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Sample records for california grassland experiment

  1. Variation in soil moisture and N availability modulates carbon and water exchange in a California grassland experiment

    SciTech Connect

    St. Clair, S.B.; Sudderth, E.; Fischer, M.L.; Torn, M.S.; Stuart, S.; Salve, R.; Eggett, D.; Ackerly, D.

    2009-03-15

    Variability in the magnitude and timing of precipitation is predicted to change under future climate scenarios. The primary objective of this study was to understand how variation in precipitation patterns consisting of soil moisture pulses mixed with intermittent dry down events influence ecosystem gas fluxes. We characterized the effects of precipitation amount and timing, N availability, and plant community composition on whole ecosystem and leaf gas exchange in a California annual grassland mesocosm study system that allowed precise control of soil moisture conditions. Ecosystem CO2 and fluxes increased significantly with greater precipitation and were positively correlated with soil moisture. A repeated 10 day dry down period following 11 days of variable precipitation inputs strongly depressed net ecosystem CO2 exchange (NEE) across a range of season precipitation totals, and plant community types. Ecosystem respiration (Re), evapotranspiration (ET) and leaf level photosynthesis (Amax) showed greatest sensitivity to dry down periods in low precipitation plots. Nitrogen additions significantly increased NEE, Re and Amax, particularly as water availability was increased. These results demonstrate that N availability and intermittent periods of soil moisture deficit (across a wide range of cumulative season precipitation totals) strongly modulate ecosystem gas exchange.

  2. Selenium contamination of the Grasslands, a major California waterfowl area.

    PubMed

    Ohlendorf, H M; Hothem, R L; Aldrich, T W; Krynitsky, A J

    1987-10-01

    In a recent study at Kesterson Reservoir in California, selenium was shown to cause mortality and deformities in embryos of aquatic birds. The present study was conducted to determine if selenium or other contaminants in agricultural drainwater used for marsh management were likely to cause similar adverse effects in the nearby Grasslands area. Selenium concentrations were elevated (greater than 15 ppm, dry-weight) in livers of some birds of all species collected from the Grasslands. Mean selenium concentrations in all species sampled in the South Grasslands were significantly higher (P less than 0.05) than those from the "control site", the Volta Wildlife Area. Mean selenium levels in black-necked stilts (Himantopus mexicanus) from the South Grasslands (35.6 ppm) were similar (P greater than 0.05) to levels in stilts from Kesterson (46.4 ppm), but means for American avocets (Recurvirostra americana) from the South Grasslands (67.3 ppm) were higher (P less than 0.05) than those from Kesterson (28.4 ppm). Bird eggs and fish from the Grasslands also contained elevated levels of selenium. Concentrations of eight heavy metals in fish generally reflected those patterns previously found in water entering the study areas. Of the organochlorines detected in fish, only DDE occurred at concentrations potentially harmful to birds (6.1 and 3.0 ppm, wet weight, at two South Grassland sites). The effect on avian health or reproduction of the other contaminants, singly or in combination, could not be determined. However, selenium levels were apparently sufficiently elevated in 1984 to have caused adverse effects on avian reproduction in the South Grasslands. PMID:3685947

  3. Fire And Dynamics Of Granivory On A California Grasslands Forb

    SciTech Connect

    Espeland, E; Carlsen, T; Macqueen, D

    2003-10-02

    This study examines the effects of burning and granivory on the reproductive success of the rare plant Amsinckia grandiflora (Boraginaceae). Fire is often used in California grasslands as a means of exotic species control, but the indirect effects of these controls on the reproductive ecology of a native plants are rarely assessed. The interaction of fire with granivory of A. grandiflora seeds was examined in California grasslands over five years (1998-2002). In 1998 and 1999, both burned and unburned plots had bird-exclusion (netted) and no-exclusion (open) treatments. Predation rates were high (51-99%) and final predation rates did not differ among treatments. In 2000, granivory rates in the unburned, open plots were lower than in previous years (14%), and rodent trapping yielded only a single animal. Low granivory rates were observed in 2001 for unburned, open plots (47%). In 2001, burned/open plots experienced significantly more granivory (87%) than either burned/netted plots (37%) or unburned/open plots (47%). In 2002, every seed was taken from burned, open plots. Granivory was highly variable, ranging from 4% to 100% per plot over a three-week period. Nearly all plots were discovered (>10% predation) by granivores in all trials in all years. When data from all treatments were combined, significant differences in granivory rates occurred among years, indicating stronger inter-year effects than within-year effects due to burning or bird exclusion. Fire affects granivory when overall predation rates are low, but when predation levels are high (as they were in 1998 and 1999), fire may not affect granivory occurring within the same year. Models extending seed survivorship through the dry summer indicate that most seeds are eaten, even when granivory rates are low.

  4. Ecosystem Change in California Grasslands: Impacts of Species Invasion

    NASA Astrophysics Data System (ADS)

    Koteen, L. E.; Harte, J.; Baldocchi, D. D.

    2009-12-01

    Grassland ecosystems of California have undergone dramatic changes, resulting in the almost complete replacement of native perennial grasses by non-native annuals across millions of hectares of grassland habitat. Our research investigates the effects of this community shift on carbon, water and energy cycles at two sites in northern coastal California. Our goal was to understand how changes to California’s grasslands have affected climate through 1. shifting the balance of carbon storage between terrestrial stocks and the atmosphere, and 2. altering the water and energy regimes that heat or cool the earth's surface. To compare the processes that govern material exchange before and after annual grass invasion, we made use of sites where native vegetation is found adjacent to locations that have undergone non-native invasion. In plots of each vegetation type, we monitored whole plant productivity, root and litter decay rates and soil respiration, as well as soil climatic controls on these processes. At one site, we also measured surface albedo and the components of the surface energy balance in each grass community, using the surface renewal method. Although seemingly subtle, the shift in California grassland communities from native perennial to non-native annual grass dominance has had profound consequences for ecosystem biogeochemical, radiative and hydrological cycles. Soil carbon storage was found to be significantly greater in native perennial grass communities. Across both study sites, we found that non-native grass invasion has resulted in the transfer of from 3 to 6 tons of carbon per hectare from the soil to the atmosphere, dependent on site and species. A soil density fractionation and a radiocarbon analysis also revealed the carbon to be more recalcitrant in native grass dominated locations. The primary plant traits that help explain why soil carbon losses follow annual grass invasion are: 1. differences between annual and perennial grasses in above

  5. Estimating Critical Nitrogen Loads for a California Grassland

    NASA Astrophysics Data System (ADS)

    Weiss, S. B.

    2007-12-01

    Rigorously established critical nitrogen loads to protect biodiversity can be effective policy tools for addressing the insidious impacts of atmospheric N-deposition on ecosystems. This presentation describes methods for determining critical N-loads to a California grassland ecosystem by careful examination of the continuum from emissions, transport, atmospheric chemistry, deposition, ecosystem response, and impacts on biodiversity. Nutrient-poor soils derived from serpentinite bedrock support diverse native grasslands with dazzling wildflower displays and numerous threatened and endangered species, including the Bay checkerspot butterfly. Under moderate atmospheric N-deposition, these sites are rapidly invaded by introduced nitrophilous annual grasses in the absence of appropriate grazing or other management. Critical loads to this ecosystem have been approached by measurements of atmospheric concentrations of reactive N gases using Ogawa passive samplers and seasonally averaged deposition velocities. A regional-scale pollution gradient was complemented by a very local-scale pollution gradient extending a few hundred meters downwind of a heavily traveled road in a relatively unpolluted area. The local gradient suggests a critical load of 5 kg-N ha-1 a-1 or less. The passive monitor calculations largely agree with deposition calculated with the CMAQ model at 4 km scale. Emissions of NH3 from catalytic converters are the dominant N-source at the roadway site, and are a function of traffic volume and speed. Plant tissue N-content and 15N gradients support the existence of N-deposition gradients. The complexities of more detailed calculations and measurements specific to this ecosystem include seasonal changes in LAI, temporal coincidence of traffic emissions and stomatal conductance, surface moisture, changes in oxidized versus reduced N sources, and annual weather variation. The concept of a "critical cumulative load" may be appropriate over decadal time scales in

  6. Quantification of Microbial Osmolytes in a Drought Impacted California Grassland

    NASA Astrophysics Data System (ADS)

    Boot, C. M.; Schaeffer, S. M.; Doyle, A. P.; Schimel, J. P.

    2008-12-01

    With drought frequency and severity likely increasing in the future, understanding its effect on terrestrial carbon (C) and nitrogen (N) cycling has become essential for accurately modeling ecosystem responses to climate change. Microbes respond to drought stress by accumulating internal solutes, or osmolytes, such as amino acids, betaines and polyols, to balance cell membrane water potential as the soil dries. However, when seasonal rains arrive, internal solutes are released and rapidly mineralized. We have been studying these processes in a California grassland. Beginning in summer 2007, we made monthly measurements of soil moisture, individual amino acid concentration in total soil and in microbial biomass, total dissolved organic carbon and nitrogen (DOC and DON), and microbial biomass carbon and nitrogen (MBC and MBN). We expected microbial concentrations of the known amino acid osmolytes glutamate (glu) and proline (pro) to fluctuate inversely with soil moisture. However, pro was only recovered in Mar 2008 (0.30 μg C g-1 dry soil) and the glu concentration varied proportionally with soil moisture: lowest during summer (0.06 g H2O g-1 dry soil, 2.22 μg glutamate-C g-1 dry soil) and highest in winter (0.27 g H2O g-1 dry soil, 4.43 μg glutamate-C g-1 dry soil). The trend from DOC, MBC, and DON measurements was opposite, however, with all concentrations decreasing as soil moisture shifted from dry to wet, (DOC: 64.61 to 32.49 μg C g-1 dry soil respectively). MBN was the exception to this trend, with concentrations staying nearly constant across seasons. These patterns suggest that the expected amino acids glu and pro are not being used for microbial osmoregulation in the CA grassland, and given the summer to winter decrease in MBC, the primary osmolyte source is likely to be either polyol-type compounds such as mannitol or betaines. The implications for terrestrial carbon cycle are considerable because as the frequency of drought increases, the accumulation

  7. Fertilization effects on the ecohydrology of a southern California annual grassland

    NASA Astrophysics Data System (ADS)

    Parolari, A. J.; Goulden, M. L.; Bras, R. L.

    2012-04-01

    Nitrogen limits leaf gas exchange, canopy development, and evapotranspiration in many ecosystems. In dryland ecosystems, it is unclear whether increased anthropogenic nitrogen inputs alter the widely recognized dominance of water and energy constraints on ecohydrology. We use observations from a factorial irrigation and fertilization experiment in a nitrogen-limited southern California annual grassland to explore this hypothesis. Our analysis shows growing season soil moisture and canopy-scale water vapor conductance are equivalent in control and fertilized plots. This consistency arises as fertilization-induced increases in leaf area index (LAI) are offset by reduced leaf area-based stomatal conductance, gs. We interpret this as evidence of a hydraulic feedback between LAI, plant water status, and gs, not commonly implemented in evapotranspiration models. These results support the notion that canopy physiology and structure are coordinated in water-limited ecosystems to maintain a transpiration flux tightly controlled by hydraulic constraints in the soil-vegetation-atmosphere pathway.

  8. Drought Experiment of a Mongolian Grassland Ecosystem

    NASA Astrophysics Data System (ADS)

    Shinoda, M.; Tsunekawa, A.; Nemoto, M.; Nachinshonhor, G. U.; Nakano, T.; Tamura, K.; Asano, M.; Erdenetsetseg, D.

    2006-12-01

    Recent large-scale climate change including global warming has likely been manifested as frequent and/or intensive drought occurrences in inland, arid Asia such as Mongolia. In order to investigate the response of a Mongolian grassland ecosystem to such a drought, an artificial drought experiment was conducted at Bayan Unjuul (105.95E, 47.04N) in the Mongolian typical steppe region during the growing season of 2005. The climatological (1995-2004) annul precipitation is 172.9mm, concentrated on the summer months of May- August, while the annual mean temperature is 0.1degC, with soil freezing during the winter. This study site is codominated by perennial grasses such as Stipa krylovii, Agropyron cristatum, and Cleistogenes squarrosa and annual forbs such as Artemisia adamsii and Chenopodium album. An area of 300m w300m in size was surrounded by a fence for protecting this area from grazing. The plots inside and outside of the area are referred to as no-grazing (NG) and grazing (G) plots, respectively. In the NG plot, two plots of 30m w30m with drought (D plot) and mowing (M plot) manipulations are allocated in the southwest part of the NG plot. The drought manipulation was conducted using a rainout shelter with a transparent polyethylene roof, open on all sides during the major growing season from late May to early August 2005. The total precipitation of 60.3mm in the annual total of 96.9mm (that is, a severe drought year) was excluded from the D plot. Thus, natural severe drought and artificial very severe drought conditions were produced in this year. To study the vegetation impact on thermal and moisture conditions at the ground surface, the mowing has been carried out on a monthly basis during the growing season. The initial conditions for each plot were examined during the late growing seasons of 2003 and 2004, showing no significant difference in terms of vegetation (above-/below-ground biomass and species diversity) and physical and chemical soil properties

  9. Controls over native perennial grass exclusion and persistence in California grasslands invaded by annuals.

    PubMed

    Mordecai, Erin A; Molinari, Nicole A; Stahlheber, Karen A; Gross, Kevin; D'Antonio, Carla

    2015-10-01

    Despite obvious impacts of nonnative species in many ecosystems, the long-term outcome of competition between native and exotic species often remains unclear. Demographic models can resolve the outcome of competition between native and exotic species and provide insight into conditions favoring exclusion vs. coexistence. California grasslands are one of the most heavily invaded ecosystems in North America. Although California native perennial bunchgrasses are thought to be restricted to a fraction of their original abundance, the eventual outcome of competition with invasive European annual grasses at a local scale (competitive exclusion, stable persistence, or priority effects) remains unresolved. Here, we used a two-species discrete time population growth model to predict the outcome of competition between exotic annual and native perennial grasses in California, and to determine the demographic traits responsible for the outcome. The model is parameterized with empirical data from several field experiments. We found that, once introduced, annual grasses persist stably with little uncertainty. Although perennial grasses are competitively excluded on average, the most likely range of model predictions also includes stable coexistence with annual grasses. As for many other perennial plants, native bunchgrass population growth is highly sensitive to the survival of adults. Management interventions that improve perennial adult survival are likely to be more effective than those that reduce exotic annual seed production or establishment, reduce competition, or increase perennial seedling establishment. Further empirical data on summer survival of bunchgrass adults and competitive effects of annuals on perennials would most improve model predictions because they contribute most to the uncertainty in the predicted outcome for the perennial grass. This work demonstrates how demographic approaches can clarify the outcome of competition between native and exotic species

  10. Soil Microbial Community Responses to Long-Term Global Change Factors in a California Grassland

    NASA Astrophysics Data System (ADS)

    Qin, K.; Peay, K.

    2015-12-01

    Soil fungal and bacterial communities act as mediators of terrestrial carbon and nutrient cycling, and interact with the aboveground plant community as both pathogens and mutualists. However, these soil microbial communities are sensitive to changes in their environment. A better understanding of the response of soil microbial communities to global change may help to predict future soil microbial diversity, and assist in creating more comprehensive models of terrestrial carbon and nutrient cycles. This study examines the effects of four global change factors (increased temperature, increased variability in precipitation, nitrogen deposition, and CO2 enrichment) on soil microbial communities at the Jasper Ridge Global Change Experiment (JRGCE), a full-factorial global change manipulative experiment on three hectares of California grassland. While similar studies have examined the effects of global change on soil microbial communities, few have manipulated more factors or been longer in duration than the JRGCE, which began field treatments in 1998. We find that nitrogen deposition, CO2 enrichment, and increased variability in precipitation significantly affect the structure of both fungal and bacterial communities, and explain more of the variation in the community structures than do local soil chemistry or aboveground plant community. Fungal richness is correlated positively with soil nitrogen content and negatively with soil water content. Arbuscular mycorrhizal fungi (AMF), which associate closely with herbaceous plants' roots and assist in nutrient uptake, decrease in both richness and relative abundance in elevated CO2 treatments.

  11. Contaminants in eggs of aquatic birds from the grasslands of central California

    USGS Publications Warehouse

    Hothem, R.L.; Welsh, D.

    1994-01-01

    Eggs were collected from the Grasslands of western Merced County, California, during 1986 and 1987, and at the Mendota Wildlife Area in Fresno County in 1987, as part of a reproductive study of nesting ducks and shorebirds. The eggs were analyzed to evaluate the effects of contaminants in agricultural drainwater on avian reproduction. Agricultural drainwater was the major source of water for irrigation and fall flooding in the Grasslands until the fall of 1985 when drainwater was mostly replaced by uncontaminated water. Drainwater had not been used at Mendota. Concentrations of arsenic and boron in eggs from all sites were lower than those known to harm avian reproduction. However, mean concentrations of selenium, a trace element known to impair avian reproduction at high dietary levels, were higher in eggs from the Grasslands than in eggs from the uncontaminated site. Although some selenium concentrations were as high as those found to have caused death or deformities at other sites, reproductive impairment was not observed in any ducks or shorebirds nesting in the Grasslands in 1986 or 1987.

  12. The Effects of Nitrogen Enrichment and a Simulated Rainfall Event on Soil Carbon Dioxide Efflux in an Annual California Grassland

    NASA Astrophysics Data System (ADS)

    Johnson, T. P.; Strong, A. L.; Chiariello, N.; Field, C. B.

    2013-12-01

    Soils contain the largest pool of carbon in terrestrial ecosystems and play a critical role in the global carbon cycle. Previous studies have shown that enhanced precipitation (projected by climate models) and human activities (such as increased fertilizer use) may alter this cycle by enhancing soil microbial activity, although effects are often variable. Soils in semi-arid grasslands play a vital role in the global carbon cycle and may be responsive to environmental perturbations. Previous studies have demonstrated that wet-up treatments positively influence soil carbon dioxide efflux rates, which are otherwise low during dry summers. A preliminary study performed in a semi-arid annual grassland has shown that long-term nitrogen enrichment (equivalent to 70kg N per hectare) positively influences soil carbon dioxide efflux during peak biomass in the wet season. However, the combined effect and seasonal dynamics of these environmental changes is poorly understood. In order to assess this interaction, we explore the short-term response of soil carbon dioxide efflux rates in a semi-arid grassland to a combination of long-term nitrogen enrichment and a simulated 20-mm rainfall event in the Jasper Ridge Global Change Experiment (JRCGE), a long-term, multi-factorial experiment in a semi-arid annual grassland located in the foothills of the Santa Cruz mountains in central California. We measured soil carbon dioxide efflux rates from pre-installed soil respiration collars for forty-eight hours after a simulated rainfall event (20mm) during the dry season in late July 2013. Both the enhanced and non-enhanced nitrogen treatments had an immediate pronounced response to the wet-up stimulation in which efflux rates increased by an average of more than six-fold. In contrast with previous studies of soil carbon dioxide efflux at JRGCE during the wet season in which N enrichment elevated efflux rates relative to controls, however, the soil carbon dioxide efflux rates in response

  13. California Wildlife Habitat Relationships System: A test in coastal scrub and annual grassland habitats

    USGS Publications Warehouse

    Howell, J.A.; Barrett, R.H.

    1998-01-01

    We tested predictions of the California Wildlife Habitat Relationships (CWHR) System in coastal scrub and annual grassland. We detected a total of 28 species of terrestrial vertebrates: 18 mammals, 9 reptiles, and 1 amphibian. The CWHR System prediction omitted 4 of these species: 3 domestic mammals and 1 reptile. For the 2 habitats combined, CWHR predicted a total of 38 species: 23 mammals, 13 reptiles, and 2 amphibians. We detected 64% of these predicted grassland species and 71% of predicted coastal scrub species. For the habitats combined, we detected 65% of the species predicted to be present by the CWHR System. We detected 68% of the mammals, 62% of the reptiles, and 50% of the amphibians predicted for these habitats. The CWHR System theoretically predicts absence rather than presence, since it is assumed that all 288 regularly occurring mammals, reptiles, and amphibians occur anywhere unless one can argue that a specific habitat, location, or habitat element is not available. By including predictions of species absence in the assessment of model performance, observed accuracy of the CWHR model predictions increased to 96% for both habitats.

  14. Usefulness of LANDSAT data for monitoring plant development and range conditions in California's annual grassland

    NASA Technical Reports Server (NTRS)

    Carneggie, D. M.; Degloria, S. D.; Colwell, R. N.

    1975-01-01

    A network of sampling sites throughout the annual grassland region of California was established to correlate plant growth stages and forage production to climatic and other environmental factors. Plant growth and range conditions were further related to geographic location and seasonal variations. A sequence of LANDSAT data was obtained covering critical periods in the growth cycle. This was analyzed by both photointerpretation and computer aided techniques. Image characteristics and spectral reflectance data were then related to forage production, range condition, range site and changing growth conditions. It was determined that repeat sequences with LANDSAT color composite images do provide a means for monitoring changes in range condition. Spectral radiance data obtained from magnetic tape can be used to determine quantitatively the critical stages in the forage growth cycle. A computer ratioing technique provided a sensitive indicator of changes in growth stages and an indication of the relative differences in forage production between range sites.

  15. Evaluating Ecosystem Services Provided by Non-Native Species: An Experimental Test in California Grasslands

    PubMed Central

    Stein, Claudia; Hallett, Lauren M.; Harpole, W. Stanley; Suding, Katharine N.

    2014-01-01

    The concept of ecosystem services – the benefits that nature provides to human's society – has gained increasing attention over the past decade. Increasing global abiotic and biotic change, including species invasions, is threatening the secure delivery of these ecosystem services. Efficient evaluation methods of ecosystem services are urgently needed to improve our ability to determine management strategies and restoration goals in face of these new emerging ecosystems. Considering a range of multiple ecosystem functions may be a useful way to determine such strategies. We tested this framework experimentally in California grasslands, where large shifts in species composition have occurred since the late 1700's. We compared a suite of ecosystem functions within one historic native and two non-native species assemblages under different grazing intensities to address how different species assemblages vary in provisioning, regulatory and supporting ecosystem services. Forage production was reduced in one non-native assemblage (medusahead). Cultural ecosystem services, such as native species diversity, were inherently lower in both non-native assemblages, whereas most other services were maintained across grazing intensities. All systems provided similar ecosystem services under the highest grazing intensity treatment, which simulated unsustainable grazing intensity. We suggest that applying a more comprehensive ecosystem framework that considers multiple ecosystem services to evaluate new emerging ecosystems is a valuable tool to determine management goals and how to intervene in a changing ecosystem. PMID:25222028

  16. A 115-year δ15N record of cumulative nitrogen pollution in California serpentine grasslands

    NASA Astrophysics Data System (ADS)

    Vallano, D.; Zavaleta, E. S.

    2010-12-01

    Until the 1980s, California’s biodiverse serpentine grasslands were threatened primarily by development and protected by reserve creation. However, nitrogen (N) fertilization due to increasing fossil fuel emissions in the expanding Bay Area is thought to be contributing to rapid, recent invasion of these ecosystems by exotic annual grasses that are displacing rare and endemic serpentine species. Documenting the cumulative effects of N deposition in this ecosystem can direct policy and management actions to mitigate the role of N deposition in its transformation. Natural abundance stable isotopes of N in vegetation have been increasingly used as bio-indicators of N deposition patterns and subsequent changes to plant N cycling and assimilation. However, the long-term record of atmospheric reactive N enrichment and the resulting changes in ecosystem N dynamics have yet to be adequately reconstructed in many ecosystems. Museum archives of vascular plant tissue are valuable sources of materials to reconstruct temporal and spatial isotopic patterns of N inputs to ecosystems. Here, we present N stable isotope data from archived and current specimens of an endemic California serpentine grassland species, leather oak (Quercus durata), since 1895 across the greater San Francisco Bay region. We measured spatial and temporal trends in stable isotope composition (δ15N and δ13C) and concentration (%N and %C) of historical and current samples of leather oak leaves from sites within the Bay Area, impacted by increasing development, and sites northeast of the Bay Area, with significantly lower rates of urbanization and industrialization. Specifically, we sampled dry museum and fresh leaf specimens from serpentine sites within Lake (n=27) and Santa Clara (n=30) counties dating from 1895 to 2010. Leaf δ15N values were stable from 1895 to the 1950s and then decreased strongly throughout the last 50 years as fossil fuel emissions rapidly increased in the Bay Area, indicating that

  17. Lessons from the California Experience.

    ERIC Educational Resources Information Center

    Smith, Martin

    1980-01-01

    Ronald Reagan's effect on higher education as governor of California and what effect he might have on U.S. colleges and universities if elected president are described. Three points are discussed: deep conservatism of Reagan, his passivity, and Reagan's relative disinterest in higher education. (MLW)

  18. Ecosystem impacts of compost and manure applications to California grazed grassland soils

    NASA Astrophysics Data System (ADS)

    DeLonge, M. S.; Silver, W. L.

    2012-12-01

    Organic matter amendments, such as compost and manure, are often applied to grasslands to improve soil conditions and enhance net primary productivity. It has been proposed that this land management strategy can sequester carbon (C) in soils and may therefore contribute to climate change mitigation. However, the net mitigation potential of organic amendments depends in part on the ecosystem response following land-application, which is likely to vary with the amendment chemical quality (C, N, C:N). To investigate the differences in ecosystem response to soil amendments of various qualities, we established research plots on three grazed annual grasslands in northern California. The study sites were sampled for soil chemical and physical properties (bulk density, temperature, and moisture), plant community composition, and peak season net primary productivity prior to and following treatment applications. In October 2011, before the rainy season, we applied a thin layer of organic amendments to the study plots. At each site, three replicate plots were treated with fresh manure (1.2 % N, 15.8 % C, C:N = 13.5), three plots were treated with a commercial plant-waste compost (2.4 % N, 26.6 % C, C:N = 11.1), and three plots were left untreated as controls. At one site, 3 additional plots received a thin layer of compost with a lower N concentration and a higher C:N ratio (1.9 % N, 27.4 % C, C:N = 14.5). All plots were sampled for greenhouse gas emissions (N2O, CH4, and CO2, n=3 per plot) using vented chambers shortly after the organic matter was applied, and then intensively following three rain events throughout the rainy season. Results showed that dry amendments were associated with negligible trace gas fluxes, but that these fluxes increased after rain events. Nitrous oxide emissions increased slightly after the first rain event and reached peak levels (approximately 20 ng N cm-1 h-1 for the manure and high N compost only) after three days, following second rain event

  19. Microbial Enzymatic Response to Reduced Precipitation and Added Nitrogen in a Southern California Grassland Ecosystem

    NASA Astrophysics Data System (ADS)

    Alster, C. J.; German, D.; Allison, S. D.

    2011-12-01

    Microbial enzymes play a fundamental role in ecosystem processes and nutrient mineralization. Although there have been many studies concluding that global climate change affects plant communities, the effects on microbial communities in leaf litter have been much less studied. We measured extracellular enzyme activities in litter decomposing in plots with either reduced precipitation or increased nitrogen in a grassland ecosystem in Loma Ridge National Landmark in Southern California. We used a reciprocal transplant design to examine the effects of plot treatment, litter origin, and microbial community origin on litter decomposition and extracellular enzyme activity. Our hypothesis was that increased nitrogen would increase activity because nitrogen often limits microbial growth, while decreased precipitation would decrease activity due to lower litter moisture levels. Samples were collected in March 2011 and analyzed for the activities of cellobiohydrolase (CBH), β-glucosidase (BG), α-glucosidase (AG), N-acetyl-β-D-glucosaminidase (NAG), β-xylosidase (BX), acid phosphatase (AP), and leucine aminopeptidase (LAP). None of the factors in the nitrogen manipulation had a significant effect on any of the enzymes, although BG, CBH, and NAG increased marginally significantly in plots with nitrogen addition (p = 0.103, p = 0.082, and p = 0.114, respectively). For the precipitation manipulation, AG, BG, BX, CBH, and NAG significantly increased in plots with reduced precipitation (p = 0.015, p <0.001, p<0.001, and p<0.001, respectively) while LAP significantly decreased (p = 0.002). LAP catalyzes the hydrolysis of polypeptides, so reduced LAP activity could result in lower rates of enzyme turnover in the reduced precipitation treatment. We also observed that AP significantly increased (p = 0.014) in litter originating from reduced precipitation plots, while AG, BX, and LAP significantly decreased (p = 0.011, p = 0.031, and 0.005, respectively). There were no significant

  20. Soil nitrifying and denitrifying capacities are altered by global change factors in a California annual grassland

    NASA Astrophysics Data System (ADS)

    Niboyet, A.; Le Roux, X.; Barthes, L.; Hungate, B.; Dijkstra, P.; Blankinship, J. C.; Brown, J. R.; Field, C. B.; Leadley, P. W.

    2009-12-01

    Nitrification and denitrification are key mediators of nitrogen (N) cycling, especially N losses, in terrestrial ecosystems, yet little is known about the long-term, in situ responses of these two microbial processes to the simultaneous and interacting global changes likely to occur this century. We investigated the responses of the two steps of nitrification - ammonia oxidation and nitrite oxidation - and of denitrification to the interactive effects of elevated CO2, warming, increased precipitation and N deposition as part of the Jasper Ridge Global Change Experiment. We followed these responses over two growing seasons of the experiment using measures of potential rates of ammonia oxidation, nitrite oxidation, and denitrification, along with key correlates of these activities (gross N mineralization, gross nitrification, soil moisture, soil NH4+ and NO3- concentrations, soil pH, soil temperature, soil CO2 and N2O effluxes, and root and shoot biomass). Across all dates, soil ammonia and nitrite oxidizing capacities responded very differently to global change treatments: soil ammonia oxidizing capacities were increased by 59% in the high N deposition treatment (likely as a result of higher substrate availability for ammonia-oxidizers), while soil nitrite oxidizing capacities did not respond to the N deposition treatment but were reduced by 10% in the increased precipitation treatment. Soil denitrifying capacities were increased by 26% in the high N deposition treatment (likely as a result of higher substrate availability for denitrifiers) and by 15% in the increased precipitation treatment (likely as a result of higher soil water content). Overall, elevated CO2 and warming were found to have little effects on soil nitrifying and denitrifying capacities, and interactive effects between global change components were rare when analyzed across multiple sampling dates. Thus, our results suggest that increased atmospheric N deposition and changes in precipitation

  1. Effects of an agricultural drainwater bypass on fishes inhabiting the Grassland Water District and the lower San Joaquin River, California

    USGS Publications Warehouse

    Saiki, M.K.; Martin, B.A.; Schwarzbach, S.E.; May, T.W.

    2001-01-01

    The Grassland Bypass Project, which began operation in September 1996, was conceived as a means of diverting brackish selenium-contaminated agricultural drainwater away from canals and sloughs needed for transporting irrigation water to wetlands within the Grassland Water District (the Grasslands), Merced County, California. The seleniferous drainwater is now routed into the San Luis Drain for conveyance to North Mud Slough and eventual disposal in the San Joaquin River. The purpose of this study was to determine the extent to which the Grassland Bypass Project has affected fishes in sloughs and other surface waters within and downstream from the Grasslands. During September-October 1997, 9,795 fish representing 25 species were captured at 13 sampling sites. Although several species exhibited restricted spatial distributions, association analysis and cluster analysis failed to identify more than one fish species assemblage inhabiting the various sites. However, seleniferous drainwater from the San Luis Drain has influenced selenium concentrations in whole fish within North Mud Slough and the San Joaquin River. The highest concentrations of selenium (12-23 ??g/g, dry weight basis) were measured in green sunfish Lepomis cyanellus from the San Luis Drain where seleniferous drainwater is most concentrated, whereas the second highest concentrations occurred in green sunfish (7.6-17 ??g/g) and bluegills Lepomis macrochirus (14-18 ??g/g) from North Mud Slough immediately downstream from the drain. Although there was some variation, fish in the San Joaquin River generally contained higher body burdens of selenium when captured immediately below the mouth of North Mud Slough (3.1-4.8 ??g/g for green sunfish, 3.7-5.0 ??g/g for bluegills) than when captured upstream from the mouth (0.67-3.3 ??g/g for green sunfish, 0.59-3.7 ??g/g for bluegills). Waterborne selenium was the single most important predictor of selenium concentrations in green sunfish and bluegills, as judged by

  2. Soil organic matter dynamics and mineral associations with depth across a toposequence from a Mediterranean grassland in Northern California

    NASA Astrophysics Data System (ADS)

    Kramer, M. G.; Yuen, W.

    2013-12-01

    The mechanisms governing soil carbon stabilization in Mediterranean grasslands are poorly understood. Consequently, how soil carbon will respond to climate change in these ecosystems, remains uncertain. We examined the distribution of carbon and it's relationship to soil mineralogy with depth across a sequence of topographic positions of grassland soils in the Central Valley of Northern California. We sampled representative 2 m deep soil cores at mid slope topopositions (resulting in 4 detailed 20 cm interval depth profiles), in conjunction with replicated 1 m deep soil profiles under two types of parent material; marine sandstone and loamy marine clay deposits. For sequentially deeper samples, we measured bulk density, particle size, soil pH, oxalate and citrate-dithionite extractable Fe, Al and Si. Inorganic and organic carbon content were determined by measuring bulk C and in the various size fractions with and without carbonate removal using a hydrochloric acid vacuum fumigation technique. C and N stable isotope ratios were also measured for both bulk and organic carbon. We found significant differences in total C storage, inorganic and organic C amount between topographic positions. Differences in pedogenic materials (oxalate and citrate-dithionate extractable Al, Fe and Si) and particle size distribution were also found. All topographic positions showed a decline in organic carbon content down to the measured depth of 2 m. South facing slopes contained a greater proportion of inorganic carbon throughout the depth profiles, declining with depth, whereas total C storage was greater on north facing slopes, where total annual above ground biomass was greater. Overall, carbon storage varied between inorganic to organic C form across the toposequence and with more or less direct association with pedogenic materials (oxalate and citrate-diothionite extractable) depending on landform position. We conclude that inorganic carbon storage may increase in these grassland

  3. Response of soil carbon dioxide efflux to fire disturbance in a long-term grassland global change experiment

    NASA Astrophysics Data System (ADS)

    Strong, A. L.; Chiariello, N.; Tobeck, T.; Field, C. B.

    2012-12-01

    How terrestrial biosphere-atmosphere carbon dioxide exchange responds to global change is an important component to understanding global feedbacks of the carbon cycle. Soils represent a global store of organic carbon on the order of 3000 Pg C. Increased carbon dioxide release from increased respiration of soil C in response to climate warming and other direct and indirect anthropogenic factors could create a positive carbon cycle feedback to climate change. Numerous studies have demonstrated that soil respiration increases under experimental warming and elevated CO2, although the long-term, multi-year dynamics of this feedback remain poorly constrained. Punctuated disturbances, such as fire, are also likely to affect soil C responses, and understanding how fire and other global change factors interact in their influence on soil respiration is important in order to fully characterize climate-carbon cycle feedbacks. Previous studies have found that fire disturbance in semi-arid grasslands reduces soil CO2. The Jasper Ridge Global Change Experiment is a thirteen-year continuous full-factorial global change manipulation (elevated carbon dioxide, temperature, precipitation, and nitrogen deposition) located in a clay-loam soil grassland in central coastal California. In summer 2011, an additional treatment condition -- a controlled burn -- was applied to half the experimental plots to provide a fire treatment, and in the following growing season, soil carbon dioxide effluxes were measured at peak aboveground plant biomass (April 2012) and after summer senescence (June 2012) using a LiCOR-6400 soil respiration chamber and infrared gas analyzer. Across all plots and other treatments, CO2 fluxes were greater in burned grassland soils than in non-burned grassland soils (p < 0.01). CO2 fluxes were also greater in grassland plots with N addition than in grassland plots without additional nutrients (p < 0.01). These two effects appear to be additive, as CO2 fluxes were greater

  4. Effects of varying fire regimes on annual grasslands in the southern Sierra Nevada of California

    USGS Publications Warehouse

    Parsons, David J.; Stohlgren, Thomas J.

    1989-01-01

    Effects of up to three successive spring and fall burns on composition and biomass of the predominantly non-native grasslands of the southern Sierra Nevada foothills were evaluated. Fall and spring burning regimes increased the number and biomass of both alien and native forb species. No native grass species became established following the treatments. Thus, whereas the biomass of alien grass species can be reduced by repeated burning, they will be replaced by increases in both alien and native forbs. Changes seen following one or two burns (spring or fall) were not sustained following cessation of burning treatment.

  5. Usefulness of LANDSAT data for monitoring plant development and range conditions in California's annual grassland

    NASA Technical Reports Server (NTRS)

    Carneggie, D. M.; Degloria, S. D.; Colwell, R. N.

    1977-01-01

    A network of sampling sites throughout the annual grassland region was established to correlate plant growth in stages and forage production to climatic and other environmental factors. Plant growth and range conditions were further related to geographic location and seasonal variations. A sequence of LANDSAT data was obtained covering critical periods in the growth cycle. Data were analyzed by both photointerpretation and computer aided techniques. Image characteristics and spectral reflectance data were then related to forage production, range condition, range site, and changing growth conditions.

  6. The parkfield, california, earthquake prediction experiment.

    PubMed

    Bakun, W H; Lindh, A G

    1985-08-16

    Five moderate (magnitude 6) earthquakes with similar features have occurred on the Parkfield section of the San Andreas fault in central California since 1857. The next moderate Parkfield earthquake is expected to occur before 1993. The Parkfield prediction experiment is designed to monitor the details of the final stages of the earthquake preparation process; observations and reports of seismicity and aseismic slip associated with the last moderate Parkfield earthquake in 1966 constitute much of the basis of the design of the experiment. PMID:17739363

  7. Isotopic Evidence that Trees Enhance Nitrogen Inputs and Cycling in California Grassland- Savanna

    NASA Astrophysics Data System (ADS)

    Perakis, S.; Kellogg, C.

    2006-12-01

    Woody vegetation is distributed patchily in many arid and semi-arid ecosystems, where it is often associated with elevated nitrogen (N) pools and availability in islands of fertility. We measured N availability and del15N in paired blue-oak versus annual grass dominated patches to characterize the causes and consequences of spatial variation in N dynamics of grassland-savanna in Sequoia - Kings Canyon National Park. We found significantly greater surface soil N pools (0-20 cm) in oak patches compared to adjacent grass areas across a 700 m elevation gradient from foothills to the savanna-forest boundary. N accumulation under oaks was associated with a 0.6 per mil depletion in soil del15N relative to grass patches. Results from a simple del15N mass balance simulation model, constrained by surface soil N and del15N measured in the field, suggest that the development of islands of N fertility under oaks can be traced primarily to enhanced N inputs, with only a small effect of greater N retention. Net N mineralization and percent nitrification in laboratory incubations were consistently higher under oaks across a range of experimental soil moisture regimes. Collectively these results suggest a scenario whereby greater N inputs to oak patches results in net N accumulation and enhanced N cycling, with a potential for greater nitrate loss as well. N concentrations of three common herbaceous annual plants were nearly 50% greater under oak than in adjacent grass patches, with community composition shifted towards more N-demanding species under oaks. We find that oaks imprint distinct N-rich islands of fertility that foster local feedback between soil N cycling, plant N uptake, and herbaceous community composition. Such patch-scale differences in N inputs and plant-soil interactions increase biogeochemical heterogeneity in grassland-savanna ecosystems, and may shape watershed-level responses to chronic N deposition.

  8. Methane-Oxidizing Bacteria in a California Upland Grassland Soil: Diversity and Response to Simulated Global Change

    PubMed Central

    Horz, Hans-Peter; Rich, Virginia; Avrahami, Sharon; Bohannan, Brendan J. M.

    2005-01-01

    We investigated the diversity of methane-oxidizing bacteria (i.e., methanotrophs) in an annual upland grassland in northern California, using comparative sequence analysis of the pmoA gene. In addition to identifying type II methanotrophs commonly found in soils, we discovered three novel pmoA lineages for which no cultivated members have been previously reported. These novel pmoA clades clustered together either with clone sequences related to “RA 14” or “WB5FH-A,” which both represent clusters of environmentally retrieved sequences of putative atmospheric methane oxidizers. Conservation of amino acid residues and rates of nonsynonymous versus synonymous nucleotide substitution in these novel lineages suggests that the pmoA genes in these clades code for functionally active methane monooxygenases. The novel clades responded to simulated global changes differently than the type II methanotrophs. We observed that the relative abundance of type II methanotrophs declined in response to increased precipitation and increased atmospheric temperature, with a significant antagonistic interaction between these factors such that the effect of both together was less than that expected from their individual effects. Two of the novel clades were not observed to respond significantly to these environmental changes, while one of the novel clades had an opposite response, increasing in relative abundance in response to increased precipitation and atmospheric temperature, with a significant antagonistic interaction between these factors. PMID:15870356

  9. Invasion of non-native grasses causes a drop in soil carbon storage in California grasslands

    NASA Astrophysics Data System (ADS)

    Koteen, Laura E.; Baldocchi, Dennis D.; Harte, John

    2011-10-01

    Vegetation change can affect the magnitude and direction of global climate change via its effect on carbon cycling among plants, the soil and the atmosphere. The invasion of non-native plants is a major cause of land cover change, of biodiversity loss, and of other changes in ecosystem structure and function. In California, annual grasses from Mediterranean Europe have nearly displaced native perennial grasses across the coastal hillsides and terraces of the state. Our study examines the impact of this invasion on carbon cycling and storage at two sites in northern coastal California. The results suggest that annual grass invasion has caused an average drop in soil carbon storage of 40 Mg/ha in the top half meter of soil, although additional mechanisms may also contribute to soil carbon losses. We attribute the reduction in soil carbon storage to low rates of net primary production in non-native annuals relative to perennial grasses, a shift in rooting depth and water use to primarily shallow sources, and soil respiratory losses in non-native grass soils that exceed production rates. These results indicate that even seemingly subtle land cover changes can significantly impact ecosystem functions in general, and carbon storage in particular.

  10. Elevated atmospheric CO{sub 2} and soil nutrients alter competitive performance of California annual grassland species

    SciTech Connect

    Reynolds, H.L.; Chapin, F.S. III; Field, C.B.

    1995-06-01

    Atmospheric CO{sub 2} and soil nutrients altered interspecific competitive performance of three grassland annuals, all exhibiting the C{sub 3} metabolic pathway. Plantago erecta, an herbaceous dicot dominant in low-fertility serpentine grassland, was the superior interspecific competitor at low soil nutrients. Bromus hordeaceus, an introduced grass dominant in higher fertility sandstone grassland, was the superior interspecific competitor at high soil nutrients. Interspecific competitive ability of Plantago was slightly enhanced under elevated CO{sub 2}, but only at high soil nutrients, whereas interspecific competitive ability of Bromus was stimulated under elevated CO{sub 2} at both low and high soil nutrients. Interspecific competitive ability of Lasthenia californica, another herbaceous dicot common in serpentine grassland, was low in all treatments, and tended to decrease with elevated CO{sub 2} at low soil nutrients. Our results suggest that elevated CO{sub 2} may shift plant species abundance of serpentine grassland in favor of Bromus hordeaceus.

  11. Insect herbivory and grass competition in a calcareous grassland: results from a plant removal experiment

    NASA Astrophysics Data System (ADS)

    Corcket, Emmanuel; Callaway, Ragan M.; Michalet, Richard

    2003-07-01

    We compared the effects of herbivory by grasshoppers and neighbourhood competition on two dominant grasses, Bromus erectus and Brachypodium pinnatum, in a calcareous grassland in the French Alps. In a fully factorial design, herbivory was reduced by insecticide spraying and competition was reduced by removal of neighbouring plants. The effects of herbivory and competition were species-dependent. Bromus, a stress-tolerant species, was strongly affected by competition, but not by herbivory. In contrast, the more competitive species, Brachypodium, was negatively affected by herbivory, but only when neighbouring vegetation was removed. The greatest herbivory pressure on isolated targets of Brachypodium is likely to be due to the indirect effects of experimental gaps, i.e. more favourable microclimatic and foraging conditions for grasshoppers. This suggests that herbivory by insects may be a confounding factor in many plant removal experiments. Field experiments designed to study the combined effects of competition and herbivory should take into account the indirect effects induced by experimental gaps.

  12. Impacts of tree rows on grassland birds and potential nest predators: a removal experiment.

    PubMed

    Ellison, Kevin S; Ribic, Christine A; Sample, David W; Fawcett, Megan J; Dadisman, John D

    2013-01-01

    Globally, grasslands and the wildlife that inhabit them are widely imperiled. Encroachment by shrubs and trees has widely impacted grasslands in the past 150 years. In North America, most grassland birds avoid nesting near woody vegetation. Because woody vegetation fragments grasslands and potential nest predator diversity and abundance is often greater along wooded edge and grassland transitions, we measured the impacts of removing rows of trees and shrubs that intersected grasslands on potential nest predators and the three most abundant grassland bird species (Henslow's sparrow [Ammodramus henslowii], Eastern meadowlark [Sturnella magna], and bobolink [Dolichonyx oryzivorus]) at sites in Wisconsin, U.S.A. We monitored 3 control and 3 treatment sites, for 1 yr prior to and 3 yr after tree row removal at the treatment sites. Grassland bird densities increased (2-4 times for bobolink and Henslow's sparrow) and nesting densities increased (all 3 species) in the removal areas compared to control areas. After removals, Henslow's sparrows nested within ≤50 m of the treatment area, where they did not occur when tree rows were present. Most dramatically, activity by woodland-associated predators nearly ceased (nine-fold decrease for raccoon [Procyon lotor]) at the removals and grassland predators increased (up to 27 times activity for thirteen-lined ground squirrel [Ictidomys tridecemlineatus]). Nest success did not increase, likely reflecting the increase in grassland predators. However, more nests were attempted by all 3 species (175 versus 116) and the number of successful nests for bobolinks and Henslow's sparrows increased. Because of gains in habitat, increased use by birds, greater production of young, and the effective removal of woodland-associated predators, tree row removal, where appropriate based on the predator community, can be a beneficial management action for conserving grassland birds and improving fragmented and degraded grassland ecosystems. PMID

  13. Impacts of tree rows on grassland birds & potential nest predators: A removal experiment

    USGS Publications Warehouse

    Ellison, Kevin S.; Ribic, Christine; Sample, David W.; Fawcett, Megan J.; Dadisman, John D.

    2013-01-01

    Globally, grasslands and the wildlife that inhabit them are widely imperiled. Encroachment by shrubs and trees has widely impacted grasslands in the past 150 years. In North America, most grassland birds avoid nesting near woody vegetation. Because woody vegetation fragments grasslands and potential nest predator diversity and abundance is often greater along wooded edge and grassland transitions, we measured the impacts of removing rows of trees and shrubs that intersected grasslands on potential nest predators and the three most abundant grassland bird species (Henslow’s sparrow [Ammodramus henslowii], Eastern meadowlark [Sturnella magna], and bobolink [Dolichonyx oryzivorus]) at sites in Wisconsin, U.S.A. We monitored 3 control and 3 treatment sites, for 1 yr prior to and 3 yr after tree row removal at the treatment sites. Grassland bird densities increased (2–4 times for bobolink and Henslow’s sparrow) and nesting densities increased (all 3 species) in the removal areas compared to control areas. After removals, Henslow’s sparrows nested within ≤50 m of the treatment area, where they did not occur when tree rows were present. Most dramatically, activity by woodland-associated predators nearly ceased (nine-fold decrease for raccoon [Procyon lotor]) at the removals and grassland predators increased (up to 27 times activity for thirteen-lined ground squirrel [Ictidomys tridecemlineatus]). Nest success did not increase, likely reflecting the increase in grassland predators. However, more nests were attempted by all 3 species (175 versus 116) and the number of successful nests for bobolinks and Henslow’s sparrows increased. Because of gains in habitat, increased use by birds, greater production of young, and the effective removal of woodland-associated predators, tree row removal, where appropriate based on the predator community, can be a beneficial management action for conserving grassland birds and improving fragmented and degraded grassland

  14. Relations between Root-zone Soil Moisture and MODIS-derived Vegetation Indices in Oak savanna and Open Grassland in California

    NASA Astrophysics Data System (ADS)

    Liu, S.; Chadwick, O.; Roberts, D.

    2008-12-01

    Optical remote sensing cannot provide direct quantification of soil moisture, but here we test the idea that plant available soil moisture can be inferred through calibration of images that quantify plant-leaf water and photosynthetic relationships. We measured relationships between volumetric soil water content in the rooting zone of annual grasslands and oak savanna and six vegetation indices (VIs) derived from MODIS data (NDVI, EVI, ARVI, SAVI,VARI and NDWI). The measured sites were part of the AmeriFlux network in California: Tonzi Ranch (oak savanna)and Vaira Ranch(open grassland). To reduce the empirical effect of linking vegetation indices to soil moisture directly, measured gross primary production (GPP) was used to bridge them. The results showed that (1) VARI was most sensitive to soil moisture variations; (2) in open grassland GPP is significantly controlled by the available water in the soil but the relationship is not linear----- GPP continues to increase in the growing season as long as soil moisture is sufficient. In oak savanna, the relationship is less obvious because oak trees can exploit water in deep soil layers. The results also demonstrated a strong linear relationship between GPP and vegetation indices for both oak savanna and open grassland. Therefore, based on the relation between GPP and root-zone soil moisture and the relation between GPP and VI, we estimated soil moisture as a function of a VI. Likely, the functional parameters are dependent on vegetation types, soil texture and topography. In order to explore the sensitivity of this relationship in areas where soil moisture and vegetation production data are not available, we will use DayCENTURY and ISOLSM models to simulate soil moisture and primary production at instrumented sites with meteorological data and soil properties data. The simulation tested in Tonzi Ranch and Vaira Ranch suggest that we can estimate root-zone soil moisture with optical remotely sensed data at large scale.

  15. Burning reveals cryptic plant diversity and promotes coexistence in a California prairie restoration experiment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grassland and prairie restoration projects in California often result in long-term establishment of only a few native plant species, even when they begin with a diverse seed palette. A likely explanation for the disappearance of certain native species over time is that they are excluded through comp...

  16. Dissolved constituents including selenium in waters in the vicinity of Kesterson National Wildlife Refuge and the west grassland, Fresno and Merced Counties, California

    USGS Publications Warehouse

    Presser, T.S.; Barnes, Ivan

    1985-01-01

    Analyses were made for dissolved constituents including selenium (Se) in waters associated with subsurface agricultural drainage from the western San Joaquin Valley of California. In the vicinity of Kesterson National Wildlife Refuge and the Grassland wetlands area Se was found to be mobilized in water. As a consequence of this mobility and bioaccumulation in the aquatic food chain, Se occurred in waterfowl at levels toxic enough to cause deformities and deaths. Se concentrations in sumps that collect subsurface agricultural drainage water and inflows to drains sampled, ultimately leading into Kesterson National Wildlife Refuge and the Grassland, ranged from 84 to 4200 microgram/L (ug/L) Se. Levels of Se were reduced in the San Luis Drain flowing into Kesterson National Wildlife Refute to approximately 300 ug/L Se and in three of the drains sampled flowing into the Grassland to approximately 50 ug/L Se. Serious effects on water fowl habitat were caused by both these levels. Se contents of algal mats and salt crusts from evaporation ponds of the San Luis Drain contained up to parts per million Se. Total ecosystem assessment of Se may be necessary for the evaluation of the toxicity of Se to the environment. No other trace element reported exceeded the various criteria for water at the level of magnitude of Se. Other dissolved constituents and the isotopic ratios of oxygen and hydrogen were analyzed to elucidate water types, reaction states of the aqueous solution with respect to minerals, and the origin of mixed waters. These data will be used later to evaluate the geologic source of Se. Methods used for collection and analysis are described and documented. Hydrologic effects were found to be complex. Preliminary indications from wells are also given. A historical sequence is adhered to and other data from the study area which serve as a guide to the toxicity of Se are included. (Author 's abstract)

  17. Mineralization of Soil Organic Matter in Two Elevated CO2 by Warming Experiments in Grassland

    NASA Astrophysics Data System (ADS)

    Pendall, E.; Hovenden, M.; Williams, A.; Dijkstra, F. A.; Morgan, J. A.

    2007-12-01

    Experimentally elevated atmospheric CO2 has enhanced carbon (C) allocation belowground, while ecosystem warming has led to losses of soil C due to enhanced mineralization of soil organic matter (SOM). Few investigations of possible interactions between elevated CO2 and temperature have been reported, but the potential for C cycling effects not to be simply additive is high. We have taken advantage of two multi-factor global change experiments being conducted in mixed C3/C4 grasslands to evaluate similarities and differences in responses of SOM mineralization rates. The TasFACE experiment in Tasmania, Australia, has been running for over 5 years, while the Prairie Heating and CO2 Enrichment (PHACE) experiment in Wyoming, USA, has been running for less than 2 years. Both experiments employ mini-FACE systems (enriched plots targeted at 550 at TasFACE and 600 ppm at PHACE) and overhead ceramic infrared emitters (heated plots targeted at +2 degrees C at TasFACE and +1.5/+3 degrees day/night at PHACE). Soil samples collected after 5 years at TasFACE and at the beginning of the second year at PHACE were incubated for three weeks to evaluate changes in labile SOM pool sizes and turnover rates. We hypothesized that elevated CO2 would enhance labile SOM pool size and that warming would reduce it, and that warming would stimulate decomposition rate. Preliminary results suggested that five years of warming enhanced decomposition rate in the TasFACE soils, but only under the C4 grass species, whereas the first two months of warming had no effects on decomposition rate at PHACE. Elevated CO2 increased mineralizable C pool sizes by 10 to 30 percent, depending on depth, in the TasFACE soils, but did not significantly alter C cycling in the PHACE soils. Short experimental duration likely explained the lack of treatment effects seen at PHACE. We plan to continue conducting parallel experiments to track temporal changes in C cycling with the expectation that interactive effects of

  18. Mammoth Mountain, California broadband seismic experiment

    NASA Astrophysics Data System (ADS)

    Dawson, P. B.; Pitt, A. M.; Wilkinson, S. K.; Chouet, B. A.; Hill, D. P.; Mangan, M.; Prejean, S. G.; Read, C.; Shelly, D. R.

    2013-12-01

    Mammoth Mountain is a young cumulo-volcano located on the southwest rim of Long Valley caldera, California. Current volcanic processes beneath Mammoth Mountain are manifested in a wide range of seismic signals, including swarms of shallow volcano-tectonic earthquakes, upper and mid-crustal long-period earthquakes, swarms of brittle-failure earthquakes in the lower crust, and shallow (3-km depth) very-long-period earthquakes. Diffuse emissions of C02 began after a magmatic dike injection beneath the volcano in 1989, and continue to present time. These indications of volcanic unrest drive an extensive monitoring effort of the volcano by the USGS Volcano Hazards Program. As part of this effort, eleven broadband seismometers were deployed on Mammoth Mountain in November 2011. This temporary deployment is expected to run through the fall of 2013. These stations supplement the local short-period and broadband seismic stations of the Northern California Seismic Network (NCSN) and provide a combined network of eighteen broadband stations operating within 4 km of the summit of Mammoth Mountain. Data from the temporary stations are not available in real-time, requiring the merging of the data from the temporary and permanent networks, timing of phases, and relocation of seismic events to be accomplished outside of the standard NCSN processing scheme. The timing of phases is accomplished through an interactive Java-based phase-picking routine, and the relocation of seismicity is achieved using the probabilistic non-linear software package NonLinLoc, distributed under the GNU General Public License by Alomax Scientific. Several swarms of shallow volcano-tectonic earthquakes, spasmodic bursts of high-frequency earthquakes, a few long-period events located within or below the edifice of Mammoth Mountain and numerous mid-crustal long-period events have been recorded by the network. To date, about 900 of the ~2400 events occurring beneath Mammoth Mountain since November 2011 have

  19. Grassland degradation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There are approximately 1.5 million square kilometers of prairie communities (grasslands)in North America, a majority of which are native grasslands. Grasslands serve ecological functions that cannot be replaced by other land uses. Examples of ecological benefits and services include the third lar...

  20. Case Study of the California Experience in Library Collection Building.

    ERIC Educational Resources Information Center

    Voigt, Melvin J.

    A variety of examples of collection development in a university system is provided by this case study. The University of California's nine campuses provide a wide variety of library acquisition experience. A retrospective view of their development reflects the changing pace and pattern of library collection building over the years. The University…

  1. Schooling Experiences of Central California Indian People across Generations

    ERIC Educational Resources Information Center

    Williams, Tara

    2012-01-01

    This exploratory study took a post-colonialist lens to record, examine and document schooling experiences of California Indian people across several generations representing three Central Valley tribes: the Mono, the Tachi Yokuts of Santa Rosa Rancheria, and the Tule River Tribe. Past and present perceptions of Indian schooling were elicited…

  2. Reproductive status of western mosquitofish inhabiting selenium- contaminated waters in the Grassland Water District, Merced County, California

    USGS Publications Warehouse

    Saiki, M.K.; Martin, B.A.; May, T.W.

    2004-01-01

    This study was implemented to determine if western mosquitofish (Gambusia affinis) populations in the Grassland Water District suffer from impaired reproduction because of seleniferous inflows of agricultural drainwater from the Grassland Bypass Project. During June to July 2001, laboratory trials with pregnant female fish collected from two seleniferous treatment sites exposed to selenium-laden drainwater and two nonseleniferous reference sites yielded fry that averaged >96% survival at birth. In addition, none of the newborn fry exhibited evidence of teratogenesis, a typical consequence of selenium toxicity. Chemical analysis of postpartum female fish and their newborn fry indicated that mosquitofish from seleniferous sites accumulated relatively high body burdens of selenium (3.96 to 17.5 ??g selenium/g in postpartum female fish and 5.35 to 29.2 ??g selenium/g in their fry), whereas those from nonseleniferous sites contained lower body burdens (0.40 to 2.72 ??g selenium/g in postpartum female fish and 0.61 to 4.68 ??g selenium/g in their fry). Collectively, these results strongly suggest that mosquitofish inhabiting selenium- contaminated waters are not experiencing adverse reproductive effects at current levels of selenium exposure.

  3. Biogenic and pedogenic controls on Si distributions and cycling in grasslands of the Santa Cruz soil chronosequence, California

    NASA Astrophysics Data System (ADS)

    White, Art F.; Vivit, Davison V.; Schulz, Marjorie S.; Bullen, Tom D.; Evett, Rand R.; Aagarwal, Jugdeep

    2012-10-01

    Biogenic and pedogenic processes control silica cycling in grasslands growing on a soil chronosequence and dominated by strong seasonal variabilities of a Mediterranean climate. Shallow pore water Si, in spite of significant annual uptake and release by plant growth and dieback, exhibits only moderate seasonal fluctuations reflecting strong buffering from labile biogenic Si, dominated by phytoliths and by secondary pedogenic silicates. Long phytolith residence times (340-900 yrs) reflect the seasonally dry climate and high solute Si concentrations. Water-extractable Si is closely associated with Al, indicating seasonal precipitation and dissolution of a highly labile 1:1 hydroxyaluminosilicate (HAS), probably allophane, which transforms in deeper soil into fine grained, poorly crystalline kaolinite. Shallow plant roots extract greater proportions of biogenic Si and deeper plant roots larger amounts pedogenic Si. High pore water Ge/Si in late winter and spring reflects the reinforcing effects of plant fractionation and concurrent dissolution of Ge-enriched HAS. The same processes produce pore waters with depleted 30Si/28Si. In the summer and fall, Ge/Si declines and 30Si/28Si increases, reflecting the cessation of plant uptake, continued dissolution of soil phytoliths and re-precipitation of less soluble HAS. Si inputs from weathering (2-90 mmol m-2 yr-1) and losses from pore water discharge (18-68 mM m-2 yr-1) are comparable for individual soils, decline with soil age and are significantly less than amounts of Si annual cycled through the vegetation (42-171 mM m-2 yr-1). Mobile Si is generally balanced in the soils with upward bio-pumping by the shallow-rooted grasses efficiently competing against downward leaching and pore water discharge. Small net annual increases in Si in the present day soils could not have been maintained over the time scale represented by the chronosequence (65-225 yrs), implying past changes in environmental conditions.

  4. Validation of SSiB model over grassland with CHeRES field experiment data in 2001

    NASA Astrophysics Data System (ADS)

    Sun, Lan; Xue, Yongkang

    2004-08-01

    The Simplified Simple Biosphere model (SSiB) is validated in off-line simulations against field measurements in the summer of 2001 from the China Heavy Rainfall Experiment and Study (CHeRES) over a grassland site located in the lower reaches of the Yangtze River. When initialized and driven by the observed atmospheric forcing, the model reproduced the observed surface heat fluxes and surface skin temperature realistically. The model was also able to well simulate the variation of soil water content. The sensitivity experiments found that the leaf reflectance was the most significant parameter in improving the estimation of surface albedo during both wet and dry periods. This study suggests that the model is capable of simulating the physical processes and of assessing the impact of biophysical parameters that relate to land-atmosphere interactions over the eastern Asian monsoon regions, which is crucial for mesoscale atmospheric models.

  5. Terrestrial activity and conservation of adult California red-legged frogs Rana aurora draytonii in coastal forests and grasslands

    USGS Publications Warehouse

    Bulger, J.B.; Scott, N.J., Jr.; Seymour, R.B.

    2003-01-01

    The federally threatened California red-legged frog Rana aurora draytonii occupies both aquatic and terrestrial habitats in its adult life stage. The terrestrial activities of this species are not well known and require documentation to assist in the development of appropriate levels of protection under the US Endangered Species Act. We studied the terrestrial activities of radio-tagged red-legged frogs (n = 8-26) inhabiting a coastal watershed in Santa Cruz County, California, during 1997-1998. In particular, we investigated (1) the use of terrestrial habitats by non-migrating adults in relation to season, breeding chronology, and precipitation, and (2) adult migration behavior, including seasonal timing, duration, distances traveled, and the use of corridors. Non-migrating red-legged frogs occupied terrestrial habitats briefly (median = 4-6 days) following infrequent summer rains, but resided nearly continuously on land (median = 20-30 days) from the onset of the winter wet-season until breeding activities commenced 1-2 months later. All of the non-migrating frogs remained within 130 m of their aquatic site of residence (median <25 m). Intervals spent on land were again brief during mid/late winter (median = 1-4 days), despite frequent and copious rainfall. Adult migration to and from breeding sites occurred from late October through mid-May (wet season). We monitored 25 migration events between aquatic sites that were 200-2800 m apart. Short distance movements ( <300 m) were completed in 1-3 days, longer movements required up to 2 months. Most migrating frogs moved overland in approximately straight lines to target sites without apparent regard to vegetation type or topography. Riparian corridors were neither essential nor preferred as migration routes. Frogs traveling overland occurred in upland habitats as far as 500 m from water. Approximately 11-22% of the adult population was estimated to migrate to and from breeding sites annually, whereas the bulk of the

  6. Grassland agriculture

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Agriculture in grassland environments is facing multiple stresses from: shifting demographics, declining and fragmented agricultural landscapes, declining environmental quality, variable and changing climate, volatile and increasing energy costs, marginal economic returns, and globalization. Degrad...

  7. Strong stoichiometric resilience after litter manipulation experiments; a case study in a Chinese grassland

    NASA Astrophysics Data System (ADS)

    Xiao, C. W.; Janssens, I. A.; Zhou, Y.; Su, J. Q.; Liang, Y.; Guenet, B.

    2014-07-01

    Global climate change has generally increased net primary production which leads to increasing litter inputs. Therefore assessing the impacts of increasing litter inputs on soil nutrients, plant growth and ecological Carbon (C) : nitrogen (N) : phosphorus (P) stoichiometry is critical for an understanding of C, N and P cycling and their feedback processes to climate change. In this study, we added plant litter to the 10-20 cm subsoil layer under a steppe community at rates equivalent to 0, 150, 300, 600 and 1200 g (dry mass) m-2 and measured the resulting C, N and P content of different pools (above and below ground plant biomass, litter, microbial biomass). High litter addition (120% of the annual litter inputs) significantly increased soil inorganic N and available P, aboveground biomass, belowground biomass and litter. Nevertheless small litter additions, which are more realistic compared to the future predictions, had no effect on the variables examined. Our results suggest that while very high litter addition can strongly affect C : N : P stoichiometry, the grassland studied here is quite resilient to more realistic inputs in terms of stoichiometric functioning. This result highlights the complexity of the ecosystem's response to climate change.

  8. Simulating small-scale climate change effects-lessons from a short-term field manipulation experiment on grassland arthropods.

    PubMed

    Buchholz, Sascha; Rolfsmeyer, Dorothee; Schirmel, Jens

    2013-10-01

    Climate change is expected to cause major consequences on biodiversity. Understanding species-specific reactions, such as species shifts, species declines, and changes in population dynamics is a key issue to quantify large-scale impacts of climate change on biotic communities. As it is often impossible or at least impracticable to conduct large-scale experiments on biotic responses to climate change, studies at a smaller scale may be a useful alternative. In our study, we therefore tested responses of grassland arthropods (carabid beetles, spiders, grasshoppers) to simulated climate change in terms of species activity densities and diversity. We conducted a controlled field experiment by changing water and microclimatic conditions at a small scale (16 m(2) ). Roof constructions were used to increase drought-like conditions, whereas water supply was enhanced by irrigation. In all, 2 038 carabid beetles (36 species), 4 893 spiders (65 species), and 303 Orthoptera (4 species) were caught using pitfall traps from May to August, 2010. During our experiment, we created an artificial small-scale climate change; and statistics revealed that these changes had short-term effects on the total number of individuals and Simpson diversity of the studied arthropod groups. Moreover, our results showed that certain species might react very quickly to climate change in terms of activity densities, which in turn might influence diversity due to shifts in abundance patterns. Finally, we devised methodological improvements that may further enhance the validity of future studies. PMID:23956202

  9. Estimation of a water budget for 1972-2000 for the Grasslands Area, central part of the Western San Joaquin Valley, California

    USGS Publications Warehouse

    Brush, Charles F.; Belitz, Kenneth; Phillips, Steven P.

    2004-01-01

    Equitable implementation of regulations restricting discharges from agricultural drains into the San Joaquin River requires a greater understanding of the influence of extreme precipitation events on the ground-water flow system. As part of a larger investigation, this study estimated ground-water recharge and ground-water pumpage, two important components of the water budget in the Grasslands drainage area in the central part of the western San Joaquin Valley, California, for the water years 1972 through 2000. These estimates will be used as inputs to a numerical simulation model of the regional ground-water flow system in the continuing investigation. Crop-acreage and surface-water delivery data were compiled for 14 water districts and 6 other areas comprising approximately 97 percent of the 600-square-mile study area. Little ground-water pumpage data exists for the study area. A climate-based approach was employed to estimate annual water-table recharge flux and ground-water pumpage for 11 water-budget areas. Ground-water pumpage was estimated from the residual irrigation demand after crop consumption of surface water. Estimated recharge flux to the water table for the entire study area averaged 0.8 ft/yr, and estimated ground-water pumpage per unit area for the entire study area averaged 0.5 ft/yr. Increased discharges from agricultural drains in the late 1990s may have been due partly to 4 years of high recharge from precipitation over the 6-year period from 1993 to 1998. Knowledge of the ratio of annual crop water demand to annual potential evapotranspiration, expressed as an aggregate crop coefficient, Kd, will facilitate estimation of annual water-budget components in future studies. Annual aggregate crop coefficients, calculated each year for the entire study area, were nearly constant at 0.59 from 1983 to 2000, and reasonably constant at 0.53 prior to 1983. The overall trend suggests continuous reductions in recharge from irrigation over time. This

  10. Microbial lipid and amino sugar responses to long-term simulated global environmental changes in a California annual grassland

    PubMed Central

    Liang, Chao; Gutknecht, Jessica L. M.; Balser, Teri C.

