Gill, Roger L.; Haskett, George W.; Gardner, Tess A.

    2013-01-01

    The U.S. government spends an estimated $3billion per year to fight forest fires in the United States. Post-fire rehabilitation activities represent a small but essential portion of that total. The Rehabilitation Capability Convergence for Ecosystem Recovery (RECOVER) system is currently under development for Savanna ecosystems in the western U.S. The prototype of this system has been built and will have realworld testing during the summer 2013 fire season. When fully deployed, the RECOVER system will provide the emergency rehabilitation teams with critical and timely information for management decisions regarding stabilization and rehabilitation strategies.

  13. Landscape alterations influence differential habitat use of nesting buteos and ravens within sagebrush ecosystem: implications for transmission line development

    USGS Publications Warehouse

    Coates, Peter S.; Howe, Kristy B.; Casazza, Michael L.; Delehanty, David J.

    2014-01-01

    A goal in avian ecology is to understand factors that influence differences in nesting habitat and distribution among species, especially within changing landscapes. Over the past 2 decades, humans have altered sagebrush ecosystems as a result of expansion in energy production and transmission. Our primary study objective was to identify differences in the use of landscape characteristics and natural and anthropogenic features by nesting Common Ravens (Corvus corax) and 3 species of buteo (Swainson's Hawk [Buteo swainsoni], Red-tailed Hawk [B. jamaicensis], and Ferruginous Hawk [B. regalis]) within a sagebrush ecosystem in southeastern Idaho. During 2007–2009, we measured multiple environmental factors associated with 212 nest sites using data collected remotely and in the field. We then developed multinomial models to predict nesting probabilities by each species and predictive response curves based on model-averaged estimates. We found differences among species related to nesting substrate (natural vs. anthropogenic), agriculture, native grassland, and edge (interface of 2 cover types). Most important, ravens had a higher probability of nesting on anthropogenic features (0.80) than the other 3 species (Artemisia spp.), favoring increased numbers of nesting ravens and fewer nesting Ferruginous Hawks. Our results indicate that habitat alterations, fragmentation, and forthcoming disturbances anticipated with continued energy development in sagebrush steppe ecosystems can lead to predictable changes in raptor and raven communities.

  14. Community-Based Ecological Restoration: The Wingra Oak Savanna Project.

    ERIC Educational Resources Information Center

    Bader, Brian J.; Egan, Dave

    1999-01-01

    The University of Wisconsin-Madison Arboretum, a pioneer in ecological restoration, is involving the local community in restoring a site to its presettlement condition as an oak savanna. Besides providing the manual labor of restoration, volunteers learn about the land and the ecological processes that tie nature and culture together. A 60-hour…

  15. Restoring a disappearing ecosystem: the Longleaf Pine Savanna.

    SciTech Connect

    Harrington, Timothy B.; Miller, Karl V.; Park, Noreen

    2013-05-01

    Longleaf pine (Pinus palustris) savannas of the southeastern United States contain some of the worlds most diverse plant communities, along with a unique complement of wildlife. Their traditionally open canopy structure and rich understory of grasses and herbs were critical to their vigor. However, a long history of land-use practices such as logging, farming, and fire exclusion have reduced this once-widespread ecosystem to only 3 percent of its original range. At six longleaf pine plantations in South Carolina, Tim Harrington with the Pacific Northwest Research Station and collaborators with the Southern Research Station used various treatments (including prescribed burns, tree thinning, and herbicide applications) to alter the forest structure and tracked how successful each one was in advancing savanna restoration over a 14-year period. They found that typical planting densities for wood production in plantations create dense understory shade that excludes many native herbaceous species important to savannas and associated wildlife. The scientists found that although tree thinning alone did not result in sustained gains, a combination of controlled burning, thinning, and herbicide treatments to reduce woody plants was an effective strategy for recovering the savanna ecosystem. The scientists also found that these efforts must be repeated periodically for enduring benefits.

  16. Soil microbial communities following bush removal in a Namibian savanna

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Savanna ecosystems are subject to desertification and bush encroachment, which reduce the grazing value of the land and hence the carrying capacity for wildlife and livestock. In this study we examined the soil microbial communities under bush and grass in Namibia. We analyzed the soil at a chronose...

  17. Contrasting long-term records of biomass burning in wet and dry savannas of equatorial East Africa.

    PubMed

    Colombaroli, Daniele; Ssemmanda, Immaculate; Gelorini, Vanessa; Verschuren, Dirk

    2014-09-01

    Rainfall controls fire in tropical savanna ecosystems through impacting both the amount and flammability of plant biomass, and consequently, predicted changes in tropical precipitation over the next century are likely to have contrasting effects on the fire regimes of wet and dry savannas. We reconstructed the long-term dynamics of biomass burning in equatorial East Africa, using fossil charcoal particles from two well-dated lake-sediment records in western Uganda and central Kenya. We compared these high-resolution (5 years/sample) time series of biomass burning, spanning the last 3800 and 1200 years, with independent data on past hydroclimatic variability and vegetation dynamics. In western Uganda, a rapid (<100 years) and permanent increase in burning occurred around 2170 years ago, when climatic drying replaced semideciduous forest by wooded grassland. At the century time scale, biomass burning was inversely related to moisture balance for much of the next two millennia until ca. 1750 ad, when burning increased strongly despite regional climate becoming wetter. A sustained decrease in burning since the mid20th century reflects the intensified modern-day landscape conversion into cropland and plantations. In contrast, in semiarid central Kenya, biomass burning peaked at intermediate moisture-balance levels, whereas it was lower both during the wettest and driest multidecadal periods of the last 1200 years. Here, burning steadily increased since the mid20th century, presumably due to more frequent deliberate ignitions for bush clearing and cattle ranching. Both the observed historical trends and regional contrasts in biomass burning are consistent with spatial variability in fire regimes across the African savanna biome today. They demonstrate the strong dependence of East African fire regimes on both climatic moisture balance and vegetation, and the extent to which this dependence is now being overridden by anthropogenic activity. PMID:24677504

  18. Contrasting long-term records of biomass burning in wet and dry savannas of equatorial East Africa.

    PubMed

    Colombaroli, Daniele; Ssemmanda, Immaculate; Gelorini, Vanessa; Verschuren, Dirk

    2014-09-01

    Rainfall controls fire in tropical savanna ecosystems through impacting both the amount and flammability of plant biomass, and consequently, predicted changes in tropical precipitation over the next century are likely to have contrasting effects on the fire regimes of wet and dry savannas. We reconstructed the long-term dynamics of biomass burning in equatorial East Africa, using fossil charcoal particles from two well-dated lake-sediment records in western Uganda and central Kenya. We compared these high-resolution (5 years/sample) time series of biomass burning, spanning the last 3800 and 1200 years, with independent data on past hydroclimatic variability and vegetation dynamics. In western Uganda, a rapid (<100 years) and permanent increase in burning occurred around 2170 years ago, when climatic drying replaced semideciduous forest by wooded grassland. At the century time scale, biomass burning was inversely related to moisture balance for much of the next two millennia until ca. 1750 ad, when burning increased strongly despite regional climate becoming wetter. A sustained decrease in burning since the mid20th century reflects the intensified modern-day landscape conversion into cropland and plantations. In contrast, in semiarid central Kenya, biomass burning peaked at intermediate moisture-balance levels, whereas it was lower both during the wettest and driest multidecadal periods of the last 1200 years. Here, burning steadily increased since the mid20th century, presumably due to more frequent deliberate ignitions for bush clearing and cattle ranching. Both the observed historical trends and regional contrasts in biomass burning are consistent with spatial variability in fire regimes across the African savanna biome today. They demonstrate the strong dependence of East African fire regimes on both climatic moisture balance and vegetation, and the extent to which this dependence is now being overridden by anthropogenic activity.

  19. Wavelet-based detection of bush encroachment in a savanna using multi-temporal aerial photographs and satellite imagery

    NASA Astrophysics Data System (ADS)

    Shekede, Munyaradzi D.; Murwira, Amon; Masocha, Mhosisi

    2015-03-01

    Although increased woody plant abundance has been reported in tropical savannas worldwide, techniques for detecting the direction and magnitude of change are mostly based on visual interpretation of historical aerial photography or textural analysis of multi-temporal satellite images. These techniques are prone to human error and do not permit integration of remotely sensed data from diverse sources. Here, we integrate aerial photographs with high spatial resolution satellite imagery and use a discrete wavelet transform to objectively detect the dynamics in bush encroachment at two protected Zimbabwean savanna sites. Based on the recently introduced intensity-dominant scale approach, we test the hypotheses that: (1) the encroachment of woody patches into the surrounding grassland matrix causes a shift in the dominant scale. This shift in the dominant scale can be detected using a discrete wavelet transform regardless of whether aerial photography and satellite data are used; and (2) as the woody patch size stabilises, woody cover tends to increase thereby triggering changes in intensity. The results show that at the first site where tree patches were already established (Lake Chivero Game Reserve), between 1972 and 1984 the dominant scale of woody patches initially increased from 8 m before stabilising at 16 m and 32 m between 1984 and 2012 while the intensity fluctuated during the same period. In contrast, at the second site, which was formely grass-dominated site (Kyle Game Reserve), we observed an unclear dominant scale (1972) which later becomes distinct in 1985, 1996 and 2012. Over the same period, the intensity increased. Our results imply that using our approach we can detect and quantify woody/bush patch dynamics in savanna landscapes.

  20. Spatial Heterogeneity of Fine Root Biomass and Soil Carbon in a California Oak Savanna Illuminates Plant Functional Strategy Across Periods of High and Low Resource Supply

    NASA Astrophysics Data System (ADS)

    Koteen, L. E.; Raz Yaseef, N.; Baldocchi, D. D.

    2014-12-01

    We sampled isolated trees and tree clusters from a blue oak, Quercus douglasii, savanna in California USA to determine the spatial heterogeneity of fine root biomass and soil carbon across the landscape as a function of tree size, age and configuration. Our goal was to understand how fine root structure enables sustained ecosystem metabolism through a summer of very limited moisture availability and high heat, and facilitates resource acquisition during the short spring period of high resource supply. An additional goal was to provide a basis for upscaling root biomass and soil carbon to the landscape scale. We sampled trees of different size and tree clusters via a stratified sampling scheme that accounted for spatial heterogeneity in root biomass and soil carbon with lateral distance from the tree bole, or cluster center, and soil depth. We upscaled these estimates using site-specific information from a lidar survey conducted in the same region over a 36 ha area in 2009. We found that fine roots and soil carbon are spatially heterogeneous in their landscape distribution in oak savanna habitat, and that they greatly increase with tree size and age. We also found that Q. douglasii possesses a dimorphic fine root architecture, uniquely suited to the region's climatic constraints, and exhibits morphological plasticity among trees of different size, age, and physical setting.

  1. The constructed catchment 'Chicken Creek' - a landscape observatory to analyze processes and feedback mechanisms during initial ecosystem development

    NASA Astrophysics Data System (ADS)

    Elmer, Michael; Schaaf, Wolfgang; Gerwin, Werner; Hinz, Christoph

    2014-05-01

    We investigated the initial development of the landscape observatory 'Chicken Creek', Germany, an artificial catchment with well known boundary conditions and inner structures (Gerwin et al., 2011). Over a period of nine years, we observed considerable changes within the site (Elmer et al., 2013). Both internal and external factors could be identified as driving forces for the formation of structures and patterns in the catchment. Over time, secondary structures and patterns evolved and became more and more important. Invading biota and vegetation succession initialized feedback mechanisms resulting in pattern and habitat formation as well as in increased differentiation, heterogeneity and complexity that are typical characteristics of ecosystems (Schaaf et al., 2013). The processes and feedback mechanisms in the initial development of a new landscape may deviate in rates, intensity, and dominance from those known from mature ecosystems. It is therefore crucial to understand these early phases of ecosystem development and to disentangle the increasingly complex interactions between the evolving terrestrial and aquatic, biotic, and abiotic compartments of the system. Elmer M, Gerwin W, Schaaf W, Zaplata MK, Hohberg K, Nenov R, Bens O, Hüttl RF (2013): Dynamics of initial ecosystem development at the artificial catchment Chicken Creek, Lusatia, Germany. Environ Earth Sci 69, 491-505. Gerwin W, Schaaf W, Biemelt D, Winter S, Fischer A, Veste M, Hüttl RF (2011): Overview and first results of ecological monitoring at the artificial watershed Chicken Creek (Germany). Phys Chem Earth 36, 61-73. Schaaf W, Elmer M, Fischer A, Gerwin W, Nenov R, Pretsch H, Seifert S, Winter S, Zaplata MK (2013): Monitoring the formation of structures and patterns during initial development of an artificial catchment. Environ Monit Assess 185, 5965-5986.

  2. Planetary Landscape Geography

    NASA Astrophysics Data System (ADS)

    Hargitai, H.

    INTRODUCTION Landscape is one of the most often used category in physical ge- ography. The term "landshap" was introduced by Dutch painters in the 15-16th cen- tury. [1] The elements that build up a landscape (or environment) on Earth consists of natural (biogenic and abiogenic - lithologic, atmospheric, hydrologic) and artificial (antropogenic) factors. Landscape is a complex system of these different elements. The same lithology makes different landscapes under different climatic conditions. If the same conditions are present, the same landscape type will appear. Landscapes build up a hierarchic system and cover the whole surface. On Earth, landscapes can be classified and qualified according to their characteristics: relief forms (morphology), and its potential economic value. Aesthetic and subjective parameters can also be considered. Using the data from landers and data from orbiters we can now classify planetary landscapes (these can be used as geologic mapping units as well). By looking at a unknown landscape, we can determine the processes that created it and its development history. This was the case in the Pathfinder/Sojourner panoramas. [2]. DISCUSSION Planetary landscape evolution. We can draw a raw landscape develop- ment history by adding the different landscape building elements to each other. This has a strong connection with the planet's thermal evolution (age of the planet or the present surface materials) and with orbital parameters (distance from the central star, orbit excentricity etc). This way we can build a complex system in which we use differ- ent evolutional stages of lithologic, atmospheric, hydrologic and biogenic conditions which determine the given - Solar System or exoplanetary - landscape. Landscape elements. "Simple" landscapes can be found on asteroids: no linear horizon is present (not differentiated body, only impact structures), no atmosphere (therefore no atmospheric scattering - black sky as part of the landscape) and no

  3. Projected changes in distributions of Australian tropical savanna birds under climate change using three dispersal scenarios

    PubMed Central

    Reside, April E; VanDerWal, Jeremy; Kutt, Alex S

    2012-01-01

    Identifying the species most vulnerable to extinction as a result of climate change is a necessary first step in mitigating biodiversity decline. Species distribution modeling (SDM) is a commonly used tool to assess potential climate change impacts on distributions of species. We use SDMs to predict geographic ranges for 243 birds of Australian tropical savannas, and to project changes in species richness and ranges under a future climate scenario between 1990 and 2080. Realistic predictions require recognition of the variability in species capacity to track climatically suitable environments. Here we assess the effect of dispersal on model results by using three approaches: full dispersal, no dispersal and a partial-dispersal scenario permitting species to track climate change at a rate of 30 km per decade. As expected, the projected distributions and richness patterns are highly sensitive to the dispersal scenario. Projected future range sizes decreased for 66% of species if full dispersal was assumed, but for 89% of species when no dispersal was assumed. However, realistic future predictions should not assume a single dispersal scenario for all species and as such, we assigned each species to the most appropriate dispersal category based on individual mobility and habitat specificity; this permitted the best estimates of where species will be in the future. Under this “realistic” dispersal scenario, projected ranges sizes decreased for 67% of species but showed that migratory and tropical-endemic birds are predicted to benefit from climate change with increasing distributional area. Richness hotspots of tropical savanna birds are expected to move, increasing in southern savannas and southward along the east coast of Australia, but decreasing in the arid zone. Understanding the complexity of effects of climate change on species’ range sizes by incorporating dispersal capacities is a crucial step toward developing adaptation policies for the conservation of

  4. [Landscape and ecological genomics].

    PubMed

    2013-10-01

    Landscape genomics is the modern version of landscape genetics, a discipline that arose approximately 10 years ago as a combination of population genetics, landscape ecology, and spatial statistics. It studies the effects of environmental variables on gene flow and other microevolutionary processes that determine genetic connectivity and variations in populations. In contrast to population genetics, it operates at the level of individual specimens rather than at the level of population samples. Another important difference between landscape genetics and genomics and population genetics is that, in the former, the analysis of gene flow and local adaptations takes quantitative account of landforms and features of the matrix, i.e., hostile spaces that separate species habitats. Landscape genomics is a part of population ecogenomics, which, along with community genomics, is a major part of ecological genomics. One of the principal purposes of landscape genomics is the identification and differentiation of various genome-wide and locus-specific effects. The approaches and computation tools developed for combined analysis of genomic and landscape variables make it possible to detect adaptation-related genome fragments, which facilitates the planning of conservation efforts and the prediction of species' fate in response to expected changes in the environment. PMID:25508669

  5. [Landscape and ecological genomics].

    PubMed

    Tetushkin, E Ia

    2013-10-01

    Landscape genomics is the modern version of landscape genetics, a discipline that arose approximately 10 years ago as a combination of population genetics, landscape ecology, and spatial statistics. It studies the effects of environmental variables on gene flow and other microevolutionary processes that determine genetic connectivity and variations in populations. In contrast to population genetics, it operates at the level of individual specimens rather than at the level of population samples. Another important difference between landscape genetics and genomics and population genetics is that, in the former, the analysis of gene flow and local adaptations takes quantitative account of landforms and features of the matrix, i.e., hostile spaces that separate species habitats. Landscape genomics is a part of population ecogenomics, which, along with community genomics, is a major part of ecological genomics. One of the principal purposes of landscape genomics is the identification and differentiation of various genome-wide and locus-specific effects. The approaches and computation tools developed for combined analysis of genomic and landscape variables make it possible to detect adaptation-related genome fragments, which facilitates the planning of conservation efforts and the prediction of species' fate in response to expected changes in the environment. PMID:25474890

  6. Effect of Suburban Development and Landscape Position on Water Quality in Three Small Watersheds Within the Croton System, New York.

    NASA Astrophysics Data System (ADS)

    Hassett, J. M.; Endreny, T. A.; Wolosoff, S.; Adam, M.; Mitchell, M. J.

    2003-12-01

    Internal hydrological processes in suburban watersheds and their effects on water quality warrant investigation. Instrument clusters (throughfall collectors, suction lysimeters, monitoring wells, and shallow and deep piezometers) were installed at several locations within three small (50 - 70 ha) watersheds (one forested, two with different degrees of suburban development) in the Croton Watershed, southeastern New York. Biweekly and storm samples were analyzed for base cations, selected anions, and DOC over a one-year period. The topographic index (TI) quantified landscape position; flowpath analyses determined degree of development at each cluster, using % impervious cover as the metric. Water quality degradation was observed in sites with medium and high TI values; no such effect was observed along the ridges, i.e., low TI values. At medium TI values, areas with more than 5% impervious had degraded water quality. At high TI values, the water chemistry degradation appeared at 10% or greater impervious surface

  7. An artificial landscape-scale fishery in the Bolivian Amazon.

    PubMed

    Erickson, C L

    2000-11-01

    Historical ecologists working in the Neotropics argue that the present natural environment is an historical product of human intentionality and ingenuity, a creation that is imposed, built, managed and maintained by the collective multigenerational knowledge and experience of Native Americans. In the past 12,000 years, indigenous peoples transformed the environment, creating what we now recognize as the rich ecological mosaic of the Neotropics. The prehispanic savanna peoples of the Bolivian Amazon built an anthropogenic landscape through the construction of raised fields, large settlement mounds, and earthen causeways. I have studied a complex artificial network of hydraulic earthworks covering 525 km2 in the Baures region of Bolivia. Here I identify a particular form of earthwork, the zigzag structure, as a fish weir, on the basis of form, orientation, location, association with other hydraulic works and ethnographic analogy. The native peoples used this technology to harvest sufficient animal protein to sustain large and dense populations in a savanna environment.

  8. Pyromineralization of soil phosphorus in savanna ecosystems

    NASA Astrophysics Data System (ADS)

    Hartshorn, A.; Coetsee, C.; Chadwick, O.

    2007-12-01

    The weathering of rock supplies phosphorus (P) to ecosystems. Phosphorus limitation of ecosystems can be severe in thicker or older soils, where soil production rates from rock and therefore release of P is slower than in thinner or younger soils. Limitation may be especially pronounced in drier ecosystems that are experiencing increasing N deposition. Our savanna field sites in Kruger National Park, South Africa meet all three of these criteria: soil residence times average 250 ky, the climate is semiarid, and N inputs average 20 kg ha-1 y-1. Not all soil P is plant-available, and because our field sites experience occasional fires, our objectives were to quantify the importance of pyromineralization of soil P, the transfer by fire of soil P from recalcitrant to labile (HCO3- extractable) pools. We quantified these soil P pools using a modified Hedley scheme (an array of chemical extractants). Three sets of soils were fractionated: 1. soils from 10 profiles along an intensively studied hillslope, bracketing a pronounced structural and functional ecotone; 2. surface soils from these 10 profiles after a simulated burn; and 3. surface soils from the Shabeni Experimental Plots, where 4 fire treatments have been maintained for decades: no fire, annual fire in the dry season, triennial fire in the dry season, and triennial fire in the wet season. Total P for hillslope soils ranged from 45 to 135 g m-2 (to 50 cm depth) and from 8 to 15 g m-2 (to 5 cm depth). Total soil P was lowest in midslope soils, where upslope sandy soils dominated by broad-leafed vegetation shift abruptly to downslope clayey soils with fine-leafed vegetation. Simulated fire for the hillslope soils reduced total P slightly, but boosted labile P by 1.7 g m-2 (to 5 cm), representing 17% of total P in the surface 5 cm. This pyromineralization effect was not uniform across the hillslope: downslope soils gained about 50% more labile P than midslope soils with simulated burning. With a fire return interval

  9. Late Tertiary and Quaternary landscape development in the western Grand Canyon and western Arizona strip

    SciTech Connect

    Billingsley, G.H. ); Wenrich, K.J. . Federal Center); Blackerby, B. )

    1993-04-01

    New geologic mapping of the western Grand Canyon and the Arizona Strip region, northwest Arizona, reveals young fault scarps on all faults, horsts, and graben structures. Tectonic activity here was previously thought to be at least Miocene age and older. New K-Ar age data for basalt flows in this region provide a basis for determining the age of surficial deposits in relation to elevated structural landforms. The basalts range in age from middle Miocene to late Pleistocene (17 Ma to 0.14 Ma). The Miocene basalts are found in the western Grand Canyon area and are progressively younger in a northeast direction onto the Shivwits and Uinkaret Plateaus, a distance of about 100 km. The older basalts are generally petrographically and chemically distinct from younger basalts. Those younger than one million years have less olivine and are chemically more iron- and titanium-rich suggesting they are from less primitive magmas. Basalt flows in this region older than 1 million years, are cut by faults showing equal displacement of the underlying strata and the flows. Basalt flows younger than 1 million years show offsets as much as 12 to 100 m, less than two-thirds the offset of underlying strata, implying that most tectonic activity occurred within the last 1 to 2 million years. Late Pliocene and Pleistocene faulting has extensively modified the landscape by elevated parts of the terrain resulting in young surficial deposits in lowland areas and rejuvenation of drainages in upthrown fault blocks.

  10. Aquaculture in artificially developed wetlands in urban areas: an application of the bivariate relationship between soil and surface water in landscape ecology.

    PubMed

    Paul, Abhijit

    2011-01-01

    Wetlands show a strong bivariate relationship between soil and surface water. Artificially developed wetlands help to build landscape ecology and make built environments sustainable. The bheries, wetlands of eastern Calcutta (India), utilize the city sewage to develop urban aquaculture that supports the local fish industries and opens a new frontier in sustainable environmental planning research.

  11. Mediterranean savanna system: understanding and modeling of olive orchard.

    NASA Astrophysics Data System (ADS)

    Brilli, Lorenzo; Moriondo, Marco; Bindi, Marco

    2013-04-01

    Nowadays most of the studies on C and N exchange were focused on forest ecosystems and crop systems, while only few studies have been focused on so called "savanna systems". They are long-term agro-ecosystems (fruit trees, grapevines and olive trees, etc.) usually characterized by two different layers (ground vegetation and trees). Generally, there is a lack of knowledge about these systems due to their intrinsic structural complexity (different eco-physiological characteristics so as agricultural practices). However, given their long-term carbon storage capacity, these systems can play a fundamental role in terms of global C cycle. Among all of them, the role that olive trees can play in C sequestration should not be neglected, especially in Mediterranean areas where they typify the rural landscape and are widely cultivated (Loumou and Giourga, 2003). It is therefore fundamental modelling the C-fluxes exchanges coming from these systems through a tool able to well reproduce these dynamics in one of the most exposed areas to the risk of climate change (IPCC, 2007). In this work, 2 years of Net CO2 Ecosystem Exchange (NEE) measures from eddy covariance were used to test the biogeochemistry model DayCent. The study was conducted in a rain-fed olive orchard situated in Follonica, South Tuscany, Italy (42 ° 55'N, 10 ° 45'E), in an agricultural area near the coast. The instrumentation for flux measurement was placed 1.9 m above the canopy top (6.5 m from the ground) so that the footprint area, expressed as the area containing 90% of the observed flux, was almost entirely contained within the olive orchard limits (Brilli et al., in press). Ancillary slow sensors have included soil temperature profiles, global radiation, air temperature and humidity, rain gauge. Fluxes of sensible heat, latent heat, momentum and CO2 as well as ancillary data were derived at half-hourly time resolution. Specific soil (texture, current and historical land use and vegetation cover) and

  12. Landscape Architecture.

    ERIC Educational Resources Information Center

    American School and University, 1985

    1985-01-01

    Members of the American Society of Landscape Architects shape open spaces on the campuses of Georgetown University, District of Columbia; the University of Missouri; Auraria Higher Education Center, Colorado; and the University of Michigan. (MLF)

  13. Mars Landscapes

    NASA Video Gallery

    Spacecraft have studied the Martian surface for decades, giving Earthlings insights into the history, climate and geology of our nearest neighbor, Mars. These images are from "Mars Landscapes," a v...

  14. Human induced prehistoric and historical soil erosion and landscape development in Southwestern USA

    NASA Astrophysics Data System (ADS)

    Dotterweich, Markus; Ivester, Andrew H.; Hanson, Paul R.; Daniel, Larsen; Dye, David H.; Foster, Thomas H., II

    2015-04-01

    gathered data will be used to i) compare the spatial extent of prehistoric and historic erosion and the short-term and long-term pedological and geomorphological effects of subtle soil erosion against extreme events, ii) assess the feedback-mechanisms of soil erosion on soil fertility and measurable land use changes in prehistorical and historical times, and (iii) estimate the long term effects of soil erosion and sediment deposition on archaeological features. The outcome will provide a decisive step forward to gather new qualitative and quantitative information on soil erosion during the Native American land use period to be able to achieve a better understanding of the long-term human induced landscape evolution in the uplands of the Southeastern USA and deliver data for a better predicting of landscape evolution to future climatic shifts in precipitation regimes.

  15. The MCH training program: developing MCH leaders that are equipped for the changing health care landscape.

    PubMed

    Kavanagh, Laura; Menser, Michelle; Pooler, Jennifer; Mathis, Sheryl; Ramos, Lauren Raskin

    2015-02-01

    This article examines the success of the Maternal and Child Health (MCH) Bureau's MCH Training Program in producing the next generation of MCH leaders, equipped with interdisciplinary, leadership skills necessary for the changing health care landscape. A secondary data analysis of performance measure data (2007-2011) collected through the discretionary grant information system was performed. Grantees were grouped by grant program (n = 10) for this analysis. Outcomes of interest 5 years post-program completion included: (1) the percentage of long-term training program graduates who demonstrate field leadership; (2) the percentage of long-term trainees (LTT) who remain in MCH, work with underserved and/or vulnerable populations, or work in a public health agency/organization; and (3) the percentage of LTT working in an interdisciplinary manner to serve the MCH population. Summary output data on the number of LTT reached was also calculated. The number of LTT participating in the MCH Training Program increased between 2007 and 2011. Over 84% of LTT demonstrate field leadership 5 years after program completion, while 78.2% of LTT remain in MCH work and 83% are working with underserved or vulnerable populations. At 5-years post-program completion, over 75% of LTT are working in an interdisciplinary manner to serve the MCH population. The MCH Training Program has produced well-positioned leaders. Continued investment in the MCH Training Program is critical to ensure a well-trained pipeline of health professionals equipped to address the special health needs of MCH populations in an evolving health system. PMID:25095766

  16. The MCH training program: developing MCH leaders that are equipped for the changing health care landscape.

    PubMed

    Kavanagh, Laura; Menser, Michelle; Pooler, Jennifer; Mathis, Sheryl; Ramos, Lauren Raskin

    2015-02-01

    This article examines the success of the Maternal and Child Health (MCH) Bureau's MCH Training Program in producing the next generation of MCH leaders, equipped with interdisciplinary, leadership skills necessary for the changing health care landscape. A secondary data analysis of performance measure data (2007-2011) collected through the discretionary grant information system was performed. Grantees were grouped by grant program (n = 10) for this analysis. Outcomes of interest 5 years post-program completion included: (1) the percentage of long-term training program graduates who demonstrate field leadership; (2) the percentage of long-term trainees (LTT) who remain in MCH, work with underserved and/or vulnerable populations, or work in a public health agency/organization; and (3) the percentage of LTT working in an interdisciplinary manner to serve the MCH population. Summary output data on the number of LTT reached was also calculated. The number of LTT participating in the MCH Training Program increased between 2007 and 2011. Over 84% of LTT demonstrate field leadership 5 years after program completion, while 78.2% of LTT remain in MCH work and 83% are working with underserved or vulnerable populations. At 5-years post-program completion, over 75% of LTT are working in an interdisciplinary manner to serve the MCH population. The MCH Training Program has produced well-positioned leaders. Continued investment in the MCH Training Program is critical to ensure a well-trained pipeline of health professionals equipped to address the special health needs of MCH populations in an evolving health system.

  17. REMOTE SENSING AND SPATIALLY EXPLICIT LANDSCAPE-BASED NITROGEN MODELING METHODS DEVELOPMENT IN THE NEUSE RIVER BASIN, NC

    EPA Science Inventory

    The objective of this research was to model and map the spatial patterns of excess nitrogen (N) sources across the landscape within the Neuse River Basin (NRB) of North
    Carolina. The process included an initial land cover characterization effort to map landscape "patches" at ...

  18. African Savanna-Forest Boundary Dynamics: A 20-Year Study.

    PubMed

    Cuni-Sanchez, Aida; White, Lee J T; Calders, Kim; Jeffery, Kathryn J; Abernethy, Katharine; Burt, Andrew; Disney, Mathias; Gilpin, Martin; Gomez-Dans, Jose L; Lewis, Simon L

    2016-01-01

    Recent studies show widespread encroachment of forest into savannas with important consequences for the global carbon cycle and land-atmosphere interactions. However, little research has focused on in situ measurements of the successional sequence of savanna to forest in Africa. Using long-term inventory plots we quantify changes in vegetation structure, above-ground biomass (AGB) and biodiversity of trees ≥10 cm diameter over 20 years for five vegetation types: savanna; colonising forest (F1), monodominant Okoume forest (F2); young Marantaceae forest (F3); and mixed Marantaceae forest (F4) in Lopé National Park, central Gabon, plus novel 3D terrestrial laser scanning (TLS) measurements to assess forest structure differences. Over 20 years no plot changed to a new stage in the putative succession, but F1 forests strongly moved towards the structure, AGB and diversity of F2 forests. Overall, savanna plots showed no detectable change in structure, AGB or diversity using this method, with zero trees ≥10 cm diameter in 1993 and 2013. F1 and F2 forests increased in AGB, mainly as a result of adding recruited stems (F1) and increased Basal Area (F2), whereas F3 and F4 forests did not change substantially in structure, AGB or diversity. Critically, the stability of the F3 stage implies that this stage may be maintained for long periods. Soil carbon was low, and did not show a successional gradient as for AGB and diversity. TLS vertical plant profiles showed distinctive differences amongst the vegetation types, indicating that this technique can improve ecological understanding. We highlight two points: (i) as forest colonises, changes in biodiversity are much slower than changes in forest structure or AGB; and (ii) all forest types store substantial quantities of carbon. Multi-decadal monitoring is likely to be required to assess the speed of transition between vegetation types. PMID:27336632

  19. African Savanna-Forest Boundary Dynamics: A 20-Year Study

    PubMed Central

    Cuni-Sanchez, Aida; White, Lee J. T.; Calders, Kim; Jeffery, Kathryn J.; Abernethy, Katharine; Burt, Andrew; Disney, Mathias; Gilpin, Martin; Gomez-Dans, Jose L.; Lewis, Simon L.