    2015-01-01

    Global environmental change is predicted to have major consequences for carbon cycling and the functioning of soil ecosystems. However, we have limited knowledge about its impacts on the microorganisms, which act as a “valve” between carbon sequestered in soils versus released into the atmosphere. In this study we examined microbial response to continuous 9-years manipulation of three global change factors (elevated CO2, warming, and nitrogen deposition), singly and in combination using two methods: lipid and amino sugar biomarkers at the Jasper Ridge Global Change Experiment (JRGCE). The two methods yielded important distinctions. There were limited microbial lipid differences, but many significant effects for microbial amino sugars. We found that CO2 was not a direct factor influencing soil carbon and major amino sugar pools, but had a positive impact on bacterial-derived muramic acid. Likewise, warming and nitrogen deposition appeared to enrich residues specific to bacteria despite an overall depletion in total amino sugars. The results indicate that elevated CO2, warming, and nitrogen deposition all appeared to increase bacterial-derived residues, but this accumulation effect was far offset by a corresponding decline in fungal residues. The sensitivity of microbial residue biomarker amino sugars to warming and nitrogen deposition may have implications for our predictions of global change impacts on soil stored carbon. PMID:25999926

  11. Microbial lipid and amino sugar responses to long-term simulated global environmental changes in a California annual grassland.

    PubMed

    Liang, Chao; Gutknecht, Jessica L M; Balser, Teri C

    2015-01-01

    Global environmental change is predicted to have major consequences for carbon cycling and the functioning of soil ecosystems. However, we have limited knowledge about its impacts on the microorganisms, which act as a "valve" between carbon sequestered in soils versus released into the atmosphere. In this study we examined microbial response to continuous 9-years manipulation of three global change factors (elevated CO2, warming, and nitrogen deposition), singly and in combination using two methods: lipid and amino sugar biomarkers at the Jasper Ridge Global Change Experiment (JRGCE). The two methods yielded important distinctions. There were limited microbial lipid differences, but many significant effects for microbial amino sugars. We found that CO2 was not a direct factor influencing soil carbon and major amino sugar pools, but had a positive impact on bacterial-derived muramic acid. Likewise, warming and nitrogen deposition appeared to enrich residues specific to bacteria despite an overall depletion in total amino sugars. The results indicate that elevated CO2, warming, and nitrogen deposition all appeared to increase bacterial-derived residues, but this accumulation effect was far offset by a corresponding decline in fungal residues. The sensitivity of microbial residue biomarker amino sugars to warming and nitrogen deposition may have implications for our predictions of global change impacts on soil stored carbon. PMID:25999926

  12. The 1994 TIMS airborne calibration experiment: Castaic Lake, California

    NASA Technical Reports Server (NTRS)

    Realmuto, Vincent J.; Hook, Simon J.; Vandenbosch, Jeannette

    1995-01-01

    This summary describes the 9 March 1994 Thermal Infrared Multispectral Scanner (TIMS) airborne calibration experiment conducted at Castaic Lake, California. This experiment was a collaborative effort between the TIMS and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) science teams at the Jet Propulsion Laboratory (JPL). TIMS was flown on the NASA/Ames Research Center C130 with the new retractable air fence installed in the TIMS instrument bay. The purpose of this experiment was to determine if the fence would reduce the air turbulence in the TIMS instrument bay, thereby reducing the errors in calibration caused by wind-blast cooling of the blackbody reference sources internal to TIMS. Previous experiments have indicated that the wind blast effect could cause TIMS to over-estimate surface temperatures by more than 10 C. We have examined the TIMS data from twelve lines flown over Castaic Lake. Four of the lines were flown at an altitude of approximately 2.5 km (MSL), four at an altitude of approximately 6.7 km, and four at approximately 8.3 km. At each altitude there were flights with northern and southern headings, with the aircraft level and at a positive pitch (nose-up attitude). The suite of twelve flights was designed to subject the TIMS/air fence system to different wind conditions and air temperatures. The TIMS flights were supported by a ground-truth team, who measured lake surface temperatures from a boat, and an atmosphere characterization team, who launched an airsonde and measured solar irradiance with a Reagan Sun Photometer. The Reagan measurements were used to construct a time-series of estimates of the total abundance of water vapor in the atmospheric column. These estimates were used to constrain modifications of the airsonde water vapor profile measurements made when processing the TIMS data with a customized version of the MODTRAN radiative transfer code.

  13. Biological and climatic controls on leaf litter decomposition across European forests and grasslands revealed by reciprocal litter transplantation experiments

    NASA Astrophysics Data System (ADS)

    Portillo-Estrada, M.; Pihlatie, M.; Korhonen, J. F. J.; Levula, J.; Frumau, A. K. F.; Ibrom, A.; Lembrechts, J. J.; Morillas, L.; Horváth, L.; Jones, S. K.; Niinemets, Ü.

    2015-11-01

    Projection of carbon and nitrogen cycles to future climates is associated with large uncertainties, in particular due to uncertainties how changes in climate alter soil turnover, including litter decomposition. In addition, future conditions are expected to result in changes in vegetation composition, and accordingly in litter type and quality, but it is unclear how such changes could potentially alter litter decomposition. Litter transplantation experiments were carried out across 6 European sites (4 forest and 2 grasslands) spanning a large geographical and climatic gradient (5.6-11.4 °C in annual temperature 511-878 mm in precipitation) to gain insight into biological (litter origin and type, soil type) and climatic controls on litter decomposition. The decomposition k rates were overall higher in warmer and wetter sites than in colder and drier sites, and positively correlated to the litter total specific leaf area. Also, litter N content increased as less litter mass remained and decay went further. Surprisingly, this study demonstrates that climatic controls on litter decomposition are quantitatively more important than species, litter origin and soil type. Cumulative climatic variables, precipitation and air temperature (ignoring days with air temperatures below 0 °C), were appropriate to predict the litter remaining mass during decomposition (Mr). And Mr and cumulative air temperature were found to be the best predictors for litter carbon and nitrogen remaining during decomposition. We concluded with an equation for predicting the decomposition k rate by using mean annual air temperature and litter total specific leaf area.

  14. Plant diversity effects on soil microbial functions and enzymes are stronger than warming in a grassland experiment.

    PubMed

    Steinauer, Katja; Tilman, David; Wragg, Peter D; Cesarz, Simone; Cowles, Jane M; Pritsch, Karin; Reich, Peter B; Weisser, Wolfgang W; Eisenhauer, Nico

    2015-01-01

    Anthropogenic changes in biodiversity and atmospheric temperature significantly influence ecosystem processes. However, little is known about potential interactive effects of plant diversity and warming on essential ecosystem properties, such as soil microbial functions and element cycling. We studied the effects of orthogonal manipulations of plant diversity (one, four, and 16 species) and warming (ambient, +1.5 degrees C, and +3 degrees C) on soil microbial biomass, respiration, growth after nutrient additions, and activities of extracellular enzymes in 2011 and 2012 in the BAC (biodiversity and climate) perennial grassland experiment site at Cedar Creek, Minnesota, USA. Focal enzymes are involved in essential biogeochemical processes of the carbon, nitrogen, and phosphorus cycles. Soil microbial biomass and some enzyme activities involved in the C and N cycle increased significantly with increasing plant diversity in both years. In addition, 16-species mixtures buffered warming induced reductions in topsoil water content. We found no interactive effects of plant diversity and warming on soil microbial biomass and growth rates. However, the activity of several enzymes (1,4-beta-glucosidase, 1,4-beta-N-acetylglucosaminidase, phosphatase, peroxidase) depended on interactions between plant diversity and warming with elevated activities of enzymes involved in the C, N, and P cycles at both high plant diversity and high warming levels. Increasing plant diversity consistently decreased microbial biomass-specific enzyme activities and altered soil microbial growth responses to nutrient additions, indicating that plant diversity changed nutrient limitations and/or microbial community composition. In contrast to our expectations, higher plant diversity only buffered temperature effects on soil water content, but not on microbial functions. Temperature effects on some soil enzymes were greatest at high plant diversity. In total, our results suggest that the fundamental

  15. Successive sheep grazing reduces population density of Brandt's voles in steppe grassland by altering food resources: a large manipulative experiment.

    PubMed

    Li, Guoliang; Yin, Baofa; Wan, Xinrong; Wei, Wanhong; Wang, Guiming; Krebs, Charles J; Zhang, Zhibin

    2016-01-01

    Livestock grazing has shaped grassland ecosystems around the world. Previous studies indicated grazing showed various impacts on small rodents; however, most studies were conducted over 1-2 years without controlling for confounding factors such as immigration/emigration and predation in rodents. Brandt's voles (Lasiopodomys brandtii) are generally recognized as pests because of food overlap with domestic herbivores, but are also important for biodiversity conservation because they provide nests or food to many birds. Fully understanding the ecological relationship between domestic herbivores and small mammals is essential to making ecosystem management decisions. To address these needs, we carried out a field experiment during the period 2010-2013 to assess the effects of sheep grazing on vegetation and the population density of Brandt's voles along a gradient of three grazing intensities by using 12 large-scale enclosures. Responses of Brandt's voles to livestock grazing varied with grazing intensity and year. As compared to the control group, sheep grazing had no effect on vole abundance in the first year but an overall negative effect on vole abundance in the following 3 years. Successive grazing caused decreases in survival and male body mass of voles, but had no significant effect on fecundity. Negative effects of grazing were associated with a grazing-induced deterioration in both food quantity (reflected by biomass and cover of less-preferred plants), and food quality (measured by tannin and total phenol content). Our findings highlight the urgent need for more flexible management of yearly rotational grazing to optimize livestock production while maintaining species diversity and ecosystem health. PMID:26446568

  16. Climatic controls on leaf litter decomposition across European forests and grasslands revealed by reciprocal litter transplantation experiments

    NASA Astrophysics Data System (ADS)

    Portillo-Estrada, Miguel; Pihlatie, Mari; Korhonen, Janne F. J.; Levula, Janne; Frumau, Arnoud K. F.; Ibrom, Andreas; Lembrechts, Jonas J.; Morillas, Lourdes; Horváth, László; Jones, Stephanie K.; Niinemets, Ülo

    2016-03-01

    Carbon (C) and nitrogen (N) cycling under future climate change is associated with large uncertainties in litter decomposition and the turnover of soil C and N. In addition, future conditions (especially altered precipitation regimes and warming) are expected to result in changes in vegetation composition, and accordingly in litter species and chemical composition, but it is unclear how such changes could potentially alter litter decomposition. Litter transplantation experiments were carried out across six European sites (four forests and two grasslands) spanning a large geographical and climatic gradient (5.6-11.4 °C in annual temperature 511-878 mm in precipitation) to gain insight into the climatic controls on litter decomposition as well as the effect of litter origin and species. The decomposition k rates were overall higher in warmer and wetter sites than in colder and drier sites, and positively correlated with the litter total specific leaf area. Also, litter N content increased as less litter mass remained and decay went further. Surprisingly, this study demonstrates that climatic controls on litter decomposition are quantitatively more important than species or site of origin. Cumulative climatic variables, precipitation, soil water content and air temperature (ignoring days with air temperatures below zero degrees Celsius), were appropriate to predict the litter remaining mass during decomposition (Mr). Mr and cumulative air temperature were found to be the best predictors for litter carbon and nitrogen remaining during the decomposition. Using mean annual air temperature, precipitation, soil water content and litter total specific leaf area as parameters we were able to predict the annual decomposition rate (k) accurately.

  17. Enhanced Observations with Borehole Seismographic Networks. The Parkfield, California Experiment

    SciTech Connect

    McEvilly, T.V.; Karageorgi, E.; Nadeau, R.M.

    1997-01-02

    The data acquired in the Parkfield, California experiment are unique and they are producing results that force a new look at some conventional concepts and models for earthquake occurrence and fault-zone dynamics. No fault-zone drilling project can afford to neglect installation of such a network early enough in advance of the fault-zone penetration to have a well-defined picture of the seismicity details (probably at least 1000 microearthquakes--an easy 2-3 year goal for the M<0 detection of a borehole network). Analyses of nine years of Parkfield monitoring data have revealed significant and unambiguous departures from stationarity both in the seismicity characteristics and in wave propagation details within the S-wave coda for paths within the presumed M6 nucleation zone where we also have found a high Vp/Vs anomaly at depth, and where the three recent M4.7-5.0 sequences have occurred. Synchronous changes well above noise levels have also been seen among several independent parameters, including seismicity rate, average focal depth, S-wave coda velocities, characteristic sequence recurrence intervals, fault creep and water levels in monitoring wells. The significance of these findings lies in their apparent coupling and inter-relationships, from which models for fault-zone process can be fabricated and tested with time. The more general significance of the project is its production of a truly unique continuous baseline, at very high resolution, of both the microearthquake pathology and the subtle changes in wave propagation.

  18. Grazing damage to plants and gastropod and grasshopper densities in a CO 2-enrichment experiment on calcareous grassland

    NASA Astrophysics Data System (ADS)

    Ledergerber, Stephan; Thommen, G. Heinrich; Baur, Bruno

    Plant-herbivore interactions may change as atmospheric CO 2 concentrations continue to rise. We examined the effects of elevated atmospheric CO 2 and CO 2-exposure chambers on the grazing damage to plants, and on the abundances of potential herbivores (terrestrial gastropods and grasshoppers) in a calcareous grassland in the Jura mountains of Switzerland (village of Nenzlingen). Individuals of most plant species examined showed slight grazing damage. However, plots with CO 2 enrichment and plots with ambient atmosphere did not differ in the extent of grazing damage. Similarly, plots with CO 2 enrichment and plots with ambient atmosphere did not differ in either gastropod or grasshopper density. Experimental plots with and without chambers did not differ in the number of gastropods. However, the densities of gastropods and grasshoppers and extent of grazing damage to plants were generally lower in the experimental area than in the grassland outside the experimental field.

  19. The impact of Precipitation and Grassland Vegetation on Soil Moisture Dynamics

    NASA Astrophysics Data System (ADS)

    Salve, R.; Sudderth, E. A.; St. Clair, S. B.; Torn, M. S.

    2009-12-01

    The primary objective of this study was to assess the impact of grassland vegetation and precipitation (defined by the temporal pattern of water deposition and cumulative rainfall) on near-surface hydrology. Using a randomized block design experiment in a greenhouse, we monitored soil-moisture dynamics in mesocosms planted with three types of grassland vegetation found in California (mixed California grassland, avena grass monoculture, and erodium forb monoculture). We observed that above ground biomass production was strongly influenced by rainfall amount, with most productivity in the mid-level rainfall treatment. Soil moisture content (SMC) was best predicted by rainfall, stage of plant growth, and the interaction between these two parameters. Surprisingly, SMC did not depend on species composition of the grassland. The role of ET in drying the soil was influenced by the interaction between growth stage and rainfall, and to a lesser extend by the interaction between vegetation type and growth stage. When combined, seasonal precipitation and vegetation influenced the near-surface hydrology in ways that cannot be predicted from manipulation of a single variable. These results emphasize the importance of the interactive effects of precipitation and vegetation on soil moisture dynamics, and the potential for feedbacks since soil moisture affects vegetation. This study was supported by the Program for Ecosystem Research, Office of Science, U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

  20. Resource Guide to the Pawnee Grasslands.

    ERIC Educational Resources Information Center

    Kielsmeier, Jim; And Others

    Colorado's Pawnee Grasslands are well suited for a wide range of academic study, from astronomy to zoology. Designed for educators and youth leaders seeking to integrate an alternative experience into their curriculum or recreation program, this guide is intended to give leaders of excursions to the Grasslands a sense of what's out there and some…

  1. Spatial relationship with the grazing pressure and alpine grassland degradation base on the GPS tracing experiment: a case study in the source region of Yellow River

    NASA Astrophysics Data System (ADS)

    Liu, L.; Zhang, Y.

    2014-12-01

    It is hard to distinguish the affects from the human activities and climate change on the grassland degradation, especially to quantification the human activities. Grazing is the main kind of human activities on the alpine grassland. To investigate the relationship of the grazing activities and grassland degradation will help the understanding of the effects of human impacts. A GPS tracing experiment was designed to tracing the activities of the Yaks. The spatial distribution of the grazing pressure was simulated under Geographic Information System. The biomass distribution and grazing pressure was compared to judge the distribution of overgrazing. The main research results are: (1) The tracing experiment could record the track of the Yaks very well, and it could be a good tool for the quantification research of grazing pressure. (2) The grazing activities have good relationship with vegetation, residents and landform. The worse vegetation is, the grazing time is longer and the radius is bigger. The closer to the residents, the grazing intensive is higher. The grazing route is influenced by the landform. Usually the herds would like to choose the least cost way. And the grazing intensive is higher in sunny slope. (3) The grazing probability is higher while the elevation is lower and the vegetation is better. The numbers of livestock of different villages determine the spatial distribution of the grazing pressure but it has very big heterogeneity in the same village. It seems the forage is enough in the research area since the available biomass is about 1190058t and the total demand is only 603700t. But because of the heterogeneity of the grazing pressure, there are still overgrazing in some villages. The area of overgrazing is 6 percent in the winter rangeland and 11 percent in summer rangeland. It is important to take care of the spatial heterogeneity of the grazing pressure and grass production in the management of the grassland ecosystem. It should improve the

  2. University of California electron and X-ray experiments on ISEE-3

    NASA Technical Reports Server (NTRS)

    Anderson, K. A.

    1981-01-01

    The history of the University of California solar and interplanetary electron experiment and the solar X-ray experiment is outlined, and the two instruments used are described. The roles of personnel are mentioned and the data analysis projects completed or begun are summarized. A bibliography is included.

  3. SUPERVISED FIELD EXPERIENCE AND INTERNSHIP PROGRAMS IN EDUCATIONAL ADMINISTRATION AND SUPERVISION IN THE CALIFORNIA STATE COLLEGES.

    ERIC Educational Resources Information Center

    JOHNS, W. LLOYD

    A SURVEY OF EXISTING FIELD EXPERIENCE PROGRAMS IN THE 18 CALIFORNIA STATE COLLEGES WAS CONDUCTED TO IDENTIFY THE CHARACTERISTICS OF A HIGH-QUALITY SUPERVISED FIELD-EXPERIENCE PROGRAM IN EDUCATIONAL ADMINISTRATION AND SUPERVISION. DATA FOR MAJOR FINDINGS WERE COLLECTED FROM (1) A REVIEW OF THE LITERATURE, (2) AN EXAMINATION OF FIELD-EXPERIENCE…

  4. Imprint of oaks on nitrogen availability and δ15N in California grassland-savanna: A case of enhanced N inputs?

    USGS Publications Warehouse

    Perakis, S.S.; Kellogg, C.H.

    2007-01-01

    Woody vegetation is distributed patchily in many arid and semi-arid ecosystems, where it is often associated with elevated nitrogen (N) pools and availability in islands of fertility. We measured N availability and δ15N in paired blue-oak versus annual grass dominated patches to characterize the causes and consequences of spatial variation in N dynamics of grassland-savanna in Sequoia-Kings Canyon National Park. We found significantly greater surface soil N pools (0–20 cm) in oak patches compared to adjacent grass areas across a 700 m elevation gradient from foothills to the savanna-forest boundary. N accumulation under oaks was associated with a 0.6‰ depletion in soil δ15N relative to grass patches. Results from a simple δ15N mass balance simulation model, constrained by surface soil N and δ15N measured in the field, suggest that the development of islands of N fertility under oaks can be traced primarily to enhanced N inputs. Net N mineralization and percent nitrification in laboratory incubations were consistently higher under oaks across a range of experimental soil moisture regimes, suggesting a scenario whereby greater N inputs to oak patches result in net N accumulation and enhanced N cycling, with a potential for greater nitrate loss as well. N concentrations of three common herbaceous annual plants were nearly 50% greater under oak than in adjacent grass patches, with community composition shifted towards more N-demanding species under oaks. We find that oaks imprint distinct N-rich islands of fertility that foster local feedback between soil N cycling, plant N uptake, and herbaceous community composition. Such patch-scale differences in N inputs and plant–soil interactions increase biogeochemical heterogeneity in grassland-savanna ecosystems and may shape watershed-level responses to chronic N deposition.

  5. Do grasslands act as a perpetual sink for carbon?

    PubMed

    Smith, Pete

    2014-09-01

    It is increasingly commonly suggested that grasslands are a perpetual sink for carbon, and that just maintaining grasslands will yield a net carbon sink. I examine the evidence for this from repeated soil surveys, long term grassland experiments and simple mass balance calculations. I conclude that it is untenable that grasslands act as a perpetual carbon sink, and the most likely explanation for observed grassland carbon sinks over short periods is legacy effects of land use and land management prior to the beginning of flux measurement periods. Simply having grassland does not result is a carbon sink, but judicious management or previously poorly managed grasslands can increase the sink capacity. Given that grasslands are a large store of carbon, and that it is easier and faster for soils to lose carbon that it is for them to gain carbon, it is an important management target to maintain these stocks. PMID:24604749

  6. Response of aboveground biomass and diversity to nitrogen addition – a five-year experiment in semi-arid grassland of Inner Mongolia, China

    PubMed Central

    He, Kejian; Qi, Yu; Huang, Yongmei; Chen, Huiying; Sheng, Zhilu; Xu, Xia; Duan, Lei

    2016-01-01

    Understanding the response of the plant community to increasing nitrogen (N) deposition is helpful for improving pasture management in semi-arid areas. We implemented a 5-year N addition experiment in a Stipa krylovii steppe of Inner Mongolia, northern China. The aboveground biomass (AGB) and species richness were measured annually. Along with the N addition levels, the species richness declined significantly, and the species composition changed noticeably. However, the total AGB did not exhibit a noticeable increase. We found that compensatory effects of the AGB occurred not only between the grasses and the forbs but also among Gramineae species. The plant responses to N addition, from the community to species level, lessened in dry years compared to wet or normal years. The N addition intensified the reduction of community productivity in dry years. Our study indicated that the compensatory effects of the AGB among the species sustained the stability of grassland productivity. However, biodiversity loss resulting from increasing N deposition might lead the semi-arid grassland ecosystem to be unsustainable, especially in dry years. PMID:27573360

  7. Response of aboveground biomass and diversity to nitrogen addition - a five-year experiment in semi-arid grassland of Inner Mongolia, China.

    PubMed

    He, Kejian; Qi, Yu; Huang, Yongmei; Chen, Huiying; Sheng, Zhilu; Xu, Xia; Duan, Lei

    2016-01-01

    Understanding the response of the plant community to increasing nitrogen (N) deposition is helpful for improving pasture management in semi-arid areas. We implemented a 5-year N addition experiment in a Stipa krylovii steppe of Inner Mongolia, northern China. The aboveground biomass (AGB) and species richness were measured annually. Along with the N addition levels, the species richness declined significantly, and the species composition changed noticeably. However, the total AGB did not exhibit a noticeable increase. We found that compensatory effects of the AGB occurred not only between the grasses and the forbs but also among Gramineae species. The plant responses to N addition, from the community to species level, lessened in dry years compared to wet or normal years. The N addition intensified the reduction of community productivity in dry years. Our study indicated that the compensatory effects of the AGB among the species sustained the stability of grassland productivity. However, biodiversity loss resulting from increasing N deposition might lead the semi-arid grassland ecosystem to be unsustainable, especially in dry years. PMID:27573360

  8. Resuspension and redistribution of radionuclides during grassland and forest fires in the Chernobyl exclusion zone: part I. Fire experiments.

    PubMed

    Yoschenko, V I; Kashparov, V A; Protsak, V P; Lundin, S M; Levchuk, S E; Kadygrib, A M; Zvarich, S I; Khomutinin, Yu V; Maloshtan, I M; Lanshin, V P; Kovtun, M V; Tschiersch, J

    2006-01-01

    Controlled burning of experimental plots of forest or grassland in the Chernobyl exclusion zone has been carried out in order to estimate the parameters of radionuclide resuspension, transport and deposition during forest and grassland fires and to evaluate the working conditions of firemen. An increase of several orders of magnitude of the airborne radionuclide concentration was observed in the territory near the fire area. The resuspension factor for (137)Cs and (90)Sr was determined to range from 10(-6) to 10(-5) m(-1), and for the plutonium radionuclides from 10(-7) to 10(-6) m(-1) (related to the nuclides in the combustible biomass). These values are 2 orders of magnitude lower if they are calculated relatively to the total contamination density (including the nuclides in the soil). The radionuclide fallout along the plume axis is negligible in comparison to the existing contamination. However, the additional inhalation dose for firemen exposed in the affected area can reach the level of the additional external irradiation in the period of their mission. The plutonium nuclides constitute the dominating contribution to the inhalation dose. PMID:16213067

  9. Genetic variation in response to elevated CO 2 in three grassland perennials — a field experiment with two competition regimes

    NASA Astrophysics Data System (ADS)

    Steinger, Thomas; Lavigne, Claire; Birrer, Andreas; Groppe, Kathleen; Schmid, Bernhard

    Intraspecific variation in the response to increased concentrations of atmospheric CO 2 was investigated in three plant species ( Bromus erectus, Prunella vulgaris, P. grandiflora) in a calcareous grassland. Genotypes of each species were grown both in multispecies communities and under reduced competition pressure in tubes buried in the soil. Plant growth was reduced in the artificial communities but no significant effect of CO 2 was observed on any of the measured traits. Significant genotype-by-CO 2 interactions were found in two species when plants were grown under reduced competition in the tubes. No genotype-by-CO 2 interactions were found for the same genotypes grown in the multispecies communities indicating that genetic variation was swamped by large environmental variation. Furthermore, no correlations were observed between CO 2 responses of identical genotypes grown individually in tubes and in multispecies communities. This result cautions about the ability to predict CO 2-induced evolutionary changes from data of individually-grown plants.

  10. Examining the Experiences and Adjustment Challenges of Saudi Arabian Students in the California State University System

    ERIC Educational Resources Information Center

    Caldwell, Jeremy Dean

    2013-01-01

    The purpose of this study was to examine the experiences and adjustment challenges of Saudi Arabian students in the California State University (CSU) system. Specifically, the study was conducted to better understand and serve the Saudi Arabian students studying in the system. The design for this mixed method study integrated both quantitative and…

  11. From Horse-Drawn Wagon to Hot Rod: The University of California's Digital Image Service Experience

    ERIC Educational Resources Information Center

    Burns, Maureen A.

    2006-01-01

    This article proposes that a viable approach archivists might consider to meet increasing demands for access to digital images with functional presentation tools is to develop a reciprocal partnership with a digital library. The University of California's experience with the federation of licensed and UC-owned digital image collections is…

  12. Experiences with and Preparedness for Emergencies and Disasters among Public Schools in California

    ERIC Educational Resources Information Center

    Kano, Megumi; Bourque, Linda B.

    2007-01-01

    This study assesses schools' experiences with, and preparedness for, emergencies and disasters. Data are collected by mail survey from 157 public schools in California. The majority of schools have experienced emergencies in recent years. Although respondents generally feel their school is well prepared for future emergencies, limitations are…

  13. Protecting Student Press Freedom by State Law: The Experience in California.

    ERIC Educational Resources Information Center

    Overbeck, Wayne

    Following "Tinker vs. Des Moines Community School District," the United States Supreme Court decision that assured First Amendment rights to secondary school students and teachers, California began experimenting with statutory guarantees of free expression for students at the high school and community college levels. Decisions issued by several…

  14. A multiisotope C and N modeling analysis of soil organic matter turnover and transport as a function of soil depth in a California annual grassland soil chronosequence

    USGS Publications Warehouse

    Baisden, W.T.; Amundson, Ronald; Brenner, D.L.; Cook, A.C.; Kendall, C.; Harden, J.W.

    2002-01-01

    We examine soil organic matter (SOM) turnover and transport using C and N isotopes in soil profiles sampled circa 1949, 1978, and 1998 (a period spanning pulse thermonuclear 14C enrichment of the atmosphere) along a 3-million-year annual grassland soil chronosequence. Temporal differences in soil ??14C profiles indicate that inputs of recently living organic matter (OM) occur primarily in the upper 20-30 cm but suggest that OM inputs can occur below the primary rooting zone. A three-pool SOM model with downward transport captures most observed variation in ??14C, percentages of C and N, ??13C, and ??15N, supporting the commonly accepted concept of three distinct SOM pools. The model suggests that the importance of the decadal SOM pool in N dynamics is greatest in young and old soils. Altered hydrology and possibly low pH and/or P dynamics in highly developed old soils cause changes in soil C and N turnover and transport of importance for soil biogeochemistry models.

  15. Operating experience with California's first coal fired enhanced oil recovery steam generator

    SciTech Connect

    Waldman, G.B.

    1983-11-01

    This article discusses the experiences of operating Pyropower Corporation's ''Pyroflow'' circulating fluidized bed steam generation plant in Bakersfield, California. The Pyroflow plant is shown to be demonstrating its ability to provide a reliable source of steam for enhanced oil recovery. Actual operating problems have been minimal, and those which have occurred have involved plant auxilliary equipment rather than the steam generator itself. Fluidized bed combustion is the only practical means of burning coal in environmentally sensitive areas such as California without the use of flue gas scrubbing for sulfur dioxide control. This plant operates on the circulating bed concept as distinct from conventional fluidized beds which have a fixed bed depth.

  16. A New Generation: Ethnicity, Socioeconomic Status, Immigration and the Undergraduate Experience at the University of California. General Report on the Results of the 2006 University of California Undergraduate Experience Survey

    ERIC Educational Resources Information Center

    Brint, Steve; Douglass, John Aubrey; Flacks, Richard; Thomson, Gregg; Chatman, Steve

    2007-01-01

    The Student Experience in the Research University (SERU) Project is a collaborative effort of academic scholars, IR staff, and academic and administrative leaders at each of the UC (University of California) undergraduate campuses and at UCOP (University of California Office of the President). The objective is to develop new types of data and…

  17. Before We Were Chicanas/os: The Mexican American Experience in California Higher Education, 1848-1945

    ERIC Educational Resources Information Center

    Tudico, Christopher

    2010-01-01

    Mexican American students have a long and proud history of enrolling in colleges and universities across the state of California for nearly 160 years, since shortly after the Treaty of Guadalupe Hidalgo in 1848. Yet, inexplicably, historians of higher education have virtually ignored the Mexican American experience in California higher education.…

  18. Protection of Grasslands in East Asia

    NASA Astrophysics Data System (ADS)

    Qi, Jiaguo; Groisman, Pavel; Xin, Xiaoping

    2013-10-01

    An international workshop was held to examine ways to preserve the ecological values of grassland ecosystems while maximizing the economic development benefits to the local population. Experts on grassland ecosystems from Australia, China, Mongolia, the United Kingdom, and the United States presented the latest research and regional programs for sustainable management, while local scientists highlighted detailed field experiments, their findings, and future research plans. The participation of major stakeholders and representatives of local governments allowed for a transdisciplinary assessment.

  19. Management experiences and trends for water reuse implementation in Northern California.

    PubMed

    Bischel, Heather N; Simon, Gregory L; Frisby, Tammy M; Luthy, Richard G

    2012-01-01

    In 2010, California fell nearly 300,000 acre-ft per year (AFY) short of its goal to recycle 1,000,000 AFY of municipal wastewater. Growth of recycled water in the 48 Northern California counties represented only 20% of the statewide increase in reuse between 2001 and 2009. To evaluate these trends and experiences, major drivers and challenges that influenced the implementation of recycled water programs in Northern California are presented based on a survey of 71 program managers conducted in 2010. Regulatory requirements limiting discharge, cited by 65% of respondents as a driver for program implementation, historically played an important role in motivating many water reuse programs in the region. More recently, pressures from limited water supplies and needs for system reliability are prevalent drivers. Almost half of respondents (49%) cited ecological protection or enhancement goals as drivers for implementation. However, water reuse for direct benefit of natural systems and wildlife habitat represents just 6-7% of total recycling in Northern California and few financial incentives exist for such projects. Economic challenges are the greatest barrier to successful project implementation. In particular, high costs of distribution systems (pipelines) are especially challenging, with $1 to 3 million/mile costs experienced. Negative perceptions of water reuse were cited by only 26% of respondents as major hindrances to implementation of surveyed programs. PMID:22107126

  20. The Millikan shaking experiments and high-frequency seismic wave propagation in Southern California

    NASA Astrophysics Data System (ADS)

    Tanimoto, Toshiro; Okamoto, Taro

    2014-08-01

    In order to study high-frequency seismic wave propagation, seismic wavefields generated by resonant-shaking experiments of the Millikan Library, on the campus of California Institute Technology (Pasadena, California, USA), were analysed. Because the resonant shaking frequencies are 1.12 Hz (the east-west direction) and 1.64 Hz (the north-south direction), this active-source experiment can provide opportunities for studying high-frequency seismic wave propagation in Southern California. Because they are very narrow frequency band data, the analyses must be quite different from ordinary time-domain analyses. We show, theoretically, that the signals must be dominated by surface waves. Adopting this surface wave assumption, we proceed to make two separate analyses, one on spectral amplitude and the other on phase. We present a new method to derive group velocity from phase based on the cross correlations between the station in the Millikan Library (MIK) and stations in the regional network. Our results support that an active-source experiment by resonant shaking of a building is a feasible approach for high-frequency seismic wave studies.

  1. Grazing maintains native plant diversity and promotes community stability in an annual grassland.

    PubMed

    Beck, Jared J; Hernández, Daniel L; Pasari, Jae R; Zavaleta, Erika S

    2015-07-01

    Maintaining native biodiversity in grasslands requires management and mitigation of anthropogenic changes that have altered resource availability, grazing regimes, and community composition. In California (USA), high levels of atmospheric nitrogen (N) deposition have facilitated the invasion of exotic grasses, posing a threat to the diverse plant and insect communities endemic to serpentine grasslands. Cattle grazing has been employed to mitigate the consequences of exotic grass invasion, but the ecological effects of grazing in this system are not fully understood. To characterize the effects of realistic N deposition on serpentine plant communities and to evaluate the efficacy of grazing as a management tool, we performed a factorial experiment adding N and excluding large herbivores in California's largest serpentine grassland. Although we observed significant interannual variation in community composition related to climate in our six-year study, exotic cover was consistently and negatively correlated with native plant richness. Sustained low-level N addition did not influence plant community composition, but grazing reduced grass abundance while maintaining greater native forb cover, native plant diversity, and species richness in comparison to plots excluding large herbivores. Furthermore, grazing increased the temporal stability of plant communities by decreasing year-to-year variation in native forb cover, native plant diversity, and native species richness. Taken together, our findings demonstrate that moderate-intensity cattle grazing can be used to restrict the invasive potential of exotic grasses and maintain native plant communities in serpentine grasslands. We hypothesize that the reduced temporal variability in serpentine plant communities managed by grazing may directly benefit populations of the threatened Edith's Bay checkerspot butterfly (Euphydryas editha bayensis). PMID:26485954

  2. Initial Results from the 2002 Gulf of California Conjugate Margin Seismic Experiment

    NASA Astrophysics Data System (ADS)

    Holbrook, S.; Lizarralde, D.; Kent, G.; Harding, A.; Fletcher, J.; Gonzalez-Fernandez, A.; Umhoefer, P.; Axen, G.

    2003-04-01

    The Gulf of California, which marks the ongoing separation of Baja California from mainland Mexico, is one of the few locales where active continental breakup can be studied along unambiguous flow lines that join clear conjugate margin pairs. In Fall 2002, we conducted an onshore-offshore seismic experiment across the conjugate rifted margins of the Gulf of California in several rift segments. The joint U.S.-Mexico project, sponsored principally by the MARGINS program of the U.S. National Science Foundation, aimed to image crustal structure across conjugate margins of four major basins to determine the modes of extension and the influence of sedimentation and magmatism on breakup. Here we present an overview of the experiment, which was substantially altered at sea due to concerns for marine-mammal safety, and present some preliminary findings. Three flow-line transects were acquired, in the Alarcon Basin, the Guaymas Basin, and between Cabo and Tres Marias Islands. In addition, a fourth transect across the Baja Peninsula was acquired. Data acquired included (1) multichannel seismic reflection data using the R/V Ewing’s 20-gun array and 480-channel, 6-km-long streamer, (2) wide-angle reflection/refraction data recorded on ocean-bottom seismometers, from 206 deployments conducted by the R/V New Horizon, and (3) onshore-offshore data recorded on portable seismometers deployed up to 100 km inland on all transects. Initial results from the experiment include (1) clear evidence for asymmetric basement structure on the conjugate rifted margins and across the active mid-ocean spreading center, of the Guaymas Basin, (2) the suggestion of substantial magmatism in an early failed rift of the Alarcon Basin, and (3) active subduction beneath the margin at the Tres Marias islands. In addition, we will discuss new procedures for mitigating effects on marine mammals that may have a significant impact on future U.S.-sponsored seismic reflection activities.

  3. Farm-gate budget of energy crops: an experiment to assess changes in GHGs balance due to a land use change from grassland to short rotation coppice of poplar

    NASA Astrophysics Data System (ADS)

    Sabbatini, S.; Arriga, N.; Baiocco, A.; Boschi, A.; Castaldi, S.; Consalvo, C.; Gioli, B.; Matteucci, G.; Tomassucci, M.; Zaldei, A.; Papale, D.

    2012-04-01

    Over the last decades the rising in the prices of oil pushed many farmers all over the Europe to exploit part of their fields to produce biomass for energy. Government funding promoted this trend in order to contrast global warming and Green-House Gases (GHG) emissions. Nevertheless energy crops entail, in addition to a land use change, a sum of treatments that leads again to emissions of GHG. In the context of the GHG-Europe FP7 project we set-up an experiment to study a case of land use change from grassland to Short Rotation Coppice (SRC) of poplar clones in central Italy. Through the Eddy Covariance (EC) technique, we measure carbon and energy fluxes over two different poplar SRC with different ages, and over a reference site (grassland) representing the original land use. Furthermore, we measured additional fluxes such as soil respiration, CH4 and N2O fluxes using chambers. To compute the Farm-Gate Budget (FGB) of both the grassland and the poplar plantations, we collect also additional data that contribute to GHG budget such as management (tillage, fertilizations, irrigations, harvesting) and disturbances. In this poster we present the experiment set-up and the first results resulting from the measurements.

  4. Effects of plant diversity, N fertilization, and elevated carbon dioxide on grassland soil N cycling in a long-term experiment.

    PubMed

    Mueller, Kevin E; Hobbie, Sarah E; Tilman, David; Reich, Peter B

    2013-04-01

    The effects of global environmental changes on soil nitrogen (N) pools and fluxes have consequences for ecosystem functions such as plant productivity and N retention. In a 13-year grassland experiment, we evaluated how elevated atmospheric carbon dioxide (CO2 ), N fertilization, and plant species richness alter soil N cycling. We focused on soil inorganic N pools, including ammonium and nitrate, and two N fluxes, net N mineralization and net nitrification. In contrast with existing hypotheses, such as progressive N limitation, and with observations from other, often shorter, studies, elevated CO2 had relatively static and small, or insignificant, effects on soil inorganic N pools and fluxes. Nitrogen fertilization had inconsistent effects on soil N transformations, but increased soil nitrate and ammonium concentrations. Plant species richness had increasingly positive effects on soil N transformations over time, likely because in diverse subplots the concentrations of N in roots increased over time. Species richness also had increasingly positive effects on concentrations of ammonium in soil, perhaps because more carbon accumulated in soils of diverse subplots, providing exchange sites for ammonium. By contrast, subplots planted with 16 species had lower soil nitrate concentrations than less diverse subplots, especially when fertilized, probably due to greater N uptake capacity of subplots with 16 species. Monocultures of different plant functional types had distinct effects on N transformations and nitrate concentrations, such that not all monocultures differed from diverse subplots in the same manner. The first few years of data would not have adequately forecast the effects of N fertilization and diversity on soil N cycling in later years; therefore, the dearth of long-term manipulations of plant species richness and N inputs is a hindrance to forecasting the state of the soil N cycle and ecosystem functions in extant plant communities. PMID:23504900

  5. How do soil texture, plant community composition and earthworms affected the infiltration rate in a grassland plant diversity experiment depending on season?

    NASA Astrophysics Data System (ADS)

    Fischer, Christine; Britta, Merkel; Nico, Eisenhauer; Christiane, Roscher; Sabine, Attinger; Stefan, Scheu; Anke, Hildebrandt

    2013-04-01

    Background and aims: In this study we analyzed the influences of plant community characteristics, soil texture and earthworm presence on infiltration rates on a managed grassland plant diversity experiment assessing the role of biotic and abiotic factors on soil hydrology. Methods: We measured infiltration using a hood infiltrometer in subplots with ambient and reduced earthworm density (earthworm extraction) nested in plots of different plant species richness (1, 4, and 16), plant functional group number and composition (1 to 4; legumes, grasses, small herbs, tall herbs) in early summer (June) and autumn (September, October) 2011. Results: The presence of certain plant functional groups such as grasses and legumes influenced infiltration rates and this effect enhanced during the growing season. Infiltration was significantly higher in plots containing legumes than in plots without, and it was significantly lower in the presence of grasses than in their absence. In early summer, earthworm presence and biomass increased the infiltration rates, independently of plant species richness. In October, plant species richness only affected infiltration rates in reduced earthworm plots. At the end of the growing season earthworm populations were negatively influenced by grasses and positively by legumes. In September, infiltration rates were positive related to the proportion of finer grains. The correlation disappears when removing all plots containing legumes from the sample. For all measurements the infiltration rates decreases from early summer to autumn at the matric potentials at pressure zero and -0.02 m, but not for smaller macropores at matric potentials -0.04 and -0.06m. Conclusions: Considering infiltration rates as ecosystem function, this function will largely depend on the ecosystem composition and season, not on biodiversity per se. Our results indicate that biotic factors are of overriding influence for shaping infiltration rates mainly for larger macropores

  6. Effects of biotic and abiotic indices on long term soil moisture data in a grassland biodiversity experiment

    NASA Astrophysics Data System (ADS)

    Fischer, Christine; Hohenbrink, Tobias; Leimer, Sophia; Roscher, Christiane; Ravenek, Janneke; de Kroon, Hans; Kreutziger, Yvonne; Wirth, Christian; Eisenhauer, Nico; Gleixner, Gerd; Weigelt, Alexandra; Mommer, Liesje; Beßler, Holger; Schröder, Boris; Hildebrandt, Anke

    2015-04-01

    Soil moisture is the dynamic link between climate, soil and vegetation and the dynamics and variation are affected by several often interrelated factors such as soil texture, soil structural parameters (soil organic carbon) and vegetation parameters (belowground- and aboveground biomass). For the characterization and estimation of soil moisture and its variability and the resulting water fluxes and solute transports, the knowledge of the relative importance of these factors is of major challenge for hydrology and bioclimatology. Because of the heterogeneity of these factors, soil moisture varies strongly over time and space. Our objective was to assess the spatio-temporal variability of soil moisture and factors which could explain that variability, like soil properties and vegetation cover, in in a long term biodiversity experiment (Jena Experiment). The Jena Experiment consist 86 plots on which plant species richness (0, 1, 2, 4, 8, 16, and 60) and functional groups (legumes, grasses, tall herbs, and small herbs) were manipulated in a factorial design Soil moisture measurements were performed weekly April to September 2003-2005 and 2008-2013 using Delta T theta probe. Measurements were integrated to three depth intervals: 0.0 - 0.20, 0.20 - 0.40 and 0.40 - 0.70 m. We analyze the spatio-temporal patterns of soil water content on (i) the normalized time series and (ii) the first components obtained from a principal component analysis (PCA). Both were correlated with the design variables of the Jena Experiment (plant species richness and plant functional groups) and other influencing factors such as soil texture, soil structural variables and vegetation parameters. For the time stability of soil water content, the analysis showed that plots containing grasses was consistently drier than average at the soil surface in all observed years while plots containing legumes comparatively moister, but only up to the year 2008. In 0.40 - 0.70 m soil deep plots presence of

  7. Priority effects of time of arrival of plant functional groups override sowing interval or density effects: a grassland experiment.

    PubMed

    von Gillhaussen, Philipp; Rascher, Uwe; Jablonowski, Nicolai D; Plückers, Christine; Beierkuhnlein, Carl; Temperton, Vicky M

    2014-01-01

    Priority effects occur when species that arrive first in a habitat significantly affect the establishment, growth, or reproduction of species arriving later and thus affect functioning of communities. However, we know little about how the timing of arrival of functionally different species may alter structure and function during assembly. Even less is known about how plant density might interact with initial assembly. In a greenhouse experiment legumes, grasses or forbs were sown a number of weeks before the other two plant functional types were sown (PFT) in combination with a sowing density treatment. Legumes, grasses or non-legume forbs were sown first at three different density levels followed by sowing of the remaining PFTs after three or six-weeks. We found that the order of arrival of different plant functional types had a much stronger influence on aboveground productivity than sowing density or interval between the sowing events. The sowing of legumes before the other PFTs produced the highest aboveground biomass. The larger sowing interval led to higher asymmetric competition, with highest dominance of the PFT sown first. It seems that legumes were better able to get a head-start and be productive before the later groups arrived, but that their traits allowed for better subsequent establishment of non-legume PFTs. Our study indicates that the manipulation of the order of arrival can create priority effects which favour functional groups of plants differently and thus induce different assembly routes and affect community composition and functioning. PMID:24497995

  8. Carbon sequestration strategies for crop- and grasslands evaluated in long-term field experiments in Northern Europe

    NASA Astrophysics Data System (ADS)

    Kätterer, Thomas; Bolinder, Martin; Börjesson, Gunnar; Kirchmann, Holger

    2013-04-01

    Improved management of grass- and croplands is a win-win strategy resulting in both increased soil fertility and carbon sequestration. We quantified the effect of N fertilization, organic amendments and ley-arable rotations versus continuous annual cropping systems on soil carbon stocks by analyzing data from long-term field experiments in Nordic countries. Increasing net primary production was found to be the main driver for higher soil carbon storage. Mineral N fertilization increased soil carbon stocks by about 1-2 kg C ha-1 for each kg of N applied to cropland. Ley-arable rotations, being a combination of annual and perennial crops, are expected to have C stocks intermediate between continuous grass- and croplands. A summary of data from 15 long-term sites showed that on average 0.5 Mg ha-1 yr-1 (range 0.3 to 1.1; median 0.4 Mg ha-1 yr-1) more carbon was retained in soils in ley-arable compared to exclusively annual systems, depending on species composition, management, soil depth and the duration of the studies. We also quantified the effect of organic amendments on soil carbon stocks. Retention factors calculated for straw, manure, sawdust, peat, sewage sludge and composted household waste varied widely from about 15% for above-ground crop residues to about 90% for composted household waste. We also emphasize that increased soil carbon stocks not always lead to carbon sequestration of atmospheric CO2 and discuss misunderstandings related to mitigation options earlier proposed for carbon sequestration such as organic farming, manure application, residue handling or application of biochar. Finally, the consequences of different land use and management are discussed, taking into account two critical boundaries - the limited area of agricultural land on Earth and requirements to produce sufficient food, fibres and energy for a growing population.

  9. Phenylketonuria—Experience at One Center in the First Year of Screening in California

    PubMed Central

    Peterson, Raymond M.; Koch, Richard; Schaeffler, Graciela E.; Wohlers, Audrey; Acosta, Phyllis B.; Boyle, David

    1968-01-01

    One year's experience with phenylketonuria during the calendar year 1966, the first year for compulsory newborn screening in California, was reviewed. The over-all prevalence rate from reported cases in California during this period was one case per 19,500 persons tested. Fifty-seven persons suspected of having pku were evaluated, and 25 of them were determined to be phenylketonuric. Eleven of the 25 were infants in whom the abnormality was detected through the newborn screening program or because it was detected in a sibling through a screening program. All the newborn phenylketonuric patients were developing normally at the time of last report (although the follow-up periods were short). In nine of the other children, pku was detected because they were retarded. Five retarded children who were diagnosed as phenylketonuric at another clinic were given dietary assistance. Five additional infants had elevated serum phenylalanines but did not have the classic biochemical findings of pku and are being evaluated further. Nine infants with positive screening tests exhibited biochemical and clinical findings consistent with transient tyrosinemia. Eighteen other children were evaluated and found to have no metabolic abnormality. The newborn screening program for pku is of decided benefit in early identification of a group of infants who have a high rate of potentially serious metabolic disease. Early identification permits treatment soon enough to prevent mental retardation. Newly identified patients should be evaluated in a medical setting capable of careful pediatric, biochemical and nutritional surveillance. PMID:5652755

  10. Phenylketonuria. Experience at one center in the first year of screening in California.

    PubMed

    Peterson, R M; Koch, R; Schaeffler, G E; Wohlers, A; Acosta, P B; Boyle, D

    1968-05-01

    One year's experience with phenylketonuria during the calendar year 1966, the first year for compulsory newborn screening in California, was reviewed. The over-all prevalence rate from reported cases in California during this period was one case per 19,500 persons tested. Fifty-seven persons suspected of having pku were evaluated, and 25 of them were determined to be phenylketonuric. Eleven of the 25 were infants in whom the abnormality was detected through the newborn screening program or because it was detected in a sibling through a screening program. All the newborn phenylketonuric patients were developing normally at the time of last report (although the follow-up periods were short). In nine of the other children, pku was detected because they were retarded. Five retarded children who were diagnosed as phenylketonuric at another clinic were given dietary assistance. Five additional infants had elevated serum phenylalanines but did not have the classic biochemical findings of pku and are being evaluated further. Nine infants with positive screening tests exhibited biochemical and clinical findings consistent with transient tyrosinemia. Eighteen other children were evaluated and found to have no metabolic abnormality. The newborn screening program for pku is of decided benefit in early identification of a group of infants who have a high rate of potentially serious metabolic disease. Early identification permits treatment soon enough to prevent mental retardation. Newly identified patients should be evaluated in a medical setting capable of careful pediatric, biochemical and nutritional surveillance. PMID:5652755

  11. Reconstructing the Past: Historical Interpretations and Native Experiences at Contemporary California Missions

    ERIC Educational Resources Information Center

    Lorimer, Michelle Marie

    2013-01-01

    Spanish missions that dot the landscape in California today exist as centers of historical interpretation. Visitors to California, residents of the state, and school children often turn to these sites to learn about the early history of the region. Unbeknownst to many visitors, the history presented at many contemporary California mission sites…

  12. Economics of Grassland Conversion

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this paper we provide an overview of economic factors that contribute to changes in grassland area including the relative profitability of crop and livestock production, effects of land productivity, and effects of conversion costs. We also identify other potential socio-economic influences on gr...

  13. [Experiences of undocumented Mexican migrant women when accessing sexual and reproductive health services in California, USA: a case study].

    PubMed

    Deeb-Sossa, Natalia; Díaz Olavarrieta, Claudia; Juárez-Ramírez, Clara; García, Sandra G; Villalobos, Aremis

    2013-05-01

    This study focuses on the experience of Mexican women migrants in California, USA, with the use of formal health services for sexual and reproductive health issues. The authors used a qualitative interpretative approach with life histories, interviewing eight female users of healthcare services in California and seven key informants in Mexico and California. There were three main types of barriers to healthcare: immigration status, language, and gender. Participants reported long waiting times, discriminatory attitudes, and high cost of services. A combination of formal and informal healthcare services was common. The assessment of quality of care was closely related to undocumented immigration status. Social support networks are crucial to help solve healthcare issues. Quality of care should take intercultural health issues into account. PMID:23703003

  14. Channel responses to varying sediment input: A flume experiment modeled after Redwood Creek, California

    USGS Publications Warehouse

    Madej, M.A.; Sutherland, D.G.; Lisle, T.E.; Pryor, B.

    2009-01-01

    At the reach scale, a channel adjusts to sediment supply and flow through mutual interactions among channel form, bed particle size, and flow dynamics that govern river bed mobility. Sediment can impair the beneficial uses of a river, but the timescales for studying recovery following high sediment loading in the field setting make flume experiments appealing. We use a flume experiment, coupled with field measurements in a gravel-bed river, to explore sediment transport, storage, and mobility relations under various sediment supply conditions. Our flume experiment modeled adjustments of channel morphology, slope, and armoring in a gravel-bed channel. Under moderate sediment increases, channel bed elevation increased and sediment output increased, but channel planform remained similar to pre-feed conditions. During the following degradational cycle, most of the excess sediment was evacuated from the flume and the bed became armored. Under high sediment feed, channel bed elevation increased, the bed became smoother, mid-channel bars and bedload sheets formed, and water surface slope increased. Concurrently, output increased and became more poorly sorted. During the last degradational cycle, the channel became armored and channel incision ceased before all excess sediment was removed. Selective transport of finer material was evident throughout the aggradational cycles and became more pronounced during degradational cycles as the bed became armored. Our flume results of changes in bed elevation, sediment storage, channel morphology, and bed texture parallel those from field surveys of Redwood Creek, northern California, which has exhibited channel bed degradation for 30??years following a large aggradation event in the 1970s. The flume experiment suggested that channel recovery in terms of reestablishing a specific morphology may not occur, but the channel may return to a state of balancing sediment supply and transport capacity.

  15. Twelve years and counting: California's experience with a statewide Healthy Cities and Community program.

    PubMed Central

    Twiss, J M; Duma, S; Look, V; Shaffer, G S; Watkins, A C

    2000-01-01

    California Healthy Cities and Communities is the longest running statewide program of its kind in the nation. After providing a brief history the authors give an overview of the supporting activities and resources the Program provides to Healthy Cities and Communities initiatives throughout California. PMID:10968743

  16. Public Outreach and Educational Experiences in Mexico and Latin American communities in California

    NASA Astrophysics Data System (ADS)

    Andres De Leo-Winkler, Mario; Canalizo, Gabriela; Pichardo, Barbara; Arias, Brenda

    2015-08-01

    I have created and applied diverse methods in public outreach at National Autonomous Univerisity of Mexico (UNAM) since 2001.A student-led volunteer astronomical club has been created, the biggest in Mexico. We serve over 10,000 people per year. We have created public outreach activities for the general audience: archeo-astronomical outings, scientific movie debates, conferences, courses, public telescope viewings. We have also worked with juvenile delinquents to offer them scientific opportunities when released from jail.I've also created and worked the social media for the Institute of Astronomy UNAM, which is currently the biggest social media site on astronomy in Spanish in the world. I've created and organized a mass photo exhibition (over 1 million people served) for the Institute of Astronomy, UNAM which was citizen-funded through an online platform, the first of its kind in the country. Together with my colleages, we created workshops on astronomy for children with the Mexican's government funding.I've participated in several radio and television programs/capsules designed to bring astronomy to the general audience, one in particular ("Astrophysics for Dummies") was very successful in nation-wide Mexican radio.I am currently applying all experiences to develop a new public outreach project on astronomy for the University of California - Riverside and its on-campus and surrounding Latin American communities. We are offering new workshops for blind and deaf children. We want to integrate the Latino community to our outreach activities and offer science in their language in a simple and entertaining fashion. We have also successfully applied astrophotography as a course which brings social-science and arts undergraduate students into natural sciences.Sharing experiences, success and failure stories will help new and experienced educators and public outreach professionals learn and better from past experiences.

  17. Airborne multiangle spectropolarimetric imager (AirMSPI) observations over California during NASA's polarimeter definition experiment (PODEX)

    NASA Astrophysics Data System (ADS)

    Diner, David J.; Garay, Michael J.; Kalashnikova, Olga V.; Rheingans, Brian E.; Geier, Sven; Bull, Michael A.; Jovanovic, Veljko M.; Xu, Feng; Bruegge, Carol J.; Davis, Ab; Crabtree, Karlton; Chipman, Russell A.

    2013-09-01

    The Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) is an ultraviolet/visible/near-infrared pushbroom camera mounted on a single-axis gimbal to acquire multiangle imagery over a +/-67° along-track range. The instrument flies aboard NASA's high-altitude ER-2 aircraft, and acquires Earth imagery with ~10 m spatial resolution across an 11- km wide swath. Radiance data are obtained in eight spectral bands (355, 380, 445, 470, 555, 660, 865, 935 nm). Dual photoelastic modulators (PEMs), achromatic quarter-wave plates, and wire-grid polarizers also enable imagery of the linear polarization Stokes components Q and U at 470, 660, and 865 nm. During January-February 2013, AirMSPI data were acquired over California as part of NASA's Polarimeter Definition Experiment (PODEX), a field campaign designed to refine requirements for the future Aerosol-Cloud-Ecosystem (ACE) satellite mission. Observations of aerosols, low- and mid-level cloud fields, cirrus, aircraft contrails, and clear skies were obtained over the San Joaquin Valley and the Pacific Ocean during PODEX. Example radiance and polarization images are presented to illustrate some of the instrument's capabilities.

  18. Development and Adoption of a Watershed Approach to Compensatory Mitigation: Experiences in Colorado and California

    EPA Science Inventory

    In this article, we examine the adoption of the watershed approach and its technical methods into regulatory programs in Colorado and California. Specific steps and motives for the adoption are explained. Through close collaboration, regulators have systematically been made aware...

  19. The Effects of Carbon Dioxide Sequestration on Deep-sea Foraminifera in two California Margin Experiments

    SciTech Connect

    Ricketts, Erin R

    2006-01-01

    ABSTRACT Deep-sea sequestration of CO2 is being considered as a possible mitigation tool to decrease atmospheric CO2 concentrations and its associated negative effects. This study is the first to investigate potential effects of liquid carbon dioxide (CO2) injection on deep-sea foraminiferal assemblages. Foraminifera are ideal for this ecological impact investigation because of differing test composition (calcareous and non-calcareous) and thickness, and diverse epifaunal and infaunal depth preferences. The experiment was conducted August-September 2003, at 3600m off the coast of Monterey Bay, California, aboard the R/V Western Flyer using the ROV Tiburon. The pH of the site was monitored throughout the experiment by Seabird CTDs. Sediment push-cores were collected (both from the experimental and control sites) and stained to distinguish live (stained) from dead (unstained) individuals. Effects of CO2 injection on assemblages have been tracked both vertically (to 10cm depth below sea floor) and horizontally (up to 10m from CO2 injection sites), as well as between live and dead individuals. Within the corrals and underlying sediments severe pH changes (to near 4.0) were seen while over the experimental area small average reductions in ocean pH (-0.05 units) and large episodic excursions (-1.7 units) were measured resulting from CO2 injection. Exposure to this gradient of low pH caused increased mortality and dissolution of calcareous forms within corrals, as far as 5m from the injection site, and to at least 10cm depth in the sediments. This experiment revealed several major effects of CO2 injection on foraminiferal assemblages in surficial sediments: 1) total number of foraminifera in a sample decreases; 2) foraminiferal species richness decreases in both stained and unstained specimens; and 3) percentage of stained (live) forms increases. Down-core trends (to 10cm below sea floor) have revealed: 1) percent agglutinated forms decline and calcareous forms increase

  20. Particle size reduction in debris flows: Laboratory experiments compared with field data from Inyo Creek, California

    NASA Astrophysics Data System (ADS)

    Arabnia, O.; Sklar, L. S.; Mclaughlin, M. K.

    2014-12-01

    Rock particles in debris flows are reduced in size through abrasion and fracture. Wear of coarse sediments results in production of finer particles, which alter the bulk material rheology and influence flow dynamics and runout distance. Particle wear also affects the size distribution of coarse particles, transforming the initial sediment size distribution produced on hillslopes into that delivered to the fluvial channel network. A better understanding of the controls on particle wear in debris flows would aid in the inferring flow conditions from debris flow deposits, in estimating the initial size of sediments entrained in the flow, and in modeling debris flow dynamics and mapping hazards. The rate of particle size reduction with distance traveled should depend on the intensity of particle interactions with other particles and the flow boundary, and on rock resistance to wear. We seek a geomorphic transport law to predict rate of particle wear with debris flow travel distance as a function of particle size distribution, flow depth, channel slope, fluid composition and rock strength. Here we use four rotating drums to create laboratory debris flows across a range of scales. Drum diameters range from 0.2 to 4.0 m, with the largest drum able to accommodate up to 2 Mg of material, including boulders. Each drum has vanes along the boundary to prevent sliding. Initial experiments use angular clasts of durable granodiorite; later experiments will use less resistant rock types. Shear rate is varied by changing drum rotational velocity. We begin experiments with well-sorted coarse particle size distributions, which are allowed to evolve through particle wear. The fluid is initially clear water, which rapidly acquires fine-grained wear products. After each travel increment all coarse particles (mass > 0.4 g) are weighed individually. We quantify particle wear rates using statistics of size and mass distributions, and by fitting various comminution functions to the data

  1. A Mechanistic Study of Plant and Microbial Controls over R* for Nitrogen in an Annual Grassland

    PubMed Central

    Levine, Jonathan M.; HilleRisLambers, Janneke

    2014-01-01

    Differences in species' abilities to capture resources can drive competitive hierarchies, successional dynamics, community diversity, and invasions. To investigate mechanisms of resource competition within a nitrogen (N) limited California grassland community, we established a manipulative experiment using an R* framework. R* theory holds that better competitors within a N limited community should better depress available N in monoculture plots and obtain higher abundance in mixture plots. We asked whether (1) plant uptake or (2) plant species influences on microbial dynamics were the primary drivers of available soil N levels in this system where N structures plant communities. To disentangle the relative roles of plant uptake and microbially-mediated processes in resource competition, we quantified soil N dynamics as well as N pools in plant and microbial biomass in monoculture plots of 11 native or exotic annual grassland plants over one growing season. We found a negative correlation between plant N content and soil dissolved inorganic nitrogen (DIN, our measure of R*), suggesting that plant uptake drives R*. In contrast, we found no relationship between microbial biomass N or potential net N mineralization and DIN. We conclude that while plant-microbial interactions may have altered the overall quantity of N that plants take up, the relationship between species' abundance and available N in monoculture was largely driven by plant N uptake in this first year of growth. PMID:25170943

  2. Introduction to Grassland Management. Instructor Guide, Student Reference [and] Crop and Grassland Plant Identification Manual.

    ERIC Educational Resources Information Center

    Suits, Susie

    This packet contains an Instructor guide and student reference for a course in introduction to grassland management, as well as a crop and grassland plant identification manual. The three-unit curriculum contains the following 11 lessons: (unit I, grasslands and grassland plants): (1) an introduction to grasslands; (2) plant classification; (3)…

  3. Local Control Funding Formula in California: How to Monitor Progress and Learn from a Grand Experiment

    ERIC Educational Resources Information Center

    Fuller, Bruce; Tobben, Laura

    2014-01-01

    The Local Control Funding Formula (LCFF) was enacted by the California legislature in June 2013 and fundamentally changes the distribution of education dollars to districts. The legislation simplifies the formula for sending money to districts and now takes into account the higher costs of educating certain groups of students, specifically those…

  4. Before the Federal Bilingual Education Act: Legislation and Lived Experience in California

    ERIC Educational Resources Information Center

    Petrzela, Natalia Mehlman

    2010-01-01

    The federal Bilingual Education Act (BEA; 1968) augured a new era in the national politics of diversity, schooling, and state, and California became symbolic of the problems and promise of bilingual pedagogy. This article explores how the BEA was pivotal not only in conceiving a federal commitment to the educational achievement of…

  5. Bumpy Path into a Profession: What California's Beginning Teachers Experience. Policy Brief 14-2

    ERIC Educational Resources Information Center

    Koppich, Julia E.; Humphrey, Daniel C.

    2014-01-01

    In California as elsewhere, state policy anticipates that aspiring teachers will follow a uniform, multistep path into the profession. It assumes they will complete a preparation program and earn a preliminary credential, take a teaching job and be assigned probationary status, complete a two-year induction program (the Beginning Teacher Support…

  6. The Eco-Village Experience at California State University, Fresno: An Integrated Approach to Service Learning

    ERIC Educational Resources Information Center

    Luo, Yupeng; Crask, Lloyd; Dyson, Arthur; Zoghi, Manoochehr; Hyatt, Brad

    2011-01-01

    Poverty has caused enormous pressures and urgent needs in the city of Fresno. In an effort to incorporate a deep awareness of social, cultural, and environmental needs of the Fresno area in engineering and design education, a pilot design-build program entitled Eco-village at California State University, Fresno, has been established. Students from…

  7. Revenue/Expenditure Limits and Override Elections: The Experience of California School Districts.

    ERIC Educational Resources Information Center

    Osman, Jack W.; Gemello, John M.

    The revenue and expenditure limit contained in California's SB-90 legislation was the legislature's response to the Supreme Court's mandate to equalize spending among the state's public schools. An escape valve written into SB-90 granted districts the power to override the revenue limit by a simple majority vote. This paper examines the strategies…

  8. Collaborative Governance: Structures for Success. The California and Yosemite Community College District Experience.

    ERIC Educational Resources Information Center

    Draper, Brice; Van Groningen, Tom

    Assembly Bill (AB) 1725 addresses the mission, functions, governance, finance, staffing, programs, services, and accountability of the California Community Colleges (CCC). Many of the bill's recommendations place emphasis on the 107 community colleges, the CCC Chancellor's Office, and the Board of Governors (BOG) becoming a single system of…

  9. Enhancing Price Response Programs through Auto-DR: California's 2007 Implementation Experience

    SciTech Connect

    Kiliccote, Sila; Wikler, Greg; Chiu, Albert; Piette, Mary Ann; Kiliccote, Sila; Hennage, Dan; Thomas, Chuck

    2007-12-18

    This paper describes automated demand response (Auto-DR) activities, an innovative effort in California to ensure that DR programs produce effective and sustainable impacts. Through the application of automation and communication technologies coupled with well-designed incentives and DR programs such as Critical Peak Pricing (CPP) and Demand Bidding (DBP), Auto-DR is opening up the opportunity for many different types of buildings to effectively participate in DR programs. We present the results of Auto-DR implementation efforts by the three California investor-owned utilities for the Summer of 2007. The presentation emphasizes Pacific Gas and Electric Company's (PG&E) Auto-DR efforts, which represents the largest in the state. PG&E's goal was to recruit, install, test and operate 15 megawatts of Auto-DR system capability. We describe the unique delivery approaches, including optimizing the utility incentive structures designed to foster an Auto-DR service provider community. We also show how PG&E's Critical Peak Pricing (CPP) and Demand Bidding (DBP) options were called and executed under the automation platform. Finally, we show the results of the Auto-DR systems installed and operational during 2007, which surpassed PG&E's Auto-DR goals. Auto-DR is being implemented by a multi-disciplinary team including the California Investor Owned Utilities (IOUs), energy consultants, energy management control system vendors, the Lawrence Berkeley National Laboratory (LBNL), and the California Energy Commission (CEC).

  10. Forecasting Price Increase Needs for Library Materials: The University of California Experience.

    ERIC Educational Resources Information Center

    Smith, Dennis

    1984-01-01

    Examines steps taken by the University of California to establish an adequate base library book budget and to measure price increase needs to maintain budgeted acquisition rates. The Voigt/Susskind Acquisitions Model, securing adequate funding for price increase needs, and the university's price increase justification are highlighted. (EJS)

  11. GAIN: Early Implementation Experiences and Lessons. California's Greater Avenues for Independence Program.

    ERIC Educational Resources Information Center

    Riccio, James; And Others

    California's Greater Avenues for Independence (GAIN) program requires that large numbers of welfare recipients receive job training and preparation for employment. A survey of the program analyzed early operations in 8 of the first 10 counties to implement it; data were gathered from program staff, case records, and field research of the first…

  12. Student Outcomes Assessment: What Makes it Work? Assessment Practices & Experiences in the California State University.

    ERIC Educational Resources Information Center

    California State Univ. and Colleges, Long Beach. Inst. for Teaching and Learning.

    This monograph is a collection of papers that emerged from a project evaluating the implementation of college outcomes assessment at the campuses of the California State University (CSU) system. Fifteen pilot projects integrated their outcomes assessment in the academic majors and in general education from 1986 to 1990 and the projects were then…

  13. Grassland productivity limited by multiple nutrients.

    PubMed

    Fay, Philip A; Prober, Suzanne M; Harpole, W Stanley; Knops, Johannes M H; Bakker, Jonathan D; Borer, Elizabeth T; Lind, Eric M; MacDougall, Andrew S; Seabloom, Eric W; Wragg, Peter D; Adler, Peter B; Blumenthal, Dana M; Buckley, Yvonne M; Chu, Chengjin; Cleland, Elsa E; Collins, Scott L; Davies, Kendi F; Du, Guozhen; Feng, Xiaohui; Firn, Jennifer; Gruner, Daniel S; Hagenah, Nicole; Hautier, Yann; Heckman, Robert W; Jin, Virginia L; Kirkman, Kevin P; Klein, Julia; Ladwig, Laura M; Li, Qi; McCulley, Rebecca L; Melbourne, Brett A; Mitchell, Charles E; Moore, Joslin L; Morgan, John W; Risch, Anita C; Schütz, Martin; Stevens, Carly J; Wedin, David A; Yang, Louie H

    2015-01-01

    Terrestrial ecosystem productivity is widely accepted to be nutrient limited(1). Although nitrogen (N) is deemed a key determinant of aboveground net primary production (ANPP)(2,3), the prevalence of co-limitation by N and phosphorus (P) is increasingly recognized(4-8). However, the extent to which terrestrial productivity is co-limited by nutrients other than N and P has remained unclear. Here, we report results from a standardized factorial nutrient addition experiment, in which we added N, P and potassium (K) combined with a selection of micronutrients (K+μ), alone or in concert, to 42 grassland sites spanning five continents, and monitored ANPP. Nutrient availability limited productivity at 31 of the 42 grassland sites. And pairwise combinations of N, P, and K+μ co-limited ANPP at 29 of the sites. Nitrogen limitation peaked in cool, high latitude sites. Our findings highlight the importance of less studied nutrients, such as K and micronutrients, for grassland productivity, and point to significant variations in the type and degree of nutrient limitation. We suggest that multiple-nutrient constraints must be considered when assessing the ecosystem-scale consequences of nutrient enrichment. PMID:27250253

  14. PoroTomo Subtask 3.2 Data files from the Distributed Acoustic Sensing experiment at Garner Valley, California

    DOE Data Explorer

    Chelsea Lancelle

    2013-09-11

    In September 2013, an experiment using Distributed Acoustic Sensing (DAS) was conducted at Garner Valley, a test site of the University of California Santa Barbara (Lancelle et al., 2014). This submission includes all DAS data recorded during the experiment. The sampling rate for all files is 1000 samples per second. Any files with the same filename but ending in _01, _02, etc. represent sequential files from the same test. Locations of the sources are plotted on the basemap in GDR submission 481, titled: "PoroTomo Subtask 3.2 Sample data from a Distributed Acoustic Sensing experiment at Garner Valley, California (PoroTomo Subtask 3.2)." Lancelle, C., N. Lord, H. Wang, D. Fratta, R. Nigbor, A. Chalari, R. Karaulanov, J. Baldwin, and E. Castongia (2014), Directivity and Sensitivity of Fiber-Optic Cable Measuring Ground Motion using a Distributed Acoustic Sensing Array (abstract # NS31C-3935), AGU Fall Meeting. 
https://agu.confex.com/agu/fm1/meetingapp.cgi#Paper/19828 The e-poster is available at: https://agu.confex.com/data/handout/agu/fm14/Paper_19828_handout_696_0.pdf

  15. Data from a solute transport experiment in the Leviathan Mine drainage, Alpine County, California, October 1982

    USGS Publications Warehouse

    Flint, M.R.; Bencala, K.E.; Zellweger, G.W.; Hammermeister, D.P.

    1985-01-01

    A twenty-four hour injection of chloride and sodium was made into Leviathan Creek, Alpine County, California to aid interpretation of the coupled interactions between physical transport processes and geochemical reactions. Leviathan Creek was chosen because it receives acid mine drainage from Leviathan Mine, an abandoned open-pit sulfur mine. Water samples were collected at 15 sites along a 4.39 kilometer reach and analyzed for chloride, sodium, sulfate and fluoride. Dissolved concentrations are presented in tabular format and time-series plots. Duplicate samples were analyzed by two laboratories: the Central Laboratory, Denver, Colorado and a research laboratory in Menlo Park, California. A tabular comparison of the analyses and plots of the differences between the two laboratories is presented. Hydrographs and instantaneous discharge measurements are included. (USGS)

  16. The effect of fire intensity, nutrients, soil microbes, and spatial distance on grassland productivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding nutrient limitation is essential for interpreting grassland dynamics and responses to disturbance(s). Effects of fire on the biomass of grassland plants and soil microbes is likely mediated by short-term pulses of limiting resources. We used a replicated fire ecology experiment with ...

  17. AIDS-related experiences of primary care physicians in rural California, 1995.

    PubMed Central

    Lewis, C E

    1996-01-01

    A telephone survey was conducted of primary care physicians in nonmetropolitan counties of California. In a random sample of those counties reporting fewer than 30 cases of the acquired immunodeficiency syndrome (AIDS) as of December 1994, all physicians in practice were called; in counties reporting from 31 to 150 cases of AIDS as of the same date, a 30% random sample was selected for interviewing. Completion rates were 82% in the smallest counties and 70% in the larger counties (overall 72%). Two thirds of physicians reported that they had seen a patient positive for the human immunodeficiency virus and were providing continuing care for the disease. In all, 60% of physicians had seen a patient with AIDS. In these counties, there were 653 primary care physicians and 873 patients living with AIDS. The proportion of physicians providing care to persons with AIDS was twice that reported in previous surveys done in Los Angeles, California. In the interval (1985-1994), there was a 20-fold increase in the number of AIDS cases in California. In the nonmetropolitan areas, the number of AIDS cases in late 1994 was 290 times that reported in 1985. PMID:8686298

  18. The Immigrant University: Assessing the Dynamics of Race, Major and Socioeconomic Characteristics at the University of California. A Student Experience in the Research University (SERU) Project Research Paper. Research & Occasional Paper Series: CSHE.19.07

    ERIC Educational Resources Information Center

    Douglass, John Aubrey; Roebken, Heinke; Thomson, Gregg

    2007-01-01

    The University of California has long been a major source of socioeconomic mobility in California. Data from the University of California's Undergraduate Experience Survey (UCUES) indicates that more than half the undergraduate students in the UC system have at least one parent that is an immigrant. The ratio is even higher at UC Berkeley. What do…

  19. [Vegetation index estimation by chlorophyll content of grassland based on spectral analysis].

    PubMed

    Xiao, Han; Chen, Xiu-Wan; Yang, Zhen-Yu; Li, Huai-Yu; Zhu, Han

    2014-11-01

    Comparing the methods of existing remote sensing research on the estimation of chlorophyll content, the present paper confirms that the vegetation index is one of the most practical and popular research methods. In recent years, the increasingly serious problem of grassland degradation. This paper, firstly, analyzes the measured reflectance spectral curve and its first derivative curve in the grasslands of Songpan, Sichuan and Gongger, Inner Mongolia, conducts correlation analysis between these two spectral curves and chlorophyll content, and finds out the regulation between REP (red edge position) and grassland chlorophyll content, that is, the higher the chlorophyll content is, the higher the REIP (red-edge inflection point) value would be. Then, this paper constructs GCI (grassland chlorophyll index) and selects the most suitable band for retrieval. Finally, this paper calculates the GCI by the use of satellite hyperspectral image, conducts the verification and accuracy analysis of the calculation results compared with chlorophyll content data collected from field of twice experiments. The result shows that for grassland chlorophyll content, GCI has stronger sensitivity than other indices of chlorophyll, and has higher estimation accuracy. GCI is the first proposed to estimate the grassland chlorophyll content, and has wide application potential for the remote sensing retrieval of grassland chlorophyll content. In addition, the grassland chlorophyll content estimation method based on remote sensing retrieval in this paper provides new research ideas for other vegetation biochemical parameters' estimation, vegetation growth status' evaluation and grassland ecological environment change's monitoring. PMID:25752061

  20. Electric industry restructuring and environmental issues: A comparative analysis of the experience in California, New York, and Wisconsin

    SciTech Connect

    Fang, J.M.; Galen, P.S.

    1996-08-01

    Since the California Public Utilities Commission (CPUC) issued its April 20, 1994, Blue Book proposal to restructure the regulation of electric utilities in California to allow more competition, over 40 states have initiated similar activities. The question of how major public policy objectives such as environmental protection, energy efficiency, renewable energy, and assistance to low-income customers can be sustained in the new competitive environment is also an important element being considered. Because many other states will undergo restructuring in the future, the experience of the {open_quotes}early adopter{close_quotes} states in addressing public policy objectives in their electric service industry restructuring processes can provide useful information to other states. The Competitive Resource Strategies Program of the U.S. Department of Energy`s (DOE`s) Office of Utility Technologies, is interested in documenting and disseminating the experience of the pioneering states. The Center for Energy Analysis and Applications of the National Renewable Energy Laboratory assisted the Office of Utility Technologies in this effort with a project on the treatment of environmental issues in electric industry restructuring.

  1. Chicken Farming in Grassland Increases Environmental Sustainability and Economic Efficiency

    PubMed Central

    Liu, Meizhen; Wang, Bingxue; Osborne, Colin P.; Jiang, Gaoming

    2013-01-01

    Background Grassland degradation caused by overgrazing poses a threat to both animal husbandry and environmental sustainability in most semi-arid areas especially north China. Although the Chinese Government has made huge efforts to restore degraded grasslands, a considerable attempt has unfortunately failed due to an inadequate consideration of economic benefits to local communities. Methodology/Principal Findings A controlled field experiment was conducted to test our hypothesis that utilizing natural grasslands as both habitat and feed resources for chickens and replacing the traditional husbandry system with chicken farming would increase environmental sustainability and raise income. Aboveground plant biomass elevated from 25 g m−2 for grazing sheep to 84 g m−2 for chicken farming. In contrast to the fenced (unstocked) grassland, chicken farming did not significantly decrease aboveground plant biomass, but did increase the root biomass by 60% (p<0.01). Compared with traditional sheep grazing, chicken farming significantly improved soil surface water content (0–10 cm), from 5% to 15%. Chicken farming did not affect the soil bulk density, while the traditional sheep grazing increased the soil bulk density in the 0–10 cm soil layer by 35% of the control (p<0.05). Most importantly, the economic income of local herdsmen has been raised about six times compared with the traditional practice of raising sheep. Ecologically, such an innovative solution allowed large degraded grasslands to naturally regenerate. Grasslands also provided a high quality organic poultry product which could be marketed in big cities. Conclusion/Significance Chicken farming is an innovative alternative strategy for increasing environmental sustainability and economic income, rather than a challenge to the traditional nomadic pastoral system. Our approach might be technically applicable to other large degraded grasslands of the world, especially in China. PMID:23372678

  2. Geothermal Gases--Community Experiences, Perceptions, and Exposures in Northern California.

    PubMed

    Chiu, Cindy H; Lozier, Matthew J; Bayleyegn, Tesfaye; Tait, Karen; Barreau, Tracy; Copan, Lori; Roisman, Rachel; Jackson, Rebecca; Smorodinsky, Svetlana; Kreutzer, Richard A; Yip, Fuyuen; Wolkin, Amy

    2015-12-01

    Lake County, California, is in a high geothermal-activity area. Over the past 30 years, the city of Clearlake has reported health effects and building evacuations related to geothermal venting. Previous investigations in Clearlake revealed hydrogen sulfide at levels known to cause health effects and methane at levels that can cause explosion risks. The authors conducted an investigation in multiple cities and towns in Lake County to understand better the risk of geothermal venting to the community. They conducted household surveys and outdoor air sampling of hydrogen sulfide and methane and found community members were aware of geothermal venting and some expressed concerns. The authors did not, however, find hydrogen sulfide above the California Environmental Protection Agency air quality standard of 30 parts per billion over one hour or methane above explosive thresholds. The authors recommend improving risk communication, continuing to monitor geothermal gas effects on the community, and using community reports and complaints to monitor and document geothermal venting incidents. PMID:26738314

  3. Environmental Assessment for the proposed Induction Linac System Experiments in Building 51B at Lawrence Berkeley National Laboratory, Berkeley, California

    SciTech Connect

    1995-08-01

    The US Department of Energy (DOE) has prepared an Environmental Assessment (EA), (DOE/EA-1087) evaluating the proposed action to modify existing Building 51B at Lawrence Berkeley National Laboratory (LBNL) to install and conduct experiments on a new Induction Linear Accelerator System. LBNL is located in Berkeley, California and operated by the University of California (UC). The project consists of placing a pre-fabricated building inside Building 51B to house a new 10 MeV heavy ion linear accelerator. A control room and other support areas would be provided within and directly adjacent to Building 51B. The accelerator system would be used to conduct tests, at reduced scale and cost, many features of a heavy-ion accelerator driver for the Department of Energy`s inertial fusion energy program. Based upon information and analyses in the EA, the DOE has determined that the proposed action is not a major Federal action significantly affecting the quality of the human environment within the meaning of the National Environmental Policy Act of 1969. Therefore, an Environmental Impact Statement is not required. This report contains the Environmental Assessment, as well as the Finding of No Significant Impact (FONSI).

  4. Climatic change controls productivity variation in global grasslands.

    PubMed

    Gao, Qingzhu; Zhu, Wenquan; Schwartz, Mark W; Ganjurjav, Hasbagan; Wan, Yunfan; Qin, Xiaobo; Ma, Xin; Williamson, Matthew A; Li, Yue

    2016-01-01

    Detection and identification of the impacts of climate change on ecosystems have been core issues in climate change research in recent years. In this study, we compared average annual values of the normalized difference vegetation index (NDVI) with theoretical net primary productivity (NPP) values based on temperature and precipitation to determine the effect of historic climate change on global grassland productivity from 1982 to 2011. Comparison of trends in actual productivity (NDVI) with climate-induced potential productivity showed that the trends in average productivity in nearly 40% of global grassland areas have been significantly affected by climate change. The contribution of climate change to variability in grassland productivity was 15.2-71.2% during 1982-2011. Climate change contributed significantly to long-term trends in grassland productivity mainly in North America, central Eurasia, central Africa, and Oceania; these regions will be more sensitive to future climate change impacts. The impacts of climate change on variability in grassland productivity were greater in the Western Hemisphere than the Eastern Hemisphere. Confirmation of the observed trends requires long-term controlled experiments and multi-model ensembles to reduce uncertainties and explain mechanisms. PMID:27243565

  5. Climatic change controls productivity variation in global grasslands

    NASA Astrophysics Data System (ADS)

    Gao, Qingzhu; Zhu, Wenquan; Schwartz, Mark W.; Ganjurjav, Hasbagan; Wan, Yunfan; Qin, Xiaobo; Ma, Xin; Williamson, Matthew A.; Li, Yue

    2016-05-01

    Detection and identification of the impacts of climate change on ecosystems have been core issues in climate change research in recent years. In this study, we compared average annual values of the normalized difference vegetation index (NDVI) with theoretical net primary productivity (NPP) values based on temperature and precipitation to determine the effect of historic climate change on global grassland productivity from 1982 to 2011. Comparison of trends in actual productivity (NDVI) with climate-induced potential productivity showed that the trends in average productivity in nearly 40% of global grassland areas have been significantly affected by climate change. The contribution of climate change to variability in grassland productivity was 15.2–71.2% during 1982–2011. Climate change contributed significantly to long-term trends in grassland productivity mainly in North America, central Eurasia, central Africa, and Oceania; these regions will be more sensitive to future climate change impacts. The impacts of climate change on variability in grassland productivity were greater in the Western Hemisphere than the Eastern Hemisphere. Confirmation of the observed trends requires long-term controlled experiments and multi-model ensembles to reduce uncertainties and explain mechanisms.

  6. Climatic change controls productivity variation in global grasslands

    PubMed Central

    Gao, Qingzhu; Zhu, Wenquan; Schwartz, Mark W.; Ganjurjav, Hasbagan; Wan, Yunfan; Qin, Xiaobo; Ma, Xin; Williamson, Matthew A.; Li, Yue

    2016-01-01

    Detection and identification of the impacts of climate change on ecosystems have been core issues in climate change research in recent years. In this study, we compared average annual values of the normalized difference vegetation index (NDVI) with theoretical net primary productivity (NPP) values based on temperature and precipitation to determine the effect of historic climate change on global grassland productivity from 1982 to 2011. Comparison of trends in actual productivity (NDVI) with climate-induced potential productivity showed that the trends in average productivity in nearly 40% of global grassland areas have been significantly affected by climate change. The contribution of climate change to variability in grassland productivity was 15.2–71.2% during 1982–2011. Climate change contributed significantly to long-term trends in grassland productivity mainly in North America, central Eurasia, central Africa, and Oceania; these regions will be more sensitive to future climate change impacts. The impacts of climate change on variability in grassland productivity were greater in the Western Hemisphere than the Eastern Hemisphere. Confirmation of the observed trends requires long-term controlled experiments and multi-model ensembles to reduce uncertainties and explain mechanisms. PMID:27243565

  7. Decisions required for operating a maternal mortality review committee: the California experience.

    PubMed

    Main, Elliott K

    2012-02-01

    Maternal mortality is a current and important issue for obstetrics. The challenge is to structure case reviews so that they develop real data that can inform and direct quality improvement activities. In this article, we describe a series of decisions we have made in California to organize and run our maternal mortality review committee. These include defining the goal of the reviews, selection of cases, composition of the committee, basic review issues, and the definitions used for analysis (eg, cause of death, contributing factors, role of cesarean delivery, preventability, identifying quality improvement opportunities). It is expected that each maternal mortality review committee will have somewhat different approaches based on local resources and case mix. PMID:22280864

  8. Challenges with controlling varicella in prison settings: experience of California, 2010 to 2011.

    PubMed

    Leung, Jessica; Lopez, Adriana S; Tootell, Elena; Baumrind, Nikki; Mohle-Boetani, Janet; Leistikow, Bruce; Harriman, Kathleen H; Preas, Christopher P; Cosentino, Giorgio; Bialek, Stephanie R; Marin, Mona

    2014-10-01

    This article describes the epidemiology of varicella in one state prison in California during 2010 and 2011, control measures implemented, and associated costs. Eleven varicella cases were reported, of which nine were associated with two outbreaks. One outbreak consisted of three cases and the second consisted of six cases with two generations of spread. Among exposed inmates serologically tested, 98% (643/656) were varicella-zoster virus seropositive. The outbreaks resulted in > 1,000 inmates exposed, 444 staff exposures, and > $160,000 in costs. The authors documented the challenges and costs associated with controlling and managing varicella in a prison setting. A screening policy for evidence of varicella immunity for incoming inmates and staff and vaccination of susceptible persons has the potential to mitigate the impact of future outbreaks and reduce resources necessary to manage cases and outbreaks. PMID:25201912

  9. Challenges with controlling varicella in prison settings: Experience of California, 2010–2011

    PubMed Central

    Leung, Jessica; Lopez, Adriana S.; Tootell, Elena; Baumrind, Nikki; Mohle-Boetani, Janet; Leistikow, Bruce; Harriman, Kathleen H.; Preas, Christopher P.; Cosentino, Giorgio; Bialek, Stephanie R.; Marin, Mona

    2015-01-01

    We describe the epidemiology of varicella in one state prison in California during 2010–2011, control measures implemented, and associated costs. Eleven varicella cases were reported, 9 associated with 2 outbreaks. One outbreak consisted of 3 cases and the second consisted of 6 cases with 2 generations of spread. Among exposed inmates serologically tested, 98% (643/656) were VZV sero-positive. The outbreaks resulted in >1,000 inmates exposed, 444 staff exposures, and >$160,000 in costs. We documented the challenges and costs associated with controlling and managing varicella in a prison setting. A screening policy for evidence of varicella immunity for incoming inmates and staff and vaccination of susceptible persons has the potential to mitigate the impact of future outbreaks and reduce resources necessary for managing cases and outbreaks. PMID:25201912

  10. Disentangling root responses to climate change in a semiarid grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Future ecosystem properties of grasslands will be driven largely by belowground plant biomass responses to climate change, whose understanding has been limited by experimental and technical constraints. We use a multi-faceted approach and a factorial field experiment to explore impacts of elevated C...

  11. Species interaction mechanisms maintain grassland plant species diversity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Theory has outpaced empirical research in pursuit of identifying mechanisms maintaining species diversity. Here we demonstrate how data from diversity-ecosystem functioning experiments can be used to test maintenance of diversity theory. We predict that grassland plant diversity can be maintained by...

  12. Prescribed fire as an alternative measure in European grassland conservation

    NASA Astrophysics Data System (ADS)

    Valkó, Orsolya; Deák, Balázs; Török, Péter; Tóthmérész, Béla

    2015-04-01

    There are contrasting opinions on the perspectives of prescribed burning management in European grasslands. One hand, prescribed burning can be effectively used with relatively low implementation costs for the management of open landscapes, the reduction of accumulated litter or for decreasing the chance of wildfires. On the other hand burning can also have serious detrimental impacts on grassland ecosystems by promoting the dominance of some problem species (e.g. some competitors or invasive species) and by threatening endangered plant and animal species, especially invertebrates, thus, inappropriate burning can result in a loss of biodiversity in the long run. Our goal was to review the publications on the application of prescribed burning in European grasslands considering general (e.g. timing, frequency and duration) and specific (e.g. types of grasslands, effects on endangered species) circumstances. Even prescribed burning forms an integral part of the North-American grassland management practice, it is rarely applied in Europe, despite the fact that uncontrolled burning occurs frequently in some regions. According to the North-American experiences prescribed burning can be a viable solution for biodiversity conservation and can be a feasible solution for several nature conservation problems. We reviewed prescribed burning studies from Europe and North-America to identify findings which might be adapted to the European grassland conservation strategy. We found that not only the application of fire management is scarce in Europe but there is also a lack of published studies on this topic. European studies - contrary to the North-American practice - usually used yearly dormant-season burning, and concluded that this burning type solely is not feasible to preserve and maintain species-rich grasslands. In North-American grasslands, application of burning has a stronger historical, practical and scientific background; it is fine-tuned in terms of timing, frequency

  13. Sample data from a Distributed Acoustic Sensing experiment at Garner Valley, California (PoroTomo Subtask 3.2)

    DOE Data Explorer

    Chelsea Lancelle

    2013-09-10

    In September 2013, an experiment using Distributed Acoustic Sensing (DAS) was conducted at Garner Valley, a test site of the University of California Santa Barbara (Lancelle et al., 2014). This submission includes one 45 kN shear shaker (called “large shaker” on the basemap) test for three different measurement systems. The shaker swept from a rest, up to 10 Hz, and back down to a rest over 60 seconds. Lancelle, C., N. Lord, H. Wang, D. Fratta, R. Nigbor, A. Chalari, R. Karaulanov, J. Baldwin, and E. Castongia (2014), Directivity and Sensitivity of Fiber-Optic Cable Measuring Ground Motion using a Distributed Acoustic Sensing Array (abstract # NS31C-3935), AGU Fall Meeting. 
https://agu.confex.com/agu/fm1/meetingapp.cgi#Paper/19828 The e-poster is available at: https://agu.confex.com/data/handout/agu/fm14/Paper_19828_handout_696_0.pdf

  14. Avian assemblages on altered grasslands

    USGS Publications Warehouse

    Knopf, Fritz L.

    1994-01-01

    Grasslands comprise 17% of the North American landscape but provide primary habitat for only 5% of native bird species. On the Great Plains, grasslands include an eastern component of tall grasses and a western component of short grasses, both of which have been regionally altered by removing native grazers, plowing sod, draining wetlands, and encouraging woody vegetation. As a group, populations of endemic bird species of the grasslands have declined more than others (including neotropical migrants) in the last quarter century. Individually, populations of the Upland Sandpiper and McCown’s Longspur have increased; the wetlands-associated Marbled Godwit and Wilson’s Phalarope appear stable; breeding ranges are shifting for the Ferruginous Hawk, Mississippi Kite, Short-eared Owl, Upland Sandpiper, Horned Lark, Vesper, Savannah, and Henslow’s sparrows, and Western Meadowlark; breeding habitats are disappearing locally for Franklin’s Gull, Dickcissel, Henslow’s and Grasshopper sparrows. Lark Bunting, and Eastern Meadowlark; and populations are declining throughout the breeding ranges for Mountain Plover, and Cassin’s and Clay-colored sparrows. Declines of these latter three species, and also the Franklin’s Gull, presumably are due to ecological phenomena on their respective wintering areas. Unlike forest species that winter in the neotropics, most birds that breed in the North American grasslands also winter on the continent and problems driving declines in grassland species are associated almost entirely with North American processes. Contemporary programs and initiatives hold promise for the conservation of breeding habitats for these birds. Ecological ignorance of wintering habits and habitats clouds the future of the endemic birds of grasslands, especially those currently experiencing widespread declines across breeding locales.

  15. Ecosystem services and grasslands in America

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Historically, grasslands occupied a large portion of Canada and the USA throughout the Great Plains region east of the Rocky Mountains. Grasslands in the USA are valued for a wide range of ecosystem services, and provide a primary source of forage for grazing livestock. Unfortunately, grasslands a...

  16. 36 CFR 222.52 - National Grasslands.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 36 Parks, Forests, and Public Property 2 2010-07-01 2010-07-01 false National Grasslands. 222.52 Section 222.52 Parks, Forests, and Public Property FOREST SERVICE, DEPARTMENT OF AGRICULTURE RANGE MANAGEMENT Grazing Fees § 222.52 National Grasslands. Grazing fees for National Grasslands will...

  17. 36 CFR 222.52 - National Grasslands.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 36 Parks, Forests, and Public Property 2 2013-07-01 2013-07-01 false National Grasslands. 222.52 Section 222.52 Parks, Forests, and Public Property FOREST SERVICE, DEPARTMENT OF AGRICULTURE RANGE MANAGEMENT Grazing Fees § 222.52 National Grasslands. Grazing fees for National Grasslands will...

  18. 36 CFR 222.52 - National Grasslands.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 2 2011-07-01 2011-07-01 false National Grasslands. 222.52 Section 222.52 Parks, Forests, and Public Property FOREST SERVICE, DEPARTMENT OF AGRICULTURE RANGE MANAGEMENT Grazing Fees § 222.52 National Grasslands. Grazing fees for National Grasslands will...

  19. 36 CFR 222.52 - National Grasslands.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 36 Parks, Forests, and Public Property 2 2012-07-01 2012-07-01 false National Grasslands. 222.52 Section 222.52 Parks, Forests, and Public Property FOREST SERVICE, DEPARTMENT OF AGRICULTURE RANGE MANAGEMENT Grazing Fees § 222.52 National Grasslands. Grazing fees for National Grasslands will...

  20. 36 CFR 222.52 - National Grasslands.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 36 Parks, Forests, and Public Property 2 2014-07-01 2014-07-01 false National Grasslands. 222.52 Section 222.52 Parks, Forests, and Public Property FOREST SERVICE, DEPARTMENT OF AGRICULTURE RANGE MANAGEMENT Grazing Fees § 222.52 National Grasslands. Grazing fees for National Grasslands will...

  1. Plant diversity effects on grassland productivity are robust to both nutrient enrichment and drought

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Global change drivers are rapidly altering resource availability and reducing biodiversity. Here, we evaluate the extent to which biodiversity influences the response of ecosystem productivity to increases or decreases in resource availability across grassland experiments. This was done using data...

  2. A transparent oversight policy for human anatomical specimen management: the University of California, Davis experience.

    PubMed

    Schmitt, Brandi; Wacker, Charlotte; Ikemoto, Lisa; Meyers, Frederick J; Pomeroy, Claire

    2014-03-01

    The authors describe the development and implementation of a University of California (UC) system of oversight, education, tracking, and accountability for human anatomical specimen use in education and research activities. This program was created and initially implemented at UC Davis in 2005. Several incidents arising out of the handling of human anatomical specimens at UC campuses revealed significant challenges in the system for maintaining control of human anatomical specimens used in education and research. These events combined to undermine the public perception for research and educational endeavors involving anatomical materials at public institutions. Risks associated with the acquisition, maintenance, and disposal of these specimens were not fully understood by the faculty, staff, and students who used them. Laws governing sources of specimens are grouped with those that govern organ procurement and tissue banking, and sometimes are found in cemetery and funeral regulations. These variables complicate interpretations and may hinder compliance. To regain confidence in the system, the need to set appropriate and realistic guidelines that mitigate risk and facilitate an institution's research and educational mission was identified. This article chronicles a multiyear process in which diverse stakeholders developed (1) a regulatory policy for oversight, (2) a policy education program, (3) procedures for tracking and accountability, and (4) a reporting and enforcement mechanism for appropriate and ethical use of human anatomical specimens in university education and research. PMID:24448034

  3. Acid mine drainage on public and private lands, the Walker Mine experience, Plumas County, California

    SciTech Connect

    Croyle, W.A.; Rosenbaum, S.E.

    1996-11-01

    A widespread environmental problem associated with abandoned mines and their tailings is acid mine drainage (AMD). AMID typically has low pH and elevated metal concentrations that are toxic to aquatic life. In Northern California, Iron Mountain and other mines in the Shasta mining districts are the largest sources of AMD. Additional sources lie to the south along a discontinuous belt of copper and zinc mineralization in the western Sierra foothills. Between these areas lies a remote group of copper mines in northeastern Plumas County including the Walker, Engels and Superior mines. Of this group, AMD from Walker Mine has caused the most severe water quality impairment. This paper describes the history and environmental setting of Walker Mine and the approaches used by the Central Valley Regional Water Quality Control Board, a state regulatory agency, to improve water quality at the site. Both the mine and its tailings contribute pollutants to the watershed. The mine has a portal discharge with depressed pH and high copper concentrations. The tailings add fine grained sediment to the creek and generate low but significant concentrations of dissolved copper. The mine is on private property and the tailings are on land managed by the U. S. Forest Service. Because of these differences in pollution problems and ownership, the methods employed by the Regional Board to improve conditions at the mine and tailings have been on different, but parallel tracks. Monitoring shows these efforts have significantly improved water quality in the watershed over the last 10 years.

  4. The fluorescent tracer experiment on Holiday Beach near Mugu Canyon, Southern California

    USGS Publications Warehouse

    Kinsman, Nicole; Xu, J. P.

    2012-01-01

    After revisiting sand tracer techniques originally developed in the 1960s, a range of fluorescent coating formulations were tested in the laboratory. Explicit steps are presented for the preparation of the formulation evaluated to have superior attributes, a thermoplastic pigment/dye in a colloidal mixture with a vinyl chloride/vinyl acetate copolymer. In September 2010, 0.59 cubic meters of fluorescent tracer material was injected into the littoral zone about 4 kilometers upcoast of Mugu submarine canyon in California. The movement of tracer was monitored in three dimensions over the course of 4 days using manual and automated techniques. Detailed observations of the tracer's behavior in the coastal zone indicate that this tracer successfully mimicked the native beach sand and similar methods could be used to validate models of tracer movement in this type of environment. Recommendations including how to time successful tracer studies and how to scale the field of view of automated camera systems are presented along with the advantages and disadvantages of the described tracer methodology.

  5. Sediment-transport events on the northern California continental shelf during the 1990-1991 STRESS experiment

    USGS Publications Warehouse

    Sherwood, C.R.; Butman, B.; Cacchione, D.A.; Drake, D.E.; Gross, T.F.; Sternberg, R.W.; Wiberg, P.L.; Williams, A. J., III

    1994-01-01

    Measurements of currents and light transmission were made at bottom tripods and moorings arrayed across the northern California continental shelf along the Coastal Ocean Dynamics Experiment (CODE) "C" transect as part of the 1990-1991 Sediment Transport Events on Shelves and Slopes (STRESS) experiment. In combination with meteorological and wave data from the National Data Buoy Center Buoy 46013, these measurements provide information about the physical forcing and resultant resuspension and transport of bottom material between 21 November and 8 March. Sixteen events were identified in the wave, wind and current-meter records for this period. Only two were local storms with southerly winds, but they caused about half of the seasonal net transport. Seven were swell events that combined long-period waves generated by distant storms with local currents. At the 90-m site, swells interacted with the mean northward flow to produce northward transport. During six northerly wind events, upwelling-favorable winds often were sufficient to slow or reverse the mean northward flow and thus caused southward transport. A single current event, which produced moderate southward transport, was observed at the 130-m site. Net transport during the winter experiment was offshore at all sites, northward at the inner- and mid-shelf sites, but southward at the outer-shelf site. The results suggest that local storms with southerly winds may dominate seasonal transport, as on the Washington shelf, but significant transport also can occur during fair weather and during periods of northerly winds. ?? 1994.

  6. Childhood Experiences and Psychosocial Influences on HIV Risk among Adolescent Latinas in Southern California.

    ERIC Educational Resources Information Center

    Newcomb, Michael D.; Locke, Thomas F.; Goodyear, Rodney K.

    2003-01-01

    This study determined how adverse childhood experiences influenced risky sexual behavior in a community sample of Latina adolescents in Los Angeles. Psychosocial, sociocultural, and environmental mediators of the relations between childhood experiences and risky sexual behavior were tested. Childhood maltreatment was associated with risky sexual…

  7. Professional Leadership Experiences with Formal and Informal Mentoring of College Deans of Education at 4-Year Nonprofit Private Colleges and Universities in California

    ERIC Educational Resources Information Center

    Baartman, Ingrid

    2011-01-01

    Purpose: The purpose of this study was to examine professional leadership experiences of college deans of education with formal and informal mentoring in the course of their career progression at 4-year nonprofit private colleges and universities in California. Methodology: Using a mixed-methods approach that emphasized the qualitative data…

  8. UCI Alumni and Their Careers. A Survey of the Graduate Training and Work Experience of the First Decade of the University of California, Irvine Alumni.

    ERIC Educational Resources Information Center

    California Univ., Irvine. Student Affairs Office of Studies and Research.

    The career and educational experiences of the baccalaureate degree recipients of the University of California at Irvine (UCI) during the first decade of its existence, 1965-74, were studied. A response from 2,479 alumni, or 51 percent, provided information concerning: (1) educational attainment; (2) initial employment after graduation; and (3)…

  9. Resurvey of site stability quadrilaterals, Otay Mountain and Quincy, California. [San Andreas fault experiment

    NASA Technical Reports Server (NTRS)

    Scholz, C. H.

    1977-01-01

    Trilateration quadrilaterals established across two faults near the San Andreas Fault Experiment laser/satellite ranging sites were resurveyed after four years. No evidence of significant tectonic motion was found.

  10. Native shrub reestablishment in exotic annual grasslands: do ecosystem processes recover?

    PubMed

    Yelenik, S G; Levine, J M

    2010-04-01

    The impacts of exotic plant species on ecosystem processes are well established, motivating numerous efforts to facilitate native-species recovery. Nonetheless, how the return of native species influences ecosystem processes and how these changes feed back to influence the recovery process are poorly understood. We examined these questions in exotic annual grasslands on Santa Cruz Island, California, USA, where the removal of nonnative herbivores has led to the recovery of the native shrubs Artemisia californica and Eriogonum arborescens. To examine the influence of shrub colonization on nutrient cycling, and the mechanisms by which these changes arise, we measured available nitrogen and phosphorus, and quantified nitrogen mineralization and litterfall rates under shrubs and grasses in the field and in experimental monoculture plots. Both native shrubs altered nitrogen cycling as they colonized the grassland, but they did so in opposite directions. Eriogonum depressed nitrogen pools and mineralization rates via large inputs of nitrogen-poor litter. In contrast Artemisia increased nitrogen and phosphorus pools and nitrogen mineralization rates. Last, to determine if shrub effects on soils favor shrubs or grasses, we conducted a nitrogen and phosphorus fertilization experiment in the field. Only the exotic grass was significantly limited by nitrogen. Thus the depressed nitrogen availability associated with Eriogonum colonization is more harmful to exotic grasses than to the native shrub. By contrast, the elevated nitrogen associated with recovering Artemisia favors grasses over the shrub, possibly hindering recovery of the native. Mechanistic studies of the ecosystem ,impacts of native-plant recovery are useful for managers wishing to predict which native species return ecosystem function, and whether such changes feed back to influence native recovery. PMID:20437958

  11. Effect of phosphorus availability on the selection of species with different ploidy levels and genome sizes in a long-term grassland fertilization experiment.

    PubMed

    Šmarda, Petr; Hejcman, Michal; Březinová, Alexandra; Horová, Lucie; Steigerová, Helena; Zedek, František; Bureš, Petr; Hejcmanová, Pavla; Schellberg, Jürgen

    2013-11-01

    Polyploidy and increased genome size are hypothesized to increase organismal nutrient demands, namely of phosphorus (P), which is an essential and abundant component of nucleic acids. Therefore, polyploids and plants with larger genomes are expected to be selectively disadvantaged in P-limited environments. However, this hypothesis has yet to be experimentally tested. We measured the somatic DNA content and ploidy level in 74 vascular plant species in a long-term fertilization experiment. The differences between the fertilizer treatments regarding the DNA content and ploidy level of the established species were tested using phylogeny-based statistics. The percentage and biomass of polyploid species clearly increased with soil P in particular fertilizer treatments, and a similar but weaker trend was observed for the DNA content. These increases were associated with the dominance of competitive life strategy (particularly advantageous in the P-treated plots) in polyploids and the enhanced competitive ability of dominant polyploid grasses at high soil P concentrations, indicating their increased P limitation. Our results verify the hypothesized effect of P availability on the selection of polyploids and plants with increased genome sizes, although the relative contribution of increased P demands vs increased competitiveness as causes of the observed pattern requires further evaluation. PMID:23819630

  12. A Study of PM2.5 Formation in Central California during 2013 Discover-AQ Field Experiment

    NASA Astrophysics Data System (ADS)

    Soong, S. T.; Jia, Y.; Fairley, D.; Tran, C.; Matsuoka, J.; Cordova, J.; Tanrikulu, S.

    2015-12-01

    Five high PM2.5 episodes occurred in the Central Valley of California in January and February, 2013. Two of these episodes took place during the 2013 Discover-AQ field experiment. We used observations and CMAQ model simulations to study PM2.5 formation during these episodes. The study domain covered all of central and portions of northern California. Analyses were conducted with special emphasis on the differences on the meteorology and PM2.5 components over three sub-regions: the San Francisco Bay Area (SFBA), the Sacramento area (SAC), and the San Joaquin Valley area (SJV). The CMAQ had 15 vertical layers and 4 km horizontal grid resolution. The SAPRC99 chemical and AE5 aerosol mechanisms were used in the simulations. Meteorological inputs to CMAQ were generated using the WRF model. An available 2012 emissions inventory was used for 2013 simulations. In all three sub-regions, the WRF model slightly under predicted wind speed while correctly predicted the wind direction. The predicted boundary layer thickness had good correlation with observed average PM2.5 concentrations, especially in SJV. The CMAQ model reproduced all five high PM2.5 episodes. The predicted PM2.5 almost matched the observed values in the SFBA. For the two episodes captured by the Discover-AQ field experiment, CMAQ under predicted PM2.5 in the SJV area This under prediction may be attributed to the thickness of the first layer of CMAQ, which is about 32 m. The nighttime PBL height computed by WRF can be as low as 15 m in SJV during this period. There were considerable differences in the ratio of primary to secondary PM2.5 among in the three sub-regions. Secondary PM2.5 averaged 27% of total PM2.5 in SFBA. The corresponding ratio was 36% in SAC and 45% in SJV. The biggest component of secondary PM2.5 in SJV was ammonium nitrate, which is consistent with large ammonia emissions there from dairy and feedlot operations. We found large sensitivity of CMAQ simulated PM2.5 to the model layer structure

  13. Effects of subalpine grassland management on hydrology and vegetation productivity

    NASA Astrophysics Data System (ADS)

    Fatichi, Simone; Zeeman, Matthias; Fuhrer, Jürg; Burlando, Paolo

    2014-05-01

    Grassland and pastures are very typical land uses in subalpine and alpine environments. Grass is typically subjected to management practices that can change the biophysical structure of the plant canopy through defoliation and alter soil hydraulic properties. These changes are expected to impact hydrological and energy fluxes as well as vegetation primary productivity. In this study a mechanistic model is used to investigate the effects of management practices (grass cut, grazing, and the consequent soil compaction due to treading by animals) on water and carbon dynamics. The model is first confirmed using energy, water, and carbon fluxes measured at three eddy covariance stations above grasslands in Switzerland and discharge measured in a small experimental catchment. Successively, a series of virtual experiments are conceived to elucidate the impacts of management scenarios at the plot and catchment scales. Numerical results show that only the most severe management actions such as low grass cuts or heavy grazing intensities are able to influence the long-term hydrological behavior. Moderate grassland management practices are unlikely to be effective in modifying the system both at the local and catchment scale. An important exception is represented by the short-term effect of soil compaction that can reduce infiltration capacity leading to peak flow considerably higher than in undisturbed conditions. The productivity of vegetation in absence of nutrient limitation is affected by the different management scenarios with tolerable disturbances that lead to higher aboveground net primary production. Such a result can have important consequences in terms of grassland management planning.

  14. Estimation of rainfall interception in grassland using eddy flux measurements

    NASA Astrophysics Data System (ADS)

    Maruyama, A.; Miyazawa, Y.; Inoue, A.

    2014-12-01

    Rainfall interception plays an important role in the water cycle in natural ecosystems. Interception by the forest canopies have been widely observed or estimated over various ecosystems, such as tropical rainforest, evergreen forest and deciduous forest. However interception by the short canopies, e.g. shrubby plant, grassland and crop, has been rarely observed since it has been difficult to obtain reliable precipitation measurements under the canopy. In this study, we estimated monthly and annual rainfall interception in grassland using evapotranspiration data of eddy flux measurements. Experiments were conducted in grassland (Italian ryegrass) from 2010 to 2012 growing season in Kumamoto, Japan. Evapotranspiration (latent heat flux) were observed throughout the year based on the eddy covariance technique. A three dimensional sonic anemometer and an open path CO2/H2O analyzer were used to calculate 30 min flux. Other meteorological factors, such as air temperature, humidity and solar radiation, were also observed. Rainfall interception was estimated as follows. 1) Using evapotranspiration data during dry period, environmental response of surface conductance (gc) was inversely calculated based on the big-leaf model. 2) Evapotranspiration without interception during precipitation period was estimated using above model and environmental response of gc. 3) Assuming that evaporation of intercepted rainfall is equal to the difference in evapotranspiration between above estimation and actual measurements, rainfall interception was estimated over experimental period. The account of rainfall interception in grassland using this technique will be presented at the meeting.

  15. A Gravity data along LARSE (Los Angeles Regional Seismic Experiment) Line II, Southern California

    USGS Publications Warehouse

    Wooley, R.J.; Langenheim, V.E.

    2001-01-01

    The U.S. Geological Survey conducted a detailed gravity study along part of the Los Angeles Regional Seismic Experiment (LARSE) transect across the San Fernando Basin and Transverse Ranges to help characterize the structure underlying this area. 249 gravity measurements were collected along the transect and to augment regional coverage near the profile. An isostatic gravity low of 50-60 mGal reflects the San Fernando-East Ventura basin. Another prominent isostatic gravity with an amplitude of 30 mGal marks the Antelope Valley basin. Gravity highs occur over the Santa Monica Mountains and the Transverse Ranges. The highest isostatic gravity values coincide with outcrops of Pelona schist.

  16. Effect of grassland vegetation type on the responses of hydrological processes to seasonal precipitation patterns

    NASA Astrophysics Data System (ADS)

    Salve, Rohit; Sudderth, Erika A.; St. Clair, Samuel B.; Torn, Margaret S.

    2011-11-01

    SummaryUnder future climate scenarios, rainfall patterns and species composition in California grasslands are predicted to change, potentially impacting soil-moisture dynamics and ecosystem function. The primary objective of this study was to assess the impact of altered rainfall on soil-moisture dynamics in three annual grassland vegetation types. We monitored seasonal changes in soil moisture under three different rainfall regimes in mesocosms planted with: (1) a mixed forb-grass community, (2) an Avena barbata monoculture, and (3) an Erodium botrys monoculture. We applied watering treatments in pulses, followed by dry periods that are representative of natural rainfall patterns in California annual grasslands. While rainfall was the dominant treatment, its impact on hydrological processes varied over the growing season. Surprisingly, there were only small differences in the hydrologic response among the three vegetation types. We found significant temporal variability in evapotranspiration, seepage, and soil-moisture content. Both Water Use Efficiency (WUE) and Rain Use Efficiency (RUE) decreased as annual precipitation totals increased. Results from this investigation suggest that both precipitation and vegetation have a significant interactive effect on soil-moisture dynamics. When combined, seasonal precipitation and grassland vegetation influence near-surface hydrology in ways that cannot be predicted from manipulation of a single variable.

  17. Calibration formulae and values for velocity seismometers used in the 1998 Santa Clara Valley, California seismic experiment

    USGS Publications Warehouse

    Lindh, Allan G.; Eaton, Jerry P.; O'Neill Allen, Mary; Healy, John H.; Stewart, Samuel W.; Damerell, Lu

    1999-01-01

    Eaton (1975), Bakun and Dratler (1976), Eaton (1977), Healy and O’Neil (1977), Asten (1977), Stewart and O'Neill (1980), Liu and Peselnick (1986), Eaton (1991), Rodgers et al. (1995), and many others (see Asten (1977) for a list of earlier references) have presented formulae for calculating the damped generator constant (or motor constant), and the damping constant (or fractional damping ratio) for magnetically damped velocity seismometers. Unfortunately the notation varies between authors, and not all the formulae allow for some of the significant variables -- differences in input impedance of the recording system in particular. This has become particularly relevant because the USGS seismic networks in California have traditionally set up their velocity sensors for the 10K Ohm impedance of the standard USGS analog telemetry systems (Eaton, 1977), but modern digital recording systems are usually set up with high input impedances, often of a megaohm or greater. Thus the nominal calibration values valid for USGS velocity sensors in their “normal” configuration are incorrect when they are recorded on other systems. In this short note we have collected the relevant formulae needed, and computed the seismometer responses for the various velocity sensors used in the recent Santa Clara Valley Seismic Experiment (SCVSE, see Lindh et al., 1999).

  18. Effects of interactive global changes on methane uptake in an annual grassland

    NASA Astrophysics Data System (ADS)

    Blankinship, Joseph C.; Brown, Jamie R.; Dijkstra, Paul; Hungate, Bruce A.

    2010-06-01

    The future size of the terrestrial methane (CH4) sink of upland soils remains uncertain, along with potential feedbacks to global warming. Much of the uncertainty lies in our lack of knowledge about potential interactive effects of multiple simultaneous global environmental changes. Field CH4 fluxes and laboratory soil CH4 consumption were measured five times during 3 consecutive years in a California annual grassland exposed to 8 years of the full factorial combination of ambient and elevated levels of precipitation, temperature, atmospheric CO2 concentration, and N deposition. Across all sampling dates and treatments, increased precipitation caused a 61% reduction in field CH4 uptake. However, this reduction depended quantitatively on other global change factors. Higher precipitation reduced CH4 uptake when temperature or N deposition (but not both) increased, and under elevated CO2 but only late in the growing season. Warming alone also decreased CH4 uptake early in the growing season, which was partly explained by a decrease in laboratory soil CH4 consumption. Atmospheric CH4 models likely need to incorporate nonadditive interactions, seasonal interactions, and interactions between methanotrophy and methanogenesis. Despite the complexity of interactions we observed in this multifactor experiment, the outcome agrees with results from single-factor experiments: an increased terrestrial CH4 sink appears less likely than a reduced one.

  19. Airborne In-Situ Measurements of Formaldehyde over California: First Results from the Compact Formaldehyde Fluorescence Experiment (COFFEE) Instrument

    NASA Technical Reports Server (NTRS)

    Marrero, Josette; St. Clair, Jason; Yates, Emma L.; Gore, Warren; Swanson, Andrew K.; Iraci, Laura T.; Hanisco, Thomas F.

    2016-01-01

    Formaldehyde (HCHO) is one of the most abundant oxygenated volatile organic compounds (VOCs) in the atmosphere, playing a role multiple atmospheric processes. Measurements of HCHO can be used to help quantify convective transport, the abundance of VOCs, and ozone production in urban environments. The Compact Formaldehyde FluorescencE Experiment (COFFEE) instrument uses Non-Resonant Laser Induced Fluorescence (NR-LIF) to detect trace concentrations of HCHO as part of the Alpha Jet Atmospheric eXperiment (AJAX) payload. Developed at NASA GSFC, COFFEE is a small, low maintenance instrument with a sensitivity of 100 pptv and a quick response time (1 sec). The COFFEE instrument has been customized to fit in an external wing pod on the Alpha Jet aircraft based at NASA ARC. The instrument can operate over a broad range of altitudes, from boundary layer to lower stratosphere, making it well suited for the Alpha Jet, which can access altitudes from the surface up to 40,000 ft. Results of the first COFFEE science flights preformed over the California's Central Valley will be presented. Boundary layer measurements and vertical profiles in the tropospheric column will both be included. This region is of particular interest, due to its elevated levels of HCHO, revealed in satellite images, as well as its high ozone concentrations. In addition to HCHO, the AJAX payload includes measurements of atmospheric ozone, methane, and carbon dioxide. Formaldehyde is one of the few urban pollutants that can be measured from space. Plans to compare in-situ COFFEE data with satellite-based HCHO observations such as those from OMI (Aura) and OMPS (SuomiNPP) will also be presented.

  20. Airborne In-Situ Measurements of Formaldehyde Over California: First Results from the Compact Formaldehyde Fluorescence Experiment (COFFEE) Instrument

    NASA Technical Reports Server (NTRS)

    Marrero, Josette Elizabeth; Saint Clair, Jason; Yates, Emma L.; Gore, Warren; Swanson, Andrew K.; Iraci, Laura T.; Hanisco, Thomas F.

    2016-01-01

    Formaldehyde (HCHO) is one of the most abundant oxygenated volatile organic compounds (VOCs) in the atmosphere, playing a role multiple atmospheric processes. Measurements of HCHO can be used to help quantify convective transport, the abundance of VOCs, and ozone production in urban environments. The Compact Formaldehyde FluorescencE Experiment (COFFEE) instrument uses Non-Resonant Laser Induced Fluorescence (NR-LIF) to detect trace concentrations of HCHO as part of the Alpha Jet Atmospheric eXperiment (AJAX) payload. Developed at NASA GSFC, COFFEE is a small, low maintenance instrument with a sensitivity of 100 pptv and a quick response time (1 sec). The COFFEE instrument has been customized to fit in an external wing pod on the Alpha Jet aircraft based at NASA ARC. The instrument can operate over a broad range of altitudes, from boundary layer to lower stratosphere, making it well suited for the Alpha Jet, which can access altitudes from the surface up to 40,000 ft. Results of the first COFFEE science flights preformed over the California's Central Valley will be presented. Boundary layer measurements and vertical profiles in the tropospheric column will both be included. This region is of particular interest, due to its elevated levels of HCHO, revealed in satellite images, as well as its high ozone concentrations. In addition to HCHO, the AJAX payload includes measurements of atmospheric ozone, methane, and carbon dioxide. Formaldehyde is one of the few urban pollutants that can be measured from space. Plans to compare in-situ COFFEE data with satellite-based HCHO observations such as those from OMI (Aura) and OMPS (SuomiNPP) will also be presented.

  1. Current and Future Impacts of Atmospheric Nitrogen Deposition on Grassland GHG Balance

    NASA Astrophysics Data System (ADS)

    Hudiburg, T. W.; Gomez-Casanovas, N.; Bernacchi, C.; DeLucia, E. H.

    2014-12-01

    Nitrogen deposition (Ndep), a consequence of human activities, affects the greenhouse gas (GHG; CO2, N2O and CH4) sink capacity of terrestrial ecosystems. Grasslands play an important role in determining the concentration of GHGs in the atmosphere. While they store greater than 10% of terrestrial net primary productivity and sustain up to 30% of the world's organic C in their soils, grasslands also may be responsible for significant CH4 and N2O emissions. Many fertilization experiments have examined the response of grasslands to N loads of 50 to 100 kg N ha-1 yr-1. However, few studies have been designed to examine ecosystem responses to low N loads (< 20 kg N ha-1 yr-1) which they are likely to experience in the future according to the new IPCC representative concentration pathway (RCP) scenarios. This is consistent with the notion that the N saturation threshold at which Net Ecosystem Productivity (NEP) levels off, or the dose-response relationships between N2O, N-trace gases, CH4, and Ndep in grasslands have not being well characterized. We combined data from grassland ecosystems in major climate zones and biogeochemical modeling (DayCent v. 4.5) to characterize the dose-response relationship between increased Ndep and GHG, and other N-trace gases fluxes and N leaching of these grasslands. We used the synthesized data to evaluate the modeling for above- and belowground NPP, N2O, CH4, and response to N fertilization and climate. We found that in most cases increased Ndep will continue to increase the non-CO2 GHG source strength of grasslands, whereas NEP will saturate at N levels ranging from 10 - 70 kg N ha-1 yr-1depending on the precipitation, fire regime, and/or species composition of the grassland. Given these thresholds, we modeled the potential net GHG sink capacity for the world's major grassland biomes using several of the IPCC RCP scenarios which include a range of climate and Ndep trajectories. Our results suggest that although global grassland C

  2. Songbird abundance in native and planted grassland varies with type and amount of grassland in the surrounding landscape

    USGS Publications Warehouse

    Davis, Stephen K.; Fisher, Ryan; Skinner, Susan; Shaffer, Terry L.; Brigham, R. Mark

    2013-01-01

    Agriculture and wildlife conservation programs have converted vast amounts of cropland into grasslands planted with exotic species. Understanding how landscape context influences avian use of native and planted grasslands is essential for developing effective conservation strategies in agricultural landscapes. Our primary objective was to determine the extent to which the amount and type of grassland in the surrounding landscape influences the abundance of grassland songbird species on native and planted grassland parcels in southern Saskatchewan and Alberta, Canada. Bird abundance was more strongly influenced by the amount and type of grassland within 400 m of breeding parcels than at larger spatial scales. Grassland specialists responded similarly to habitat and landscape type over both years and provinces. Sprague's pipit (Anthus spragueii) and Baird's sparrow (Ammodramus bairdii) were most common in native grassland parcels surrounded by native grassland and were more likely to occur in planted grasslands surrounded by native grassland. Bobolinks (Dolichonyx oryzivorus) were most common in planted grassland parcels, but their abundance increased with the amount of native grassland surrounding these parcels. Our findings indicate that the suitability of planted grasslands for these species is influenced by their proximity to native grassland. Grassland generalists showed mixed responses to habitat and landscape type over the 2 years (Le Conte's sparrow [Ammodramus leconteii]) and between provinces (Savannah sparrow [Passerculus sandwichensis] and western meadowlark [Sturnella neglecta]). Management to benefit grassland specialists should therefore consider the landscape context when seeding cultivated land to non-native grassland and conserve extant native grassland.

  3. Rocky 7 prototype Mars rover field geology experiments 1. Lavic Lake and sunshine volcanic field, California

    USGS Publications Warehouse

    Arvidson, R. E.; Acton, C.; Blaney, D.; Bowman, J.; Kim, S.; Klingelhofer, G.; Marshall, J.; Niebur, C.; Plescia, J.; Saunders, R.S.; Ulmer, C.T.

    1998-01-01

    Experiments with the Rocky 7 rover were performed in the Mojave Desert to better understand how to conduct rover-based, long-distance (kilometers) geological traverses on Mars. The rover was equipped with stereo imaging systems for remote sensing science and hazard avoidance and 57Fe Mo??ssbauer and nuclear magnetic resonance spectrometers for in situ determination of mineralogy of unprepared rock and soil surfaces. Laboratory data were also obtained using the spectrometers and an X ray diffraction (XRD)/XRF instrument for unprepared samples collected from the rover sites. Simulated orbital and descent image data assembled for the test sites were found to be critical for assessing the geologic setting, formulating hypotheses to be tested with rover observations, planning traverses, locating the rover, and providing a regional context for interpretation of rover-based observations. Analyses of remote sensing and in situ observations acquired by the rover confirmed inferences made from orbital and simulated descent images that the Sunshine Volcanic Field is composed of basalt flows. Rover data confirmed the idea that Lavic Lake is a recharge playa and that an alluvial fan composed of sediments with felsic compositions has prograded onto the playa. Rover-based discoveries include the inference that the basalt flows are mantled with aeolian sediment and covered with a dense pavement of varnished basalt cobbles. Results demonstrate that the combination of rover remote sensing and in situ analytical observations will significantly increase our understanding of Mars and provide key connecting links between orbital and descent data and analyses of returned samples. Copyright 1998 by the American Geophysical Union.

  4. Quantifying reflectance anisotropy of photosynthetically active radiation in grasslands

    SciTech Connect

    Middleton, E.M. )

    1992-11-30

    This work is part of the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE), an international land-surface-atmosphere experiment aimed at improving the way climate models represent energy, water, heat, and carbon exchanges, and improving the utilization of satellite based remote sensing to monitor such parameters. This paper reports on a study to quantify the reflectance anisotropy of the photosynthetically active radiation (PAR) for grasslands. PAR falls in the wavelength range 0.4 to 0.7[mu]m. The study looks at the variation of PAR with illumination and vegetative canopy conditions. It uses bidirectional reflectance distribution function data, and measures of anisotropy derived from reflectance factor and reflectance fraction data to aid in the analysis. The data used for this analysis came from an intense effort mounted to measure diurnal changes in the anisotropy of surface reflectance from prairie grassland as a function of the vegetative canopy.

  5. Components of surface energy balance in a temperate grassland ecosystem

    NASA Technical Reports Server (NTRS)

    Kim, Joon; Verma, Shashi B.

    1990-01-01

    Eddy correlation measurements of moisture, heat, and momentum fluxes were made at a tall grassland site in Kansas during the First International Satellite Land Surface Climatology Project Field Experiment. The fluxes, stomatal conductance, and leaf water potential of three grass species are reported. The species are big bluestem, indiangrass, and switchgrass. The daily and seasonal variation in the components of the surface energy balance and the aerodynamic and canopy surface conductances for prairie vegetation are examined.

  6. Selenium and boron in aquatic birds from central California

    USGS Publications Warehouse

    Paveglio, F.L.; Bunck, C.M.; Heinz, G.H.

    1992-01-01

    Subsurface agricultural drainwater used for marsh management has resulted in trace element contamination of aquatic bird food chains in central California. Consequently, we collected breeding and wintering aquatic birds from the Grassland Water District (GWD) of California during 1985-88 to measure selenium (Se) and boron (B) contamination resulting from use of such drainage water for wetland management. During the breeding and wintering periods, livers of birds from the North and South areas of the Grasslands contained concentrations of Se and B that have been associated with reproductive impairment. Birds from the South Grasslands, which had received more undiluted drainage water, were more contaminated than those from the North Grasslands. Birds had higher (P < 0.001) levels of Se and B at the end of the 1985-86 wintering period than at the beginning, indicating that the Grasslands was the major source of contamination. Concentrations of Se decreased from 1985 through 1988, after freshwater was substituted for irrigation drainage water during autumn 1985. B concentrations in wintering birds, except for American coots (Fulica americana), declined to background levels, while concentrations in breeding birds remained slightly elevated. However, after 3 years of freshwater management of the Grasslands, liver Se levels in some breeding and wintering birds still were above concentrations associated with impaired reproduction in laboratory and field studies. In areas with high potential for leaching of Se and B from agricultural land, irrigation drainage water should not be used for wetland management.

  7. Interactive effects of grazing, drought, and fire on grassland plant communities in North America and South Africa.

    PubMed

    Koerner, Sally E; Collins, Scott L

    2014-01-01

    Grazing, fire, and climate shape mesic grassland communities. With global change altering all three factors, understanding how grasslands respond to changes in these combined drivers may aid in projecting future changes in grassland ecosystems. We manipulated rainfall and simulated grazing (clipping) in two long-term fire experiments in mesic grasslands in North America (NA) and South Africa (SA). Despite their common drivers, grasslands in NA and SA differ in evolutionary history. Therefore, we expected community structure and production in NA and SA to respond differently to fire, grazing, and drought. Specifically, we hypothesized that NA plant community composition and production would be more responsive than the SA plant communities to changes in the drivers and their interactions, and that despite this expected stability of SA grasslands, drought would be the dominant factor controlling production, but grazing would play the primary role in determining community composition at both sites. Contrary to our hypothesis, NA and SA grasslands generally responded similarly to grazing, drought, and fire. Grazing increased diversity, decreased grass cover and production, and decreased belowground biomass at both sites. Drought alone minimally impacted plant community structure, and we saw similar treatment interactions at the two sites. Drought was not the primary driver of grassland productivity, but instead drought effects were similar to or less than grazing and fire. Even though these grasslands differed in evolutionary history, they responded similarly to our fire, grazing, and climate manipulations. Overall, we found community and ecosystem convergence in NA and SA grasslands. Grazing and fire are as important as climate in controlling mesic grassland ecosystems on both continents. PMID:24649650

  8. Seismic mapping of shallow fault zones in the San Gabriel Mountains from the Los Angeles Region Seismic Experiment, southern California

    USGS Publications Warehouse

    Fuis, G.S.; Ryberg, T.; Lutter, W.J.; Ehlig, P.L.

    2001-01-01

    During the Los Angeles Region Seismic Experiment (LARSE), a reflection/refraction survey was conducted along a profile (line 1) extending from Seal Beach, California, northeastward to the Mojave Desert and crossing the Los Angeles and San Gabriel Valley basins and San Gabriel Mountains. In most shot gathers from the southern and central San Gabriel Mountains, clear secondary arrivals are seen that merge, or appear to merge, with first arrivals at three locations, including the location of the Vincent thrust fault, an exposed late Mesozoic/early Cenozoic megathrust. These secondary arrivals are interpretable as reflections in the shallow crust (<5 km depth) from a concave-upward interface that projects to the surface in the north near the Vincent thrust fault, is offset in its central part at the San Gabriel fault (an old branch of the San Andreas fault), and terminates in the south at 1 to 2 km depth at the southern mountain front. The velocity structure above and below this interface strongly suggests it is the Vincent thrust fault: intermediate velocities (6.2 km/s), consistent with mylonites overlying the Vincent thrust fault, are observed above it; lower velocities (5.8 km/s), consistent with the Pelona Schist underlying the Vincent thrust fault, are observed below it. Problems arise, however, in attempting to match this reflector to the exposed Vincent thrust fault, which is seen in outcrops east of line 1. The Vincent thrust fault is shallower than the reflector in most places. An unmapped structure (steep fault, monocline, or thrust fault) is required between line 1 and the outcrops that either drops the Vincent thrust fault down to the depths of the reflector or repeats the Vincent thrust fault beneath line 1 in the footwall of another thrust fault. An alternative interpretation of the reflector is a deep greenstone horizon within the Pelona Schist, although this alternative is not favored by the velocity structure. Copyright 2001 by the American

  9. Impact of two different types of grassland-to-cropland-conversion on dynamics of soil organic matter mineralization and N2O emission

    NASA Astrophysics Data System (ADS)

    Roth, G.; Flessa, H.; Helfrich, M.; Well, R.

    2012-04-01

    Conversion of grassland to arable land often causes a decrease of soil organic matter stocks and it increases nitrate leaching and the emission of the greenhouse gases CO2 and N2O. Conversion methods which minimize the mechanical impact on the surface soil may reduce mineralization rates and greenhouse gas emissions. We determined the effect of two different types of grassland to maize conversion (a) plowing of the sward followed by seeding of maize and (b) chemical killing of the sward by glyphosate followed by direct seed of maize) on the mineralization of grassland derived organic matter, the release of nitrate and the emission of N2O. The field experiment was carried out at the research station Kleve which is located in North Rhine-Westphalia, Germany. A four times replicated plot experiment with the following treatments was set up in April 2010: (i) mechanical conversion of grassland to maize (ii) chemical conversion grassland to maize and (iii) continuous grassland as reference. Nitrogen fertilization was 137 kg N ha-1 for maize and 250 kg N ha-1 for grassland. Soil respiration and emission of N2O were measured weekly for one year using manual closed chambers and gas chromatography. Emission of CO2 from mineralization of grassland-derived organic matter was determined from the δ13C signature of soil respiration. Soil respiration was mainly fueled by mineralization of grassland-derived organic carbon. There was no effect of the type of grassland conversion on total mineralization of organic matter originating from grassland. Both grassland to maize conversion treatments exhibited very high soil nitrate concentrations one year after grassland conversion (about 250 kg NO3-N in 0 - 90 cm). Total N2O emission decreased in the order chemical conversion of grassland (25.5) > mechanical conversion of grassland (20.1) > permanent grassland (10.8). Emissions were highest after harvest of maize when soil moisture increased. The results show that both types of grassland

  10. Extensive Management Promotes Plant and Microbial Nitrogen Retention in Temperate Grassland

    PubMed Central

    de Vries, Franciska T.; Bloem, Jaap; Quirk, Helen; Stevens, Carly J.; Bol, Roland; Bardgett, Richard D.

    2012-01-01

    Leaching losses of nitrogen (N) from soil and atmospheric N deposition have led to widespread changes in plant community and microbial community composition, but our knowledge of the factors that determine ecosystem N retention is limited. A common feature of extensively managed, species-rich grasslands is that they have fungal-dominated microbial communities, which might reduce soil N losses and increase ecosystem N retention, which is pivotal for pollution mitigation and sustainable food production. However, the mechanisms that underpin improved N retention in extensively managed, species-rich grasslands are unclear. We combined a landscape-scale field study and glasshouse experiment to test how grassland management affects plant and soil N retention. Specifically, we hypothesised that extensively managed, species-rich grasslands of high conservation value would have lower N loss and greater N retention than intensively managed, species-poor grasslands, and that this would be due to a greater immobilisation of N by a more fungal-dominated microbial community. In the field study, we found that extensively managed, species-rich grasslands had lower N leaching losses. Soil inorganic N availability decreased with increasing abundance of fungi relative to bacteria, although the best predictor of soil N leaching was the C/N ratio of aboveground plant biomass. In the associated glasshouse experiment we found that retention of added 15N was greater in extensively than in intensively managed grasslands, which was attributed to a combination of greater root uptake and microbial immobilisation of 15N in the former, and that microbial immobilisation increased with increasing biomass and abundance of fungi. These findings show that grassland management affects mechanisms of N retention in soil through changes in root and microbial uptake of N. Moreover, they support the notion that microbial communities might be the key to improved N retention through tightening linkages

  11. Quantifying the pedo-ecohydrological structure and function of degraded, grassland ecosystems

    NASA Astrophysics Data System (ADS)

    Brazier, Richard E.

    2015-04-01

    the environmental setting or wider climatic conditions that the grasslands experience. Furthermore, it is demonstrated that the relatively stable ecosystem state that has prevailed in the 'pristine' grasslands studied, is in fact very fragile and may be easily altered, either by anthropogenic forcing, due to land management or by 'semi-natural' processes, related to climate change or changes in the incidence of wildfires (for example). Once structurally altered, it is also shown that positive feedbacks will occur to accelerate the loss of critical resources (topsoil and nutrients) from the ecosystem, in particular in drylands, resulting in widespread land degradation that cannot be reversed. In the temperate grasslands studied, it is shown that anthropogenic intervention may halt or even to some degree reverse the degradation of the soil-vegetation-water continuum. However, such 'landscape restoration' approaches are costly and require long-term management commitment if they are to succeed. Finally, analysis of water, sediment and nutrient fluxes from this range of grasslands also demonstrates how critical ecosystem services that grasslands can provide; including soil water storage to buffer downstream flooding, soil carbon storage and enhanced biodiversity are reduced, often to the point where restoration of the original (pristine) landscape function is impossible. To conclude, discussion is made of how we can learn across grass landscapes globally, to ensure that those ecosystems that might be restored to build resilient landscapes under future climates are well understood and that future efforts to manage grasslands for increased food production do not degrade these critical ecosystems further.