    2016-01-01

    Recent studies show widespread encroachment of forest into savannas with important consequences for the global carbon cycle and land-atmosphere interactions. However, little research has focused on in situ measurements of the successional sequence of savanna to forest in Africa. Using long-term inventory plots we quantify changes in vegetation structure, above-ground biomass (AGB) and biodiversity of trees ≥10 cm diameter over 20 years for five vegetation types: savanna; colonising forest (F1), monodominant Okoume forest (F2); young Marantaceae forest (F3); and mixed Marantaceae forest (F4) in Lopé National Park, central Gabon, plus novel 3D terrestrial laser scanning (TLS) measurements to assess forest structure differences. Over 20 years no plot changed to a new stage in the putative succession, but F1 forests strongly moved towards the structure, AGB and diversity of F2 forests. Overall, savanna plots showed no detectable change in structure, AGB or diversity using this method, with zero trees ≥10 cm diameter in 1993 and 2013. F1 and F2 forests increased in AGB, mainly as a result of adding recruited stems (F1) and increased Basal Area (F2), whereas F3 and F4 forests did not change substantially in structure, AGB or diversity. Critically, the stability of the F3 stage implies that this stage may be maintained for long periods. Soil carbon was low, and did not show a successional gradient as for AGB and diversity. TLS vertical plant profiles showed distinctive differences amongst the vegetation types, indicating that this technique can improve ecological understanding. We highlight two points: (i) as forest colonises, changes in biodiversity are much slower than changes in forest structure or AGB; and (ii) all forest types store substantial quantities of carbon. Multi-decadal monitoring is likely to be required to assess the speed of transition between vegetation types. PMID:27336632

  20. African Savanna-Forest Boundary Dynamics: A 20-Year Study.

    PubMed

    Cuni-Sanchez, Aida; White, Lee J T; Calders, Kim; Jeffery, Kathryn J; Abernethy, Katharine; Burt, Andrew; Disney, Mathias; Gilpin, Martin; Gomez-Dans, Jose L; Lewis, Simon L

    2016-01-01

    Recent studies show widespread encroachment of forest into savannas with important consequences for the global carbon cycle and land-atmosphere interactions. However, little research has focused on in situ measurements of the successional sequence of savanna to forest in Africa. Using long-term inventory plots we quantify changes in vegetation structure, above-ground biomass (AGB) and biodiversity of trees ≥10 cm diameter over 20 years for five vegetation types: savanna; colonising forest (F1), monodominant Okoume forest (F2); young Marantaceae forest (F3); and mixed Marantaceae forest (F4) in Lopé National Park, central Gabon, plus novel 3D terrestrial laser scanning (TLS) measurements to assess forest structure differences. Over 20 years no plot changed to a new stage in the putative succession, but F1 forests strongly moved towards the structure, AGB and diversity of F2 forests. Overall, savanna plots showed no detectable change in structure, AGB or diversity using this method, with zero trees ≥10 cm diameter in 1993 and 2013. F1 and F2 forests increased in AGB, mainly as a result of adding recruited stems (F1) and increased Basal Area (F2), whereas F3 and F4 forests did not change substantially in structure, AGB or diversity. Critically, the stability of the F3 stage implies that this stage may be maintained for long periods. Soil carbon was low, and did not show a successional gradient as for AGB and diversity. TLS vertical plant profiles showed distinctive differences amongst the vegetation types, indicating that this technique can improve ecological understanding. We highlight two points: (i) as forest colonises, changes in biodiversity are much slower than changes in forest structure or AGB; and (ii) all forest types store substantial quantities of carbon. Multi-decadal monitoring is likely to be required to assess the speed of transition between vegetation types.

  1. Landscape evolution (A Review)

    PubMed Central

    Sharp, Robert P.

    1982-01-01

    Landscapes are created by exogenic and endogenic processes acting along the interface between the lithosphere and the atmosphere and hydrosphere. Various landforms result from the attack of weathering and erosion upon the highly heterogeneous lithospheric surface. Landscapes are dynamic, acutely sensitive to natural and artificial perturbation. Undisturbed, they can evolve through a succession of stages to a plain of low relief. Often, the progression of an erosion cycle is interrupted by tectonic or environmental changes; thus, many landscapes preserve vestiges of earlier cycles useful in reconstructing the recent history of Earth's surface. Landforms are bounded by slopes, so their evolution is best understood through study of slopes and the complex of factors controlling slope character and development. The substrate, biosphere, climatic environment, and erosive processes are principal factors. Creep of the disintegrated substrate and surface wash by water are preeminent. Some slopes attain a quasisteady form and recede parallel to themselves (backwearing); others become ever gentler with time (downwearing). The lovely convex/rectilinear/concave profile of many debris-mantled slopes reflects an interplay between creep and surface wash. Landscapes of greatest scenic attraction are usually those in which one or two genetic factors have strongly dominated or those perturbed by special events. Nature has been perturbing landscapes for billions of years, so mankind can learn about landscape perturbation from natural examples. Images

  2. In situ development of high-elevation, low-relief landscapes via duplex deformation in the Eastern Himalayan hinterland, Bhutan

    NASA Astrophysics Data System (ADS)

    Adams, B. A.; Whipple, K. X.; Hodges, K. V.; Heimsath, A. M.

    2016-02-01

    Prior studies have proposed tectonic and climatic mechanisms to explain surface uplift throughout the Bhutan Himalaya. While the resulting enigmatic, low-relief landscapes, elevated above deeply incised canyons, are a popular setting to test ideas of interacting tectonic and climatic forces, when and why these landscapes formed is still debated. We test the idea that these landscapes were created by a spatially variable and recent increase in rock uplift rate associated with the formation of structural duplexes at depth. We utilize a new suite of erosion rates derived from detrital cosmogenic nuclide techniques, geomorphic observations, and a landscape evolution model to demonstrate the viability of this hypothesis. Low-relief landscapes in Bhutan are eroding at a rate of ~70 m/Ma, while basins from surrounding steep landscapes yield erosion rates of ~950 m/Ma, demonstrating that this portion of the range is in a transient period of increasing relief. Applying insights from our erosion rates, we explore the influence of an active duplex on overlying topography using a landscape evolution model by imposing a high rock uplift rate in the middle of a mountain range. Our simulations show that low-relief landscapes with thick alluvial fills form upstream of convex knickpoints as rivers adjust to higher uplift rates downstream, a pattern consistent with geologic, geomorphic, and thermochronometric data from Bhutan. With our new erosion rates, reconstructed paleo-river profiles, and landscape evolution simulations, we show that the low-relief landscapes were formed in situ as they were uplifted ~800 m in the past ~0.8-1 Ma.

  3. Ecological release in lizard assemblages of neotropical savannas.

    PubMed

    Mesquita, Daniel Oliveira; Colli, Guarino Rinaldi; Vitt, Laurie J

    2007-08-01

    We compare lizard assemblages of Cerrado and Amazonian savannas to test the ecological release hypothesis, which predicts that niche dimensions and abundance should be greater in species inhabiting isolated habitat patches with low species richness (Amazonian savannas and isolated Cerrado patches) when compared with nonisolated areas in central Cerrado with greater species richness. We calculated microhabitat and diet niche breadths with data from 14 isolated Cerrado patches and Amazon savanna areas and six central Cerrado populations. Morphological data were compared using average Euclidean distances, and lizard abundance was estimated using the number of lizards captured in pitfall traps over an extended time period. We found no evidence of ecological release with respect to microhabitat use, suggesting that historical factors are better microhabitat predictors than ecological factors. However, data from individual stomachs indicate that ecological release occurs in these areas for one species (Tropidurus) but not others (Ameiva ameiva, Anolis, Cnemidophorus, and Micrablepharus), suggesting that evolutionary lineages respond differently to environmental pressures, with tropidurids being more affected by ecological factors than polychrotids, teiids, and gymnophthalmids. We found no evidence that ecological release occurs in these areas using morphological data. Based on abundance data, our results indicate that the ecological release (density compensation) hypothesis is not supported: lizard species are not more abundant in isolated areas than in nonisolated areas. The ecology of species is highly conservative, varying little from assemblage to assemblage. Nevertheless, increases in niche breadth for some species indicate that ecological release occurs as well. PMID:17437128

  4. Microbial Diversity in Cerrado Biome (Neotropical Savanna) Soils

    PubMed Central

    Pereira de Castro, Alinne; Sartori da Silva, Maria Regina Silveira; Quirino, Betania Ferraz; da Cunha Bustamante, Mercedes Maria; Krüger, Ricardo Henrique

    2016-01-01

    The Cerrado, the largest savanna region in South America, is located in central Brazil. Cerrado physiognomies, which range from savanna grasslands to forest formations, combined with the highly weathered, acidic clay Cerrado soils form a unique ecoregion. In this study, high-throughput sequencing of ribosomal RNA genes was combined with shotgun metagenomic analysis to explore the taxonomic composition and potential functions of soil microbial communities in four different vegetation physiognomies during both dry and rainy seasons. Our results showed that changes in bacterial, archaeal, and fungal community structures in cerrado denso, cerrado sensu stricto, campo sujo, and gallery forest soils strongly correlated with seasonal patterns of soil water uptake. The relative abundance of AD3, WPS-2, Planctomycetes, Thermoprotei, and Glomeromycota typically decreased in the rainy season, whereas the relative abundance of Proteobacteria and Ascomycota increased. In addition, analysis of shotgun metagenomic data revealed a significant increase in the relative abundance of genes associated with iron acquisition and metabolism, dormancy, and sporulation during the dry season, and an increase in the relative abundance of genes related to respiration and DNA and protein metabolism during the rainy season. These gene functional categories are associated with adaptation to water stress. Our results further the understanding of how tropical savanna soil microbial communities may be influenced by vegetation covering and temporal variations in soil moisture. PMID:26849674

  5. Plant-soil feedback in East-African savanna trees.

    PubMed

    Rutten, Gemma; Prati, Daniel; Hemp, Andreas; Fischer, Markus

    2016-02-01

    Research in savannas has focused on tree-grass interactions, whereas tree species coexistence received little attention. A leading hypothesis to explain tree coexistence is the Janzen-Connell model, which proposes an accumulation of host-specific enemies, e.g., soil organisms. While it has been shown in several non-savanna case studies that seedlings dispersed away from the mother perform better than seedlings that stay close (home-away effect), few studies tested whether foreign seedling species can replace own seedlings under conspecific adults (replacement effect). Some studies additionally tested for negative effects of conspecific biota (conspecific effect) to demonstrate the accumulation of enemies. We tested these effects by reciprocally growing seedlings of four tree species on soil collected beneath adults of all species, with and without applying a soil sterilization treatment. We found negative home-away effects suggesting that dispersal is advantageous and negative replacement effects suggesting species replacement under adults. While negative conspecific effects indicate accumulated enemies, positive heterospecific effects indicate an accumulation of mutualists rather than enemies for some species. We suggest that plant-soil feedbacks may well contribute to tree coexistence in savannas due to both negative conspecific and positive heterospecific feedbacks. PMID:27145605

  6. Regional insight into savanna hydrogeomorphology from termite mounds.

    PubMed

    Levick, Shaun R; Asner, Gregory P; Chadwick, Oliver A; Khomo, Lesego M; Rogers, Kevin H; Hartshorn, Anthony S; Kennedy-Bowdoin, Ty; Knapp, David E

    2010-01-01

    Global vegetation models predict the spread of woody vegetation in African savannas and grasslands under future climate scenarios, but they operate too broadly to consider hillslope-scale variations in tree-grass distribution. Topographically linked hydrology-soil-vegetation sequences, or catenas, underpin a variety of ecological processes in savannas, including responses to climate change. In this study, we explore the three-dimensional structure of hillslopes and vegetation, using high-resolution airborne LiDAR (Light Detection And Ranging), to understand the long-term effects of mean annual precipitation (MAP) on catena pattern. Our results reveal that the presence and position of hillslope hydrological boundaries, or seeplines, vary as a function of MAP through its long-term influence on clay redistribution. We suggest that changes in climate will differentially alter the structure of savannas through hydrological changes to the seasonally saturated grasslands downslope of seeplines. The mechanisms underlying future woody encroachment are not simply physiological responses to elevated temperatures and CO(2) levels but also involve hydrogeomorphological processes at the hillslope scale.

  7. Plant-soil feedback in East-African savanna trees.

    PubMed

    Rutten, Gemma; Prati, Daniel; Hemp, Andreas; Fischer, Markus

    2016-02-01

    Research in savannas has focused on tree-grass interactions, whereas tree species coexistence received little attention. A leading hypothesis to explain tree coexistence is the Janzen-Connell model, which proposes an accumulation of host-specific enemies, e.g., soil organisms. While it has been shown in several non-savanna case studies that seedlings dispersed away from the mother perform better than seedlings that stay close (home-away effect), few studies tested whether foreign seedling species can replace own seedlings under conspecific adults (replacement effect). Some studies additionally tested for negative effects of conspecific biota (conspecific effect) to demonstrate the accumulation of enemies. We tested these effects by reciprocally growing seedlings of four tree species on soil collected beneath adults of all species, with and without applying a soil sterilization treatment. We found negative home-away effects suggesting that dispersal is advantageous and negative replacement effects suggesting species replacement under adults. While negative conspecific effects indicate accumulated enemies, positive heterospecific effects indicate an accumulation of mutualists rather than enemies for some species. We suggest that plant-soil feedbacks may well contribute to tree coexistence in savannas due to both negative conspecific and positive heterospecific feedbacks.

  8. Regional insight into savanna hydrogeomorphology from termite mounds.

    PubMed

    Levick, Shaun R; Asner, Gregory P; Chadwick, Oliver A; Khomo, Lesego M; Rogers, Kevin H; Hartshorn, Anthony S; Kennedy-Bowdoin, Ty; Knapp, David E

    2010-01-01

    Global vegetation models predict the spread of woody vegetation in African savannas and grasslands under future climate scenarios, but they operate too broadly to consider hillslope-scale variations in tree-grass distribution. Topographically linked hydrology-soil-vegetation sequences, or catenas, underpin a variety of ecological processes in savannas, including responses to climate change. In this study, we explore the three-dimensional structure of hillslopes and vegetation, using high-resolution airborne LiDAR (Light Detection And Ranging), to understand the long-term effects of mean annual precipitation (MAP) on catena pattern. Our results reveal that the presence and position of hillslope hydrological boundaries, or seeplines, vary as a function of MAP through its long-term influence on clay redistribution. We suggest that changes in climate will differentially alter the structure of savannas through hydrological changes to the seasonally saturated grasslands downslope of seeplines. The mechanisms underlying future woody encroachment are not simply physiological responses to elevated temperatures and CO(2) levels but also involve hydrogeomorphological processes at the hillslope scale. PMID:20842197

  9. Insectivory of savanna chimpanzees (Pan troglodytes verus) at Fongoli, Senegal.

    PubMed

    Bogart, Stephanie L; Pruetz, Jill D

    2011-05-01

    Little is known about the behavior of chimpanzees living in savanna-woodlands, although they are of particular interest to anthropologists for the insight they can provide regarding the ecological pressures affecting early hominins living in similar habitats. Fongoli, Senegal, is the first site where savanna chimpanzees have been habituated for observational data collection and is the hottest and driest site where such observation of chimpanzees occurs today. Previously, indirect evidence suggested these chimpanzees consumed termites throughout the year, an unusual occurrence for western and eastern chimpanzees. Although meat eating by chimpanzees continues to receive much attention, their use of invertebrate prey has received less emphasis in scenarios of hominin evolution. Here, we further examine the invertebrate diet of Fongoli chimpanzees using direct observational methods and accounting for potential environmental influences. Termite feeding positively correlated with high temperatures. Fongoli chimpanzees spend more time obtaining termites than any other chimpanzee population studied, and this extensive insectivory contributes to the list of distinctive behaviors they display relative to chimpanzees living in more forested habitats. We suggest that savanna chimpanzees at Fongoli differ significantly from chimpanzees elsewhere as a result of the selective pressures characterizing their harsh environment, and this contrast provides an example of a viable referential model for better understanding human evolution. Specifically, our results support the hypotheses that invertebrate prey may have figured more prominently into the diet of early hominins in similar habitats, especially given that invertebrates are an important source of protein and other essential nutrients in a highly seasonal environment. PMID:21484757

  10. A LANDSCAPE DEVELOPMENT INTENSITY MAP OF MARYLAND, USA - 4/07

    EPA Science Inventory

    We present a map of human development intensity for central and eastern Maryland using an index derived from energy systems principles. Brown and Vivas developed a measure of the intensity of human development based on the nonrenewable energy use per unit area as an index to exp...

  11. Identifying Greater Sage-Grouse source and sink habitats for conservation planning in an energy development landscape.

    PubMed

    Kirol, Christopher P; Beck, Jeffrey L; Huzurbazar, Snehalata V; Holloran, Matthew J; Miller, Scott N

    2015-06-01

    Conserving a declining species that is facing many threats, including overlap of its habitats with energy extraction activities, depends upon identifying and prioritizing the value of the habitats that remain. In addition, habitat quality is often compromised when source habitats are lost or fragmented due to anthropogenic development. Our objective was to build an ecological model to classify and map habitat quality in terms of source or sink dynamics for Greater Sage-Grouse (Centrocercus urophasianus) in the Atlantic Rim Project Area (ARPA), a developing coalbed natural gas field in south-central Wyoming, USA. We used occurrence and survival modeling to evaluate relationships between environmental and anthropogenic variables at multiple spatial scales and for all female summer life stages, including nesting, brood-rearing, and non-brooding females. For each life stage, we created resource selection functions (RSFs). We weighted the RSFs and combined them to form a female summer occurrence map. We modeled survival also as a function of spatial variables for nest, brood, and adult female summer survival. Our survival-models were mapped as survival probability functions individually and then combined with fixed vital rates in a fitness metric model that, when mapped, predicted habitat productivity (productivity map). Our results demonstrate a suite of environmental and anthropogenic variables at multiple scales that were predictive of occurrence and survival. We created a source-sink map by overlaying our female summer occurrence map and productivity map to predict habitats contributing to population surpluses (source habitats) or deficits (sink habitat) and low-occurrence habitats on the landscape. The source-sink map predicted that of the Sage-Grouse habitat within the ARPA, 30% was primary source, 29% was secondary source, 4% was primary sink, 6% was secondary sink, and 31% was low occurrence. Our results provide evidence that energy development and avoidance of

  12. More than carbon sequestration: Biophysical climate benefits of restored savanna woodlands

    PubMed Central

    Syktus, Jozef I.; McAlpine, Clive A.

    2016-01-01

    Deforestation and climate change are interconnected and represent major environmental challenges. Here, we explore the capacity of regional-scale restoration of marginal agricultural lands to savanna woodlands in Australia to reduce warming and drying resulting from increased concentration of greenhouse gases. We show that restoration triggers a positive feedback loop between the land surface and the atmosphere, characterised by increased evaporative fraction, eddy dissipation and turbulent mixing in the boundary-layer resulting in enhanced cloud formation and precipitation over the restored regions. The increased evapotranspiration results from the capacity deep-rooted woody vegetation to access soil moisture. As a consequence, the increase in precipitation provides additional moisture to soil and trees, thus reinforcing the positive feedback loop. Restoration reduced the rate of warming and drying under the transient increase in the radiative forcing of greenhouse gas emissions (RCP8.5). At the continental scale, average summer warming for all land areas was reduced by 0.18 oC from 4.1 oC for the period 2056–2075 compared to 1986–2005. For the restored regions (representing 20% of Australia), the averaged surface temperature increase was 3.2 °C which is 0.82 °C cooler compared to agricultural landscapes. Further, there was reduction of 12% in the summer drying of the near-surface soil for the restored regions. PMID:27373738

  13. More than carbon sequestration: Biophysical climate benefits of restored savanna woodlands

    NASA Astrophysics Data System (ADS)

    Syktus, Jozef I.; McAlpine, Clive A.

    2016-07-01

    Deforestation and climate change are interconnected and represent major environmental challenges. Here, we explore the capacity of regional-scale restoration of marginal agricultural lands to savanna woodlands in Australia to reduce warming and drying resulting from increased concentration of greenhouse gases. We show that restoration triggers a positive feedback loop between the land surface and the atmosphere, characterised by increased evaporative fraction, eddy dissipation and turbulent mixing in the boundary-layer resulting in enhanced cloud formation and precipitation over the restored regions. The increased evapotranspiration results from the capacity deep-rooted woody vegetation to access soil moisture. As a consequence, the increase in precipitation provides additional moisture to soil and trees, thus reinforcing the positive feedback loop. Restoration reduced the rate of warming and drying under the transient increase in the radiative forcing of greenhouse gas emissions (RCP8.5). At the continental scale, average summer warming for all land areas was reduced by 0.18 oC from 4.1 oC for the period 2056–2075 compared to 1986–2005. For the restored regions (representing 20% of Australia), the averaged surface temperature increase was 3.2 °C which is 0.82 °C cooler compared to agricultural landscapes. Further, there was reduction of 12% in the summer drying of the near-surface soil for the restored regions.

  14. The initial phase of a Longleaf Pine-Wiregrass Savanna restoration: species establishment and community responses.

    SciTech Connect

    Aschenbach, Todd, A; Foster, Bryan, L.; Imm, Donald, W.

    2010-09-01

    AbstractAbstract The significant loss of the longleaf pine-wiregrass ecosystem in the southeastern United States has serious implications for biodiversity and ecosystem functioning. In response to this loss, we have initiated a long-term and landscape-scale restoration experiment at the 80,125 ha (310 mi2) Department of Energy Savannah River Site (SRS) located near Aiken, South Carolina. Aristida beyrichiana (wiregrass), an important and dominant grass (i.e., a “matrix” species) of the longleaf pine savanna understory, and 31 other herbaceous “non-matrix” species were planted at six locations throughout SRS in 2002 and 2003. Of the 36,056 transplanted seedlings, 75% were still alive in June 2004, while mean 1–2 year survival across all planted species was 48%. Lespedeza hirta (hairy lespedeza) exhibited the greatest overall survival per 3 ×3 m cell at 95%, whereas Schizachyrium spp. (little bluestem) exhibited the greatest mean cover among individual species at 5.9%. Wiregrass survival and cover were significantly reduced when planted with non-matrix species. Aggregate cover of all planted species in restored cells averaged 25.9% in 2006. High rates of survival and growth of the planted species resulted in greater species richness (SR), diversity, and vegetative cover in restored cells. Results suggest that the loss of the longleaf pine-wiregrass ecosystem may be ameliorated through restoration efforts and illustrate the positive impact of restoration plantings on biodiversity and vegetative cover.

  15. A novel approach for the development of tiered use biological criteria for rivers and streams in an ecologically diverse landscape.

    PubMed

    Bouchard, R William; Niemela, Scott; Genet, John A; Yoder, Chris O; Sandberg, John; Chirhart, Joel W; Feist, Mike; Lundeen, Benjamin; Helwig, Dan

    2016-03-01

    Water resource protection goals for aquatic life are often general and can result in under protection of some high quality water bodies and unattainable expectations for other water bodies. More refined aquatic life goals known as tiered aquatic life uses (TALUs) provide a framework to designate uses by setting protective goals for high quality water bodies and establishing attainable goals for water bodies altered by legally authorized legacy activities (e.g., channelization). Development of biological criteria or biocriteria typically requires identification of a set of least- or minimally-impacted reference sites that are used to establish a baseline from which goals are derived. Under a more refined system of stream types and aquatic life use goals, an adequate set of reference sites is needed to account for the natural variability of aquatic communities (e.g., landscape differences, thermal regime, and stream size). To develop sufficient datasets, Minnesota employed a reference condition approach in combination with an approach based on characterizing a stream's response to anthropogenic disturbance through development of a Biological Condition Gradient (BCG). These two approaches allowed for the creation of ecologically meaningful and consistent biocriteria within a more refined stream typology and solved issues related to small sample sizes and poor representation of minimally- or least-disturbed conditions for some stream types. Implementation of TALU biocriteria for Minnesota streams and rivers will result in consistent and protective goals that address fundamental differences among waters in terms of their potential for restoration. PMID:26920130

  16. A novel approach for the development of tiered use biological criteria for rivers and streams in an ecologically diverse landscape.

    PubMed

    Bouchard, R William; Niemela, Scott; Genet, John A; Yoder, Chris O; Sandberg, John; Chirhart, Joel W; Feist, Mike; Lundeen, Benjamin; Helwig, Dan

    2016-03-01

    Water resource protection goals for aquatic life are often general and can result in under protection of some high quality water bodies and unattainable expectations for other water bodies. More refined aquatic life goals known as tiered aquatic life uses (TALUs) provide a framework to designate uses by setting protective goals for high quality water bodies and establishing attainable goals for water bodies altered by legally authorized legacy activities (e.g., channelization). Development of biological criteria or biocriteria typically requires identification of a set of least- or minimally-impacted reference sites that are used to establish a baseline from which goals are derived. Under a more refined system of stream types and aquatic life use goals, an adequate set of reference sites is needed to account for the natural variability of aquatic communities (e.g., landscape differences, thermal regime, and stream size). To develop sufficient datasets, Minnesota employed a reference condition approach in combination with an approach based on characterizing a stream's response to anthropogenic disturbance through development of a Biological Condition Gradient (BCG). These two approaches allowed for the creation of ecologically meaningful and consistent biocriteria within a more refined stream typology and solved issues related to small sample sizes and poor representation of minimally- or least-disturbed conditions for some stream types. Implementation of TALU biocriteria for Minnesota streams and rivers will result in consistent and protective goals that address fundamental differences among waters in terms of their potential for restoration.

  17. Holocene Amazon rainforest-savanna dynamics and climatic implications: high-resolution pollen record from Laguna Loma Linda in eastern Colombia

    NASA Astrophysics Data System (ADS)

    Behling, Hermann; Hooghiemstra, Henry

    2000-10-01

    We present a high-resolution pollen record of a 695-cm-long sediment core from Laguna Loma Linda, located at an altitude of 310 m in the transitional zone between the savannas of the Llanos Orientales and the Amazonian rainforest, about 100 km from the Eastern Cordillera. Based on eight AMS 14C ages, the record represents the last 8700 14C yr BP. During the period from 8700 to 6000 14C yr BP the vegetation was dominated by grass savanna with only a few woody taxa, such as Curatella and Byrsonima, present in low abundance. Gallery forest along the drainage system apparently was poorly developed. Compared with today, precipitation must have been significantly lower and seasonality stronger. During the period from 6000 to 3600 14C yr BP, rainforest taxa increased markedly, reflecting an increase in precipitation. Rainforest and gallery forest taxa such as Moraceae/Urticaceae, Melastomataceae, Alchornea, Cecropia and Acalypha, were abundant, whereas Poaceae were reduced in frequency. From 3600 to 2300 14C yr BP rainforest taxa continued to increase; Moraceae/Urticaceae became very frequent, and Myrtaceae and Myrsine became common. Savanna vegetation decreased continuously. We infer that precipitation was still increasing, and that the length of the annual dry period possibly shortened. From 2300 14C yr BP onwards, grass savanna (mainly represented by Poaceae) expanded and Mauritia palms became frequent. This reflects increased human impact on the vegetation.

  18. Structural control in sinkhole development and speleogenesis: a case study from the High Murge karst landscape (Apulia, Italy)

    NASA Astrophysics Data System (ADS)

    Pepe, M.; Parise, M.

    2012-04-01

    The Murge plateau is the main karst sector of Apulia, an almost entirely carbonate region of SE Italy. It can be, in turn, subdivided into two sectors: High Murge, the inland plateau, where remnants of an ancient tropical karst are still recognizable; and Low Murge, closer to the Adriatic Sea, with smoother karst morphologies and landforms, but, at the same time, hosting some of the longest underground karst system in the region (Parise, 1998, 2006). Even though showing low energy relief, the landscape of High Murge is very articulated when examined at greater detail, with several interesting karst features. Among these, sinkholes are definitely the most significant, showing a variety of typologies and, at the same time, a high frequency, both as individual features and as coalescent landforms, giving origin to more complex depressions (Parise, 2011). Previous studies carried out in the High Murge through morphometric analysis of the main sinkholes identified on the 1:25,000 scale topographic maps from the Italian Army Geographical Institute indicated their likely genesis in a low relief cockpit karst (Sauro, 1991). Over such landscape, developed in Upper Tertiary, a hydrographic pattern was superimposed, that partly opened some of the depressions, also dismantling sectors of the karst relief and producing talus deposits (Caldara & Ciaranfi, 1988). In the present work we take into consideration the southern countryside of Ruvo di Puglia. Choice of the area, which extends over 15 km2, was dictated by presence of a high number of sinkholes, and of several important caves with prevailing vertical development, including the deepest pit ever explored in Apulia (Grave della Ferratella, depth - 320 m). The cave is nowadays not accessible, due to clogging caused by land use changes during the 80's. Based upon extensive field surveys and interpretation of multi-year aerial photographs (time range 1955-2003), integrated by surveying in selected caves, the main hydro

  19. Structural, physiognomic and above-ground biomass variation in savanna-forest transition zones on three continents - how different are co-occurring savanna and forest formations?

    NASA Astrophysics Data System (ADS)

    Veenendaal, E. M.; Torello-Raventos, M.; Feldpausch, T. R.; Domingues, T. F.; Gerard, F.; Schrodt, F.; Saiz, G.; Quesada, C. A.; Djagbletey, G.; Ford, A.; Kemp, J.; Marimon, B. S.; Marimon-Junior, B. H.; Lenza, E.; Ratter, J. A.; Maracahipes, L.; Sasaki, D.; Sonke, B.; Zapfack, L.; Villarroel, D.; Schwarz, M.; Yoko Ishida, F.; Gilpin, M.; Nardoto, G. B.; Affum-Baffoe, K.; Arroyo, L.; Bloomfield, K.; Ceca, G.; Compaore, H.; Davies, K.; Diallo, A.; Fyllas, N. M.; Gignoux, J.; Hien, F.; Johnson, M.; Mougin, E.; Hiernaux, P.; Killeen, T.; Metcalfe, D.; Miranda, H. S.; Steininger, M.; Sykora, K.; Bird, M. I.; Grace, J.; Lewis, S.; Phillips, O. L.; Lloyd, J.

    2015-05-01

    Through interpretations of remote-sensing data and/or theoretical propositions, the idea that forest and savanna represent "alternative stable states" is gaining increasing acceptance. Filling an observational gap, we present detailed stratified floristic and structural analyses for forest and savanna stands located mostly within zones of transition (where both vegetation types occur in close proximity) in Africa, South America and Australia. Woody plant leaf area index variation was related to tree canopy cover in a similar way for both savanna and forest with substantial overlap between the two vegetation types. As total woody plant canopy cover increased, so did the relative contribution of middle and lower strata of woody vegetation. Herbaceous layer cover declined as woody cover increased. This pattern of understorey grasses and herbs progressively replaced by shrubs as the canopy closes over was found for both savanna and forests and on all continents. Thus, once subordinate woody canopy layers are taken into account, a less marked transition in woody plant cover across the savanna-forest-species discontinuum is observed compared to that inferred when trees of a basal diameter > 0.1 m are considered in isolation. This is especially the case for shrub-dominated savannas and in taller savannas approaching canopy closure. An increased contribution of forest species to the total subordinate cover is also observed as savanna stand canopy closure occurs. Despite similarities in canopy-cover characteristics, woody vegetation in Africa and Australia attained greater heights and stored a greater amount of above-ground biomass than in South America. Up to three times as much above-ground biomass is stored in forests compared to savannas under equivalent climatic conditions. Savanna-forest transition zones were also found to typically occur at higher precipitation regimes for South America than for Africa. Nevertheless, consistent across all three continents coexistence

  20. Effects of Urban Development on Water Quality in the Piedmont of North Carolina: Association of Landscape Variables With Water Quality

    NASA Astrophysics Data System (ADS)

    Harned, D. A.; Cuffney, T. F.