  12. Quantifying the pedo-ecohydrological structure and function of degraded, grassland ecosystems

    NASA Astrophysics Data System (ADS)

    Brazier, Richard E.

    2015-04-01

    the environmental setting or wider climatic conditions that the grasslands experience. Furthermore, it is demonstrated that the relatively stable ecosystem state that has prevailed in the 'pristine' grasslands studied, is in fact very fragile and may be easily altered, either by anthropogenic forcing, due to land management or by 'semi-natural' processes, related to climate change or changes in the incidence of wildfires (for example). Once structurally altered, it is also shown that positive feedbacks will occur to accelerate the loss of critical resources (topsoil and nutrients) from the ecosystem, in particular in drylands, resulting in widespread land degradation that cannot be reversed. In the temperate grasslands studied, it is shown that anthropogenic intervention may halt or even to some degree reverse the degradation of the soil-vegetation-water continuum. However, such 'landscape restoration' approaches are costly and require long-term management commitment if they are to succeed. degrade these critical ecosystems further. Finally, analysis of water, sediment and nutrient fluxes from this range of grasslands also demonstrates how critical ecosystem services that grasslands can provide; including soil water storage to buffer downstream flooding, soil carbon storage and enhanced biodiversity are reduced, often to the point where restoration of the original (pristine) landscape function is impossible. To conclude, discussion is made of how we can learn across grass landscapes globally, to ensure that those ecosystems that might be restored to build resilient landscapes under future climates are well understood and that future efforts to manage grasslands for increased food production do not degrade these critical ecosystems further.

  13. Changes in Temperature Sensitivity and Activation Energy of Soil Organic Matter Decomposition in Different Qinghai-Tibet Plateau Grasslands

    PubMed Central

    Li, Jie; He, Nianpeng; Wei, Xuehong; Gao, Yang; Zuo, Yao

    2015-01-01

    Qinghai-Tibet Plateau grasslands are unique geographical regions and store substantial soil organic matter (SOM) in the soil surface, which make them very sensitive to global climate change. Here, we focused on three main grassland types (alpine meadow, steppe, and desert) and conducted a soil incubation experiment at five different temperatures (5, 10, 15, 20, and 25°C) to investigate SOM decomposition rates (R), temperature sensitivity (Q10), and activation energy (Ea). The results showed that grassland type and incubation temperature had significant impact on R (P < 0.001), and the values of R were exponential correlated with incubation temperature in three alpine grasslands. At the same temperature, R was in the following order: alpine meadow > alpinesteppe > alpine desert. The Q10 values differed significantly among different grasslands, and the overall trends were as follows: alpine meadow (1.56 ± 0.09) < alpine steppe (1.88 ± 0.23) < alpine desert (2.39 ± 0.32). Moreover, the Ea values differed significantly across different grassland types (P < 0.001) and increased with increasing incubation time. The exponential negative correlations between Ea and R at 20°C across all grassland types (all Ps < 0.001) indicated that the substrate-quality temperature hypothesis is applicable to the alpine grasslands. Our findings provide new insights for understanding the responses of SOM decomposition and storage to warming scenarios in this Plateau. PMID:26176705

  14. Changes in Temperature Sensitivity and Activation Energy of Soil Organic Matter Decomposition in Different Qinghai-Tibet Plateau Grasslands.

    PubMed

    Li, Jie; He, Nianpeng; Wei, Xuehong; Gao, Yang; Zuo, Yao

    2015-01-01

    Qinghai-Tibet Plateau grasslands are unique geographical regions and store substantial soil organic matter (SOM) in the soil surface, which make them very sensitive to global climate change. Here, we focused on three main grassland types (alpine meadow, steppe, and desert) and conducted a soil incubation experiment at five different temperatures (5, 10, 15, 20, and 25°C) to investigate SOM decomposition rates (R), temperature sensitivity (Q10), and activation energy (Ea). The results showed that grassland type and incubation temperature had significant impact on R (P < 0.001), and the values of R were exponential correlated with incubation temperature in three alpine grasslands. At the same temperature, R was in the following order: alpine meadow > alpinesteppe > alpine desert. The Q10 values differed significantly among different grasslands, and the overall trends were as follows: alpine meadow (1.56 ± 0.09) < alpine steppe (1.88 ± 0.23) < alpine desert (2.39 ± 0.32). Moreover, the Ea values differed significantly across different grassland types (P < 0.001) and increased with increasing incubation time. The exponential negative correlations between Ea and R at 20°C across all grassland types (all Ps < 0.001) indicated that the substrate-quality temperature hypothesis is applicable to the alpine grasslands. Our findings provide new insights for understanding the responses of SOM decomposition and storage to warming scenarios in this Plateau. PMID:26176705

  15. Implementing Aid in Dying in California: Experiences from Other States Indicates the Need for Strong Implementation Guidance.

    PubMed

    Cain, Cindy L

    2016-05-01

    In late 2015, California passed the End of Life Option Act (AB 15), which allows residents at the terminal stage of an illness to request a prescription for medications meant to hasten death. As California seeks to implement the law in June 2016, findings from other states that practice aid in dying (AID) may guide implementation. This policy brief provides an overview of the use of AID, outlines outstanding questions about practice and ethics, and recommends steps for improving California's implementation of AB 15. Specifically, the implementation of AB 15 would be improved by adjusting surveillance data-collection requirements and encouraging additional research investment, using the legalization of AID to improve knowledge of and practices for end-of-life care generally, and creating ongoing educational opportunities for providers and the general public. PMID:27416645

  16. Herbivores and nutrients control grassland plant diversity via light limitation.

    PubMed

    Borer, Elizabeth T; Seabloom, Eric W; Gruner, Daniel S; Harpole, W Stanley; Hillebrand, Helmut; Lind, Eric M; Adler, Peter B; Alberti, Juan; Anderson, T Michael; Bakker, Jonathan D; Biederman, Lori; Blumenthal, Dana; Brown, Cynthia S; Brudvig, Lars A; Buckley, Yvonne M; Cadotte, Marc; Chu, Chengjin; Cleland, Elsa E; Crawley, Michael J; Daleo, Pedro; Damschen, Ellen I; Davies, Kendi F; DeCrappeo, Nicole M; Du, Guozhen; Firn, Jennifer; Hautier, Yann; Heckman, Robert W; Hector, Andy; HilleRisLambers, Janneke; Iribarne, Oscar; Klein, Julia A; Knops, Johannes M H; La Pierre, Kimberly J; Leakey, Andrew D B; Li, Wei; MacDougall, Andrew S; McCulley, Rebecca L; Melbourne, Brett A; Mitchell, Charles E; Moore, Joslin L; Mortensen, Brent; O'Halloran, Lydia R; Orrock, John L; Pascual, Jesús; Prober, Suzanne M; Pyke, David A; Risch, Anita C; Schuetz, Martin; Smith, Melinda D; Stevens, Carly J; Sullivan, Lauren L; Williams, Ryan J; Wragg, Peter D; Wright, Justin P; Yang, Louie H

    2014-04-24

    Human alterations to nutrient cycles and herbivore communities are affecting global biodiversity dramatically. Ecological theory predicts these changes should be strongly counteractive: nutrient addition drives plant species loss through intensified competition for light, whereas herbivores prevent competitive exclusion by increasing ground-level light, particularly in productive systems. Here we use experimental data spanning a globally relevant range of conditions to test the hypothesis that herbaceous plant species losses caused by eutrophication may be offset by increased light availability due to herbivory. This experiment, replicated in 40 grasslands on 6 continents, demonstrates that nutrients and herbivores can serve as counteracting forces to control local plant diversity through light limitation, independent of site productivity, soil nitrogen, herbivore type and climate. Nutrient addition consistently reduced local diversity through light limitation, and herbivory rescued diversity at sites where it alleviated light limitation. Thus, species loss from anthropogenic eutrophication can be ameliorated in grasslands where herbivory increases ground-level light. PMID:24670649

  17. Herbivores and nutrients control grassland plant diversity via light limitation

    USGS Publications Warehouse

    Borer, Elizabeth T.; Seabloom, Eric W.; Gruner, Daniel S.; Harpole, W. Stanley; Hillebrand, Helmut; Lind, Eric M.; Alder, Peter B.; Alberti, Juan; Anderson, T. Michael; Bakker, Jonathan D.; Biederman, Lori; Blumenthal, Dana; Brown, Cynthia S.; Brudvig, Lars A.; Buckley, Yvonne M.; Cadotte, Marc; Chu, Cheng-Jin; Cleland, Elsa E.; Crawley, Michael J.; Daleo, Pedro; Damschen, Ellen Ingman; Davies, Kendi F.; DeCrappeo, Nicole M.; Du, Guozhen; Firn, Jennifer; Hautier, Yann; Heckman, Robert W.; Hector, Andy; HilleRisLambers, Janneke; Iribarne, Oscar; Klein, Julia A.; Knops, Johannes M.H.; La Pierre, Kimberly J.; Leakey, Andrew D.B.; Li, Wei; MacDougall, Andrew S.; McCulley, Rebecca L.; Melbourne, Brett A.; Mitchell, Charles E.; Moore, Joslin L.; Mortensen, Brent; O'Halloran, Lydia R.; Orrock, John L.; Pascual, Jesús; Prober, Suzanne M.; Pyke, David A.; Risch, Anita C.; Schuetz, Martin; Smith, Melinda D.; Stevens, Carly J.; Sullivan, Lauren L.; Williams, Ryan J.; Wragg, Peter D.; Wright, Justin P.; Yang, Louie H.

    2014-01-01

    Human alterations to nutrient cycles and herbivore communities are affecting global biodiversity dramatically. Ecological theory predicts these changes should be strongly counteractive: nutrient addition drives plant species loss through intensified competition for light, whereas herbivores prevent competitive exclusion by increasing ground-level light, particularly in productive systems. Here we use experimental data spanning a globally relevant range of conditions to test the hypothesis that herbaceous plant species losses caused by eutrophication may be offset by increased light availability due to herbivory. This experiment, replicated in 40 grasslands on 6 continents, demonstrates that nutrients and herbivores can serve as counteracting forces to control local plant diversity through light limitation, independent of site productivity, soil nitrogen, herbivore type and climate. Nutrient addition consistently reduced local diversity through light limitation, and herbivory rescued diversity at sites where it alleviated light limitation. Thus, species loss from anthropogenic eutrophication can be ameliorated in grasslands where herbivory increases ground-level light.

  18. The balance between methane emissions and uptake in a pond-grassland ecosystem: Evidence for high temperature-sensitivity of emissions

    SciTech Connect

    Torn, M.S.

    1995-06-01

    Methane emissions and uptake were studied in an annual grassland and in seasonally-flooded soils near a pond in California from 1991 to 1993. The pond margin emitted methane (0-229 mg CH{sub 4} m{sup -2} d{sup -1}). Uptake by the grasslands averaged -0.7 mg CH{sub 4} m{sup -2} d{sup -1}, and annual uptake was highly and positively correlated with soil carbon and nitrogen content (R{sup 2} = 0.97; n=5 sites) with no significant effect of sheep grazing. Field experiments were used to determine if emissions and uptake differed in their response to variation in temperature and moisture. Methane production and consumption responded differently to changes in temperature and moisture. Methane emissions were positively correlated with soil temperature, whereas methane uptake was not significantly related to temperature. The effective temperature response for emissions (e.g., Q{sub 10}) from locations with simultaneous production and consumption was much larger than the Q{sub 10} for production alone, a result with widespread implications. A model that incorporates both the differential effect of temperature on emissions and uptake, and the balance of production and consumption, predicts three times more change in global ecosystems emissions in response to warming than does a model that ignores these two features and includes only net methane release.

  19. Grasslands, Invertebrates, and Precipitation: A Review of the Effects of Climate Change

    PubMed Central

    Barnett, Kirk L.; Facey, Sarah L.

    2016-01-01

    Invertebrates are the main components of faunal diversity in grasslands, playing substantial roles in ecosystem processes including nutrient cycling and pollination. Grassland invertebrate communities are heavily dependent on the plant diversity and production within a given system. Climate change models predict alterations in precipitation patterns, both in terms of the amount of total inputs and the frequency, seasonality and intensity with which these inputs occur, which will impact grassland productivity. Given the ecological, economic and biodiversity value of grasslands, and their importance globally as areas of carbon storage and agricultural development, it is in our interest to understand how predicted alterations in precipitation patterns will affect grasslands and the invertebrate communities they contain. Here, we review the findings from manipulative and observational studies which have examined invertebrate responses to altered rainfall, with a particular focus on large-scale field experiments employing precipitation manipulations. Given the tight associations between invertebrate communities and their underlying plant communities, invertebrate responses to altered precipitation generally mirror those of the plants in the system. However, there is evidence that species responses to future precipitation changes will be idiosyncratic and context dependent across trophic levels, challenging our ability to make reliable predictions about how grassland communities will respond to future climatic changes, without further investigation. Thus, moving forward, we recommend increased consideration of invertebrate communities in current and future rainfall manipulation platforms, as well as the adoption of new technologies to aid such studies. PMID:27547213

  20. Grasslands, Invertebrates, and Precipitation: A Review of the Effects of Climate Change.

    PubMed

    Barnett, Kirk L; Facey, Sarah L

    2016-01-01

    Invertebrates are the main components of faunal diversity in grasslands, playing substantial roles in ecosystem processes including nutrient cycling and pollination. Grassland invertebrate communities are heavily dependent on the plant diversity and production within a given system. Climate change models predict alterations in precipitation patterns, both in terms of the amount of total inputs and the frequency, seasonality and intensity with which these inputs occur, which will impact grassland productivity. Given the ecological, economic and biodiversity value of grasslands, and their importance globally as areas of carbon storage and agricultural development, it is in our interest to understand how predicted alterations in precipitation patterns will affect grasslands and the invertebrate communities they contain. Here, we review the findings from manipulative and observational studies which have examined invertebrate responses to altered rainfall, with a particular focus on large-scale field experiments employing precipitation manipulations. Given the tight associations between invertebrate communities and their underlying plant communities, invertebrate responses to altered precipitation generally mirror those of the plants in the system. However, there is evidence that species responses to future precipitation changes will be idiosyncratic and context dependent across trophic levels, challenging our ability to make reliable predictions about how grassland communities will respond to future climatic changes, without further investigation. Thus, moving forward, we recommend increased consideration of invertebrate communities in current and future rainfall manipulation platforms, as well as the adoption of new technologies to aid such studies. PMID:27547213

  1. Assessing Information Literacy among Undergraduates: A Discussion of the Literature and the University of California-Berkeley Assessment Experience.

    ERIC Educational Resources Information Center

    Maughan, Patricia Davitt

    2001-01-01

    Since 1994, the Teaching Library at the University of California-Berkeley has conducted an ongoing Survey of Information Literacy Competencies in selected academic departments to measure the "lower-order" information literacy skills of graduating seniors. The survey reveals that students think they know more about accessing information and…

  2. Experiences & Perceptions: A Phenomenological Study of the Personal Journey of California Community College Faculty Who Advanced into Dean Positions

    ERIC Educational Resources Information Center

    McManus, Melissa Joann

    2013-01-01

    California community colleges are facing an impending leadership crisis due to a lack of formal preparations related to leadership training practices, proper budgetary resources, and misconceptions associated with administration, which could prevent the preparation of individual advancement into academic leadership roles. Currently, formal…

  3. Comparative Effectiveness of Houghton Mifflin Harcourt Fuse: Algebra 1--A Report of Randomized Experiments in Four California Districts

    ERIC Educational Resources Information Center

    Toby, Megan; Ma, Boya; Lai, Garrett; Lin, Li; Jaciw, Andrew

    2012-01-01

    In spring 2010, Houghton Mifflin Harcourt (HMH) began planning a pilot of an application for the Apple iPad, "HMH Fuse: Algebra 1," which was then in development. The application was to be piloted in four California school districts during the 2010-2011 school year. HMH contracted with Empirical Education Inc. to conduct a one-year randomized…

  4. Comparative Effectiveness of Houghton Mifflin Harcourt Fuse: Algebra 1--A Report of Randomized Experiments in Four California Districts. Research Summary

    ERIC Educational Resources Information Center

    Empirical Education Inc., 2012

    2012-01-01

    In spring 2010, Houghton Mifflin Harcourt (HMH) began planning a pilot of an application for the Apple iPad, "HMH Fuse: Algebra 1," which was then in development. The application was to be piloted in four California school districts during the 2010-2011 school year. HMH contracted with Empirical Education Inc. to conduct a one-year randomized…

  5. The Immigrant's University: A Study of Academic Performance and the Experiences of Recent Immigrant Groups at the University of California

    ERIC Educational Resources Information Center

    Douglass, John Aubrey; Thomson, Gregg

    2010-01-01

    One of the major characteristics of globalization is the large influx of immigrant groups moving largely from underdeveloped regions to developed economies. California offers one of the most robust examples of a large-scale, postmodern demographic transition that includes a great racial, ethnic, and cultural diversity of immigrant groups, many of…

  6. Job Search, Training, and Work Experience: The Lessons for California from Eight Evaluations of the Work Incentive Program.

    ERIC Educational Resources Information Center

    Warren, Paul; Johnson, Hadley

    As part of a review of California's strategy for helping recipients of Aid to Families with Dependent Children (AFDC) find jobs through the Work Incentive Program (WIN), eight demonstration programs were analyzed. There were four major findings. First, the Department of Social Services (DSS), which targets AFDC recipients with recent job…

  7. Lift Ev'ry Voice: The Resounding Experiences of Black Male Student-Athletes at a California Community College

    ERIC Educational Resources Information Center

    McClellan, Michael L.

    2013-01-01

    Black male student-athletes are entering the California community college (CCC) system at an unprecedented rate. CCCs have become a repository for Black males that have aspirations of competing in the National Collegiate Athletic Association (NCAA) Division I member institutions. This historically disenfranchised subgroup of students is required…

  8. Understanding Success of Historically Underrepresented Students at California State University, Monterey Bay through a Look at Their Institutional Experiences

    ERIC Educational Resources Information Center

    Boyce, Mary; Chukwuemeka, Veronica; Cruz-Uribe, Kathryn

    2013-01-01

    Unlike many universities, the historically under-represented (URM) students at California State University, Monterey Bay, typically graduate at a higher rate than non-URM students. Intense efforts have been made by staff and faculty to increase retention and graduation rates of all students. This paper examines the graduation rates in the context…

  9. Satellite-based assessment of grassland yields

    NASA Astrophysics Data System (ADS)

    Grant, K.; Siegmund, R.; Wagner, M.; Hartmann, S.

    2015-04-01

    Cutting date and frequency are important parameters determining grassland yields in addition to the effects of weather, soil conditions, plant composition and fertilisation. Because accurate and area-wide data of grassland yields are currently not available, cutting frequency can be used to estimate yields. In this project, a method to detect cutting dates via surface changes in radar images is developed. The combination of this method with a grassland yield model will result in more reliable and regional-wide numbers of grassland yields. For the test-phase of the monitoring project, a study area situated southeast of Munich, Germany, was chosen due to its high density of managed grassland. For determining grassland cutting robust amplitude change detection techniques are used evaluating radar amplitude or backscatter statistics before and after the cutting event. CosmoSkyMed and Sentinel-1A data were analysed. All detected cuts were verified according to in-situ measurements recorded in a GIS database. Although the SAR systems had various acquisition geometries, the amount of detected grassland cut was quite similar. Of 154 tested grassland plots, covering in total 436 ha, 116 and 111 cuts were detected using CosmoSkyMed and Sentinel-1A radar data, respectively. Further improvement of radar data processes as well as additional analyses with higher sample number and wider land surface coverage will follow for optimisation of the method and for validation and generalisation of the results of this feasibility study. The automation of this method will than allow for an area-wide and cost efficient cutting date detection service improving grassland yield models.

  10. California Dust

    Atmospheric Science Data Center

    2014-05-15

    ... dramatically when forced through narrow canyons and mountain passes. Due to Southern California's uneven terrain, the strength of ... from a small fire located near the southern flank of Palomar Mountain in Southern California. This image was acquired during Terra orbit ...

  11. Plant species richness increases phosphatase activities in an experimental grassland

    NASA Astrophysics Data System (ADS)

    Hacker, Nina; Wilcke, Wolfgang; Oelmann, Yvonne

    2014-05-01

    Plant species richness has been shown to increase aboveground nutrient uptake requiring the mobilization of soil nutrient pools. For phosphorus (P) the underlying mechanisms for increased P release in soil under highly diverse grassland mixtures remain obscure because aboveground P storage and concentrations of inorganic and organic P in soil solution and differently reactive soil P pools are unrelated (Oelmann et al. 2011). The need of plants and soil microorganisms for P can increase the exudation of enzymes hydrolyzing organically bound P (phosphatases) which might represent an important release mechanism of inorganic P in a competitive environment such as highly diverse grassland mixtures. Our objectives were to test the effects of i) plant functional groups (legumes, grasses, non-leguminous tall and small herbs), and of (ii) plant species richness on microbial P (Pmic) and phosphatase activities in soil. In autumn 2013, we measured Pmic and alkaline phosphomonoesterase and phosphodiesterase activities in soil of 80 grassland mixtures comprising different community compositions and species richness (1, 2, 4, 8, 16, 60) in the Jena Experiment. In general, Pmic and enzyme activities were correlated (r = 0.59 and 0.46 for phosphomonoesterase and phosphodiesterase activities, respectively; p

  12. Eutrophication weakens stabilizing effects of diversity in natural grasslands.

    PubMed

    Hautier, Yann; Seabloom, Eric W; Borer, Elizabeth T; Adler, Peter B; Harpole, W Stanley; Hillebrand, Helmut; Lind, Eric M; MacDougall, Andrew S; Stevens, Carly J; Bakker, Jonathan D; Buckley, Yvonne M; Chu, Chengjin; Collins, Scott L; Daleo, Pedro; Damschen, Ellen I; Davies, Kendi F; Fay, Philip A; Firn, Jennifer; Gruner, Daniel S; Jin, Virginia L; Klein, Julia A; Knops, Johannes M H; La Pierre, Kimberly J; Li, Wei; McCulley, Rebecca L; Melbourne, Brett A; Moore, Joslin L; O'Halloran, Lydia R; Prober, Suzanne M; Risch, Anita C; Sankaran, Mahesh; Schuetz, Martin; Hector, Andy

    2014-04-24

    Studies of experimental grassland communities have demonstrated that plant diversity can stabilize productivity through species asynchrony, in which decreases in the biomass of some species are compensated for by increases in others. However, it remains unknown whether these findings are relevant to natural ecosystems, especially those for which species diversity is threatened by anthropogenic global change. Here we analyse diversity-stability relationships from 41 grasslands on five continents and examine how these relationships are affected by chronic fertilization, one of the strongest drivers of species loss globally. Unmanipulated communities with more species had greater species asynchrony, resulting in more stable biomass production, generalizing a result from biodiversity experiments to real-world grasslands. However, fertilization weakened the positive effect of diversity on stability. Contrary to expectations, this was not due to species loss after eutrophication but rather to an increase in the temporal variation of productivity in combination with a decrease in species asynchrony in diverse communities. Our results demonstrate separate and synergistic effects of diversity and eutrophication on stability, emphasizing the need to understand how drivers of global change interactively affect the reliable provisioning of ecosystem services in real-world systems. PMID:24531763

  13. Measuring dry plant residues in grasslands: A case study using AVIRIS

    NASA Technical Reports Server (NTRS)

    Fitzgerald, Michael; Ustin, Susan L.

    1992-01-01

    Grasslands, savannah, and hardwood rangelands are critical ecosystems and sensitive to disturbance. Approximately 20 percent of the Earth's surface are grasslands and represent 3 million ha. in California alone. Developing a methodology for estimating disturbance and the effects of cumulative impacts on grasslands and rangelands is needed to effectively monitor these ecosystems. Estimating the dry biomass residue remaining on rangelands at the end of the growing season provides a basis for evaluating the effectiveness of land management practices. The residual biomass is indicative of the grazing pressure and provides a measure of the system capacity for nutrient cycling since it represents the maximum organic matter available for decomposition, and finally, provides a measure of the erosion potential for the ecosystem. Remote sensing presents a possible method for measuring dry residue. However, current satellites have had limited application due to the coarse spatial scales (relative to the patch dynamics) and insensitivity of the spectral coverage to resolve dry plant material. Several hypotheses for measuring the biochemical constituents of dry plant material, particularly cellulose and lignin, using high spectral resolution sensors were proposed. The use of Airborne Visible/Infrared Imaging Spectrometers (AVIRIS) to measure dry plant residues over an oak savannah on the eastern slopes of the Coast Range in central California was investigated and it was asked what spatial and spectral resolutions are needed to quantitatively measure dry plant biomass in this ecosystem.

  14. Evidence for Recent Invasion of Historically Resistant Chaparral Shrublands to Grasslands

    NASA Astrophysics Data System (ADS)

    Park, I.; Jenerette, D.; Hooper, J.

    2015-12-01

    Although historically resistant to invasion and type-conversion, there are strong indications that native shrublands in southern California are often increasingly degraded, and in many cases have begun transitioning into herbaceous grasslands. Chaparral shrublands in particular, which are characterized by a closed evergreen canopy composed of multiple species, represent a critical habitat for many native fauna and also play a significant role in soil stabilization and water partitioning throughout much of Southern California. However, in response to interactive global changes, these ecosystems may be transitioning into invasive-dominated deciduous grasslands. Through the use of a novel, phenology-driven vegetation classification, we examine the extent of such type-conversions through analysis of increases in seasonal changes (i.e. deciduousness). Estimates of phenological variation in greenness (NDVI) developed through analysis of Landsat 4-8 imagery were calibrated to observed seasonal NDVI variation as developed through high-resolution ground-based imagery platforms to develop estimates in the change of percent cover by evergreen shrubs and drought-deciduous herbs and grasses. This study evaluates long-term changes in invasive cover from 1985 through 2011. These analyses indicate substantial type-conversion of native chaparral over this period, as with differences in local elevation representing the dominant factor in the degree of long-term type-conversion at broad landscape-scales, with high elevation sites being the least susceptible to type conversion from chaparral to invaded grassland.

  15. "Picturing the Past": Farm Women on the Grasslands Frontier, 1850-1900

    ERIC Educational Resources Information Center

    Sundberg, Sara Brooks

    2010-01-01

    This study analyzes fifty-two accounts by pioneer farm women from a less well known part of the U.S. grasslands, the Minnesota prairie between 1850 and 1900. Using Hamlin Garland's frequently cited description of his mother's experience as a baseline for comparison to Minnesota farm women's experiences, this study finds that pioneer farm women…

  16. Soil type and moisture regime control microbial C and N mineralization in grassland soils more than atmospheric CO2-induced changes in litter quality

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Decomposition in grassland soils and subsequent impacts on grassland C storage will depend on how global change effects on litter quality and soil moisture interact with edaphic characteristics across the landscape. We measured grass litter decomposition in a full-factorial incubation experiment (1...

  17. Bundled payment fails to gain a foothold In California: the experience of the IHA bundled payment demonstration.

    PubMed

    Ridgely, M Susan; de Vries, David; Bozic, Kevin J; Hussey, Peter S

    2014-08-01

    To determine whether bundled payment could be an effective payment model for California, the Integrated Healthcare Association convened a group of stakeholders (health plans, hospitals, ambulatory surgery centers, physician organizations, and vendors) to develop, through a consensus process, the methods and means of implementing bundled payment. In spite of a high level of enthusiasm and effort, the pilot did not succeed in its goal to implement bundled payment for orthopedic procedures across multiple payers and hospital-physician partners. An evaluation of the pilot documented a number of barriers, such as administrative burden, state regulatory uncertainty, and disagreements about bundle definition and assumption of risk. Ultimately, few contracts were signed, which resulted in insufficient volume to test hypotheses about the impact of bundled payment on quality and costs. Although bundled payment failed to gain a foothold in California, the evaluation provides lessons for future bundled payment initiatives. PMID:25092835

  18. The Effects of Timing of Grazing on Plant and Arthropod Communities in High-Elevation Grasslands

    PubMed Central

    Davis, Stacy C.; Burkle, Laura A.; Cross, Wyatt F.; Cutting, Kyle A.

    2014-01-01

    Livestock grazing can be used as a key management tool for maintaining healthy ecosystems. However, the effectiveness of using grazing to modify habitat for species of conservation concern depends on how the grazing regime is implemented. Timing of grazing is one grazing regime component that is less understood than grazing intensity and grazer identity, but is predicted to have important implications for plant and higher trophic level responses. We experimentally assessed how timing of cattle grazing affected plant and arthropod communities in high-elevation grasslands of southwest Montana to better evaluate its use as a tool for multi-trophic level management. We manipulated timing of grazing, with one grazing treatment beginning in mid-June and the other in mid-July, in two experiments conducted in different grassland habitat types (i.e., wet meadow and upland) in 2011 and 2012. In the upland grassland experiment, we found that both early and late grazing treatments reduced forb biomass, whereas graminoid biomass was only reduced with late grazing. Grazing earlier in the growing season versus later did not result in greater recovery of graminoid or forb biomass as expected. In addition, the density of the most ubiquitous grassland arthropod order (Hemiptera) was reduced by both grazing treatments in upland grasslands. A comparison of end-of-season plant responses to grazing in upland versus wet meadow grasslands revealed that grazing reduced graminoid biomass in the wet meadow and forb biomass in the upland, irrespective of timing of grazing. Both grazing treatments also reduced end-of-season total arthropod and Hemiptera densities and Hemiptera biomass in both grassland habitat types. Our results indicate that both early and late season herbivory affect many plant and arthropod characteristics in a similar manner, but grazing earlier may negatively impact species of conservation concern requiring forage earlier in the growing season. PMID:25338008

  19. Nitrogen deposition and greenhouse gas emissions from grasslands: uncertainties and future directions.

    PubMed

    Gomez-Casanovas, Nuria; Hudiburg, Tara W; Bernacchi, Carl J; Parton, William J; DeLucia, Evan H

    2016-04-01

    Increases in atmospheric nitrogen deposition (Ndep) can strongly affect the greenhouse gas (GHG; CO2, CH4, and N2O) sink capacity of grasslands as well as other terrestrial ecosystems. Robust predictions of the net GHG sink strength of grasslands depend on how experimental N loads compare to projected Ndep rates, and how accurately the relationship between GHG fluxes and Ndep is characterized. A literature review revealed that the vast majority of experimental N loads were higher than levels these ecosystems are predicted to experience in the future. Using a process-based biogeochemical model, we predicted that low levels of Ndep either enhanced or reduced the net GHG sink strength of most grasslands, but as experimental N loads continued to increase, grasslands transitioned to a N saturation-decline stage, where the sensitivity of GHG exchange to further increases in Ndep declined. Most published studies represented treatments well into the N saturation-decline stage. Our model results predict that the responses of GHG fluxes to N are highly nonlinear and that the N saturation thresholds for GHGs varied greatly among grasslands and with fire management. We predict that during the 21st century some grasslands will be in the N limitation stage where others will transition into the N saturation-decline stage. The linear relationship between GHG sink strength and N load assumed by most studies can overestimate or underestimate predictions of the net GHG sink strength of grasslands depending on their N baseline status. The next generation of global change experiments should be designed at multiple N loads consistent with future Ndep rates to improve our empirical understanding and predictive ability. PMID:26661794

  20. Multichannel seismic-reflection profiling on the R/V Maurice Ewing during the Los Angeles Region Seismic Experiment (LARSE), California

    USGS Publications Warehouse

    Brocher, Thomas M.; Clayton, Robert W.; Klitgord, Kim D.; Bohannon, Robert G.; Sliter, Ray; McRaney, John K.; Gardner, James V.; Keene, J.B.

    1995-01-01

    This report describes the acquisition of deep-crustal multichannel seismic-reflection data in the Inner California Borderland aboard the R/V Maurice Ewing, conducted in October 1994 as part of the Los Angeles Regional Seismic Experiment (LARSE). LARSE is a cooperative study of the crustal structure of southern California involving earth scientists from the U.S. Geological Survey, Caltech, the University of Southern California, the University of California Los Angeles, and the Southern California Earthquake Center (SCEC). During LARSE, the R/V Ewing's 20- element air gun array, totaling 137.7 liters (8470 cu. in.), was used as the primary seismic source for wide-angle recording along three main onshore-offshore lines centered on the Los Angeles basin and the epicenters of the 1933 Long Beach and 1994 Northridge earthquakes. The LARSE onshore-offshore lines were each 200-250 km long, with the offshore portions being between 90 and 150 km long. The nearly 24,000 air gun signals generated by the Ewing were recorded by an array of 170 PASSCAL REFTEK recorders deployed at 2 km intervals along all three of the onshore lines and 9 ocean bottom seismometers (OBSs) deployed along two of the lines. Separate passes over the OBS-deployment lines were performed with a long air gun repetition rate (60 and 90 seconds) to minimize acoustic-wave interference from previous shots in the OBS data. The Ewing's 4.2-km, 160-channel, digital streamer was also used to record approximately 1250 km of 40-fold multichannel seismic-reflection data. To enhance the fold of the wide-angle data recorded onshore, mitigating against cultural and wind noise in the Los Angeles basin, the entire ship track was repeated at least once resulting in fewer than about 660 km of unique trackline coverage in the Inner Borderland. Portions of the seismic-reflection lines were repeated up to 6 times. A variety of other geophysical data were also continuously recorded, including 3.5 kHz bathymetry, multi

  1. Spectral responses to plant available soil moisture in a Californian grassland

    NASA Astrophysics Data System (ADS)

    Liu, Shishi; Roberts, Dar A.; Chadwick, Oliver A.; Still, Chris J.

    2012-10-01

    This study established relationships among plant available soil moisture and reflectance and vegetation indices (VIs) derived from AVIRIS and MODIS data in grassland ecosystem in California. Strong correlations were observed between soil moisture and different forms of reflectance in the red-edge, near infrared and shortwave infrared bands. Both greenness-based and canopy-water-based indices were linearly related with soil moisture during the growing season, the wet and the dry season. The relationship was stronger with antecedent soil moisture, particularly in the dry season. Using plant available soil moisture, which is the difference between measured soil moisture and the wilting point, improved the relationship by reducing the soil property effect. Furthermore, results suggested that the difference in sensors had little impact on the relationships in grassland, but the parameters of relationships were influenced by the spatial resolution of sensors.

  2. Carbon fluxes from an urban tropical grassland.

    PubMed

    Ng, B J L; Hutyra, L R; Nguyen, H; Cobb, A R; Kai, F M; Harvey, C; Gandois, L

    2015-08-01

    Turfgrass covers a large fraction of the urbanized landscape, but the carbon exchange of urban lawns is poorly understood. We used eddy covariance and flux chambers in a grassland field manipulative experiment to quantify the carbon mass balance in a Singapore tropical turfgrass. We also assessed how management and variations in environmental factors influenced CO2 respiration. Standing aboveground turfgrass biomass was 80 gC m(-2), with a mean ecosystem respiration of 7.9 ± 1.1 μmol m(-2) s(-1). The contribution of autotrophic respiration was 49-76% of total ecosystem respiration. Both chamber and eddy covariance measurements suggest the system was in approximate carbon balance. While we did not observe a significant relationship between the respiration rates and soil temperature or moisture, daytime fluxes increased during the rainy interval, indicating strong overall moisture sensitivity. Turfgrass biomass is small, but given its abundance across the urban landscape, it significantly influences diurnal CO2 concentrations. PMID:24998996

  3. Grassland Arthropods Are Controlled by Direct and Indirect Interactions with Cattle but Are Largely Unaffected by Plant Provenance

    PubMed Central

    Farrell, Kelly Anne; Harpole, W. Stanley; Stein, Claudia; Suding, Katharine N.; Borer, Elizabeth T.

    2015-01-01

    Cattle grazing and invasion by non-native plant species are globally-ubiquitous changes occurring to plant communities that are likely to reverberate through whole food webs. We used a manipulative field experiment to quantify how arthropod community structure differed in native and non-native California grassland communities in the presence and absence of grazing. The arthropod community was strongly affected by cattle grazing: the biovolume of herbivorous arthropods was 79% higher in grazed than ungrazed plots, whereas the biovolume of predatory arthropods was 13% higher in ungrazed plots. In plots where non-native grasses were grazed, arthropod biovolume increased, possibly in response to increased plant productivity or increased nutritional quality of rapidly-growing annual plants. Grazing may thus affect plant biomass both through the direct removal of biomass, and through arthropod-mediated impacts. We also expected the arthropod community to differ between native and non-native plant communities; surprisingly, arthropod richness and diversity did not vary consistently between these grass community types, although arthropod abundance was slightly higher in plots with native and ungrazed grasses. These results suggest that whereas cattle grazing affects the arthropod community via direct and indirect pathways, arthropod community changes commonly associated with non-native plant invasions may not be due to the identity or dominance of the invasive species in those systems, but to accompanying changes in plant traits or functional group composition, not seen in this experiment because of the similarity of the plant communities. PMID:26158494

  4. Belowground grassland herbivores are resistant to elevated atmospheric CO2 concentrations in grassland ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grasslands are considered to be one of the most sensitive ecosystems to rising atmospheric CO2 concentrations. Moreover, grasslands support large populations of belowground herbivores that consume a major portion of plant biomass. The direct trophic link between herbivores and plants suggests that...

  5. Plant Trait Assembly Affects Superiority of Grazer's Foraging Strategies in Species-Rich Grasslands

    PubMed Central

    Mládek, Jan; Mládková, Pavla; Hejcmanová, Pavla; Dvorský, Miroslav; Pavlu, Vilém; De Bello, Francesco; Duchoslav, Martin; Hejcman, Michal; Pakeman, Robin J.

    2013-01-01

    Background Current plant – herbivore interaction models and experiments with mammalian herbivores grazing plant monocultures show the superiority of a maximizing forage quality strategy (MFQ) over a maximizing intake strategy (MI). However, there is a lack of evidence whether grazers comply with the model predictions under field conditions. Methodology/Findings We assessed diet selection of sheep (Ovis aries) using plant functional traits in productive mesic vs. low-productivity dry species-rich grasslands dominated by resource-exploitative vs. resource-conservative species respectively. Each grassland type was studied in two replicates for two years. We investigated the first grazing cycle in a set of 288 plots with a diameter of 30 cm, i.e. the size of sheep feeding station. In mesic grasslands, high plot defoliation was associated with community weighted means of leaf traits referring to high forage quality, i.e. low leaf dry matter content (LDMC) and high specific leaf area (SLA), with a high proportion of legumes and the most with high community weighted mean of forage indicator value. In contrast in dry grasslands, high community weighted mean of canopy height, an estimate of forage quantity, was the best predictor of plot defoliation. Similar differences in selection on forage quality vs. quantity were detected within plots. Sheep selected plants with higher forage indicator values than the plot specific community weighted mean of forage indicator value in mesic grasslands whereas taller plants were selected in dry grasslands. However, at this scale sheep avoided legumes and plants with higher SLA, preferred plants with higher LDMC while grazing plants with higher forage indicator values in mesic grasslands. Conclusions Our findings indicate that MFQ appears superior over MI only in habitats with a predominance of resource-exploitative species. Furthermore, plant functional traits (LDMC, SLA, nitrogen fixer) seem to be helpful correlates of forage quality

  6. [Differences in soil respiration between cropland and grassland ecosystems and factors influencing soil respiration on the Loess Plateau].

    PubMed

    Zhou, Xiao-Gang; Zhang, Yan-Jun; Nan, Ya-Fang; Liu, Qing-Fang; Guo, Sheng-Li

    2013-03-01

    Understanding the effect of land-use change on soil respiration rates becomes critical in predicting soil carbon cycling under conversion of arable into grassland on the Loess Plateau. From July 2010 to December 2011, CO2 efflux from the soil surface was measured between 08:00 to 10:00 am in clear days by a Licor-8100 closed chamber system (Li-COR, Lincoln, NE, US). Also, soil temperature and soil moisture at the 5-cm depth was measured using a Li-Cor thermocouple and a hand-held frequency-domain reflectometer (ML2x, Delta-T Devices Ltd, UK) at each PVC collar, respectively. We found marked differences (P < 0.05) in soil respiration related to different land-use: the mean cropland soil respiration [1.35 micromol x (m2 x s)(-1)] was 24% (P < 0.05) less than the paired grassland soil respiration [1.67 micromol x (m2 x s)(-1)] (P < 0.05) during the period of experiment and the cumulative CO2-C emissions in grassland (856 g x m(-2)) was 23% (P < 0.05) higher than that in cropland (694 g x m(-2)). Soil moisture from 0-5 cm depth was much drier in cropland and significantly different between cropland and grassland except for winter. However, there were no clear relationships between soil moisture and soil respiration. Soil temperature at 5-cm depth was 2.5 degress C higher in grassland during the period of experiment (P < 0.05). Regression of soil temperature vs. soil respiration indicated significant exponential relationships both in grassland and cropland. Besides, there were intrinsic differences in response of soil respiration to temperature between the cropland and grassland ecosystems: grassland and cropland respiration response was significantly different at the alpha = 0.05 level, also expressed by a higher temperature sensitivity of soil respiration (Q10) in cropland (2.30) relative to grassland (1.74). Soil temperature of cropland and grassland can explain 79% of the variation in the soil respiration in grassland, compared to 82% in cropland. Therefore, land

  7. Forging successful academic-community partnerships with community health centers: the California statewide Area Health Education Center (AHEC) experience.

    PubMed

    Fowkes, Virginia; Blossom, H John; Mitchell, Brenda; Herrera-Mata, Lydia

    2014-01-01

    Increased access to insurance under the Affordable Care Act will increase demands for clinical services in community health centers (CHCs). CHCs also have an increasingly important educational role to train clinicians who will remain to practice in community clinics. CHCs and Area Health Education Centers (AHECs) are logical partners to prepare the health workforce for the future. Both are sponsored by the Health Resources and Services Administration, and they share a mission to improve quality of care in medically underserved communities. AHECs emphasize the educational side of the mission, and CHCs the service side. Building stronger partnerships between them can facilitate a balance between education and service needs.From 2004 to 2011, the California Statewide AHEC program and its 12 community AHECs (centers) reorganized to align training with CHC workforce priorities. Eight centers merged into CHC consortia; others established close partnerships with CHCs in their respective regions. The authors discuss issues considered and approaches taken to make these changes. Collaborative innovative processes with program leadership, staff, and center directors revised the program mission, developed common training objectives with an evaluation plan, and defined organizational, functional, and impact characteristics for successful AHECs in California. During this planning, centers gained confidence as educational arms for the safety net and began collaborations with statewide programs as well as among themselves. The AHEC reorganization and the processes used to develop, strengthen, and identify standards for centers forged the development of new partnerships and established academic-community trust in planning and implementing programs with CHCs. PMID:24280858

  8. Some Insights on Grassland Health Assessment Based on Remote Sensing

    PubMed Central

    Xu, Dandan; Guo, Xulin

    2015-01-01

    Grassland ecosystem is one of the largest ecosystems, which naturally occurs on all continents excluding Antarctica and provides both ecological and economic functions. The deterioration of natural grassland has been attracting many grassland researchers to monitor the grassland condition and dynamics for decades. Remote sensing techniques, which are advanced in dealing with the scale constraints of ecological research and provide temporal information, become a powerful approach of grassland ecosystem monitoring. So far, grassland health monitoring studies have mostly focused on different areas, for example, productivity evaluation, classification, vegetation dynamics, livestock carrying capacity, grazing intensity, natural disaster detecting, fire, climate change, coverage assessment and soil erosion. However, the grassland ecosystem is a complex system which is formed by soil, vegetation, wildlife and atmosphere. Thus, it is time to consider the grassland ecosystem as an entity synthetically and establish an integrated grassland health monitoring system to combine different aspects of the complex grassland ecosystem. In this review, current grassland health monitoring methods, including rangeland health assessment, ecosystem health assessment and grassland monitoring by remote sensing from different aspects, are discussed along with the future directions of grassland health assessment. PMID:25643060

  9. Preliminary Research on Grassland Fine-classification Based on MODIS

    NASA Astrophysics Data System (ADS)

    Hu, Z. W.; Zhang, S.; Yu, X. Y.; Wang, X. S.

    2014-03-01

    Grassland ecosystem is important for climatic regulation, maintaining the soil and water. Research on the grassland monitoring method could provide effective reference for grassland resource investigation. In this study, we used the vegetation index method for grassland classification. There are several types of climate in China. Therefore, we need to use China's Main Climate Zone Maps and divide the study region into four climate zones. Based on grassland classification system of the first nation-wide grass resource survey in China, we established a new grassland classification system which is only suitable for this research. We used MODIS images as the basic data resources, and use the expert classifier method to perform grassland classification. Based on the 1:1,000,000 Grassland Resource Map of China, we obtained the basic distribution of all the grassland types and selected 20 samples evenly distributed in each type, then used NDVI/EVI product to summarize different spectral features of different grassland types. Finally, we introduced other classification auxiliary data, such as elevation, accumulate temperature (AT), humidity index (HI) and rainfall. China's nation-wide grassland classification map is resulted by merging the grassland in different climate zone. The overall classification accuracy is 60.4%. The result indicated that expert classifier is proper for national wide grassland classification, but the classification accuracy need to be improved.

  10. Some insights on grassland health assessment based on remote sensing.

    PubMed

    Xu, Dandan; Guo, Xulin

    2015-01-01

    Grassland ecosystem is one of the largest ecosystems, which naturally occurs on all continents excluding Antarctica and provides both ecological and economic functions. The deterioration of natural grassland has been attracting many grassland researchers to monitor the grassland condition and dynamics for decades. Remote sensing techniques, which are advanced in dealing with the scale constraints of ecological research and provide temporal information, become a powerful approach of grassland ecosystem monitoring. So far, grassland health monitoring studies have mostly focused on different areas, for example, productivity evaluation, classification, vegetation dynamics, livestock carrying capacity, grazing intensity, natural disaster detecting, fire, climate change, coverage assessment and soil erosion. However, the grassland ecosystem is a complex system which is formed by soil, vegetation, wildlife and atmosphere. Thus, it is time to consider the grassland ecosystem as an entity synthetically and establish an integrated grassland health monitoring system to combine different aspects of the complex grassland ecosystem. In this review, current grassland health monitoring methods, including rangeland health assessment, ecosystem health assessment and grassland monitoring by remote sensing from different aspects, are discussed along with the future directions of grassland health assessment. PMID:25643060

  11. Madagascar's grasses and grasslands: anthropogenic or natural?

    PubMed Central

    Besnard, Guillaume; Forest, Félix; Malakasi, Panagiota; Moat, Justin; Clayton, W. Derek; Ficinski, Paweł; Savva, George M.; Nanjarisoa, Olinirina P.; Razanatsoa, Jacqueline; Randriatsara, Fetra O.; Kimeu, John M.; Luke, W. R. Quentin; Kayombo, Canisius; Linder, H. Peter

    2016-01-01

    Grasses, by their high productivity even under very low pCO2, their ability to survive repeated burning and to tolerate long dry seasons, have transformed the terrestrial biomes in the Neogene and Quaternary. The expansion of grasslands at the cost of biodiverse forest biomes in Madagascar is often postulated as a consequence of the Holocene settlement of the island by humans. However, we show that the Malagasy grass flora has many indications of being ancient with a long local evolutionary history, much predating the Holocene arrival of humans. First, the level of endemism in the Madagascar grass flora is well above the global average for large islands. Second, a survey of many of the more diverse areas indicates that there is a very high spatial and ecological turnover in the grass flora, indicating a high degree of niche specialization. We also find some evidence that there are both recently disturbed and natural stable grasslands: phylogenetic community assembly indicates that recently severely disturbed grasslands are phylogenetically clustered, whereas more undisturbed grasslands tend to be phylogenetically more evenly distributed. From this evidence, it is likely that grass communities existed in Madagascar long before human arrival and so were determined by climate, natural grazing and other natural factors. Humans introduced zebu cattle farming and increased fire frequency, and may have triggered an expansion of the grasslands. Grasses probably played the same role in the modification of the Malagasy environments as elsewhere in the tropics. PMID:26791612

  12. Madagascar's grasses and grasslands: anthropogenic or natural?

    PubMed

    Vorontsova, Maria S; Besnard, Guillaume; Forest, Félix; Malakasi, Panagiota; Moat, Justin; Clayton, W Derek; Ficinski, Paweł; Savva, George M; Nanjarisoa, Olinirina P; Razanatsoa, Jacqueline; Randriatsara, Fetra O; Kimeu, John M; Luke, W R Quentin; Kayombo, Canisius; Linder, H Peter

    2016-01-27

    Grasses, by their high productivity even under very low pCO2, their ability to survive repeated burning and to tolerate long dry seasons, have transformed the terrestrial biomes in the Neogene and Quaternary. The expansion of grasslands at the cost of biodiverse forest biomes in Madagascar is often postulated as a consequence of the Holocene settlement of the island by humans. However, we show that the Malagasy grass flora has many indications of being ancient with a long local evolutionary history, much predating the Holocene arrival of humans. First, the level of endemism in the Madagascar grass flora is well above the global average for large islands. Second, a survey of many of the more diverse areas indicates that there is a very high spatial and ecological turnover in the grass flora, indicating a high degree of niche specialization. We also find some evidence that there are both recently disturbed and natural stable grasslands: phylogenetic community assembly indicates that recently severely disturbed grasslands are phylogenetically clustered, whereas more undisturbed grasslands tend to be phylogenetically more evenly distributed. From this evidence, it is likely that grass communities existed in Madagascar long before human arrival and so were determined by climate, natural grazing and other natural factors. Humans introduced zebu cattle farming and increased fire frequency, and may have triggered an expansion of the grasslands. Grasses probably played the same role in the modification of the Malagasy environments as elsewhere in the tropics. PMID:26791612

  13. Building capacity for HIV/AIDS prevention among Asian Pacific Islander organizations: the experience of a culturally appropriate capacity-building program in Southern California.

    PubMed

    Takahashi, Lois M; Candelario, Jury; Young, Tim; Mediano, Elizabeth

    2007-01-01

    This article has two goals: (1) to outline a conceptual model for culturally appropriate HIV prevention capacity building; (2) to present the experiences from a 3-year program provided by Asian Pacific AIDS Intervention Team to Asian Pacific Islander (API) organizations in southern California. The participating organizations were of two types: lesbian, gay, bisexual, transgender, and questioning (LGBTQ) social organizations and social service agencies not targeting LGBTQ. These organizations were selected for participation because of their commitment to HIV/AIDS issues in API communities. An organizational survey and staff observations were used to explore changes in capacity. The organizations were mostly small, targeted diverse populations, served a large geographic area (southern California as a region), and were knowledgeable about HIV. Organizations became more viable (more capacity in human resources, financial, external relations, and strategic management), but also more unstable (large growth in paid staff and board members), and showed more capacity in HIV knowledge environments (especially less stigma and more sensitivity to diverse populations). The results suggest that capacity can expand over a short period of time, but as capacity increases, organizational viability/stability and HIV knowledge environments change, meaning that different types of technical assistance would be needed for sustainability. PMID:17159469

  14. Using a Regional Cluster of AmeriFlux Sites in Central California to Advance Our Knowledge on Decadal-Scale Ecosystem-Atmosphere Carbon Dioxide Exchange

    SciTech Connect

    Baldocchi, Dennis

    2015-03-24

    Continuous eddy convariance measurements of carbon dioxide, water vapor and heat were measured continuously between an oak savanna and an annual grassland in California over a 4 year period. These systems serve as representative sites for biomes in Mediterranean climates and experience much seasonal and inter-annual variability in temperature and precipitation. These sites hence serve as natural laboratories for how whole ecosystem will respond to warmer and drier conditions. The savanna proved to be a moderate sink of carbon, taking up about 150 gC m-2y-1 compared to the annual grassland, which tended to be carbon neutral and often a source during drier years. But this carbon sink by the savanna came at a cost. This ecosystem used about 100 mm more water per year than the grassland. And because the savanna was darker and rougher its air temperature was about 0.5 C warmer. In addition to our flux measurements, we collected vast amounts of ancillary data to interpret the site and fluxes, making this site a key site for model validation and parameterization. Datasets consist of terrestrial and airborne lidar for determining canopy structure, ground penetrating radar data on root distribution, phenology cameras monitoring leaf area index and its seasonality, predawn water potential, soil moisture, stem diameter and physiological capacity of photosynthesis.

  15. Balancing Tradeoffs in Ecosystem Functions and Services in Grassland Management

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Managed grasslands are increasingly expected to provide ecosystem services beyond the traditional provision of food, feed, and fiber. Grassland systems can provide ecosystem services such as soil conservation, water quality protection, wildlife conservation, pleasing landscapes, soil carbon storage,...

  16. Black-tailed prairie dogs, cattle, and the conservation of North America's arid grasslands.

    PubMed

    Sierra-Corona, Rodrigo; Davidson, Ana; Fredrickson, Ed L; Luna-Soria, Hugo; Suzan-Azpiri, Humberto; Ponce-Guevara, Eduardo; Ceballos, Gerardo

    2015-01-01

    Prairie dogs (Cynomys spp.) have been eliminated from over 95% of their historic range in large part from direct eradication campaigns to reduce their purported competition with cattle for forage. Despite the longstanding importance of this issue to grassland management and conservation, the ecological interactions between cattle and prairie dogs have not been well examined. We address this issue through two complementary experiments to determine if cattle and prairie dogs form a mutualistic grazing association similar to that between prairie dogs and American bison. Our experimental results show that cattle preferentially graze along prairie dog colony edges and use their colony centers for resting, resembling the mutualistic relationship prairie dogs have with American bison. Our results also show that prairie dog colonies are not only an important component of the grassland mosaic for maintaining biodiversity, but also provide benefits to cattle, thereby challenging the long-standing view of prairie dogs as an undesirable pest species in grasslands. PMID:25760377

  17. Black-Tailed Prairie Dogs, Cattle, and the Conservation of North America’s Arid Grasslands

    PubMed Central

    Sierra–Corona, Rodrigo; Davidson, Ana; Fredrickson, Ed L.; Luna-Soria, Hugo; Suzan-Azpiri, Humberto; Ponce-Guevara, Eduardo; Ceballos, Gerardo

    2015-01-01

    Prairie dogs (Cynomys spp.) have been eliminated from over 95% of their historic range in large part from direct eradication campaigns to reduce their purported competition with cattle for forage. Despite the longstanding importance of this issue to grassland management and conservation, the ecological interactions between cattle and prairie dogs have not been well examined. We address this issue through two complementary experiments to determine if cattle and prairie dogs form a mutualistic grazing association similar to that between prairie dogs and American bison. Our experimental results show that cattle preferentially graze along prairie dog colony edges and use their colony centers for resting, resembling the mutualistic relationship prairie dogs have with American bison. Our results also show that prairie dog colonies are not only an important component of the grassland mosaic for maintaining biodiversity, but also provide benefits to cattle, thereby challenging the long-standing view of prairie dogs as an undesirable pest species in grasslands. PMID:25760377

  18. Contrasting above- and belowground sensitivity of three Great Plains grasslands to altered rainfall regimes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To assess primary productivity responses to increases in precipitation amount and altered rainfall patterns, we conducted an experiment in 2011 and 2012 in shortgrass prairie (SGP; C4 dominated; Central Plains Experimental Grassland), northern mixed grass prairie (NMP; C3 dominated; Fort Keogh Lives...

  19. Bird Communities and Biomass Yields in Potential Bioenergy Grasslands

    PubMed Central

    Blank, Peter J.; Sample, David W.; Williams, Carol L.; Turner, Monica G.

    2014-01-01

    Demand for bioenergy is increasing, but the ecological consequences of bioenergy crop production on working lands remain unresolved. Corn is currently a dominant bioenergy crop, but perennial grasslands could produce renewable bioenergy resources and enhance biodiversity. Grassland bird populations have declined in recent decades and may particularly benefit from perennial grasslands grown for bioenergy. We asked how breeding bird community assemblages, vegetation characteristics, and biomass yields varied among three types of potential bioenergy grassland fields (grass monocultures, grass-dominated fields, and forb-dominated fields), and assessed tradeoffs between grassland biomass production and bird habitat. We also compared the bird communities in grassland fields to nearby cornfields. Cornfields had few birds compared to perennial grassland fields. Ten bird Species of Greatest Conservation Need (SGCN) were observed in perennial grassland fields. Bird species richness and total bird density increased with forb cover and were greater in forb-dominated fields than grass monocultures. SGCN density declined with increasing vertical vegetation density, indicating that tall, dense grassland fields managed for maximum biomass yield would be of lesser value to imperiled grassland bird species. The proportion of grassland habitat within 1 km of study sites was positively associated with bird species richness and the density of total birds and SGCNs, suggesting that grassland bioenergy fields may be more beneficial for grassland birds if they are established near other grassland parcels. Predicted total bird density peaked below maximum biomass yields and predicted SGCN density was negatively related to biomass yields. Our results indicate that perennial grassland fields could produce bioenergy feedstocks while providing bird habitat. Bioenergy grasslands promote agricultural multifunctionality and conservation of biodiversity in working landscapes. PMID:25299593

  20. Precipitation and soil impacts on partitioning of subsurface moisture in Avena barbata: Observations from a greenhouse experiment

    SciTech Connect

    Salve, R.; Torn, M.S.

    2011-03-01

    The primary objective of this study was to assess the impact of two grassland soils and precipitation regimes on soil-moisture dynamics. We set up an experiment in a greenhouse, and monitored soil moisture dynamics in mesocosms planted with Avena barbata, an annual species found in California grasslands. By repeating the precipitation input at regular intervals, we were able to observe plant manipulation of soil moisture during well-defined periods during the growing season. We found that the amount of water partitioned to evapotranspiration, seepage, and soil storage varied among different growth stages. Further, both soil type and precipitation regimes had a significant impact on redistributing soil moisture. Whereas in the low-precipitation treatments most water was released to the atmosphere as evapotranspiration, major losses from the high-precipitation treatment occurred as gravity drainage. Observations from this study emphasize the importance of understanding intra-seasonal relationships between vegetation, soil, and water.

  1. Visibility in California

    SciTech Connect

    Trijonis, J.

    1982-02-01

    A comprehensive study is conducted of visibility in California using prevailing visibility measurements at 67 weather stations in conjunction with data on particulate concentrations and meteorology. The weather station visibility data, when handled with special techniques that account for the nature of visibility reporting practices, prove to be of very good quality for the purposes of most of the analyses that are attempted. It is found that the most important meteorological parameters with respect to visibility are relative humidity, temperature, and special weather events (especially fog). A detailed isopleth map of visibility within California, when compared with earlier work on nationwide visibility, reveals that California experiences far more severe and complex spatial gradients in visibility than those observed anywhere else in the U.S. Two major pockets of heavy man-made visibility impact in California are the Los Angeles basin and the San Joaquin Valley. The spatial, seasonal, and diurnal patterns of visibility are found to be readily explainable in terms of corresponding patterns in emissions, air quality, and meteorology. Regression analyses relating visibility to relative humidity and aerosol concentrations produce high levels of correlation and physically reasonable regression coefficients; these analyses indicate that secondary aerosols are major contributors to visibility reduction in California. An analysis of long-term visibility trends from 1949 to 1976 reveals several interesting features in historical visibility changes for California.

  2. Ungulate vs. landscape control of soil C and N processes in grasslands of Yellowstone National Park

    SciTech Connect

    Frank, D.A.; Groffman, P.M.

    1998-10-01

    Within large grassland ecosystems, climatic and topographic gradients are considered the primary controls of soil processes. Ungulates also can influence soil dynamics; however the relative contribution of large herbivores to controlling grassland soil processes remains largely unknown. In this study, the authors compared the effects of native migratory ungulates and variable site (landscape) conditions, caused by combined climatic and topographic variability, on grassland of the northern winter range of Yellowstone National Park by determining soil C and N dynamics inside and outside 33--37 yr exclosures at seven diverse sites. Sites included hilltop, slope, and slope bottom positions across a climatic gradient and represented among the driest and wettest grasslands on the northern winter range. The authors performed two experiments: (1) a 12-mo in situ net N mineralization study and (2) a long-term (62-wk) laboratory incubation to measure potential N mineralization and microbial respiration. Results from the in situ experiment indicated that average net N mineralization among grazed plots was double that of fenced, ungrazed plots (1.9 g N{center_dot}m{sup {minus}2}{center_dot}yr{sup {minus}1}). Mean grazer enhancement of net N mineralization across sites (1.9 g N{center_dot}m{sup {minus}2}{center_dot}yr{sup {minus}1}), approached the maximum difference in net N mineralization among fenced plots (2.2 g N{center_dot}m{sup {minus}2}{center_dot}yr{sup {minus}1}), i.e., the greatest landscape effect observed. Furthermore, ungulates substantially increased between-site variation in mineralization; grazed grassland, 1 SD = 2.2 g N{center_dot}m{sup {minus}2}{center_dot}yr{sup {minus}1}, fenced grassland, 1 SD = 0.85 g N{center_dot}m{sup {minus}2}{center_dot}yr{sup {minus}1}.

  3. Grazing effects on carbon fluxes in a northern China grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grazing is a widespread use of grasslands in northern China, but if stocking rate exceeds grassland carrying capacity, degradation and desertification can occur. As a result, grazing management is critical and can play a significant role in driving C sink and source activity in grassland ecosystems...

  4. Grassland birds: An overview of threats and recommended management strategies

    USGS Publications Warehouse

    Vickery, P.D.; Herkert, J.R.; Knopf, F.L.; Ruth, J.; Keller, C.E.

    2000-01-01

    Grassland ecosystems are dependent on periodic disturbance for habitat maintenance. Historically, grazing by native herbivores and prairie fires were the agents principally responsible for maintaining grassland areas. However, elimination of native herbivores, wide-spread fire suppression, and conversion for agriculture have greatly altered grasslands in the United States and Canada. Because of these landscape changes, many grassland birds are increasingly dependent on land managers for habitat creation, maintenance, and health. Grazing, prescribed burning, and mowing/haying are the most frequently used, and versatile, grassland management techniques. Grassland birds prefer a wide range of grass heights and densities, with some species preferring short sparse vegetation, and others preferring taller, more dense vegetation. Due to differences in species habitat preferences and regional differences in soils and floristics, the responses of individual grassland species to specific grassland management practices can be variable and often are regionally dependent. As a result, management of grassland areas is best directed toward the creation of a mosaic of grassland habitat types. This habitat mosaic is probably best maintained through some type of rotational management system in which sections of large grassland areas receive management on a regular schedule. Such a rotational system would provide a variety of habitat types in every year, would ensure the availability of suitable habitat for birds at either end of the grassland management spectrum, and also would provide habitat for birds whose preferences lie between these extremes.

  5. Report for borehole explosion data acquired in the 1999 Los Angeles Region Seismic Experiment (LARSE II), Southern California; Part II, Data tables and plots

    USGS Publications Warehouse

    Murphy, Janice M.; Fuis, Gary S.; Okaya, D.A.; Thygesen, Kristina; Baher, Shirley A.; Rybert, Trond; Kaip, Galen; Fort, Michael D.; Asudeh, Isa; Sell, Russell

    2002-01-01

    The Los Angeles Region Seismic Experiment (LARSE), a joint project of the U.S. Geological Survey (USGS) and the Southern California Earthquake Center (SCEC), was conducted to produce seismic images of the subsurface in the Los Angeles region. Primary targets were major fault systems and sedimentary basins; the goal of the project was to address the earthquake hazard posed by these geologic features. The first phase of data collection (LARSE 1) was completed in 1994; the second phase (LARSE 2) was completed in 1999. A description of the 1999 survey and an overview of both phase I and II is given in Fuis and others (2001). In this report, we present the technical details for the explosion data collected in 1999.

  6. Analysis of existing data from a Distributed Acoustic Sensing experiment at Garner Valley, California using noise correlation functions (PoroTomo Substask 3.2)

    DOE Data Explorer

    Xiangfang Zeng

    2015-03-26

    In September 2013, an experiment using Distributed Acoustic Sensing (DAS) was conducted at Garner Valley, a test site of the University of California Santa Barbara (Lancelle et al., 2014). This submission includes noise cross-correlation functions (NCF) . Each file includes a NCF between two channels. The name of each channel denotes the distance in meters from starting point of the fiber-optic cable. Lancelle, C., N. Lord, H. Wang, D. Fratta, R. Nigbor, A. Chalari, R. Karaulanov, J. Baldwin, and E. Castongia (2014), Directivity and Sensitivity of Fiber-Optic Cable Measuring Ground Motion using a Distributed Acoustic Sensing Array (abstract # NS31C-3935), AGU Fall Meeting. 
https://agu.confex.com/agu/fm14/meetingapp.cgi#Paper/19828 The e-poster is available at: https://agu.confex.com/data/handout/agu/fm14/Paper_19828_handout_696_0.pdf

  7. Dry deposition of pan to grassland vegetation

    SciTech Connect

    Doskey, P.V.; Wesely, M.L.; Cook, D.R.; Gao, W.

    1994-01-01

    Peroxyacetyl nitrate or PAN (CH{sub 3}C(O)OONO{sub 2}) is formed in the lower troposphere via photochemical reactions involving nitrogen oxides (NO{sub x}) and non-methane hydrocarbons (NMHCs). PAN has a lifetime in the free troposphere of about three months and is removed by photolysis or reaction with OH. Dry deposition will decrease its lifetime, although the few measurements that have been made indicate that this process is slow. Measurements of the uptake of PAN by alfalfa in growth chambers indicated that the dry deposition velocity (downward flux divided by concentration at a specified height) was 0.75 cm s{sup {minus}1}. Garland and Penkett measured a dry deposition velocity of 0.25 cm s{sup {minus}1} for PAN to grass and soil in a return-flow wind tunnel. Shepson et al. (1992) analyzed trends of PAN and O{sub 3} concentrations in the stable nocturnal boundary layer over mixed deciduous/coniferous forests at night, when leaf stomata were closed, and concluded that the deposition velocity for PAN was at least 0.5 cm s{sup {minus}1}. We measured the dry deposition velocity of PAN to a grassland site in the midwestern United States with a modified Bowen ratio technique. Experiments were conducted on selected days during September, October, and November of 1990. An energy balance Bowen ratio station was used to observe the differences in air temperature and water vapor content between heights of 3.0 and 0.92 m and to evaluate the surface energy balance. Air samples collected at the same two heights in Teflon {reg_sign} bags were analyzed for PAN by a gas chromatographic technique. We present an example of the variations of PAN concentrations and gradients observed during the day and compare measurements of the dry deposition velocity to expectations based on the physicochemical properties of PAN.

  8. Ammonia sources and sinks in an intensively managed grassland canopy

    NASA Astrophysics Data System (ADS)

    David, M.; Loubet, B.; Cellier, P.; Mattsson, M.; Schjoerring, J. K.; Nemitz, E.; Roche, R.; Riedo, M.; Sutton, M. A.

    2009-09-01

    Grasslands represent canopies with a complex structure where sources and sinks of ammonia (NH3) may coexist at the plant level. Moreover, management practices such as mowing, hay production and grazing may change the composition of the sward and hence the source-sink relationship at the canopy level as well as the interaction with the atmosphere. There is therefore a need to understand the exchange of ammonia between grasslands and the atmosphere better, especially regarding the location and magnitude of sources and sinks. Fluxes of atmospheric NH3 within a grassland canopy were assessed in the field and under controlled conditions using a dynamic chamber technique (cuvette). These cuvette measurements were combined with extraction techniques to estimate the ammonium (NH4+) concentration and the pH of a given part of the plant or soil, leading to an estimated ammonia compensation point (Cp). The combination of the cuvette and the extraction techniques was used to identify the potential sources and sinks of NH3 within the different compartments of the grassland: the soil, the litter or senescent "litter leaves", and the functioning "green leaves". A set of six field experiments and six laboratory experiments were performed in which the different compartments were either added or removed from the cuvettes. The results show that the cuvette measurements agree with the extraction technique in ranking the strength of compartment sources. It suggests that in the studied grassland the green leaves were mostly a sink for NH3 with a compensation point around 0.1-0.4 μg m-3 and an NH3 flux of 6 to 7 ng m-2 s-1. Cutting of the grass did not increase the NH3 fluxes of the green leaves. The litter was found to be the largest source of NH3 in the canopy, with a Cp of up to 1000 μg m-3 NH3 and an NH3 flux up to 90 ng m-2 s-1. The litter was found to be a much smaller NH3 source when dried (Cp=160 μg m-3 and FNH3=35 ng m-2 s-1 NH3). Moreover emissions from the litter were found

  9. Conspecific attraction in a grassland bird, the Baird's Sparrow

    USGS Publications Warehouse

    Ahlering, M.A.; Johnson, D.H.; Faaborg, J.

    2006-01-01

    Territorial songbirds generally use song to defend territories and attract mates, but conspecific song may also serve as a cue to attract other male songbirds to a breeding site. Although known to occur in some colonial and forest-associated species, only recently have investigators examined conspecific attraction in grassland species. We used a playback experiment to examine the possible role of conspecific attraction for males searching for potentially suitable breeding habitat in a grassland specialist, the Baird's Sparrow (Ammodramus bairdii). Experimental playback plots and control plots with similar landscape and vegetation characteristics were established at two sites in North Dakota. Baird's Sparrows colonized three of six experimental plots and none of six control plots. Males on experimental plots established territories adjacent to the playback stations and were sometimes observed counter-singing with the playback of conspecific songs. Vegetation characteristics were similar on all study plots, and did not explain differences in bird density on our treatment plots. Although we found that playback of conspecific songs attracted male Baird's Sparrows to previously unoccupied, potentially suitable habitat, further experiments are needed to examine the importance of conspecific attraction relative to other cues that birds may use, such as vegetation features. The conservation and management implications of conspecific attraction are not completely understood, but the presence of conspecifics should be considered as a potential cue in habitat selection by all species of birds. ?? 2006 The Author(s).

  10. Grassland biodiversity bounces back from long-term nitrogen addition.

    PubMed

    Storkey, J; Macdonald, A J; Poulton, P R; Scott, T; Köhler, I H; Schnyder, H; Goulding, K W T; Crawley, M J

    2015-12-17

    The negative effect of increasing atmospheric nitrogen (N) pollution on grassland biodiversity is now incontrovertible. However, the recent introduction of cleaner technologies in the UK has led to reductions in the emissions of nitrogen oxides, with concomitant decreases in N deposition. The degree to which grassland biodiversity can be expected to 'bounce back' in response to these improvements in air quality is uncertain, with a suggestion that long-term chronic N addition may lead to an alternative low biodiversity state. Here we present evidence from the 160-year-old Park Grass Experiment at Rothamsted Research, UK, that shows a positive response of biodiversity to reducing N addition from either atmospheric pollution or fertilizers. The proportion of legumes, species richness and diversity increased across the experiment between 1991 and 2012 as both wet and dry N deposition declined. Plots that stopped receiving inorganic N fertilizer in 1989 recovered much of the diversity that had been lost, especially if limed. There was no evidence that chronic N addition has resulted in an alternative low biodiversity state on the Park Grass plots, except where there has been extreme acidification, although it is likely that the recovery of plant communities has been facilitated by the twice-yearly mowing and removal of biomass. This may also explain why a comparable response of plant communities to reduced N inputs has yet to be observed in the wider landscape. PMID:26633635

  11. Grassland biodiversity bounces back from long-term nitrogen addition

    NASA Astrophysics Data System (ADS)

    Storkey, J.; MacDonald, A. J.; Poulton, P. R.; Scott, T.; Köhler, I. H.; Schnyder, H.; Goulding, K. W. T.; Crawley, M. J.

    2015-12-01

    The negative effect of increasing atmospheric nitrogen (N) pollution on grassland biodiversity is now incontrovertible. However, the recent introduction of cleaner technologies in the UK has led to reductions in the emissions of nitrogen oxides, with concomitant decreases in N deposition. The degree to which grassland biodiversity can be expected to ‘bounce back’ in response to these improvements in air quality is uncertain, with a suggestion that long-term chronic N addition may lead to an alternative low biodiversity state. Here we present evidence from the 160-year-old Park Grass Experiment at Rothamsted Research, UK, that shows a positive response of biodiversity to reducing N addition from either atmospheric pollution or fertilizers. The proportion of legumes, species richness and diversity increased across the experiment between 1991 and 2012 as both wet and dry N deposition declined. Plots that stopped receiving inorganic N fertilizer in 1989 recovered much of the diversity that had been lost, especially if limed. There was no evidence that chronic N addition has resulted in an alternative low biodiversity state on the Park Grass plots, except where there has been extreme acidification, although it is likely that the recovery of plant communities has been facilitated by the twice-yearly mowing and removal of biomass. This may also explain why a comparable response of plant communities to reduced N inputs has yet to be observed in the wider landscape.

  12. Image classification approach for automatic identification of grassland weeds

    NASA Astrophysics Data System (ADS)

    Gebhardt, Steffen; Kühbauch, Walter

    2006-08-01

    The potential of digital image processing for weed mapping in arable crops has widely been investigated in the last decades. In grassland farming these techniques are rarely applied so far. The project presented here focuses on the automatic identification of one of the most invasive and persistent grassland weed species, the broad-leaved dock (Rumex obtusifolius L.) in complex mixtures of grass and herbs. A total of 108 RGB-images were acquired in near range from a field experiment under constant illumination conditions using a commercial digital camera. The objects of interest were separated from the background by transforming the 24 bit RGB-images into 8 bit intensities and then calculating the local homogeneity images. These images were binarised by applying a dynamic grey value threshold. Finally, morphological opening was applied to the binary images. The remaining contiguous regions were considered to be objects. In order to classify these objects into 3 different weed species, a soil and a residue class, a total of 17 object-features related to shape, color and texture of the weeds were extracted. Using MANOVA, 12 of them were identified which contribute to classification. Maximum-likelihood classification was conducted to discriminate the weed species. The total classification rate across all classes ranged from 76 % to 83 %. The classification of Rumex obtusifolius achieved detection rates between 85 % and 93 % by misclassifications below 10 %. Further, Rumex obtusifolius distribution and the density maps were generated based on classification results and transformation of image coordinates into Gauss-Krueger system. These promising results show the high potential of image analysis for weed mapping in grassland and the implementation of site-specific herbicide spraying.

  13. Land use affects the resistance and resilience of carbon dynamics of mountain grassland to extreme drought

    NASA Astrophysics Data System (ADS)

    Ingrisch, Johannes; Karlowsky, Stefan; Hasibeder, Roland; Anadon-Rosell, Alba; Augusti, Angela; Scheld, Sarah; König, Alexander; Gleixner, Gerd; Bahn, Michael

    2015-04-01

    Climatic extremes like droughts are expected to occur more frequently and to be more severe in a future climate and have been shown to strongly affect the carbon (C) cycle. Few studies have so far explored how the management intensity of ecosystems and land-use changes alter C cycle responses to extreme climatic events. In many mountain areas land-use changes have been taking place at a rapid pace and have altered plant species composition and biogeochemical cycles. It is still unknown whether and how abandonment of mountain grasslands affects the resistance and the resilience of carbon dynamics to extreme drought. We carried out an in situ experiment to test the hypothesis that abandonment increases the resistance of grassland C dynamics to extreme drought, but decreases its resilience (i.e. post-drought recovery). In a common garden experiment at a mountain meadow in the Austrian Central Alps we exposed large intact monoliths from the meadow and a nearby abandoned grassland to extreme drought conditions during the main growth period in late spring. We measured above- and belowground productivity and net ecosystem exchange and its components over the course of the drought and during the recovery to assess and quantify their resistance and resilience. Furthermore, we analysed the coupling of the two major ecosystem CO2 fluxes, photosynthesis and soil respiration, as based on 13CO2 pulse labelling campaigns at peak drought and during post-drought recovery using isotope laser spectroscopy. Four weeks of early season drought induced a strong decrease of aboveground biomass at the mountain meadow, whereas no effect was observed for the abandoned grassland. At peak drought gross primary productivity was reduced at both grasslands compared to the respective controls, but with a stronger decrease at the meadow (80%) compared to the abandoned grassland (60%). The same pattern was observed for ecosystem respiration. However, the effect was less pronounced compared to carbon

  14. California's Water Problems.

    ERIC Educational Resources Information Center

    Wheatley, Judy; Sudman, Rita Schmidt, Ed.

    This packet of instructional materials is designed to give social science students in grades 6-9 a first-hand experience in working out solutions to real-life problems involving the management of California's water. Students work in groups on one of three problems presented in the packet: (1) the management of the Sacramento-San Joaquin Delta that…

  15. A Comparison of a Sub-Population of Santa Monica College Students to Other Community College Students in the Southern California Area: An Analysis of the Results from the Community College Student Experiences Questionnaire.

    ERIC Educational Resources Information Center

    Ackermann, Susan P.

    Drawing from a nationwide pilot test of the Community College Student Experiences Questionnaire (CCSEQ), a study was conducted to compare Santa Monica College (SMC) students (N=106) with students attending nine other Southern California community colleges (N=498). The CCSEQ was designed to provide information on the relationship between students'…

  16. Water and Productivity of Floodplain Grasslands: Exploring Linkages through Experimentations and Models in the Tana River Delta, Kenya

    NASA Astrophysics Data System (ADS)

    Leauthaud, C.; Musila, W.; Kergoat, L.; Hiernaux, P.; Manuela, G.; Duvail, S.

    2014-12-01

    Floodplain grasslands have one of the highest productivities of non-cultivated ecosystems on Earth. They procure a wide variety of benefits to human beings. In Eastern Africa, grasslands of Echinochloa stagnina are primordial for pastoralists as highly productive dry-season grazing zones. Regular flooding is a critical property in maintaining their productivity and resulting services. Yet, construction of hydrologic infrastructure modifies the flooding regime of rivers and the consequences on downstream floodplain grasslands need to be assessed. This presentation focuses on quantifying the productivity of the floodplain grasslands in the Tana River Delta, Kenya, in order to assess potential changes under varying flooding regimes. The interactions between growth and floods are explored firstly at an experimental site, then through the construction of a process-based plant growth model adapted to floodplain grasslands. The 15-month experiment consisted in quantifying daily growth rates under various rainfall, irrigation, cutting and flooding regimes . Floods increased growth rates three-folds, and high productivities were maintained after the floods. The cutting regime and contribution of non-flood water also influenced productivity. Modelling allowed exploring the underlying processes explaining such behaviour. In an exploratory endeavour, the productivity of the grassland at the ecosystem scale was assessed with the model for a variety of flood and non-flooded scenarios. Decreasing floods led to a drop in annual productivity that could have serious consequences for the livestock keeping activities of the zone. This research highlights the importance of floods in the maintenance of high productivities for a floodplain grassland typical of East Africa, and maybe of the Sahelian band. The model, once further validated, could be used on other floodplain grasslands, such as those of the Niger delta. Results for the Tana River Delta would need to be discussed with the

  17. Evidence of physiological decoupling from grassland ecosystem drivers by an encroaching woody shrub.

    PubMed

    Nippert, Jesse B; Ocheltree, Troy W; Orozco, Graciela L; Ratajczak, Zak; Ling, Bohua; Skibbe, Adam M

    2013-01-01

    Shrub encroachment of grasslands is a transformative ecological process by which native woody species increase in cover and frequency and replace the herbaceous community. Mechanisms of encroachment are typically assessed using temporal data or experimental manipulations, with few large spatial assessments of shrub physiology. In a mesic grassland in North America, we measured inter- and intra-annual variability in leaf δ(13)C in Cornus drummondii across a grassland landscape with varying fire frequency, presence of large grazers and topographic variability. This assessment of changes in individual shrub physiology is the largest spatial and temporal assessment recorded to date. Despite a doubling of annual rainfall (in 2008 versus 2011), leaf δ(13)C was statistically similar among and within years from 2008-11 (range of -28 to -27‰). A topography*grazing interaction was present, with higher leaf δ(13)C in locations that typically have more bare soil and higher sensible heat in the growing season (upland topographic positions and grazed grasslands). Leaf δ(13)C from slopes varied among grazing contrasts, with upland and slope leaf δ(13)C more similar in ungrazed locations, while slopes and lowlands were more similar in grazed locations. In 2011, canopy greenness (normalized difference vegetation index - NDVI) was assessed at the centroid of individual shrubs using high-resolution hyperspectral imagery. Canopy greenness was highest mid-summer, likely reflecting temporal periods when C assimilation rates were highest. Similar to patterns seen in leaf δ(13)C, NDVI was highest in locations that typically experience lowest sensible heat (lowlands and ungrazed). The ability of Cornus drummondii to decouple leaf physiological responses from climate variability and fire frequency is a likely contributor to the increase in cover and frequency of this shrub species in mesic grassland and may be generalizable to other grasslands undergoing woody encroachment. PMID

  18. Evolution of Grasses and Grassland Ecosystems

    NASA Astrophysics Data System (ADS)

    Strömberg, Caroline A. E.

    2011-05-01

    The evolution and subsequent ecological expansion of grasses (Poaceae) since the Late Cretaceous have resulted in the establishment of one of Earth's dominant biomes, the temperate and tropical grasslands, at the expense of forests. In the past decades, several new approaches have been applied to the fossil record of grasses to elucidate the patterns and processes of this ecosystem transformation. The data indicate that the development of grassland ecosystems on most continents was a multistage process involving the Paleogene appearance of (C3 and C4) open-habitat grasses, the mid-late Cenozoic spread of C3 grass-dominated habitats, and, finally, the Late Neogene expansion of C4 grasses at tropical-subtropical latitudes. The evolution of herbivores adapted to grasslands did not necessarily coincide with the spread of open-habitat grasses. In addition, the timing of these evolutionary and ecological events varied between regions. Consequently, region-by-region investigations using both direct (plant fossils) and indirect (e.g., stable carbon isotopes, faunas) evidence are required for a full understanding of the tempo and mode of grass and grassland evolution.

  19. Implementation of grassland conservation practices in EQIP

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many conservation practices are implemented with financial and technical assistance from the Environmental Quality Incentives Program (EQIP), administered by the USDA. The extent to which practices specific to grasslands and pasture-based production systems have been adopted is not clear. We used ...

  20. Grasslands and groundwater: what's the connection?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grasslands, either improved pastures or native rangelands, are a crucial component of the hydrologic system, and provide vast surface areas for infiltration and groundwater recharge from precipitation. The soil profile also behaves as a filter that removes many contaminants from percolating water a...

  1. Soil quality under mixed grassland - Cropland environments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Native grassland environments (i.e. prairies) are typically characterized by soils with high quality. Historical cultivation of prairies has led to soil resources that are now in a compromised state of health. The loss of soil organic matter that led to large biopores and a favorable rooting envir...

  2. Contrasting microbial biogeographical patterns between anthropogenic subalpine grasslands and natural alpine grasslands.

    PubMed

    Geremia, Roberto A; Pușcaș, Mihai; Zinger, Lucie; Bonneville, Jean-Marc; Choler, Philippe

    2016-02-01

    The effect of plant species composition on soil microbial communities was studied at the multiregional level. We compared the soil microbial communities of alpine natural grasslands dominated by Carex curvula and anthropogenic subalpine pastures dominated by Nardus stricta. We conducted paired sampling across the Carpathians and the Alps and used Illumina sequencing to reveal the molecular diversity of soil microbes. We found that bacterial and fungal communities exhibited contrasting regional distributions and that the distribution in each grassland is well discriminated. Beta diversity of microbial communities was much higher in C. curvula grasslands due to a marked regional effect. The composition of grassland-type core microbiomes suggest that C. curvula, and N. stricta to a lesser extent, tend to select a cohort of microbes related to antibiosis/exclusion, pathogenesis and endophytism. We discuss these findings in light of the postglacial history of the studied grasslands, the habitat connectivity and the disturbance regimes. Human-induced disturbance in the subalpine belt of European mountains has led to homogeneous soil microbial communities at large biogeographical scales. Our results confirm the overarching role of the dominant grassland plant species in the distribution of microbial communities and highlight the relevance of biogeographical history. PMID:26443332

  3. Negative global phosphorus budgets challenge sustainable intensification of grasslands.

    PubMed

    Sattari, S Z; Bouwman, A F; Martinez Rodríguez, R; Beusen, A H W; van Ittersum, M K

    2016-01-01

    Grasslands provide grass and fodder to sustain the growing need for ruminant meat and milk. Soil nutrients in grasslands are removed through withdrawal in these livestock products and through animal manure that originates from grasslands and is spread in croplands. This leads to loss of soil fertility, because globally most grasslands receive no mineral fertilizer. Here we show that phosphorus (P) inputs (mineral and organic) in global grasslands will have to increase more than fourfold in 2050 relative to 2005 to achieve an anticipated 80% increase in grass production (for milk and meat), while maintaining the soil P status. Combined with requirements for cropland, we estimate that mineral P fertilizer use must double by 2050 to sustain future crop and grassland production. Our findings point to the need to better understand the role of grasslands and their soil P status and their importance for global food security. PMID:26882144

  4. Negative global phosphorus budgets challenge sustainable intensification of grasslands

    PubMed Central

    Sattari, S. Z.; Bouwman, A. F.; Martinez Rodríguez, R.; Beusen, A. H. W.; van Ittersum, M. K.

    2016-01-01

    Grasslands provide grass and fodder to sustain the growing need for ruminant meat and milk. Soil nutrients in grasslands are removed through withdrawal in these livestock products and through animal manure that originates from grasslands and is spread in croplands. This leads to loss of soil fertility, because globally most grasslands receive no mineral fertilizer. Here we show that phosphorus (P) inputs (mineral and organic) in global grasslands will have to increase more than fourfold in 2050 relative to 2005 to achieve an anticipated 80% increase in grass production (for milk and meat), while maintaining the soil P status. Combined with requirements for cropland, we estimate that mineral P fertilizer use must double by 2050 to sustain future crop and grassland production. Our findings point to the need to better understand the role of grasslands and their soil P status and their importance for global food security. PMID:26882144

  5. California Fires

    Atmospheric Science Data Center

    2014-05-15

    ... title:  Smoke from Station Fire Blankets Southern California     View Larger Image ... that had not burned in decades, and years of extended drought contributed to the explosive growth of wildfires throughout southern ...

  6. Leaf and ecosystem response to soil water availability in mountain grasslands

    PubMed Central

    Brilli, Federico; Hörtnagl, Lukas; Hammerle, Albin; Haslwanter, Alois; Hansel, Armin; Loreto, Francesco; Wohlfahrt, Georg

    2014-01-01

    Climate change is expected to affect the Alps by increasing the frequency and intensity of summer drought events with negative impacts on ecosystem water resources. The response of CO2 and H2O exchange of a mountain grassland to natural fluctuations of soil water content was evaluated during 2001-2009. In addition, the physiological performance of individual mountain forb and graminoid plant species under progressive soil water shortage was explored in a laboratory drought experiment. During the 9-year study period the natural occurrence of moderately to extremely dry periods did not lead to substantial reductions in net ecosystem CO2 exchange and evapotranspiration. Laboratory drought experiments confirmed that all the surveyed grassland plant species were insensitive to progressive soil drying until very low soil water contents (<0.01 m3 m−3) were reached after several days of drought. In field conditions, such a low threshold was never reached. Re-watering after a short-term drought event (5±1 days) resulted in a fast and complete recovery of the leaf CO2 and H2O gas exchange of the investigated plant species. We conclude that the present-day frequency and intensity of dry periods does not substantially affect the functioning of the investigated grassland ecosystem. During dry periods the observed “water spending” strategy employed by the investigated mountain grassland species is expected to provide a cooling feedback on climate warming, but may have negative consequences for down-stream water users. PMID:24465071

  7. Soil organisms shape the competition between grassland plant species.

    PubMed

    Sabais, Alexander C W; Eisenhauer, Nico; König, Stephan; Renker, Carsten; Buscot, François; Scheu, Stefan

    2012-12-01

    Decomposers and arbuscular mycorrhizal fungi (AMF) both determine plant nutrition; however, little is known about their interactive effects on plant communities. We set up a greenhouse experiment to study effects of plant competition (one- and two-species treatments), Collembola (Heteromurus nitidus and Protaphorura armata), and AMF (Glomus intraradices) on the performance (above- and belowground productivity and nutrient uptake) of three grassland plant species (Lolium perenne, Trifolium pratense, and Plantago lanceolata) belonging to three dominant plant functional groups (grasses, legumes, and herbs). Generally, L. perenne benefited from being released from intraspecific competition in the presence of T. pratense and P. lanceolata. However, the presence of AMF increased the competitive strength of P. lanceolata and T. pratense against L. perenne and also modified the effects of Collembola on plant productivity. The colonization of roots by AMF was reduced in treatments with two plant species suggesting that plant infection by AMF was modified by interspecific plant interactions. Collembola did not affect total colonization of roots by AMF, but increased the number of mycorrhizal vesicles in P. lanceolata. AMF and Collembola both enhanced the amount of N and P in plant shoot tissue, but impacts of Collembola were less pronounced in the presence of AMF. Overall, the results suggest that, by differentially affecting the nutrient acquisition and performance of plant species, AMF and Collembola interactively modify plant competition and shape the composition of grassland plant communities. The results suggest that mechanisms shaping plant community composition can only be understood when complex belowground interactions are considered. PMID:22678109

  8. Nitrogen acquisition by plants and microorganisms in a temperate grassland

    PubMed Central

    Liu, Qianyuan; Qiao, Na; Xu, Xingliang; Xin, Xiaoping; Han, Jessie Yc; Tian, Yuqiang; Ouyang, Hua; Kuzyakov, Yakov

    2016-01-01

    Nitrogen (N) limitation is common in most terrestrial ecosystems, often leading to strong competition between microorganisms and plants. The mechanisms of niche differentiation to reduce this competition remain unclear. Short-term 15N experiments with NH4+, NO3−, and glycine were conducted in July, August and September in a temperate grassland to evaluate the chemical, spatial and temporal niche differentiation by competition between plants and microorganisms for N. Microorganisms preferred NH4+ and NO3−, while plants preferred NO3−. Both plants and microorganisms acquired more N in August and September than in July. The soil depth had no significant effects on microbial uptake, but significantly affected plant N uptake. Plants acquired 67% of their N from the 0–5 cm soil layer and 33% from the 5–15 cm layer. The amount of N taken up by microorganisms was at least seven times than plants. Although microorganisms efficiently compete for N with plants, the competition is alleviated through chemical partitioning mainly in deeper soil layer. In the upper soil layer, neither chemical nor temporal niche separation is realized leading to strong competition between plants and microorganisms that modifies N dynamics in grasslands. PMID:26961252

  9. Herbivores and nutrients control grassland plant diversity via light limitation.

    SciTech Connect

    Borer, Elizabeth T.; et al, et al

    2014-01-01

    Human alterations to nutrient cycles1,2 and herbivore communities3–7 are affecting global biodiversity dramatically2. Ecological theory predicts these changes should be strongly counteractive: nutrient addition drives plant species loss through intensified competition for light, whereas herbivores prevent competitive exclusion by increasing ground-level light, particularly in productive systems8,9. Here we use experimental data spanning a globally relevant range of conditions to test the hypothesis that herbaceous plant species losses caused by eutrophication may be offset by increased light availability due to herbivory. This experiment, replicated in 40 grasslands on 6 continents, demonstrates that nutrients and herbivores can serve as counteracting forces to control local plant diversity through light limitation, independent of site productivity, soil nitrogen, herbivore type and climate. Nutrient addition consistently reduced local diversity through light limitation, and herbivory rescued diversity at sites where it alleviated light limitation. Thus, species loss from anthropogenic eutrophication can be ameliorated in grasslands where herbivory increases ground-level light.

  10. Nitrogen acquisition by plants and microorganisms in a temperate grassland.

    PubMed

    Liu, Qianyuan; Qiao, Na; Xu, Xingliang; Xin, Xiaoping; Han, Jessie Yc; Tian, Yuqiang; Ouyang, Hua; Kuzyakov, Yakov

    2016-01-01

    Nitrogen (N) limitation is common in most terrestrial ecosystems, often leading to strong competition between microorganisms and plants. The mechanisms of niche differentiation to reduce this competition remain unclear. Short-term (15)N experiments with NH4(+), NO3(-), and glycine were conducted in July, August and September in a temperate grassland to evaluate the chemical, spatial and temporal niche differentiation by competition between plants and microorganisms for N. Microorganisms preferred NH4(+) and NO3(-), while plants preferred NO3(-). Both plants and microorganisms acquired more N in August and September than in July. The soil depth had no significant effects on microbial uptake, but significantly affected plant N uptake. Plants acquired 67% of their N from the 0-5 cm soil layer and 33% from the 5-15 cm layer. The amount of N taken up by microorganisms was at least seven times than plants. Although microorganisms efficiently compete for N with plants, the competition is alleviated through chemical partitioning mainly in deeper soil layer. In the upper soil layer, neither chemical nor temporal niche separation is realized leading to strong competition between plants and microorganisms that modifies N dynamics in grasslands. PMID:26961252

  11. Functional diversity of leaf nitrogen concentrations drives grassland carbon fluxes.

    PubMed

    Milcu, Alexandru; Roscher, Christiane; Gessler, Arthur; Bachmann, Dörte; Gockele, Annette; Guderle, Markus; Landais, Damien; Piel, Clément; Escape, Christophe; Devidal, Sebastien; Ravel, Olivier; Buchmann, Nina; Gleixner, Gerd; Hildebrandt, Anke; Roy, Jacques

    2014-04-01

    Little is known about the role of plant functional diversity for ecosystem-level carbon (C) fluxes. To fill this knowledge gap, we translocated monoliths hosting communities with four and 16 sown species from a long-term grassland biodiversity experiment ('The Jena Experiment') into a controlled environment facility for ecosystem research (Ecotron). This allowed quantifying the effects of plant diversity on ecosystem C fluxes as well as three parameters of C uptake efficiency (water and nitrogen use efficiencies and apparent quantum yield). By combining data on ecosystem C fluxes with vegetation structure and functional trait-based predictors, we found that increasing plant species and functional diversity led to higher gross and net ecosystem C uptake rates. Path analyses and light response curves unravelled the diversity of leaf nitrogen concentration in the canopy as a key functional predictor of C fluxes, either directly or indirectly via LAI and aboveground biomass. PMID:24393400

  12. Overview of the Focused Isoprene eXperiment at the California Institute of Technology (FIXCIT): mechanistic chamber studies on the oxidation of biogenic compounds

    DOE PAGESBeta

    Nguyen, T. B.; Crounse, J. D.; Schwantes, R. H.; Teng, A. P.; Bates, K. H.; Zhang, X.; St. Clair, J. M.; Brune, W. H.; Tyndall, G. S.; Keutsch, F. N.; et al

    2014-12-19

    The Focused Isoprene eXperiment at the California Institute of Technology (FIXCIT) was a collaborative atmospheric chamber campaign that occurred during January 2014. FIXCIT is the laboratory component of a synergistic field and laboratory effort aimed toward (1) better understanding the chemical details behind ambient observations relevant to the southeastern United States, (2) advancing the knowledge of atmospheric oxidation mechanisms of important biogenic hydrocarbons, and (3) characterizing the behavior of field instrumentation using authentic standards. Approximately 20 principal scientists from 14 academic and government institutions performed parallel measurements at a forested site in Alabama and at the atmospheric chambers at Caltech.more » During the 4 week campaign period, a series of chamber experiments was conducted to investigate the dark- and photo-induced oxidation of isoprene, α-pinene, methacrolein, pinonaldehyde, acylperoxy nitrates, isoprene hydroxy nitrates (ISOPN), isoprene hydroxy hydroperoxides (ISOPOOH), and isoprene epoxydiols (IEPOX) in a highly controlled and atmospherically relevant manner. Pinonaldehyde and isomer-specific standards of ISOPN, ISOPOOH, and IEPOX were synthesized and contributed by campaign participants, which enabled explicit exploration into the oxidation mechanisms and instrument responses for these important atmospheric compounds. The present overview describes the goals, experimental design, instrumental techniques, and preliminary observations from the campaign. This work provides context for forthcoming publications affiliated with the FIXCIT campaign. Insights from FIXCIT are anticipated to aid significantly in interpretation of field data and the revision of mechanisms currently implemented in regional and global atmospheric models.« less

  13. Overview of the Focused Isoprene eXperiments at California Institute of Technology (FIXCIT): mechanistic chamber studies on the oxidation of biogenic compounds

    DOE PAGESBeta

    Nguyen, T. B.; Crounse, J. D.; Schwantes, R. H.; Teng, A. P.; Bates, K. H.; Zhang, X.; St. Clair, J. M.; Brune, W. H.; Tyndall, G. S.; Keutsch, F. N.; et al

    2014-08-25

    The Focused Isoprene eXperiment at the California Institute of Technology (FIXCIT) was a collaborative atmospheric chamber campaign that occurred during January 2014. FIXCIT was the laboratory component of a synergistic field and laboratory effort aimed toward (1) better understanding the chemical details behind ambient observations relevant to the Southeastern United States, (2) advancing the knowledge of atmospheric oxidation mechanisms of important biogenic hydrocarbons, and (3) characterizing the behavior of field instrumentation using authentic standards. Approximately 20 principal scientists from 14 academic and government institutions performed parallel measurements at a forested site in Alabama and at the atmospheric chambers at Caltech.more » During the four-week campaign period, a series of chamber experiments was conducted to investigate the dark- and photo-induced oxidation of isoprene, α-pinene, methacrolein, pinonaldehyde, acylperoxy nitrates, isoprene hydroxy nitrates (ISOPN), isoprene hydroxy hydroperoxides (ISOPOOH), and isoprene epoxydiols (IEPOX) in a highly-controlled and atmospherically-relevant manner. Pinonaldehyde and isomer-specific standards of ISOPN, ISOPOOH, and IEPOX were synthesized and contributed by campaign participants, which enabled explicit exploration into the oxidation mechanisms and instrument responses for these important atmospheric compounds. The present overview describes the goals, experimental design, instrumental techniques, and preliminary observations from the campaign. Insights from FIXCIT are anticipated to significantly aid in interpretation of field data and the revision of mechanisms currently implemented in regional and global atmospheric models.« less

  14. Experiences and Perceptions of Medical Discrimination Among a Multiethnic Sample of Breast Cancer Patients in the Greater San Francisco Bay Area, California

    PubMed Central

    Nuru-Jeter, Amani; Morris, Pagan; Allen, Laura; Shema, Sarah J.; Winters, June K.; Gomez, Scarlett Lin

    2012-01-01

    Objectives. We conducted qualitative interviews with breast cancer survivors to identify themes related to institutional, personally mediated, and internalized discrimination in the medical setting. Methods. We conducted 7 focus groups and 23 one-on-one interviews with a multiethnic sample of breast cancer survivors randomly selected from a population-based registry covering the Greater San Francisco Bay Area, California. Results. Participants reported experiencing different forms of medical discrimination related to class, race, and language. Among African Americans, participants reported experiencing internalized discrimination and personal or group discrimination discrepancy—perceiving discrimination against them as a racial/ethnic group, yet not perceiving or discussing personal experiences of discrimination. Among Asian immigrants, participants reported experiencing institutional and personally mediated overt types of discrimination, including lack of access to quality and readily available translation services. Our results also indicated well-established coping mechanisms in response to discrimination experiences in both groups. Conclusions. Participants reported experiencing medical discrimination at all 3 levels, which may have deleterious health effects through the biopsychosocial stress pathway and through active coping mechanisms that could lead to delayed- or underutilization of the health care system to avoid discrimination. PMID:22420791

  15. Climate-driven diversity loss in a grassland community.

    PubMed

    Harrison, Susan P; Gornish, Elise S; Copeland, Stella

    2015-07-14

    Local ecological communities represent the scale at which species coexist and share resources, and at which diversity has been experimentally shown to underlie stability, productivity, invasion resistance, and other desirable community properties. Globally, community diversity shows a mixture of increases and decreases over recent decades, and these changes have relatively seldom been linked to climatic trends. In a heterogeneous California grassland, we documented declining plant diversity from 2000 to 2014 at both the local community (5 m(2)) and landscape (27 km(2)) scales, across multiple functional groups and soil environments. Communities became particularly poorer in native annual forbs, which are present as small seedlings in midwinter; within native annual forbs, community composition changed toward lower representation of species with a trait indicating drought intolerance (high specific leaf area). Time series models linked diversity decline to the significant decrease in midwinter precipitation. Livestock grazing history, fire, succession, N deposition, and increases in exotic species could be ruled out as contributing causes. This finding is among the first demonstrations to our knowledge of climate-driven directional loss of species diversity in ecological communities in a natural (nonexperimental) setting. Such diversity losses, which may also foreshadow larger-scale extinctions, may be especially likely in semiarid regions that are undergoing climatic trends toward higher aridity and lower productivity. PMID:26100891

  16. Climate-driven diversity loss in a grassland community

    PubMed Central

    Harrison, Susan P.; Gornish, Elise S.; Copeland, Stella

    2015-01-01

    Local ecological communities represent the scale at which species coexist and share resources, and at which diversity has been experimentally shown to underlie stability, productivity, invasion resistance, and other desirable community properties. Globally, community diversity shows a mixture of increases and decreases over recent decades, and these changes have relatively seldom been linked to climatic trends. In a heterogeneous California grassland, we documented declining plant diversity from 2000 to 2014 at both the local community (5 m2) and landscape (27 km2) scales, across multiple functional groups and soil environments. Communities became particularly poorer in native annual forbs, which are present as small seedlings in midwinter; within native annual forbs, community composition changed toward lower representation of species with a trait indicating drought intolerance (high specific leaf area). Time series models linked diversity decline to the significant decrease in midwinter precipitation. Livestock grazing history, fire, succession, N deposition, and increases in exotic species could be ruled out as contributing causes. This finding is among the first demonstrations to our knowledge of climate-driven directional loss of species diversity in ecological communities in a natural (nonexperimental) setting. Such diversity losses, which may also foreshadow larger-scale extinctions, may be especially likely in semiarid regions that are undergoing climatic trends toward higher aridity and lower productivity. PMID:26100891

  17. Report for borehole explosion data acquired in the 1999 Los Angeles Region Seismic Experiment (LARSE II), Southern California: Part I, description of the survey

    USGS Publications Warehouse

    Fuis, Gary S.; Murphy, Janice M.; Okaya, David A.; Clayton, Robert W.; Davis, Paul M.; Thygesen, Kristina; Baher, Shirley A.; Ryberg, Trond; Benthien, Mark L.; Simila, Gerry; Perron, J. Taylor; Yong, Alan K.; Reusser, Luke; Lutter, William J.; Kaip, Galen; Fort, Michael D.; Asudeh, Isa; Sell, Russell; Van Schaack, John R.; Criley, Edward E.; Kaderabek, Ronald; Kohler, Will M.; Magnuski, Nickolas H.

    2001-01-01

    The Los Angeles Region Seismic Experiment (LARSE) is a joint project of the U.S. Geological Survey (USGS) and the Southern California Earthquake Center (SCEC). The purpose of this project is to produce seismic images of the subsurface of the Los Angeles region down to the depths at which earthquakes occur, and deeper, in order to remedy a deficit in our knowledge of the deep structure of this region. This deficit in knowledge has persisted despite over a century of oil exploration and nearly 70 years of recording earthquakes in southern California. Understanding the deep crustal structure and tectonics of southern California is important to earthquake hazard assessment. Specific imaging targets of LARSE include (a) faults, especially blind thrust faults, which cannot be reliably detected any other way; and (b) the depths and configurations of sedimentary basins. Imaging of faults is important in both earthquake hazard assessment but also in modeling earthquake occurrence. Earthquake occurrence cannot be understood unless the earthquake-producing "machinery" (tectonics) is known (Fuis and others, 2001). Imaging the depths and configurations of sedimentary basins is important because earthquake shaking at the surface is enhanced by basin depth and by the presence of sharp basin edges (Wald and Graves, 1998, Working Group on California Earthquake Probabilities, 1995; Field and others, 2001). (Sedimentary basins are large former valleys now filled with sediment eroded from nearby mountains.) Sedimentary basins in the Los Angeles region that have been investigated by LARSE include the Los Angeles, San Gabriel Valley, San Fernando Valley, and Santa Clarita Valley basins. The seismic imaging surveys of LARSE include recording of earthquakes (both local and distant earthquakes) along several corridors (or transects) through the Los Angeles region and also recording of man-made sources along these same corridors. Man-made sources have included airguns offshore and borehole

  18. Burning reveals cryptic diversity and promotes coexistence of native species in a restored California prairie

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grassland and prairie restoration projects in California often result in long-term establishment of only a few native plant species, even when they begin with a diverse palette of species. A likely explanation for the disappearance of certain native species over time is that they are outcompeted by ...

  19. Impact of grazing on carbon balance of a Belgian grassland

    NASA Astrophysics Data System (ADS)

    Jérôme, Elisabeth; Beckers, Yves; Bodson, Bernard; Moureaux, Christine; Dumortier, Pierre; Beekkerk van Ruth, Joran; Aubinet, Marc

    2013-04-01

    This work analyzes the impact of grazing on the carbon balance of a grassland grazed by the Belgian Blue breed of cattle. The research was run at the Dorinne terrestrial observatory (DTO). The experimental site is a permanent grassland of ca. 4.2 ha located in the Belgian Condroz (50° 18' 44" N; 4° 58' 07" E; 248 m asl.). Other studies are conducted at the DTO including measurements of methane (CH4) and nitrous oxide fluxes (Dumortier et al., Geophysical Research Abstracts, Vol. 15, EGU2013-2083-1, 2013; Beekkerk van Ruth et al., Geophysical Research Abstracts, Vol. 15, EGU2013-3211, 2013, respectively). Grassland carbon budget (Net Biome Productivity, NBP) was calculated from Net Ecosystem Exchange (NEE) measured by eddy covariance by taking imports and exports of organic C and losses of carbon as CH4 into account. After 2 years of measurements (May 2010 - May 2012), the grassland behaved on average as a CO2 source (NEE = 73 ±31 g C m-2 y-1). After inclusion of all the C inputs and outputs the site was closed to equilibrium (NBP = 23 ±34 g C m-2 y-1). To analyze the impact of grazing on CO2 fluxes, we studied the temporal evolution of gross maximal photosynthetic capacity GPPmax and dark respiration Rd (deduced from the response of daytime fluxes to radiation over 5-day windows). We calculated GPPmax and Rd variation between the end and the beginning of grazing or non-grazing periods (ΔGPPmax and ΔRd, respectively). We observed a significant decrease of GPPmax during grazing periods and measured a ΔGPPmax dependence on the average stocking rate. This allows us to quantify the assimilation reduction due to grass consumption by cattle. On the contrary, no Rd decrease was observed during grazing periods. Moreover, we found that cumulated monthly NEE increased significantly with the average stocking rate. In addition, a confinement experiment was carried out in order to analyze livestock contribution to Total Ecosystem Respiration. Each experiment extended over

  20. Effects of management of ecosystem carbon pools and fluxes in grassland ecosystems

    NASA Astrophysics Data System (ADS)

    Ryals, R.; Silver, W. L.

    2010-12-01

    Grasslands represent a large land-use footprint and have considerable potential to sequester carbon (C) in soil. Climate policies and C markets may provide incentives for land managers to pursue strategies that optimize soil C storage, yet we lack robust understanding of C sequestration in grasslands. Previous research has shown that management approaches such as organic amendments or vertical subsoiling can lead to larger soil C pools. These management approaches can both directly and indirectly affect soil C pools. We used well-replicated field experiments to explore the effects of these management strategies on ecosystem C pools and fluxes in two bioclimatic regions of California (Sierra Foothills Research and Extension Center (SFREC) and Nicasio Ranch). Our treatments included an untreated control, compost amendments, plowed (vertical subsoil), and compost + plow. The experiment was conducted over two years allowing us to compare dry (360 mm) and average (632 mm) rainfall conditions. Carbon dioxide (CO2) fluxes were measured weekly using a LI-8100 infrared gas analyzer. Methane (CH4) and nitrous oxide (N2O) fluxes were measured monthly using static flux chambers. Aboveground and belowground biomass were measured at the end of the growing season as an index of net primary productivity (NPP) in the annual plant dominated system. Soil moisture and temperature were measured continuously and averaged on hourly and daily timescales. Soil organic C and N concentrations were measured prior to the application of management treatments and at the ends of each growing season. Soils were collected to a 10 cm depth in year one and at four depth increments (0-10, 10-30, 30-50, and 50-100 cm) in year two. Soil C and N concentrations were converted to content using bulk density values for each plot. During both growing seasons, soil respiration rates were higher in the composted plots and lower in the plowed plots relative to controls at both sites. The effects on C loss via

  1. Still Learning from the Past: Drawing on California's CLAS Experience to Inform Assessment of the Common Core. Policy and Practice Brief

    ERIC Educational Resources Information Center

    Knudson, Joel; Hannan, Stephanie; O'Day, Jennifer; Castro, Marina

    2015-01-01

    The Common Core State Standards represent an exciting step forward for California, and for the nation as a whole, in supporting instruction that can better prepare students for college and career success. Concurrent with the transition to the new standards, the Smarter Balanced Assessment Consortium (SBAC), of which California is a governing…

  2. A Case Study of a Southern California Elementary School District's Comprehensive School Safety Plan: Experiences and Perceptions of School Leaders and Teachers

    ERIC Educational Resources Information Center

    Favila, Marisela

    2013-01-01

    For children to be successful, schools must provide a safe and secure environment in which teachers can teach and students can learn (Skiba & Sprague, 2008). In California, state regulations require that schools maintain an appropriate school climate on campus, in classrooms, and at school sponsored events (California Education Code 35294).…

  3. Grassland/atmosphere response to changing climate: Coupling regional and local scales. Final report

    SciTech Connect

    Coughenour, M.B.; Kittel, T.G.F.; Pielke, R.A.; Eastman, J.

    1993-10-01

    The objectives of the study were: to evaluate the response of grassland ecosystems to atmospheric change at regional and site scales, and to develop multiscaled modeling systems to relate ecological and atmospheric models with different spatial and temporal resolutions. A menu-driven shell was developed to facilitate use of models at different temporal scales and to facilitate exchange information between models at different temporal scales. A detailed ecosystem model predicted that C{sub 3} temperate grasslands wig respond more strongly to elevated CO{sub 2} than temperate C{sub 4} grasslands in the short-term while a large positive N-PP response was predicted for a C{sub 4} Kenyan grassland. Long-term climate change scenarios produced either decreases or increases in Colorado plant productivity (NPP) depending on rainfall, but uniform increases in N-PP were predicted in Kenya. Elevated CO{sub 2} is likely to have little effect on ecosystem carbon storage in Colorado while it will increase carbon storage in Kenya. A synoptic climate classification processor (SCP) was developed to evaluate results of GCM climate sensitivity experiments. Roughly 80% agreement was achieved with manual classifications. Comparison of lx and 2xCO{sub 2} GCM Simulations revealed relatively small differences.

  4. Multiscale Trend Analysis for Pampa Grasslands Using Ground Data and Vegetation Sensor Imagery

    PubMed Central

    Scottá, Fernando C.; da Fonseca, Eliana L.

    2015-01-01

    This study aimed to evaluate changes in the aboveground net primary productivity (ANPP) of grasslands in the Pampa biome by using experimental plots and changes in the spectral responses of similar vegetation communities obtained by remote sensing and to compare both datasets with meteorological variations to validate the transition scales of the datasets. Two different geographic scales were considered in this study. At the local scale, an analysis of the climate and its direct influences on grassland ANPP was performed using data from a long-term experiment. At the regional scale, the influences of climate on the grassland reflectance patterns were determined using vegetation sensor imagery data. Overall, the monthly variations of vegetation canopy growth analysed using environmental changes (air temperature, total rainfall and total evapotranspiration) were similar. The results from the ANPP data and the NDVI data showed the that variations in grassland growth were similar and independent of the analysis scale, which indicated that local data and the relationships of local data with climate can be considered at the regional scale in the Pampa biome by using remote sensing. PMID:26197320

  5. Multiscale Trend Analysis for Pampa Grasslands Using Ground Data and Vegetation Sensor Imagery.

    PubMed

    Scottá, Fernando C; da Fonseca, Eliana L

    2015-01-01

    This study aimed to evaluate changes in the aboveground net primary productivity (ANPP) of grasslands in the Pampa biome by using experimental plots and changes in the spectral responses of similar vegetation communities obtained by remote sensing and to compare both datasets with meteorological variations to validate the transition scales of the datasets. Two different geographic scales were considered in this study. At the local scale, an analysis of the climate and its direct influences on grassland ANPP was performed using data from a long-term experiment. At the regional scale, the influences of climate on the grassland reflectance patterns were determined using vegetation sensor imagery data. Overall, the monthly variations of vegetation canopy growth analysed using environmental changes (air temperature, total rainfall and total evapotranspiration) were similar. The results from the ANPP data and the NDVI data showed the that variations in grassland growth were similar and independent of the analysis scale, which indicated that local data and the relationships of local data with climate can be considered at the regional scale in the Pampa biome by using remote sensing. PMID:26197320

  6. BVOCs emission in a semi-arid grassland under climate warming and nitrogen deposition

    NASA Astrophysics Data System (ADS)

    Wang, H. J.; Xia, J. Y.; Mu, Y. J.; Nie, L.; Han, X. G.; Wan, S. Q.

    2012-04-01

    Biogenic volatile organic compounds (BVOCs) profoundly affect atmospheric chemistry and ecosystem functioning. BVOCs emission and their responses to global change are still unclear in grasslands, which cover one quarter of the Earth's land surface and are currently undergoing the largest changes. Over two growing seasons, we conducted a field experiment in a semi-arid grassland (Inner Mongolia, China) to examine the emission and the responses of BVOCs emissions to warming and nitrogen deposition. The natural emission rate (NER) of monoterpene (dominant BVOCs here) is 107 ± 16 μg m-2 h-1 in drought 2007, and 266 ± 53 μg m-2 h-1 in wet 2008, respectively. Warming decreased the standard emission factor (SEF) by 24% in 2007, while it increased by 43% in 2008. The exacerbated soil moisture loss caused by warming in dry season might be responsible for the decrease of SEF in 2007. A possible threshold of soil moisture (8.2% (v/v)), which controls the direction of warming effects on monoterpene emission, existed in the semiarid grassland. Nitrogen deposition decreased the coverage of Artemisia frigida and hence reduced the NER by 24% across the two growing seasons. These results suggest that the grasslands dominated by the extended Artemisia frigida are an important source for BVOCs, while the responses of their emissions to global changes are more uncertain since they depend on multifactorial in-situ conditions.

  7. BVOCs emission in a semi-arid grassland under climate warming and nitrogen deposition

    NASA Astrophysics Data System (ADS)

    Wang, H. J.; Xia, J. Y.; Mu, Y. J.; Nie, L.; Han, X. G.; Wan, S. Q.

    2012-01-01

    Biogenic volatile organic compounds (BVOCs) profoundly affect atmospheric chemistry and ecosystem functioning. BVOCs emission and their responses to global change are still unclear in grasslands, which cover one quarter of the Earth's land surface and are currently undergoing the largest changes. Over two growing seasons, we conducted a field experiment in a semi-arid grassland (Inner Mongolia, China) to examine the emission and the responses of BVOCs emissions to warming and nitrogen deposition. The natural emission rate (NER) of monoterpene (dominant BVOCs here) is 107 ± 16 μg m-2 h-1 in drought 2007, and 266 ± 53 μg m-2 h-1 in wet 2008, respectively. Warming decreased the standard emission factor (SEF) by 24% in 2007, while increased it by 43% in 2008. The exacerbated soil moisture loss caused by warming in dry season might be responsible for the decrease of SEF in 2007. A possible threshold of soil moisture (8.2% (v/v)), which controls the direction of warming effects on monoterpene emission, existed in the semiarid grassland. Nitrogen deposition decreased the coverage of Artemisia frigida and hence reduced the NER by 24% across the two growing seasons. These results suggest that the grasslands dominated by the extended Artemisia frigida are an important source for BVOCs, while the responses of their emissions to global changes are more uncertain since they depend on multifactorial/in-situ/conditions.

  8. Response of carbon dioxide emissions to sheep grazing and nitrogen application in an alpine grassland

    NASA Astrophysics Data System (ADS)

    Gong, Y. M.; Mohammat, A.; Liu, X. J.; Li, K. H.; Christie, P.; Fang, F.; Song, W.; Chang, Y. H.; Han, W. X.; Lü, X. T.; Liu, Y. Y.; Hu, Y. K.

    2013-07-01

    Previous work has failed to address fully the response of (autotrophic and heterotrophic) respiration to grazing and nitrogen (N) addition in different ecosystems, particularly in alpine grasslands outside the growing season. From 2010 to 2011, we combined two methods (static closed chambers and a closed dynamic soil CO2 flux system) in a controlled field experiment in an alpine grassland in the Tianshan Mountains. We examined the effects of grazing and N application on ecosystem respiration (Re) both outside (NGS) and during (GS) the growing season and determined the pattern of Re in relation to climate change. There was no significant change in CO2 emissions under grazing or N application. Heterotrophic respiration (Rh) accounted for 78.5% of Re. Re, Rh and autotrophic respiration (Ra) outside the growing season were equivalent to 12.9, 14.1 and 11.4% of the respective CO2 fluxes during the growing season. In addition, our results indicate that precipitation (soil water content) plays a critical role in Ra in this cold and arid environment. Both Rh and Re were sensitive to soil temperature. Moreover, our results suggest that grazing and N addition exert no significant effect on CO2 emissions in alpine grassland but may alter soil carbon stocks in alpine grassland.

  9. Persistence of biological nitrogen fixation in high latitude grass-clover grasslands under different management practices

    NASA Astrophysics Data System (ADS)

    Tzanakakis, Vasileios; Sturite, Ievina; Dörsch, Peter

    2016-04-01

    Biological nitrogen fixation (BNF) can substantially contribute to N supply in permanent grasslands, improving N yield and forage quality, while reducing inorganic N inputs. Among the factors critical to the performance of BNF in grass-legume mixtures are selected grass and legume species, proportion of legumes, the soil-climatic conditions, in particular winter conditions, and management practices (e.g. fertilization and compaction). In high latitude grasslands, low temperatures can reduce the performance of BNF by hampering the legumés growth and by suppressing N2 fixation. Estimation of BNF in field experiments is not straightforward. Different methods have been developed providing different results. In the present study, we evaluated the performance of BNF, in a newly established field experiment in North Norway over four years. The grassland consisted of white clover (Trifolium repens L.) and red clover (Trifolium pretense L.) sawn in three proportions (0, 15 and 30% in total) together with timothy (Pheum pretense L.) and meadow fescue (Festuca pratensis L.). Three levels of compaction were applied each year (no tractor, light tractor, heavy tractor) together with two different N rates (110 kg N/ha as cattle slurry or 170 kg N/ha as cattle slurry and inorganic N fertilizer). We applied two different methods, the 15N natural abundance and the difference method, to estimate BNF in the first harvest of each year. Overall, the difference method overestimated BNF relative to the 15N natural abundance method. BNF in the first harvest was compared to winter survival of red and white clover plants, which decreased with increasing age of the grassland. However, winter conditions did not seem to affect the grassland's ability to fix N in spring. The fraction of N derived from the atmosphere (NdfA) in white and red clover was close to 100% in each spring, indicating no suppression of BNF. BNF increased the total N yield of the grasslands by up to 75%, mainly due to high

  10. The impact of land-cover change on carbon and water cycling in the U.S. central plains grasslands

    NASA Astrophysics Data System (ADS)

    Buck, Tyler

    Using the eddy covariance technique, the impact of land cover variability on carbon and water cycling was examined at three different grasslands in Northeast Kansas. One site 8 km north of Lawrence, Kansas at the Nelson Environmental Study Area (NESA) experiences woody-encroachment and is burned every three years. The remaining two sites are located at the Konza Prairie Biological Station, 8 km south of Manhattan, Kansas. KZU is located in an annual burned, non-grazed watershed in an upland area. K4B experiences woody encroachment and has prescribed burns every four years. Water-use efficiency was used to examine how the carbon and water cycling of these ecosystems respond to land cover change. Analysis suggest that the two grasslands experiencing woody-encroachment (NESA and K4B) show more efficient water use values than the grassland that is not (KZU). This may be due to a possible difference in rooting depth between woody-vegetation and grasses.

  11. Deposition fluxes of terpenes over grassland

    NASA Astrophysics Data System (ADS)

    Bamberger, I.; HöRtnagl, L.; Ruuskanen, T. M.; Schnitzhofer, R.; Müller, M.; Graus, M.; Karl, T.; Wohlfahrt, G.; Hansel, A.

    2011-07-01

    Eddy covariance flux measurements were carried out for two subsequent vegetation periods above a temperate mountain grassland in an alpine valley using a proton-transfer-reaction-mass spectrometer (PTR-MS) and a PTR time-of-flight-mass spectrometer (PTR-TOF). In 2008 and during the first half of the vegetation period 2009 the volume mixing ratios (VMRs) for the sum of monoterpenes (MTs) were typically well below 1 ppbv and neither MT emission nor deposition was observed. After a hailstorm in July 2009 an order of magnitude higher amount of terpenes was transported to the site from nearby coniferous forests causing elevated VMRs. As a consequence, deposition fluxes of terpenes to the grassland, which continued over a time period of several weeks without significant reemission, were observed. For days without precipitation the deposition occurred at velocities close to the aerodynamic limit. In addition to monoterpene uptake, deposition fluxes of the sum of sesquiterpenes (SQTs) and the sum of oxygenated terpenes (OTs) were detected. Considering an entire growing season for the grassland (i.e., 1 April to 1 November 2009), the cumulative carbon deposition of monoterpenes reached 276 mg C m-2. This is comparable to the net carbon emission of methanol (329 mg C m-2), which is the dominant nonmethane volatile organic compound (VOC) emitted from this site, during the same time period. It is suggested that deposition of monoterpenes to terrestrial ecosystems could play a more significant role in the reactive carbon budget than previously assumed.

  12. Experiments with Seasonal Forecasts of ocean conditions for the Northern region of the California Current upwelling system.

    PubMed

    Siedlecki, Samantha A; Kaplan, Isaac C; Hermann, Albert J; Nguyen, Thanh Tam; Bond, Nicholas A; Newton, Jan A; Williams, Gregory D; Peterson, William T; Alin, Simone R; Feely, Richard A

    2016-01-01

    Resource managers at the state, federal, and tribal levels make decisions on a weekly to quarterly basis, and fishers operate on a similar timeframe. To determine the potential of a support tool for these efforts, a seasonal forecast system is experimented with here. JISAO's Seasonal Coastal Ocean Prediction of the Ecosystem (J-SCOPE) features dynamical downscaling of regional ocean conditions in Washington and Oregon waters using a combination of a high-resolution regional model with biogeochemistry and forecasts from NOAA's Climate Forecast System (CFS). Model performance and predictability were examined for sea surface temperature (SST), bottom temperature, bottom oxygen, pH, and aragonite saturation state through model hindcasts, reforecast, and forecast comparisons with observations. Results indicate J-SCOPE forecasts have measurable skill on seasonal timescales. Experiments suggest that seasonal forecasting of ocean conditions important for fisheries is possible with the right combination of components. Those components include regional predictability on seasonal timescales of the physical environment from a large-scale model, a high-resolution regional model with biogeochemistry that simulates seasonal conditions in hindcasts, a relationship with local stakeholders, and a real-time observational network. Multiple efforts and approaches in different regions would advance knowledge to provide additional tools to fishers and other stakeholders. PMID:27273473

  13. Experiments with Seasonal Forecasts of ocean conditions for the Northern region of the California Current upwelling system

    NASA Astrophysics Data System (ADS)

    Siedlecki, Samantha A.; Kaplan, Isaac C.; Hermann, Albert J.; Nguyen, Thanh Tam; Bond, Nicholas A.; Newton, Jan A.; Williams, Gregory D.; Peterson, William T.; Alin, Simone R.; Feely, Richard A.

    2016-06-01

    Resource managers at the state, federal, and tribal levels make decisions on a weekly to quarterly basis, and fishers operate on a similar timeframe. To determine the potential of a support tool for these efforts, a seasonal forecast system is experimented with here. JISAO’s Seasonal Coastal Ocean Prediction of the Ecosystem (J-SCOPE) features dynamical downscaling of regional ocean conditions in Washington and Oregon waters using a combination of a high-resolution regional model with biogeochemistry and forecasts from NOAA’s Climate Forecast System (CFS). Model performance and predictability were examined for sea surface temperature (SST), bottom temperature, bottom oxygen, pH, and aragonite saturation state through model hindcasts, reforecast, and forecast comparisons with observations. Results indicate J-SCOPE forecasts have measurable skill on seasonal timescales. Experiments suggest that seasonal forecasting of ocean conditions important for fisheries is possible with the right combination of components. Those components include regional predictability on seasonal timescales of the physical environment from a large-scale model, a high-resolution regional model with biogeochemistry that simulates seasonal conditions in hindcasts, a relationship with local stakeholders, and a real-time observational network. Multiple efforts and approaches in different regions would advance knowledge to provide additional tools to fishers and other stakeholders.

  14. Experiments with Seasonal Forecasts of ocean conditions for the Northern region of the California Current upwelling system

    PubMed Central

    Siedlecki, Samantha A.; Kaplan, Isaac C.; Hermann, Albert J.; Nguyen, Thanh Tam; Bond, Nicholas A.; Newton, Jan A.; Williams, Gregory D.; Peterson, William T.; Alin, Simone R.; Feely, Richard A.

    2016-01-01

    Resource managers at the state, federal, and tribal levels make decisions on a weekly to quarterly basis, and fishers operate on a similar timeframe. To determine the potential of a support tool for these efforts, a seasonal forecast system is experimented with here. JISAO’s Seasonal Coastal Ocean Prediction of the Ecosystem (J-SCOPE) features dynamical downscaling of regional ocean conditions in Washington and Oregon waters using a combination of a high-resolution regional model with biogeochemistry and forecasts from NOAA’s Climate Forecast System (CFS). Model performance and predictability were examined for sea surface temperature (SST), bottom temperature, bottom oxygen, pH, and aragonite saturation state through model hindcasts, reforecast, and forecast comparisons with observations. Results indicate J-SCOPE forecasts have measurable skill on seasonal timescales. Experiments suggest that seasonal forecasting of ocean conditions important for fisheries is possible with the right combination of components. Those components include regional predictability on seasonal timescales of the physical environment from a large-scale model, a high-resolution regional model with biogeochemistry that simulates seasonal conditions in hindcasts, a relationship with local stakeholders, and a real-time observational network. Multiple efforts and approaches in different regions would advance knowledge to provide additional tools to fishers and other stakeholders. PMID:27273473

  15. Fire management in fens and wet grasslands grazed by cattle

    USGS Publications Warehouse

    Middleton, Beth A.

    2006-01-01

    Managers grapple with the problem of shrub invasion in fens and wet grasslands, and the invasion of shrubs is a particular problem in newly acquired natural areas that were once grazed by cattle. The specific management for any particular fen or wet grassland depends greatly on its previous land-use history. Managers should have a clear understanding of the grazing and drainage history of newly acquired fens and wet grasslands so that well-informed management decisions can be made.

  16. Dimers and organosulfates derived from biogenic oxidation products in aerosols during the Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX) in California 2007 and 2009 (Invited)

    NASA Astrophysics Data System (ADS)

    Glasius, M.; Worton, D. R.; Kristensen, K.; Nguyen, Q.; Surratt, J.; Enggrob, K. L.; Bouvier-Brown, N. C.; Farmer, D.; Docherty, K. S.; Platt, S.; Bilde, M.; Nøjgaard, J. K.; Seinfeld, J.; Jimenez, J. L.; Goldstein, A.

    2010-12-01

    Oxidation products of biogenic volatile organic compounds, such as monoterpenes and isoprene, contribute to biogenic secondary organic aerosol (BSOA). The organosulfate derivatives of these compounds are formed through heterogeneous reactions involving sulphur compounds, with a considerable contribution from anthropogenic sources. Organosulfate derivatives of biogenic oxidation products thus belong to a new group of anthropogenic enhanced biogenic SOA (ABSOA). The Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX) during summers of 2007 and 2009 provided an excellent platform at Blodgett Forest, California (a ponderosa pine plantation) for studying ABSOA. Typically, polluted air masses were transported upslope from the California Central Valley during day, while night conditions were influenced by downslope transport of air masses, low local atmospheric mixing and formation of a shallow boundary layer. We collected particle samples (PM2.5) as one nighttime and two daytime samples per day. After extraction of filters in polar organic solvents (i.e. acetonitrile or methanol), organic aerosol constituents were analyzed by HPLC coupled through an electrospray inlet to a quadrupole time-of-flight mass spectrometer (qTOF-MS). Organosulfates and nitrooxy organosulfates derived from oxidation products of α-pinene, β-pinene, limonene and isoprene were identified based on their molecular mass and MS fragmentation patterns. Measurements by High Resolution Time of Flight Aerosol Mass Spectrometry (HR-ToF-AMS) show high mass loadings of nitrate in the night and morning samples with highest levels of the nitrooxy organosulfates with MW 295 and MW 297. This may indicate that elevated levels of nitrate and nitrooxy organosulfates are formed in the same polluted air mass, probably through nitrate radical reactions. Terpenylic acid, diterpenylic acid acetate, and methylbutane tricarboxylic acid were found at concentrations comparable to pinic acid. A dimer of

  17. Effects of leafy spurge infestation on grassland birds

    USGS Publications Warehouse

    Scheiman, D.M.; Bollinger, E.K.; Johnson, D.H.

    2003-01-01

    Grassland bird populations are declining. Invasive plant species may be contributing to these declines by altering habitat quality. However, the effects of invasive plants on grassland birds are largely unknown. Leafy spurge (Euphorbia esula) is an exotic, invasive weed in the northern Great Plains. We examined the effects of leafy spurge infestation on densities of breeding birds, nest-site selection, and nest success in grasslands on the Sheyenne National Grassland (SNG), North Dakota, USA, 1999-2000. We categorized spurge-infested grasslands into 3 groups (low, medium, high), based on the area covered by spurge patches. We surveyed 75 100-m-radius circular points (25 in each group), and searched for nests in 6 16-ha plots (2 in each group). Grasshopper sparrow (Ammodramus savannarum) and savannah sparrow (Passerculus sandwichensis) densities were lower on high-spurge points than on low- and medium-spurge points. Bobolink (Dolichonyx oryzivorus) and western meadowlark (Sturnella neglecta) densities were not significantly different among spurge cover groups. Spurge cover did not appear to be an important factor in nest-site selection. However, western meadowlark nest success was positively associated with spurge cover. Vegetation structure is an important indicator of habitat quality and resource availability for grassland birds. Changes in vegetation structure caused by introduced plant species, such as spurge, can alter resource availability and hence affect bird community composition. Managers of spurge-infested grasslands should continue current spurge control measures to help prevent further declines in grassland habitat quality and grassland bird populations.

  18. Greenhouse gas budgets of managed European grasslands

    NASA Astrophysics Data System (ADS)

    Ammann, C.; Horváth, L.; Jones, S. K.

    2012-04-01

    Greenhouse gas exchange of grasslands are directly and indirectly related to the respective carbon (C) and nitrogen (N) budget. Within the framework of the NitroEurope project we investigated the greenhouse gas, carbon, and nitrogen budgets of four European grassland systems over several years: Easter Bush (UK), Oensingen intensive and extensive (CH), and Bugac (HU). They span contrasting climatic conditions, management types (grazing, cutting) and intensity. While Easter Bush (pasture) and Oensingen int. (meadow) were intensively managed and received a considerable amount of fertiliser, the unfertilised sites Bugac (pasture) and Oensingen ext. (meadow) depended on atmospheric N input (wet and dry deposition) and biological N fixation. The experimental results of the four sites were also compared to published GHG fluxes of other European grasslands. While the ecosystem CO2 exchange was measured on the field scale with the eddy covariance method, the soil fluxes of the other greenhouse gases CH4 and N2O have been detected generally by means of static chambers (only occasional application of eddy covariance). The emission of CH4 by grazing ruminant resulting from enteric fermentation was estimated by animal type specific emission factors. For characterizing the total GHG effect of the grassland sites, the contributions of the different GHGs were normalised to CO2-equivalents. Except for Oensingen ext., all sites showed positive C budgets (sequestration). The observed positive correlation between C and N sequestration (with a ratio between 10 and 20) agrees with studies reported in the literature. The magnitude of N2O emission depended mainly on management intensity (fertiliser input) and on the soil moisture conditions. Whereas for the Oensingen and the Bugac sites, the total GHG budget was dominated by the carbon budget, for Easter Bush the combined effect of N2O and CH4 emission (including animal enteric fermentation) was in the same order of magnitude as the

  19. The greenhouse gas balance of European grasslands.

    PubMed

    Chang, Jinfeng; Ciais, Philippe; Viovy, Nicolas; Vuichard, Nicolas; Sultan, Benjamin; Soussana, Jean-François

    2015-10-01

    The greenhouse gas (GHG) balance of European grasslands (EU-28 plus Norway and Switzerland), including CO2 , CH4 and N2 O, is estimated using the new process-based biogeochemical model ORCHIDEE-GM over the period 1961-2010. The model includes the following: (1) a mechanistic representation of the spatial distribution of management practice; (2) management intensity, going from intensively to extensively managed; (3) gridded simulation of the carbon balance at ecosystem and farm scale; and (4) gridded simulation of N2 O and CH4 emissions by fertilized grassland soils and livestock. The external drivers of the model are changing animal numbers, nitrogen fertilization and deposition, land-use change, and variable CO2 and climate. The carbon balance of European grassland (NBP) is estimated to be a net sink of 15 ± 7 g C m(-2 ) year(-1) during 1961-2010, equivalent to a 50-year continental cumulative soil carbon sequestration of 1.0 ± 0.4 Pg C. At the farm scale, which includes both ecosystem CO2 fluxes and CO2 emissions from the digestion of harvested forage, the net C balance is roughly halved, down to a small sink, or nearly neutral flux of 8 g C m(-2 ) year(-1) . Adding CH4 and N2 O emissions to net ecosystem exchange to define the ecosystem-scale GHG balance, we found that grasslands remain a net GHG sink of 19 ± 10 g C-CO2 equiv. m(-2 ) year(-1) , because the CO2 sink offsets N2 O and grazing animal CH4 emissions. However, when considering the farm scale, the GHG balance (NGB) becomes a net GHG source of -50 g C-CO2 equiv. m(-2 ) year(-1) . ORCHIDEE-GM simulated an increase in European grassland NBP during the last five decades. This enhanced NBP reflects the combination of a positive trend of net primary production due to CO2 , climate and nitrogen fertilization and the diminishing requirement for grass forage due to the Europe-wide reduction in livestock numbers. PMID:26059550

  20. The California-Arizona Minority Partnership for Astronomy Research and Education (CAMPARE): an Educational Experience for Undergraduates at the University of Arizona Alumni Association's Astronomy Camp.