    2005-12-01

    An assessment of effects of urban development on water quality in the Piedmont of North Carolina is part of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program. Thirty sites along a gradient of undeveloped to fully urbanized basins were selected using geographic information analysis to control variability in natural factors that influence water quality. Data collected include nutrient, pesticide, ion, and dissolved-oxygen concentrations, temperature, pH, specific conductance, streamflow, stage, habitat characteristics, and algal, benthic invertebrate, and fish communities. Sampling for water chemistry ranged from two samples (at 20 sites) to six samples (at 10 sites) per year from October 2002 to September 2003. Geomorphic and biological data were collected once in each basin. An index that integrates information on human influences, including land cover, population, and socioeconomic characteristics was used to define the urban gradient and to select sites. Relations among landscape, streamflow, temperature, and water-chemistry variables were analyzed to define urban effects on water quality. Distinct patterns of association occurred between landscape variables and water quality. An increase in urban index is associated with increases in pH (r=0.60), specific conductance (0.72), sulfate (0.68), a multiple-constituent chemical index (0.91), and a pesticide index (0.76). Landscape characteristics correlated with water quality in a similar manner. Increasing basin population density is associated with higher pH (0.55, 1990; 0.56, 2000), specific conductance (0.71, 1990), chloride (0.66, 1990), sulfate (0.72), and pesticides (0.71, 1990; 0.68, 2000). This pattern also is reflected in household density (pH (0.60), chemical index (0.87), and pesticide index (0.68)); in the total percentage of developed land in the basin (specific conductance (0.85), chloride (0.77), sulfate (0.81), total nitrogen (0.50), chemical index (0.84), and pesticide

  1. Carbon monitoring of tree encroachment in Argentine savanna

    NASA Astrophysics Data System (ADS)

    Gonzalez-Roglich, M.; Swenson, J. J.

    2013-12-01

    Land cover change dynamics alter ecosystem and climate functioning primarily through changes in matter cycles and energy fluxes. Woody plant encroachment in semiarid rangelands is a widespread process of land cover change driven by a combination of local land use practices and global environmental changes. Increases in woody plant cover alter the distribution of carbon and can affect water and nutrient s in the ecosystem. Rangelands comprise almost 45% of the global land surface, yet our understanding of the effects of woody plant encroachment is limited, in most cases, to fine resolution studies of the northern hemisphere. In this study we analyzed the consequences of woody plant encroachment on ecosystem carbon stocks at a regional scale (30,000 km2) across the transitional zone of the Western Pampas grasslands and the Caldenal Savannas of Argentina. A space-for-time substitution approach was used to analyze changes in C stocks in the woody plant, grass, litter and soil organic carbon pools along an encroachment gradient. We found a significant increase in ecosystem C stocks along the encroachment gradient, with mean values of 4.5, 8.4, 12.4, and 16.5 kgC/m2 for grasslands, shrublands, open and closed forests respectively. As in most semiarid systems, soil organic C is the single largest pool in the ecosystem, containing between 63 and 71% of the total C (1.5 m depth). Woody plant percent cover and soil texture (i.e. percent silt content), where the two primary factors accounting for the variability of C in the ecosystem, together explaining 81.0% and 84.7% of the variability in soil organic C and total ecosystem C stocks, respectively. This is the first study that assess the effect of woody plant encroachment at a regional scale in the Southern Hemisphere, finding important gains in ecosystem C stocks with the increase in woody plants cover. The very simple models presented here are a very valuable tool for rapid field assessment, and if combined with remotely

  2. Simulating Groundwater-Plant-Atmosphere Interactions in a Semiarid Savanna

    NASA Astrophysics Data System (ADS)

    Gou, S.; Miller, G. R.

    2013-12-01

    Groundwater serves as one of the main water sources for deep rooted phreatophytic vegetation. Such vegetation acts as the linkage between groundwater, land surface and atmosphere. Through plant groundwater uptake and hydraulic redistribution (HR), the dynamics of relatively deep groundwater can influence ET and soil moisture of top soil layers. In this work, we first developed a plant scale model to simulate groundwater uptake and HR driven by the potential gradients along the groundwater-soil-plant-atmosphere continuum (GSPAC). The model included a new plant water stress function based on the 'vulnerability curve' theory in order to integrate the influences of both soil water and groundwater on transpiration. The model was calibrated and validated with measured ET, soil moisture, and leaf water potential data and was able to capture both energy and water dynamics along the GSPAC. We then coupled this plant scale model into a spatial distributed groundwater-land surface model (ParFlow.CLM). The revisions to ParFlow.CLM allow it to explicitly describe root water uptake and HR of different species, allowing for the study of how plant groundwater use and HR influence regional water budget and climate. This new uptake formulation was applied to simulate a heterogeneous savanna system at an AmeriFlux site in California. The site is dominated by blue oaks which can access both soil water and groundwater and grasses which only depend on soil water. The results match previous field measurements indicating that the oaks use most soil water during wet season and switch to groundwater use in dry season to buffer the impacts of drought. Therefore, the water and energy dynamics at this site showed the soil moisture controlled pattern in wet season, and the vegetation and groundwater controlled pattern in dry season. With HR, the rainfall is distributed into deeper soil in wet season by hydraulic descent. Such water will be lifted into shallower soil to promote transpiration in

  3. Exploring water cycle dynamics by sampling multiple stable water isotope pools in a developed landscape in Germany

    NASA Astrophysics Data System (ADS)

    Orlowski, Natalie; Kraft, Philipp; Pferdmenges, Jakob; Breuer, Lutz

    2016-09-01

    A dual stable water isotope (δ2H and δ18O) study was conducted in the developed (managed) landscape of the Schwingbach catchment (Germany). The 2-year weekly to biweekly measurements of precipitation, stream, and groundwater isotopes revealed that surface and groundwater are isotopically disconnected from the annual precipitation cycle but showed bidirectional interactions between each other. Apparently, snowmelt played a fundamental role for groundwater recharge explaining the observed differences to precipitation δ values. A spatially distributed snapshot sampling of soil water isotopes at two soil depths at 52 sampling points across different land uses (arable land, forest, and grassland) revealed that topsoil isotopic signatures were similar to the precipitation input signal. Preferential water flow paths occurred under forested soils, explaining the isotopic similarities between top- and subsoil isotopic signatures. Due to human-impacted agricultural land use (tilling and compression) of arable and grassland soils, water delivery to the deeper soil layers was reduced, resulting in significant different isotopic signatures. However, the land use influence became less pronounced with depth and soil water approached groundwater δ values. Seasonally tracing stable water isotopes through soil profiles showed that the influence of new percolating soil water decreased with depth as no remarkable seasonality in soil isotopic signatures was obvious at depths > 0.9 m and constant values were observed through space and time. Since classic isotope evaluation methods such as transfer-function-based mean transit time calculations did not provide a good fit between the observed and calculated data, we established a hydrological model to estimate spatially distributed groundwater ages and flow directions within the Vollnkirchener Bach subcatchment. Our model revealed that complex age dynamics exist within the subcatchment and that much of the runoff must has been stored

  4. Pathology Residency Programme of a Developing Country--Landscape of Last 25 Years

    ERIC Educational Resources Information Center

    Siddiqui, Imran; Ali, Natasha; Kayani, Naila

    2016-01-01

    We report the evolution of a residency programme in Pathology from a developing country. This article highlights the historical perspective of our application procedure, the number of inductions, the programme framework, acheivements and limitations.

  5. Effects of landscape-based green infrastructure on stormwater runoff in suburban developments

    EPA Science Inventory

    The development of impervious surfaces in urban and suburban catchments affects their hydrological behavior by decreasing infiltration, increasing peak hydrograph response following rainfall events, and ultimately increasing the total volume of water and mass of pollutants reachi...

  6. Understanding the ecological complexity of semi-arid savannas using remote sensing

    NASA Astrophysics Data System (ADS)

    Huang, Cho-Ying

    Savannas are ecosystems with a background herbaceous layer and intermittently distributed woody plants. A large body of literature has revealed that the ecological processes within savannas are complex and the spatial pattern and abundance of woody and herbaceous plants through time may be influenced by various factors. This dissertation research consists of three studies demonstrating the feasibility of utilizing remote sensing techniques to better understand the ecological complexity of semisavannas in southern Arizona, USA. The first study investigated the impacts of recent fire disturbance on structural changes of woody plants at varying scales. Results indicated that while field canopy cover and remote sensing woody cover fraction were strong predictors of woody biomass at local and landscape scales, respectively, fire history can significantly alter the nature of these relationships. This work suggested that simple predictions of woody biomass from field and remote sensing cover measures without considering disturbance will underestimate biomass in mature undisturbed settings, and overestimate biomass in recently disturbed locations in most cases. The second study investigated the ecological stability by implementing a top-down approach to analyze 21 years (1984--2005) of Landsat satellite data. This work suggested that a stable system needed to receive sufficient precipitation for basic plant growth, to be on coarse-textured and shallow soils that can efficiently store precipitation but inhibit the proliferation of woody plants, and to be on east facing slopes which can support clement microclimate. The perspectives gained from this study will enable us to target fine-scale field studies seeking to address circumstances conferring ecosystem stability; and improve predictions of potential carbon stocks in drylands. The third study derived the unique temporal and spatial signatures of vegetation [the Normalized Difference Vegetation Index (NDVI)] and

  7. Obstacles to Enhancing Professional Development with Digital Tools in Rural Landscapes

    ERIC Educational Resources Information Center

    Hunt-Barron, Sarah; Tracy, Kelly N.; Howell, Emily; Kaminski, Rebecca

    2015-01-01

    This case study examines the use of online tools, including blogs, as a means of enhancing face-to-face professional development in writing instruction for teachers in rural districts. Since many rural districts serve large physical areas that are geographically distant from larger metropolitan areas and/or colleges and universities, teachers in…

  8. University Continuing Education in a Neoliberal Landscape: Developments in England and Aotearoa New Zealand

    ERIC Educational Resources Information Center

    Bowl, Marion

    2010-01-01

    This paper explores the impact of changing higher education policies and funding on university adult and continuing education in England and Aotearoa New Zealand. It discusses some of the contextual factors contributing to sustaining continuing education in New Zealand, against the tide of developments elsewhere, and in spite of its subjection to…

  9. The Position of Human Resource Developers in the New Learning Landscape: A Discussion Paper. Working Paper.

    ERIC Educational Resources Information Center

    Johnston, Robyn

    Despite increased attention to learning within the workplace and investigation into the distribution and nature of learning-related activities, how these trends have impacted the role of human resource (HR) professionals has been less extensively examined. Studies examining their role indicate that HR development (HRD) positions name traditional…

  10. MID-ATLANTIC COASTAL STREAMS STUDY: STATISTICAL DESIGN FOR REGIONAL ASSESSMENT AND LANDSCAPE MODEL DEVELOPMENT

    EPA Science Inventory

    A network of stream-sampling sites was developed for the Mid-Atlantic Coastal Plain (New Jersey through North Carolina) a collaborative study between the U.S. Environmental Protection Agency and the U.S. Geological Survey. A stratified random sampling with unequal weighting was u...

  11. MID-ATLANTIC COASTAL STREAMS STUDY: STATISTICAL DESIGN FOR REGIONAL ASSESSMENT AND LANDSCAPE MODEL DEVELOPMENT

    EPA Science Inventory

    A network of stream-sampling sites was developed for the Mid-Atlantic Coastal Plain (New Jersey through North Carolina) as part of collaborative research between the U.S. Environmental Protection Agency and the U.S. Geological Survey. A stratified random sampling with unequal wei...

  12. Reconciling Agricultural Needs with Biodiversity and Carbon Conservation in a Savanna Transformation Frontier

    NASA Astrophysics Data System (ADS)

    Spiegel, M. P.; Estes, L. D.; Caylor, K. K.; Searchinger, T.

    2015-12-01

    Zambia is a major hotspot for agricultural development in the African savannas, which will be targeted for agricultural expansion to relieve food shortages and economic insecurity in the next few decades. Recent scholarship rejects the assumption that the large reserves of arable land in the African savannas could be converted to cropland with low ecological costs. In light of these findings, the selection of land for agricultural expansion must consider not only its potential productivity, but also the increase in greenhouse gas emissions and biodiversity loss that would result from the land conversion. To examine these tradeoffs, we have developed a multi-objective optimization technique to seek scenarios for agricultural development in Zambia that simultaneously achieve production targets and minimize carbon, biodiversity, and economic cost constraints, while factoring in the inter-annual variability in crop production in this highly uncertain climate. Potential production is determined from well-characterized yield potential estimates while robust metrics of biodiversity and high resolution mapping of carbon storage provide fine scale estimates of ecological impact. We draw production targets for individual crops from potential development pathways, primarily export, commodity-crop driven expansion and identify ecologically responsible agricultural development scenarios that are resilient to climate change and meet these demands. In order to achieve a doubling of production of nine key crops, assuming a modest 20% overall increase in yield potential, we find a range of scenarios that use less than 1600 km2 of new land without infringing on any protected areas or exceeding 6.7 million tons of carbon emissions.

  13. Landscape development in an hyperarid sandstone environment along the margins of the Dead Sea fault: Implications from dated rock falls

    USGS Publications Warehouse

    Matmon, A.; Shaked, Y.; Porat, N.; Enzel, Y.; Finkel, R.; Lifton, N.; Boaretto, E.; Agnon, A.

    2005-01-01

    In this study, we explored the spatial and temporal relations between boulders and their original in-situ locations on sandstone bedrock cliffs. This was accomplished by combining field observations with dating methods using cosmogenic isotopes (10Be and 14C) and optically stimulated luminescence (OSL). Our conclusions bear both on the landscape evolution and cliff retreat process in the hyperarid region of Timna and on the methodology of estimating exposure ages using cosmogenic isotopes. We recognize three discrete rock fall events, at 31 ka, 15 ka, and 4 ka. In this hyperarid region, the most plausible triggering mechanism for rock fall events is strong ground acceleration caused by earthquakes generated by the nearby Dead Sea fault (DSF). Our record, however, under represents the regional earthquake record implying that ongoing development of detachment cracks prior to the triggering event might be slower than the earthquake cycle. Cliff retreat rates calculated using the timing of rock fall events and estimated thickness of rock removed in each event range between 0.14 m ky-1 and 2 m ky-1. When only full cycles are considered, we derive a more realistic range of 0.4 m ky-1 to 0.7 m ky-1. These rates are an order of magnitude faster than the calculated rate of surface lowering in the area. We conclude that sandstone cliffs at Timna retreat through episodic rock fall events that preserve the sharp, imposing, landscape characteristic to this region and that ongoing weathering of the cliff faces is minor. A 10%-20% difference in the 10Be concentrations in samples from matching boulder and cliff faces that have identical exposure histories and are located only a few meters apart indicates that cosmogenic nuclide production rates are sensitive to shielding and vary spatially over short distances. However, uncertainties associated with age calculations yielded boulder and matching cliff face ages that are similar within 1 ??. The use of external constraints in the

  14. CO2 fluxes in converting a tropical savanna to a managed ecosystem

    NASA Astrophysics Data System (ADS)

    Bristow, Mila; Hutley, Lindsay; Beringer, Jason; Livesley, Stephen; Arndt, Stefan

    2013-04-01

    Clearing and burning of tropical savanna is a globally significant emission of greenhouse gas although there is large uncertainty relating to the magnitude of this flux. Australia's tropical savannas occupy over 25% of the continental land mass and they significantly influence the national greenhouse gas budget. The tropical savanna region is also earmarked as one potential area of agricultural expansion in Australia given predicted rainfall declines across southern agricultural regions. It is currently unknown what impact a conversion of savanna woodlands to agricultural cropping will have on carbon and water budgets. We measured continuous CO2 exchange using eddy covariance flux towers before, during and after a land use change event in a savanna woodland in the Northern Territory of Australia. Our experimental design included flux measurement in an uncleared savanna and at a second savanna site prior to, during clearing and conversion to agricultural land. In addition, we measured the biomass of the savanna vegetation to quantify loss of standing carbon during conversion. The uncleared savanna was a weak net sink annually (~0.5 t C ha-1yr-1). In the 5 months prior to clearing, the late dry season to the early wet season (Oct 2011 to Mar 2012), the analogue savanna site was also a weak sink (mean daily sink ~0.05 t C ha-1 d-1). Clearing shifted the site to a net source of CO2. It remained a permanent CO2 source regardless of subsequent weather events, with pulses of increased respiration associated with rainfall events. The cleared debris (63 t biomass ha-1) was burnt in the late dry season a process that took 10 days (burning, stock piling, re-burning). Using savanna specific fuel emission factors we calculated the emissions from this fire event assuming all above ground, and 90% below-ground biomass was incinerated. The burning released a further 25.1 t C ha-1 from cleared debris, plus 6.3 t C ha-1 as a net emission as measured by the tower, generating huge CO2

  15. Creating a fuels baseline and establishing fire frequency relationships to develop a landscape management strategy at the Savannah River Site.

    SciTech Connect

    Parresol, Bernard R.; Shea, Dan; Ottmar, Roger.

    2006-10-01

    USDA Forest Service Proceedings RMRS-P-41. pp 351-366. Abstract—The Savannah River Site is a Department of Energy Nuclear Defense Facility and a National Environmental Research Park located in the upper coastal plain of South Carolina. Prescribed burning is conducted on 15,000 to 20,000 ac annually. We modifi ed standard forest inventory methods to incorporate a complete assessment of fuel components on 622 plots, assessing coarse woody debris, ladder fuels, and the litter and duff layers. Because of deficiencies in south-wide data on litter-duff bulk densities, which are the fuels most often consumed in prescribed fires, we developed new bulk density relationships. Total surface fuel loading across the landscape ranged from 0.8 to 48.7 tons/ac. The variables basal area, stand age, and site index were important in accounting for variability in ladder fuel, coarse woody debris, and litter-duff for pine types. For a given pine stand condition, litter-duff loading decreased in direct proportion to the number of burns in the preceding thirty years. Ladder fuels for loblolly and longleaf increased in direct proportion to the years since the last prescribed burn. The pattern of fuel loading on the SRS reflects stand dynamics, stand management and fire management. It is suggested that the Forest Inventory and Analysis Program can easily modify sampling protocols to incorporate collection of fuels data.

  16. Combining laser microdissection and RNA-seq to chart the transcriptional landscape of fungal development

    PubMed Central

    2012-01-01

    Background During sexual development, filamentous ascomycetes form complex, three-dimensional fruiting bodies for the protection and dispersal of sexual spores. Fruiting bodies contain a number of cell types not found in vegetative mycelium, and these morphological differences are thought to be mediated by changes in gene expression. However, little is known about the spatial distribution of gene expression in fungal development. Here, we used laser microdissection (LM) and RNA-seq to determine gene expression patterns in young fruiting bodies (protoperithecia) and non-reproductive mycelia of the ascomycete Sordaria macrospora. Results Quantitative analysis showed major differences in the gene expression patterns between protoperithecia and total mycelium. Among the genes strongly up-regulated in protoperithecia were the pheromone precursor genes ppg1 and ppg2. The up-regulation was confirmed by fluorescence microscopy of egfp expression under the control of ppg1 regulatory sequences. RNA-seq analysis of protoperithecia from the sterile mutant pro1 showed that many genes that are differentially regulated in these structures are under the genetic control of transcription factor PRO1. Conclusions We have generated transcriptional profiles of young fungal sexual structures using a combination of LM and RNA-seq. This allowed a high spatial resolution and sensitivity, and yielded a detailed picture of gene expression during development. Our data revealed significant differences in gene expression between protoperithecia and non-reproductive mycelia, and showed that the transcription factor PRO1 is involved in the regulation of many genes expressed specifically in sexual structures. The LM/RNA-seq approach will also be relevant to other eukaryotic systems in which multicellular development is investigated. PMID:23016559

  17. The enhancer landscape during early neocortical development reveals patterns of dense regulation and co-option.

    PubMed

    Wenger, Aaron M; Clarke, Shoa L; Notwell, James H; Chung, Tisha; Tuteja, Geetu; Guturu, Harendra; Schaar, Bruce T; Bejerano, Gill

    2013-08-01

    Genetic studies have identified a core set of transcription factors and target genes that control the development of the neocortex, the region of the human brain responsible for higher cognition. The specific regulatory interactions between these factors, many key upstream and downstream genes, and the enhancers that mediate all these interactions remain mostly uncharacterized. We perform p300 ChIP-seq to identify over 6,600 candidate enhancers active in the dorsal cerebral wall of embryonic day 14.5 (E14.5) mice. Over 95% of the peaks we measure are conserved to human. Eight of ten (80%) candidates tested using mouse transgenesis drive activity in restricted laminar patterns within the neocortex. GREAT based computational analysis reveals highly significant correlation with genes expressed at E14.5 in key areas for neocortex development, and allows the grouping of enhancers by known biological functions and pathways for further studies. We find that multiple genes are flanked by dozens of candidate enhancers each, including well-known key neocortical genes as well as suspected and novel genes. Nearly a quarter of our candidate enhancers are conserved well beyond mammals. Human and zebrafish regions orthologous to our candidate enhancers are shown to most often function in other aspects of central nervous system development. Finally, we find strong evidence that specific interspersed repeat families have contributed potentially key developmental enhancers via co-option. Our analysis expands the methodologies available for extracting the richness of information found in genome-wide functional maps.

  18. Structural, physiognomic and aboveground biomass variation in savanna-forest transition zones on three continents. How different are co-occurring savanna and forest formations?

    NASA Astrophysics Data System (ADS)

    Veenendaal, E. M.; Torello-Raventos, M.; Feldpausch, T. R.; Domingues, T. F.; Gerard, F.; Schrodt, F.; Saiz, G.; Quesada, C. A.; Djagbletey, G.; Ford, A.; Kemp, J.; Marimon, B. S.; Marimon-Junior, B. H.; Lenza, E.; Ratter, J. A.; Maracahipes, L.; Sasaki, D.; Sonké, B.; Zapfack, L.; Villarroel, D.; Schwarz, M.; Yoko Ishida, F.; Gilpin, M.; Nardoto, G. B.; Affum-Baffoe, K.; Arroyo, L.; Bloomfield, K.; Ceca, G.; Compaore, H.; Davies, K.; Diallo, A.; Fyllas, N. M.; Gignoux, J.; Hien, F.; Johnson, M.; Mougin, E.; Hiernaux, P.; Killeen, T.; Metcalfe, D.; Miranda, H. S.; Steininger, M.; Sykora, K.; Bird, M. I.; Grace, J.; Lewis, S.; Phillips, O. L.; Lloyd, J.

    2014-03-01

    Through interpretations of remote sensing data and/or theoretical propositions, the idea that forest and savanna represent "alternative stable states" is gaining increasing acceptance. Filling an observational gap, we present detailed stratified floristic and structural analyses for forest and savanna stands mostly located within zones of transition (where both vegetation types occur in close proximity) in Africa, South America and Australia. Woody plant leaf area index variation was related in a similar way to tree canopy cover for both savanna and forest with substantial overlap between the two vegetation types. As total woody plant canopy cover increased, so did the contribution of middle and lower strata of woody vegetation to this total. Herbaceous layer cover also declined as woody cover increased. This pattern of understorey grasses and herbs being progressively replaced by shrubs as canopy closure occurs was found for both savanna and forests and on all continents. Thus, once subordinate woody canopy layers are taken into account, a less marked transition in woody plant cover across the savanna-forest species discontinuum is observed compared to that implied when trees of a basal diameter > 0.1m are considered in isolation. This is especially the case for shrub-dominated savannas and in taller savannas approaching canopy closure. An increased contribution of forest species to the total subordinate cover is also observed as savanna stand canopy closure occurs. Despite similarities in canopy cover characteristics, woody vegetation in Africa and Australia attained greater heights and stored a greater concentration of above ground biomass than in South America. Up to three times as much aboveground biomass is stored in forests compared to savannas under equivalent climatic conditions. Savanna/forest transition zones were also found to typically occur at higher precipitation regimes for South America than for Africa. Nevertheless, coexistence was found to be

  19. Geomorpho-Landscapes

    NASA Astrophysics Data System (ADS)

    Farabollini, Piero; Lugeri, Francesca; Amadio, Vittorio

    2014-05-01

    Landscape is the object of human perceptions, being the image of spatial organization of elements and structures: mankind lives the first approach with the environment, viewing and feeling the landscape. Many definitions of landscape have been given over time: in this case we refer to the Landscape defined as the result of interaction among physical, biotic and anthropic phenomena acting in a different spatial-temporal scale (Foreman & Godron) Following an Aristotelic approach in studying nature, we can assert that " Shape is synthesis": so it is possible to read the land features as the expression of the endogenous and exogenous processes that mould earth surfaces; moreover, Landscape is the result of the interaction of natural and cultural components, and conditions the spatial-temporal development of a region. The study of the Landscape offers results useful in order to promote sustainable development, ecotourism, enhancement of natural and cultural heritage, popularization of the scientific knowledge. In Italy, a very important GIS-based tool to represent the territory is the "Carta della Natura" ("Map of Nature", presently coordinated by the ISPRA) that aims at assessing the state of the whole Italian territory, analyzing Landscape. The methodology follows a holistic approach, taking into consideration all the components of a landscape and then integrating the information. Each individual landscape, studied at different scales, shows distinctive elements: structural, which depend on physical form and specific spatial organization; functional, which depend on relationships created between biotic and abiotic elements, and dynamic, which depend on the successive evolution of the structure. The identification of the landscape units, recognized at different scales of analysis, allows an evaluation of the state of the land, referring to the dual risk/resource which characterizes the Italian country. An interesting opportunity is to discover those areas of unusual

  20. 2015 RAD-AID Conference on International Radiology for Developing Countries: The Evolving Global Radiology Landscape.

    PubMed

    Kesselman, Andrew; Soroosh, Garshasb; Mollura, Daniel J

    2016-09-01

    Radiology in low- and middle-income (developing) countries continues to make progress. Research and international outreach projects presented at the 2015 annual RAD-AID conference emphasize important global themes, including (1) recent slowing of emerging market growth that threatens to constrain the advance of radiology, (2) increasing global noncommunicable diseases (such as cancer and cardiovascular disease) needing radiology for detection and management, (3) strategic prioritization for pediatric radiology in global public health initiatives, (4) continuous expansion of global health curricula at radiology residencies and the RAD-AID Chapter Network's participating institutions, and (5) technologic innovation for recently accelerated implementation of PACS in low-resource countries. PMID:27233909

  1. The changing landscape of functional brain networks for face processing in typical development.

    PubMed

    Joseph, Jane E; Swearingen, Joshua E; Clark, Jonathan D; Benca, Chelsie E; Collins, Heather R; Corbly, Christine R; Gathers, Ann D; Bhatt, Ramesh S

    2012-11-15

    Greater expertise for faces in adults than in children may be achieved by a dynamic interplay of functional segregation and integration of brain regions throughout development. The present study examined developmental changes in face network functional connectivity in children (5-12 years) and adults (18-43 years) during face-viewing using a graph-theory approach. A face-specific developmental change involved connectivity of the right occipital face area. During childhood, this node increased in strength and within-module clustering based on positive connectivity. These changes reflect an important role of the ROFA in segregation of function during childhood. In addition, strength and diversity of connections within a module that included primary visual areas (left and right calcarine) and limbic regions (left hippocampus and right inferior orbitofrontal cortex) increased from childhood to adulthood, reflecting increased visuo-limbic integration. This integration was pronounced for faces but also emerged for natural objects. Taken together, the primary face-specific developmental changes involved segregation of a posterior visual module during childhood, possibly implicated in early stage perceptual face processing, and greater integration of visuo-limbic connections from childhood to adulthood, which may reflect processing related to development of perceptual expertise for individuation of faces and other visually homogenous categories.

  2. Understory plant communities and the functional distinction between savanna trees, forest trees, and pines

    SciTech Connect

    Veldman, Joseph W.; Mattingly, W. Brett; Brudvig, Lars A.

    2013-02-01

    Although savanna trees and forest trees are thought to represent distinct functional groups with different effects on ecosystem processes, few empirical studies have examined these effects. In particular, it remains unclear if savanna and forest trees differ in their ability to coexist with understory plants, which comprise the majority of plant diversity in most savannas. We used structural equation modeling (SEM) and data from 157 sites across three locations in the southeastern United States to understand the effects of broadleaf savanna trees, broadleaf forest trees, and pine trees on savanna understory plant communities. After accounting for underlying gradients in fire frequency and soil moisture, abundances (i.e., basal area and stem density) of forest trees and pines, but not savanna trees, were negatively correlated with the cover and density (i.e., local-scale species richness) of C4 graminoid species, a defining savanna understory functional group that is linked to ecosystem flammability. In analyses of the full understory community, abundances of trees from all functional groups were negatively correlated with species density and cover. For both the C4 and full communities, fire frequency promoted understory plants directly, and indirectly by limiting forest tree abundance. There was little indirect influence of fire on the understory mediated through savanna trees and pines, which are more fire tolerant than forest trees. We conclude that tree functional identity is an important factor that influences overstory tree relationships with savanna understory plant communities. In particular, distinct relationships between trees and C4 graminoids have implications for grass-tree coexistence and vegetation-fire feedbacks that maintain savanna environments and their associated understory plant diversity.

  3. The Impact of Fire on Energy Balance in Southern African Savanna Ecosystems: Implications of Climate Change

    NASA Astrophysics Data System (ADS)

    Dintwe, K.; Okin, G. S.; Saha, M.; Scanlon, T. M.; D'Odorico, P.; De Sales, F.; Xue, Y.

    2015-12-01

    Savannas are the most fire prone ecosystems in the world accounting for more than 75% of annual global fires. Wildfires in savannas consume large quantities of biomass releasing CO2 and aerosols while leaving ash and char residues. The residues form black-grey patches on the soil surface, and together with newly exposed bare soil patches, they play a significant role in altering surface reflectance and vegetation condition. We investigated the impact of fire on savanna albedo and vegetation greenness (from Enhanced Vegetation Index, EVI) from 2000-2014 using data from the Moderate Resolution Imaging Spectrometer (MODIS) for Africa south of the Equator. Preliminary results indicate that more mesic savannas near the Equator have the highest fire frequencies, with fire frequency generally decreasing with aridity. Immediately after fires, the average change in albedo and EVI is -5% and -10%, respectively, with the magnitude of the change increasing with aridity. The time for albedo to recover to values similar to unburned areas varied by latitude, with more mesic savannas recovering much faster (24 days vs. 65 days for dry savannas). The time for vegetation condition to recover did not vary strongly by latitude (about 65 days). The upward shortwave energy in burnt areas in mesic savannas is 53 W m-2 compared to 95 W m-2 for unburnt areas, indicating a positive forcing of about 42 W m-2 associated with mesic savanna fires locally. Approximately 7% of the (primarily savanna) land in southern Africa burns each year, suggesting an overall forcing in Africa south of the Equator of ~1-2 W m-2 associated with savanna fires. This large forcing indicates clearly the important interplay between ecosystem processes (fire) and climate (radiative forcing) in this region. With changing climate, this region is expected to become significantly drier, suggesting that the forcing due to fire might decrease in the coming decades and indicating that fire-induced albedo changes potentially

  4. Stem and leaf hydraulics of congeneric tree species from adjacent tropical savanna and forest ecosystems.

    PubMed

    Hao, Guang-You; Hoffmann, William A; Scholz, Fabian G; Bucci, Sandra J; Meinzer, Frederick C; Franco, Augusto C; Cao, Kun-Fang; Goldstein, Guillermo

    2008-03-01

    Leaf and stem functional traits related to plant water relations were studied for six congeneric species pairs, each composed of one tree species typical of savanna habitats and another typical of adjacent forest habitats, to determine whether there were intrinsic differences in plant hydraulics between these two functional types. Only individuals growing in savanna habitats were studied. Most stem traits, including wood density, the xylem water potential at 50% loss of hydraulic conductivity, sapwood area specific conductivity, and leaf area specific conductivity did not differ significantly between savanna and forest species. However, maximum leaf hydraulic conductance (K (leaf)) and leaf capacitance tended to be higher in savanna species. Predawn leaf water potential and leaf mass per area were also higher in savanna species in all congeneric pairs. Hydraulic vulnerability curves of stems and leaves indicated that leaves were more vulnerable to drought-induced cavitation than terminal branches regardless of genus. The midday K (leaf) values estimated from leaf vulnerability curves were very low implying that daily embolism repair may occur in leaves. An electric circuit analog model predicted that, compared to forest species, savanna species took longer for their leaf water potentials to drop from predawn values to values corresponding to 50% loss of K (leaf) or to the turgor loss points, suggesting that savanna species were more buffered from changes in leaf water potential. The results of this study suggest that the relative success of savanna over forest species in savanna is related in part to their ability to cope with drought, which is determined more by leaf than by stem hydraulic traits. Variation among genera accounted for a large proportion of the total variance in most traits, which indicates that, despite different selective pressures in savanna and forest habitats, phylogeny has a stronger effect than habitat in determining most hydraulic traits

  5. Understory plant communities and the functional distinction between savanna trees, forest trees, and pines.

    PubMed

    Veldman, Joseph W; Mattingly, W Brett; Brudvig, Lars A

    2013-02-01

    Although savanna trees and forest trees are thought to represent distinct functional groups with different effects on ecosystem processes, few empirical studies have examined these effects. In particular, it remains unclear if savanna and forest trees differ in their ability to coexist with understory plants, which comprise the majority of plant diversity in most savannas. We used structural equation modeling (SEM) and data from 157 sites across three locations in the southeastern United States to understand the effects of broadleaf savanna trees, broadleaf forest trees, and pine trees on savanna understory plant communities. After accounting for underlying gradients in fire frequency and soil moisture, abundances (i.e., basal area and stem density) of forest trees and pines, but not savanna trees, were negatively correlated with the cover and density (i.e., local-scale species richness) of C4 graminoid species, a defining savanna understory functional group that is linked to ecosystem flammability. In analyses of the full understory community, abundances of trees from all functional groups were negatively correlated with species density and cover. For both the C4 and full communities, fire frequency promoted understory plants directly, and indirectly by limiting forest tree abundance. There was little indirect influence of fire on the understory mediated through savanna trees and pines, which are morefire tolerant than forest trees. We conclude that tree functional identity is an important factor that influences overstory tree relationships with savanna understory plant communities. In particular, distinct relationships between trees and C4 graminoids have implications for grass-tree coexistence and vegetation-fire feedbacks that maintain savanna environments and their associated understory plant diversity.

  6. North African savanna fires and atmospheric carbon dioxide

    SciTech Connect

    Iacobellis, S.F.; Frouni, Razafimpaniolo, H.

    1994-04-20

    The effect of north African savanna fires on atmospheric CO{sub 2} is investigated using a tracer transport model. The model uses winds from operational numerical weather prediction analyses and provides CO{sub 2} concentrations as a function of space and time. After a spin-up period of several years, biomass-burning sources are added, and model experiments are run for an additional year, utilizing various estimates of CO{sub 2} sources. The various model experiments show that biomass burning in the north African savannas significantly affects CO{sub 2} concentrations in South America. The effect is more pronounced during the period from January through March, when biomass burning in South America is almost nonexistent. During this period, atmospheric CO{sub 2} concentrations in parts of South America typically may increase by 0.5 to 0.75 ppm at 970 mbar, the average pressure of the lowest model layer. These figures are above the probable uncertainty level, as model runs with biomass-burning sources estimated from independent studies using distinct data sets and techniques indicate. From May through September, when severe biomass burning occurs in South America, the effect of north African savanna fires over South America has become generally small at 970 mbar, but north of the equator it may be of the same magnitude or larger than the effect of South American fires. The CO{sub 2} concentration increase in the extreme northern and southern portions of South America, however, is mostly due to southern African fires, whose effect may be 2-3 times larger than the effect of South American fires at 970 mbar. Even in the central part of the continent, where local biomass-burning emissions are maximum, southern African fires contribute to at least 15% of the CO{sub 2} concentration increase at 970 mbar. 20 refs., 15 figs., 1 tab.

  7. Effectiveness of scat-detection dogs in determining species presence in a tropical savanna landscape.

    PubMed

    Vynne, Carly; Skalski, John R; Machado, Ricardo B; Groom, Martha J; Jácomo, Anah T A; Marinho-Filho, Jader; Ramos Neto, Mario B; Pomilla, Cristina; Silveira, Leandro; Smith, Heath; Wasser, Samuel K

    2011-02-01

    Most protected areas are too small to sustain populations of wide-ranging mammals; thus, identification and conservation of high-quality habitat for those animals outside parks is often a high priority, particularly for regions where extensive land conversion is occurring. This is the case in the vicinity of Emas National Park, a small protected area in the Brazilian Cerrado. Over the last 40 years the native vegetation surrounding the park has been converted to agriculture, but the region still supports virtually all of the animals native to the area. We determined the effectiveness of scat-detection dogs in detecting presence of five species of mammals threatened with extinction by habitat loss: maned wolf (Chrysocyon brachyurus), puma (Puma concolor), jaguar (Panthera onca), giant anteater (Myrmecophaga tridactyla), and giant armadillo (Priodontes maximus). The probability of scat detection varied among the five species and among survey quadrats of different size, but was consistent across team, season, and year. The probability of occurrence, determined from the presence of scat, in a randomly selected site within the study area ranged from 0.14 for jaguars, which occur primarily in the forested areas of the park, to 0.91 for maned wolves, the most widely distributed species in our study area. Most occurrences of giant armadillos in the park were in open grasslands, but in the agricultural matrix they tended to occur in riparian woodlands. At least one target species occurred in every survey quadrat, and giant armadillos, jaguars, and maned wolves were more likely to be present in quadrats located inside than outside the park. The effort required for detection of scats was highest for the two felids. We were able to detect the presence for each of five wide-ranging species inside and outside the park and to assign occurrence probabilities to specific survey sites. Thus, scat dogs provide an effective survey tool for rare species even when accurate detection likelihoods are required. We believe the way we used scat-detection dogs to determine the presence of species can be applied to the detection of other mammalian species in other ecosystems. PMID:21029162

  8. Effectiveness of scat-detection dogs in determining species presence in a tropical savanna landscape.

    PubMed

    Vynne, Carly; Skalski, John R; Machado, Ricardo B; Groom, Martha J; Jácomo, Anah T A; Marinho-Filho, Jader; Ramos Neto, Mario B; Pomilla, Cristina; Silveira, Leandro; Smith, Heath; Wasser, Samuel K

    2011-02-01

    Most protected areas are too small to sustain populations of wide-ranging mammals; thus, identification and conservation of high-quality habitat for those animals outside parks is often a high priority, particularly for regions where extensive land conversion is occurring. This is the case in the vicinity of Emas National Park, a small protected area in the Brazilian Cerrado. Over the last 40 years the native vegetation surrounding the park has been converted to agriculture, but the region still supports virtually all of the animals native to the area. We determined the effectiveness of scat-detection dogs in detecting presence of five species of mammals threatened with extinction by habitat loss: maned wolf (Chrysocyon brachyurus), puma (Puma concolor), jaguar (Panthera onca), giant anteater (Myrmecophaga tridactyla), and giant armadillo (Priodontes maximus). The probability of scat detection varied among the five species and among survey quadrats of different size, but was consistent across team, season, and year. The probability of occurrence, determined from the presence of scat, in a randomly selected site within the study area ranged from 0.14 for jaguars, which occur primarily in the forested areas of the park, to 0.91 for maned wolves, the most widely distributed species in our study area. Most occurrences of giant armadillos in the park were in open grasslands, but in the agricultural matrix they tended to occur in riparian woodlands. At least one target species occurred in every survey quadrat, and giant armadillos, jaguars, and maned wolves were more likely to be present in quadrats located inside than outside the park. The effort required for detection of scats was highest for the two felids. We were able to detect the presence for each of five wide-ranging species inside and outside the park and to assign occurrence probabilities to specific survey sites. Thus, scat dogs provide an effective survey tool for rare species even when accurate detection likelihoods are required. We believe the way we used scat-detection dogs to determine the presence of species can be applied to the detection of other mammalian species in other ecosystems.

  9. Fires in tropical savanna ecosystems -- The need for mitigation?

    SciTech Connect

    Ward, D.E.; Shea, R.; Hao, W.M.

    1994-12-31

    Fires in savanna ecosystems are usually considered to be ``natural`` in that the ecosystems where fire is present generally have evolved in the presence of fire. In the past several decades, with large increases in population in most of the tropical countries, there has been an accelerated demand for fuel wood, charcoal, building materials, and agriculture. The overall effect has been to reduce the above-ground biomass and to cycle the carbon more frequently. The authors discuss the mitigation strategies for reducing the release of carbon from charcoal production and shifting cultivation.

  10. Life on Guam: Savanna, Old Fields, Roadsides.

    ERIC Educational Resources Information Center

    Falanruw, Margie Cushing

    This unit is part of a series of materials produced by a project to develop locally applicable class, lab, and field materials in ecology and social studies for Guam junior and senior high schools. While the materials were developed for Guam, they can be adapted to other localities. The unit stresses the uniqueness of natural Guam, especially the…

  11. Age and dynamics of the Namib Sand Sea: A review of chronological evidence and possible landscape development models

    NASA Astrophysics Data System (ADS)

    Stone, A. E. C.

    2013-06-01

    The Namib Sand Sea constitutes a major physiographic feature of the Namib Desert on the west of Namibia, covering a 50-160 km wide region of the coast between Lüderitz and Walvis Bay. It is widely considered to be one of the oldest desert regions, with a Tertiary-aged fossil desert underlying the modern sand sea. The sand sea has been well studied, benefiting from the presence of the Gobabeb Training and Research Centre during the past 50 years. Whilst much is understood about its sediments and geomorphology, it is only recently that new chronological information, using cosmogenic-nuclide burial dating and optically stimulated luminescence dating have offered new insights, and this calls for an updated review of the age and landscape development of the sand sea. This assessment of the geomorphological and Quaternary dynamics of the region is complemented by developments in the description and analysis of sediment composition. New age control from cosmogenic dating indicates that the sand sea is in excess of a million years old. Initial data from luminescence dating yields depositional ages for dune sediments from three broad areas of the sand sea that include MIS 5, later in the Pleistocene around the Last Glacial Maximum and the Holocene, although it is not expected that these will be the only, or discrete age groupings. Detailed dating and application of ground penetrating radar in the far northern reaches reveals extensive dune migration and deposition during the Holocene. It is important to stress that the upper limit of luminescence dating here is about ˜200 ka (depending on the environmental dose rate of the site) and that migration and reworking of dunes resets the luminescence signal (so what is recorded is(are) the last phase(s) of preserved sediment accumulation). Whilst there are three potential sources of material for the Namib Sand Sea (reworked Tsondab Sandstone (TSS), material from the Great Escarpment derived by rivers and water and wind

  12. Isolated Ficus trees deliver dual conservation and development benefits in a rural landscape.

    PubMed

    Cottee-Jones, H Eden W; Bajpai, Omesh; Chaudhary, Lal B; Whittaker, Robert J

    2015-11-01

    Many of the world's rural populations are dependent on the local provision of economically and medicinally important plant resources. However, increasing land-use intensity is depleting these resources, reducing human welfare, and thereby constraining development. Here we investigate a low cost strategy to manage the availability of valuable plant resources, facilitated by the use of isolated Ficus trees as restoration nuclei. We surveyed the plants growing under 207 isolated trees in Assam, India, and categorized them according to their local human-uses. We found that Ficus trees were associated with double the density of important high-grade timber, firewood, human food, livestock fodder, and medicinal plants compared to non-Ficus trees. Management practices were also important in determining the density of valuable plants, with grazing pressure and land-use intensity significantly affecting densities in most categories. Community management practices that conserve isolated Ficus trees, and restrict livestock grazing and high-intensity land-use in their vicinity, can promote plant growth and the provision of important local resources.

  13. Predicting Stand-Level Fire Behavior From Forest Community Data in Former Prairie and Savanna

    NASA Astrophysics Data System (ADS)

    Yospin, G. I.; Bridgham, S. D.; Kertis, J.; Johnson, B. R.

    2009-05-01

    As development pressures continue to expand the extent of the wildland-urban interface (WUI), the ability to predict fire regimes there becomes increasingly important. Such predictions will be particularly valuable to land managers who seek to reduce wildfire risk and to restore imperiled ecosystems within the WUI. Our study focused on remnant and former upland prairie and oak savanna ecosystems in the southern Willamette Valley, Oregon, which were widespread prior to Euro-American settlement but now occupy less than 2% of their historic range. Prairie and savanna grasslands provide habitat for several endangered species, as well as important ecosystem services, such as the regulation of fire regimes. We sampled over 250 plots from seven sites that were grasslands with few to no trees circa 1850 but now have markedly different communities, ranging from prairie to dense forest. We collected data on community composition, topography and fuel loadings. With the BehavePlus fire model, we calculated surface and crown fire parameters. We built two classification and regression trees (CARTs) that used plant community data to group plots on the basis of their surface-fire and crown-fire behavior, respectively. Fuel loads differed significantly by community type, although trends in fuel loadings were neither monotonic across communities nor intuitive. Fuel characteristics were extremely sensitive to topography, and may result from successional history and the presence of exotic invasive species. Though the CARTs were statistically significant, they generally had poor predictive power, which is indicative of the amount of variability inherent in wildland fire. There was greater variability in fire behavior for more intense fires, indicating that land managers can improve the precision of their predictions by managing for less intense fire regimes. The CARTs suggested that surface fires differed among nine different community types and crown fire behavior differed among five

  14. Green Is the New Black: The Need for a New Currency That Values Water Resources in Rapidly Developing Landscapes

    NASA Astrophysics Data System (ADS)

    Creed, I. F.; Webster, K. L.; Kreutzweiser, D. P.; Beall, F.

    2014-12-01

    Canada's boreal forest supports many aquatic ecosystem services (AES) due to the intimate linkage between aquatic systems and their surrounding terrestrial watersheds in forested landscapes. There is an increasing risk to AES because natural development activities (forest management, mining, energy) have resulted in disruptions that deteriorate aquatic ecosystems at local (10s of km2) to regional (100s of km2) scales. These activities are intensifying and expanding, placing at risk the healthy aquatic ecosystems that provide AES and may threaten the continued development of the energy, forest, and mining sectors. Remarkably, we know little about the consequences of these activities on AES. The idea that AES should be explicitly integrated into modern natural resource management regulations is gaining broad acceptance. A major need is the ability to measure cumulative effects and determine thresholds (the points where aquatic ecosystems and their services cannot recover to a desired state within a reasonable time frame) in these cumulative effects. However, there is no single conceptual approach to assessing cumulative effects that is widely accepted by both scientists and managers. We present an integrated science-policy framework that enables the integration of AES into forest management risk assessment and prevention/mitigation strategies. We use this framework to explore the risk of further deterioration of AES by (1) setting risk criteria; (2) using emerging technologies to map process-based indicators representing causes and consequences of risk events to the deterioration of AES; (3) assessing existing prevention and mitigation policies in place to avoid risk events; and (4) identifying priorities for policy change needed to reduce risk event. Ultimately, the success of this framework requires that higher value be placed on AES, and in turn to improve the science and management of the boreal forest.

  15. Restoring grassland savannas from degraded pinyon-juniper woodlands: effects of mechanical overstory reduction and slash treatment alternatives.

    PubMed

    Brockway, Dale G; Gatewood, Richard G; Paris, Randi B

    2002-02-01

    Although the distribution and structure of pinyon-juiper woodlands in the southwestern United States are thought to be the result of historic fluctuations in regional climatic conditions, more recent increases in the areal extent, tree density, soil erosion rates and loss of understory plant diversity are attributed to heavy grazing by domestic livestock and interruption of the natural fire regime. Prior to 1850, many areas currently occupied by high-density pinyon-juniper woodlands, with their degraded soils and depauperate understories, were very likely savannas dominated by native grasses and forbs and containing sparse tree cover scattered across the landscape. The purpose of this study was to evaluate the effectiveness of mechanical overstory reduction and three slash treatment alternatives (removal, clustering and scattering) followed by prescribed fire as techniques for restoring grassland savannas from degraded woodlands. Plant cover, diversity, biomass and nutrient status, litter cover and soil chemistry and erosion rates were measured prior to and for two years following experimental treatment in a degraded pinyon-juniper woodland in central New Mexico. Treatment resulted in a significant increase in the cover of native grasses and, to a lesser degree, forbs and shrubs. Plant species richness and diversity increased most on sites where slash was either completely removed or scattered to serve as a mulch. Although no changes in soil chemistry or plant nutrient status were observed, understory biomass increased over 200% for all harvest treatments and was significantly greater than controls. While treatment increased litter cover and decreased soil exposure, this improvement did not significantly affect soil loss rates. Even though all slash treatment alternatives increased the cover and biomass of native grasses, scattering slash across the site to serve as a mulch appears most beneficial to improving plant species diversity and conserving site resources

  16. Fitness Landscapes of Functional RNAs.

    PubMed

    Kun, Ádám; Szathmáry, Eörs

    2015-08-21

    The notion of fitness landscapes, a map between genotype and fitness, was proposed more than 80 years ago. For most of this time data was only available for a few alleles, and thus we had only a restricted view of the whole fitness landscape. Recently, advances in genetics and molecular biology allow a more detailed view of them. Here we review experimental and theoretical studies of fitness landscapes of functional RNAs, especially aptamers and ribozymes. We find that RNA structures can be divided into critical structures, connecting structures, neutral structures and forbidden structures. Such characterisation, coupled with theoretical sequence-to-structure predictions, allows us to construct the whole fitness landscape. Fitness landscapes then can be used to study evolution, and in our case the development of the RNA world.

  17. Fitness Landscapes of Functional RNAs

    PubMed Central

    Kun, Ádám; Szathmáry, Eörs

    2015-01-01

    The notion of fitness landscapes, a map between genotype and fitness, was proposed more than 80 years ago. For most of this time data was only available for a few alleles, and thus we had only a restricted view of the whole fitness landscape. Recently, advances in genetics and molecular biology allow a more detailed view of them. Here we review experimental and theoretical studies of fitness landscapes of functional RNAs, especially aptamers and ribozymes. We find that RNA structures can be divided into critical structures, connecting structures, neutral structures and forbidden structures. Such characterisation, coupled with theoretical sequence-to-structure predictions, allows us to construct the whole fitness landscape. Fitness landscapes then can be used to study evolution, and in our case the development of the RNA world. PMID:26308059

  18. Ant plant herbivore interactions in the neotropical cerrado savanna

    NASA Astrophysics Data System (ADS)

    Oliveira, Paulo S.; Freitas, André V. L.

    2004-12-01

    The Brazilian cerrado savanna covers nearly 2 million km2 and has a high incidence on foliage of various liquid food sources such as extrafloral nectar and insect exudates. These liquid rewards generate intense ant activity on cerrado foliage, making ant plant herbivore interactions especially prevalent in this biome. We present data on the distribution and abundance of extrafloral nectaries in the woody flora of cerrado communities and in the flora of other habitats worldwide, and stress the relevance of liquid food sources (including hemipteran honeydew) for the ant fauna. Consumption by ants of plant and insect exudates significantly affects the activity of the associated herbivores of cerrado plant species, with varying impacts on the reproductive output of the plants. Experiments with an ant plant butterfly system unequivocally demonstrate that the behavior of both immature and adult lepidopterans is closely related to the use of a risky host plant, where intensive visitation by ants can have a severe impact on caterpillar survival. We discuss recent evidence suggesting that the occurrence of liquid rewards on leaves plays a key role in mediating the foraging ecology of foliage-dwelling ants, and that facultative ant plant mutualisms are important in structuring the community of canopy arthropods. Ant-mediated effects on cerrado herbivore communities can be revealed by experiments performed on wide spatial scales, including many environmental factors such as soil fertility and vegetation structure. We also present some research questions that could be rewarding to investigate in this major neotropical savanna.

  19. Source compositions of trace gases released during African savanna fires

    NASA Astrophysics Data System (ADS)

    Cofer, Wesley R.; Levine, Joel S.; Winstead, Edward L.; Cahoon, Donald R.; Sebacher, Daniel I.; Pinto, Joseph P.; Stocks, Brian J.

    1996-10-01

    Measurements of biomass burn-produced trace gases were made using low-altitude helicopter penetrations of smoke plumes above burning African savanna during the Southern African Fire-Atmosphere Research Initiative (SAFARI-92). Smoke from two large prescribed fires conducted in the Kruger National Park, South Africa, on September 18 and 24, 1992, was sampled at altitudes ranging from 20 to 100 m above ground level during flaming and smoldering phases of combustion. Carbon dioxide (CO2) normalized emission ratios (dX/dCO2 (vol/vol), where X denotes a trace gas) for carbon monoxide (CO), hydrogen (H2), methane (CH4), total nonmethane hydrocarbons (TNMHC), and nitrous oxide (N2O) were determined. The emission ratios were used in conjunction with fuel consumption estimates to calculate emission factors (grams of product per gram of fuel) for these gases. Emission factors for CO2, CO, CH4, and N2O of 1.61, 0.055, 0.003, and 1.6 × 10-4 g/g fuel, respectively, were determined. The fires advanced rapidly through the savanna (primarily grass) fuels with minimal amounts of smoldering combustion. The relatively low emission ratios determined for these fires indicated excellent combustion efficiency. About 93% of the carbon released into the atmosphere as a result of these fires was in the form of CO2.

  20. Effect of wildfires on surface reflectance from a savanna ecosystem

    NASA Astrophysics Data System (ADS)

    Poudyal, R.; Gatebe, C. K.; Ichoku, C. M.; Varnai, T.

    2015-12-01

    During an airborne field campaign in South Africa in 2005, NASA's Cloud Absorption Radiometer (CAR) flew aboard South Africa Weather Service, Aerocommander 690A and measured surface bidirectional reflectance-distribution function (BRDF) over savanna comprised mostly of grasses and a few scattered trees. Savannas cover half the surface of Africa, large areas of Australia, South America, and India. . The region that was studied is located in Kruger National Park in northeastern South Africa, which was heavily affected by the wildfires. The CAR measured surface reflectance along its flight path covering both burned and unburned areas. . In this study, we compared surface reflectance between burnt and un-burnt areas at various wavelengths (340nm, 380nm, 472nm, 682nm, 870nm, 1036nm, 1219nm, 1273nm, and 2205nm) at satellite sub-pixel scales. We found a relative burnt surface reflectance decrease of between 8 and 65% due to fires. These results not only serve to highlight the importance of biomass burning and effects on the energy budgets, but also the need to determine the effects of albedo changes due to fires on soil moisture budget, evapotranspiration, infiltration, and runoff, all of which govern the land-surface component of the water cycle.

  1. Modelling fire frequency in a Cerrado savanna protected area.

    PubMed

    Pereira Júnior, Alfredo C; Oliveira, Sofia L J; Pereira, José M C; Turkman, Maria Antónia Amaral

    2014-01-01

    Covering almost a quarter of Brazil, the Cerrado is the world's most biologically rich tropical savanna. Fire is an integral part of the Cerrado but current land use and agricultural practices have been changing fire regimes, with undesirable consequences for the preservation of biodiversity. In this study, fire frequency and fire return intervals were modelled over a 12-year time series (1997-2008) for the Jalapão State Park, a protected area in the north of the Cerrado, based on burned area maps derived from Landsat imagery. Burned areas were classified using object based image analysis. Fire data were modelled with the discrete lognormal model and the estimated parameters were used to calculate fire interval, fire survival and hazard of burning distributions, for seven major land cover types. Over the study period, an area equivalent to four times the size of Jalapão State Park burned and the mean annual area burned was 34%. Median fire intervals were generally short, ranging from three to six years. Shrub savannas had the shortest fire intervals, and dense woodlands the longest. Because fires in the Cerrado are strongly responsive to fuel age in the first three to four years following a fire, early dry season patch mosaic burning may be used to reduce the extent of area burned and the severity of fire effects. PMID:25054540

  2. ReRouting biomedical innovation: observations from a mapping of the alternative research and development (R&D) landscape.

    PubMed

    Greenberg, Alexandra; Kiddell-Monroe, Rachel

    2016-01-01

    In recent years, the world has witnessed the tragic outcomes of multiple global health crises. From Ebola to high prices to antibiotic resistance, these events highlight the fundamental constraints of the current biomedical research and development (R&D) system in responding to patient needs globally.To mitigate this lack of responsiveness, over 100 self-identified "alternative" R&D initiatives, have emerged in the past 15 years. To begin to make sense of this panoply of initiatives working to overcome the constraints of the current system, UAEM began an extensive, though not comprehensive, mapping of the alternative biomedical R&D landscape. We developed a two phase approach: (1) an investigation, via the RE:Route Mapping, of both existing and proposed initiatives that claim to offer an alternative approach to R&D, and (2) evaluation of those initiatives to determine which are in fact achieving increased access to and innovation in medicines. Through phase 1, the RE:Route Mapping, we examined 81 initiatives that claim to redress the inequity perpetuated by the current system via one of five commonly recognized mechanisms necessary for truly alternative R&D.Preliminary analysis of phase 1 provides the following conclusions: 1. No initiative presents a completely alternative model of biomedical R&D. 2. The majority of initiatives focus on developing incentives for drug discovery. 3. The majority of initiatives focus on rare diseases or diseases of the poor and marginalized. 4. There is an increasing emphasis on the use of push, pull, pool, collaboration and open mechanisms alongside the concept of delinkage in alternative R&D. 5. There is a trend towards public funding and launching of initiatives by the Global South. Given the RE:Route Mapping's inevitable limitations and the assumptions made in its methodology, it is not intended to be the final word on a constantly evolving and complex field; however, its findings are significant. The Mapping's value lies in its

  3. ReRouting biomedical innovation: observations from a mapping of the alternative research and development (R&D) landscape.

    PubMed

    Greenberg, Alexandra; Kiddell-Monroe, Rachel

    2016-09-14

    In recent years, the world has witnessed the tragic outcomes of multiple global health crises. From Ebola to high prices to antibiotic resistance, these events highlight the fundamental constraints of the current biomedical research and development (R&D) system in responding to patient needs globally.To mitigate this lack of responsiveness, over 100 self-identified "alternative" R&D initiatives, have emerged in the past 15 years. To begin to make sense of this panoply of initiatives working to overcome the constraints of the current system, UAEM began an extensive, though not comprehensive, mapping of the alternative biomedical R&D landscape. We developed a two phase approach: (1) an investigation, via the RE:Route Mapping, of both existing and proposed initiatives that claim to offer an alternative approach to R&D, and (2) evaluation of those initiatives to determine which are in fact achieving increased access to and innovation in medicines. Through phase 1, the RE:Route Mapping, we examined 81 initiatives that claim to redress the inequity perpetuated by the current system via one of five commonly recognized mechanisms necessary for truly alternative R&D.Preliminary analysis of phase 1 provides the following conclusions: 1. No initiative presents a completely alternative model of biomedical R&D. 2. The majority of initiatives focus on developing incentives for drug discovery. 3. The majority of initiatives focus on rare diseases or diseases of the poor and marginalized. 4. There is an increasing emphasis on the use of push, pull, pool, collaboration and open mechanisms alongside the concept of delinkage in alternative R&D. 5. There is a trend towards public funding and launching of initiatives by the Global South. Given the RE:Route Mapping's inevitable limitations and the assumptions made in its methodology, it is not intended to be the final word on a constantly evolving and complex field; however, its findings are significant. The Mapping's value lies in its

  4. Vegetation-climate feedbacks in the conversion of tropical savanna to grassland

    SciTech Connect

    Hoffmann, W.A.; Jackson, R.B.

    2000-05-01

    Tropical savannas have been heavily impacted by human activity, with large expanses transformed from a mixture of trees and grasses to open grassland and agriculture. The National Center for Atmospheric Research (NCAR) CCM3 general circulation model, coupled with the NCAR Land Surface Model, was used to simulate the effects of this conversion on regional climate. Conversion of savanna to grassland reduced precipitation by approximately 10% in four of the five savanna regions under study; only the northern African savannas showed no significant decline. Associated with this decline was an increase in the frequency of dry periods within the wet season, a change that could be particularly damaging to shallow-rooted crops. The overall decline in precipitation is almost equally attributable to changes in albedo and roughness length. Conversion to grassland increased mean surface air temperature of all the regions by 0.5 C, primarily because of reductions in surface roughness length. Rooting depth, which decreases dramatically with the conversion of savanna to grassland, contributed little to the overall effect of savanna conversion, but deeper rooting had a small positive effect on latent heat flux with a corresponding reduction in sensible heat flux. The authors propose that the interdependence of climate and vegetation in these regions is manifested as a positive feedback loop in which anthropogenic impacts on savanna vegetation are exacerbated by declines in precipitation.

  5. Climate change and long-term fire management impacts on Australian savannas.

    PubMed

    Scheiter, Simon; Higgins, Steven I; Beringer, Jason; Hutley, Lindsay B

    2015-02-01

    Tropical savannas cover a large proportion of the Earth's land surface and many people are dependent on the ecosystem services that savannas supply. Their sustainable management is crucial. Owing to the complexity of savanna vegetation dynamics, climate change and land use impacts on savannas are highly uncertain. We used a dynamic vegetation model, the adaptive dynamic global vegetation model (aDGVM), to project how climate change and fire management might influence future vegetation in northern Australian savannas. Under future climate conditions, vegetation can store more carbon than under ambient conditions. Changes in rainfall seasonality influence future carbon storage but do not turn vegetation into a carbon source, suggesting that CO₂ fertilization is the main driver of vegetation change. The application of prescribed fires with varying return intervals and burning season influences vegetation and fire impacts. Carbon sequestration is maximized with early dry season fires and long fire return intervals, while grass productivity is maximized with late dry season fires and intermediate fire return intervals. The study has implications for management policy across Australian savannas because it identifies how fire management strategies may influence grazing yield, carbon sequestration and greenhouse gas emissions. This knowledge is crucial to maintaining important ecosystem services of Australian savannas.

  6. Drivers of Recent Trends in African Landscape Fires

    NASA Astrophysics Data System (ADS)

    Andela, N.; van der Werf, G.

    2014-12-01

    Landscape fires play an important role in savannah ecosystem dynamics and are an important source of emissions of (greenhouse) gases and aerosols. Within the Monitoring Atmospheric Composition and Climate (MACC) project these fires are monitored using MODIS satellite data which now provides more than a decade of continuous observations. Africa is nowadays responsible for about 70% of global burned area and about 50% of fire carbon emissions, affecting regional air quality and global atmospheric composition. Although it has been reported that fire activity varies according to climatic and anthropogenic influences, much remains unclear about the drivers of the spatial distribution of fire activity over the African continent and its temporal dynamics. Resolving the drivers of this spatiotemporal variability is crucial to understand the future role of fire on the African continent. We developed a model to account for variations in fire activity due to climate, and investigated the role of sea surface temperatures on rainfall patterns and thus fire dynamics. Spatial variation and trends in cropland extent were used to improve understanding of underlying trends caused by socio-economic changes. Over 2001-2012, satellite observations indicate strong but opposing trends in the African hemispheres. Changes in precipitation, driven by the El Niño/Southern Oscillation (ENSO), which changed from El Niño to la Niña dominance over the study period, contributed substantially to the upward trend over southern Africa. This shift also contributed to the downward trend in northern Africa, but here rapid demographic and socio-economic developments contributed equally. Given the economic perspective of Africa and the oscillative nature of ENSO, future African savannah burned area will likely decline. Using MACC and GFED emissions estimates we expect that in the long term this decrease may be so substantial that forests may take over savannas as the main source of global fire

  7. Relating Landscape Development Intensity to Coral Reef Condition in the Watersheds of St. Croix, U.S. Virgin Islands

    EPA Science Inventory

    Diagnosing the degree to which local landscape activities impact coral reef ecosystems and their ecological services is critically important to coastal and watershed decision-makers. We report, for the first time, a study that relates coral reef condition metrics to metrics of h...

  8. [Anatomical and nutrient features of plant leaves in Yuanjiang savanna valley].

    PubMed

    Song, Fuqiang; Cao, Kunfang

    2005-01-01

    Due to rain shadow effect, the valleys in southwestern China mountainous areas have hot and dry climate, and savanna or semi-savanna vegetations occur on the slopes of these valleys. Yuanjiang dry-hot valley is such a valley, which has a distinct dry season of about six months from November to next April. This paper studied the anatomical and nutrient features of the leaves of twenty plant species, including those on upland soils and hilly slopes. The results showed that compared with the species on upland soil and the rain forest, the leaves of the plants from savanna showed more xeromorphic features, such as thicker leaf thickness, greater leaf mass per area (LMA), smaller ratios of spongy/palisade tissues (S:P) and higher stomatal density (SD), which mainly came from the more severe drought in Yuanjiang savanna valley. Seven plant species in the savanna valley showed a shortage of nutrients in their leaves, and the leaf nutrient content was in order of 1.3% > Ca > N > K > 1% > Mg > P > S. Savanna had lower leaf mineral element concentrations than rain forest, but higher than other dry forests, including Asian heath forest and Bana forest. The differences in leaf nutrient concentrations between Yuanjiang valley savanna and other dry forests were mainly ascribed to the difference of soil nutrient contents, while those between valley savanna and rainforest were largely determined by the different plant biology. It could be concluded that the leaves of plant species in Yuanjiang savanna valley not only had obvious xeromorphic features, but also were deficit in nutrients. PMID:15852953

  9. [Anatomical and nutrient features of plant leaves in Yuanjiang savanna valley].