    NASA Astrophysics Data System (ADS)

    Lemon, Courtney; McCarthy, D.; Rudolph, A.

    2011-01-01

    The California-Arizona Minority Partnership for Astronomy Research and Education (CAMPARE) is an NSF-funded partnership between the Astronomy Program at Cal Poly Pomona (CPP) and the University of Arizona Steward Observatory designed to promote participation of underrepresented minorities (including women) in astronomy research and education. As part of the education component of the program, CPP undergraduate physics majors and minors are eligible to work as a counselor at the University of Arizona's Astronomy Camp, one of the premier astronomy outreach opportunities in the world. CAMPARE students have the opportunity to work in this learn-by-doing environment with a wide range of students to gain first hand experience of teaching astronomy to students of a wide variety of ages in highly structured educational setting. Cal Poly Pomona students who are interested in education, both formal and informal, work in a variety of camps, from Girl Scout camps to camps for advanced high school students, to further their understanding of what it means to be a professional in the field of education. The CAMPARE student who participated in this program during summer 2010 had the opportunity to work under Dr. Don McCarthy, camp director of University of Arizona's Astronomy Camps for 20 years, and observe the interpersonal relations between campers and staff that is so vital to the learning the students receive. Through these observations, the CAMPARE student was able to learn to gauge students' interest in the material, and experience real life teaching and learning scenarios in the informal education realm.

  1. California Coast

    Atmospheric Science Data Center

    2014-05-15

    ... of the cloud bank is San Nicolas Island, and further up the coast are the Channel Islands. The Los Angeles basin is just south of center; ... Mar 14, 2000 Images:  California Coast location:  United States region:  ...

  2. California Fires

    Atmospheric Science Data Center

    2014-05-15

    article title:  Wildfires Rage in Southern California     ... Image Large plumes of smoke rising from devastating wildfires burning near Los Angeles and San Diego on Sunday, October 26, 2003, ... at JPL October 26, 2003 - Smoke from wildfires near Los Angeles and San Diego. project:  MISR ...

  3. California Dreaming

    ERIC Educational Resources Information Center

    Olson, Cathy Applefeld

    2011-01-01

    After getting her master's degree from UCLA, Nancy Wills dreamed of starting a school-based guitar program so she could teach students to make music on the instrument she'd loved since she was a kid growing up outside of Yosemite, California. She had a strong belief that guitar was perfect for schools, ideal for individualized playing but also…

  4. More than a century of Grain for Green Program is expected to restore soil carbon stock on alpine grassland revealed by field (13)C pulse labeling.

    PubMed

    Li, Qi; Chen, Dongdong; Zhao, Liang; Yang, Xue; Xu, Shixiao; Zhao, Xinquan

    2016-04-15

    Anthropogenic changes in land use/cover have altered the vegetation, soil, and carbon (C) cycling on the Qinghai-Tibetan Plateau (QTP) over the last ~50years. As a result, the Grain for Green Program (GfGP) has been widely implemented over the last 10years to mitigate the impacts of cultivation. To quantify the effects of the GfGP on C partitioning and turnover rates at the ecosystem scale, an in situ (13)C pulse labeling experiment was conducted on natural and GfGP grasslands in an agro-pastoral ecotone in the Lake Qinghai region on the QTP. We found that there were significant differences in the C stocks of all the considered pools in both the natural and GfGP grasslands, with higher CO2 uptake rates in the GfGP grassland than that in the natural grassland. Partitioning of photoassimilate (% of recovered (13)C) in C pools of both grasslands was similar 25days after labeling, except in the roots of the 0-15 and 5-15cm soil layer. Soil organic C (SOC) sequestration rate in the GfGP grassland was 11.59±1.89gCm(-2)yr(-1) significantly greater than that in the natural grassland. The results confirmed that the GfGP is an efficient approach for grassland restoration and C sequestration. However, it will take more than a century (119.19±20.26yr) to restore the SOC stock from the current cropland baseline level to the approximate level of natural grassland. We suggest that additional measures are needed in the selection of suitable plant species for vegetation restoration, and in reasonable grazing management. PMID:26803680

  5. Effects of Water and Nitrogen Addition on Species Turnover in Temperate Grasslands in Northern China

    PubMed Central

    Xu, Zhuwen; Wan, Shiqiang; Ren, Haiyan; Han, Xingguo; Li, Mai-He; Cheng, Weixin; Jiang, Yong

    2012-01-01

    Global nitrogen (N) deposition and climate change have been identified as two of the most important causes of current plant diversity loss. However, temporal patterns of species turnover underlying diversity changes in response to changing precipitation regimes and atmospheric N deposition have received inadequate attention. We carried out a manipulation experiment in a steppe and an old-field in North China from 2005 to 2009, to test the hypothesis that water addition enhances plant species richness through increase in the rate of species gain and decrease in the rate of species loss, while N addition has opposite effects on species changes. Our results showed that water addition increased the rate of species gain in both the steppe and the old field but decreased the rates of species loss and turnover in the old field. In contrast, N addition increased the rates of species loss and turnover in the steppe but decreased the rate of species gain in the old field. The rate of species change was greater in the old field than in the steppe. Water interacted with N to affect species richness and species turnover, indicating that the impacts of N on semi-arid grasslands were largely mediated by water availability. The temporal stability of communities was negatively correlated with rates of species loss and turnover, suggesting that water addition might enhance, but N addition would reduce the compositional stability of grasslands. Experimental results support our initial hypothesis and demonstrate that water and N availabilities differed in the effects on rate of species change in the temperate grasslands, and these effects also depend on grassland types and/or land-use history. Species gain and loss together contribute to the dynamic change of species richness in semi-arid grasslands under future climate change. PMID:22768119

  6. Contrasting above- and belowground sensitivity of three Great Plains grasslands to altered rainfall regimes.

    PubMed

    Wilcox, Kevin R; von Fischer, Joseph C; Muscha, Jennifer M; Petersen, Mark K; Knapp, Alan K

    2015-01-01

    Intensification of the global hydrological cycle with atmospheric warming is expected to increase interannual variation in precipitation amount and the frequency of extreme precipitation events. Although studies in grasslands have shown sensitivity of aboveground net primary productivity (ANPP) to both precipitation amount and event size, we lack equivalent knowledge for responses of belowground net primary productivity (BNPP) and NPP. We conducted a 2-year experiment in three US Great Plains grasslands--the C4-dominated shortgrass prairie (SGP; low ANPP) and tallgrass prairie (TGP; high ANPP), and the C3-dominated northern mixed grass prairie (NMP; intermediate ANPP)--to test three predictions: (i) both ANPP and BNPP responses to increased precipitation amount would vary inversely with mean annual precipitation (MAP) and site productivity; (ii) increased numbers of extreme rainfall events during high-rainfall years would affect high and low MAP sites differently; and (iii) responses belowground would mirror those aboveground. We increased growing season precipitation by as much as 50% by augmenting natural rainfall via (i) many (11-13) small or (ii) fewer (3-5) large watering events, with the latter coinciding with naturally occurring large storms. Both ANPP and BNPP increased with water addition in the two C4 grasslands, with greater ANPP sensitivity in TGP, but greater BNPP and NPP sensitivity in SGP. ANPP and BNPP did not respond to any rainfall manipulations in the C3 -dominated NMP. Consistent with previous studies, fewer larger (extreme) rainfall events increased ANPP relative to many small events in SGP, but event size had no effect in TGP. Neither system responded consistently above- and belowground to event size; consequently, total NPP was insensitive to event size. The diversity of responses observed in these three grassland types underscores the challenge of predicting responses relevant to C cycling to forecast changes in precipitation regimes even

  7. Image-guided robotic stereotactic body radiotherapy for benign spinal tumors: theUniversity of California San Francisco preliminary experience.

    PubMed

    Sahgal, A; Chou, D; Ames, C; Ma, L; Lamborn, K; Huang, K; Chuang, C; Aiken, A; Petti, P; Weinstein, P; Larson, D

    2007-12-01

    We evaluate our preliminary experience using the Cyberknife Radiosurgery System in treating benign spinal tumors. A retrospective review of 16 consecutively treated patients, comprising 19 benign spinal tumors, was performed. Histologic types included neurofibroma [11], chordoma [4], hemangioma [2], and meningioma [2]. Three patients had Neurofibromatosis Type 1 (NF1). Only one tumor, recurrent chordoma, had been previously irradiated, and as such not considered in the local failure analysis. Local failure, for the remaining 18 tumors, was based clinically on symptom progression and/or tumor enlargement based on imaging. Indications for spine stereotactic body radiotherapy (SBRT) consisted of either adjuvant to subtotal resection (5/19), primary treatment alone (12/19), boost following external beam radiotherapy (1/19), and salvage following previous radiation (1/19). Median tumor follow-up is 25 months (2-37), and one patient (with NF1) died at 12 months from a stroke. The median total dose, number of fractions, and prescription isodose was 21 Gy (10-30 Gy), 3 fx (1-5 fx), 80% (42-87%). The median tumor volume was 7.6 cc (0.2-274.1 cc). The median V100 (volume V receiving 100% of the prescribed dose) and maximum tumor dose was 95% (77-100%) and 26.7 Gy (15.4-59.7 Gy), respectively. Three tumors progressed at 2, 4, and 36 months post-SR (n=18). Two tumors were neurofibromas (both in NF1 patients), and the third was an intramedullary hemangioblastoma. Based on imaging, two tumors had MRI documented progression, three had regressed, and 13 were unchanged (n=18). With short follow-up, local control following Cyberknife spine SBRT for benign spinal tumors appear acceptable. PMID:17994789

  8. Lower crustal deformation beneath the central Transverse Ranges, southern California: Results from the Los Angeles Region Seismic Experiment

    USGS Publications Warehouse

    Godfrey, N.J.; Fuis, G.S.; Langenheim, V.; Okaya, D.A.

    2002-01-01

    We present a P wave velocity model derived from active source seismic data collected during the 1994 Los Angeles Region Seismic Experiment. Our model extends previously published upper crustal velocity models to mantle depths. Our model was developed by both ray tracing through a layered model and calculating travel times through a gridded model. It includes an 8-km-thick crustal root centered beneath the surface trace of the San Andreas fault, north of the highest topography in the San Gabriel Mountains. A simple mass balance calculation suggests that ???36 km of north-south shortening across the San Andreas fault in the central Transverse Ranges could have formed this root. If north-south compression began when the "Big Bend" in the San Andreas fault formed at ???5 Ma, 36 km of shortening implies a north-south contraction rate of ???7.1 mm/yr across the central Transverse Ranges. If, instead, north-south compression began when the Transverse Ranges formed at 3.4-3.9 Ma, 36 km of shortening implies a contraction rate of 9.2-10.6 mm/yr. North of the San Andreas fault, the Mojave Desert crust has a low-velocity (6.3 km/s) mid and lower crust and a 28-km-deep Moho. South of the San Andreas fault, beneath the Los Angeles and San Gabriel Valley basins, there is a fast (6.6-6.8 km/s), thick (10-12 km) lower crust with a 27-km-deep Moho. Farther south still, the lower crust of the Continental Borderland is fast (6.6-6.8 km/s) and thin (5 km) with a shallow (22 km deep) Moho.

  9. Grassland Degradation Alters Soil Carbon Turnover through Depth

    NASA Astrophysics Data System (ADS)

    Creamer, C.; Prober, S. M.; Chappell, A.; Farrell, M.; Baldock, J.

    2015-12-01

    Ecosystem degradation is widespread and changes in aboveground plant communities alter belowground soil processes. In Australia, grassy eucalyptus woodlands dominated by kangaroo grasses (Themeda trianda) were widely cleared during European settlement for agriculture, with only fragments remaining of this now threatened ecosystem. As remnant grassland fragments are used for livestock grazing, Themeda transitions through states of degradation, starting with red grasses (Bothriochloa spp) and then proceeding to less productive, increasingly degraded states dominated by either annual exotic weeds or native wallaby grasses (Rytidosperma spp) and spear grasses (Austrastipa spp). The aim of our experiment was to determine how soil organic matter dynamics (including erosion, root biomass, C storage and turnover) have been altered by the transition from deeply-rooted Themeda grass systems to more shallowly-rooted annual exotic weeds and wallaby/spear grass states. We sampled soils in five depth-based increments (0-5, 5-15, 15-30, 30-60, 60-100 cm) across this ecosystem transition at five sites across New South Wales, Australia. Caseium-137 analysis indicated erosion rates were similar among all ecosystems and were consistent with levels for grasslands in the region. Compared to the remnant Themeda grass systems, the degraded states had lower root biomass, lower carbon stocks and C:N ratios in the coarse fraction (> 50 μm), lower fungal : bacterial ratios, higher available phosphate, higher alkyl : O-alkyl C ratios, and faster mineralization of synthetic root-exudate carbon. All these metrics indicate the surprising finding of more microbially processed OM and faster turnover of newly added C in the degraded sites. Compared to one another, the two degraded sites differed in both C and N turnover, with the exotic weeds having higher dissolved organic N, inorganic N, and coarse fraction N, higher fine fraction C stocks, and greater microbial biomass. These differences likely

  10. Measurement of N{sub 2}O fluxes from fertilized grassland using a fast response tunable diode laser spectrometer

    SciTech Connect

    Wienhold, F.G.; Frahm, H.; Harris, G.W.

    1994-08-20

    Measurements of nitrous oxide flux from fertilized agricultural grasslands is important in explaining and predicting the relationship of emissions of this gas to global warming. The nitrous oxide flux from agricultural grasslands was measured using micrometeorological techniques at a site near Stirling, Scotland. Emission levels were measured using a fast response tunable diode laser spectrometer. Measurements were made by both eddy correlation and concentration gradient techniques. This paper describes the results of this experiment and discusses information obtained that may be used for the characterization of the spatial variability in nitrous oxide emissions. 20 refs., 8 figs, 1 tab.

  11. Using Elemental Budgets to Determine Effects of Simulated Climate Change on Phosphorus Cycling in a Grassland Ecosystem

    NASA Astrophysics Data System (ADS)

    Yoo, S.; Paytan, A.; Mellett, T.

    2013-12-01

    The purpose of the Jasper Ridge Global Change Experiment is to find out the effects of climate change on a terrestrial grassland ecosystem. The different treatments include increased carbon dioxide, nitrogen deposition, temperature, and precipitation. A portion of the above ground biomass of each plot was harvested, and an abundant species chosen to analyze. The goal of this project was to investigate the effects of climate change on phosphorus cycling in the grassland vegetation. Total phosphorus content of each sample was determined by combustion and acid digestion along with optical emission spectrometry. Total nitrogen and carbon was determined via flash combustion in an isotope ratio mass spectrometer. This information was combined to evaluate the limitation of phosphorus in each treatment and better understand how climate change may affect phosphorus cycling in terrestrial grasslands.

  12. Recent landscape change in California's Central Valley

    NASA Astrophysics Data System (ADS)

    Soulard, C. E.; Wilson, T. S.

    2012-12-01

    Long term monitoring of land use and land cover in California's intensively farmed Central Valley reveals several key physical and socioeconomic factors driving landscape change. As part of the USGS Land Cover Trends Project, we analyzed modern land-use/land-cover change for the California Central Valley ecoregion between 2000 and 2010, monitoring annual change between 2005 and 2010, while creating two new change intervals (2000-2005 and 2005-2010) to update the existing 27-year, interval-based analysis. Between 2000 and 2010, agricultural lands fluctuated due to changes in water allocations and emerging drought conditions, or were lost permanently to development (240 square km). Land-use pressure from agriculture and development also led to a decline in grasslands and shrublands across the region (280 square km). Overall, 400 square km of new developed lands were added in the first decade of the 21st century. From 2007 to 2010, development only expanded by 50 square km, coinciding with defaults in the banking system, the onset of historic foreclosure crisis in California and the global economic downturn. Our annual LULC change estimates capture landscape-level change in response to regional policy changes, climate, and fluctuations (e.g., growth or decline) in the national and global economy. The resulting change data provide insights into the drivers of landscape change in the California Central Valley and the combination of two consistent mapping efforts represents the first continuous, 37-year endeavor of its kind.

  13. Data on the solute concentration within the subsurface flows of Little Lost Man Creek in response to a transport experiment, Redwood National Park, northwest California

    USGS Publications Warehouse

    Zellweger, Gary W.; Kennedy, V.C.; Bencala, K.E.; Avanzino, R.J.; Jackman, A.P.; Triska, F.J.

    1986-01-01

    A solute transport experiment was conducted on a 327-m reach of Little Lost Man Creek, a small stream in Humboldt County, California. Solutes were injected for 20 days. Chloride was used as a conservative tracer; lithium, potassium, and strontium were used as reactive tracers. In addition, nitrate and phosphate were added as biological reactants. Eighteen shallow wells were dug along the length of the study reach, 1-10 m laterally from the edge of the stream. The wells and sites in the stream were monitored for the injected solutes during and after the injection. Solute concentrations in the wells and stream are indicative of transport properties of stream and subsurface channel flow. This report presents the results of the analyses of the well samples and chemical data relevant to the interpretation of hydrological and chemical interaction between the stream and adjacent channel subsurface flows in the streambed. Calculations of the percentage of streamwater in the wellwater were made from conservative tracer measurements. The composition of wellwater ranged from 47% to 100% streamwater with most values above 90%. The time for water to travel from the beginning of the study reach to the wells was approximately three times as great as the travel time in the stream at the same distance down the reach. The three conclusions that can be drawn are (1) water in the stream exchanges extensively with water in the rest of the channel; (2) the interstitial water in the channel gravels achieves almost the same composition as the stream; and (3) under low flow conditions the stream gravels contain a significant portion of the stream volume. Plots of normalized chloride, lithium, and strontium concentrations at three stream sites are included. (Author 's abstract)

  14. Plant productivity responses to rising atmospheric CO2 and warming in semi-arid grassland in Wyoming, USA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There is little information on the responses of native grasslands to combined global change factors. This experiment examines how plant productivity in a northern mixed-grass prairie near Cheyenne, WY, USA responds to combined CO2 enrichment and warming. The Prairie Heating and CO2 Enrichment (PHACE...

  15. Canopy reflectance modeling in a tropical wooded grassland

    NASA Technical Reports Server (NTRS)

    Simonett, D.

    1986-01-01

    A study area was selected in West Africa in order to establish a relationship between rainfall and grassland productivity, and also to provide ground measurements and support for the GIMMS investigation of the use of AVHRR vegetation index data for monitoring grassland biomass and productivity. Field data collection, image and collateral data acquisition, model development, and data analysis and processing are briefly discussed.

  16. Ecosystem services to and from North American arid grasslands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Arid grasslands throughout North America are characterized by low and variable precipitation, nutrient-poor soils, and high spatial and temporal variability in plant production. These grasslands have provided a variety of goods and services, with the provisioning of food and fiber dominating through...

  17. AmeriFlux US-SRG Santa Rita Grassland

    SciTech Connect

    Scott, Russell

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-SRG Santa Rita Grassland. Site Description - Semidesert C4 grassland, lies in Pasture 1 on the Santa Rita Experimental Range. This is the companion site for US-SRM, but has much less mesquite encroachment.

  18. Carbon Cycling in Grasslands: Effects of Climate Change

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Large amounts of carbon are stored in grassland soils, which can potentially buffer or exacerbate climate change depending on interacting climate factors. Here we discuss results from several grassland field studies examining the effects of atmospheric CO2 enrichment and/or temperature rise on carbo...

  19. Managing Grasslands with Fire: Potential Benefits to Livestock Producers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fire occurred naturally in grasslands and is the oldest method used by humans to manipulate grasslands. Today, fires are typically identified as wildfires or prescribed fires. Wildfires are unplanned and occur as a result of lightning or human negligence and can have an undesirable effect on plant c...

  20. Greenhouse gas emissions from a managed grassland

    NASA Astrophysics Data System (ADS)

    Jones, S. K.; Rees, R. M.; Skiba, U. M.; Ball, B. C.

    2005-07-01

    Managed grasslands contribute to global warming by the exchange of the greenhouse gases carbon dioxide, nitrous oxide and methane. To reduce uncertainties of the global warming potential of European grasslands and to assess potential mitigation options, an integrated approach quantifying fluxes from all three gases is needed. Greenhouse gas emissions from a grassland site in the SE of Scotland were measured in 2002 and 2003. Closed static chambers were used for N 2O and CH 4 flux measurements, and samples were analysed by gas chromatography. Closed dynamic chambers were used for soil respiration measurements, using infrared gas analysis. Three organic manures and two inorganic fertilizers were applied at a rate of 300 kg N ha -1 a -1 (available N) and compared with a zero-N control on grassland plots in a replicated experimental design. Soil respiration from plots receiving manure was up to 1.6 times larger than CO 2 release from control plots and up to 1.7 times larger compared to inorganic treatments ( p<0.05). A highly significant ( p<0.001) effect of fertilizer and manure treatments on N 2O release was observed. Release of N 2O from plots receiving inorganic fertilizers resulted in short term peaks of up to 388 g N 2O-N ha -1 day -1. However losses from plots receiving organic manures were both longer lasting and greater in magnitude, with an emission of up to 3488 g N 2O-N ha -1 day -1 from the sewage sludge treatments. During the 2002 growing season the cumulative total N 2O flux from manure treatments was 25 times larger than that from mineral fertilizers. CH 4 emissions were only significantly increased ( p<0.001) for a short period following applications of cattle slurry. Although soil respiration in manure plots was high, model predictions and micrometeorological flux measurements at an adjacent site suggest that all plots receiving fertilizer or manure acted as a sink for CO 2. Therefore in terms of global warming potentials the contribution of N 2O from

  1. To what extent does urbanisation affect fragmented grassland functioning?

    PubMed

    van der Walt, L; Cilliers, S S; Kellner, K; Du Toit, M J; Tongway, D

    2015-03-15

    Urbanisation creates altered environments characterised by increased human habitation, impermeable surfaces, artificial structures, landscape fragmentation, habitat loss, resulting in different resource loss pathways. The vulnerable Rand Highveld Grassland vegetation unit in the Tlokwe Municipal area, South Africa, has been extensively affected and transformed by urbanisation, agriculture, and mining. Grassland fragments in urban areas are often considered to be less species rich and less functional than in the more untransformed or "natural" exurban environments, and are therefore seldom a priority for conservation. Furthermore, urban grassland fragments are often being more intensely managed than exurban areas, such as consistent mowing in open urban areas. Four urbanisation measures acting as indicators for patterns and processes associated with urban areas were calculated for matrix areas surrounding each selected grassland fragment to quantify the position of each grassland remnant along an urbanisation gradient. The grassland fragments were objectively classified into two classes of urbanisation, namely "exurban" and "urban" based on the urbanisation measure values. Grazing was recorded in some exurban grasslands and mowing in some urban grassland fragments. Unmanaged grassland fragments were present in both urban and exurban areas. Fine-scale biophysical landscape function was determined by executing the Landscape Function Analysis (LFA) method. LFA assesses fine-scale landscape patchiness (entailing resource conserving potential and erosion resistance) and 11 soil surface indicators to produce three main LFA parameters (stability, infiltration, and nutrient cycling), which indicates how well a system is functioning in terms of fine-scale biophysical soil processes and characteristics. The aim of this study was to determine the effects of urbanisation and associated management practices on fine-scale biophysical landscape function of urban and exurban

  2. Plant diversity and functional groups affect Si and Ca pools in aboveground biomass of grassland systems.

    PubMed

    Schaller, Jörg; Roscher, Christiane; Hillebrand, Helmut; Weigelt, Alexandra; Oelmann, Yvonne; Wilcke, Wolfgang; Ebeling, Anne; Weisser, Wolfgang W

    2016-09-01

    Plant diversity is an important driver of nitrogen and phosphorus stocks in aboveground plant biomass of grassland ecosystems, but plant diversity effects on other elements also important for plant growth are less understood. We tested whether plant species richness, functional group richness or the presence/absence of particular plant functional groups influences the Si and Ca concentrations (mmol g(-1)) and stocks (mmol m(-2)) in aboveground plant biomass in a large grassland biodiversity experiment (Jena Experiment). In the experiment including 60 temperate grassland species, plant diversity was manipulated as sown species richness (1, 2, 4, 8, 16) and richness and identity of plant functional groups (1-4; grasses, small herbs, tall herbs, legumes). We found positive species richness effects on Si as well as Ca stocks that were attributable to increased biomass production. The presence of particular functional groups was the most important factor explaining variation in aboveground Si and Ca stocks (mmol m(-2)). Grass presence increased the Si stocks by 140 % and legume presence increased the Ca stock by 230 %. Both the presence of specific plant functional groups and species diversity altered Si and Ca stocks, whereas Si and Ca concentration were affected mostly by the presence of specific plant functional groups. However, we found a negative effect of species diversity on Si and Ca accumulation, by calculating the deviation between mixtures and mixture biomass proportions, but in monoculture concentrations. These changes may in turn affect ecosystem processes such as plant litter decomposition and nutrient cycling in grasslands. PMID:27164912

  3. Exotic grasslands on reclaimed midwestern coal mines: An ornithological perspective

    SciTech Connect

    Scott, P.E.; Lima, S.L.

    2004-07-01

    The largest grasslands in Indiana and Illinois are on reclaimed surface coal mines, which are numerous in the Illinois Coal Basin. The reclamation goal of establishing a vegetation cover with inexpensive, hardy exotic grass species (e.g., tall fescue, smooth brome) inadvertently created persistent, large grassland bird refuges. We review research documenting the importance of these sites for native prairie birds. On mines, grassland specialist birds (restricted to grassland throughout their range) prefer sites dominated by exotic grasses to those rich in forbs, whereas nonspecialist bird species show no significant preference. Midwestern mine grasslands potentially could be converted into landscapes that include native warm-season grasses and forbs adapted to the relatively dry, poor soil conditions, in addition to the present successful exotic grass stands. A key question is whether native mixtures will resist conversion to forb-rich or woody growth over the long term, as the exotic grasses have done.

  4. Effects of Holocene vegetation change on soils across the forest-grassland transition, northern Minnesota, and implications for erosion processes

    NASA Astrophysics Data System (ADS)

    Mason, Joseph; Kasmerchak, Chase; Keita, Hawa; Liang, Mengyu; Gruley, Kristine

    2016-04-01

    Boundaries between forest and grassland in the midlatitudes and their shifts in response to Holocene climatic change, provide opportunities to detect effects of life on landscapes. In northern Minnesota, USA, paleoecological research has documented that grassland and/or savanna expanded eastward in the dry early to middle Holocene. In the late Holocene, forest cover expanded westward at the expense of savanna and grassland. We studied soils at 20 sites spanning the forest-grassland transition. A dramatic change in soil morphology coincides approximately, though not exactly, with that transition as recorded in 1870s-1880s land surveys, suggesting that soils change rapidly in response to forest expansion (we are attempting to constrain the timescale of response through radiocarbon dating of deep soil organic matter in which stable C isotopes record past presence of grassland). The key changes from grassland to forest are loss of organic matter below a thin surface A horizon and greatly enhanced mobility and downward translocation of clay - particularly smectite - in forest soils. This results in upper soil horizons that have relatively low smectite content and low microaggregate stability (as detected through laser diffraction analysis of aggregate disintegration in laboratory experiments), especially below the thin A horizon. The best explanation for this change appears to involve differences in how OM is added to and accumulated in the soil under forest and grassland; soil acidity and base saturation change more gradually eastward along a gradient more likely to reflect climate than vegetation. Evidence of bioturbation (especially gopher burrowing) is much more common at former grassland sites. In addition to mixing OM downward in the soil, burrowing moves detrital carbonates upward, probably enhancing OM accumulation and aggregate stability. Research on geomorphic response to Holocene climatic change in the Midwestern US has often emphasized higher potential

  5. Seasonal dynamics of microbial community composition and function in oak canopy and open grassland soils

    USGS Publications Warehouse

    Waldrop, M.P.; Firestone, M.K.

    2006-01-01

    Soil microbial communities are closely associated with aboveground plant communities, with multiple potential drivers of this relationship. Plants can affect available soil carbon, temperature, and water content, which each have the potential to affect microbial community composition and function. These same variables change seasonally, and thus plant control on microbial community composition may be modulated or overshadowed by annual climatic patterns. We examined microbial community composition, C cycling processes, and environmental data in California annual grassland soils from beneath oak canopies and in open grassland areas to distinguish factors controlling microbial community composition and function seasonally and in association with the two plant overstory communities. Every 3 months for up to 2 years, we monitored microbial community composition using phospholipid fatty acid (PLFA) analysis, microbial biomass, respiration rates, microbial enzyme activities, and the activity of microbial groups using isotope labeling of PLFA biomarkers (13C-PLFA) . Distinct microbial communities were associated with oak canopy soils and open grassland soils and microbial communities displayed seasonal patterns from year to year. The effects of plant species and seasonal climate on microbial community composition were similar in magnitude. In this Mediterranean ecosystem, plant control of microbial community composition was primarily due to effects on soil water content, whereas the changes in microbial community composition seasonally appeared to be due, in large part, to soil temperature. Available soil carbon was not a significant control on microbial community composition. Microbial community composition (PLFA) and 13C-PLFA ordination values were strongly related to intra-annual variability in soil enzyme activities and soil respiration, but microbial biomass was not. In this Mediterranean climate, soil microclimate appeared to be the master variable controlling

  6. Influence of topography on density of grassland passerines in pastures

    USGS Publications Warehouse

    Renfrew, R.B.; Ribic, C.A.

    2002-01-01

    Pastures provide substantial habitat for grassland birds of management concern in the Driftless Area of southwestern Wisconsin. The rolling topography in this region is characterized by lowland valleys surrounded by relatively steep and often wooded slopes which are set apart from more expansive treeless uplands. We hypothesized that there would be lower densities of area sensitive grassland passerines in lowland grasslands compared to upland grasslands because of their preference for larger more open grasslands. To test this hypothesis and assess how well pasture area and vegetation structure predicted grassland passerine density compared to upland/lowland status, we conducted point counts of birds in 60 pastures in May-June 1997 and 1998. Upland pastures generally supported greater densities of grassland passerines than lowland pastures. Densities of Savannah sparrow (Passerculus sandwichensis) and bobolink (Dolichonyx oryzivorus) were significantly higher in upland pastures than in lowland pastures. Grasshopper sparrow (Ammodramus savannarum) density was significantly higher on uplands in one of the study years. The density of eastern meadowlark (Sturnella magna), western meadowlark (S. neglecta) and sedge wren (Cistothorus platensis) did not differ significandy between uplands and lowlands. Grassland passerine density was also predicted by pasture size and vegetation structure. Densities of bobolink and grasshopper sparrow were higher in larger pastures. Bobolink and Savannah sparrow occurred on pastures with greater vegetation height-density and less bare ground; bobolink also preferred shallower litter depths. Lowland pastures supported grassland bird species of management concern and should not be neglected. However, we recommend that pasture management for grassland passerines in areas of variable topography favor relatively large upland pastures that will contain higher densities of species of management concern.

  7. Monitoring soil greenhouse gas emissions from managed grasslands

    NASA Astrophysics Data System (ADS)

    Díaz-Pinés, Eugenio; Lu, Haiyan; Butterbach-Bahl, Klaus; Kiese, Ralf

    2014-05-01

    Grasslands in Central Europe are of enormous social, ecological and economical importance. They are intensively managed, but the influence of different common practices (i.e. fertilization, harvesting) on the total greenhouse gas budget of grasslands is not fully understood, yet. In addition, it is unknown how these ecosystems will react due to climate change. Increasing temperatures and changing precipitation will likely have an effect on productivity of grasslands and on bio-geo-chemical processes responsible for emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). In the frame of the TERENO Project (www.tereno.net), a long-term observatory has been implemented in the Ammer catchment, southern Germany. Acting as an in situ global change experiment, 36 big lysimeters (1 m2 section, 150 cm height) have been translocated along an altitudinal gradient, including three sites ranging from 600 to 860 meters above sea level. In addition, two treatments have been considered, corresponding to different management intensities. The overall aim of the pre-alpine TERENO observatory is improving our understanding of the consequences of climate change and management on productivity, greenhouse gas balance, soil nutritional status, nutrient leaching and hydrology of grasslands. Two of the sites are equipped with a fully automated measurement system in order to continuously and accurately monitor the soil-atmosphere greenhouse gas exchange. Thus, a stainless steel chamber (1 m2 section, 80 cm height) is controlled by a robotized system. The chamber is hanging on a metal structure which can move both vertically and horizontally, so that the chamber is able to be set onto each of the lysimeters placed on the field. Furthermore, the headspace of the chamber is connected with a gas tube to a Quantum Cascade Laser, which continuously measures CO2, CH4, N2O and H2O mixing ratios. The chamber acts as a static chamber and sets for 15 minutes onto each lysimeter

  8. Three-dimensional imaging, change detection, and stability assessment during the centerline trench levee seepage experiment using terrestrial light detection and ranging technology, Twitchell Island, California, 2012

    USGS Publications Warehouse

    Bawden, Gerald W.; Howle, James; Bond, Sandra; Shriro, Michelle; Buck, Peter

    2014-01-01

    A full scale field seepage test was conducted on a north-south trending levee segment of a now bypassed old meander belt on Twitchell Island, California, to understand the effects of live and decaying root systems on levee seepage and slope stability. The field test in May 2012 was centered on a north-south trench with two segments: a shorter control segment and a longer seepage test segment. The complete length of the trench area measured 40.4 meters (m) near the levee centerline with mature trees located on the waterside and landside of the levee flanks. The levee was instrumented with piezometers and tensiometers to measure positive and negative porewater pressures across the levee after the trench was flooded with water and held at a constant hydraulic head during the seepage test—the results from this component of the experiment are not discussed in this report. We collected more than one billion three-dimensional light detection and ranging (lidar) data points before, during, and after the centerline seepage test to assess centimeter-scale stability of the two trees and the levee crown. During the seepage test, the waterside tree toppled (rotated 20.7 degrees) into the water. The landside tree rotated away from the levee by 5 centimeters (cm) at a height of 2 m on the tree. The paved surface of the levee crown had three regions that showed subsidence on the waterside of the trench—discussed as the northern, central, and southern features. The northern feature is an elongate region that subsided 2.1 cm over an area with an average width of 1.35 m that extends 15.8 m parallel to the trench from the northern end of the trench to just north of the trench midpoint, and is associated with a crack 1 cm in height that formed during the seepage test on the trench wall. The central subsidence feature is a semicircular region on the waterside of the trench that subsided by as much as 6.2 cm over an area 3.4 m wide and 11.2 m long. The southern feature is an elongate

  9. Plant diversity effects on root decomposition in grasslands

    NASA Astrophysics Data System (ADS)

    Chen, Hongmei; Mommer, Liesje; van Ruijven, Jasper; de Kroon, Hans; Gessler, Arthur; Scherer-Lorenzen, Michael; Wirth, Christian; Weigelt, Alexandra

    2016-04-01

    Loss of plant diversity impairs ecosystem functioning. Compared to other well-studied processes, we know little about whether and how plant diversity affects root decomposition, which is limiting our knowledge on biodiversity-carbon cycling relationships in the soil. Plant diversity potentially affects root decomposition via two non-exclusive mechanisms: by providing roots of different substrate quality and/or by altering the soil decomposition environment. To disentangle these two mechanisms, three decomposition experiments using a litter-bag approach were conducted on experimental grassland plots differing in plant species richness, functional group richness and functional group composition (e.g. presence/absence of grasses, legumes, small herbs and tall herbs, the Jena Experiment). We studied: 1) root substrate quality effects by decomposing roots collected from the different experimental plant communities in one common plot; 2) soil decomposition environment effects by decomposing standard roots in all experimental plots; and 3) the overall plant diversity effects by decomposing community roots in their 'home' plots. Litter bags were installed in April 2014 and retrieved after 1, 2 and 4 months to determine the mass loss. We found that mass loss decreased with increasing plant species richness, but not with functional group richness in the three experiments. However, functional group presence significantly affected mass loss with primarily negative effects of the presence of grasses and positive effects of the presence of legumes and small herbs. Our results thus provide clear evidence that species richness has a strong negative effect on root decomposition via effects on both root substrate quality and soil decomposition environment. This negative plant diversity-root decomposition relationship may partly account for the positive effect of plant diversity on soil C stocks by reducing C loss in addition to increasing primary root productivity. However, to fully

  10. Diversity Promotes Temporal Stability across Levels of Ecosystem Organization in Experimental Grasslands

    PubMed Central

    Proulx, Raphaël; Wirth, Christian; Voigt, Winfried; Weigelt, Alexandra; Roscher, Christiane; Attinger, Sabine; Baade, Jussi; Barnard, Romain L.; Buchmann, Nina; Buscot, François; Eisenhauer, Nico; Fischer, Markus; Gleixner, Gerd; Halle, Stefan; Hildebrandt, Anke; Kowalski, Esther; Kuu, Annely; Lange, Markus; Milcu, Alex; Niklaus, Pascal A.; Oelmann, Yvonne; Rosenkranz, Stephan; Sabais, Alexander; Scherber, Christoph; Scherer-Lorenzen, Michael; Scheu, Stefan; Schulze, Ernst-Detlef; Schumacher, Jens; Schwichtenberg, Guido; Soussana, Jean-François; Temperton, Vicky M.; Weisser, Wolfgang W.; Wilcke, Wolfgang; Schmid, Bernhard

    2010-01-01

    The diversity–stability hypothesis states that current losses of biodiversity can impair the ability of an ecosystem to dampen the effect of environmental perturbations on its functioning. Using data from a long-term and comprehensive biodiversity experiment, we quantified the temporal stability of 42 variables characterizing twelve ecological functions in managed grassland plots varying in plant species richness. We demonstrate that diversity increases stability i) across trophic levels (producer, consumer), ii) at both the system (community, ecosystem) and the component levels (population, functional group, phylogenetic clade), and iii) primarily for aboveground rather than belowground processes. Temporal synchronization across studied variables was mostly unaffected with increasing species richness. This study provides the strongest empirical support so far that diversity promotes stability across different ecological functions and levels of ecosystem organization in grasslands. PMID:20967213

  11. Competition, resources, and vegetation during 10 years in native grassland.

    PubMed

    Wilson, Scott D

    2007-12-01

    A 10-year experiment tested for variation in competition intensity over time in a natural grassland at the northern edge of the Great Plains. Growing-season precipitation varied fivefold during the study. All ecosystem-level variables varied significantly among years, and most covaried in expected ways. The covers of all common grasses possessing the C3 photosynthetic pathway varied significantly among years; in contrast, all common species with traits associated with drought tolerance (a C4 grass, a lichen, a spikemoss, and a subshrub) did not vary. Annual transplant experiments measured the competitive effects of neighbors on the growth of individuals of the native grass Bouteloua gracilis. A significant interaction between year and competition showed that competition intensity varied among years. The size of this effect, however, was small (eta2 = 0.074) relative to the size of the direct effect of competition (eta2 = 0.20) or the year in which the experiment was conducted (eta2 = 0.51). Further, competition intensity was not significantly related to any variable describing standing crop or resources, or species richness. Species richness was highest in years with high precipitation, standing crop, and individual growth, due to the recruitment of rare species that were absent from dry years. In summary, variation in competition intensity was statistically significant but had small effects relative to the direct effects of climate. PMID:18229830

  12. Response of a keystone rodent to landscape-scale restoration of desert grasslands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Over the last century, many grasslands in the Chihuahuan Desert have converted to shrublands dominated by creosotebush (Larrea tridentata). The loss and spatial isolation of perennial grasslands has led to declines of grassland-dependent wildlife species. Grassland restoration efforts have been domi...

  13. Staged invasions across disparate grasslands: effects of seed provenance, consumers and disturbance on productivity and species richness.

    PubMed

    Maron, John L; Auge, Harald; Pearson, Dean E; Korell, Lotte; Hensen, Isabell; Suding, Katharine N; Stein, Claudia

    2014-04-01

    Exotic plant invasions are thought to alter productivity and species richness, yet these patterns are typically correlative. Few studies have experimentally invaded sites and asked how addition of novel species influences ecosystem function and community structure and examined the role of competitors and/or consumers in mediating these patterns. We invaded disturbed and undisturbed subplots in and out of rodent exclosures with seeds of native or exotic species in grasslands in Montana, California and Germany. Seed addition enhanced aboveground biomass and species richness compared with no-seeds-added controls, with exotics having disproportionate effects on productivity compared with natives. Disturbance enhanced the effects of seed addition on productivity and species richness, whereas rodents reduced productivity, but only in Germany and California. Our results demonstrate that experimental introduction of novel species can alter ecosystem function and community structure, but that local filters such as competition and herbivory influence the magnitude of these impacts. PMID:24467348

  14. Rapid response of a grassland ecosystem to an experimental manipulation of a keystone rodent and domestic livestock.

    PubMed

    Davidson, Ana D; Ponce, Eduardo; Lightfoot, David C; Fredrickson, Ed L; Brown, James H; Cruzado, Juan; Brantley, Sandra L; Sierra-Corona, Rodrigo; List, Rurik; Toledo, David; Ceballos, Gerardo

    2010-11-01

    Megaherbivores and small burrowing mammals commonly coexist and play important functional roles in grassland ecosystems worldwide. The interactive effects of these two functional groups of herbivores in shaping the structure and function of grassland ecosystems are poorly understood. In North America's central grasslands, domestic cattle (Bos taurus) have supplanted bison (Bison bison), and now coexist with prairie dogs (Cynomys spp.), a keystone burrowing rodent. Understanding the ecological relationships between cattle and prairie dogs and their independent and interactive effects is essential to understanding the ecology and important conservation issues affecting North American grassland ecosystems. To address these needs, we established a long-term manipulative experiment that separates the independent and interactive effects of prairie dogs and cattle using a 2 x 2 factorial design. Our study is located in the Janos-Casas Grandes region of northwestern Chihuahua, Mexico, which supports one of the largest remaining complexes of black-tailed prairie dogs (C. ludovicianus). Two years of posttreatment data show nearly twofold increases in prairie dog abundance on plots grazed by cattle compared to plots without cattle. This positive effect of cattle on prairie dogs resulted in synergistic impacts when they occurred together. Vegetation height was significantly lower on the plots where both species co-occurred compared to where either or both species was absent. The treatments also significantly affected abundance and composition of other grassland animal species, including grasshoppers and banner-tailed kangaroo rats (Dipodomys spectabilis). Our results demonstrate that two different functional groups of herbivorous mammals, burrowing mammals and domestic cattle, have distinctive and synergistic impacts in shaping the structure and function of grassland ecosystems. PMID:21141180

  15. Organic vs. Conventional Grassland Management: Do 15N and 13C Isotopic Signatures of Hay and Soil Samples Differ?

    PubMed Central

    Klaus, Valentin H.; Hölzel, Norbert; Prati, Daniel; Schmitt, Barbara; Schöning, Ingo; Schrumpf, Marion; Fischer, Markus; Kleinebecker, Till

    2013-01-01

    Distinguishing organic and conventional products is a major issue of food security and authenticity. Previous studies successfully used stable isotopes to separate organic and conventional products, but up to now, this approach was not tested for organic grassland hay and soil. Moreover, isotopic abundances could be a powerful tool to elucidate differences in ecosystem functioning and driving mechanisms of element cycling in organic and conventional management systems. Here, we studied the δ15N and δ13C isotopic composition of soil and hay samples of 21 organic and 34 conventional grasslands in two German regions. We also used Δδ15N (δ15N plant - δ15N soil) to characterize nitrogen dynamics. In order to detect temporal trends, isotopic abundances in organic grasslands were related to the time since certification. Furthermore, discriminant analysis was used to test whether the respective management type can be deduced from observed isotopic abundances. Isotopic analyses revealed no significant differences in δ13C in hay and δ15N in both soil and hay between management types, but showed that δ13C abundances were significantly lower in soil of organic compared to conventional grasslands. Δδ15N values implied that management types did not substantially differ in nitrogen cycling. Only δ13C in soil and hay showed significant negative relationships with the time since certification. Thus, our result suggest that organic grasslands suffered less from drought stress compared to conventional grasslands most likely due to a benefit of higher plant species richness, as previously shown by manipulative biodiversity experiments. Finally, it was possible to correctly classify about two third of the samples according to their management using isotopic abundances in soil and hay. However, as more than half of the organic samples were incorrectly classified, we infer that more research is needed to improve this approach before it can be efficiently used in practice

  16. GHGs balance in a land use change process from grassland to short rotation coppice of poplar

    NASA Astrophysics Data System (ADS)

    Sabbatini, Simone; Arriga, Nicola; Baiocco, Andrea; Boschi, Alessio; Castaldi, Simona; Consalvo, Claudia; Gioli, Beniamino; Matteucci, Giorgio; Tomassucci, Michele; Zaldei, Alessandro; Papale, Dario

    2013-04-01

    At present one of the fastest spreading renewable energy sources are bioenergy cultivations. Millions of hectares of traditional crops all over the Europe are expected to be converted in energy crops in the near future, in order to produce green energy and contrast global warming. Last year, in the context of the GHG-Europe FP7 project we set up an experiment to verify the effects on the green-house gases balance of a land use change from traditional agriculture to short rotation coppice of poplar clones in central Italy. CO2 fluxes measured during the last growing season through three Eddy Covariance masts - two on poplar plantations of different ages and one over a reference site (grassland) - have been analysed. We also monitored CO2, CH4 and N2O fluxes from soil measured using chambers in order to better understand the contribution of other GHGs. The two poplar plantations showed a similar uptake of Carbon, 368 g C m-2 year-1 and 358 g C m-2 year-1, while the grassland absorbed 220 g C m-2 year-1 during the same period. Soil respiration in average was higher for the youngest plantation of poplar and for the grassland, lower for the oldest one, where soil is undisturbed from more time. In all the sites we measured low emissions during the winter (between 80 and 150 mg CO2 m-2 h-1), progressively higher in the spring and early summer with growing temperatures (up to 650 mg CO2 m-2 h-1), quite low during the summer because of a strong drought, while the highest values were recorded in September (ca. 1100 mg CO2 m-2 h-1 in the grassland and youngest poplar) after important rain events. Fluxes of N2O and CH4 from soil are very low: little absorption of CH4 in the grassland (values between 0 and -18.75 μg m-2 h-1), with peak after fertilization; in the SRC little absorption or emission with no clear seasonal pattern. Insignificant fluxes of N2O in all crops (even in the grassland after fertilization). The carbon fluxes measured are strongly related to the particular

  17. Environmental Controls and Management Effects on Ecosystem Carbon Exchange in Two Grazed Temperate Grasslands

    NASA Astrophysics Data System (ADS)

    Ni Choncubhair, O.; Humphreys, J.; Lanigan, G.

    2013-12-01

    Temperate grasslands constitute over 30% of the Earth's naturally-occurring biomes and make an important contribution towards the partial mitigation of anthropogenic greenhouse gas emissions by terrestrial ecosystems. Accumulation of carbon (C) in grassland systems predominantly takes place in below-ground repositories, enhanced by the presence of a stable soil environment with low carbon turnover rates, active rhizodeposition and high levels of residue and organic inputs. However, this C sequestration is strongly influenced by soil characteristics and climatic variables. Furthermore, in managed pasture systems, carbon exchange across the soil-atmosphere boundary is additionally affected by management activities, such as biomass removal, grazing events and the deposition or application of organic amendments. These biotic and abiotic factors contribute greatly towards the large uncertainty associated with the carbon balance of grassland ecosystems and demand further analysis. In the present study, the controls and drivers of carbon dynamics in two rotationally-grazed grasslands in Ireland were examined. The sites experience similar temperate climatic regimes but differ in soil texture classification and stocking rate. Eddy covariance measurements of net ecosystem exchange of carbon were complemented by regular assessment of standing biomass, leaf cover, harvest exports and organic amendment inputs. Our study showed that mild weather conditions and an extended growing season sustained net C accumulation at both sites for at least ten months of the year. Despite differing soil drainage characteristics, winter fluxes of net carbon exchange and its component fluxes, gross photosynthesis and ecosystem respiration, were highly comparable between the two sites. Management practices during the active growing season exerted a strong influence on both the direction and the rate of C exchange in the grassland systems, with a strong dependence, however, on the timing and

  18. Degradation increase responses of priming effects to temperature in Tibetan alpine grasslands

    NASA Astrophysics Data System (ADS)

    Sun, Yue; Li, Qianru; Schleuss, Per; Hua, Ouyang; Kuzyakov, Yakov

    2016-04-01

    Kobresia grassland in Tibet plateau, with a rich storage of soil organic carbon (SOC), is very important to both ecosystem function and the livelihoods of local pastoral communities. But its intensive degradation in recent decades has led to unclear consequences for SOC stocks and dynamics. Kobresia grassland acts as a critical "first response region" to climate change, where the SOC decomposition is highly sensitive to temperature, and can produce positive C climate feedback. Priming effects, induced by inputs of labile organic carbon (LOC), can also affect SOC dynamic. Therefore, knowledge about how the priming effects response to temperature, and how their interactions affect SOC decomposition are central to understanding the carbon cycle of Tibet plateau under global warming. To this ends, we conducted a laboratory incubation experiment with the non-degraded soil collected from intact Kobresia patches, and degraded soil collected from crust patches, labeled with 14C-glucose in high/low level and incubated under 0 °C, 10 °C and 20 °C for 80 days. Cumulated CO2 emission increased significantly with temperature. Degraded soil showed lower CO2 emission at 0 °C, but significant higher CO2 emission at higher temperature compared to that of non-degraded soil. Priming positively responded to increasing temperature, with 78.9% increment in degraded soil and 12.9% in non-degraded soil on average, and at 20 °C, it was significant higher in degraded soil than non-degraded soil. Low-level glucose input led to the positive priming effects, while high-level glucose induced the negative priming. Higher temperature led to higher microbial activity (i.e., qCO2) and enzyme activity (i.e., β-glucosidases, chitinase, cellobiohydrolase and Xylosidase). Vmax of enzyme was significantly higher in degraded soil than in non-degraded soil, exhibiting a positive linear regression with priming effects. In conclusion, increase in temperature improved priming effects via higher microbe

  19. A modeling study of shelf circulation off northern California in the region of the Coastal Ocean Dynamics Experiment 2. Simulations and comparisons with observations

    NASA Astrophysics Data System (ADS)

    Gan, Jianping; Allen, J. S.

    2002-11-01

    This is the second part of a modeling study of wind-forced flow on the continental shelf off northern California in the region (37°-40°N) of the Coastal Ocean Dynamics Experiment (CODE). [2002] analyzed the shelf flow response to idealized wind stress forcing in a process-oriented study. The study here applies forcing from observed winds and heat flux for April-May 1982 and compares the model results with moored current and temperature measurements. The Princeton Ocean Model (POM) is used in a three-dimensional limited area domain with a high-resolution curvilinear grid (approximately 1 km horizontal spacing, 60 vertical levels) and realistic coastline and bottom topography. The objectives of the study are to simulate the response of the shelf circulation field to time-varying observed wind stress and heat flux, to compare model results with oceanographic observations to establish confidence in the model, and to subsequently analyze the model fields and the model dynamical balances to help understand the behavior of the observed flow. The model variables show overall good agreement with corresponding observations. Similar to the conclusions by [2002], it is found that the alongshore variability of upwelling is mainly controlled by the interaction of the wind-forced shelf flow with the coastline and bottom topography. Different dynamical regimes in the regions north and south of the coastal capes formed by Pt. Reyes and Pt. Arena and in the more uniform region between these capes are identified and investigated. The results demonstrate that the coastal capes play a dominant role in causing alongshore variability of the upwelling flow, including the setup of an alongshore pressure gradient that forces northward currents during relaxation of southward upwelling favorable winds. An analysis of the balance of terms in the equation for potential temperature indicates that across-shore temperature advection is the major contributor to the cooling of coastal water during

  20. The Experiences of Low-Income Latino/a Students in the California Community College System at a Time of Education Budget Cuts

    ERIC Educational Resources Information Center

    Chacon, Justin Akers

    2013-01-01

    Budget cuts have reduced courses and student services within California community colleges. This coincides with the growth of low-income Latino male (Latinos) and Latina female (Latinas) student enrollment. Budget cuts have been implemented throughout the system, including in the Extended Opportunity Programs and Services (EOPS), which…

  1. Andean grasslands are as productive as tropical cloud forests

    NASA Astrophysics Data System (ADS)

    Oliveras, I.; Girardin, C.; Doughty, C. E.; Cahuana, N.; Arenas, C. E.; Oliver, V.; Huaraca Huasco, W.; Malhi, Y.

    2014-11-01

    We aim to assess net primary productivity (NPP) and carbon cycling in Andean tropical alpine grasslands (puna) and compare it with NPP of tropical montane cloud forests. We ask the following questions: (1) how do NPP and soil respiration of grasslands vary over the seasonal cycle? (2) how do burning and grazing affect puna productivity? (3) if the montane forest expands into the puna, what will be the resulting change in productivity? The study sites are located at the South-eastern Peruvian Andes; one grassland site and the forest sites are in Wayqecha biological station, and another grassland site in Manu National Park. At each grassland site, we selected a burnt and an unburnt area, installed unfenced and fenced transects in each area, and monitored above-ground productivity (NPPAG), below-ground productivity (NPPBG) and soil respiration (Rs) for 2 yr. In the forest, we monitored NPPAG, NPPBG and Rs for 2-4 yr. Grassland NPP varied between 4.6 ± 0.25 (disturbed areas) to 15.3 ± 0.9 Mg C ha-1 yr-1 (undisturbed areas) and cloud forest NPP was between 7.05 ± 0.39 and 8.0 ± 0.47 Mg C ha-1 yr-1, while soil carbon stocks were in the range of 126 ± 22 to 285 ± 31 Mg C ha-1. There were no significant differences on NPP between the puna and forest sites. The most undisturbed site had significantly higher NPP than other grassland sites, but no differences were found when relating grazing and fire at other sites. There were lower residence times of above-ground biomass compared to below-ground biomass. There was a strong seasonal signal on grassland NPPAG and NPPBG, with a shift on allocation at the beginning of the austral summer. High elevation tropical grasslands can be as productive as adjacent cloud forests, but have very different carbon cycling and retention properties than cloud forests.

  2. Ammonia emission after slurry application to grassland in Switzerland

    NASA Astrophysics Data System (ADS)

    Häni, Christoph; Sintermann, Jörg; Kupper, Thomas; Jocher, Markus; Neftel, Albrecht

    2016-01-01

    Loss of ammonia (NH3) after field application of livestock slurry contributes between 30% and 50% of agricultural NH3 emissions from European countries. The objectives of this study were to re-evaluate NH3 emissions following application of cattle and pig slurry to grassland in Switzerland and to investigate the effectiveness of abatement techniques. In 17 field experiments, NH3 emissions were determined with a micrometeorological approach, relating the emission to the measured concentration by means of atmospheric dispersion modelling. The cattle slurry applied exhibited an average dry matter content of 3.3% (range between 1.0% and 6.7% dry matter). The emission after application of cattle slurry spread with a splash plate (referred to as reference technique) ranged from 10% to 47% of applied Total Ammoniacal Nitrogen (% of TAN) and averaged to 25% of TAN. This range of losses is lower by approx. a factor of two compared to measurements from earlier Swiss experiments. Applications with trailing hose and trailing shoe systems yielded an average reduction of 51% and 53%, respectively, relative to the reference technique. A regression analysis showed that the dry matter content of the slurry and the air temperature are important drivers for NH3 emission.

  3. Optimising stocking rate and grazing management to enhance environmental and production outcomes for native temperate grasslands

    NASA Astrophysics Data System (ADS)

    Badgery, Warwick; Zhang, Yingjun; Huang, Ding; Broadfoot, Kim; Kemp, David; Mitchell, David

    2015-04-01

    Stocking rate and grazing management can be altered to enhance the sustainable production of grasslands but the relative influence of each has not often been determined for native temperate grasslands. Grazing management can range from seasonal rests through to intensive rotational grazing involving >30 paddocks. In large scale grazing, it can be difficult to segregate the influence of grazing pressure from the timing of utilisation. Moreover, relative grazing pressure can change between years as seasonal conditions influence grassland production compared to the relative constant requirements of animals. This paper reports on two studies in temperate native grasslands of northern China and south eastern Australia that examined stocking rate and regionally relevant grazing management strategies. In China, the grazing experiment involved combinations of a rest, moderate or heavy grazing pressure of sheep in spring, then moderate or heavy grazing in summer and autumn. Moderate grazing pressure at 50% of the current district average, resulted in the better balance between maintaining productive and diverse grasslands, a profitable livestock system, and mitigation of greenhouse gases through increased soil carbon, methane uptake by the soil, and efficient methane emissions per unit of weight gain. Spring rests best maintained a desirable grassland composition, but had few other benefits and reduced livestock productivity due to lower feed quality from grazing later in the season. In Australia, the grazing experiment compared continuous grazing to flexible 4- and 20-paddock rotational grazing systems with sheep. Stocking rates were adjusted between systems biannually based on the average herbage mass of the grassland. No treatment degraded the perennial pasture composition, but ground cover was maintained at higher levels in the 20-paddock system even though this treatment had a higher stocking rate. Overall there was little difference in livestock production (e.g. kg

  4. Timing of climate variability and grassland productivity

    PubMed Central

    Craine, Joseph M.; Nippert, Jesse B.; Elmore, Andrew J.; Skibbe, Adam M.; Hutchinson, Stacy L.; Brunsell, Nathaniel A.

    2012-01-01

    Future climates are forecast to include greater precipitation variability and more frequent heat waves, but the degree to which the timing of climate variability impacts ecosystems is uncertain. In a temperate, humid grassland, we examined the seasonal impacts of climate variability on 27 y of grass productivity. Drought and high-intensity precipitation reduced grass productivity only during a 110-d period, whereas high temperatures reduced productivity only during 25 d in July. The effects of drought and heat waves declined over the season and had no detectable impact on grass productivity in August. If these patterns are general across ecosystems, predictions of ecosystem response to climate change will have to account not only for the magnitude of climate variability but also for its timing. PMID:22331914

  5. Simulated heat waves affected alpine grassland only in combination with drought

    NASA Astrophysics Data System (ADS)

    De Boeck, Hans J.; Bassin, Seraina; Verlinden, Maya; Zeiter, Michaela; Hiltbrunner, Erika

    2016-04-01

    The Alpine region is warming fast, leading to an increase in the frequency and intensity of climate extremes. Currently, it is unclear whether alpine ecosystems are sensitive or resistant to such extremes. In an experiment carried out in the Swiss Alps, we subjected Swiss alpine grassland communities to heat waves with varying intensity (5-10 °C warming) by transplanting monoliths to four different elevations (2440-660 m a.s.l.) for 17 days. Half of the monoliths were regularly irrigated while the other half were deprived of irrigation to additionally induce a drought at each site. We found that heat waves had no significant short-term impacts on fluorescence (Fv/Fm, a stress indicator), senescence and aboveground productivity if irrigation was provided. However, when heat waves coincided with drought, plants showed clear signs of stress, resulting in vegetation browning and reduced phytomass production. This likely resulted from direct drought effects, but also, as measurements of stomatal conductance and canopy temperatures suggest, from increased high-temperature stress as water scarcity decreased heat mitigation through transpiration. The immediate responses to heat waves (with or without droughts) recorded in these alpine grasslands were similar to those observed in the more extensively studied grasslands from temperate climates. Climate extreme impacts may differ in the longer run, however, because the short growing season in alpine environments likely constrains recovery.

  6. A semi-ellipsoid-model based fuzzy classifier to map grassland in Inner Mongolia, China

    NASA Astrophysics Data System (ADS)

    Lan, Hai; Xie, Yichun

    2013-11-01

    Remote sensing techniques offer effective means for mapping plant communities. However, mapping grassland with fine vegetative classes over large areas has been challenging for either the coarse resolutions of remotely sensed images or the high costs of acquiring images with high-resolutions. An improved hybrid-fuzzy-classifier (HFC) derived from a semi-ellipsoid-model (SEM) is developed in this paper to achieve higher accuracy for classifying grasslands with Landsat images. The Xilin River Basin, Inner Mongolia, China, is chosen as the study area, because an acceptable volume of ground truthing data was previously collected by multiple research communities. The accuracy assessment is based on the comparison of the classification outcomes from four types of image sets: (1) Landsat ETM+ August 14, 2004, (2) Landsat TM August 12, 2009, (3) the fused images of ETM+ with CBERS, and (4) TM with CBERS, respectively, and by three classifiers, the proposed HFC-SEM, the tetragonal pyramid model (TPM) based HFC, and the support vector machine method. In all twelve classification experiments, the HFC-SEM classifier had the best overall accuracy statistics. This finding indicates that the medium resolution Landsat images can be used to map grassland vegetation with good vegetative detail when the proper classifier is applied.

  7. Scale-dependent feedbacks between patch size and plant reproduction in desert grassland

    USGS Publications Warehouse

    Svejcar, Lauren N.; Bestelmeyer, Brandon T.; Duniway, Michael C.; James, Darren K.

    2015-01-01

    Theoretical models suggest that scale-dependent feedbacks between plant reproductive success and plant patch size govern transitions from highly to sparsely vegetated states in drylands, yet there is scant empirical evidence for these mechanisms. Scale-dependent feedback models suggest that an optimal patch size exists for growth and reproduction of plants and that a threshold patch organization exists below which positive feedbacks between vegetation and resources can break down, leading to critical transitions. We examined the relationship between patch size and plant reproduction using an experiment in a Chihuahuan Desert grassland. We tested the hypothesis that reproductive effort and success of a dominant grass (Bouteloua eriopoda) would vary predictably with patch size. We found that focal plants in medium-sized patches featured higher rates of grass reproductive success than when plants occupied either large patch interiors or small patches. These patterns support the existence of scale-dependent feedbacks in Chihuahuan Desert grasslands and indicate an optimal patch size for reproductive effort and success in B. eriopoda. We discuss the implications of these results for detecting ecological thresholds in desert grasslands.

  8. Stability of Grassland Communities to Altered Precipitation: A Meta-Analysis

    NASA Astrophysics Data System (ADS)

    Luo, Y.; Shi, Z.; Collins, S. L.; Knapp, A.; Pockman, W.; Smith, M.

    2014-12-01

    Species-specific responses to changes in precipitation can alter plant community structure and composition potentially altering ecosystem functioning. The latter will further feed back to climate change. Here, we synthesized results from more than 50 experimental studies that either increased or decreased precipitation in grasslands to assess productivity responses of different species and plant functional types (PFT) as well as changes in community structure. Our results showed that increased precipitation enhanced aboveground net primary production (ANPP) of the dominant PFT but had no effect on ANPP of the subordinate species. Similarly, decreased precipitation reduced ANPP of the dominant species but not that of subordinate species. Individual C3 species were highly responsive to alterations in precipitation, but C4 species were not. Altered precipitation had no effect on species richness, evenness or diversity. Overall, ANPP and belowground net primary productivity (BNPP) responded to both increased and reduced precipitation, but relative responses of ANPP to increased precipitation diminished with increasing mean annual precipitation (MAP) whereas the relative responses to reduced precipitation did not change with MAP. BNPP responses to altered precipitation did not vary with MAP. Our findings suggest that the dominant PFT in grasslands can be used as a proxy for community responses in ecosystem biogeochemical models. Further, grassland community composition and structure appear to be relatively stable in response to alterations in precipitation of the duration and magnitude encompassed by these experiments.

  9. Seedling responses to water pulses in shrubs with contrasting histories of grassland encroachment.

    PubMed

    Woods, Steven R; Archer, Steven R; Schwinning, Susan

    2014-01-01

    Woody plant encroachment into grasslands has occurred worldwide, but it is unclear why some tree and shrub species have been markedly more successful than others. For example, Prosopis velutina has proliferated in many grasslands of the Sonoran Desert in North America over the past century, while other shrub species with similar growth form and life history, such as Acacia greggii, have not. We conducted a glasshouse experiment to assess whether differences in early seedling development could help explain why one species and not the other came to dominate many Sonoran Desert grasslands. We established eight watering treatments mimicking a range of natural precipitation patterns and harvested seedlings 16 or 17 days after germination. A. greggii had nearly 7 times more seed mass than P. velutina, but P. velutina emerged earlier (by 3.0±0.3 d) and grew faster (by 8.7±0.5 mg d⁻¹). Shoot mass at harvest was higher in A. greggii (99±6 mg seedling⁻¹) than in P. velutina (74±2 mg seedling⁻¹), but there was no significant difference in root mass (54±3 and 49±2 mg seedling⁻¹, respectively). Taproot elongation was differentially sensitive to water supply: under the highest initial watering pulse, taproots were 52±19 mm longer in P. velutina than in A. greggii. Enhanced taproot elongation under favorable rainfall conditions could give nascent P. velutina seedlings growth and survivorship advantages by helping reduce competition with grasses and maintain contact with soil water during drought. Conversely, A. greggii's greater investment in mass per seed appeared to provide little return in early seedling growth. We suggest that such differences in recruitment traits and their sensitivities to environmental conditions may help explain ecological differences between species that are highly similar as adults and help identify pivotal drivers of shrub encroachment into grasslands. PMID:24475263

  10. Effects of drought on nitrogen turnover and abundances of ammonia-oxidizers in mountain grassland

    NASA Astrophysics Data System (ADS)

    Fuchslueger, L.; Kastl, E.-M.; Bauer, F.; Kienzl, S.; Hasibeder, R.; Ladreiter-Knauss, T.; Schmitt, M.; Bahn, M.; Schloter, M.; Richter, A.; Szukics, U.

    2014-11-01

    Future climate scenarios suggest an increased frequency of summer drought periods in the European Alpine Region. Drought can affect soil nitrogen (N) cycling, by altering N transformation rates, as well as the abundances of ammonia-oxidizing bacteria and archaea. However, the extent to which drought affects N cycling under in situ conditions is still controversial. The goal of this study was to analyse effects of drought on soil N turnover and ammonia-oxidizer abundances in soil without drought history. To this end we conducted rain-exclusion experiments at two differently managed mountain grassland sites, an annually mown and occasionally fertilized meadow and an abandoned grassland. Soils were sampled before, during and after drought and were analysed for potential gross rates of N mineralization, microbial uptake of inorganic N, nitrification, and the abundances of bacterial and archaeal ammonia-oxidizers based on gene copy numbers of the amoA gene (AOB and AOA, respectively). Drought induced different responses at the two studied sites. At the managed meadow drought increased NH4+ immobilization rates and NH4+ concentrations in the soil water solution, but led to a reduction of AOA abundance compared to controls. At the abandoned site gross nitrification and NO3- immobilization rates decreased during drought, while AOB and AOA abundances remained stable. Rewetting had only minor, short-term effects on the parameters that had been affected by drought. Seven weeks after the end of drought no differences to control plots could be detected. Thus, our findings demonstrated that in mountain grasslands drought had distinct transient effects on soil nitrogen cycling and ammonia-oxidizers, which could have been related to a niche differentiation of AOB and AOA with increasing NH4+ levels. However, the effect strength of drought was modulated by grassland management.

  11. Ammonia volatilization following dairy slurry application to a permanent grassland on a volcanic soil

    NASA Astrophysics Data System (ADS)

    Martínez-Lagos, J.; Salazar, F.; Alfaro, M.; Misselbrook, T.