    PubMed

    Song, Fuqiang; Cao, Kunfang

    2005-01-01

    Due to rain shadow effect, the valleys in southwestern China mountainous areas have hot and dry climate, and savanna or semi-savanna vegetations occur on the slopes of these valleys. Yuanjiang dry-hot valley is such a valley, which has a distinct dry season of about six months from November to next April. This paper studied the anatomical and nutrient features of the leaves of twenty plant species, including those on upland soils and hilly slopes. The results showed that compared with the species on upland soil and the rain forest, the leaves of the plants from savanna showed more xeromorphic features, such as thicker leaf thickness, greater leaf mass per area (LMA), smaller ratios of spongy/palisade tissues (S:P) and higher stomatal density (SD), which mainly came from the more severe drought in Yuanjiang savanna valley. Seven plant species in the savanna valley showed a shortage of nutrients in their leaves, and the leaf nutrient content was in order of 1.3% > Ca > N > K > 1% > Mg > P > S. Savanna had lower leaf mineral element concentrations than rain forest, but higher than other dry forests, including Asian heath forest and Bana forest. The differences in leaf nutrient concentrations between Yuanjiang valley savanna and other dry forests were mainly ascribed to the difference of soil nutrient contents, while those between valley savanna and rainforest were largely determined by the different plant biology. It could be concluded that the leaves of plant species in Yuanjiang savanna valley not only had obvious xeromorphic features, but also were deficit in nutrients.

  10. Development and assessment of a landscape-scale ecological threat index for the Lower Colorado River Basin

    USGS Publications Warehouse

    Paukert, Craig P.; Pitts, K.L.; Whittier, Joanna B.; Olden, Julian D.

    2011-01-01

    Anthropogenic disturbances impact freshwater biota but are rarely incorporated into conservation planning due to the difficulties in quantifying threats. There is currently no widely accepted method to quantify disturbances, and determining how to measure threats to upstream catchments using disturbance metrics can be time consuming and subjective. We compared four watershed-scale ecological threat indices for the Lower Colorado River Basin (LCRB) using landscape-level threats of land use (e.g., agricultural and urban lands), waterway development and diversions (e.g., number of canals, dams), and human development (e.g., road and railroads density, pollution sites). The LCRB is an ideal region to assess ecological threat indices because of the increasing need for conservation to ensure the persistence of native fishes in highly altered habitat. Each threat was measured for severity (i.e., level of influence on the upstream watershed) and frequency throughout each watershed; both severity and frequency were measured using two different methods. Severity values were based either on peer-reviewed literature and weighted in accordance to their published ecological impact, or assumed equal severity across stressors. Threat frequency was calculated according to either the presence/absence of each stressor, or on the relative density of each stressor in the watershed. Each measure of severity was combined with a measure of frequency, creating four ecological threat indices, and transformed to a 0–100 scale. Threat indices were highly correlated (slopes of 0.94–1.63; R2 of 0.82–0.98), and were highest for watersheds close to urban centers, including Phoenix, Tucson, and Flagstaff, Arizona, and Las Vegas, Nevada. Road crossings and density appeared to be the most influential stressors in the index, but the removal of any individual stressor only changed the index by <5.1 units. Our results indicate that a simpler index with less subjectivity (i.e., presence/absence of

  11. Grassland structural heterogeneity in a savanna is driven more by productivity differences than by consumption differences between lawn and bunch grasses.

    PubMed

    Veldhuis, Michiel P; Fakkert, Heleen F; Berg, Matty P; Olff, Han

    2016-11-01

    Savanna grasslands are characterized by high spatial heterogeneity in vegetation structure, aboveground biomass and nutritional quality, with high quality short-grass grazing lawns forming mosaics with patches of tall bunch grasses of lower quality. This heterogeneity can arise because of local differences in consumption, because of differences in productivity, or because both processes enforce each other (more production and consumption). However, the relative importance of both processes in maintaining mosaics of lawn and bunch grassland types has not been measured. Also their interplay been not been assessed across landscape gradients. In a South African savanna, we, therefore, measured the seasonal changes in primary production, nutritional quality and herbivore consumption (amount and percentage) of grazing lawns and adjacent bunch grass patches across a rainfall gradient. We found both higher amounts of primary production and, to a smaller extent, consumption for bunch grass patches. In addition, for bunch grasses primary production increased towards higher rainfall while foliar nitrogen concentrations decreased. Foliar nitrogen concentrations of lawn grasses decreased much less with increasing rainfall. Consequently, large herbivores targeted the biomass produced on grazing lawns with on average 75 % of the produced biomass consumed. We conclude that heterogeneity in vegetation structure in this savanna ecosystem is better explained by small-scale differences in productivity between lawn and bunch grass vegetation types than by local differences in consumption rates. Nevertheless, the high nutritional quality of grazing lawns is highly attractive and, therefore, important for the maintenance of the heterogeneity in species composition (i.e. grazing lawn maintenance). PMID:27522607

  12. How Plant Functional-Type, Weather, Seasonal Drought, and Soil Physical Properties Alter Water and Energy Fluxes of an Oak-Grass Savanna and an Annual Grassland

    NASA Astrophysics Data System (ADS)

    Baldocchi, D.; Xu, L.

    2003-12-01

    Savannas and open grasslands often co-exist in semi-arid regions. How these contrasting landscapes affect the exchanges of energy remain to be quantified. Here we examine how a number of abiotic, biotic and edaphic factors modulate water and energy flux densities over an oak/grass savanna and an annual grassland that coexist in the same climate but on soils with different hydraulic properties. The net radiation balance was greater over the oak woodland than the grassland despite the fact that both canopies received similar sums of incoming short and long wave radiation. The lower albedo and lower surface temperature of the transpiring woodland caused it to intercept and retain more long and shortwave energy during the dry period. The observed differences in net energy exchange had profound impacts on canopy evaporation and sensible heat exchange. The woodland evaporated about 380 mm per year and the grassland evaporated about 300 mm per year. Differences in the water holding characteristics of the soils at the two sites account for this difference in evaporation, and provide a partial explanation why the vegetation differs at the two sites. The response of evaporation to diminishing soil moisture was quantified using information on volumetric water content, soil water potential of the root zone and predawn water potential. When soil moisture was ample, after recharging winter rains, values of latent heat flux density, normalized by the equilibrium evaporation rate, were greater for the grassland than for the oak savanna. The grassland died and quit evaporating when the water content of the soil dropped below the permanent wilting point (-1.5 MPa). The oak trees, on the other hand, were able to transpire, at low rates, under very dry soil conditions (soil water potentials down to -4.0 MPa). The trees were able to endure such low water potentials and maintain basal levels of metabolism because a few exploratory roots tapped deep water sources during the dry season

  13. Inter- and intrahabitat dietary variability of chacma baboons (Papio ursinus) in South African savannas based on fecal delta13C, delta15N, and %N.

    PubMed

    Codron, Daryl; Lee-Thorp, Julia A; Sponheimer, Matt; de Ruiter, Darryl; Codron, Jacqueline

    2006-02-01

    Baboons are dietary generalists, consuming a wide range of food items in varying proportions. It is thus difficult to quantify and explain the dietary behavior of these primates. We present stable carbon (delta(13)C) and nitrogen (delta(15)N) isotopic data, and percentage nitrogen (%N), of feces from chacma baboons (Papio ursinus) living in two savanna environments of South Africa: the mountainous Waterberg region and the low-lying Kruger National Park. Baboons living in the more homogeneous landscapes of the Waterberg consume a more isotopically heterogeneous diet than their counterparts living in Kruger Park. Grasses and other C(4)-based foods comprise between approximately 10-20% (on average) of the bulk diet of Kruger Park baboons. Carbon isotopic data from the Waterberg suggest diets of approximately 30-50% grass, which is higher than generally reported for baboons across the African savanna. Based on observations of succulent-feeding, we propose that baboons in the Waterberg consume a mix of C(4) grasses and CAM-photosynthesizing succulents in combined proportions varying between approximately 5-75% (average, approximately 35%). Fecal delta(15)N of baboons is lower than that of sympatric ungulates, which may be due to a combination of low levels of faunivory, foraging on subterranean plant parts, or the use of human foods in the case of Kruger Park populations. Fecal N levels in baboons are consistently higher than those of sympatric ungulate herbivores, indicating that baboons consume a greater proportion of protein-rich foods than do other savanna mammals. These data suggest that chacma baboons adapt their dietary behavior so as to maximize protein intake, regardless of their environment.

  14. Stable isotopes in ecosystem science: structure, function and dynamics of a subtropical Savanna.

    PubMed

    Boutton, T W; Archer, S R; Midwood, A J

    1999-01-01

    Stable isotopes are often utilized as intrinsic tracers to study the effects of human land uses on the structural and functional characteristics of ecosystems. Here, we illustrate how stable isotopes of H, C, and O have been utilized to document changes in ecosystem structure and function using a case study from a subtropical savanna ecosystem. Specifically, we demonstrate that: (1) delta 13C values of soil organic carbon record a vegetation change in this ecosystem from C4 grassland to C3 woodland during the past 40-120 years, and (2) delta 2H and delta 18O of plant and soil water reveal changes in ecosystem hydrology that accompanied this grassland-to-woodland transition. In the Rio Grande Plains of North America, delta 13C values of plants and soils indicate that areas now dominated by C3 subtropical thorn woodland were once C4 grasslands. delta 13C values of current organic matter inputs from wooded landscape elements in this region are characteristic of C3 plants (-28 to -25/1000), while those of the associated soil organic carbon are higher and range from -20 to -15/1000. Approximately 50-90% of soil carbon beneath the present C3 woodlands is derived from C4 grasses. A strong memory of the C4 grasslands that once dominated this region is retained by delta 13C values of organic carbon associated with fine and coarse clay fractions. When delta 13C values are evaluated in conjunction with 14C measurements of that same soil carbon, it appears that grassland-to-woodland conversion occurred largely within the past 40-120 years, coincident with the intensification of livestock grazing and reductions in fire frequency. These conclusions substantiate those based on demographic characteristics of the dominant tree species, historical aerial photography, and accounts of early settlers and explores. Concurrent changes in soil delta 13C values and organic carbon content over the past 90 years also indicate that wooded landscape elements are behaving as sinks for

  15. Stable isotopes in ecosystem science: structure, function and dynamics of a subtropical Savanna.

    PubMed

    Boutton, T W; Archer, S R; Midwood, A J

    1999-01-01

    Stable isotopes are often utilized as intrinsic tracers to study the effects of human land uses on the structural and functional characteristics of ecosystems. Here, we illustrate how stable isotopes of H, C, and O have been utilized to document changes in ecosystem structure and function using a case study from a subtropical savanna ecosystem. Specifically, we demonstrate that: (1) delta 13C values of soil organic carbon record a vegetation change in this ecosystem from C4 grassland to C3 woodland during the past 40-120 years, and (2) delta 2H and delta 18O of plant and soil water reveal changes in ecosystem hydrology that accompanied this grassland-to-woodland transition. In the Rio Grande Plains of North America, delta 13C values of plants and soils indicate that areas now dominated by C3 subtropical thorn woodland were once C4 grasslands. delta 13C values of current organic matter inputs from wooded landscape elements in this region are characteristic of C3 plants (-28 to -25/1000), while those of the associated soil organic carbon are higher and range from -20 to -15/1000. Approximately 50-90% of soil carbon beneath the present C3 woodlands is derived from C4 grasses. A strong memory of the C4 grasslands that once dominated this region is retained by delta 13C values of organic carbon associated with fine and coarse clay fractions. When delta 13C values are evaluated in conjunction with 14C measurements of that same soil carbon, it appears that grassland-to-woodland conversion occurred largely within the past 40-120 years, coincident with the intensification of livestock grazing and reductions in fire frequency. These conclusions substantiate those based on demographic characteristics of the dominant tree species, historical aerial photography, and accounts of early settlers and explores. Concurrent changes in soil delta 13C values and organic carbon content over the past 90 years also indicate that wooded landscape elements are behaving as sinks for

  16. Intellectual property rights and challenges for development of affordable human papillomavirus, rotavirus and pneumococcal vaccines: Patent landscaping and perspectives of developing country vaccine manufacturers.

    PubMed

    Chandrasekharan, Subhashini; Amin, Tahir; Kim, Joyce; Furrer, Eliane; Matterson, Anna-Carin; Schwalbe, Nina; Nguyen, Aurélia

    2015-11-17

    The success of Gavi, the Vaccine Alliance depends on the vaccine markets providing appropriate, affordable vaccines at sufficient and reliable quantities. Gavi's current supplier base for new and underutilized vaccines, such as the human papillomavirus (HPV), rotavirus, and the pneumococcal conjugate vaccine is very small. There is growing concern that following globalization of laws on intellectual property rights (IPRs) through trade agreements, IPRs are impeding new manufacturers from entering the market with competing vaccines. This article examines the extent to which IPRs, specifically patents, can create such obstacles, in particular for developing country vaccine manufacturers (DCVMs). Through building patent landscapes in Brazil, China, and India and interviews with manufacturers and experts in the field, we found intense patenting activity for the HPV and pneumococcal vaccines that could potentially delay the entry of new manufacturers. Increased transparency around patenting of vaccine technologies, stricter patentability criteria suited for local development needs and strengthening of IPRs management capabilities where relevant, may help reduce impediments to market entry for new manufacturers and ensure a competitive supplier base for quality vaccines at sustainably low prices.

  17. Intellectual property rights and challenges for development of affordable human papillomavirus, rotavirus and pneumococcal vaccines: Patent landscaping and perspectives of developing country vaccine manufacturers.

    PubMed

    Chandrasekharan, Subhashini; Amin, Tahir; Kim, Joyce; Furrer, Eliane; Matterson, Anna-Carin; Schwalbe, Nina; Nguyen, Aurélia

    2015-11-17

    The success of Gavi, the Vaccine Alliance depends on the vaccine markets providing appropriate, affordable vaccines at sufficient and reliable quantities. Gavi's current supplier base for new and underutilized vaccines, such as the human papillomavirus (HPV), rotavirus, and the pneumococcal conjugate vaccine is very small. There is growing concern that following globalization of laws on intellectual property rights (IPRs) through trade agreements, IPRs are impeding new manufacturers from entering the market with competing vaccines. This article examines the extent to which IPRs, specifically patents, can create such obstacles, in particular for developing country vaccine manufacturers (DCVMs). Through building patent landscapes in Brazil, China, and India and interviews with manufacturers and experts in the field, we found intense patenting activity for the HPV and pneumococcal vaccines that could potentially delay the entry of new manufacturers. Increased transparency around patenting of vaccine technologies, stricter patentability criteria suited for local development needs and strengthening of IPRs management capabilities where relevant, may help reduce impediments to market entry for new manufacturers and ensure a competitive supplier base for quality vaccines at sustainably low prices. PMID:26368398

  18. Indigenous Burning as Conservation Practice: Neotropical Savanna Recovery amid Agribusiness Deforestation in Central Brazil

    PubMed Central

    Welch, James R.; Brondízio, Eduardo S.; Hetrick, Scott S.; Coimbra, Carlos E. A.

    2013-01-01

    International efforts to address climate change by reducing tropical deforestation increasingly rely on indigenous reserves as conservation units and indigenous peoples as strategic partners. Considered win-win situations where global conservation measures also contribute to cultural preservation, such alliances also frame indigenous peoples in diverse ecological settings with the responsibility to offset global carbon budgets through fire suppression based on the presumed positive value of non-alteration of tropical landscapes. Anthropogenic fire associated with indigenous ceremonial and collective hunting practices in the Neotropical savannas (cerrado) of Central Brazil is routinely represented in public and scientific conservation discourse as a cause of deforestation and increased CO2 emissions despite a lack of supporting evidence. We evaluate this claim for the Xavante people of Pimentel Barbosa Indigenous Reserve, Brazil. Building upon 23 years of longitudinal interdisciplinary research in the area, we used multi-temporal spatial analyses to compare land cover change under indigenous and agribusiness management over the last four decades (1973–2010) and quantify the contemporary Xavante burning regime contributing to observed patterns based on a four year sample at the end of this sequence (2007–2010). The overall proportion of deforested land remained stable inside the reserve (0.6%) but increased sharply outside (1.5% to 26.0%). Vegetation recovery occurred where reserve boundary adjustments transferred lands previously deforested by agribusiness to indigenous management. Periodic traditional burning by the Xavante had a large spatial distribution but repeated burning in consecutive years was restricted. Our results suggest a need to reassess overreaching conservation narratives about the purported destructiveness of indigenous anthropogenic fire in the cerrado. The real challenge to conservation in the fire-adapted cerrado biome is the long

  19. Structure of arboreal and herbaceous strata in a neotropical seasonally flooded monodominant savanna of Tabebuia aurea.

    PubMed

    Bueno, M L; Damasceno-Junior, G A; Pott, A; Pontara, V; Seleme, E P; Fava, W S; Salomão, A K D; Ratter, J A

    2014-05-01

    Large areas in the Pantanal wetland are covered by monodominant formations, e.g. typical landscapes with local names such as "paratudal", dominated by T. aurea. Studies on structure of these formations generally include only woody strata, consequently the species richness registered is usually low due to the absence of the 'ground layer' of herbaceous and others low species. We recorded 13 species, 12 genera and 11 families for the arboreal stratum. Considering arboreal flora without the dominant (T. aurea) individuals showed great establishment in relation to the flood level between 35 - 45 cm while the individuals of the dominant species of 30 - 45 cm. The diameter distribution revealed that the population of T. aurea did not show the reverse J curve, the usual pattern for species in constant regeneration, also evidenced in inconstant Licourt quotient, indicating an episodic recruitment that could lead to future changes in structure. In the herbaceous strata we recorded 78 species, included in 62 genera and 27 families. Using plots method we sampled 46 species, 40 genera and 22 families, while in line interception we found 65 species distributed in 57 genera and 26 families. The floristic similarity of Sørensen between both methods was 59.4%, with 33 species in common, and the method of line interception was more efficient in detecting richness, with 35% more species found in the same time. According to the methods of plots and line interception applied on the woody stratum, our results gave similar detailed information on the structure of this type of savanna, and in spite of being monodominant it shows high species richness when the herbaceous stratum is taken into account. Plots and line interception methods showed similar results for the woody stratum and high species richness of the herbaceous stratum.

  20. Indigenous burning as conservation practice: neotropical savanna recovery amid agribusiness deforestation in Central Brazil.

    PubMed

    Welch, James R; Brondízio, Eduardo S; Hetrick, Scott S; Coimbra, Carlos E A

    2013-01-01

    International efforts to address climate change by reducing tropical deforestation increasingly rely on indigenous reserves as conservation units and indigenous peoples as strategic partners. Considered win-win situations where global conservation measures also contribute to cultural preservation, such alliances also frame indigenous peoples in diverse ecological settings with the responsibility to offset global carbon budgets through fire suppression based on the presumed positive value of non-alteration of tropical landscapes. Anthropogenic fire associated with indigenous ceremonial and collective hunting practices in the Neotropical savannas (cerrado) of Central Brazil is routinely represented in public and scientific conservation discourse as a cause of deforestation and increased CO2 emissions despite a lack of supporting evidence. We evaluate this claim for the Xavante people of Pimentel Barbosa Indigenous Reserve, Brazil. Building upon 23 years of longitudinal interdisciplinary research in the area, we used multi-temporal spatial analyses to compare land cover change under indigenous and agribusiness management over the last four decades (1973-2010) and quantify the contemporary Xavante burning regime contributing to observed patterns based on a four year sample at the end of this sequence (2007-2010). The overall proportion of deforested land remained stable inside the reserve (0.6%) but increased sharply outside (1.5% to 26.0%). Vegetation recovery occurred where reserve boundary adjustments transferred lands previously deforested by agribusiness to indigenous management. Periodic traditional burning by the Xavante had a large spatial distribution but repeated burning in consecutive years was restricted. Our results suggest a need to reassess overreaching conservation narratives about the purported destructiveness of indigenous anthropogenic fire in the cerrado. The real challenge to conservation in the fire-adapted cerrado biome is the long

  1. Desert landscape irrigation

    SciTech Connect

    Quinones, R.

    1995-06-01

    Industrialization can take place in an arid environment if a long term, overall water management program is developed. The general rule to follow is that recharge must equal or exceed use. The main problem encountered in landscape projects is that everyone wants a lush jungle setting, tall shade trees, ferns, with a variety of floral arrangements mixed in. What we want, what we can afford, and what we get are not always the same. Vegetation that requires large quantities of water are not native to any desert. Surprisingly; there are various types of fruit trees, and vegetables that will thrive in the desert. Peaches, plums, nut trees, do well with drip irrigation as well as tomatoes. Shaded berry plans will also do well, the strawberry being one. In summary; if we match our landscape to our area, we can then design our irrigation system to maintain our landscape and grow a variety of vegetation in any arid or semiarid environment. The application of science and economics to landscaping has now come of age.

  2. Group Dynamics of Zebra and Wildebeest in a Woodland Savanna: Effects of Predation Risk and Habitat Density

    PubMed Central

    Thaker, Maria; Vanak, Abi T.; Owen, Cailey R.; Ogden, Monika B.; Slotow, Rob

    2010-01-01

    Background Group dynamics of gregarious ungulates in the grasslands of the African savanna have been well studied, but the trade-offs that affect grouping of these ungulates in woodland habitats or dense vegetation are less well understood. We examined the landscape-level distribution of groups of blue wildebeest, Connochaetes taurinus, and Burchell's zebra, Equus burchelli, in a predominantly woodland area (Karongwe Game Reserve, South Africa; KGR) to test the hypothesis that group dynamics are a function of minimizing predation risk from their primary predator, lion, Panthera leo. Methodology/Principal Findings Using generalized linear models, we examined the relative importance of habitat type (differing in vegetation density), probability of encountering lion (based on utilization distribution of all individual lions in the reserve), and season in predicting group size and composition. We found that only in open scrub habitat, group size for both ungulate species increased with the probability of encountering lion. Group composition differed between the two species and was driven by habitat selection as well as predation risk. For both species, composition of groups was, however, dominated by males in open scrub habitats, irrespective of the probability of encountering lion. Conclusions/Significance Distribution patterns of wildebeest and zebra groups at the landscape level directly support the theoretical and empirical evidence from a range of taxa predicting that grouping is favored in open habitats and when predation risk is high. Group composition reflected species-specific social, physiological and foraging constraints, as well as the importance of predation risk. Avoidance of high resource open scrub habitat by females can lead to loss of foraging opportunities, which can be particularly costly in areas such as KGR, where this resource is limited. Thus, landscape-level grouping dynamics are species specific and particular to the composition of the group

  3. Connecting Brabant's cover sand landscapes through landscape history

    NASA Astrophysics Data System (ADS)

    Heskes, Erik; van den Ancker, Hanneke; Jungerius, Pieter Dirk; Harthoorn, Jaap; Maes, Bert; Leenders, Karel; de Jongh, Piet; Kluiving, Sjoerd; van den Oetelaar, Ger

    2015-04-01

    Noord-Brabant has the largest variety of cover sand landscapes in The Netherlands, and probably in Western Europe. During the Last Ice Age the area was not covered by land ice and a polar desert developed in which sand dunes buried the existing river landscapes. Some of these polar dune landscapes experienced a geomorphological and soil development that remained virtually untouched up to the present day, such as the low parabolic dunes of the Strabrechtse Heide or the later and higher dunes of the Oisterwijkse Vennen. As Noord-Brabant lies on the fringe of a tectonic basin, the thickness of cover sand deposits in the Centrale Slenk, part of a rift through Europe, amounts up to 20 metres. Cover sand deposits along the fault lines cause the special phenomenon of 'wijst' to develop, in which the higher grounds are wetter than the boarding lower grounds. Since 4000 BC humans settled in these cover sand landscapes and made use of its small-scale variety. An example are the prehistoric finds on the flanks and the historic towns on top of the 'donken' in northwest Noord-Brabant, where the cover sand landscapes are buried by river and marine deposits and only the peaks of the dunes protrude as donken. Or the church of Handel that is built beside a 'wijst' source and a site of pilgrimage since living memory. Or the 'essen' and plaggen agriculture that developed along the stream valleys of Noord-Brabant from 1300 AD onwards, giving rise to geomorphological features as 'randwallen' and plaggen soils of more than a metre thickness. Each region of Brabant each has its own approach in attracting tourists and has not yet used this common landscape history to connect, manage and promote their territories. We propose a landscape-historical approach to develop a national or European Geopark Brabants' cover sand landscapes, in which each region focuses on a specific part of the landscape history of Brabant, that stretches from the Late Weichselian polar desert when the dune

  4. Modeling the habitat range of phototrophs in yellowstone national park: toward the development of a comprehensive fitness landscape.

    PubMed

    Boyd, Eric S; Fecteau, Kristopher M; Havig, Jeff R; Shock, Everett L; Peters, John W

    2012-01-01

    The extent to which geochemical variation shapes the distribution of phototrophic metabolisms was modeled based on 439 observations in geothermal springs in Yellowstone National Park (YNP), Wyoming. Generalized additive models (GAMs) were developed to predict the distribution of phototrophic metabolism as a function of spring temperature, pH, and total sulfide. GAMs comprised of temperature explained 38.8% of the variation in the distribution of phototrophic metabolism, whereas GAMs comprised of sulfide and pH explained 19.6 and 11.2% of the variation, respectively. These results suggest that of the measured variables, temperature is the primary constraint on the distribution of phototrophs in YNP. GAMs comprised of multiple variables explained a larger percentage of the variation in the distribution of phototrophic metabolism, indicating additive interactions among variables. A GAM that combined temperature and sulfide explained the greatest variation in the dataset (53.4%) while minimizing the introduction of degrees of freedom. In an effort to verify the extent to which phototroph distribution reflects constraints on activity, we examined the influence of sulfide and temperature on dissolved inorganic carbon (DIC) uptake rates under both light and dark conditions. Light-driven DIC uptake decreased systematically with increasing concentrations of sulfide in acidic, algal-dominated systems, but was unaffected in alkaline, cyanobacterial-dominated systems. In both alkaline and acidic systems, light-driven DIC uptake was suppressed in cultures incubated at temperatures 10°C greater than their in situ temperature. Collectively, these quantitative results indicate that apart from light availability, the habitat range of phototrophs in YNP springs is defined largely by constraints imposed firstly by temperature and secondly by sulfide on the activity of these populations that inhabit the edges of the habitat range. These findings are consistent with the predictions

  5. Geomorphology of anthropogenic landscapes

    NASA Astrophysics Data System (ADS)

    Sofia, Giulia; Tarolli, Paolo

    2015-04-01

    The construction of urban areas and the development of road networks leave a significant signature on the Earth surface, providing a geomorphological evidence to support the idea that humans are nowadays a geomorphic agent having deep effects on the morphological organization of the landscape. The reconstruction or identification of anthropogenic topographies, therefore, provides a mechanism for quantifying anthropogenic changes to the landscape systems in the Anthropocene. Following this research line, the present study tests the effectiveness of a recently published topographic index, the Slope Local Length of Autocorrelation (SLLAC, Sofia et al. 2014) to portrait anthropogenic geomorphology, focusing in particular on road network density, and urban complexity (UCI). At first, the research considers the increasing of anthropic structures and the resulting changes in the SLLAC and in two derived parameters (mean SLLAC per km2 and SLLAC roughness, or Surface Peak Curvature -Spc). As a second step, considering the SLLAC derived indices, the anthropogenic geomorphology is automatically depicted using a k-means clustering algorithm. In general, the increasing of road network density or of the UCI is positively correlated to the mean SLLAC per km2, while the Spc is negatively correlated to the increasing of the anthropic structures. Areas presenting different road network organization are effectively captured considering multiple combinations of the defined parameters. Landscapes with small scattered towns, and a network with long roads in a dendritic shape (with hierarchical branching) are characterized simultaneously by high mean SLLAC and low Spc. Large and complex urban areas served by rectilinear networks with numerous short straight lines and right angles, have either a maximized mean SLLAC or a minimized Spc or both. In all cases, the anthropogenic landscape identified by the procedure is comparable to the ones identified manually from orthophoto, with the

  6. Land Use Change In Australia's Tropical Savanna Woodlands: Greenhouse Gas Emissions From Deforestation And Conversion To Agriculture

    NASA Astrophysics Data System (ADS)

    Hutley, L. B.; Bristow, M.; Beringer, J.; Livesley, S. L.; Arndt, S. K.

    2015-12-01

    Clearing and burning of tropical savanna leads to globally significant emissions of greenhouse gases (GHG), although there is large uncertainty relating to the magnitude of this flux. Australia's tropical savannas are 12% of global savanna extent and are largely intact; however there is currently a focus on agricultural expansion across northern Australia involving clearing for primary production. Eddy covariance and soil chamber methods were used over almost 2 years to quantify CO2 and non-CO2 fluxes from savanna that was cleared and prepared for agriculture (CS). Fluxes from an uncleared site (UC) were also monitored. Carbon fluxes from both sites were similar (NEE -0.23 Mg C ha-1 month-1) for the 5.4 months prior to clearing, a period spanning the late dry to mid-wet season. Fluxes were monitored for a further 17 months through a dry-wet-dry climate cycle and phased land use change which included clearing and a debris curing phase, followed by burning and soil preparation for cropping. Over this period (excluding the managed fire), the CS site was a source of +0.43 Mg C ha-1 month-1 compared to a net sink at the UC site of -0.05 Mg C ha-1 month-1. Woody debris from clearing (30.9 Mg C ha-1) was removed from the site via burning in the late dry season and emission factors were used to calculate emissions of CO2, CH4 and N2O which totalled 138.0 Mg CO2-e ha-1. Over the 17 months of monitoring this land transformation, emissions were +9.7 Mg CO2-e ha-1 month-1 compared to a sink of -0.17 Mg CO2-e from the UC site. Using these emissions and LUC scenarios at catchment to regional scales suggest proposed clearing for agriculture could significantly increase the region's fire-dominated GHG emissions. These data are essential for both land-atmosphere models as well as decision support tools that inform trade-offs between greenhouse gas accounting, conservation and development goals.

  7. The farmer as a landscape steward: Comparing local understandings of landscape stewardship, landscape values, and land management actions.

    PubMed

    Raymond, Christopher M; Bieling, Claudia; Fagerholm, Nora; Martin-Lopez, Berta; Plieninger, Tobias

    2016-03-01

    We develop a landscape stewardship classification which distinguishes between farmers' understanding of landscape stewardship, their landscape values, and land management actions. Forty semi-structured interviews were conducted with small-holder (<5 acres), medium-holders (5-100 acres), and large-holders (>100 acres) in South-West Devon, UK. Thematic analysis revealed four types of stewardship understandings: (1) an environmental frame which emphasized the farmers' role in conserving or restoring wildlife; (2) a primary production frame which emphasized the farmers' role in taking care of primary production assets; (3) a holistic frame focusing on farmers' role as a conservationist, primary producer, and manager of a range of landscape values, and; (4) an instrumental frame focusing on the financial benefits associated with compliance with agri-environmental schemes. We compare the landscape values and land management actions that emerged across stewardship types, and discuss the global implications of the landscape stewardship classification for the engagement of farmers in landscape management.

  8. Methane production from mixed tropical savanna and forest vegetation in Venezuela

    NASA Astrophysics Data System (ADS)

    Crutzen, P. J.; Sanhueza, E.; Brenninkmeijer, C. A. M.

    2006-04-01

    Measurements of methane concentrations in the boundary layer in the northern part of the Guayana shield, Venezuela, during the wet season (October 1988), showed the presence of substantial methane surface emissions. The measuring site is within the savanna climate region, but is affected by emissions from savanna and forest vegetation. From day versus night concentration measurements, with higher concentrations during night, a methane source strength near the site of 3-7×1011 molecules/cm2/s can be estimated, which includes emissions from small tracts of flooded soils, termites and especially tropical vegetation. Extrapolated to the entire savanna, this may imply a methane source of ~30-60 Tg yr-1 similar to the one calculated for tropical vegetation on the basis of recently published in vitro plant emission experiments by Keppler et al. (2006), which indicate emissions of ~30 Tg yr-1 for tropical savannas and grasslands and ~78 Tg yr-1 for tropical forests.

  9. Measuring and Modelling the Carbon Balance of Pinus palustris Savannas

    NASA Astrophysics Data System (ADS)

    Wright, J. K.; Williams, M. D.; Mitchell, R. J.; Starr, G.; McGee, J.; Whelan, A.

    2011-12-01

    Longleaf pine savannas currently occupy 1.4 million hectares in the South Eastern USA - only 2.6% of their original range. These fire-dependent ecosystems are highly biodiverse and of economic and ecological importance to the region. This region of the United States, however, is increasingly prone to severe drought, including a classified "exceptional" drought in 2011. Drought occurrence and severity are likely to increase in future climate scenarios. Moreover, increasing drought and accompanying wildfire will influence the carbon balance of the South East, a region identified as having the highest carbon sequestration potential in the USA. Thus, understanding the effects of drought on the native longleaf pine savanna land cover, therefore, is of both scientific and economic interest. Longleaf pine exists over a wide soil moisture gradient, driven by the texture and drainage capacity of the soils. These ecosystems therefore provide a natural laboratory for exploring the interaction between productivity, fire and water use. Here we present results of a 3 year study comparing the ecophysiology and carbon balance of two adjacent (5 mile separation) longleaf pine savanna flux sites, one xeric, one mesic. A process-based model (Soil-Plant-Atmosphere - SPA) and leaf-level measurements of photosynthesis and water use in drought and non-drought periods have enabled the authors to partition the carbon fluxes observed at each site into three functional groups (C4 understorey, C3 canopy and mid-storey). Results of this study show that the comparative overall productivity of wet and dry longleaf pine savannas varies through the year, with both wet and dry sites achieving similar productivity in the summer months but with the wet site exceeding the dry site during winter. We hypothesise that this difference is due to the activity of the seasonal C4 understorey. Results from SPA, flux data and field measurements suggest the understorey, dominated by the C4 grass Aristida stricta

  10. Land-atmosphere interactions in the West African Savanna

    NASA Astrophysics Data System (ADS)

    Parlange, M. B.; Ceperley, N. C.; Mande, T.; Bassiouni, M.; Van De Giesen, N.; Tyler, S. W.

    2012-12-01

    Continuous field observations in southeastern Burkina - Faso, since 2008, have been undertaken to observe and understand the diurnal and seasonal hydrologic behavior in this sensitive zone for global circulation patterns. Though this is an important region in the context of global hydrology it remains largely ungauged with minimal observation. To advance hydrology it becomes essential to start to measure at field scales of interest. Within a small watershed (< 4 km2), with mixed agriculture and Savanna forest, the ephemeral stream flow, surface energy balance, vegetation dynamics, and regional micrometeorology and soil moisture have been monitored using distributed environmental sensor networks, eddy correlation towers, stream gauging, sap flow monitoring and isotope sampling. The pattern of changes that take place during the wet season transitions and the coupling of local water resources with evaporation into the atmosphere are highlighted. The applications of robust evaporation models are discussed.

  11. Geostatistical analyses reveal nutrient-vegetation relationships in savanna soils

    NASA Astrophysics Data System (ADS)

    Mladenov, N.; Okin, G. S.; Cassel, D.; Caylor, K. C.; Clausen, K. M.

    2005-12-01

    The uniform Kalahari sands that underlay the Kalahari Transect (KT) are a unique test bed for examining soil nutrient and vegetation cover relationships in a savanna ecosystem. Transects (300m x 100m) were sampled and mapped for each of four sites located along an aridity gradient from Mongu, Zambia in the north (1600 mm/yr precipitation), to Tshane, Botswana in the south (250 mm/yr precipitation). Geostatistical analyses of soil chemistry and tree, shrub, and grass cover at four sites along the moisture gradient of the KT indicated an accumulation of nutrients below tree/shrub cover. In general, areas where grasses dominated between canopies were negatively correlated with soil nutrients at the drier sites. Here we examine effects of vegetation cover on soil productivity and differences in soil nutrients along the moisture gradient of the KT.

  12. How soil shapes the landscape

    NASA Astrophysics Data System (ADS)

    Minasny, Budiman; Finke, Peter; Vanwalleghem, Tom Tom; Stockmann, Uta; McBratney, Alex

    2014-05-01

    There has been an increase in interest in quantitative modelling of soil genesis, which can provide prediction of environmental changes through numerical models. Modelling soil formation is a difficult task because soil itself is highly complex with interactions between water, inorganic materials and organic matter. This paper will provide a review on the research efforts of modelling soil genesis, their connection with landscape models and the inexorable genesis of the IUSS soil landscape modelling working group. Quantitative modelling soil formation using mechanistic models have begun in the 1980s such as the 'soil deficit' model by Kirkby (1985), Hoosbeek & Bryant's pedodynamic model (1992), and recently the SoilGen model by Finke (2008). These profile models considered the chemical reactions and physical processes in the soil at the horizon and pedon scale. The SoilGen model is an integration of sub-models, such as water and solute movement, heat transport, soil organic matter decomposition, mineral dissolution, ion exchange, adsorption, speciation, complexation and precipitation. The model can calculate with detail the chemical changes and materials fluxes in a profile and has been successfully applied. While they can simulate soil profile development in detail, there is still a gap how the processes act in the landscape. Meanwhile research in landscape formation in geomorphology is progressing steadily over time, slope development models model have been developed since 1970s (Ahnert, 1977). Soil was also introduced in a landscape, however soil processes are mainly modelled through weathering and transport processes (Minasny & McBratney 1999, 2001). Recently, Vanwalleghem et al. (2013) are able to combine selected physical, chemical and biological processes to simulate a full 3-D soil genesis in the landscape. Now there are research gaps between the 2 approaches: the landscape modellers increasingly recognise the importance of soil and need more detailed soil

  13. Sleeping site selection by savanna chimpanzees in Ugalla, Tanzania.

    PubMed

    Ogawa, Hideshi; Yoshikawa, Midori; Idani, Gen'ichi

    2014-04-01

    We examined sleeping site selection by chimpanzees (Pan troglodytes) in the Ugalla savanna woodland area, western Tanzania, from 1994 to 2012. We established 488 km of line transects and recorded 379 chimpanzee beds within 30 m perpendicular to the transects. Comparisons between 60 × 60 m(2) quadrats containing new and recent beds and the remaining quadrats without beds along the transects indicated that evergreen forests accounted for disproportionately more area in quadrats with beds than in those without beds during both the dry and rainy seasons. In Ugalla, chimpanzees coexist with lions (Panthera leo) and leopards (Panthera pardus). They may sleep in forests to reduce predation risk by these carnivores, as trees are dense and the canopy is high and closed. The angle of slope was steeper in quadrats containing beds than in those without beds during the dry season, whereas the angle was less steep in quadrats with beds than in those without beds during the rainy season. Additionally, fewer beds were found further from forests. The distance between beds and forests during the dry season was shorter than that during the rainy season. Chimpanzees may sleep in or near forests and on slopes because of water pools in the valley forests along the slopes during the dry season. Quadrats with beds were at slightly higher altitude than those without beds during the rainy season; however, the difference was not significant during the dry season. The number of beds found in or close to feeding trees was not related to the fruiting period. Sleeping site selection by chimpanzees may be affected by predation pressure and water availability in the savanna woodland area.

  14. Distinctiveness, use, and value of midwestern oak savannas and woodlands as avian habitats

    USGS Publications Warehouse

    Grundel, R.; Pavlovic, N.B.

    2007-01-01

    Oak savannas and woodlands historically covered millions of hectares in the midwestern United States but are rare today. We evaluated the ecological distinctiveness and conservation value of savannas and woodlands by examining bird distributions across a fire-maintained woody-vegetation gradient in northwest Indiana encompassing five habitats—open habitats with low canopy cover, savannas, woodlands, scrublands, and forests—during migration, breeding, and overwintering. Savannas and woodlands were significantly different in overall bird species composition from open and forest habitats but were often intermediate between open and forest in guild densities. Few bird species were consistently and highly concentrated in savannas or woodlands, and the Red-headed Woodpecker (Melanerpes erythrocephalus) was the only species significantly more abundant in savannas and woodlands than in open, scrub, and forest habitats. Fire frequency over a 15-year interval was a significant predictor of bird community composition and was positively related to species diversity, spring transient migrant density, and density of the most threatened species. Each habitat type had characteristics potentially important for avian conservation. Scrub had the highest density of transient migrants, which suggests it plays an important role as migration stopover habitat. More species were significantly concentrated in open or forest habitats than in the other habitats. Lack of species concentration and intermediate community composition suggested that birds experienced savannas and woodlands more as ecotones than as habitats distinct from forests or grasslands. However, this intermediate character can benefit conservation, as evidenced by savannas and woodlands having the highest density of the most threatened species along this woody-vegetation gradient.

  15. Climate Change and Long-Term Fire Management Impacts on Australian Savanna

    NASA Astrophysics Data System (ADS)

    Scheiter, S.; Higgins, S. I.; Beringer, J.; Hutley, L. B.

    2014-12-01

    Tropical savannas cover a large proportion of the Earth's land surface and many people are dependent on the ecosystem services that savannas supply. Their sustainable management is therefore crucial. Due to the complexity of vegetation dynamics, the impacts of climate change and land use on savannas are highly uncertain. Here, we use a dynamic vegetation model, the aDGVM, to project how climate change and fire management influence vegetation in northern Australian savannas in 2100. We show that under future climate conditions, vegetation can store more carbon than under ambient conditions, despite substantial changes in fire regimes. Changes in rainfall seasonality influence future carbon storage but do not turn vegetation into a carbon source, suggesting that CO2 fertilization is the main driver of vegetation change. The application of prescribed fires with varying return intervals and burning season, influences vegetation dynamics and fire induced carbon and greenhouse gas emissions. Carbon sequestration is maximized with early dry season fires and long fire return intervals, grass productivity is maximized with late dry season fires at an intermediate fire return intervals. The study has implications for management policy across Australian savannas because it can contribute to identifying fire management strategies that optimize grazing yield, carbon sequestration and greenhouse gas emissions. This knowledge is crucial to maintain important ecosystem services of Australian savannas.

  16. Wildfire and landscape change

    USGS Publications Warehouse

    Santi, P.; Cannon, S.; DeGraff, J.

    2013-01-01

    Wildfire is a worldwide phenomenon that is expected to increase in extent and severity in the future, due to fuel accumulations, shifting land management practices, and climate change. It immediately affects the landscape by removing vegetation, depositing ash, influencing water-repellent soil formation, and physically weathering boulders and bedrock. These changes typically lead to increased erosion through sheetwash, rilling, dry ravel, and increased mass movement in the form of floods, debris flow, rockfall, and landslides. These process changes bring about landform changes as hillslopes are lowered and stream channels aggrade or incise at increased rates. Furthermore, development of alluvial fans, debris fans, and talus cones are enhanced. The window of disturbance to the landscape caused by wildfire is typically on the order of three to four years, with some effects persisting up to 30 years.

  17. Landscaping for energy efficiency

    SciTech Connect

    1995-04-01

    This publication by the National Renewable Energy Laboratory addresses the use of landscaping for energy efficiency. The topics of the publication include minimizing energy expenses; landscaping for a cleaner environment; climate, site, and design considerations; planning landscape; and selecting and planting trees and shrubs. A source list for more information on landscaping for energy efficiency and a reading list are included.

  18. Vulnerability and Resilience of Temperate Forest Landscapes to Broad-Scale Deforestation in Response to Changing Fire Regimes and Altered Post-Fire Vegetation Dynamics

    NASA Astrophysics Data System (ADS)

    Tepley, A. J.; Veblen, T. T.; Perry, G.; Anderson-Teixeira, K. J.

    2015-12-01

    In the face of on-going climatic warming and land-use change, there is growing concern that temperate forest landscapes could be near a tipping point where relatively small changes to the fire regime or altered post-fire vegetation dynamics could lead to extensive conversion to shrublands or savannas. To evaluate vulnerability and resilience to such conversion, we develop a simple model based on three factors we hypothesize to be key in predicting temperate forest responses to changing fire regimes: (1) the hazard rate (i.e., the probability of burning in the next year given the time since the last fire) in closed-canopy forests, (2) the hazard rate for recently-burned, open-canopy vegetation, and (3) the time to redevelop canopy closure following fire. We generate a response surface representing the proportions of the landscape potentially supporting closed-canopy forest and non-forest vegetation under nearly all combinations of these three factors. We then place real landscapes on this response surface to assess the type and magnitude of changes to the fire regime that would drive extensive forest loss. We show that the deforestation of much of New Zealand that followed initial human colonization and the introduction of a new ignition source ca. 750 years ago was essentially inevitable due to the slow rate of forest recovery after fire and the high flammability of post-fire vegetation. In North America's Pacific Northwest, by contrast, a predominantly forested landscape persisted despite two periods of widespread burning in the recent past due in large part to faster post-fire forest recovery and less pronounced differences in flammability between forests and the post-fire vegetation. We also assess the factors that could drive extensive deforestation in other regions to identify where management could reduce this potential and to guide field and modeling work to better understand the responses and ecological feedbacks to changing fire regimes.

  19. Introduction to landscape influences on stream habitats and biological assemblages

    EPA Science Inventory

    Viewing river systems within a landscape context is a relatively new and rapidly developing approach to river ecology. Although the linkages among landscapes and associated physicochemical and biological characteristics of rivers have long been recognized, the development of con...

  20. Lightning fires in North Dakota grasslands and in pine-savanna lands of South Dakota and Montana

    USGS Publications Warehouse

    Higgins, K.F.

    1984-01-01

    Lightning strike fires which occurred between 1940 and 1981 were studied in mixed-grass prairie grasslands and in pine-savanna lands in the Northern Great Plains region. A majority (73%) of ignitions occurred during July and August, while a lesser number was recorded in April, May, June, and September. The April-September period is also the average time of the freeze-free period and approximates the average distribution period for thunderstorm activity in this region. The area burned by each of 293 lightning fires (most of which were suppressed) ranged from 0.004-1158.3 ha (mean = 10.8 ha). The frequency of lightning fires in mixed-grass prairie grasslands averaged 6.0/yr per 10,000 km2 in eastern North Dakota, 22.4/yr per 10,000 km2 in southcentral North Dakota, 24.7/yr per 10,000 km2 in western North Dakota, and 91.7/yr per 10,000 km2 in pine-savanna lands in northwestern South Dakota and southeastern Montana. The ecological role of lightning-set fires is discussed relative to the development of resource research and management plans and to the interpretation of historical records of natural fire occurrence in the Northern Great Plains region.

  1. The Development of Topography in Ancient and Active Orogens: Case Studies of Landscape Evolution in the Southern Appalachians, USA and Crete, Greece

    NASA Astrophysics Data System (ADS)

    Gallen, Sean Francis

    Understanding the development of topography is fundamental to the geosciences. Topography represents the sum of all tectonic and geodynamic processes that force the earth's surface upward paired with those that act to bring it down. Spatial and temporal changes in topographic relief can modulate the various feedbacks between atmospheric, earth surface and rock exhumation processes, sediment flux, and the magnitude and style of gravity driven natural hazards. Plate tectonics provides the first-order framework necessary to understand how topography is built through the interaction of lithospheric plates. However, density contrasts in the mantle can also influence the elevation of the earth's surface through dynamic topography, while poorly understood nuances of mountain building at convergent margins complicate drawing direct connections between tectonics and topography. Such linkages are further confounded by non-linearity between rock uplift and erosion, variations in rates of deformation, changes in climate and the properties of bedrock. Great advances in our understanding of the evolution of topography have been achieved, yet numerous questions remain regarding the evolution of topography in ancient and active orogens. This research addresses knowledge gaps in the development of topography through case-studies of landscape evolution in the southern Appalachians Mountains, USA and the forearc overlying the Hellenic subduction zone. Chapter 1 explores the origins of modern topographic relief in the southern Appalachians, where tectonic activity ceased prior to 200 Ma. Conventional theories invoked to explain modern relief in the region are challenged. Quantitative analyses of digital elevation models and numerical modeling are coupled to provide the magnitudes and timing of changes in topographic relief. The results suggest that the southern Appalachians experienced a phase of topographic rejuvenation during the Miocene that increased the distance between the

  2. Understanding cultural and environmental archaeological records within Holocene alluvial landscapes in the UK: developing an integrated tool-kit approach to geoprospection

    NASA Astrophysics Data System (ADS)

    Howard, Andy

    2013-04-01

    The river valleys of the UK preserve a rich record of post-glacial human activity, which reflects both the attraction of such landscapes for human settlement and the preservation of both cultural and environmental remains under the (relatively) high groundwater tables that have existed for most of the Holocene. The juxtaposition of cultural and environmental records in such environments provides significant opportunities for archaeologists to reconstruct high resolution, extended records of both cultural and environmental landscape development. However, the evolution of these natural sedimentary environments is complex and is influenced by both natural climate cycles (changing flood frequency and magnitude) as well as anthropogenic activity (through deforestation and transformation of local hydrological conditions). Therefore, producing meaningful spatial and temporal datasets requires the collaboration of archaeologists with a range of complementary technical skills from the design stage of individual projects. Using a series of case studies from a number of river valleys, this paper will outline the multi-method toolkit approach developed in the UK and evaluate the validity of such models for enhancing our knowledge of alluvial archaeological records. The paper will conclude by considering how such methodological approaches can be further refined and enhance our understanding of the resilience of human communities to future environmental change.

  3. Probing the String Landscape

    ScienceCinema

    Keith Dienes

    2016-07-12

    We are currently in the throes of a potentially huge paradigm shift in physics. Motivated by recent developments in string theory and the discovery of the so-called "string landscape", physicists are beginning to question the uniqueness of fundamental theories of physics and the methods by which such theories might be understood and investigated. In this colloquium, I will give a non-technical introduction to the nature of this paradigm shift and how it developed. I will also discuss some of the questions to which it has led, and the nature of the controversies it has spawned.

  4. Probing the String Landscape

    SciTech Connect

    Keith Dienes

    2009-12-01

    We are currently in the throes of a potentially huge paradigm shift in physics. Motivated by recent developments in string theory and the discovery of the so-called "string landscape", physicists are beginning to question the uniqueness of fundamental theories of physics and the methods by which such theories might be understood and investigated. In this colloquium, I will give a non-technical introduction to the nature of this paradigm shift and how it developed. I will also discuss some of the questions to which it has led, and the nature of the controversies it has spawned.

  5. Applying landscape genetics to the microbial world.

    PubMed

    Dudaniec, Rachael Y; Tesson, Sylvie V M

    2016-07-01

    Landscape genetics, which explicitly quantifies landscape effects on gene flow and adaptation, has largely focused on macroorganisms, with little attention given to microorganisms. This is despite overwhelming evidence that microorganisms exhibit spatial genetic structuring in relation to environmental variables. The increasing accessibility of genomic data has opened up the opportunity for landscape genetics to embrace the world of microorganisms, which may be thought of as 'the invisible regulators' of the macroecological world. Recent developments in bioinformatics and increased data accessibility have accelerated our ability to identify microbial taxa and characterize their genetic diversity. However, the influence of the landscape matrix and dynamic environmental factors on microorganism genetic dispersal and adaptation has been little explored. Also, because many microorganisms coinhabit or codisperse with macroorganisms, landscape genomic approaches may improve insights into how micro- and macroorganisms reciprocally interact to create spatial genetic structure. Conducting landscape genetic analyses on microorganisms requires that we accommodate shifts in spatial and temporal scales, presenting new conceptual and methodological challenges not yet explored in 'macro'-landscape genetics. We argue that there is much value to be gained for microbial ecologists from embracing landscape genetic approaches. We provide a case for integrating landscape genetic methods into microecological studies and discuss specific considerations associated with the novel challenges this brings. We anticipate that microorganism landscape genetic studies will provide new insights into both micro- and macroecological processes and expand our knowledge of species' distributions, adaptive mechanisms and species' interactions in changing environments.

  6. Soil moisture redistribution as a mechanism of facilitation in savanna tree-shrub clusters.

    PubMed

    Zou, C B; Barnes, P W; Archer, S; McMurtry, C R

    2005-08-01

    Plant-soil water relations were examined in the context of a selective removal study conducted in tree-shrub communities occupying different but contiguous soil types (small discrete clusters on shallow, duplex soils versus larger, extensive groves on deep, sandy soils) in a subtropical savanna parkland. We (1) tested for the occurrence of soil moisture redistribution by hydraulic lift (HL), (2) determined the influence of edaphic factors on HL, and (3) evaluated the significance of HL for overstory tree-understory shrub interactions. Diel cycling and nocturnal increases in soil water potential (Psisoil), characteristic signatures of HL, occurred intermittently throughout an annual growth cycle in both communities over a range of moisture levels (Psisoil=-0.5 to -6.0 MPa) but only when soils were distinctly stratified with depth (dry surface/wet deep soil layers). The magnitude of mean (+/-SE) diel fluctuations in Psisoil (0.19+/-0.01 MPa) did not differ on the two community types, though HL occurred more frequently in groves (deep soils) than clusters (shallow soils). Selective removal of either Prosopis glandulosa overstory or mixed-species shrub understory reduced the frequency of HL, indicating that Prosopis and at least one other woody species was conducting HL. For Zanthoxylum fagara, a shallow-rooted understory shrub, Prosopis removal from clusters decreased leaf water potential (Psileaf) and net CO2 exchange (A) during periods of HL. In contrast, overstory removal had neutral to positive effects on more deeply-rooted shrub species (Berberis trifoliolata and Condalia hookeri). Removal of the shrub understory in groves increased A in the overstory Prosopis. Results indicate the following: (a) HL is common but temporally dynamic in these savanna tree-shrub communities; (b) edaphic factors influencing the degree of overstory/understory development, rooting patterns and soil moisture distribution influence HL; (c) net interactions between overstory and

  7. Savanna Tree Seedlings are Physiologically Tolerant to Nighttime Freeze Events

    PubMed Central

    O’Keefe, Kimberly; Nippert, Jesse B.; Swemmer, Anthony M.

    2016-01-01

    Freeze events can be important disturbances in savanna ecosystems, yet the interactive effect of freezing with other environmental drivers on plant functioning is unknown. Here, we investigated physiological responses of South African tree seedlings to interactions of water availability and freezing temperatures. We grew widely distributed South African tree species (Colophospermum mopane, Combretum apiculatum, Acacia nigrescens, and Cassia abbreviata) under well-watered and water-limited conditions and exposed individuals to nighttime freeze events. Of the four species studied here, C. mopane was the most tolerant of lower water availability. However, all species were similarly tolerant to nighttime freezing and recovered within one week following the last freezing event. We also show that water limitation somewhat increased freezing tolerance in one of the species (C. mopane). Therefore, water limitation, but not freezing temperatures, may restrict the distribution of these species, although the interactions of these stressors may have species-specific impacts on plant physiology. Ultimately, we show that unique physiologies can exist among dominant species within communities and that combined stresses may play a currently unidentified role in driving the function of certain species within southern Africa. PMID:26870065

  8. Soil microbial communities following bush removal in a Namibian savanna

    NASA Astrophysics Data System (ADS)

    Buyer, J. S.; Schmidt-Küntzel, A.; Nghikembua, M.; Maul, J. E.; Marker, L.

    2015-12-01

    Savanna ecosystems are subject to desertification and bush encroachment, which reduce the carrying capacity for wildlife and livestock. Bush thinning is a management approach that can, at least temporarily, restore grasslands and raise the grazing value of the land. In this study we examined the soil microbial communities under bush and grass in Namibia. We analyzed the soil through a chronosequence where bush was thinned at 9, 5, or 3 years before sampling. Soil microbial biomass, the biomass of specific taxonomic groups, and overall microbial community structure was determined by phospholipid fatty acid analysis, while the community structure of Bacteria, Archaea, and fungi was determined by multiplex terminal restriction fragment length polymorphism analysis. Soil under bush had higher pH, C, N, and microbial biomass than under grass, and the microbial community structure was also altered under bush compared to grass. A major disturbance to the ecosystem, bush thinning, resulted in an altered microbial community structure compared to control plots, but the magnitude of this perturbation gradually declined with time. Community structure was primarily driven by pH, C, and N, while vegetation type, bush thinning, and time since bush thinning were of secondary importance.

  9. Will savannas survive outside the parks? A lesson from Zambia

    NASA Astrophysics Data System (ADS)

    Kutsch, W.; Merbold, L.; Scholes, B.; Mukelabai, M.

    2012-04-01

    Miombo woodlands cover the transition zone between dry open savannas and moist forests in Southern Africa. They cover about 2.7 million km2 in southern Africa and provide many ecosystem services that support rural life, including medical products, wild foods, construction timber and fuel. In Zambia, as in many of its neighbouring countries, miombo woodlands are currently experiencing accelerating degradation and clearing, mostly with charcoal production as the initial driver. Domestic energy needs in the growing urban areas are largely satisfied by charcoal, which is less energy-efficient fuel on a tree-to-table basis than the firewood that is used in rural areas, but has a higher energy density and is thus cheaper to transport. This study uses data from inventories and from eddy covariance measurements of carbon exchange to characterize the impact of charcoal production on miombo woodlands. We address the following questions: (i) how much carbon is lost at local as well as at national scale and (ii) does forest degradation result in the loss of a carbon sink? On the basis of our data we (iii) estimate the per capita emissions through deforestation and forest degradation in Zambia and relate it to fossil fuel emissions. Furthermore, (iv) a rough estimate of the energy that is provided by charcoal production to private households at a national level is calculated and (v) options for alternative energy supply to private households are discussed.

  10. Soil microbial communities following bush removal in a Namibian savanna

    NASA Astrophysics Data System (ADS)

    Buyer, Jeffrey S.; Schmidt-Küntzel, Anne; Nghikembua, Matti; Maul, Jude E.; Marker, Laurie

    2016-03-01

    Savanna ecosystems are subject to desertification and bush encroachment, which reduce the carrying capacity for wildlife and livestock. Bush thinning is a management approach that can, at least temporarily, restore grasslands and raise the grazing value of the land. In this study we examined the soil microbial communities under bush and grass in Namibia. We analyzed the soil through a chronosequence where bush was thinned at 9, 5, or 3 years before sampling. Soil microbial biomass, the biomass of specific taxonomic groups, and overall microbial community structure was determined by phospholipid fatty acid analysis, while the community structure of Bacteria, Archaea, and fungi was determined by multiplex terminal restriction fragment length polymorphism analysis. Soil under bush had higher pH, C, N, and microbial biomass than under grass, and the microbial community structure was also altered under bush compared to grass. A major disturbance to the ecosystem, bush thinning, resulted in an altered microbial community structure compared to control plots, but the magnitude of this perturbation gradually declined with time. Community structure was primarily driven by pH, C, and N, while vegetation type, bush thinning, and time since bush thinning were of secondary importance.

  11. Savanna Tree Seedlings are Physiologically Tolerant to Nighttime Freeze Events.

    PubMed

    O'Keefe, Kimberly; Nippert, Jesse B; Swemmer, Anthony M

    2016-01-01

    Freeze events can be important disturbances in savanna ecosystems, yet the interactive effect of freezing with other environmental drivers on plant functioning is unknown. Here, we investigated physiological responses of South African tree seedlings to interactions of water availability and freezing temperatures. We grew widely distributed South African tree species (Colophospermum mopane, Combretum apiculatum, Acacia nigrescens, and Cassia abbreviata) under well-watered and water-limited conditions and exposed individuals to nighttime freeze events. Of the four species studied here, C. mopane was the most tolerant of lower water availability. However, all species were similarly tolerant to nighttime freezing and recovered within one week following the last freezing event. We also show that water limitation somewhat increased freezing tolerance in one of the species (C. mopane). Therefore, water limitation, but not freezing temperatures, may restrict the distribution of these species, although the interactions of these stressors may have species-specific impacts on plant physiology. Ultimately, we show that unique physiologies can exist among dominant species within communities and that combined stresses may play a currently unidentified role in driving the function of certain species within southern Africa. PMID:26870065

  12. Palaeoenvironments of insular Southeast Asia during the Last Glacial Period: a savanna corridor in Sundaland?

    NASA Astrophysics Data System (ADS)

    Bird, Michael I.; Taylor, David; Hunt, Chris

    2005-11-01

    Consideration of a range of evidence from geomorphology, palynology, biogeography and vegetation/climate modelling suggests that a north-south 'savanna corridor' did exist through the continent of Sundaland (modern insular Indonesia and Malaysia) through the Last Glacial Period (LGP) at times of lowered sea-level, as originally proposed by Heaney [1991. Climatic Change 19, 53-61]. A minimal interpretation of the size of this corridor requires a narrow but continuous zone of open 'savanna' vegetation 50-150 km wide, running along the sand-covered divide between the modern South China and Java Seas. This area formed a land bridge between the Malaysian Peninsula and the major islands of Sumatra, Java and Borneo. The savanna corridor connected similar open vegetation types north and south of the equator, and served as a barrier to the dispersal of rainforest-dependent species between Sumatra and Borneo. A maximal interpretation of the available evidence is compatible with the existence of a broad savanna corridor, with forest restricted to refugia primarily in Sumatra, Borneo and the continental shelf beneath the modern South China Sea. This savanna corridor may have provided a convenient route for the rapid early dispersal of modern humans through the region and on into Australasia.

  13. Distinguishing forest and savanna African elephants using short nuclear DNA sequences.

    PubMed

    Ishida, Yasuko; Demeke, Yirmed; van Coeverden de Groot, Peter J; Georgiadis, Nicholas J; Leggett, Keith E A; Fox, Virginia E; Roca, Alfred L

    2011-01-01

    A more complete description of African elephant phylogeography would require a method that distinguishes forest and savanna elephants using DNA from low-quality samples. Although mitochondrial DNA is often the marker of choice for species identification, the unusual cytonuclear patterns in African elephants make nuclear markers more reliable. We therefore designed and utilized genetic markers for short nuclear DNA regions that contain fixed nucleotide differences between forest and savanna elephants. We used M13 forward and reverse sequences to increase the total length of PCR amplicons and to improve the quality of sequences for the target DNA. We successfully sequenced fragments of nuclear genes from dung samples of known savanna and forest elephants in the Democratic Republic of Congo, Ethiopia, and Namibia. Elephants at previously unexamined locations were found to have nucleotide character states consistent with their status as savanna or forest elephants. Using these and results from previous studies, we estimated that the short-amplicon nuclear markers could distinguish forest from savanna African elephants with more than 99% accuracy. Nuclear genotyping of museum, dung, or ivory samples will provide better-informed conservation management of Africa's elephants.

  14. Analysis of the pattern of potential woody cover in Texas savanna

    NASA Astrophysics Data System (ADS)

    Yang, Xuebin; Crews, Kelley A.; Yan, Bowei

    2016-10-01

    While woody plant encroachment has been observed worldwide in savannas and adversely affected the ecosystem structure and function, a thorough understanding of the nature of this phenomenon is urgently required for savanna management and restoration. Among others, potential woody cover (the maximum realizable woody cover that a given site can support), especially its variation over environment has huge implication on the encroachment management in particular, and on tree-grass interactions in general. This project was designed to explore the pattern of potential woody cover in Texas savanna, an ecosystem with a large rainfall gradient in west-east direction. Substantial random pixels were sampled across the study area from MODIS Vegetation Continuous Fields (VCF) tree cover layer (250 m). Since potential woody cover is suggested to be limited by water availability, a nonlinear 99th quantile regression was performed between the observed woody cover and mean annual precipitation (MAP) to model the pattern of potential woody cover. Research result suggests a segmented relationship between potential woody cover and MAP at MODIS scale. Potential biases as well as the practical and theoretical implications were discussed. Through this study, the hypothesis about the primary role of water availability in determining savanna woody cover was further confirmed in a relatively understudied US-located savanna.

  15. Seasonality and facilitation drive tree establishment in a semi-arid floodplain savanna.

    PubMed

    Good, Megan K; Clarke, Peter J; Price, Jodi N; Reid, Nick

    2014-05-01

    A popular hypothesis for tree and grass coexistence in savannas is that tree seedlings are limited by competition from grasses. However, competition may be important in favourable climatic conditions when abiotic stress is low, whereas facilitation may be more important under stressful conditions. Seasonal and inter-annual fluctuations in abiotic conditions may alter the outcome of tree-grass interactions in savanna systems and contribute to coexistence. We investigated interactions between coolibah (Eucalyptus coolabah) tree seedlings and perennial C4 grasses in semi-arid savannas in eastern Australia in contrasting seasonal conditions. In glasshouse and field experiments, we measured survival and growth of tree seedlings with different densities of C4 grasses across seasons. In warm glasshouse conditions, where water was not limiting, competition from grasses reduced tree seedling growth but did not affect tree survival. In the field, all tree seedlings died in hot dry summer conditions irrespective of grass or shade cover, whereas in winter, facilitation from grasses significantly increased tree seedling survival by ameliorating heat stress and protecting seedlings from herbivory. We demonstrated that interactions between tree seedlings and perennial grasses vary seasonally, and timing of tree germination may determine the importance of facilitation or competition in structuring savanna vegetation because of fluctuations in abiotic stress. Our finding that trees can grow and survive in a dense C4 grass sward contrasts with the common perception that grass competition limits woody plant recruitment in savannas.