    2013-12-01

    Agriculture is the largest source of ammonia (NH3) emission to the atmosphere. Within the agricultural sector, the application of slurry to grasslands as fertilizer is one of the main emission sources. This is a common practice in southern Chile, where most dairy production systems are grazing-based. In Chile, there are few published data of gaseous emissions following slurry application to grassland. The aim of this study was to evaluate NH3 volatilization following dairy slurry application to a permanent grassland on an Andosol soil. Ammonia volatilization was measured in four field experiments (winters of 2009 and 2011 and early and late springs of 2011) using a micrometeorological mass balance method with passive flux samplers following dairy slurry application at a target rate of 100 kg total N ha-1. The accumulated N loss was equivalent to 7, 8, 16 and 21% of the total N applied and 22, 34, 88 and 74% of total ammoniacal nitrogen (TAN) applied for winters 2009 and 2011, and early and late spring 2011, respectively. Ammonia emission rates were high immediately after application and declined rapidly with time, with more than 50% of the total emissions within the first 24 h. Losses were highly influenced by environmental conditions, increasing with temperature and lack of rainfall. Taking into consideration the low N losses via leaching and nitrous oxide emissions reported for the study area, results indicate that NH3 volatilization is the main pathway of N loss in fertilized grasslands of southern Chile. However, dairy slurry application could be an important source of nutrients, if applied at a suitable time, rate and using an appropriate technique, and if soil and climate conditions are taken into consideration. This could improve N use efficiency and reduce N losses to the wider environment.

  12. A new framework for evaluating the impacts of drought on net primary productivity of grassland.

    PubMed

    Lei, Tianjie; Wu, Jianjun; Li, Xiaohan; Geng, Guangpo; Shao, Changliang; Zhou, Hongkui; Wang, Qianfeng; Liu, Leizhen

    2015-12-01

    This paper presented a valuable framework for evaluating the impacts of droughts (single factor) on grassland ecosystems. This framework was defined as the quantitative magnitude of drought impact that unacceptable short-term and long-term effects on ecosystems may experience relative to the reference standard. Long-term effects on ecosystems may occur relative to the reference standard. Net primary productivity (NPP) was selected as the response indicator of drought to assess the quantitative impact of drought on Inner Mongolia grassland based on the Standardized Precipitation Index (SPI) and BIOME-BGC model. The framework consists of six main steps: 1) clearly defining drought scenarios, such as moderate, severe and extreme drought; 2) selecting an appropriate indicator of drought impact; 3) selecting an appropriate ecosystem model and verifying its capabilities, calibrating the bias and assessing the uncertainty; 4) assigning a level of unacceptable impact of drought on the indicator; 5) determining the response of the indicator to drought and normal weather state under global-change; and 6) investigating the unacceptable impact of drought at different spatial scales. We found NPP losses assessed using the new framework were more sensitive to drought and had higher precision than the long-term average method. Moreover, the total and average losses of NPP are different in different grassland types during the drought years from 1961-2009. NPP loss was significantly increased along a gradient of increasing drought levels. Meanwhile, NPP loss variation under the same drought level was different in different grassland types. The operational framework was particularly suited for integrative assessing the effects of different drought events and long-term droughts at multiple spatial scales, which provided essential insights for sciences and societies that must develop coping strategies for ecosystems for such events. PMID:26204052

  13. Effects of drought on nitrogen turnover and abundances of ammonia-oxidizers in mountain grassland

    NASA Astrophysics Data System (ADS)

    Fuchslueger, L.; Kastl, E.-M.; Bauer, F.; Kienzl, S.; Hasibeder, R.; Ladreiter-Knauss, T.; Schmitt, M.; Bahn, M.; Schloter, M.; Richter, A.; Szukics, U.

    2014-06-01

    Future climate scenarios suggest an increased frequency of summer drought periods in the European Alpine Region. Drought can affect soil nitrogen (N) cycling, by altering N transformation rates, as well as the abundances of ammonia-oxidizing bacteria and archaea. However, the extent to which drought affects N cycling under in situ conditions is still controversial. The goal of this study was to analyse effects of drought on soil N turnover and ammonia-oxidizer abundances. To this end we conducted a rain-exclusion experiment at two differently managed mountain grassland sites, an annually mown and occasionally fertilized meadow and an abandoned grassland. Soils were sampled before, during and after drought and were analysed for gross rates of N mineralization, microbial uptake of inorganic N, nitrification, and the abundances of bacterial and archaeal ammonia oxidizers based on gene copy numbers of the amoA gene (AOB and AOA, respectively). Our results showed that the response to drought differed between the two sites. Effects were stronger at the managed meadow, where NH4+ immobilization rates increased and AOA abundances decreased. At the abandoned site gross nitrification and NO3- immobilization rates decreased during drought, while neither AOB, nor AOA abundances were affected. The different responses of the two sites to drought were likely related to site specific differences, such as soil organic matter content, nitrogen pools and absolute soil water content, resulting from differences in land-management. At both sites rewetting after drought had only minor short-term effects on the parameters that had been affected by drought, and seven weeks after the drought no effects of drought were detectable anymore. Thus, our findings indicate that drought can have distinct transient effects on soil nitrogen cycling and ammonia-oxidizer abundances in mountain grasslands and that the effect strength could be modulated by grassland management.

  14. Grassland-shrubland state transitions in arid lands: Competition matters

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Background/Question/Methods: State transition from grassland to shrubland is synonymous with desertification in many dryland systems. The classic desertification model emphasizes abiotic feedbacks that modify the physical environment in ways that promote shrub proliferation and impede grass survival...

  15. Controls upon microbial accessibility to soil organic matter following woody plant encroachment into grasslands

    NASA Astrophysics Data System (ADS)

    Creamer, C. A.; Boutton, T. W.; Filley, T. R.

    2009-12-01

    Woody plant encroachment (WPE) into savannas and grasslands is a global phenomenon that alters soil organic matter (SOM) dynamics through changes in litter quality and quantity, soil structure, microbial ecology, and soil hydrology. To elucidate the controls upon microbial accessibility to SOM, bulk soils from a chronosequence of progressive WPE into native grasslands at the Texas A&M Agricultural Experimental Station La Copita Research Area were incubated for one year. The quantity and stable carbon isotope composition of respired CO2, plant biopolymer chemistry in SOM, and microbial community structure were tracked. Respiration rates declined steadily over the course of the experiment with 15-25% of the total CO2 respired released in the first month of incubation. Between 8 and 18% of the total carbon was mineralized to CO2 throughout the incubation. After day 84 a significantly (p < 0.05) greater portion of carbon was mineralized from soils of older woody clusters (34-86 years) than from soils of younger clusters (14-23 years) and the native grassland. Approximately 80% of patterns seen in cumulative CO2 loss could be explained by the proportions of macro- and micro-aggregates within each soil, suggesting soil structure is a major controlling factor of respiration rates. Despite documented carbon accrual within La Copita soils due to WPE, we observed no evidence of enhanced carbon stabilization in these respiration experiments. In fact, a greater proportion of total carbon was lost from the soil of mature woody stands than from young stands, suggesting carbon accumulation observed with WPE may be due to greater input rates or microbial dynamics not captured in the laboratory incubation. A cluster approximately 34 years in age represents a transition point in WPE where respiration dynamics become distinct between grassland and wooded elements. By day 84 of the incubation CO2 respired from all soils was depleted with respect to bulk SOM (1.5 to 5‰) and this

  16. [Impacts of Ochotona pallasi disturbance on alpine grassland community characteristics].

    PubMed

    Zhao, Guo-qin; Li, Guang-yong; Ma, Wen-hu; Zhao, Dian-zhi; Li, Xiao-yan

    2013-08-01

    Plateau pika is the main fossorial mammal in the alpine grassland in Qinghai Lake Watershed of Northwest China. Based on the field investigation data from 18 alpine grassland quadrats in the Watershed, and by using redundancy analysis (RDA) and the surface fitting offered by 'R-Vegan' , the disturbance intensity of plateau pika (Ochotona pallasi) was classified as four levels. In order to explore the impacts of plateau pika disturbance on the alpine grassland ecosystem and its grazing quality, the community characteristics under different disturbance intensities by plateau pika were analyzed, and a conceptual model about the alpine grassland community succession was proposed. The results showed that with the increase of the disturbance intensity, the dominant species changed from Juncus roemerianus to Poa pratensis and Laux maritima. When the disturbance was small, the community had high quantitative values of coverage, aboveground biomass, biodiversity, and species richness, but the proportion of weeds was also high. When the disturbance was large, the quantitative values were the lowest, while the proportion of weeds was the highest. When the disturbance was moderate, the community had relatively high quantitative values, and the proportion of grasses and sedges was the highest. It was concluded that the community' s characteristic values under low plateau pika disturbance intensity were high but the grazing quality was low, while high disturbance intensity resulted in the grassland degradation. Therefore, the disturbance intensity in the threshold could maintain the stability of alpine grassland ecosystem and improve its grazing quality. PMID:24380328

  17. Innovative grassland management systems for environmental and livelihood benefits

    PubMed Central

    Kemp, David R.; Guodong, Han; Xiangyang, Hou; Michalk, David L.; Fujiang, Hou; Jianping, Wu; Yingjun, Zhang

    2013-01-01

    Grasslands occupy 40% of the world’s land surface (excluding Antarctica and Greenland) and support diverse groups, from traditional extensive nomadic to intense livestock-production systems. Population pressures mean that many of these grasslands are in a degraded state, particularly in less-productive areas of developing countries, affecting not only productivity but also vital environmental services such as hydrology, biodiversity, and carbon cycles; livestock condition is often poor and household incomes are at or below poverty levels. The challenge is to optimize management practices that result in “win-win” outcomes for grasslands, the environment, and households. A case study is discussed from northwestern China, where it has been possible to reduce animal numbers considerably by using an energy-balance/market-based approach while improving household incomes, providing conditions within which grassland recovery is possible. This bottom-up approach was supported by informing and working with the six layers of government in China to build appropriate policies. Further policy implications are considered. Additional gains in grassland rehabilitation could be fostered through targeted environmental payment schemes. Other aspects of the livestock production system that can be modified are discussed. This work built a strategy that has implications for many other grassland areas around the world where common problems apply. PMID:23671092

  18. Innovative grassland management systems for environmental and livelihood benefits.

    PubMed

    Kemp, David R; Guodong, Han; Xiangyang, Hou; Michalk, David L; Fujiang, Hou; Jianping, Wu; Yingjun, Zhang

    2013-05-21

    Grasslands occupy 40% of the world's land surface (excluding Antarctica and Greenland) and support diverse groups, from traditional extensive nomadic to intense livestock-production systems. Population pressures mean that many of these grasslands are in a degraded state, particularly in less-productive areas of developing countries, affecting not only productivity but also vital environmental services such as hydrology, biodiversity, and carbon cycles; livestock condition is often poor and household incomes are at or below poverty levels. The challenge is to optimize management practices that result in "win-win" outcomes for grasslands, the environment, and households. A case study is discussed from northwestern China, where it has been possible to reduce animal numbers considerably by using an energy-balance/market-based approach while improving household incomes, providing conditions within which grassland recovery is possible. This bottom-up approach was supported by informing and working with the six layers of government in China to build appropriate policies. Further policy implications are considered. Additional gains in grassland rehabilitation could be fostered through targeted environmental payment schemes. Other aspects of the livestock production system that can be modified are discussed. This work built a strategy that has implications for many other grassland areas around the world where common problems apply. PMID:23671092

  19. Disentangling the response of forest and grassland energy exchange to heatwaves under idealized land-atmosphere coupling

    NASA Astrophysics Data System (ADS)

    van Heerwaarden, C. C.; Teuling, A. J.

    2014-04-01

    This study investigates the difference in land-atmosphere interactions between grassland and forest during typical heat wave conditions in order to understand the controversial results of Teuling et al. (2010) (T10, hereafter), who have found the systematic occurrence of higher sensible heat fluxes over forest than over grassland during heat wave conditions. With a simple, but accurate coupled land-atmosphere model, we are able to reproduce the findings of T10 for both normal summer and heat wave conditions, and to carefully explore the sensitivity of the coupled land-atmosphere system to changes in incoming radiation and early-morning temperature. Our results emphasize the importance of fast processes during the onset of heat waves, since we are able to explain the results of T10 without having to take into account changes in soil moisture. In order to disentangle the contribution of differences in several static and dynamic properties between forest and grassland, we have performed an experiment in which new land use types are created that are equal to grassland, but with one of its properties replaced by that of forest. From these, we conclude that the closure of stomata in the presence of dry air is by far the most important process in creating the different behavior of grassland and forest during the onset of a heat wave. However, we conclude that for a full explanation of the results of T10 also the other properties (albedo, roughness and the ratio of minimum stomatal resistance to leaf-area index) play an important, but indirect role; their influences mainly consist of strengthening the feedback that leads to the closure of the stomata by providing more energy that can be converted into sensible heat. The model experiment also confirms that, in line with the larger sensible heat flux, higher atmospheric temperatures occur over forest.

  20. Soil-occupancy effects of invasive and native grassland plant species on composition and diversity of mycorrhizal associations

    USGS Publications Warehouse

    Jordan, Nicholas R.; Aldrich-Wolfe, Laura; Huerd, Sheri C.; Larson, Diane L.; Muehlbauer, Gary

    2012-01-01

    Diversified grasslands that contain native plant species can produce biofuels, support sustainable grazing systems, and produce other ecosystem services. However, ecosystem service production can be disrupted by invasion of exotic perennial plants, and these plants can have soil-microbial “legacies” that may interfere with establishment and maintenance of diversified grasslands even after effective management of the invasive species. The nature of such legacies is not well understood, but may involve suppression of mutualisms between native species and soil microbes. In this study, we tested the hypotheses that legacy effects of invasive species change colonization rates, diversity, and composition of arbuscular-mycorrhizal fungi (AMF) associated with seedlings of co-occurring invasive and native grassland species. In a glasshouse, experimental soils were conditioned by cultivating three invasive grassland perennials, three native grassland perennials, and a native perennial mixture. Each was grown separately through three cycles of growth, after which we used T-RFLP analysis to characterize AMF associations of seedlings of six native perennial and six invasive perennial species grown in these soils. Legacy effects of soil conditioning by invasive species did not affect AMF richness in seedling roots, but did affect AMF colonization rates and the taxonomic composition of mycorrhizal associations in seedling roots. Moreover, native species were more heavily colonized by AMF and roots of native species had greater AMF richness (number of AMF operational taxonomic units per seedling) than did invasive species. The invasive species used to condition soil in this experiment have been shown to have legacy effects on biomass of native seedlings, reducing their growth in this and a previous similar experiment. Therefore, our results suggest that successful plant invaders can have legacies that affect soil-microbial associations of native plants and that these effects

  1. Effects of smectite on the oil-expulsion efficiency of the Kreyenhagen Shale, San Joaquin Basin, California, based on hydrous-pyrolysis experiments

    USGS Publications Warehouse

    Lewan, Michael D.; Dolan, Michael P.; Curtis, John B.

    2014-01-01

    The amount of oil that maturing source rocks expel is expressed as their expulsion efficiency, which is usually stated in milligrams of expelled oil per gram of original total organic carbon (TOCO). Oil-expulsion efficiency can be determined by heating thermally immature source rocks in the presence of liquid water (i.e., hydrous pyrolysis) at temperatures between 350°C and 365°C for 72 hr. This pyrolysis method generates oil that is compositionally similar to natural crude oil and expels it by processes operative in the subsurface. Consequently, hydrous pyrolysis provides a means to determine oil-expulsion efficiencies and the rock properties that influence them. Smectite in source rocks has previously been considered to promote oil generation and expulsion and is the focus of this hydrous-pyrolysis study involving a representative sample of smectite-rich source rock from the Eocene Kreyenhagen Shale in the San Joaquin Basin of California. Smectite is the major clay mineral (31 wt. %) in this thermally immature sample, which contains 9.4 wt. % total organic carbon (TOC) comprised of type II kerogen. Compared to other immature source rocks that lack smectite as their major clay mineral, the expulsion efficiency of the Kreyenhagen Shale was significantly lower. The expulsion efficiency of the Kreyenhagen whole rock was reduced 88% compared to that of its isolated kerogen. This significant reduction is attributed to bitumen impregnating the smectite interlayers in addition to the rock matrix. Within the interlayers, much of the bitumen is converted to pyrobitumen through crosslinking instead of oil through thermal cracking. As a result, smectite does not promote oil generation but inhibits it. Bitumen impregnation of the rock matrix and smectite interlayers results in the rock pore system changing from water wet to bitumen wet. This change prevents potassium ion (K+) transfer and dissolution and precipitation reactions needed for the conversion of smectite to

  2. Exotic plant invasion alters nitrogen dynamics in an arid grassland

    USGS Publications Warehouse

    Evans, R.D.; Rimer, R.; Sperry, L.; Belnap, J.

    2001-01-01

    The introduction of nonnative plant species may decrease ecosystem stability by altering the availability of nitrogen (N) for plant growth. Invasive species can impact N availability by changing litter quantity and quality, rates of N2-fixation, or rates of N loss. We quantified the effects of invasion by the annual grass Bromus tectorum on N cycling in an arid grassland on the Colorado Plateau (USA). The invasion occurred in 1994 in two community types in an undisturbed grassland. This natural experiment allowed us to measure the immediate responses following invasion without the confounding effects of previous disturbance. Litter biomass and the C:N and lignin:N ratios were measured to determine the effects on litter dynamics. Long-term soil incubations (415 d) were used to measure potential microbial respiration and net N mineralization. Plant-available N was quantified for two years in situ with ion-exchange resin bags, and potential changes in rates of gaseous N loss were estimated by measuring denitrification enzyme activity. Bromus invasion significantly increased litter biomass, and Bromus litter had significantly greater C:N and lignin:N ratios than did native species. The change in litter quantity and chemistry decreased potential rates of net N mineralization in sites with Bromus by decreasing nitrogen available for microbial activity. Inorganic N was 50% lower on Hilaria sites with Bromus during the spring of 1997, but no differences were observed during 1998. The contrasting differences between years are likely due to moisture availability; spring precipitation was 15% greater than average during 1997, but 52% below average during spring of 1998. Bromus may cause a short-term decrease in N loss by decreasing substrate availability and denitrification enzyme activity, but N loss is likely to be greater in invaded sites in the long term because of increased fire frequency and greater N volatilization during fire. We hypothesize that the introduction of

  3. Modelling susceptibility of grassland soil to macropore flow

    NASA Astrophysics Data System (ADS)

    Alaoui, Abdallah

    2015-06-01

    Investigating preferential flow, including macropore flow, is crucial to predicting and preventing point sources of contamination in soil, for example in the vicinity of pumping wells. With a view to advancing groundwater protection, this study aimed (i) to quantify the strength of macropore flow in four representative natural grassland soils on the Swiss plateau, and (ii) to define the parameters that significantly control macropore flow in grassland soil. For each soil type we selected three measurement points on which three successive irrigation experiments were carried out, resulting in a total of 36 irrigations. The strength of macropore flow, parameterized as the cumulated water volume flowing from macropores at a depth of 1 m in response to an irrigation of 60 mm h-1 intensity and 1 h duration, was simulated using the dual-permeability MACRO model. The model calibration was based on the key soil parameters and fine measurements of water content at different depths. Modelling results indicate high performance of macropore flow in all investigated soil types except in gleysols. The volume of water that flowed from macropores and was hence expected to reach groundwater varied between 81% and 94% in brown soils, 59% and 67% in para-brown soils, 43% and 56% in acid brown soils, and 22% and 35% in gleysols. These results show that spreading pesticides and herbicides in pumping well protection zones poses a high risk of contamination and must be strictly prohibited. We also found that organic carbon content was not correlated with the strength of macropore flow, probably due to its very weak variation in our study, while saturated water content showed a negative correlation with macropore flow. The correlation between saturated hydraulic conductivity (Ks) and macropore flow was negative as well, but weak. Macropore flow appears to be controlled by the interaction between the bulk density of the uppermost topsoil layer (0-0.10 m) and the macroporosity of the soil

  4. Litter quality, decomposition rates and saprotrophic mycoflora in Fallopia japonica (Houtt.) Ronse Decraene and in adjacent native grassland vegetation

    NASA Astrophysics Data System (ADS)

    Mincheva, T.; Barni, E.; Varese, G. C.; Brusa, G.; Cerabolini, B.; Siniscalco, C.

    2014-01-01

    Fallopia japonica succeeds in invading different ecosystems likely because of its huge biomass production. This biomass is characterized by low nutritional quality and low decomposition rates but knowledge on whether these features are correlated to microbial decomposers is still lacking. The aims of this work were: i) to determine litter decomposition rates of native grassland vegetation and F. japonica under different conditions in a year-round experiment; ii) to evaluate litter quality and/or site effect on the decomposition of the invader and native vegetation and iii) to characterize mycoflora isolated from F. japonica and native vegetation litter. The results showed that F. japonica litter decomposes 3-4 times slower than that of native grassland, mainly due to its low N content and consequently high C/N ratio both in leaves and stems. As decomposition proceeds C/N in F. japonica litter decreases to values approaching those of the grassland litter. Site had no effect on the decomposition rates of F. japonica and grassland litter. Total fungal load and composition differed between F. japonica and native litter, and also varied across sites. These results indicate that the successful invasive plant F. japonica affects the structure and functions of the invaded ecosystem through a huge production of low quality, slow-decomposing litter that selects saprotrophic fungi.

  5. Recommendations on the use of prescribed burning practices in grassland conservation - An evidence-based study from Hungary

    NASA Astrophysics Data System (ADS)

    Tóthmérész, Béla; Valkó, Orsolya; Török, Péter; Végvári, Zsolt; Deák, Balázs

    2015-04-01

    Fire as a natural disturbance has been present in most European grasslands. In parallel controlled use of burning was an important part of the traditional landscape management for millennia. It was used to reduce litter and suppress woody vegetation as well as to maintain open landscapes suitable for farming. Recently, human activities have a considerable impact on natural fire regimes through habitat fragmentation, cessation of traditional grassland management and climate change. Nowadays the majority of human-ignited fires are uncontrolled burnings and arson, which have serious negative impacts on human life, property and can be detrimental also from the nature conservation point of view. Despite fire was widely applied in the past and the considerable extension and frequency of current grassland fires, the impact of fire on the grassland biodiversity is still scarcely documented in Europe. The aim of our study was to gather practical knowledge and experiences from Hungary concerning the effects of fire on grasslands. To fulfil this aim we sent questionnaires to experts from Hungarian national park directorates to gather unpublished data and field observations concerning the effects of burning on grasslands. Based on the answers for the questionnaires fire regularly occur in almost every grassland types in Hungary. We found that effects of fire are habitat-specific. One hand uncontrolled burning and arson have serious detrimental impacts on many endangered species (ground-dwelling birds, such as Asio flammeus, Tringa totanus and Vanellus vanellus; or lizards, such as Ablepharus kitaibelii). On the other hand in several cases fire has a positive effect on the habitat structure and favours species of high nature conservation interest (plant species, such as Adonis volgensis, Chamaecytisus supinus and Pulsatilla grandis; butterflies, such as Euphydryas aurinia; bird species such as Circus aeruginosus and Larus cachinnans). Our results suggest that even uncontrolled

  6. Impact of Reduced Diurnal Temperature Range (DTR) on Grassland Mesocosms

    NASA Astrophysics Data System (ADS)

    Gregg, J. W.; Phillips, C.; Wilson, J.

    2010-12-01

    treatments compared to AMB. Lupinus albicaulus, the lone N-fixing perennial forb, exhibited low (48%) survival for the ambient treatment in the N-rich grassland soils after one year, but even lower survival (8% and 11%) for the SYM and ASYM treatments. There were no differences in soil N availability between treatments, so reduced survival for this and other late spring emerging species appeared to be due to substantially reduced growing season due to the earlier senescence for the warmer treatments. These results suggest that species that take advantage of enhanced fall growth conditions are likely to have a competitive advantage as grasslands become warmer. Overall, our results show no differences in assimilation, respiration, NEP, phenology, or species composition/diversity for ASYM compared to SYM warming treatments. Future research should determine if these lack of treatment effects persist for reverse-ASYM treatments that experience an increase in DTR where greatest temperature increase occurs at the hottest time of day. It will also be important to determine the robustness of these results for woody species or higher latitudes where winter dormancy would play an important role for altering season length.

  7. The sensitivity of carbon exchanges in Great Plains grasslands to precipitation variability

    NASA Astrophysics Data System (ADS)

    Petrie, M. D.; Brunsell, N. A.; Vargas, R.; Collins, S. L.; Flanagan, L. B.; Hanan, N. P.; Litvak, M. E.; Suyker, A. E.

    2016-02-01

    In the Great Plains, grassland carbon dynamics differ across broad gradients of precipitation and temperature, yet finer-scale variation in these variables may also affect grassland processes. Despite the importance of grasslands, there is little information on how fine-scale relationships compare between them regionally. We compared grassland C exchanges, energy partitioning and precipitation variability in eight sites in the eastern and western Great Plains using eddy covariance and meteorological data. During our study, both eastern and western grasslands varied between an average net carbon sink and a net source. Eastern grasslands had a moderate vapor pressure deficit (VPD = 0.95 kPa) and high growing season gross primary productivity (GPP = 1010 ± 218 g C m-2 yr-1). Western grasslands had a growing season with higher VPD (1.43 kPa) and lower GPP (360 ± 127 g C m-2 yr-1). Western grasslands were sensitive to precipitation at daily timescales, whereas eastern grasslands were sensitive at monthly and seasonal timescales. Our results support the expectation that C exchanges in these grasslands differ as a result of varying precipitation regimes. Because eastern grasslands are less influenced by short-term variability in rainfall than western grasslands, the effects of precipitation change are likely to be more predictable in eastern grasslands because the timescales of variability that must be resolved are relatively longer. We postulate increasing regional heterogeneity in grassland C exchanges in the Great Plains in coming decades.

  8. Grasslands changes in the Northern Songnen Plain, China during 1954-2000.

    PubMed

    Huang, Fang; Wang, Ping; Zhang, Jingjing

    2012-04-01

    Songnen Plain in Northeast China is one of the most significantly altered biological hotspots on Earth. Based on the information from integrated topographic maps, Landsat MSS, TM/ETM images and geographic information systems, grassland cover change, grassland fragmentation, agricultural reclamation, and saline-alkaline wasteland expansion in the region were investigated for the period of 1954 to 2000. The results showed that the native grassland decreased by 44.6 × 10(4) ha and moderate density grassland decreased from 78.3 × 10(4) to 20.3 × 10(4) ha. Calculated from change dynamic model, the annual decrease rate of grassland was 1.1%.The distribution center of the grasslands illustrated a trend of shifting southeastward. The distance between centroids of grassland was 10.1 km. The numbers of grassland patch increased by 1,378, while the patch size of grasslands declined. Grassland experienced substantial clearing and fragmentation. The decreased grassland was converted into cropland, wetland, and saline-alkaline wasteland. The loss and degradation of grasslands was closely related to regional climate during the past 47 years. Population and livestock number increased significantly as grassland quality decreased. Intensive human activities including irrational reclamation and overgrazing may have accelerated the degradation of grasslands. PMID:21614622

  9. Microscale Topographic Influence on Grassland Primary Productivity on Semiarid Hillslopes

    NASA Astrophysics Data System (ADS)

    Travis, Jeffrey Todd

    Understanding the distribution of plant productivity is vital for understanding the spatial variability of ecosystem functions. This study evaluates microtopographic controls (1m-12m) on plant productivity on three rolling hills in Sedgwick Natural Reserve, located in south-central California. Specifically I evaluate the relationship between topographic metrics and plant biomass production through space and time. Biomass was measured using destructive harvests and seasonal Airborne Visible Infrared Imaging Spectrometer (AVIRIS) data. Eighty-three 1x0.5m2 quadrats of aboveground plant matter at peak biomass (ANPP) were harvested for the 2012 growing season. For the 2009 growing season, AVIRIS derived Normalized Difference Vegetation Index (NDVI) was used to estimate biomass at roughly monthly intervals from March to August. I evaluate whether seasonal changes in growing degree days (GDD) was a better predictor of plant phenological events than cumulative days since first soil moisture increase. To characterize topography, I used a 1m resolution digital elevation model derived from terrestrial lidar data to calculate curvature, aspect, and the Compound Topographic Index (CTI) - an index that integrates the flow accumulation area and slope. Using GDD, I found that ecosystem productivity was not temperature limited early in the growing season. Using webcam images I was able to remotely monitor phenological events quantitatively, but was not able to calculate NDVI because I lacked appropriate spectral bands. Plants growing on north facing slopes consistently had higher ANPP than those on south facing slopes, due to lower temperatures, hence greater preservation of soil moisture. No correlation was found between CTI or curvature and ANPP across the 83 sampled points in 2012, potentially because it was a dry year and there was limited water redistribution to lower positions in the landscape. Although a relationship between topography and soil moisture is probably valid

  10. Sustaining multiple ecosystem functions in grassland communities requires higher biodiversity.

    PubMed

    Zavaleta, Erika S; Pasari, Jae R; Hulvey, Kristin B; Tilman, G David

    2010-01-26

    Society places value on the multiple functions of ecosystems from soil fertility to erosion control to wildlife-carrying capacity, and these functions are potentially threatened by ongoing biodiversity losses. Recent empirically based models using individual species' traits suggest that higher species richness is required to provide multiple ecosystem functions. However, no study to date has analyzed the observed functionality of communities of interacting species over multiple temporal scales to assess the relationship between biodiversity and multifunctionality. We use data from the longest-running biodiversity-functioning field experiment to date to test how species diversity affects the ability of grassland ecosystems to provide threshold levels of up to eight ecosystem functions simultaneously. Across years and every combination of ecosystem functions, minimum-required species richness consistently increases with the number of functions considered. Moreover, tradeoffs between functions and variability among years prevent any one community type from providing high levels of multiple functions, regardless of its diversity. Sustained multifunctionality, therefore, likely requires both higher species richness than single ecosystem functionality and a diversity of species assemblages across the landscape. PMID:20080690

  11. Application of relaxed eddy accumulation (REA) on managed grassland

    NASA Astrophysics Data System (ADS)

    Riederer, M.; Hübner, J.; Ruppert, J.; Brand, W. A.; Foken, T.

    2014-05-01

    Relaxed eddy accumulation is applied for measuring fluxes of trace gases for which there is a lack of sensors fast enough in their resolution for eddy-covariance. On managed grasslands, the length of time between management events and the application of relaxed eddy accumulation has an essential influence on the determination of the proportionality factor b and thereby on the resulting flux. In this study this effect is discussed for the first time. Also, scalar similarity between proxy scalars and scalars of interest is affected until the ecosystem has completely recovered. Against this background, CO2 fluxes were continuously measured and 13CO2 isofluxes were determined with a high measurement precision on two representative days in summer 2010. This enabled the evaluation of the 13CO2 flux portion of the entire CO2 flux, in order to estimate potential influences on tracer experiments in ecosystem sciences and to compare a common method for the partitioning of the net ecosystem exchange into assimilation and respiration based on temperature and light response with an isotopic approach directly based on the isotope discrimination of the biosphere.

  12. Computer Literacy of California's Sixth and Twelfth Grade Students. California Assessment Program.

    ERIC Educational Resources Information Center

    California State Dept. of Education, Sacramento.

    As a baseline measurement of what is being learned about computers in California, a study, originally reported in "Student Achievement in California Schools: 1982-83 Annual Report," investigated the knowledge, attitudes, and experiences of a representative sample of 6th and 12th graders. The survey was developed by experts on computer technology…

  13. California Dreaming: The Past, Present, and Future of Continuing and Higher Education in California

    ERIC Educational Resources Information Center

    Matkin, Gary W.

    2012-01-01

    In this article, Gary Matkin, Dean of Continuing Education, Distance Learning, and Summer Session at the University of California, Irvine and long-time member of UPCEA, talks about his experience with higher and continuing education in California. The situation of public universities has changed considerably, and his 43 years as an undergraduate,…

  14. Estimation of nitrous oxide emissions from US grasslands

    SciTech Connect

    Mummey, D.L.; Smith, J.L.; Bluhm, G.

    2000-02-01

    Nitrous oxide (N{sub 2}O) emissions from temperate grasslands are poorly quantified and may be an important part of the atmospheric N{sub 2}O budget. In this study N{sub 2}O emissions were simulated for 1,052 grassland sites in the US using the NGAS model of Parton and others (1996) coupled with an organic matter decomposition model. N{sub 2}O flux was calculated for each site using soil and land use data obtained from the National Resource Inventory (NRI) database and weather data obtained from NASA. The estimates were regionalized based upon temperature and moisture isotherms. Annual N{sub 2}O emissions for each region were based on the grassland area of each region and the mean estimated annual N{sub 2}O flux from NRI grassland sites in the region. The regional fluxes ranged from 0.18 to 1.02 kg N{sub 2}O N/ha/yr with the mean flux for all regions being 0.29 kg N{sub 2}O N/ha/yr. Even though fluxes from the western regions were relatively low, these regions made the largest contribution to total emissions due to their large grassland area. Total US grassland N{sub 2}O emissions were estimated to be about 67 Gg N{sub 2}O N/yr. Emissions from the Great Plains states, which contain the largest expanse of natural grassland in the US, were estimated to average 0.24 kg N{sub 2}O N/ha/yr. Using the annual flux estimate for the temperate Great Plains, the authors estimate that temperate grasslands worldwide may potentially produce 0.27 Tg N{sub 2}O N/yr. Even though the estimate for global temperate grassland N{sub 2}O emissions is less than published estimates for other major temperate grasslands are a significant part of both United States and global atmospheric N{sub 2}O budgets. This study demonstrates the utility of models for regional N{sub 2}O budgets. This study demonstrates the utility of models for regional N{sub 2}O flux estimation although additional data from carefully designed field studies is needed to further validate model results.

  15. Response of grassland ecosystems to prolonged soil moisture deficit

    NASA Astrophysics Data System (ADS)

    Ross, Morgan A.; Ponce-Campos, Guillermo E.; Barnes, Mallory L.; Hottenstein, John D.; Moran, M. Susan

    2014-05-01

    Soil moisture is commonly used for predictions of plant response and productivity. Climate change is predicted to cause an increase in the frequency and duration of droughts over the next century, which will result in prolonged periods of below-normal soil moisture. This, in turn, is expected to impact regional plant production, erosion and air quality. In fact, the number of consecutive months of soil moisture content below the drought-period mean has recently been linked to regional tree and shrub mortality in the southwest United States. This study investigated the effects of extended periods of below average soil moisture on the response of grassland ANPP to precipitation. Grassland ecosystems were selected for this study because of their ecological sensitivity to precipitation patterns. It has been postulated that the quick ecological response of grasslands to droughts can provide insight to large scale functional responses of regions to predicted climate change. The study sites included 21 grassland biomes throughout arid-to-humid climates in the United States with continuous surface soil moisture records for 2-13 years during the drought period from 2000-2013. Annual net primary production (ANPP) was estimated from the 13-year record of NASA MODIS Enhanced Vegetation Index extracted for each site. Prolonged soil moisture deficit was defined as a period of at least 10 consecutive months during which soil moisture was below the drought-period mean. ANPP was monitored before, during and after prolonged soil moisture deficit to quantify shifts in the functional response of grasslands to precipitation, and in some cases, new species assemblages that included invasive species. Preliminary results indicated that when altered climatic conditions on grasslands led to an increase in the duration of soil water deficit, then the precipitation-to-ANPP relation became non-linear. Non-linearity was associated with extreme grassland dieback and changes in the historic

  16. Controls on microbial accessibility to soil organic carbon following woody plant encroachment into grasslands

    NASA Astrophysics Data System (ADS)

    Creamer, Courtney; Boutton, Thomas; Olk, Dan; Filley, Timothy

    2010-05-01

    Woody plant encroachment (WPE) into savannas and grasslands is a global phenomenon that alters soil organic carbon (SOC) dynamics through changes in litter quality and quantity, soil structure, microbial ecology, and hydrology. To elucidate the controls on microbial accessibility to SOC, bulk soils from a chronosequence of progressive WPE into native grasslands at the Texas Agrilife La Copita Research Area were incubated for one year. The quantity and stable carbon isotope composition of respired CO2, and plant biopolymer chemistry in SOC were tracked. Respiration rates declined exponentially over the course of the experiment with 15-25% of the total CO2 respired released in the first month of incubation. Between 8 and 18% of the total SOC was mineralized to CO2 throughout the incubation. After day 84 a significantly (p<0.05) greater portion of SOC was mineralized from soils of older woody clusters (34-86 years) than from soils of younger woody clusters (14-23 years) and the native grassland. Invading woody stands of ≃≥35 years of age represent a transition point in WPE where respiration dynamics become distinct in wooded elements compared to grasslands; this distinction has been previously observed through changes in belowground SOC accrual, C input chemistry, and mycorrhizal productivity. Despite documented SOC accrual following WPE at La Copita, we observed no evidence of enhanced SOC stabilization in these respiration experiments. In fact, a greater proportion of total SOC was lost from the soil of mature woody stands than from young stands, suggesting SOC accumulation observed with WPE may be due to greater input rates or microbial dynamics not captured in the laboratory incubation. Compound-specific analyses indicated there was a significant (p<0.05) loss of C from carbohydrates, amino acids, and amino sugars during the incubation. Amino nitrogen tended to become more concentrated during the incubation, although the trend was not significant. Relatively

  17. Managing for Biodiversity and Livestock: A Scale-Dependent Approach for Promoting Vegetation Heterogenity in Western Great Plains Grasslands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grasslands with heterogeneous vegetation structure and composition support a greater number of plant and animal species. To increase habitat diversity for wildlife, improve overall grassland health, and help recover declining grassland bird populations, management strategies should maintain or maxim...

  18. Locally rare species influence grassland ecosystem multifunctionality.

    PubMed

    Soliveres, Santiago; Manning, Peter; Prati, Daniel; Gossner, Martin M; Alt, Fabian; Arndt, Hartmut; Baumgartner, Vanessa; Binkenstein, Julia; Birkhofer, Klaus; Blaser, Stefan; Blüthgen, Nico; Boch, Steffen; Böhm, Stefan; Börschig, Carmen; Buscot, Francois; Diekötter, Tim; Heinze, Johannes; Hölzel, Norbert; Jung, Kirsten; Klaus, Valentin H; Klein, Alexandra-Maria; Kleinebecker, Till; Klemmer, Sandra; Krauss, Jochen; Lange, Markus; Morris, E Kathryn; Müller, Jörg; Oelmann, Yvonne; Overmann, Jörg; Pašalić, Esther; Renner, Swen C; Rillig, Matthias C; Schaefer, H Martin; Schloter, Michael; Schmitt, Barbara; Schöning, Ingo; Schrumpf, Marion; Sikorski, Johannes; Socher, Stephanie A; Solly, Emily F; Sonnemann, Ilja; Sorkau, Elisabeth; Steckel, Juliane; Steffan-Dewenter, Ingolf; Stempfhuber, Barbara; Tschapka, Marco; Türke, Manfred; Venter, Paul; Weiner, Christiane N; Weisser, Wolfgang W; Werner, Michael; Westphal, Catrin; Wilcke, Wolfgang; Wolters, Volkmar; Wubet, Tesfaye; Wurst, Susanne; Fischer, Markus; Allan, Eric

    2016-05-19

    Species diversity promotes the delivery of multiple ecosystem functions (multifunctionality). However, the relative functional importance of rare and common species in driving the biodiversity-multifunctionality relationship remains unknown. We studied the relationship between the diversity of rare and common species (according to their local abundances and across nine different trophic groups), and multifunctionality indices derived from 14 ecosystem functions on 150 grasslands across a land-use intensity (LUI) gradient. The diversity of above- and below-ground rare species had opposite effects, with rare above-ground species being associated with high levels of multifunctionality, probably because their effects on different functions did not trade off against each other. Conversely, common species were only related to average, not high, levels of multifunctionality, and their functional effects declined with LUI. Apart from the community-level effects of diversity, we found significant positive associations between the abundance of individual species and multifunctionality in 6% of the species tested. Species-specific functional effects were best predicted by their response to LUI: species that declined in abundance with land use intensification were those associated with higher levels of multifunctionality. Our results highlight the importance of rare species for ecosystem multifunctionality and help guiding future conservation priorities. PMID:27114572

  19. Allopolyploidy, diversification, and the Miocene grassland expansion

    PubMed Central

    Estep, Matt C.; McKain, Michael R.; Vela Diaz, Dilys; Zhong, Jinshun; Hodge, John G.; Hodkinson, Trevor R.; Layton, Daniel J.; Malcomber, Simon T.; Pasquet, Rémy; Kellogg, Elizabeth A.

    2014-01-01

    The role of polyploidy, particularly allopolyploidy, in plant diversification is a subject of debate. Whole-genome duplications precede the origins of many major clades (e.g., angiosperms, Brassicaceae, Poaceae), suggesting that polyploidy drives diversification. However, theoretical arguments and empirical studies suggest that polyploid lineages may actually have lower speciation rates and higher extinction rates than diploid lineages. We focus here on the grass tribe Andropogoneae, an economically and ecologically important group of C4 species with a high frequency of polyploids. A phylogeny was constructed for ca. 10% of the species of the clade, based on sequences of four concatenated low-copy nuclear loci. Genetic allopolyploidy was documented using the characteristic pattern of double-labeled gene trees. At least 32% of the species sampled are the result of genetic allopolyploidy and result from 28 distinct tetraploidy events plus an additional six hexaploidy events. This number is a minimum, and the actual frequency could be considerably higher. The parental genomes of most Andropogoneae polyploids diverged in the Late Miocene coincident with the expansion of the major C4 grasslands that dominate the earth today. The well-documented whole-genome duplication in Zea mays ssp. mays occurred after the divergence of Zea and Sorghum. We find no evidence that polyploidization is followed by an increase in net diversification rate; nonetheless, allopolyploidy itself is a major mode of speciation. PMID:25288748

  20. Recent changes in mountain grasslands: a vegetation resampling study.

    PubMed

    Gillet, François; Mauchamp, Leslie; Badot, Pierre-Marie; Mouly, Arnaud

    2016-04-01

    Understanding how land-use changes affect different facets of plant biodiversity in seminatural European grasslands is of particular importance for biodiversity conservation. As conclusions of previous experimental or synchronic observational studies did not converge toward a general agreement, assessing the recent trends in vegetation change in various grassland systems using a diachronic approach is needed. In this resurvey study, we investigated the recent changes in grassland vegetation of the French Jura Mountains, a region with a long tradition of pastoralism. We compared the floristic composition of 150 grassland plots recorded between 1990 and 2000 with new relevés made in 2012 on the same plots. We considered taxonomic, phylogenetic and functional diversity as well as ecological characteristics of the plant communities derived from ecological indicator values and life strategies of the species. PCA of the floristic composition revealed a significant general trend linked to the sampling year. Wilcoxon paired tests showed that contemporary communities were generally more dominated by grass species and presented a higher tolerance to defoliation, a higher pastoral value, and a higher nutrient indicator value. Comparisons revealed a decrease in phylogenetic and functional diversity. By contrast, local species richness has slightly increased. The intensity of change in species composition, measured by Hellinger distance between pairs of relevés, was dependent on neither the time lag between the two surveys, the author of the first relevé nor its location or elevation. The most important changes were observed in grasslands that previously presented low pastoral value, low grass cover, low tolerance to defoliation, and high proportion of stress-tolerant species. This trend was likely linked to the intensification of grassland management reported in the region, with a parallel increase in mowing frequency, grazing pressure, and fertilization level. More

  1. Ecosystem Carbon Storage in Alpine Grassland on the Qinghai Plateau.

    PubMed

    Liu, Shuli; Zhang, Fawei; Du, Yangong; Guo, Xiaowei; Lin, Li; Li, Yikang; Li, Qian; Cao, Guangmin

    2016-01-01

    The alpine grassland ecosystem can sequester a large quantity of carbon, yet its significance remains controversial owing to large uncertainties in the relative contributions of climate factors and grazing intensity. In this study we surveyed 115 sites to measure ecosystem carbon storage (both biomass and soil) in alpine grassland over the Qinghai Plateau during the peak growing season in 2011 and 2012. Our results revealed three key findings. (1) Total biomass carbon density ranged from 0.04 for alpine steppe to 2.80 kg C m-2 for alpine meadow. Median soil organic carbon (SOC) density was estimated to be 16.43 kg C m-2 in alpine grassland. Total ecosystem carbon density varied across sites and grassland types, from 1.95 to 28.56 kg C m-2. (2) Based on the median estimate, the total carbon storage of alpine grassland on the Qinghai Plateau was 5.14 Pg, of which 94% (4.85 Pg) was soil organic carbon. (3) Overall, we found that ecosystem carbon density was affected by both climate and grazing, but to different extents. Temperature and precipitation interaction significantly affected AGB carbon density in winter pasture, BGB carbon density in alpine meadow, and SOC density in alpine steppe. On the other hand, grazing intensity affected AGB carbon density in summer pasture, SOC density in alpine meadow and ecosystem carbon density in alpine grassland. Our results indicate that grazing intensity was the primary contributing factor controlling carbon storage at the sites tested and should be the primary consideration when accurately estimating the carbon storage in alpine grassland. PMID:27494253

  2. Ecosystem Carbon Storage in Alpine Grassland on the Qinghai Plateau

    PubMed Central

    Liu, Shuli; Zhang, Fawei; Du, Yangong; Guo, Xiaowei; Lin, Li; Li, Yikang; Li, Qian; Cao, Guangmin

    2016-01-01

    The alpine grassland ecosystem can sequester a large quantity of carbon, yet its significance remains controversial owing to large uncertainties in the relative contributions of climate factors and grazing intensity. In this study we surveyed 115 sites to measure ecosystem carbon storage (both biomass and soil) in alpine grassland over the Qinghai Plateau during the peak growing season in 2011 and 2012. Our results revealed three key findings. (1) Total biomass carbon density ranged from 0.04 for alpine steppe to 2.80 kg C m-2 for alpine meadow. Median soil organic carbon (SOC) density was estimated to be 16.43 kg C m-2 in alpine grassland. Total ecosystem carbon density varied across sites and grassland types, from 1.95 to 28.56 kg C m-2. (2) Based on the median estimate, the total carbon storage of alpine grassland on the Qinghai Plateau was 5.14 Pg, of which 94% (4.85 Pg) was soil organic carbon. (3) Overall, we found that ecosystem carbon density was affected by both climate and grazing, but to different extents. Temperature and precipitation interaction significantly affected AGB carbon density in winter pasture, BGB carbon density in alpine meadow, and SOC density in alpine steppe. On the other hand, grazing intensity affected AGB carbon density in summer pasture, SOC density in alpine meadow and ecosystem carbon density in alpine grassland. Our results indicate that grazing intensity was the primary contributing factor controlling carbon storage at the sites tested and should be the primary consideration when accurately estimating the carbon storage in alpine grassland. PMID:27494253

  3. Estimation of Canopy Water Content in Konza Parry Grasslands Using Synthetic Aperture Radar Measurements During FIFE

    NASA Technical Reports Server (NTRS)

    Saatchi, Sasan S.; van Zyl, Jacob J.; Asrar, Ghassem

    1996-01-01

    This paper presents the development of an algorithm to retrieve the canopy water contents of natural grasslands and pasture from synthetic aperture radar (SAR) measurements. The development on this algorithm involves three interrelated steps: (1) calibration of SAR data for ground topographic variations, (2) development and validation of backscatter model for cross-polarized ratio. The polarimetric radar data acquired by the Jet Propulsion Laboratory AIRSAR system during the 1989 First International Satellite land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) used for this study. The SAR data have been calibrated and corrected for the topographical effects by using the digital elevation map of the study area.

  4. Consistent ozone-induced decreases in pasture forage quality across several grassland types and consequences for UK lamb production.

    PubMed

    Hayes, Felicity; Mills, Gina; Jones, Laurence; Abbott, John; Ashmore, Mike; Barnes, Jeremy; Neil Cape, J; Coyle, Mhairi; Peacock, Simon; Rintoul, Naomi; Toet, Sylvia; Wedlich, Kerstin; Wyness, Kirsten

    2016-02-01

    In this study we have demonstrated that rising background ozone has the potential to reduce grassland forage quality and explored the implications for livestock production. We analysed pasture samples from seven ozone exposure experiments comprising mesotrophic, calcareous, haymeadow and sanddune unimproved grasslands conducted in open-top chambers, solardomes and a field release system. Across all grassland types, there were significant increases in acid detergent fibre, crude fibre and lignin content with increasing ozone concentration, resulting in decreased pasture quality in terms of the metabolisable energy content of the vegetation. We derived a dose-response function for metabolisable energy of the grassland with ozone concentration, applicable to a range of grassland types, and used this to predict effects on pasture quality of UK vegetation at 1 km resolution using modelled ozone data for 2007 and for predicted higher average ozone concentrations in 2020. This showed a potential total reduction in lamb production in the UK of approximately 4% in 2020 compared to 2007. The largest impacts were in geographical areas of modest ozone increases between the two years, but where large numbers of lambs were present. For an individual farmer working to a very small cost margin this could represent a large reduction in profit, both in regions where the impacts per lamb and those where the impacts per km(2) of grazing land are largest. In the short term farmers could adapt their lamb management in response to changed forage quality by additional supplementary feed of high metabolisable energy content. Nationally this increase in annual additional feed in 2020 compared to 2007 would be 2,166 tonnes (an increase of 0.7%). Of added concern are the longer-term consequences of continual deterioration of pasture quality and the implications for changes in farming practices to compensate for potential reductions in livestock production capacity. PMID:26595401

  5. Disentangling direct and indirect effects of experimental grassland management and plant functional-group manipulation on plant and leafhopper diversity

    PubMed Central

    2014-01-01

    Background Plant biodiversity can affect trophic interactions in many ways, including direct bottom-up effects on insects, but is negatively affected by agricultural intensification. Grassland intensification promotes plant productivity, resulting in changes in plant community composition, and impacts on higher trophic levels. Here, we use a novel grassland management experiment combining manipulations of cutting and fertilization with experimental changes in plant functional group composition (independent of management effects) to disentangle the direct and indirect effects of agricultural management on insect herbivore diversity and abundance. We used leafhoppers as model organisms as they are a key insect taxon in grasslands and react rapidly to management changes. Leafhoppers were sampled between May and September 2010 using standardized sweep netting and pan traps. Results Plant diversity, functional group composition and management regime in grasslands affected leafhopper species richness and abundance. Higher cutting frequencies directly led to decreasing leafhopper species richness, presumably due to the higher disturbance frequency and the reduction in food-resource heterogeneity. In contrast, fertilizer application had only a small indirect negative effect via enhanced aboveground plant biomass, reduced plant diversity and changes in functional group composition. The manipulated increase in grass cover had contrasting direct and indirect effects on leafhopper species richness: grass cover directly increased leafhopper species richness, but negatively affected plant diversity, which in turn was positively related to leafhopper species richness. In conclusion, insect diversity is driven in complex direct and indirect ways by grassland management, including changes in functional group composition. Conclusions The availability of preferred food sources and the frequency of disturbance are important direct and indirect drivers of leafhopper species richness

  6. Carbon sink activity and GHG budget of managed European grasslands

    NASA Astrophysics Data System (ADS)

    Klumpp, Katja; Herfurth, Damien; Soussana, Jean-Francois; Fluxnet Grassland Pi's, European

    2013-04-01

    In agriculture, a large proportion (89%) of greenhouse gas (GHG) emission saving potential may be achieved by means of soil C sequestration. Recent demonstrations of carbon sink activities of European ecosystemes, however, often questioned the existence of C storing grasslands, as though a net sink of C was observed, uncertainty surrounding this estimate was larger than the sink itself (Janssens et al., 2003, Schulze et al., 2009. Then again, some of these estimates were based on a small number of measurements, and on models. Not surprising, there is still, a paucity of studies demonstrating the existence of grassland systems, where C sequestration would exceed (in CO2 equivalents) methane emissions from the enteric fermentation of ruminants and nitrous oxide emissions from managed soils. Grasslands are heavily relied upon for food and forage production. A key component of the carbon sink activity in grasslands is thus the impact of changes in management practices or effects of past and recent management, such as intensification as well as climate (and -variation). We analysed data (i.e. flux, ecological, management and soil organic carbon) from a network of European grassland flux observation sites (36). These sites covered different types and intensities of management, and offered the opportunity to understand grassland carbon cycling and trade-offs between C sinks and CH4 and N2O emissions. For some sites, the assessment of carbon sink activities were compared using two methods; repeated soil inventory and determination of the ecosystem C budget by continuous measurement of CO2 exchange in combination with quantification of other C imports and exports (net C storage, NCS). In general grassland, were a potential sink of C with 60±12 g C /m2.yr (median; min -456; max 645). Grazed sites had a higher NCS compared to cut sites (median 99 vs 67 g C /m2.yr), while permanent grassland sites tended to have a lower NCS compared to temporary sown grasslands (median 64 vs

  7. Bioenergy from permanent grassland--a review: 2. Combustion.

    PubMed

    Prochnow, A; Heiermann, M; Plöchl, M; Amon, T; Hobbs, P J

    2009-11-01

    The aim of this review is to summarize current knowledge on suitability and sustainability of grassland biomass for combustion. In the first section grassland management for solid biofuel as well as information on harvest, postharvest and firing technology are described. An extensive grassland management system with one late cut and low level of fertilization is favored for grass as a solid biofuel. The grass harvest usually involves drying in the field and clearing with conventional farm machinery. Pelleting or briquetting improves the biofuel quality. Grass combustion is possible as stand-alone biomass-firing or co-firing with other fuels. Firing herbaceous biomass requires various specific adaptations of the different combustion technologies. In the second section economic and environmental aspects are discussed. Costs for biomass supply mainly depend on yields and harvesting technologies, while combustion costs are influenced by the size and technical design of the plant. Market prices for grass and possible subsidies for land use are crucial for profitability. Regarding biogeochemical cycles a specific feature of combustion is the fact that none of the biomass carbon and nitrogen removed at harvest is available for return to the grassland. These exports can be compensated for by fixation from the air given legumes in the vegetation and sufficient biomass production. Greenhouse gas emissions can be considerably reduced by grass combustion. Solid biofuel production has a potential for predominantly positive impacts on biodiversity due to the extensive grassland management. PMID:19546000

  8. Agricultural practices in grasslands detected by spatial remote sensing.

    PubMed

    Dusseux, Pauline; Vertès, Françoise; Corpetti, Thomas; Corgne, Samuel; Hubert-Moy, Laurence

    2014-12-01

    The major decrease in grassland surfaces associated with changes in their management that has been observed in many regions of the earth during the last half century has major impacts on environmental and socio-economic systems. This study focuses on the identification of grassland management practices in an intensive agricultural watershed located in Brittany, France, by analyzing the intra-annual dynamics of the surface condition of vegetation using remotely sensed and field data. We studied the relationship between one vegetation index (NDVI) and two biophysical variables (LAI and fCOVER) derived from a series of three SPOT images on one hand and measurements collected during field campaigns achieved on 120 grasslands on the other. The results show that the LAI appears as the best predictor for monitoring grassland mowing and grazing. Indeed, because of its ability to characterize vegetation status, LAI estimated from remote sensing data is a relevant variable to identify these practices. LAI values derived from the SPOT images were then classified based on the K-Nearest Neighbor (KNN) supervised algorithm. The results points out that the distribution of grassland management practices such as grazing and mowing can be mapped very accurately (Kappa index = 0.82) at a field scale over large agricultural areas using a series of satellite images. PMID:25182683

  9. Variation in dry grassland communities along a heavy metals gradient.

    PubMed

    Woch, Marcin W; Kapusta, Paweł; Stefanowicz, Anna M

    2016-01-01

    The aim of this study was to investigate the variation in plant communities growing on metal-enriched sites created by historical Zn–Pb mining. The study sites were 65 small heaps of waste rock covered by grassland vegetation and scattered mostly over agricultural land of southern Poland. The sites were described in terms of plant coverage, species richness and composition, and the composition of plant traits. They were classified using phytosociological methods and detrended correspondence analysis. Identified plant communities were compared for vegetation parameters and habitat properties (soil characteristics, distance from the forest) by analysis of variance. The variation in plant community parameters was explained by multiple regression, in which the predictors were properties of the habitat selected on the basis of factor analysis. Grasslands that developed at low and high concentrations of heavy metals in soil were similar to some extent: they were composed on average of 17–20 species (per 4 m(2)), and their total coverage exceeded 90%. The species composition changed substantially with increasing contamination with heavy metals; metal-sensitive species withdrew, while the metal-tolerant became more abundant. Other important predictors of community structure were: proximity to the forest (responsible for the encroachment of competitive forest species and ruderals), and the thickness of the surface soil (shallow soil favored the formation of the heavy metal grassland). The heavy metal grassland was closely related to the dry calcareous grasslands. The former was an earlier succession stage of the latter at low contamination with heavy metals. PMID:26493699

  10. Grassland ecology and population growth: striking a balance.

    PubMed

    Hou, D; Duan, C; Zhang, D

    2000-06-01

    Degradation of forest and grasslands in western China attributes to the soil erosion and desertification in the country. Researchers have established that the primary reason for the degradation of grasslands is overgrazing, which in turn is caused by a number of factors, including over-population and over-reliance on animal husbandry. In addition, the existing administrative system has also proved ineffective in ensuring sustainable development. On contrary, many local governments even encourage exploitative development of grassland; thus, localities opened up grassland for growing crops in an effort to increase income. According to estimates, degraded grassland accounts for more than one-third of utilizable acreage and another one-third suffers from a profusion of rats and pests. To redress the situation, central government should implement strategies in achieving sustainable development, such as providing banking and tax incentives for the development of the secondary and tertiary industries, and supporting education and training of youths from herding areas. Moreover, government should increase spending on infrastructural construction and ecological preservation. Finally, the family planning program needs to be enforced to control population growth and improve the quality of peoples¿ lives. PMID:12322589

  11. Dick Crane's California Days

    NASA Astrophysics Data System (ADS)

    Holbrow, Charles H.

    2011-03-01

    Horace Richard Crane (1907-2007) was born and educated in California. His childhood was full of activities that helped him become an outstanding experimental physicist. As a graduate student at the California Institute of Technology (1930-1934), he had the good fortune to work with Charles C. Lauritsen (1892-1968) just as he introduced accelerator-based nuclear physics to Caltech. They shared the euphoric excitement of opening up a new field with simple, ingenious apparatus and experiments. This work prepared Crane for his career at the University of Michigan (1935-1973) where in the 1950s, after making the first measurement of the electron's magnetic moment, he devised the g-2 technique and made the first measurement of the anomaly in the electron's magnetic moment. A man of direct, almost laconic style, he made lasting contributions to the exposition of physics to the general public and to its teaching in high schools, community colleges, four-year colleges, and universities. I tell how he became a physicist and describe some of his early achievements.

  12. California Workforce: California Faces a Skills Gap

    ERIC Educational Resources Information Center

    Public Policy Institute of California, 2011

    2011-01-01

    California's education system is not keeping up with the changing demands of the state's economy--soon, California will face a shortage of skilled workers. Projections to 2025 suggest that the economy will continue to need more and more highly educated workers, but that the state will not be able to meet that demand. If current trends persist,…

  13. Feedbacks between aeolian processes and ecosystem change in a degraded desert grassland in the southwestern US

    NASA Astrophysics Data System (ADS)

    Li, Junran

    2015-04-01

    The desert grassland in the southwestern US has undergone dramatic vegetation changes with many areas of grassland becoming shrublands in the last 150 years. A principle manifestation of such a land degradation is the wide distribution of fertile islands in once-homogenous landscapes, which changed soil resource redistributions through the movement of resources from plant interspaces to the area beneath plant canopies. A great deal of work has examined the role of water in nutrient reduction and enforcement of islands of fertility in the semiarid landscapes. However, little is known on the role of wind in the removal or redistribution of soil resources, and further the feedbacks between wind and ecosystem change in this area. In spring 2004, a vegetation removal experiment was established in the northern Chihuahuan Desert, southern New Mexico, where vegetation cover on the experimental plots were manually reduced to various levels to study the entire suite of aeolian processes, including erosion, transport, and deposition in creating and enforcing patchy distribution of vegetation. This experiment has been continually maintained for more than ten years, with the sampling and observation of vegetation cover, soil nutrients, sediment flux, topography, and plant physiology. The experimental results highlighted that the aeolian processes in the Chihuahuan Desert are able to change soil properties and community composition in as short as 3 three years. Further, the removal of grasses by 75% may trigger a very substantial increase of wind erosion and the removal of grass by 50% could cause significant amount of C and N loss due to wind erosion. Last but not least, the change of the spatial distribution of soil C and the micro-topography both point to the fact that aeolian processes contribute substantially to the dynamics of fertile islands in this desert grassland.

  14. Response of lizard community structure to desert grassland restoration mediated by a keystone rodent

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many grasslands in the Chihuahuan Desert have transformed to shrublands dominated by creosotebush (Larrea tridentata). Grassland restoration efforts have been directed at controlling creosotebush by applying herbicide over large spatial scales. However, we have a limited understanding of how landsca...

  15. 75 FR 18202 - Grassland Renewables Energy LLC; Notice of Petition for Declaratory Order

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-09

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Grassland Renewables Energy LLC; Notice of Petition for Declaratory Order... Regulatory Commission's (Commission) Rules of Practice and Procedure, Grassland Renewables Energy LLC...

  16. 75 FR 22588 - Grassland Renewables Energy LLC; Notice of Petition for Declaratory Order

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-29

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Grassland Renewables Energy LLC; Notice of Petition for Declaratory Order... Regulatory Commission's (Commission) Rules of Practice and Procedure, Grassland Renewables Energy LLC...

  17. Restoring Tropical Grassland Productivity with Facilitated Biofertilisation

    NASA Astrophysics Data System (ADS)

    Williams, Wendy; Büdel, Burkhard

    2015-04-01

    Grazing is the major economic activity in northern Australia's subtropical grasslands, savannah and shrublands that cover >1.9 million km2 however; there has been significant decline in soil fertility that has led to the need to consider ways to improve management. Terrestrial cyanobacteria primarily inhabit complex soil microbial communities that drive physical and biological processes in the topsoil. These microbes facilitate resilience to drought and maintain soil function. They transform their environment through the secretion of mucilaginous organic compounds that improve aggregate stability, porosity, rainfall infiltration rates and water storage, reduce evaporation and soil erosion and, improve seedling emergence. In the northern Australian savannah cyanobacterial communities dominate soil surfaces of the perennial tussock grasslands. The core focus of this research has been to better understand the function of cyanobacteria within the climate-soil-plant ecosystem. The recent discovery that cyanobacteria are programmed to detect and respond only to wet season rains, and remain inactive and unproductive during the dry season even if it rains, has rewritten our understanding of soil nutrient cycles in the northern Australian savannah. In this project we have established: 1. For the wet season trials (Dec 2009-May 2010) the mean values of cyanobacterial crust (0-1 cm depth; n=100) plant-available N fluctuated, yet significantly increased incrementally from Dec to Feb (2.74 ± 0.37SE-5.62 ± 0.82 mg NH4+ kg-1 soil; p = 0.003) and peaked from Mar-May (9.59 ± 1.5SE-16.04 ± 3.2SE mg NH4+ kg-1 soil; p = 0.127) that represented the concluding stages of the wet season. 2. Cyanobacterial rates of N-fixation (determined by Acetylene Reduction assays, n=6 per month), increased significantly from the commencement to the height of the wet season (13.2 ± 2.9SE-30.2 ± 1.9SE kg N ha-1; p = 0.001) and decreased towards the end of the wet season (10.4 ± 1.8SE kg N ha-1; p

  18. California State University, Sacramento

    ERIC Educational Resources Information Center

    Varlotta, Lori E.

    2009-01-01

    California State University, Sacramento, commonly referred to as "Sacramento State," is a booming metropolitan university located on 300 acres in the state capital of California. The university, the seventh largest in the California State University system, enrolls a multicultural student body of approximately 29,000 students. At Sacramento State,…

  19. California Burn Scars

    Atmospheric Science Data Center

    2014-05-15

    article title:  Burn Scars Across Southern California     ... California between October 21 and November 18, 2003. Burn scars and vegetation changes wrought by the fires are illustrated in these ... Nov 18, 2003 Images:  California Burn Scars location:  United States region:  ...

  20. Nitrogen addition and harvest frequency rather than initial plant species composition determine vertical structure and light interception in grasslands.

    PubMed

    Petersen, Ute; Isselstein, Johannes

    2015-01-01

    In biodiversity experiments based on seeded experimental communities, species richness and species composition exert a strong influence on canopy structure and can lead to an improved use of aboveground resources. In this study, we want to explore whether these findings are applicable to agriculturally managed permanent grassland. Vertical layered profiles of biomass, leaf area (LA) and light intensity were measured in a removal-type biodiversity experiment (GrassMan) to compare the canopy structure in grassland vegetation of different plant species composition (called sward types). Additionally, the altered sward types were subjected to four different management regimes by a combination of the factors fertilization (unfertilized, NPK fertilized) and cutting frequency (one late cut or three cuts). In spite of large compositional differences (ratio grasses : non-leguminous forbs : leguminous forbs ranging from 93 : 7 : 0 to 39 : 52 : 9), the vegetation of the same management regime hardly differed in its canopy structure, whereas the different management regimes led to distinct vertical profiles in the vegetation. However, the allocation of biomass in response to cutting and fertilization differed among the sward types. Vegetation dominated by grasses was denser and had more LA when fertilized compared with vegetation rich in dicots which merely grew taller. In functionally more diverse vegetation, light interception was not increased compared with vegetation consisting of more than 90 % of grasses in terms of biomass. Management had a much stronger influence on structure and light interception than plant species composition in this grassland experiment. PMID:26199402

  1. Do patients hospitalised in high-minority hospitals experience more diversion and poorer outcomes? A retrospective multivariate analysis of Medicare patients in California

    PubMed Central

    Shen, Yu-Chu; Hsia, Renee Y

    2016-01-01

    Objective We investigated the association between crowding as measured by ambulance diversion and differences in access, treatment and outcomes between black and white patients. Design Retrospective analysis. Setting We linked daily ambulance diversion logs from 26 California counties between 2001 and 2011 to Medicare patient records with acute myocardial infarction and categorised patients according to hours in diversion status for their nearest emergency departments on their day of admission: 0, <6, 6 to <12 and ≥12 h. We compared the amount of diversion time between hospitals serving high volume of black patients and other hospitals. We then use multivariate models to analyse changes in outcomes when patients faced different levels of diversion, and compared that change between black and white patients. Participants 29 939 Medicare patients from 26 California counties between 2001 and 2011. Main outcome measures (1) Access to hospitals with cardiac technology; (2) treatment received; and (3) health outcomes (30-day, 90-day, and 1-year death and 30-day readmission). Results Hospitals serving high volume of black patients spent more hours in diversion status compared with other hospitals. Patients faced with the highest level of diversion had the lowest probability of being admitted to hospitals with cardiac technology compared with those facing no diversion, by 4.4% for cardiac care intensive unit, and 3.4% for catheterisation laboratory and coronary artery bypass graft facilities. Patients experiencing increased diversion also had a 4.3% decreased likelihood of receiving catheterisation and 9.6% higher 1-year mortality. Conclusions Hospitals serving high volume of black patients are more likely to be on diversion, and diversion is associated with poorer access to cardiac technology, lower probability of receiving revascularisation and worse long-term mortality outcomes. PMID:26988352

  2. Building Code Compliance and Enforcement: The Experience of SanFrancisco's Residential Energy Conservation Ordinanace and California'sBuildign Standards for New Construction

    SciTech Connect

    Vine, E.