  16. Western equatorial African forest-savanna mosaics: a legacy of late Holocene climatic change?

    NASA Astrophysics Data System (ADS)

    Ngomanda, A.; Chepstow-Lusty, A.; Makaya, M.; Favier, C.; Schevin, P.; Maley, J.; Fontugne, M.; Oslisly, R.; Jolly, D.

    2009-10-01

    Past vegetation and climate changes reconstructed using two pollen records from Lakes Maridor and Nguène, located in the coastal savannas and inland rainforest of Gabon, respectively, provide new insights into the environmental history of western equatorial African rainforests during the last 4500 cal yr BP. These pollen records indicate that the coastal savannas of western equatorial Africa did not exist during the mid-Holocene and instead the region was covered by evergreen rainforests. From ca. 4000 cal yr BP a progressive decline of inland evergreen rainforest, accompanied by the expansion of semi-deciduous rainforest, occurred synchronously with grassland colonisation in the coastal region of Gabon. The contraction of moist evergreen rainforest and the establishment of coastal savannas in Gabon suggest decreasing humidity from ca. 4000 cal yr BP. The marked reduction in evergreen rainforest and subsequent savanna expansion was followed from 2700 cal yr BP by the colonization of secondary forests dominated by the palm, Elaeis guineensis, and the shrub, Alchornea cordifolia (Euphorbiaceae). A return to wetter climatic conditions from about 1400 cal yr BP led to the renewed spread of evergreen rainforest inland, whereas a forest-savanna mosaic still persists in the coastal region. There is no evidence to suggest that the major environmental changes observed were driven by human impact.

  17. Ecological thresholds at the savanna-forest boundary: how plant traits, resources and fire govern the distribution of tropical biomes.

    PubMed

    Hoffmann, William A; Geiger, Erika L; Gotsch, Sybil G; Rossatto, Davi R; Silva, Lucas C R; Lau, On Lee; Haridasan, M; Franco, Augusto C

    2012-07-01

    Fire shapes the distribution of savanna and forest through complex interactions involving climate, resources and species traits. Based on data from central Brazil, we propose that these interactions are governed by two critical thresholds. The fire-resistance threshold is reached when individual trees have accumulated sufficient bark to avoid stem death, whereas the fire-suppression threshold is reached when an ecosystem has sufficient canopy cover to suppress fire by excluding grasses. Surpassing either threshold is dependent upon long fire-free intervals, which are rare in mesic savanna. On high-resource sites, the thresholds are reached quickly, increasing the probability that savanna switches to forest, whereas low-resource sites are likely to remain as savanna even if fire is infrequent. Species traits influence both thresholds; saplings of savanna trees accumulate bark thickness more quickly than forest trees, and are more likely to become fire resistant during fire-free intervals. Forest trees accumulate leaf area more rapidly than savanna trees, thereby accelerating the transition to forest. Thus, multiple factors interact with fire to determine the distribution of savanna and forest by influencing the time needed to reach these thresholds. Future work should decipher multiple environmental controls over the rates of tree growth and canopy closure in savanna.

  18. Variation in woody plant delta(13)C along a topoedaphic gradient in a subtropical savanna parkland.

    PubMed

    Bai, Edith; Boutton, Thomas W; Liu, Feng; Wu, X Ben; Archer, Steven R

    2008-06-01

    delta(13)C values of C(3) plants are indicators of plant carbon-water relations that integrate plant responses to environmental conditions. However, few studies have quantified spatial variation in plant delta(13)C at the landscape scale. We determined variation in leaf delta(13)C, leaf nitrogen per leaf area (N(area)), and specific leaf area (SLA) in April and August 2005 for all individuals of three common woody species within a 308 x 12-m belt transect spanning an upland-lowland topoedaphic gradient in a subtropical savanna in southern Texas. Clay content, available soil moisture, and soil total N were all negatively correlated with elevation. The delta(13)C values of Prosopis glandulosa (deciduous N(2)-fixing tree legume), Condalia hookeri (evergreen shrub), and Zanthoxylum fagara (evergreen shrub) leaves increased 1-4 per thousand with decreasing elevation, with the delta(13)C value of P. glandulosa leaves being 1-3 per thousand higher than those of the two shrub species. Contrary to theory and results from previous studies, delta(13)C values were highest where soil water was most available, suggesting that some other variable was overriding or interacting with water availability. Leaf N(area) was positively correlated with leaf delta(13)C of all species (p < 0.01) and appeared to exert the strongest control over delta(13)C along this topoedaphic gradient. Since leaf N(area) is positively related to photosynthetic capacity, plants with high leaf N(area) are likely to have low p (I)/p (a) ratios and therefore higher delta(13)C values, assuming stomatal conductance is constant. Specific leaf area was not correlated significantly with leaf delta(13)C. Following a progressive growing season drought in July/August, leaf delta(13)C decreased. The lower delta(13)C in August may reflect the accumulation of (13)C-depleted epicuticular leaf wax. We suggest control of leaf delta(13)C along this topoedaphic gradient is mediated by leaf N(area) rather than by stomatal

  19. Groundwater dependent ecohydrology in a semi-arid oak savanna (Invited)

    NASA Astrophysics Data System (ADS)

    Miller, G. R.; Rubin, Y.; Baldocchi, D. D.; Chen, X.; Ma, S.

    2010-12-01

    Groundwater can serve as an important resource for woody vegetation in semi-arid landscapes, particularly when soil water is functionally depleted and unavailable to plants. This study examines the uptake of groundwater by deciduous blue oak trees (Quercus douglasii) in a California oak savanna. Here, we present a suite of direct and indirect measurement techniques, combined with modeling, that demonstrate its occurrence and quantify its rates. The study site is similar to others with shallow-soil ecohydrology: it is underlain by a thin, rocky soil layer followed fractured metavolcanic bedrock. Typical depth to groundwater is approximately 8 m and varies from 7- 10 m, both spatially and temporally. A variety of water storage and flux measurements were collected from 2005 to 2008, including groundwater levels, soil moisture contents, sap flows, and latent heat fluxes. During the dry season, groundwater uptake rates ranged from 4 to 25 mm per month, and approximately 80% of total ET during June, July, and August came from groundwater. Leaf and soil water potentials supported these results, indicating that groundwater uptake was thermodynamically favorable over soil water uptake for key portions of the growing season. Sap flow rates suggest differential access to groundwater by trees of varying size classes. Dynamic groundwater-soil-plant-atmosphere modeling has shown that in order to achieve these uptake rates, approximately 20% of roots must be exposed to groundwater. Modeled evapotranspiration rates drop dramatically during the late summer when this connection is severed (Figure 1). These findings strongly suggest that blue oaks should be considered obligate phreatophytes, and that groundwater reserves provide a buffer to rapid changes in their hydro-climate, if these assets are not otherwise depleted by prolonged drought or human consumption. While groundwater uptake may provide for short-term protection, it should be viewed not as a mechanism for continued plant

  20. Development, survival, and phenotypic plasticity in anthropogenic landscapes: trade-offs between offspring quantity and quality in the nettle-feeding peacock butterfly.

    PubMed

    Serruys, Mélanie; Van Dyck, Hans

    2014-10-01

    Habitats selected for development may have important fitness consequences. This is relevant within the framework of niche shifts in human-dominated landscapes. Currently, the peacock butterfly (Aglais io) occurs ubiquitously, covering many habitat types, whereas its distribution used to be much more restricted. Indeed, its host plant (stinging nettle Urtica dioica) was limited to natural forest gaps on relatively nitrogen-rich soil, but due to land use changes and eutrophication, host plants are now quasi-omnipresent in Western Europe. In order to assess the impact of specific anthropogenic habitat types on host plant quality and environmental conditions for phenotypic trait values, an experiment was conducted in woodlands, field margins, and urban gardens. Larval development was studied in field enclosures, and adult traits were analyzed to test predicted effects of warmer and more nitrogen-rich conditions in field margins compared to woodlands and urban gardens. Survival to the adult stage was highest in woodlands and lowest in field margins, and whilst development time did not differ amongst habitat types, butterflies that developed in field margins were larger and had higher lipid content and wing loadings than conspecifics from woodlands and urban gardens. Nettles in field margins provided warmer microclimates. However, and contrary to predictions, the nitrogen level within host plant leaves was highest in woodlands. Hence, anthropogenic landscapes may pose a conflict for choosing what is ultimately the best breeding habitat, as survival was highest in woodlands (followed by urban gardens), but adults with highest fitness predictions were produced in field margins (and secondarily urban gardens). PMID:25015122

  1. Multidisciplinary modeling and GIS for landscape management

    SciTech Connect

    Flamm, R.O.; Turner, M.G.

    1993-12-31

    Ecological dynamics in human-influenced landscapes are strongly affected by the socioeconomic factors that influence land-use decisions. Incorporating these factors into a spatially-explicit landscape-change model requires the integration of multidisciplinary data. We developed a model that simulates the effects of land use on landscape structure in the Little Tennessee River Basin in western North Carolina. This model uses a variety of data, including interpreted remotely-sensed imagery, census and ownership maps, topography, and results from econometric models. Data are integrated by using a geographic information system and translated into a common format, maps. Simulations generate new maps of land cover representing the amount of land-cover change that occurs. With spatially-explicit projections of landscape change, issues such as biodiversity conservation, the importance of specific landscape elements to conservation goals, and long-term landscape integrity can be addressed. In order for management to use the model to address these issues, a computer-based landscape-management decision aid is being developed. This tool integrates the models, associated data bases, and a geographic information system to facilitate the evaluation of land-use decisions and management plans. This system will estimate landscape-level consequences of alternative actions and will serve to focus coordination among different land-owners and land-use interests in managing the regional landscape.

  2. The relationship between satellite-derived indices and species diversity across African savanna ecosystems

    NASA Astrophysics Data System (ADS)

    Mapfumo, Ratidzo B.; Murwira, Amon; Masocha, Mhosisi; Andriani, R.

    2016-10-01

    The ability to use remotely sensed diversity is important for the management of ecosystems at large spatial extents. However, to achieve this, there is still need to develop robust methods and approaches that enable large-scale mapping of species diversity. In this study, we tested the relationship between species diversity measured in situ with the Normalized Difference Vegetation Index (NDVI) and the Coefficient of Variation in the NDVI (CVNDVI) derived from high and medium spatial resolution satellite data at dry, wet and coastal savanna woodlands. We further tested the effect of logging on NDVI along the transects and between transects as disturbance may be a mechanism driving the patterns observed. Overall, the results of this study suggest that high tree species diversity is associated with low and high NDVI and at intermediate levels is associated with low tree species diversity and NDVI. High tree species diversity is associated with high CVNDVI and vice versa and at intermediate levels is associated with high tree species diversity and CVNDVI.

  3. The effect of carbon credits on savanna land management and priorities for biodiversity conservation.

    PubMed

    Douglass, Lucinda L; Possingham, Hugh P; Carwardine, Josie; Klein, Carissa J; Roxburgh, Stephen H; Russell-Smith, Jeremy; Wilson, Kerrie A

    2011-01-01

    Carbon finance offers the potential to change land management and conservation planning priorities. We develop a novel approach to planning for improved land management to conserve biodiversity while utilizing potential revenue from carbon biosequestration. We apply our approach in northern Australia's tropical savanna, a region of global significance for biodiversity and carbon storage, both of which are threatened by current fire and grazing regimes. Our approach aims to identify priority locations for protecting species and vegetation communities by retaining existing vegetation and managing fire and grazing regimes at a minimum cost. We explore the impact of accounting for potential carbon revenue (using a carbon price of US$14 per tonne of carbon dioxide equivalent) on priority areas for conservation and the impact of explicitly protecting carbon stocks in addition to biodiversity. Our results show that improved management can potentially raise approximately US$5 per hectare per year in carbon revenue and prevent the release of 1-2 billion tonnes of carbon dioxide equivalent over approximately 90 years. This revenue could be used to reduce the costs of improved land management by three quarters or double the number of biodiversity targets achieved and meet carbon storage targets for the same cost. These results are based on generalised cost and carbon data; more comprehensive applications will rely on fine scale, site-specific data and a supportive policy environment. Our research illustrates that the duel objective of conserving biodiversity and reducing the release of greenhouse gases offers important opportunities for cost-effective land management investments.

  4. Savanna domain in the herbivores-fire parameter space exploiting a tree-grass-soil water dynamic model.

    PubMed

    De Michele, C; Accatino, F; Vezzoli, R; Scholes, R J

    2011-11-21

    The tree-grass co-existence in savannas involves multiple and sometimes connected biogeophysical conditions. The savanna domain, its boundaries, and transitions (gradual or abrupt) to other vegetation types (i.e., grassland or forest) are fundamental for the management of ecosystems and for preserving the biodiversity in present conditions and in future changing scenarios. Here we investigate the savanna domain within grazers-fire and browsers-fire parameter planes through a simple ecohydrological model of tree-grass-soil water dynamics. Stability maps allow to identify savanna domains and to show the behavior of vegetation under increasing pressure of grazing and browsing. Stability maps shed light on the causes behind possible vegetation abrupt transitions (e.g., forest collapse and bush encroachment). An application to 15 African savannas sites is presented and discussed with the support of a local sensitivity analysis of the model's parameters. PMID:21875600

  5. Dynamics of Vegetatin Indices in Tropical and Subtropical Savannas Defined by Ecoregions and Moderate Resolution Imaging Spectoradiometer (MODIS) Land Cover

    NASA Technical Reports Server (NTRS)

    Hill, Michael J.; Roman, Miguel O.; Schaaf, Crytal B.

    2011-01-01

    In this study, we explored the capacity of vegetation indices derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) reflectance products to characterize global savannas in Australia, Africa and South America. The savannas were spatially defined and subdivided using the World Wildlife Fund (WWF) global ecoregions and MODIS land cover classes. Average annual profiles of Normalized Difference Vegetation Index, shortwave infrared ratio (SWIR32), White Sky Albedo (WSA) and the Structural Scattering Index (SSI) were created. Metrics derived from average annual profiles of vegetation indices were used to classify savanna ecoregions. The response spaces between vegetation indices were used to examine the potential to derive structural and fractional cover measures. The ecoregions showed distinct temporal profiles and formed groups with similar structural properties, including higher levels of woody vegetation, similar forest savanna mixtures and similar grassland predominance. The potential benefits from the use of combinations of indices to characterize savannas are discussed.

  6. Tree cover bimodality in savannas and forests emerging from the switching between two fire dynamics.

    PubMed

    De Michele, Carlo; Accatino, Francesco

    2014-01-01

    Moist savannas and tropical forests share the same climatic conditions and occur side by side. Experimental evidences show that the tree cover of these ecosystems exhibits a bimodal frequency distribution. This is considered as a proof of savanna-forest bistability, predicted by dynamic vegetation models based on non-linear differential equations. Here, we propose a change of perspective about the bimodality of tree cover distribution. We show, using a simple matrix model of tree dynamics, how the bimodality of tree cover can emerge from the switching between two linear dynamics of trees, one in presence and one in absence of fire, with a feedback between fire and trees. As consequence, we find that the transitions between moist savannas and tropical forests, if sharp, are not necessarily catastrophic.

  7. Seasonal variation in the relative dominance of herbivore guilds in an African savanna.

    PubMed

    Davies, Andrew B; van Rensburg, Berndt J; Robertson, Mark P; Levick, Shaun R; Asner, Gregory P; Parr, Catherine L

    2016-06-01

    African savannas are highly seasonal with a diverse array of both mammalian and invertebrate herbivores, yet herbivory studies have focused almost exclusively on mammals. We conducted a 2-yr exclosure experiment in South Africa's Kruger National Park to measure the relative impact of these two groups of herbivores on grass removal at both highly productive patches (termite mounds) and in the less productive savanna matrix. Invertebrate and mammalian herbivory was greater on termite mounds, but the relative importance of each group changed over time. Mammalian offtake was higher than invertebrates in the dry season, but can be eclipsed by invertebrates during the wet season when this group is more active. Our results demonstrate that invertebrates play a substantial role in savanna herbivory and should not be disregarded in attempts to understand the impacts of herbivory on ecosystems.

  8. Seasonal variation in the relative dominance of herbivore guilds in an African savanna.

    PubMed

    Davies, Andrew B; van Rensburg, Berndt J; Robertson, Mark P; Levick, Shaun R; Asner, Gregory P; Parr, Catherine L

    2016-06-01

    African savannas are highly seasonal with a diverse array of both mammalian and invertebrate herbivores, yet herbivory studies have focused almost exclusively on mammals. We conducted a 2-yr exclosure experiment in South Africa's Kruger National Park to measure the relative impact of these two groups of herbivores on grass removal at both highly productive patches (termite mounds) and in the less productive savanna matrix. Invertebrate and mammalian herbivory was greater on termite mounds, but the relative importance of each group changed over time. Mammalian offtake was higher than invertebrates in the dry season, but can be eclipsed by invertebrates during the wet season when this group is more active. Our results demonstrate that invertebrates play a substantial role in savanna herbivory and should not be disregarded in attempts to understand the impacts of herbivory on ecosystems. PMID:27459791

  9. Remote Sensing Time Series Analysis of Coupled Impacts of Disturbance and Management on Landscape Carbon Storage in the Okavango Delta, Botswana

    NASA Astrophysics Data System (ADS)

    Crews, K.; Neuenschwander, A.

    2007-12-01

    Tropical and subtropical savanna processes are largely impacted by both disturbance and disturbance regimes, notably fire and grazing. In the Okavango Delta, Botswana, savanna-grassland ecotones are also influenced by a third type of disturbance/disturbance regime: flooding. The interspersal of seasonal and occasional wetlands with savanna, grassland, and riparian woodland interfluves culminates in an environment with interacting drivers of landscape change over space and time: fire, flooding, grazing, climatic oscillations, and differential human management practices. The environs of the Okavango are currently subject to four different land management regimes, most of which are now separated by staffed veterinary fences: open or communal lands, photography concessions, hunting concessions, and reserves / national parks. This work utilizes a suite of 85 Landsat TM and ETM+ images from 1989 to 2002 to assess fire magnitude and impact on landscape carbon storage as mitigated by 1) changing and variable rainfall and flooding and 2) the introduction of management zones aimed in part at controlling both proximate and ultimate drivers of fire dynamics and landscape change.

  10. An index of ecological integrity for the Mississippi alluvial plain ecoregion: index development and relations to selected landscape variables

    USGS Publications Warehouse

    Justus, B.G.

    2003-01-01

    Macroinvertebrate community, fish community, water-quality, and habitat data collected from 36 sites in the Mississippi Alluvial Plain Ecoregion during 1996-98 by the U.S. Geological Survey were considered for a multimetric test of ecological integrity. Test metrics were correlated to site scores of a Detrended Correspondence Analysis of the fish community (the biological community that was the most statistically significant for indicating ecological conditions in the ecoregion) and six metrics--four fish metrics, one chemical metric (total ammonia plus organic nitrogen) and one physical metric (turbidity)--having the highest correlations were selected for the index. Index results indicate that sites in the northern half of the study unit (in Arkansas and Missouri) were less degraded than sites in the southern half of the study unit (in Louisiana and Mississippi). Of 148 landscape variables evaluated, the percentage of Holocene deposits and cotton insecticide rates had the highest correlations to index of ecological integrity results. sites having the highest (best) index scores had the lowest percentages of Holocene deposits and the lowest cotton insecticide use rates, indicating that factors relating to the amount of Holocene deposits and cotton insecticide use rates partially explain differences in ecological conditions throughout the Mississippi Alluvial Plain Ecoregion.

  11. Long-term landscape development: a perspective from the southern Buenos Aires ranges of east central Argentina

    NASA Astrophysics Data System (ADS)

    Demoulin, A.; Zarate, M.; Rabassa, J.

    2005-06-01

    Traditionally, the long-term landscape evolution of the southern Buenos Aires ranges of east central Argentina has been related to the influence of the Andean orogeny. We describe the large-scale morphological units and associated weathering products in the Tandilia and Ventania ranges. Two main planation surfaces are encountered at varying altitudes in different sectors of these ranges. The lower surface is characterized by roots of kaolinized weathering profiles in the Tandil area and silicified conglomerates around Sierra de La Ventana. In an interpretative model linking the range morphogenesis to the tectonosedimentary evolution of the bordering Salado and Colorado Basins, we suggest that the main morphogenetic stages are related to the late Jurassic-early Cretaceous south Atlantic rifting and Miocene tectonic reactivation induced by the Andean orogeny. Thus, the uplifted surfaces appear much older than commonly believed: pre-Cretaceous and Paleogene. Although they contradict recent results of apatite fission-track studies along the South America and South Africa passive margins, the implied low denudation rates (˜4 m/My) can be explained by the limited Meso-Cenozoic uplift suffered by the southern Buenos Aires ranges. The discussion also shows the limits of the comparison that can be made with the South African planation surfaces.

  12. Using landscape history to predict biodiversity patterns in fragmented landscapes

    PubMed Central

    Ewers, Robert M; Didham, Raphael K; Pearse, William D; Lefebvre, Véronique; Rosa, Isabel M D; Carreiras, João M B; Lucas, Richard M; Reuman, Daniel C

    2013-01-01

    Landscape ecology plays a vital role in understanding the impacts of land-use change on biodiversity, but it is not a predictive discipline, lacking theoretical models that quantitatively predict biodiversity patterns from first principles. Here, we draw heavily on ideas from phylogenetics to fill this gap, basing our approach on the insight that habitat fragments have a shared history. We develop a landscape ‘terrageny’, which represents the historical spatial separation of habitat fragments in the same way that a phylogeny represents evolutionary divergence among species. Combining a random sampling model with a terrageny generates numerical predictions about the expected proportion of species shared between any two fragments, the locations of locally endemic species, and the number of species that have been driven locally extinct. The model predicts that community similarity declines with terragenetic distance, and that local endemics are more likely to be found in terragenetically distinctive fragments than in large fragments. We derive equations to quantify the variance around predictions, and show that ignoring the spatial structure of fragmented landscapes leads to over-estimates of local extinction rates at the landscape scale. We argue that ignoring the shared history of habitat fragments limits our ability to understand biodiversity changes in human-modified landscapes. PMID:23931035

  13. Juggling carbon: allocation patterns of a dominant tree in a fire-prone savanna.

    PubMed

    Schutz, Alexander Ernest Noel; Bond, William J; Cramer, Michael D

    2009-05-01

    In frequently burnt mesic savannas, trees can get trapped into a cycle of surviving fire-induced stem death (i.e. topkill) by resprouting, only to be topkilled again a year or two later. The ability of savanna saplings to resprout repeatedly after fire is a key component of recent models of tree-grass coexistence in savannas. This study investigated the carbon allocation and biomass partitioning patterns that enable a dominant savanna tree, Acacia karroo, to survive frequent and repeated topkill. Root starch depletion and replenishment, foliage recovery and photosynthesis of burnt and unburnt plants were compared over the first year after a burn. The concentration of starch in the roots of the burnt plants (0.08 +/- 0.01 g g(-1)) was half that of the unburnt plant (0.16 +/- 0.01 g g(-1)) at the end of the first growing season after topkill. However, root starch reserves of the burnt plants were replenished over the dry season and matched that of unburnt plants within 1 year after topkill. The leaf area of resprouting plants recovered to match that of unburnt plants within 4-5 months after topkill. Shoot growth of resprouting plants was restricted to the first few months of the wet season, whereas photosynthetic rates remained high into the dry season, allowing replenishment of root starch reserves. (14)C labeling showed that reserves were initially utilized for shoot growth after topkill. The rapid foliage recovery and the replenishment of reserves within a single year after topkill implies that A. karroo is well adapted to survive recurrent topkill and is poised to take advantage of unusually long fire-free intervals to grow into adults. This paper provides some of the first empirical evidence to explain how savanna trees in frequently burnt savannas are able to withstand frequent burning as juveniles and survive to become adults.

  14. Nutrient dynamics and plant assemblages of Macrotermes falciger mounds in a savanna ecosystem

    NASA Astrophysics Data System (ADS)

    Muvengwi, Justice; Ndagurwa, Hilton G. T.; Nyenda, Tatenda; Mbiba, Monicah

    2016-10-01

    Termites through mound construction and foraging activities contribute significantly to carbon and nutrient fluxes in nutrient-poor savannas. Despite this recognition, studies on the influence of termite mounds on carbon and nitrogen dynamics in sub-tropical savannas are limited. In this regard, we examined soil nutrient concentrations, organic carbon and nitrogen mineralization in incubation experiments in mounds of Macrotermes falciger and surrounding soils of sub-tropical savanna, northeast Zimbabwe. We also addressed whether termite mounds altered the plant community and if effects were similar across functional groups i.e. grasses, forbs or woody plants. Mound soils had significantly higher silt and clay content, pH and concentrations of calcium (Ca), magnesium (Mg), potassium (K), organic carbon (C), ammonium (NH4+) and nitrate (NO3-) than surrounding soils, with marginal differences in phosphorus (P) and sodium (Na) between mounds and matrix soils. Nutrient enrichment increased by a factor ranging from 1.5 for C, 4.9 for Mg up to 10.3 for Ca. Although C mineralization, nitrification and nitrification fraction were similar between mounds and matrix soils, nitrogen mineralization was elevated on mounds relative to surrounding matrix soils. As a result, termite mounds supported unique plant communities rich and abundant in woody species but less diverse in grasses and forbs than the surrounding savanna matrix in response to mound-induced shifts in soil parameters specifically increased clay content, drainage and water availability, nutrient status and base cation (mainly Ca, Mg and Na) concentration. In conclusion, by altering soil properties such as texture, moisture content and nutrient status, termite mounds can alter the structure and composition of sub-tropical savanna plant communities, and these results are consistent with findings in other savanna systems suggesting that increase in soil clay content, nutrient status and associated changes in the plant

  15. Contrasting photosynthetic characteristics of forest vs. savanna species (Far North Queensland, Australia)

    NASA Astrophysics Data System (ADS)

    Bloomfield, K. J.; Domingues, T. F.; Saiz, G.; Bird, M. I.; Crayn, D. M.; Ford, A.; Metcalfe, D. J.; Farquhar, G. D.; Lloyd, J.

    2014-12-01

    Forest and savanna are the two dominant vegetation types of the tropical regions with very few tree species common to both. At a broad scale, it has long been recognised that the distributions of these two biomes are principally governed by precipitation and its seasonality, but with soil physical and chemical properties also potentially important. For tree species drawn from a range of forest and savanna sites in tropical Far North Queensland, Australia, we compared leaf traits of photosynthetic capacity, structure and nutrient concentrations. Area-based photosynthetic capacity was higher for the savanna species with a steeper slope to the photosynthesis ↔ nitrogen (N) relationship compared with the forest group. Higher leaf mass per unit leaf area for the savanna trees derived from denser rather than thicker leaves and did not appear to restrict rates of light-saturated photosynthesis when expressed on either an area or mass basis. Median ratios of foliar N to phosphorus (P) were relatively high (>20) at all sites, but we found no evidence for a dominant P limitation of photosynthesis for either forest or savanna trees. A parsimonious mixed-effects model of area-based photosynthetic capacity retained vegetation type and both N and P as explanatory terms. Resulting model-fitted predictions suggested a good fit to the observed data (R2 = 0.82). The model's random component found variation in area-based photosynthetic response to be much greater among species (71% of response variance) than across sites (9%). These results suggest that, on a leaf-area basis, savanna trees of Far North Queensland, Australia, are capable of photosynthetically outperforming forest species at their common boundaries.

  16. Competition between trees and grasses for both soil water and mineral nitrogen in dry savannas.

    PubMed

    Donzelli, D; De Michele, C; Scholes, R J

    2013-09-01

    The co-existence of trees and grasses in savannas in general can be the result of processes involving competition for resources (e.g. water and nutrients) or differential response to disturbances such as fire, animals and human activities; or a combination of both broad mechanisms. In moist savannas, the tree-grass coexistence is mainly attributed to of disturbances, while in dry savannas, limiting resources are considered the principal mechanism of co-existence. Virtually all theoretical explorations of tree-grass dynamics in dry savannas consider only competition for soil water. Here we investigate whether coexistence could result from a balanced competition for two resources, namely soil water and mineral nitrogen. We introduce a simple dynamical resource-competition model for trees and grasses. We consider two alternative hypotheses: (1) trees are the superior competitors for nitrogen while grasses are superior competitors for water, and (2) vice-versa. We study the model properties under the two hypotheses and test each hypothesis against data from 132 dry savannas in Africa using Kendall's test of independence. We find that Hypothesis 1 gets much more support than Hypothesis 2, and more support than the null hypothesis that neither is operative. We further consider gradients of rainfall and nitrogen availability and find that the Hypothesis 1 model reproduces the observed patterns in nature. We do not consider our results to definitively show that tree-grass coexistence in dry savannas is due to balanced competition for water and nitrogen, but show that this mechanism is a possibility, which cannot be a priori excluded and should thus be considered along with the more traditional explanations.

  17. Sources and sinks of methane in the African savanna. CH sub 4 emissions from biomass burning

    SciTech Connect

    Delmas, R.A.; Marenco, A. ); Tathy, J.P.; Cros, B. ); Baudet, J.G.R. )

    1991-04-20

    Sources and sinks of atmospheric methane are studied in savanna regions of west and central Africa. Flux measured over dry savanna soils, using static chambers, is always negative, the average uptake rate being 2 {times} 10{sup 10} molecules/cm{sup 2}/s. In these regions, sources are linked to biomass burning. Methane and CO{sub 2} emission from combustion of savanna plants and wood is studied by both field experiments and laboratory experiments using a combustion chamber. For savanna plants most of the carbon (85%) contained in the biomaterial is volatilized as CO{sub 2} and 0.1 to 0.25% as methane. For graminaceous plants like loudetia simplex the ratio C-CH{sub 4}/C-CO{sub 2} is 0.11%; it is 0.28% for hyparrhenia the other main type of savanna plants and it attains 1.4% for the combustion of wood. In natural fire plumes this ratio is around 0.26% for savanna fires and 0.56 to 2.22% for forest fires. These results show that methane release is highly dependent on the type of combustion. Methane to CO{sub 2} ratios are also studied in vertical profiles in the troposphere taken during the TROPOZ I campaign, an aerial research expedition carried out over west Africa during the bushfire period. Within polluted layers, the average ratio of CH{sub 4} to CO{sub 2} excess over ambient air concentration is 0.34%. These results show that biomass burning in tropical Africa constitutes an important source of atmospheric methane estimated to about 9.2 {times} 10{sup 6} T (CH{sub 4})/yr.

  18. Emission estimates of selected volatile organic compounds from tropical savanna burning in northern Australia

    NASA Astrophysics Data System (ADS)

    Shirai, T.; Blake, D. R.; Meinardi, S.; Rowland, F. S.; Russell-Smith, J.; Edwards, A.; Kondo, Y.; Koike, M.; Kita, K.; Machida, T.; Takegawa, N.; Nishi, N.; Kawakami, S.; Ogawa, T.

    2003-02-01

    Here we present measurements of a range of carbon-based compounds: carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), nonmethane hydrocarbons (NMHCs), methyl halides, and dimethyl sulfide (DMS) emitted by Australian savanna fires studied as part of the Biomass Burning and Lightning Experiment (BIBLE) phase B aircraft campaign, which took place during the local late dry season (28 August to 13 September 1999). Significant enhancements of short-lived NMHCs were observed in the boundary layer (BL) over the region of intensive fires and indicate recent emissions for which the mean transport time was estimated to be about 9 hours. Emission ratios relative to CO were determined for 20 NMHCs, 3 methyl halides, DMS, and CH4 based on the BL enhancements in the source region. Tight correlations with CO were obtained for most of those compounds, indicating the homogeneity of the local savanna source. The emission ratios were in good agreement with some previous measurements of savanna fires for stable compounds but indicated the decay of emission ratios during transport for several reactive compounds. Based on the observed emission ratios, emission factors were derived and compared to previous studies. While emission factors (g species/kg dry mole) of CO2 varied little according to the vegetation types, those of CO and NMHCs varied significantly. Higher combustion efficiency and a lower emission factor for methane in this study, compared to forest fires, agreed well with results for savanna fires in other tropical regions. The amount of biomass burned was estimated by modeling methods using available satellite data, and showed that 1999 was an above average year for savanna burning. The gross emissions of the trace gases from Australian savanna fires were estimated.

  19. Tree topkill, not mortality, governs the dynamics of savanna-forest boundaries under frequent fire in central Brazil.

    PubMed

    Hoffmann, William A; Adasme, Ryan; Haridasan, M; de Carvalho, Marina T; Geiger, Erika L; Pereira, Mireia A B; Gotsch, Sybil G; Franco, Augusto C

    2009-05-01

    Tropical savanna and forest are recognized to represent alternate stable states, primarily determined by feedbacks with fire. Vegetation-fire dynamics in each of these vegetation types are largely determined by the influence of the vegetation on fire behavior, as well as the effects of fire behavior on tree mortality, topkill (defined here as complete death of the aerial biomass, regardless of whether the plant recovers by resprouting), and rate of growth of resprouts. We studied the effect of fire on three savanna-forest boundaries in central Brazil. Fire intensity was greater in savanna than forest, as inferred by a twofold greater height of stem charring. Despite lower fire intensity, forest tree species exhibited higher rates of topkill, which was best explained by their thinner bark, relative to savanna species. Following topkill, there was no tendency for sprouts of savanna trees to grow faster than those of forest species, contrary to expectations, nor was whole-plant mortality higher in forest than in savanna. This contrasts with observations of high rates of postburn mortality in many other tropical forests. The low tree mortality in these transitional forests suggests that the dynamic of these natural savanna-forest boundaries is fundamentally different from that of forest boundaries originating from deforestation in the humid tropics. The forests studied here appear to be much more resilient to occasional incursion of fire from the savanna, despite being unable to invade frequently burned savanna. The thin bark of forest species makes them particularly susceptible to the "fire trap," whereby repeated topkill of small trees prevents recruitment into adult size classes. Rapid growth will be particularly important for forest species to escape the fire trap, so we predict that, where fire is frequent, forests should be restricted to high-resource sites. Here, Mg2+ and Ca2+ concentrations had particularly strong effects on postburn growth rates, suggesting

  20. Assessing Landscapes to Support Watershed Management

    EPA Science Inventory

    As we change the face of the landscape in the United States with urban development and agriculture practices, the alterations can cause stormwater runoff, soil erosion and water pollution. Therefore, evaluating or assessing natural landscapes and providing the tools to do the...

  1. Oregon Hydrologic Landscapes: A Classification Framework

    EPA Science Inventory

    There is a growing need for hydrologic classification systems that can provide a basis for broad-scale assessments of the hydrologic functions of landscapes and watersheds and their responses to stressors such as climate change. We developed a hydrologic landscape (HL) classifica...

  2. Modelling productivity in a mixed C3 and C4 Australian savanna using a soil-plant-atmosphere model

    NASA Astrophysics Data System (ADS)

    Macinnis-Ng, Cate; Whitley, Rhys; Hutley, Lindsay; Beringer, Jason; Zeppel, Melanie; Williams, Mathew; Medlyn, Belinda; Eamus, Derek

    2010-05-01

    The Soil-Plant-Atmosphere (SPA) model of Williams et al. (1996) is a mechanistic model which simulates ecosystem carbon and water fluxes over multiple canopy and soil layers at fine temporal scale. To-date, this model has not included consideration of C4 vegetation that is typically present in tropical savannas. We added a C4 photosynthesis routine to the model to allow estimation of the gross primary productivity (GPP) of a mixed (C3 and C4) tropical savanna in northern Australia. Much of Australia's savanna consists of a seasonal C4 grass understorey with a C3 open tree canopy, including evergreen, semi-deciduous and deciduous species. The tall annual grasses make up approximately half of the leaf area index (LAI) in the wet season (November to March) when 90% of annual rain falls but they die back in every dry season (April to October). The seasonal cycle of leaf area and foliar N distributions were defined for each canopy layer and each layer was designated as C3 or C4 for application of the applicable photosynthesis model. The SPA model was then run over a 5 year period (2001-2005) and compared to measured eddy covariance data. There was good agreement between modelled and measured GPP values. The model explained between 80 - 87% of the variance and had a low root-mean-square error (RMSE) of between 0.0206 - 0.5742 g C m-2 d-1. The contribution of the grass to total annual GPP was approximately 66%, highlighting the importance of including the C4 grasses in the model. Approximately 60% of the total (trees and grasses) annual GPP occurred during the wet season. Landscape quantum yields were calculated as the response of GPP to PAR between 50 and 250 µmol m-2 s-1 and compared for wet and dry seasons, in both morning and afternoons. This was highest for the wet season mornings (0.0282 mol CO2 per mol photon) and lowest for dry season afternoons. A sensitivity analysis of GPP revealed that daily GPP was most sensitive to changes in understorey LAI and foliar N

  3. Rapid Leaf Deployment Strategies in a Deciduous Savanna

    PubMed Central

    2016-01-01

    Deciduous plants avoid the costs of maintaining leaves in the unfavourable season, but carry the costs of constructing new leaves every year. Deciduousness is therefore expected in ecological situations with pronounced seasonality and low costs of leaf construction. In our study system, a seasonally dry tropical savanna, many trees are deciduous, suggesting that leaf construction costs must be low. Previous studies have, however, shown that nitrogen is limiting in this system, suggesting that leaf construction costs are high. Here we examine this conundrum using a time series of soil moisture availability, leaf phenology and nitrogen distribution in the tree canopy to illustrate how trees resorb nitrogen before leaf abscission and use stored reserves of nitrogen and carbon to construct new leaves at the onset of the growing season. Our results show that trees deployed leaves shortly before and in anticipation of the first rains with its associated pulse of nitrogen mineralisation. Our results also show that trees rapidly constructed a full canopy of leaves within two weeks of the first rains. We detected an increase in leaf nitrogen content that corresponded with the first rains and with the movement of nitrogen to more distal branches, suggesting that stored nitrogen reserves are used to construct leaves. Furthermore the stable carbon isotope ratios (δ13C) of these leaves suggest the use of stored carbon for leaf construction. Our findings suggest that the early deployment of leaves using stored nitrogen and carbon reserves is a strategy that is integrally linked with the onset of the first rains. This strategy may confer a competitive advantage over species that deploy leaves at or after the onset of the rains. PMID:27310398

  4. Rapid Leaf Deployment Strategies in a Deciduous Savanna.

    PubMed

    February, Edmund Carl; Higgins, Steven Ian

    2016-01-01

    Deciduous plants avoid the costs of maintaining leaves in the unfavourable season, but carry the costs of constructing new leaves every year. Deciduousness is therefore expected in ecological situations with pronounced seasonality and low costs of leaf construction. In our study system, a seasonally dry tropical savanna, many trees are deciduous, suggesting that leaf construction costs must be low. Previous studies have, however, shown that nitrogen is limiting in this system, suggesting that leaf construction costs are high. Here we examine this conundrum using a time series of soil moisture availability, leaf phenology and nitrogen distribution in the tree canopy to illustrate how trees resorb nitrogen before leaf abscission and use stored reserves of nitrogen and carbon to construct new leaves at the onset of the growing season. Our results show that trees deployed leaves shortly before and in anticipation of the first rains with its associated pulse of nitrogen mineralisation. Our results also show that trees rapidly constructed a full canopy of leaves within two weeks of the first rains. We detected an increase in leaf nitrogen content that corresponded with the first rains and with the movement of nitrogen to more distal branches, suggesting that stored nitrogen reserves are used to construct leaves. Furthermore the stable carbon isotope ratios (δ13C) of these leaves suggest the use of stored carbon for leaf construction. Our findings suggest that the early deployment of leaves using stored nitrogen and carbon reserves is a strategy that is integrally linked with the onset of the first rains. This strategy may confer a competitive advantage over species that deploy leaves at or after the onset of the rains. PMID:27310398

  5. The ecohydrologic significance of hydraulic redistribution in a semiarid savanna

    NASA Astrophysics Data System (ADS)

    Scott, Russell L.; Cable, William L.; Hultine, Kevin R.

    2008-02-01

    Recent studies have illuminated the process of hydraulic redistribution, defined as the translocation of soil moisture via plant root systems, but the long-term ecohydrologic significance of this process is poorly understood. We investigated hydraulic redistribution (HR) by Prosopis velutina Woot. (velvet mesquite) in an upland savanna ecosystem over a two-year period. Our goal was to quantify patterns of HR by mesquite roots and assess how this affects tree water use and productivity. We used the heat ratio method to monitor bi-directional sap flow, an analog of HR, in both lateral and tap roots. Additionally, we monitored soil water content and used the eddy covariance technique to quantify ecosystem carbon dioxide and water exchange. Mesquite roots redistributed large amounts of water throughout the year, even during periods of canopy dormancy. Dormant season precipitation (November-March) was often taken up by shallow lateral roots and transferred downward in the soil profile by deeper lateral and tap roots. Such a transfer was also apparent when the trees were active and moisture from summer rainfall was plant available in the upper soil layers. As the upper soil layers dried, sap flow moving toward the canopy in the lateral roots diminished and water use from deeper soils increased via the taproots. The relationship between root sap flow and above-canopy fluxes suggested that deeper "stored" water from HR allowed the trees to transpire more in the spring that followed a winter with significant downward redistribution. Patterns of lateral and tap root sap flow also implied that redistribution may extend the growing season of the trees after summer rains have ended and surface soils are dry, thus allowing the trees to photosynthesize through periods of seasonal drought. The large hydrologic magnitude and the ecological effects of HR we studied, along with mounting evidence of this process occurring in many other ecosystems, indicates that HR should be accounted

  6. The development of quick, robust, quantitative phenotypic assays for describing the host–nonhost landscape to stripe rust

    PubMed Central

    Dawson, Andrew M.; Bettgenhaeuser, Jan; Gardiner, Matthew; Green, Phon; Hernández-Pinzón, Inmaculada; Hubbard, Amelia; Moscou, Matthew J.

    2015-01-01

    Nonhost resistance is often conceptualized as a qualitative separation from host resistance. Classification into these two states is generally facile, as they fail to fully describe the range of states that exist in the transition from host to nonhost. This poses a problem when studying pathosystems that cannot be classified as either host or nonhost due to their intermediate status relative to these two extremes. In this study, we investigate the efficacy of the Poaceae-stripe rust (Puccinia striiformis Westend.) interaction for describing the host–nonhost landscape. First, using barley (Hordeum vulgare L.) and Brachypodium distachyon (L.) P. Beauv. We observed that macroscopic symptoms of chlorosis and leaf browning were associated with hyphal colonization by P. striiformis f. sp. tritici, respectively. This prompted us to adapt a protocol for visualizing fungal structures into a phenotypic assay that estimates the percent of leaf colonized. Use of this assay in intermediate host and intermediate nonhost systems found the frequency of infection decreases with evolutionary divergence from the host species. Similarly, we observed that the pathogen’s ability to complete its life cycle decreased faster than its ability to colonize leaf tissue, with no incidence of pustules observed in the intermediate nonhost system and significantly reduced pustule formation in the intermediate host system as compared to the host system, barley-P. striiformis f. sp. hordei. By leveraging the stripe rust pathosystem in conjunction with macroscopic and microscopic phenotypic assays, we now hope to dissect the genetic architecture of intermediate host and intermediate nonhost resistance using structured populations in barley and B. distachyon. PMID:26579142

  7. Satellite-based automated burned area detection: A performance assessment of the MODIS MCD45A1 in the Brazilian savanna

    NASA Astrophysics Data System (ADS)

    Araújo, Fernando Moreira De; Ferreira, Laerte G.

    2015-04-01

    Burnings, which cause major changes to the environment, can be effectively monitored via satellite data, regarding both the identification of active fires and the estimation of burned areas. Among the many orbital sensors suitable for mapping burned areas on global and regional scales, the moderate resolution imaging spectroradiometer (MODIS), on board the Terra and Aqua platforms, has been the most widely utilized. In this study, the performance of the MODIS MCD45A1 burned area product was thoroughly evaluated in the Brazilian savanna, the second largest biome in South America and a global biodiversity hotspot, characterized by a conspicuous climatic seasonality and the systematic occurrence of natural and anthropogenic fires. Overall, September MCD45A1 polygons (2000-2012) compared well to the Landsat-based reference mapping (r2 = 0.92) and were closely accompanied, on a monthly basis, by MOD14 and MYD14 hotspots (r2 = 0.89), although large omissions errors, linked to landscape patterns, structures, and overall conditions depicted in each reference image, were observed. In spite of its spatial and temporal limitations, the MCD45A1 product proved instrumental for mapping and understanding fire behavior and impacts on the Cerrado landscapes.

  8. SAVANNAH RIVER BASIN LANDSCAPE ANALYSIS

    EPA Science Inventory

    Scientists from the U.S. Environmental Protection Agency (EPA), Region 4, Science and Ecosystem Support Division, enlisted the assistance of the landscape ecology group of U.S. EPA, Office of Research and Development (ORD), National Exposure Research Laboratory, Environmental Sci...

  9. INTEGRATING A LANDSCAPE HYDROLOGIC ANALYSIS FOR WATERSHED ASSESSMENT

    EPA Science Inventory

    Methods to provide linkages between a hydrologic modeling tool (AGW A) and landscape assessment tool (A TtILA) for determining the vulnerability of semi-arid landscapes to natural and human-induced landscape pattern changes have been developed. The objective of this study is to ...

  10. Units of Instruction in Landscape and Nursery Management.

    ERIC Educational Resources Information Center

    Iowa State Univ. of Science and Technology, Ames. Dept. of Agricultural Education.

    This set of teacher-developed instructional units is intended for use in secondary-level vocational agriculture courses dealing with landscape and nursery management courses. The following topics are covered in the individual units: identification of landscape plants, selection of landscape plants, understanding soils and fertilizers, water…

  11. Landscapes Impacted by Light

    NASA Astrophysics Data System (ADS)

    Arellano, B.; Roca, J.

    2016-06-01

    The gradual spread of urbanization, the phenomenon known under the term urban sprawl, has become one of the paradigms that have characterized the urban development since the second half of the twentieth century and early twenty-first century. However, there is no unanimous consensus about what means "urbanization". The plurality of forms of human settlement on the planet difficult to identify the urbanization processes. The arrival of electrification to nearly every corner of the planet is certainly the first and more meaningful indicator of artificialization of land. In this sense, the paper proposes a new methodology based on the analysis of the satellite image of nighttime lights designed to identify the highly impacted landscapes worldwide and to build an index of Land Impacted by Light per capita (LILpc) as an indicator of the level of urbanization. The used methodology allows the identification of different typologies of urbanized areas (villages, cities or metropolitan areas), as well as "rural", "rurban", "periurban" and "central" landscapes. The study identifies 186,134 illuminated contours (urbanized areas). In one hand, 404 of these contours could be consider as real "metropolitan areas"; and in the other hand, there are 161,821 contours with less than 5,000 inhabitants, which could be identify as "villages". Finally, the paper shows that 44.5 % live in rural areas, 15.5 % in rurban spaces, 26.2 % in suburban areas and only 18.4 % in central areas.

  12. Cydonia Landscape

    NASA Technical Reports Server (NTRS)

    2002-01-01

    [figure removed for brevity, see original site]

    The Cydonia region on Mars straddles the boundary between the bright, dusty, cratered highlands to the southeast and the dark, relatively dust-free, lowland plains to the west. The countless mesas and buttes that cover the region are testament to the former presence of vast layers of material that have been stripped back over the eons leaving the isolated remnants seen in this THEMIS image. Evidence of larger masses of these remnants is visible to the south in the MOLA context image. Note the lobes of ejecta emanating from the large crater in the upper right of the THEMIS image. This style of ejecta is thought to arise when an impact occurs into water or ice-rich material, indicating that at least at the time of the impact such material was present.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  13. Effects of Precommercial Thinning and Midstory Control on Avian and Small Mammal Communities during Longleaf Pine Savanna Restoration.

    SciTech Connect

    Lane, Vanessa R; Kilgo, John C

    2015-01-01

    Abstract - Restoring longleaf pine (Pinus palustris Mill.) savanna is a goal of many southern land managers, and longleaf plantations may provide a mechanism for savanna restoration. However, the effects of silvicultural treatments used in the management of longleaf pine plantations on wildlife communities are relatively unknown. Beginning in 1994, we examined effects of longleaf pine restoration with plantation silviculture on avian and small mammal communities using four treatments in four 8- to 11- year-old plantations within the Savannah River Site in South Carolina. Treatments included prescribed burning every 3 to 5 years, plus: (1) no additional treatment (burn-only control); (2) precommercial thinning; (3) non-pine woody control with herbicides; and (4) combined thinning and woody control. We surveyed birds (1996-2003) using 50-m point counts and small mammals with removal trapping. Thinning and woody control alone had short-lived effects on avian communities, and the combination treatment increased avian parameters over the burn-only control in all years. Small mammal abundance showed similar trends as avian abundance for all three treatments when compared with the burn-only control, but only for 2 years post-treatment. Both avian and small mammal communities were temporarily enhanced by controlling woody vegetation with chemicals in addition to prescribed fire and thinning. Therefore, precommercial thinning in longleaf plantations, particularly when combined with woody control and prescribed fire, may benefit early-successional avian and small mammal communities by developing stand conditions more typical of natural longleaf stands maintained by periodic fire.

  14. Fire controls population structure in four dominant tree species in a tropical savanna.

    PubMed

    Lehmann, Caroline E R; Prior, Lynda D; Bowman, David M J S

    2009-09-01

    The persistence of mesic savannas has been theorised as being dependent on disturbances that restrict the number of juveniles growing through the sapling size class to become fire-tolerant trees. We analysed the population structures of four dominant tropical savanna tree species from 30 locations in Kakadu National Park (KNP), northern Australia. We found that across KNP as a whole, the population size structures of these species do not exhibit recruitment bottlenecks. However, individual stands had multimodal size-class distributions and mixtures of tree species consistent with episodic and individualistic recruitment of co-occurring tree species. Using information theory and multimodel inference, we examined the relative importance of fire frequency, stand basal area and elevation difference between a site and permanent water in explaining variations in the proportion of sapling to adult stems in four dominant tree species. This showed that the proportion of the tree population made up of saplings was negatively related to both fire frequencies and stand basal area. Overall, fire frequency has density-dependent effects in the regulation of the transition of saplings to trees in this Australian savanna, due to interactions with stem size, regeneration strategies, growth rates and tree-tree competition. Although stable at the regional scale, the spatiotemporal variability of fire can result in structural and floristic diversity of savanna tree populations. PMID:19629532

  15. Are cattle surrogate wildlife? Savanna plant community composition explained by total herbivory, not herbivore identity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The replacement of wild ungulate herbivores by domestic livestock in African savannas is composed of two interrelated phenomena: 1) loss or reduction in numbers of individual wildlife species or guilds, and 2) addition of livestock to the system. Yet very few studies have addressed the individual, c...

  16. Direct measurements of the seasonality of emission factors from savanna fires in northern Australia

    NASA Astrophysics Data System (ADS)

    Meyer, C. P.; Cook, G. D.; Reisen, F.; Smith, T. E. L.; Tattaris, M.; Russell-Smith, J.; Maier, S. W.; Yates, C. P.; Wooster, M. J.

    2012-10-01

    Current good practice guidelines for national greenhouse gas inventories requires that seasonal variation in emission factors from savanna fires be considered when compiling national accounts. African studies concluded that the emission factor for methane decreases during the dry season principally due to curing of the fuels. However, available data from Australian tropical savannas shows no effect of seasonality on emission factors, consistent with observations that the fine fuels appear to cure fully soon after the start of the fire season. To test whether the seasonality in greenhouse gas emission factors reported for Africa also occurs in Australia, methane and nitrous oxide emission factors were measured in early and in late dry season fires in Western Arnhem Land, a region typical of much of the northern Australia savanna zone. We found no significant seasonality in methane emission factors, but there was substantial variation in emission factors associated with inter-fire differences in vegetation and fuel. This variation could be explained almost completely by combustion efficiency. Nitrous oxide emission factors were not related to combustion efficiency but showed some variation across vegetation and fuel size class. Both methane and nitrous oxide emission factors were consistent with previous work in northern Australia and with some published values from Africa. The absence of a significant seasonal trend in emission factors indicates that savanna fire emissions in northern Australia can be managed by strategic prescribed burning.

  17. SEASONAL SOIL FLUXES OF CARBON MONOXIDE IN BURNED AND UNBURNED BRAZILIAN SAVANNAS

    EPA Science Inventory

    Soil-atmosphere fluxes of carbon monoxide (CO) were measured from September 1999 through November 2000 in savanna areas in central Brazil (Cerrado) under different fire regimes using transparent and opaque static chambers. Studies focused on two vegetation types, cerrado stricto...

  18. RELATIONSHIP OF MICROBIAL COMMUNITY STRUCTURE AND CARBON DYNAMICS IN SOILS FROM BRAZILIAN SAVANNAS

    EPA Science Inventory

    Fertilization is a widespread management practice in savanna areas of central Brazil (Cerrado) that are undergoing rapid agricultural land use changes. We conducted field and laboratory studies in soils with added fertilizers to determine the effect that fertilization of native a...

  19. Sustainable Land Management and Adult Education: Issues for the Stakeholders of Australia's Tropical Savannas.

    ERIC Educational Resources Information Center

    Benson, Rebecca

    1998-01-01

    Sustainable land management is an important consideration for stakeholders in Australia's tropical savannas. Land-management-education providers must deal with issues of access and the impact of values and perceptions on behavior. Adult educators must take on the role of negotiating attitudes and beliefs among stakeholders. (SK)

  20. Ecology and management of savannas and semi-deserts of central Argentina

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vegetation of western pampas of central Argentina comprises: caldera, local name of a savanna to woodland ecosystem dominated by Prosopis caldenia; short-grassland and dune-grassland. The area include the central La Pampa and southern San Luis provinces, following a western precipitation gradient fr...

  1. STRUCTURE OF MICROBIAL COMMUNITIES IN NATIVE AND CONVERTED SAVANNA AREAS OF CENTRAL BRAZIL

    EPA Science Inventory

    Brazilian savannas (Cerrado) have suffered drastic changes in land use with major conversion of native areas to agriculture since 1960. Burning, both due to natural conditions and as a human-induced practice, is a common event during the dry season (April to September) and plays ...

  2. Fire controls population structure in four dominant tree species in a tropical savanna.

    PubMed

    Lehmann, Caroline E R; Prior, Lynda D; Bowman, David M J S

    2009-09-01

    The persistence of mesic savannas has been theorised as being dependent on disturbances that restrict the number of juveniles growing through the sapling size class to become fire-tolerant trees. We analysed the population structures of four dominant tropical savanna tree species from 30 locations in Kakadu National Park (KNP), northern Australia. We found that across KNP as a whole, the population size structures of these species do not exhibit recruitment bottlenecks. However, individual stands had multimodal size-class distributions and mixtures of tree species consistent with episodic and individualistic recruitment of co-occurring tree species. Using information theory and multimodel inference, we examined the relative importance of fire frequency, stand basal area and elevation difference between a site and permanent water in explaining variations in the proportion of sapling to adult stems in four dominant tree species. This showed that the proportion of the tree population made up of saplings was negatively related to both fire frequencies and stand basal area. Overall, fire frequency has density-dependent effects in the regulation of the transition of saplings to trees in this Australian savanna, due to interactions with stem size, regeneration strategies, growth rates and tree-tree competition. Although stable at the regional scale, the spatiotemporal variability of fire can result in structural and floristic diversity of savanna tree populations.

  3. Western equatorial African forest-savanna mosaics: a legacy of late Holocene climatic change?

    NASA Astrophysics Data System (ADS)

    Ngomanda, A.; Chepstow-Lusty, A.; Makaya, M.; Favier, C.; Schevin, P.; Maley, J.; Fontugne, M.; Oslisly, R.; Jolly, D.

    2009-02-01

    Past vegetation and climate changes reconstructed using two pollen records from Lakes Maridor and Nguène, Gabon, provide new insights into the environmental history of western equatorial African rainforests during the last 4500 cal yr BP. The Lake Maridor pollen record indicates that the coastal savannas of western equatorial Africa did not exist during the mid-Holocene and instead the region was covered by evergreen rainforests. In the Lake Nguène pollen record, a rapid decline of hygrophilous evergreen rainforest occurred around 4000 cal yr BP, synchronously with grassland expansion around Lake Maridor. The establishment of coastal savannas in Gabon suggests decreasing humidity at the onset of the late Holocene. The marked reduction in evergreen rainforest and subsequent savanna expansion was associated with the colonization of secondary forests dominated by the palm, Elaeis guineensis, in the coastal region and the shrub, Alchornea cordifolia, further inland. A return to wetter climatic conditions from about 1400 cal yr BP led to the renewed spread of evergreen rainforest inland, whereas a forest-savanna mosaic still persists in the coastal region. There is no evidence to suggest that the major environmental changes observed are driven by human impact.

  4. Methane sources and sinks in a periodically flooded South African savanna

    NASA Astrophysics Data System (ADS)

    Otter, Luanne B.; Scholes, Mary C.

    2000-03-01

    Methane (CH4) fluxes were measured over a 2-year period at subtropical savanna and floodplain sites located in South Africa. No significant differences were detected in fluxes from the nutrient-rich and nutrient-poor savannas. Savannas were not always sinks and showed some CH4 emissions during the wet, summer season with fluxes in the range of -1.6 to 1.68 mg m-2 d-1. Soil temperature did not have a significant effect on the flux, while CH4 consumption decreased and emissions increased with an increase in soil moisture between 5% and 50% water-filled-pore-space (WFPS). Understanding the factors which control the production and emission of CH4 in aerobic environments is extremely important for predicting net emissions from a region. Dry floodplain soil fluxes were near zero and did not differ significantly from savanna fluxes. During a flood, saturated sites emitted CH4 at an average rate of 69.4 mg m-2 d-1. Flooded areas with a water depth of 0.3 - 0.4 m emitted CH4 from the water surface at rates between 0.48 and 466.3 mg m-2 d-1 with the highest emission occurring during summer. Emission rates were exponentially related to sediment temperature, which had a greater influence on the emission rate than the flood regime. The length of the dry period preceding the flood and the extent of a flood did not have a significant effect on CH4 fluxes from saturated and flooded sites. Emission rates were highest when the water level was between 0.1 m below the soil surface and 0.4 m above the soil surface, with emission rates declining to near zero as the water became deeper than 0.4 m. Savannas were estimated to consume an average of 0.04 g CH4 m-2 d-1, with southern African savannas consuming 0.23 Tg CH4 yr-1. Saturated and flooded sites were estimated to produce 25.3 and 57.2 g CH4 m-2 d-1, respectively. Southern African floodplains are estimated to produce between 0.2 and 10 Tg CH4 yr-1(excluding the effects of vegetation-mediated emissions) and therefore produce more CH4

  5. Longwave infrared observation of urban landscapes

    NASA Technical Reports Server (NTRS)

    Goward, S. N.

    1981-01-01

    An investigation is conducted regarding the feasibility to develop improved methods for the identification and analysis of urban landscapes on the basis of a utilization of longwave infrared observations. Attention is given to landscape thermal behavior, urban thermal properties, modeled thermal behavior of pavements and buildings, and observed urban landscape thermal emissions. The differential thermal behavior of buildings, pavements, and natural areas within urban landscapes is found to suggest that integrated multispectral solar radiant reflectance and terrestrial radiant emissions data will significantly increase potentials for analyzing urban landscapes. In particular, daytime satellite observations of the considered type should permit better identification of urban areas and an analysis of the density of buildings and pavements within urban areas. This capability should enhance the utility of satellite remote sensor data in urban applications.

  6. Nitrogen Dynamics of the Savanna Flux Site at Skukuza, Kruger National Park.

    NASA Astrophysics Data System (ADS)

    Woghiren, A. J.; Scholes, M.

    2001-12-01

    The SAFARI 2000 campaign aims at validating satellite-based estimates of photosynthesis and net primary productivity (NPP). The Skukuza site has two vegetation types, a Combretum (broad-leafed) savanna and an Acacia (fine-leafed) savanna. Since it is expected that these two vegetation types may have markedly different responses to global climate change, it is an ideal site for the Earth observing systems (EOS) validation experiment. NPP estimates need to be explained and supported using corresponding data on the N (nitrogen) budgets for the site. Plants capable of nitrogen fixation usually had higher % N and lower \\delta15N signatures than their non-nitrogen-fixing counterparts. Most species had isotopically enriched signatures relative to the standard, which was air. The mean enrichments for the legumes varied from -1.76 to 3.32%, while that of the non-legumes ranged from 3.02 to 7.08%. In the herbaceous layer, Stylosanthes fruticosa and Macrotyloma maranguense had the highest fixation rates, with 84% and 41% being contributed by each species respectively (4.9 - 6.8 kg N ha-1 yr-1 is fixed in this layer). Since these species occurred in dense patches at the broad-leafed site, it was assumed that this was the contribution of N2 fixation to this savanna. The dominant N2 fixing tree was Acacia nilotica, with 50 % of its N being fixed. Trees at the fine-leafed site fixed between 2.9 - 5.5 kg N ha-1 yr-1, while herbaceous legumes contributed 4.9 - 6.8 kg N ha-1 yr-1. Nitrogen mineralisation is seasonal, with particularly high rates of mineralisation in spring. In winter, NH4+ dominates at the fine-leafed site, when it is scarcely detectable at the broad-leafed site. On the other hand, nitrate prevails in summer at the fine-leafed site, while it is being immobilised at the broad-leafed site. In contrast to another South African savanna, NH4+ is detected in large quantities (0.85 μ g N g-1 dry soil day-1) at both sites during summer. The nitrification rates are

  7. (U-Th)/He Age Elevation Profiles from the Adamello Batholith (Southern Alps, Italy): Possible Insights into the Miocene Landscape Development of the European Alps

    NASA Astrophysics Data System (ADS)

    Reverman, R.

    2009-12-01

    Alpine landscapes are developed through the complex interplay between tectonics and climate. However, the nature of this interplay is still poorly understood. Age elevation profiles, especially those for low temperature thermochronometers, provide high resolution near surface exhumation rates. These rates can be used to constrain the rate of surface relief development in response to climatic and/or tectonic events. In this study we present the first apatite (U-TH) /He ages for two vertical profiles from the Adamello batholith (Southern Alps, Italy). These initial ages span the Miocene and suggest at least two periods of accelerated cooling. The Adamello batholith is the largest of the Tertiary intrusions along the Insubric line in the European Alps and is bound by two major faults, the Tonale line and the Giudicarie line. Major river systems within the massif drain south to the Po Plain. This makes it an ideal location to determine the role and magnitude of known tectonic events (Giudicarie phase shortening in the Tortonian) and climatic events (Messinian Salinity crisis and Neogene glaciation) in the recent development of alpine relief. Further work will include 4He/3He analysis, zircon (U-Th)/He dating and apatite fission-track analysis.

  8. Are the eucalypt and non-eucalypt components of Australian tropical savannas independent?

    PubMed

    Lawes, M J; Murphy, B P; Midgley, J J; Russell-Smith, J

    2011-05-01

    Eucalypts (Eucalyptus and Corymbia spp.) dominate (>60%) the tree biomass of Australia's tropical savannas but account for only a fraction (28%) of the tree diversity. Because of their considerable biomass and adaptation to environmental stressors, such as fire, the eucalypts may drive tree dynamics in these savannas, possibly to the exclusion of non-eucalypts. We evaluated whether the eucalypt and non-eucalypt components in tropical savannas are dependent so that changes in one component are matched by opposite trends in the other. Using tree inventory data from 127 savanna sites across the rainfall and fire frequency gradients, we found that eucalypt and non-eucalypt basal area and species richness had a negative relationship. This relationship was maintained across the rainfall gradient, with rainfall having a positive effect on the basal area and species richness of both components, but with a greater effect in non-eucalypts. Fire frequency negatively affected basal area, but not species richness, although basal area and species richness of eucalypts and non-eucalypts did not differ in their response to fire. Rainfall appears to set the upper bounds to woody biomass in these mesic savannas, while fire maintains woody biomass below carrying capacity and facilitates coexistence of the components. The magnitude of the component responses, particularly for non-eucalypts, is determined by rainfall, but their dependence is likely due to their differential response to both rainfall and fire, but not to competition for resources. Thus, while eucalypts dominate biomass overall, at high rainfall sites non-eucalypt basal area and diversity are highest, especially where fire frequency is low.

  9. Contrasting photosynthetic characteristics of forest vs.