    1990-11-01

    As part of Lawrence Berkeley Laboratory's (LBL) technical assistance to the Sustainable City Project, compliance and enforcement activities related to local and state building codes for existing and new construction were evaluated in two case studies. The analysis of the City of San Francisco's Residential Energy Conservation Ordinance (RECO) showed that a limited, prescriptive energy conservation ordinance for existing residential construction can be enforced relatively easily with little administrative costs, and that compliance with such ordinances can be quite high. Compliance with the code was facilitated by extensive publicity, an informed public concerned with the cost of energy and knowledgeable about energy efficiency, the threat of punishment (Order of Abatement), the use of private inspectors, and training workshops for City and private inspectors. The analysis of California's Title 24 Standards for new residential and commercial construction showed that enforcement of this type of code for many climate zones is more complex and requires extensive administrative support for education and training of inspectors, architects, engineers, and builders. Under this code, prescriptive and performance approaches for compliance are permitted, resulting in the demand for alternative methods of enforcement: technical assistance, plan review, field inspection, and computer analysis. In contrast to existing construction, building design and new materials and construction practices are of critical importance in new construction, creating a need for extensive technical assistance and extensive interaction between enforcement personnel and the building community. Compliance problems associated with building design and installation did occur in both residential and nonresidential buildings. Because statewide codes are enforced by local officials, these problems may increase over time as energy standards change and become more complex and as other standards (eg, health and

  3. AmeriFlux US-Seg Sevilleta grassland

    SciTech Connect

    Litvak, Marcy

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-Seg Sevilleta grassland. Site Description - The Sevilleta Desert Grassland site is located within the McKenzie Flats area of the Sevilleta National Wildlife Refuge (NWR), central New Mexico. Historically, this area has been used for livestock grazing; however, the McKenzie Flats have not been grazed since 1973 and the effects of this previous grazing are considered negligible for the purposes of this study. As the name suggests, McKenzie Flats is an extensive (~130 km2), nearly flat, mixed-species desert grassland bounded on the east by Los Pinos Mountains and on the west by the Rio Grande.

  4. Assessing the Effects of Grassland Management on Forage Production and Environmental Quality to Identify Paths to Ecological Intensification in Mountain Grasslands.

    PubMed

    Loucougaray, Grégory; Dobremez, Laurent; Gos, Pierre; Pauthenet, Yves; Nettier, Baptiste; Lavorel, Sandra

    2015-11-01

    Ecological intensification in grasslands can be regarded as a process for increasing forage production while maintaining high levels of ecosystem functions and biodiversity. In the mountain Vercors massif, where dairy cattle farming is the main component of agriculture, how to achieve forage autonomy at farm level while sustaining environmental quality for tourism and local dairy products has recently stimulated local debate. As specific management is one of the main drivers of ecosystem functioning, we assessed the response of forage production and environmental quality at grassland scale across a wide range of management practices. We aimed to determine which components of management can be harnessed to better match forage production and environmental quality. We sampled the vegetation of 51 grasslands stratified across 13 grassland types. We assessed each grassland for agronomic and environmental properties, measuring forage production, forage quality, and indices based on the abundance of particular plant species such as timing flexibility, apiarian potential, and aromatic plants. Our results revealed an expected trade-off between forage production and environmental quality, notably by stressing the contrasts between sown and permanent grasslands. However, strong within-type variability in both production and environmental quality as well as in flexibility of timing of use suggests possible ways to improve this trade-off at grassland and farm scales. As achieving forage autonomy relies on increasing both forage production and grassland resilience, our results highlight the critical role of the ratio between sown and permanent grasslands as a major path for ecological intensification in mountain grasslands. PMID:26092047

  5. Assessing the Effects of Grassland Management on Forage Production and Environmental Quality to Identify Paths to Ecological Intensification in Mountain Grasslands

    NASA Astrophysics Data System (ADS)

    Loucougaray, Grégory; Dobremez, Laurent; Gos, Pierre; Pauthenet, Yves; Nettier, Baptiste; Lavorel, Sandra

    2015-11-01

    Ecological intensification in grasslands can be regarded as a process for increasing forage production while maintaining high levels of ecosystem functions and biodiversity. In the mountain Vercors massif, where dairy cattle farming is the main component of agriculture, how to achieve forage autonomy at farm level while sustaining environmental quality for tourism and local dairy products has recently stimulated local debate. As specific management is one of the main drivers of ecosystem functioning, we assessed the response of forage production and environmental quality at grassland scale across a wide range of management practices. We aimed to determine which components of management can be harnessed to better match forage production and environmental quality. We sampled the vegetation of 51 grasslands stratified across 13 grassland types. We assessed each grassland for agronomic and environmental properties, measuring forage production, forage quality, and indices based on the abundance of particular plant species such as timing flexibility, apiarian potential, and aromatic plants. Our results revealed an expected trade-off between forage production and environmental quality, notably by stressing the contrasts between sown and permanent grasslands. However, strong within-type variability in both production and environmental quality as well as in flexibility of timing of use suggests possible ways to improve this trade-off at grassland and farm scales. As achieving forage autonomy relies on increasing both forage production and grassland resilience, our results highlight the critical role of the ratio between sown and permanent grasslands as a major path for ecological intensification in mountain grasslands.

  6. Modeling effects of conservation grassland losses on amphibian habitat

    USGS Publications Warehouse

    Mushet, David M.; Neau, Jordan L.; Euliss, Ned H.

    2014-01-01

    Amphibians provide many ecosystem services valued by society. However, populations have declined globally with most declines linked to habitat change. Wetlands and surrounding terrestrial grasslands form habitat for amphibians in the North American Prairie Pothole Region (PPR). Wetland drainage and grassland conversion have destroyed or degraded much amphibian habitat in the PPR. However, conservation grasslands can provide alternate habitat. In the United States, the Conservation Reserve Program (CRP) is the largest program maintaining grasslands on agricultural lands. We used an ecosystem services model (InVEST) parameterized for the PPR to quantify amphibian habitat over a six-year period (2007–2012). We then quantified changes in availability of amphibian habitat under various land-cover scenarios representing incremental losses (10%, 25%, 50%, 75%, and 100%) of CRP grasslands from 2012 levels. The area of optimal amphibian habitat in the four PPR ecoregions modeled (i.e., Northern Glaciated Plains, Northwestern Glaciated Plains, Lake Agassiz Plain, Des Moines Lobe) declined by approximately 22%, from 3.8 million ha in 2007 to 2.9 million ha in 2012. These losses were driven by the conversion of CRP grasslands to croplands, primarily for corn and soybean production. Our modeling identified an additional 0.8 million ha (26%) of optimal amphibian habitat that would be lost if remaining CRP lands are returned to crop production. An economic climate favoring commodity production over conservation has resulted in substantial losses of amphibian habitat across the PPR that will likely continue into the future. Other regions of the world face similar challenges to maintaining amphibian habitats.

  7. Associations of grassland birds with landscape factors in southern Wisconsin

    USGS Publications Warehouse

    Ribic, C.A.; Sample, D.W.

    2001-01-01

    We investigated the association of grassland birds with field- and landscape-level habitat variables in south-central Wisconsin during 1985-1987. Landscape-level variables were measured and digitized at 200, 400 and 800 m from the perimeter of 38 200 m ?? 100 m strip transects. A mixture of field and landscape variables was associated with the density of savannah sparrow (Passerculus sandwichensis) and grasshopper sparrow (Ammodramus savannarum). Only landscape variables were associated with the density of bobolink (Dolichonyx oryzivorus), eastern meadowlark (Sturnella magna) and all birds that were grassland species of management concern. Field size was not an important predictor of bird density. Cover-type diversity of the surrounding area was commonly selected in the models for three species and all birds that were grassland species of management concern. Higher bird densities in the transects were associated with landscapes where the cover types were less diverse. Landscapes with low cover type diversity were dominated by grassland, pasture and hay. Field habitat, mean patch size of cover types and distance to woody vegetation were the next most common predictors of avian density. The density of some grassland birds increased as nonlinear woody features such as woodlots and shrub carrs decreased in patch size, decreased in total amount in the landscape and increased in distance from a transect. However, density of other species was positively associated with linear woody features such as the total amount and nearness of hedgerows. The composition of the surrounding landscape, at least out to 800 m, is important in grassland bird management.

  8. Energy Potential of Biomass from Conservation Grasslands in Minnesota, USA

    PubMed Central

    Jungers, Jacob M.; Fargione, Joseph E.; Sheaffer, Craig C.; Wyse, Donald L.; Lehman, Clarence

    2013-01-01

    Perennial biomass from grasslands managed for conservation of soil and biodiversity can be harvested for bioenergy. Until now, the quantity and quality of harvestable biomass from conservation grasslands in Minnesota, USA, was not known, and the factors that affect bioenergy potential from these systems have not been identified. We measured biomass yield, theoretical ethanol conversion efficiency, and plant tissue nitrogen (N) as metrics of bioenergy potential from mixed-species conservation grasslands harvested with commercial-scale equipment. With three years of data, we used mixed-effects models to determine factors that influence bioenergy potential. Sixty conservation grassland plots, each about 8 ha in size, were distributed among three locations in Minnesota. Harvest treatments were applied annually in autumn as a completely randomized block design. Biomass yield ranged from 0.5 to 5.7 Mg ha−1. May precipitation increased biomass yield while precipitation in all other growing season months showed no affect. Averaged across all locations and years, theoretical ethanol conversion efficiency was 450 l Mg−1 and the concentration of plant N was 7.1 g kg−1, both similar to dedicated herbaceous bioenergy crops such as switchgrass. Biomass yield did not decline in the second or third year of harvest. Across years, biomass yields fluctuated 23% around the average. Surprisingly, forb cover was a better predictor of biomass yield than warm-season grass with a positive correlation with biomass yield in the south and a negative correlation at other locations. Variation in land ethanol yield was almost exclusively due to variation in biomass yield rather than biomass quality; therefore, efforts to increase biomass yield might be more economical than altering biomass composition when managing conservation grasslands for ethanol production. Our measurements of bioenergy potential, and the factors that control it, can serve as parameters for assessing the economic

  9. Productivity of North American grasslands is increased under future climate scenarios despite rising aridity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grassland productivity is regulated by both temperature and the amount and timing of precipitation. Future climate change is therefore expected to influence grassland phenology and growth, with consequences for ecosystems and economies. However, the potential response of grasslands to climate change...

  10. 78 FR 19444 - Pawnee National Grassland, Colorado; Oil and Gas Leasing Analysis Environmental Impact Statement

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-01

    ...; ] DEPARTMENT OF AGRICULTURE Forest Service Pawnee National Grassland, Colorado; Oil and Gas Leasing Analysis... Pawnee National Grassland Record of Decision (ROD) for the Revision of the Land and Resource Management Plan (LRMP), which included the Oil and Gas Leasing Analysis on the Pawnee National Grassland...

  11. 77 FR 39987 - Arapaho and Roosevelt National Forests and Pawnee National Grassland; Boulder and Gilpin County...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-06

    ... Forest Service Arapaho and Roosevelt National Forests and Pawnee National Grassland; Boulder and Gilpin... and Pawnee National Grassland is preparing an Environmental Impact Statement (EIS) to consider and... Pawnee National Grassland, located at 2140 Yarmouth Avenue, Boulder, CO 80301; and one on July 19,...

  12. 77 FR 56808 - Arapaho and Roosevelt National Forests and Pawnee National Grassland; Larimer County, CO; Middle...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-14

    ...; ] DEPARTMENT OF AGRICULTURE Forest Service Arapaho and Roosevelt National Forests and Pawnee National Grassland... Roosevelt National Forests and Pawnee National Grassland is preparing an environmental impact statement to... Supervisor for the Arapaho and Roosevelt National Forests and Pawnee National Grassland. Nature of...

  13. California rides the tiger

    SciTech Connect

    Garner, W.L.

    1995-01-01

    Revolutions rarely succeed without a struggle. At the California Public Utilities Commission (CPUC), the move to restructure the state`s electric utility industry is no exception. The stakes are enormous. For starters, annual revenues at the state`s investor-owned electric utilities (IOUs) exceed $18 billion, making up 2 percent of California`s gross state product. Competitively priced electricity is vital to California`s $800-billion-a-year economy, one would think. And with its sweeping restructing plan, the CPUC has found itself riding a tiger, hoping it won`t get swallowed whole in the process.

  14. Effects of haying on breeding birds in CRP grasslands

    USGS Publications Warehouse

    Igl, Lawrence D.; Johnson, Douglas H.

    2016-01-01

    The Conservation Reserve Program (CRP) is a voluntary program that is available to agricultural producers to help protect environmentally sensitive or highly erodible land. Management disturbances of CRP grasslands generally are not allowed unless authorized to provide relief to livestock producers during severe drought or a similar natural disaster (i.e., emergency haying and grazing) or to improve the quality and performance of the CRP cover (i.e., managed haying and grazing). Although CRP grasslands may not be hayed or grazed during the primary bird-nesting season, these disturbances may have short-term (1 yr after disturbance) and long-term (≥2 yr after disturbance) effects on grassland bird populations. We assessed the effects of haying on 20 grassland bird species in 483 CRP grasslands in 9 counties of 4 states in the northern Great Plains, USA between 1993 and 2008. We compared breeding bird densities (as determined by total-area counts) in idle and hayed fields to evaluate changes 1, 2, 3, and 4 years after haying. Haying of CRP grasslands had either positive or negative effects on grassland birds, depending on the species, the county, and the number of years after the initial disturbance. Some species (e.g., horned lark [Eremophila alpestris], bobolink [Dolichonyx oryzivorus]) responded positively after haying, and others (e.g., song sparrow [Melospiza melodia]) responded negatively. The responses of some species changed direction as the fields recovered from haying. For example, densities for common yellowthroat (Geothlypis trichas), sedge wren (Cistothorus platensis), and clay-colored sparrow (Spizella pallida) declined the first year after haying but increased in the subsequent 3 years. Ten species showed treatment × county interactions, indicating that the effects of haying varied geographically. This long-term evaluation on the effects of haying on breeding birds provides important information on the strength and direction of changes in

  15. Anthropogenic disturbances are key to maintaining the biodiversity of grasslands.

    PubMed

    Yuan, Z Y; Jiao, F; Li, Y H; Kallenbach, Robert L

    2016-01-01

    Although anthropogenic disturbances are often perceived as detrimental to plant biodiversity, the relationship between biodiversity and disturbance remains unclear. Opinions diverge on how natural diversity is generated and maintained. We conducted a large-scale investigation of a temperate grassland system in Inner Mongolia and assessed the richness-disturbance relationship using grazing intensity, the primary anthropogenic disturbance in the region. Vascular plant-species richness peaked at an intermediate level of anthropogenic disturbance. Our results support the Intermediate Disturbance Hypothesis, which provides a valid and useful measure of biodiversity at a metacommunity scale, indicating that anthropogenic disturbances are necessary to conserve the biodiversity of grassland systems. PMID:26903041

  16. Bifurcation analysis of a forest-grassland ecosystem

    NASA Astrophysics Data System (ADS)

    Russo, Lucia; Spiliotis, Konstantinos G.

    2016-06-01

    The nonlinear analysis of a forest-grassland ecosystem is performed as the main system parameters are changed. The model consists of a couple of nonlinear ordinary differential equations which include dynamically the human perceptions of forest/grassland value. The system displays multiple steady states corresponding to different forest densities as well as periodic regimes characterized by oscillations in time. We performed the bifurcation analysis of the system as the parameter relative to the human opinions influence is changed. We found that the main mechanisms which regulate the transitions occurring between different states or the appearance of new steady and dynamic regimes are transcritical, saddle/node and Hopf bifurcations.

  17. Anthropogenic disturbances are key to maintaining the biodiversity of grasslands

    PubMed Central

    Yuan, Z. Y.; Jiao, F.; Li, Y. H.; Kallenbach, Robert L.

    2016-01-01

    Although anthropogenic disturbances are often perceived as detrimental to plant biodiversity, the relationship between biodiversity and disturbance remains unclear. Opinions diverge on how natural diversity is generated and maintained. We conducted a large-scale investigation of a temperate grassland system in Inner Mongolia and assessed the richness-disturbance relationship using grazing intensity, the primary anthropogenic disturbance in the region. Vascular plant-species richness peaked at an intermediate level of anthropogenic disturbance. Our results support the Intermediate Disturbance Hypothesis, which provides a valid and useful measure of biodiversity at a metacommunity scale, indicating that anthropogenic disturbances are necessary to conserve the biodiversity of grassland systems. PMID:26903041

  18. Grassland management affects belowground carbon allocation in mountain grasslands and its resistance and resilience to drought

    NASA Astrophysics Data System (ADS)

    Karlowsky, Stefan; Augusti, Angela; Ingrisch, Johannes; Hasibeder, Roland; Bahn, Michael; Gleixner, Gerd

    2015-04-01

    Future climate scenarios do not only forecast increased extreme events during summer, but also more frequent drought events in the early season. In mountain grasslands, different land uses may contribute to the response of the ecosystem to climate changes, like drought in May and June. In this study, we examined the drought response of two differently managed grasslands, 1) a more intensive used meadow and 2) a less intensive used abandoned area. Our aim was to highlight differences in both resistance and resilience of ecosystem functioning, based on carbon (C) belowground allocation as a key function in the plant-rhizosphere continuum. Therefore, we used an isotopic approach and in particular, we used 13C pulse labelling to track the fate of newly assimilated C from leaves, to roots and to soil, up to different microbial communities. We performed two 13C pulse labellings, the first during the acute phase of drought, when the water status of soil was drastically decreased compared to the control; and the second during the recovery phase, when the soil water status was restored to control level. We followed the kinetics of 13C incorporation in above- and below-ground bulk material as well as non-structural sugars, in general soil microbial biomass, in different soil microbial communities and in CO2 respired from roots, up to 5 days from each labelling. Preliminary results from the 13C analyses of bulk phytomass material and soil microbial biomass indicate, as expected, different kinetics of aboveground 13C incorporation and its belowground allocation. During the acute phase of drought, 13C incorporation shows a decrease compared to the control for both land uses, with generally higher reductions in meadow treatments. Root 13C tracer dynamics follow the leaf 13C enrichment with a delay. High label amounts are found in leaves directly after labelling, whereas in roots high 13C incorporation is found first after 24 hours, accompanied by a fast decrease of 13C label in

  19. Measurement of advection of CO2 over grasslands in complex terrain in the Alps

    NASA Astrophysics Data System (ADS)

    Zhao, Peng; Hammerle, Albin; Wohlfahrt, Georg

    2015-04-01

    The role of advection is often ignored in the estimation of net ecosystem exchange (NEE) of CO2 in ecosystems. However, some studies reported that more realistic estimates of night-time NEE could be gathered if horizontal and vertical advections are included. While most of previous advection experiments have been conducted in forest ecosystems, grassland ecosystems have a great advantage as measurements of advection can be realised with smaller infrastructure and thus less experimental effort. In a preliminary simplified study, advection showed an important contribution to NEE during night time at a sub-alpine grassland site. This three-year program is focused on the role of advection for NEE of grassland ecosystems in complex terrain in the Alps. We are going to carry out field campaigns at four sites which cover a range of terrain types typical for mountains with varying degrees of complexity, including a valley-bottom site, a steep-slope site, a mixed-terrain site, and an undulating-terrain site. Observations will take place in a notional control volume with a length varying from 50 m to 5 m at each site in order to quantify the effects of horizontal spatial scale on advection estimates. The observations at each site include vertical flux of CO2 measured by eddy-covariance technique, horizontal and vertical advections of CO2 calculated from the measurement of wind components and CO2 gradients, and NEE measured by chambers. Among all, the measurement of the horizontal advection of CO2 needs many efforts because of small-scale variability in sources/sinks of CO2. We are going to use tubes with multiple inlets, which allows sampling at multiple positions across the faces at three heights of the control volume. Thus, we would be able to quantify the contribution of advection to NEE at different grassland sites situated in complex terrain in the Alps, and to quantify the effect of spatial scale of advection measurements with a given experimental setup and accuracy on

  20. Soil degradation in semi-arid grasslands due to intensive grazing in Northern China

    NASA Astrophysics Data System (ADS)

    Wiesmeier, M.; Steffens, M.; Kölbl, A.; Kögel-Knabner, I.

    2012-04-01

    Degradation of semi-arid grasslands is a global environmental problem, particularly in Inner Mongolia, Northern China, where up to 70% of the total area is classified as degraded steppe. The main cause of grassland degradation in Northern China is overgrazing as a result of increasing stocking rates and a static grazing management during the last 50 years. The aim of this study was to investigate the impact of intensive grazing on the stabilization processes, the amount and the spatial distribution of soil organic matter (SOM) in the grasslands of Inner Mongolia. Within the Xilin River Catchment, intensively grazed sites were compared with ungrazed experimental sites at different spatial and temporal scales. In order to determine short-term effects of intensive grazing, a controlled grazing experiment was established in 2005. Topsoil samples were taken in 2005 and again in 2008 from ungrazed (UG05), moderately grazed (MG) and heavily grazed plots (HG) and analyzed for chemical and physical soil properties. The effects of long-term grazing were investigated in detail at continuously grazed sites (CG) and compared to adjacent ungrazed sites that were fenced in 1979 (UG79). To elucidate the spatial structure of selected topsoil parameters at the field scale, 100 grid points with spacings of 5 m and 15 m were sampled. For detection of small-scale variability at the plant scale, 40 randomly selected points were sampled inside areas of 2 m × 2 m at each plot. Semivariances were calculated for the determined soil properties. To quantify the contribution of single soil fractions to total SOC stocks, a combined density and particle size fractionation was applied. Carbon mineralization was determined in an incubation experiment for a period of one month for UG79 and CG sites. Grazing exclusion led to a significant decrease of SOC in the topsoil already three years after grazing exclusion and resulted in 25-30% lower amounts after 30 years. This decrease was related to lower

  1. Learning from California`s QF auction

    SciTech Connect

    Gribik, P.

    1995-04-15

    California`s 1993 qualifying facility (QF) auction dramatically illustrates problems that can be encountered in structuring auctions for electric utility solicitations of supply-side resources from qualifying cogeneration and small power production facilities. In the 1993 California QF auction, three California utilities were to select QFs that would be awarded long-term purchased-power contracts. The auction produced some unexpected outcomes that could potentially cost the utilities and their customers tens of millions of dollars per year. A year after the auction was held, the parties were still attempting to revise contracts, or even rebid a portion of the auction. And all of this effort may come to naught, depending upon what happens now that the Federal Energy Regulatory Commission has struck down the auction process under California`s Biennial Resource Plan Update, claiming that it violates the Public Utility Regulatory Policies Act (PURPA) by using an improper method to calculate avoided costs. A study of the California QF auction illustrates yet again that the devil is in the details. And the stakes will only rise farther as regulators in other states rely more on auctions to open up the electric industry to further competition.

  2. Community assembly in experimental grasslands: suitable environment or timely arrival?

    PubMed

    Ejrnaes, Rasmus; Bruun, Hans Henrik; Graae, Bente J

    2006-05-01

    It is hard to defend the view that biotic communities represent a simple and predictable response to the abiotic environment. Biota and the abiotic environment interact, and the environment of an individual certainly includes its neighbors and visitors in the community. The complexity of community assembly calls forth a quest for general principles, yet current results and theories on assembly rules differ widely. Using a grassland microcosm as a model system, we manipulated fertility, disturbance by defoliation, soil/microclimate, and arrival order of species belonging to two groups differing in functional attributes. We analyzed the outcome of community assembly dynamics in terms of species richness, invasibility, and species composition. The analyses revealed strong environmental control over species richness and invasibility. Species composition was mainly determined by the arrival order of species, indicating that historical contingency may change the outcome of community assembly. The probability for multiple equilibria appeared to increase with productivity and environmental stability. The importance of arrival order offers an explanation of the difficulties in predicting local occurrences of species in the field. In our experiment, variation in fertility and disturbance was controlling colonization with predictable effects on emergent community properties such as species richness. The key mechanism is suggested to be asymmetric competition, and our results show that this mechanism is relatively insensitive to the species through which it works. While our analyses indicate a positive and significant correlation between richness and invasibility, the significance disappears after accounting for the effect of the environment. The importance of arrival order (historical contingency) and environmental control supports the assumption of the unified neutral theory that different species within a trophic level can be considered functionally equivalent when it comes

  3. An evaluation of the regional acid deposition model surface module for ozone uptake at three sites in the San Joaquin Valley of California

    NASA Technical Reports Server (NTRS)

    Massman, W. J.; Pederson, J.; Delany, A.; Grantz, D.; Hertog, G. Den; Neumann, H. H.; Oncley, S. P.; Pearson, R., Jr.; Shaw, R. H.

    1994-01-01

    Plants and soils act as major sinks for the destruction of tropospheric ozone, especially during daylight hours when plant stomata open and are thought to provide the dominant pathway for the uptake of ozone. The present study, part of the California Ozone Deposition Experiment, compares predictions of the regional acid deposition model ozone surface conductance module with surface conductance data derived from eddy covariance measurements of ozone flux taken at a grape, a cotton, and a grassland site in the San Joaquin Valley of California during the summer of 1991. Results indicate that the model (which was developed to provide long-term large-area estimates for the eastern United States) significantly overpredicts the surface conductance at all times of the day for at least two important types of plant cover of the San Joaquin Valley and that it incorrectly partitions the ozone flux between transpiring and nontranspiring components of the surface at the third site. Consequently, the model either overpredicts or inaccurately represents the observed deposition velocities. Other results indicate that the presence of dew does not reduce the rate of ozone deposition, contradicting to model assumptions, and that model assumptions involving the dependency of stomata upon environmental temperature are unnecessary. The effects of measurement errors and biases, arising from the presence of the roughness sublayer and possible photochemical reactions, are also discussed. A simpler model for ozone surface deposition (at least for the San Joaquin Valley) is proposed and evaluated.

  4. An evaluation of the regional acid deposition model surface module for ozone uptake at three sites in the San Joaquin Valley of California

    NASA Astrophysics Data System (ADS)

    Massman, W. J.; Pederson, J.; Delany, A.; Grantz, D.; den Hartog, G.; Neumann, H. H.; Oncley, S. P.; Pearson, R.; Shaw, R. H.

    1994-04-01

    Plants and soils act as major sinks for the destruction of tropospheric ozone, especially during daylight hours when plant stomata open and are thought to provide the dominant pathway for the uptake of ozone. The present study, part of the California Ozone Deposition Experiment, compares predictions of the regional acid deposition model ozone surface conductance module with surface conductance data derived from eddy covariance measurements of ozone flux taken at a grape, a cotton, and a grassland site in the San Joaquin Valley of California during the summer of 1991. Results indicate that the model (which was developed to provide long-term large-area estimates for the eastern United States) significantly overpredicts the surface conductance at all times of the day for at least two important types of plant cover of the San Joaquin Valley and that it incorrectly partitions the ozone flux between transpiring and nontranspiring components of the surface at the third site. Consequently, the model either overpredicts or inaccurately represents the observed deposition velocities. Other results indicate that the presence of dew does not reduce the rate of ozone deposition, contradicting to model assumptions, and that model assumptions involving the dependency of stomata upon environmental temperature are unnecessary. The effects of measurement errors and biases, arising from the presence of the roughness sublayer and possible photochemical reactions, are also discussed. A simpler model for ozone surface deposition (at least for the San Joaquin Valley) is proposed and evaluated.

  5. Plant diversity drives soil microbial biomass carbon in grasslands irrespective of global environmental change factors.

    PubMed

    Thakur, Madhav Prakash; Milcu, Alexandru; Manning, Pete; Niklaus, Pascal A; Roscher, Christiane; Power, Sally; Reich, Peter B; Scheu, Stefan; Tilman, David; Ai, Fuxun; Guo, Hongyan; Ji, Rong; Pierce, Sarah; Ramirez, Nathaly Guerrero; Richter, Annabell Nicola; Steinauer, Katja; Strecker, Tanja; Vogel, Anja; Eisenhauer, Nico

    2015-11-01

    Soil microbial biomass is a key determinant of carbon dynamics in the soil. Several studies have shown that soil microbial biomass significantly increases with plant species diversity, but it remains unclear whether plant species diversity can also stabilize soil microbial biomass in a changing environment. This question is particularly relevant as many global environmental change (GEC) factors, such as drought and nutrient enrichment, have been shown to reduce soil microbial biomass. Experiments with orthogonal manipulations of plant diversity and GEC factors can provide insights whether plant diversity can attenuate such detrimental effects on soil microbial biomass. Here, we present the analysis of 12 different studies with 14 unique orthogonal plant diversity × GEC manipulations in grasslands, where plant diversity and at least one GEC factor (elevated CO2 , nutrient enrichment, drought, earthworm presence, or warming) were manipulated. Our results show that higher plant diversity significantly enhances soil microbial biomass with the strongest effects in long-term field experiments. In contrast, GEC factors had inconsistent effects with only drought having a significant negative effect. Importantly, we report consistent non-significant effects for all 14 interactions between plant diversity and GEC factors, which indicates a limited potential of plant diversity to attenuate the effects of GEC factors on soil microbial biomass. We highlight that plant diversity is a major determinant of soil microbial biomass in experimental grasslands that can influence soil carbon dynamics irrespective of GEC. PMID:26118993

  6. Following The Money: Characterizing the Dynamics of Microbial Ecosystems and Labile Organic Matter in Grassland Soils

    NASA Astrophysics Data System (ADS)

    Herbert, B. E.; McNeal, K. S.

    2006-12-01

    The dynamics of soil microbial ecosystems and labile fractions of soil organic matter in grasslands have important implications for the response of these critical ecosystems to perturbations. Organic, inorganic and genetic biomarkers in the solid (e.g. lipids, microbial DNA), liquid (e.g. porewater ions) or gaseous phases (e.g. carbon dioxide) have been used to characterize carbon cycling and soil microbial ecology. These proxies are generally limited in the amount of temporal information that they can provide (i.e., solid-phase proxies) or the amount of specific information they can provide about carbon sources or microbial community processes (e.g. inorganic gases). It is the aim of this research to validate the use of soil volatile organic carbon emissions (VOCs) as useful indicators of subsurface microbial community shifts and processes as a function of ecosystem perturbations. We present results of method validation using laboratory microcosm, where VOC metabolites as characterized by gas chromatography and mass spectrometry (GC-MS), were related to other proxies including carbon dioxide (CO2) via infra-red technology, and microbial community shifts as measured by Biolog© and fatty acid methyl ester (FAME) techniques. Experiments with soil collected from grasslands along the coastal margin region in southern Texas were preformed where environmental factors such as soil water content, soil type, and charcoal content are manipulated. Results indicate that over fifty identifiable VOC metabolites are produced from the soils, where many (~15) can be direct indicators of microbial ecology. Principle component analysis (PCA) evidences these trends through similar cluster patterns for the VOC results, the Biolog© results, and FAME. Regression analysis further shows that VOCs are significant (p < 0.05) indicators of microbial stress. Our results are encouraging that characterizing VOCs production in grassland soils are easy to measure, relatively inexpensive method

  7. Contingenet Productivity Responses to More Extreme Rainfall Regimes Across a Grassland Biome

    NASA Astrophysics Data System (ADS)

    Heisler-White, J. L.; Knapp, A.; Collins, S.; Blair, J.; Kelly, E.

    2008-12-01

    Climate models predict, and empirical evidence confirms, that more extreme precipitation regimes are occurring in tandem with warmer atmospheric temperatures. These more extreme rainfall patterns are characterized by increased event size separated by longer within season drought periods, and represent novel climatic conditions whose consequences for different ecosystem types are largely unknown. The focus of this talk will be the impacts of extreme rainfall events on soil water content and ecosystem function, and we will present results from experimental manipulations of rainfall in four native grassland sites within the Great Plains Region of North America (USA). Along this precipitation-productivity gradient, our results suggest strong sensitivity to more extreme growing season rainfall regimes, with responses of aboveground net primary productivity (ANPP) contingent on mean soil water levels for different grassland types. At the mesic end of the gradient (tallgrass prairie), longer dry intervals between events led to extended periods of below-average soil water content, increased plant water stress and a reduction in ANPP. The opposite response occurred at the dry end (semi-arid grasslands), where a shift to fewer, but larger, events increased periods of above-average soil water content, reduced seasonal plant water stress and resulted in an increase in ANPP. These results highlight the inherent complexity in predicting how terrestrial ecosystem will respond to forecast novel climate conditions as well as the difficulties in extending inferences from single site experiments across biomes. Even with no change in annual precipitation amount, ANPP responses in a relatively uniform physiographic region differed in both magnitude and direction in response to within season changes in rainfall event size/frequency. From a mechanistic perspective, we believe that these contingent responses reflect strikingly different consequences for soil water content as a result of

  8. Constraints on tree seedling establishment in montane grasslands of the Valles Caldera, New Mexico.

    PubMed

    Coop, Jonathan D; Givnish, Thomas J

    2008-04-01

    Montane and subalpine grasslands are prominent, but poorly understood, features of the Rocky Mountains. These communities frequently occur below reversed tree lines on valley floors, where nightly cold air accumulation is spatially coupled with fine soil texture. We used field experiments to assess the roles of minimum temperature, soil texture, grass competition, and ungulate browsing on the growth, photosynthetic performance, and survival of transplanted ponderosa pine (Pinus ponderosa) seedlings at 32 sites straddling such reversed tree lines in the Valles Caldera National Preserve (VCNP) of the Jemez Mountains, New Mexico (USA). Seedling growth increased most strongly with increasing nighttime minimum temperatures away from the valley bottoms; seedlings experiencing the coldest temperatures on the caldera floor exhibited stunted needles and often no measurable height growth. Based on the chlorophyll fluorescence ratios PhiPSII and Fv/Fm, we found that low minimum temperatures, low soil moisture, and fine soil texture all contributed to photoinhibition. Neighboring herbs had only minor negative effects on seedlings. We found no effect of ungulates, but golden-mantled ground squirrels (Spermophilus lateralis) caused substantial seedling mortality. Second-year seedling survival was highest on sandy soils, and third-year survival was highest at sites with higher minimum temperatures. We conclude that differential tree seedling establishment driven by low minimum temperatures in the valley bottoms is the primary factor maintaining montane grasslands of the VCNP, although this process probably operated historically in combination with frequent surface fire to set the position of the tree line ecotone. As at alpine tree lines, reversed tree lines bordering montane and subalpine grasslands can represent temperature-sensitive boundaries of the tree life form. PMID:18481534

  9. The responses of soil respiration to nitrogen addition in a temperate grassland in northern China.

    PubMed

    Luo, Qinpu; Gong, Jirui; Zhai, Zhanwei; Pan, Yan; Liu, Min; Xu, Sha; Wang, Yihui; Yang, Lili; Baoyin, Taoge-Tao

    2016-11-01

    Anthropogenic activities have increased nitrogen (N) inputs to grassland ecosystems. Knowledge of the impact of soil N availability on soil respiration (RS) is critical to understand soil carbon balances and their responses to global climate change. A 2-year field experiment was conducted to evaluate the response of RS to soil mineral N in a temperate grassland in northern China. RS, abiotic and biotic factors, and N mineralization were measured in the grassland, at rates of N addition ranging from 0 to 25gNm(-2)yr(-1). Annual and dormant-season RS ranged from 241.34 to 283.64g C m(-2) and from 61.34 to 83.84g C m(-2) respectively. High N application significantly increased RS, possibly due to increased root biomass and increased microbial biomass. High N treatment significantly increased soil NO3-N and inorganic N content compared with the control. The ratio of NO3-N to NH4-N and the N mineralization rate were significantly positively correlated with RS, but NH4-N was not correlated or negatively correlated with RS during the growing season. The temperature sensitivity of RS (Q10) was not significantly affected by N levels, and ranged from 1.90 to 2.20, but decreased marginally significantly at high N. RS outside the growing season is an important component of annual RS, accounting for 25.0 to 29.6% of the total. High N application indirectly stimulated RS by increasing soil NO3-N and net nitrification, thereby eliminating soil N limitations, promoting ecosystem productivity, and increasing soil CO2 efflux. Our results show the importance of distinguishing between NO3-N and NH4-N, as their impact on soil CO2 efflux differed. PMID:27396319

  10. Floristic and structural patterns in South Brazilian coastal grasslands.

    PubMed

    Menezes, Luciana S; Müller, Sandra C; Overbeck, Gerhard E

    2015-01-01

    The natural vegetation of Southern Brazil's coastal region includes grasslands formations that are poorly considered in conservation policy, due to the lack of knowledge about these systems. This study reports results from a regional-scale survey of coastal grasslands vegetation along a 536 km gradient on southern Brazil. We sampled 16 sites along the coastal plain with 15 plots (1 m²) per site. All sites were grazed by cattle. We estimated plant species cover, vegetation height, percentage of bare soil, litter and manure, and classified species according to their growth forms. We found 221 species, 14 of them exotic and two threatened. The prostate grasses: Axonopus aff.affinis, Paspalum notatum and P. pumilumwere among the most important species. Prostrate graminoids species represented the most important vegetation cover, followed by cespitose grasses. Vegetation height, bare soil, litter and manure were similar among all areas, highlighting the homogeneity of sampling sites due to similar management. In comparison to other grasslands formations in Southern Brazil, the coastal grasslands presented rather low species richness. The presence of high values for bare soil at all sampling sites indicates the need to discuss management practices in the region, especially with regard to the intensity of livestock grazing. PMID:26628017

  11. Area requirements of grassland birds: a regional perspective

    USGS Publications Warehouse

    Johnson, D.H.; Igl, L.D.

    2001-01-01

    Area requirements of grassland birds have not been studied except in tallgrass prairie. We studied the relation between both species-occurrence and density and patch size by conducting 699 fixed-radius point counts of 15 bird species on 303 restored grassland areas in nine counties in four northern Great Plains states. Northern Harrier (Circus cyaneus), Sedge Wren (Cistothorus platensis), Clay-colored Sparrow (Spizella pallida), Grasshopper Sparrow (Ammodramus savannarum), Baird's Sparrow (Ammodramus bairdii), Le Conte's Sparrow (Ammodramus leconteii), and Bobolink (Dolichonyx oryzivorus) were shown to favor larger grassland patches in one or more counties. Evidence of area sensitivity was weak or ambivalent for Eastern Kingbird (Tyrannus tyrannus), Common Yellowthroat (Geothlypis trichas), Savannah Sparrow (Passerculus sandwichensis), and Western Meadowlark (Sturnella neglecta). Red-winged Blackbirds (Agelaius phoeniceus) preferred larger patches in some counties, and smaller patches in others. Mourning Doves (Zenaida macroura) and Brown-headed Cowbirds (Molothrus ater) tended to favor smaller grassland patches. Three species showed greater area sensitivity in counties where each species was more common. Five species demonstrated some spatial pattern of area sensitivity, either north to south or east to west. This study demonstrates the importance of replication in space; results from one area may not apply to others because of differences in study design, analytical methods, location relative to range of the species, and surrounding landscapes.

  12. NITROGEN POOLS AND FLUXES IN GRASSLAND SOILS SEQUESTERING CARBON

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Carbon sequestration in agricultural, forest, and grassland soils has been promoted as a means by which substantial amounts of CO2 may be removed from the atmosphere, but few studies have evaluated the associated impacts on changes in soil N or net global warming potential (GWP). The purpose of this...

  13. Area requirements of grassland birds: A regional perspective

    USGS Publications Warehouse

    Johnson, Douglas H.; Igl, Lawrence D.

    2001-01-01

    Area requirements of grassland birds have not been studied except in tallgrass prairie. We studied the relation between both species-occurrence and density and patch size by conducting 699 fixed-radius point counts of 15 bird species on 303 restored grassland areas in nine counties in four northern Great Plains states. Northern Harrier (Circus cyaneus), Sedge Wren (Cistothorus platensis), Clay-colored Sparrow (Spizella pallida), Grasshopper Sparrow (Ammodramus savannarum), Baird's Sparrow (Ammodramus bairdii), Le Conte's Sparrow (Ammodramus leconteii), and Bobolink (Dolichonyx oryzivorus) were shown to favor larger grassland patches in one or more counties. Evidence of area sensitivity was weak or ambivalent for Eastern Kingbird (Tyrannus tyrannus), Common Yellowthroat (Geothlypis trichas), Savannah Sparrow (Passerculus sandwichensis), and Western Meadowlark (Sturnella neglecta). Red-winged Blackbirds (Agelaius phoeniceus) preferred larger patches in some counties, and smaller patches in others. Mourning Doves (Zenaida macroura) and Brown-headed Cowbirds (Molothrus ater) tended to favor smaller grassland patches. Three species showed greater area sensitivity in counties where each species was more common. Five species demonstrated some spatial pattern of area sensitivity, either north to south or east to west. This study demonstrates the importance of replication in space; results from one area may not apply to others because of differences in study design, analytical methods, location relative to range of the species, and surrounding landscapes.

  14. GRAZING EFFECTS ON MICROTOPOGRAPHY IN A DESERT GRASSLAND

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We measured the effects of short-term intense grazing by domestic cattle on the microtopography of a black-grama grass Bouteloua eriopoda dominated desert grasslands. Plots were grazed during winter or summer for 24-36 hours by 20-40 yearlings in 1995 and 1996. Soil microtopography was measured wi...

  15. Complexity in rodent community responses to grassland-shrubland transitions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    It is believed that the abundance and diversity of Chihuahuan Desert rodents increases with shrub encroachment accompanying desertification although grassland specialist species decline with loss of perennial grasses. It has been reported, however, that a suite of biotic-abiotic interactions may inf...

  16. Regional dynamics of grassland change in the western Great Plains

    USGS Publications Warehouse

    Drummond, M.A.

    2007-01-01

    This paper examines the contemporary land-cover changes in two western Great Plains ecoregions between 1973 and 2000. Agriculture and other land uses can have a substantial effect on grassland cover that varies regionally depending on the primary driving forces of change. In order to better understand change, the rates, types, and causes of land conversion were examined for 1973, 1980, 1986, 1992, and 2000 using Landsat satellite data and a statistical sampling strategy. The overall estimated rate of land-cover change between 1973 and 2000 was 7.4% in the Northwestern Great Plains and 11.5% in the Western High Plains. Trends in both ecoregions have similarities, although the dynamics of change differ temporally depending on driving forces. Between 1973 and 1986, grassland cover declined when economic opportunity drove an expansion of agriculture. Between 1986 and 2000, grassland expanded as public policy and a combination of socioeconomic factors drove a conversion from agriculture to grassland. ?? 2007 Copyright by the Center for Great Plains Studies, University of Nebraska-Lincoln.

  17. Life cycle greenhouse gas impacts of grassland management practice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biomass from conservation and dedicated grasslands could be an important feedstock for biofuels. Estimating the carbon (C) intensity of biofuel production pathways is important in order to meet greenhouse gas (GHG) targets set by government policy. Management decisions made during feedstock producti...

  18. Plant species composition and biofuel yields of conservation grasslands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Marginal croplands, such as those in the Conservation Reserve Program (CRP), have been suggested as a source of biomass for biofuel production. However, little is known about the composition of plant species on these conservation grasslands or their potential for ethanol production. Our objective w...

  19. Evaluation of SPOT imagery for the estimation of grassland biomass

    NASA Astrophysics Data System (ADS)

    Dusseux, P.; Hubert-Moy, L.; Corpetti, T.; Vertès, F.

    2015-06-01

    In many regions, a decrease in grasslands and change in their management, which are associated with agricultural intensification, have been observed in the last half-century. Such changes in agricultural practices have caused negative environmental effects that include water pollution, soil degradation and biodiversity loss. Moreover, climate-driven changes in grassland productivity could have serious consequences for the profitability of agriculture. The aim of this study was to assess the ability of remotely sensed data with high spatial resolution to estimate grassland biomass in agricultural areas. A vegetation index, namely the Normalized Difference Vegetation Index (NDVI), and two biophysical variables, the Leaf Area Index (LAI) and the fraction of Vegetation Cover (fCOVER) were computed using five SPOT images acquired during the growing season. In parallel, ground-based information on grassland growth was collected to calculate biomass values. The analysis of the relationship between the variables derived from the remotely sensed data and the biomass observed in the field shows that LAI outperforms NDVI and fCOVER to estimate biomass (R2 values of 0.68 against 0.30 and 0.50, respectively). The squared Pearson correlation coefficient between observed and estimated biomass using LAI derived from SPOT images reached 0.73. Biomass maps generated from remotely sensed data were then used to estimate grass reserves at the farm scale in the perspective of operational monitoring and forecasting.

  20. An efficient sampling protocol for sagebrush/grassland monitoring

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Monitoring the health and condition of rangeland vegetation can be very time consuming and costly. An efficiency but rigorous sampling protocol is needed for monitoring sagebrush/grassland vegetation. A randomized sampling protocol was presented for geo-referenced, nadir photographs acquired using...

  1. ADAPTIVE MANAGEMENT IN GRASSLANDS TO IMPROVE WATER QUALITY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grassland management practices may influence nutrient concentrations in streams, both base flow and storm flow, when nutrients are applied at recommended rates. We examined the extent to which nutrients (phosphorus (P) and nitrogen (N)) were present (from 1999 to 2004) in both soluble and particul...

  2. [CO2 fluxes in mire and grassland on Ruoergai plateau].

    PubMed

    Wang, De-Xuan; Song, Chang-Chun; Wang, Yi-Yong; Zhao, Zhi-Chun

    2008-02-01

    With closed chamber and GC technique, a comparative study was conducted on the CO2 fluxes in mire and grassland on Ruoergai plateau during the plant growth period in 2003-2005. The results showed that the mean value of the CO2 fluxes in the three years was 203.22 mg x m(-2) x h(-1) in mire and 323.03 mg x m(-2) x h(-1) in grassland, with the former being only about 60% of the latter. The perennially water-logging of mire limited the decomposition of plant residues, roots and organic substances, resulting in a lower CO2 flux in mire than in grassland. The seasonal changes of CO2 fluxes in mire and grassland were positively correlated with air temperature, the peak value being usually appeared in July or August, and the diurnal changes of the CO2 fluxes were also positively correlated with air temperature, the peak value being usually appeared between 11:00 and 17:00. The CO2 fluxes had a higher correlation with the soil temperature at the depth of 5 cm than at the depths of 10 cm and 15 cm. PMID:18464633

  3. Plant species composition and biofuel yields of conservation grasslands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Conservation Reserve Program (CRP) grasslands are a critical component for reaching the billion annual tons of biomass feedstock production goal. Few studies have determined the capacity of CRP land for biomass production or biofuel quality. The objective of this study was to assess the potential of...

  4. Predicting parameters of degradation succession processes of Tibetan Kobresia grasslands

    NASA Astrophysics Data System (ADS)

    Lin, L.; Li, Y. K.; Xu, X. L.; Zhang, F. W.; Du, Y. G.; Liu, S. L.; Guo, X. W.; Cao, G. M.

    2015-08-01

    In the past two decades, increasing human activity (i.e., overgrazing) in the Tibetan Plateau has strongly influenced plant succession processes, resulting in the degradation of alpine grasslands. Therefore, it is necessary to diagnose the degree of degradation to enable implementation of appropriate management for sustainable exploitation and protection of alpine grasslands. Here, we investigated environmental factors and plant functional group quantity factors (PFGs) during the alpine grassland succession processes. Principal component analysis (PCA) was used to identify the parameters indicative of degradation. We divided the entire degradation process into six stages. PFG types shifted from rhizome bunch grasses to rhizome plexus and dense plexus grasses during the degradation process. Leguminosae and Gramineae plants were replaced by Sedges during the advanced stages of degradation. The PFGs were classified into two reaction groups: the grazing-sensitive group, containing Kobresia humilis Mey, and Gramineae and Leguminosae plants, and the grazing-insensitive group, containing Kobresia pygmaea Clarke. The first group was correlated with live root biomass in the surface soil (0-10 cm), whereas the second group was strongly correlated with mattic epipedon thickness and K. pygmaea characteristics. The degree of degradation of alpine meadows may be delineated by development of mattic epipedon and PFG composition. Thus, meadows could be easily graded and their use adjusted based on our scaling system, which would help prevent irreversible degradation of important grasslands. Because relatively few environmental factors are investigated, this approach can save time and labor to formulate a conservation management plan for degraded alpine meadows.

  5. Predicting parameters of degradation succession processes of Tibetan Kobresia grasslands

    NASA Astrophysics Data System (ADS)

    Lin, L.; Li, Y. K.; Xu, X. L.; Zhang, F. W.; Du, Y. G.; Liu, S. L.; Guo, X. W.; Cao, G. M.

    2015-11-01

    In the past two decades, increasing human activity (i.e., overgrazing) in the Tibetan Plateau has strongly influenced plant succession processes, resulting in the degradation of alpine grasslands. Therefore, it is necessary to diagnose the degree of degradation to enable implementation of appropriate management for sustainable exploitation and protection of alpine grasslands. Here, we investigated environmental factors and plant functional group (PFG) quantity factors during the alpine grassland succession processes. Principal component analysis (PCA) was used to identify the parameters indicative of degradation. We divided the entire degradation process into six stages. PFG types shifted from rhizome bunchgrasses to rhizome plexus and dense-plexus grasses during the degradation process. Leguminosae and Gramineae plants were replaced by sedges during the advanced stages of degradation. The PFGs were classified into two reaction groups: the grazing-sensitive group, containing Kobresia humilis Mey, and Gramineae and Leguminosae plants, and the grazing-insensitive group, containing Kobresia pygmaea Clarke. The first group was correlated with live root biomass in the surface soil (0-10 cm), whereas the second group was strongly correlated with mattic epipedon thickness and K. pygmaea characteristics. The degree of degradation of alpine meadows may be delineated by development of mattic epipedon and PFG composition. Thus, meadows could be easily graded and their use adjusted based on our scaling system, which would help prevent irreversible degradation of important grasslands. Because relatively few environmental factors are investigated, this approach can save time and labor to formulate a conservation management plan for degraded alpine meadows.

  6. Ecological dynamic model of grassland and its practical verification.

    PubMed

    Zeng, Xiaodong; Wang, Aihui; Zhao, Gang; Shen, Samuel S P; Zeng, Xubin; Zeng, Qingcun

    2005-02-01

    Based on the physico-biophysical considerations, mathematical analysis and some approximate formulations generally adopted in meteorology and ecology, an ecological dynamic model of grassland is developed. The model consists of three interactive variables, i.e. the biomass of living grass, the biomass of wilted grass, and the soil wetness. The major biophysical processes are represented in parameterization formulas, and the model parameters can be determined inversely by using the observational climatological and ecological data. Some major parameters are adjusted by this method to fit the data (although incomplete) in the Inner Mongolia grassland, and other secondary parameters are estimated through sensitivity studies. The model results are well agreed with reality, e.g., (i) the maintenance of grassland requires a minimum amount of annual precipitation (approximately 300 mm); (ii) there is a significant relationship between the annual precipitation and the biomass of living grass; and (iii) the overgrazing will eventually result in desertification. A specific emphasis is put on the shading effect of the wilted grass accumulated on the soil surface. It effectively reduces the soil surface temperature and the evaporation, hence benefits the maintenance of grassland and the reduction of water loss in the soil. PMID:15844356

  7. The Influence of Encroaching Woodland on Grassland Enzymatic Activities

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grass-dominated ecosystems around the world are experiencing woody plant invasion due to human land uses. Vast regions in southern Texas have been transformed from open grasslands to subtropical thorn woodlands during the past 150 yrs. The assumption is that the soil microbial activity in the remain...

  8. Efficiency of phosphorus cycling in different grassland systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The reliance of dairy farms on grassland is currently expanding, particularly in areas where confined operations have recently predominated. At the same time, some pasture based dairy systems, such as those found in New Zealand, are turning toward seasonal confinement of herds for production and eve...

  9. Bird Use of Grassland Habitat Patches at a Military Airfield

    EPA Science Inventory

    In light of reported declines in grassland bird populations in North America, information about their use of airfield habitats can help inform management decisions in the context of conflicting objectives of minimizing wildlife-aircraft collisions and helping to conserve grasslan...

  10. Water, temperature, and defoliation effects on perennial grassland respiration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Changes in respiration can have a profound effect on ecosystem C balance. This talk will present results from eddy covariance studies describing environment and management effects on ecosystem C flux from cool- and warm-season perennial grasslands. In addition, stable C isotope studies that partitio...

  11. Native American impacts on fire regimes of the California coastal ranges

    USGS Publications Warehouse

    Keeley, J.E.

    2002-01-01

    Aim: Native American burning impacts on California shrubland dominated landscapes are evaluated relative to the natural lightning fire potential for affecting landscape patterns. Location: Focus was on the coastal ranges of central and southern California. Methods: Potential patterns of Indian burning were evaluated based upon historical documents, ethnographic accounts, archaeological records and consideration of contemporary land management tactics. Patterns of vegetation distribution in this region were evaluated relative to environmental factors and the resilience of the dominant shrub vegetation to different fire frequencies. Results: Lightning fire frequency in this region is one of the lowest in North America and the density of pre-Columbian populations was one of the highest. Shrublands dominate the landscape throughout most of the region. These woody communities have weak resilience to high fire frequency and are readily displaced by annual grasses and forbs under high fire frequency. Intact shrublands provided limited resources for native Americans and thus there was ample motivation for using fire to degrade this vegetation to an open mosaic of shrubland/grassland, not unlike the agropastoral modification of ecologically related shrublands by Holocene peoples in the Mediterranean Basin. Alien-dominated grasslands currently cover approximately one-quarter of the landscape and less than 1% of these grasslands have a significant native grass presence. Ecological studies in the Californian coastal ranges have failed to uncover any clear soil or climate factors explaining grassland and shrubland distribution patterns. Main conclusions: Coastal ranges of California were regions of high Indian density and low frequency of lightning fires. The natural vegetation dominants on this landscape are shrubland vegetation that often form dense impenetrable stands with limited resources for Native Americans. Natural fire frequencies are not high enough to maintain these

  12. Rapid transfer of photosynthetic carbon through the plant-soil system in differently managed grasslands

    NASA Astrophysics Data System (ADS)

    de Deyn, G. B.; Quirk, H.; Oakley, S.; Ostle, N.; Bardgett, R. D.

    2011-02-01

    Plant-soil interactions are central to short-term carbon (C) cycling through the rapid transfer of recently assimilated C from plant roots to soil biota. In grassland ecosystems, changes in C cycling are likely to be influenced by land use and management that changes vegetation and the associated soil microbial communities. Here we tested whether changes in grassland vegetation composition resulting from management for plant diversity influences short-term rates of C assimilation, retention and transfer from plants to soil microbes. To do this, we used an in situ 13C-CO2 pulse-labeling approach to measure differential C uptake among different plant species and the transfer of the plant-derived 13C to key groups of soil microbiota across selected treatments of a long-term plant diversity grassland restoration experiment. Results showed that plant taxa differed markedly in the rate of 13C assimilation and retention: uptake was greatest and retention lowest in Ranunculus repens, and assimilation was least and retained longest in mosses. Incorporation of recent plant-derived 13C was maximal in all microbial phosopholipid fatty acid (PLFA) markers at 24 h after labeling. The greatest incorporation of 13C was in the PLFA 16:1ω5, a marker for arbuscular mycorrhizal fungi (AMF), while after one week most 13C was retained in the PLFA 18:2ω6,9 which is indicative of assimilation of plant-derived 13C by saprophytic fungi. Our results of 13C assimilation, transfer and retention within plant species and soil microbes were consistent across management treatments. Overall, our findings suggest that changes in vegetation and soil microbial composition resulting from differences in long-term grassland management will affect short-term cycling of photosynthetic C, but that restoration management does not alter the short-term C uptake and transfer within plant species and within key groups of soil microbes. Moreover, across all treatments we found that plant-derived C is rapidly

  13. Legacy effects of grassland management on soil carbon to depth.

    PubMed

    Ward, Susan E; Smart, Simon M; Quirk, Helen; Tallowin, Jerry R B; Mortimer, Simon R; Shiel, Robert S; Wilby, Andrew; Bardgett, Richard D

    2016-08-01

    The importance of managing land to optimize carbon sequestration for climate change mitigation is widely recognized, with grasslands being identified as having the potential to sequester additional carbon. However, most soil carbon inventories only consider surface soils, and most large-scale surveys group ecosystems into broad habitats without considering management intensity. Consequently, little is known about the quantity of deep soil carbon and its sensitivity to management. From a nationwide survey of grassland soils to 1 m depth, we show that carbon in grassland soils is vulnerable to management and that these management effects can be detected to considerable depth down the soil profile, albeit at decreasing significance with depth. Carbon concentrations in soil decreased as management intensity increased, but greatest soil carbon stocks (accounting for bulk density differences), were at intermediate levels of management. Our study also highlights the considerable amounts of carbon in subsurface soil below 30 cm, which is missed by standard carbon inventories. We estimate grassland soil carbon in Great Britain to be 2097 Tg C to a depth of 1 m, with ~60% of this carbon being below 30 cm. Total stocks of soil carbon (t ha(-1) ) to 1 m depth were 10.7% greater at intermediate relative to intensive management, which equates to 10.1 t ha(-1) in surface soils (0-30 cm), and 13.7 t ha(-1) in soils from 30 to 100 cm depth. Our findings highlight the existence of substantial carbon stocks at depth in grassland soils that are sensitive to management. This is of high relevance globally, given the extent of land cover and large stocks of carbon held in temperate managed grasslands. Our findings have implications for the future management of grasslands for carbon storage and climate mitigation, and for global carbon models which do not currently account for changes in soil carbon to depth with management. PMID:26854892

  14. Phosphorus and Nitrogen Co-Limit Global Grassland Productivity

    NASA Astrophysics Data System (ADS)

    Fay, P. A.; Prober, S. M.; Harpole, W. S.; Knops, J. M. H.; Bakker, J. D.; Borer, E. T.; MacDougall, A. S.; Seabloom, E. W.; Wragg, P. D.; Lind, E. M.

    2014-12-01

    Terrestrial ecosystem primary productivity has been considered to be primarily nitrogen (N) - limited, but may be co-limited by phosphorus (P), and possibly by potassium and micronutrients (K+m). The frequency, magnitude, and global extent of single or multiple nutrient limitations are poorly understood in natural systems, but can influence how anthropogenic nutrient enrichment affects ecosystem productivity and provisioning of ecosystem goods and services. We examined the occurrence and magnitude of nutrient limitation of aboveground net primary productivity (ANPP) by N, P, and K+m at 42 grassland sites on five continents in the Nutrient Network (https://www.nutnet.umn.edu). N, P, and K+m were factorially applied annually in a randomized block design at all sites. ANPP was measured annually for 3 to 5 years by clipping and weighing standing aboveground biomass. We found clear evidence for nutrient limitation of ANPP in these grasslands. Across all sites and years, the combined addition of N and P increased ANPP by 39% over controls, more than occurred if either was added alone (N: 18%; P: 9%), suggesting co-limitation of ANPP by both nutrients. Co-limitation by other nutrient combinations was not detected. At individual sites, ANPP limitation was most often alleviated by adding N and P together, but K+m addition alleviated ANPP limitation at three sites. Also, site-level limitation of ANPP by any one nutrient was positively correlated (R2 0.07 to 0.21) with limitation by other single or multiple nutrients, suggesting generalized multiple nutrient limitation. We found no differences in nutrient limitation of ANPP among continents or management practices, between native and previously cultivated grasslands, or with site soil properties or climate. These novel patterns of nutrient limitation of ANPP in grasslands around the global contradict the long-held idea that N is the primary nutrient limiting productivity in these ecosystems. Grasslands are globally important

  15. Slug responses to grassland cutting and fertilizer application under plant functional group removal

    NASA Astrophysics Data System (ADS)

    Everwand, Georg; Scherber, Christoph; Tscharntke, Teja

    2013-04-01

    Current studies on trophic interactions in biodiversity experiments have largely relied on artificially sown gradients in plant diversity, but removal experiments with their more natural plant community composition are more realistic. Slugs are a major part of the invertebrate herbivore community, with some species being common pests in agriculture. We therefore investigated how strongly slugs are influenced by grassland management, plant biodiversity and composition. Here we analysed the effects of cutting frequency, fertilizer application and plant functional group composition on slug densities and their contribution to herbivory on Rumex acetosa in a removal experiment within a >100-year old grassland in Northern Germany. The experiment was laid out as a Latin rectangle with full factorial combinations of (i) plant functional group removal (3 levels) using herbicides, (ii) fertilizer application (2 levels) and (iii) cutting frequency (2 levels). The resulting 12 treatment combinations were replicated 6 times, resulting in 72 plots. We collected a total of 1020 individuals belonging to three species Arion distinctus (60.4% of individuals), Deroceras reticulatum (34.7%) and Arion lusitanicus (4.9%) using a cover board technique and additionally measured herbivore damage to R. acetosa. We found the highest slug abundance on plots with a low cutting frequency and high food resource availability (increased cover of forbs and taller vegetation). Fertilizer application had no significant effect on slug abundance, but caused higher herbivore damage to on R. acetosa, possibly as a result of increased tissue quality. The negative effect of higher cutting frequency on slug abundance was lowest in control plots with their naturally developed graminoid-forb communities (cutting reduced slug density by 6% in the control vs. 29% in herbicide plots). Our experiments therefore support the idea that more natural plant species compositions reduce the impact of disturbances (e

  16. Organic carbon pools in Austrian permanent grassland soils

    NASA Astrophysics Data System (ADS)

    Foldal, Cecilie B.; Bohner, Andreas; Jandl, Robert

    2015-04-01

    Grasslands are known to store large amounts of carbon (C) and land use and farming management practices do have an impact on the quantity of soil organic carbon (SOC) as well as the biomass production. In the period from 1995 to 2010 the total area for agriculture and forest production in Austria declined and the most severe changes took place in grassland areas where more than 25% of the land used for extensive or intensive grass production was lost due to land use change, abandonment or sealing. In this study, we investigated the organic carbon (OC) stock at three different locations representative for Austrian mountainous grassland regions. At each location we compared the above- and belowground (down to 50 cm depth) C stocks at two adjacent but differently managed sites in order to see how management intensity affects the OC pools in permanent grassland soils. Mean OC stocks ranged from 8.2 to 15.7 kg per m² whereby approximately 95% was allocated belowground. In general, we found a significant positive correlation between the SOC content and biomass production at all three locations. Mean root biomass content ranged from 0.205 to 1.950 kg per m². 78.2 to 93.2% of root biomass was concentrated in the top 10 cm of the soil. Management had a significant influence on the SOC content as well as on above- and belowground biomass production. We conclude that permanent grassland soils represent a large sink for OC. Root biomass and SOC content respond to management intensity.

  17. The ecological consequences of biochar application to grasslands.

    NASA Astrophysics Data System (ADS)

    Jeffery, S.; Memelink, I.; Voorde, T. V.; Mommer, L.; Bezemer, M.; Groenigen, J. W. V.

    2014-12-01

    Biochar application to soil is widely proposed as a means of sequestering carbon (C) in soils to aid climate change mitigation while concurrently improving crop yields. Other benefits include issues such as waste disposal. While there are numerous studies investigating the effects of biochar application to agricultural systems, the impact of application to grasslands is still an understudied area. We studied the impact of biochar application on aboveground (plant) and belowground community composition and effects on the functional repertoire of soil microbial communities under a semi-natural grassland in the Netherlands. We investigated the impacts and the underlying mechanisms behind observed effects. We found that biochar application to soil caused a transient competitive effect, enhancing legumes biomass when compared to grasses and forbs. Biological nitrogen fixation was shown to increase following biochar application, with potassium (K) introduced with the biochar the most likely reason. Furthermore, we found lasting effects on the functional repertoire of the soil microbial communities after three seasons. Different responses to C substrate additions of field soil under laboratory conditions indicated lasting effects on C utilisation of soil microbial communities following biochar application. Stable isotope techniques showed pyrolysis to increase the predicted C residence time in soil from ~30 years to >520 years as well as reducing N availability by ~70% compared to the unpyrolysed feedstock. Combined, these results suggest biochar production and application can be used to control the nutrient status of grasslands while concurrently storing C for extended periods. These results have implications for grassland management, including grazed pastures which may benefit from increased BNF. Further they demonstrate the potential of grasslands for climate change mitigation through increased C storage following biochar application.

  18. [Spatiotemporal pattern of alpine grassland productivity in Qiangtang Plateau].

    PubMed

    Wang, Jing-Sheng; Zhang, Xian-Zhou; Zhao, Yu-Ping; Qin, Si-Guo; Wu, Jian-Shuang

    2010-06-01

    Based on the meteorological data and remote sensing data, and by using vegetation-climate comprehensive model and CASA model, this paper analyzed the climate change trend and the spatiotemporal pattern of alpine grassland potential and actual net primary productivity (NPP) in Qiantang Plateau. In 1955-2004, the mean annual temperature and annual cumulated precipitation in the Plateau increased by 1.37 degrees C and 63 mm, respectively. The climate in the central and eastern parts of the Plateau became warmer and wetter, whereas it was warmer and dryer in the western part. However, the regional climate change did not yet result in grassland degradation. The mean potential NPP of alpine grassland was in the order of eastern part > central part > western part. From 1982 to 2004, the potential NPP in the central part had the largest increment (0.55 t x hm(-2) x a(-1)), followed by in the eastern part (0.51 t x hm(-2) x a(-1)) and western part (0.21 t x hm(-2) x a(-1)), which was consequent with the spatiotemporal pattern of climate change in the study area. In contrast, the actual NPP in the eastern, central, and western parts in the past two decades was -0.19, -0.03, and 0.20 t x hm(-2) x a(-1), respectively. Overgrazing was the main reason of grassland degradation in the central and eastern parts, and the central part was the key layout area for the implement of 'grazing withdrawal and management of grassland' project. PMID:20873612

  19. Remote sensing for grassland management in the arid Southwest

    USGS Publications Warehouse

    Marsett, R.C.; Qi, J.; Heilman, P.; Biedenbender, S.H.; Watson, M.C.; Amer, S.; Weltz, M.; Goodrich, D.; Marsett, R.

    2006-01-01

    We surveyed a group of rangeland managers in the Southwest about vegetation monitoring needs on grassland. Based on their responses, the objective of the RANGES (Rangeland Analysis Utilizing Geospatial Information Science) project was defined to be the accurate conversion of remotely sensed data (satellite imagery) to quantitative estimates of total (green and senescent) standing cover and biomass on grasslands and semidesert grasslands. Although remote sensing has been used to estimate green vegetation cover, in arid grasslands herbaceous vegetation is senescent much of the year and is not detected by current remote sensing techniques. We developed a ground truth protocol compatible with both range management requirements and Landsat's 30 m resolution imagery. The resulting ground-truth data were then used to develop image processing algorithms that quantified total herbaceous vegetation cover, height, and biomass. Cover was calculated based on a newly developed Soil Adjusted Total Vegetation Index (SATVI), and height and biomass were estimated based on reflectance in the near infrared (NIR) band. Comparison of the remotely sensed estimates with independent ground measurements produced r2 values of 0.80, 0.85, and 0.77 and Nash Sutcliffe values of 0.78, 0.70, and 0.77 for the cover, plant height, and biomass, respectively. The approach for estimating plant height and biomass did not work for sites where forbs comprised more than 30% of total vegetative cover. The ground reconnaissance protocol and image processing techniques together offer land managers accurate and timely methods for monitoring extensive grasslands. The time-consuming requirement to collect concurrent data in the field for each image implies a need to share the high fixed costs of processing an image across multiple users to reduce the costs for individual rangeland managers.

  20. Effects of Reproductive Experience on Central Expression of Progesterone, Oestrogen α, Oxytocin and Vasopressin Receptor mRNA in Male California Mice (Peromyscus californicus)

    PubMed Central

    Perea-Rodriguez, J. P.; Takahashi, E. Y.; Amador, T. M.; Hao, R. C.; Saltzman, W.; Trainor, B. C.

    2016-01-01

    Fatherhood in biparental mammals is accompanied by distinct neuroendocrine changes in males, involving some of the same hormones involved in maternal care. In the monogamous, biparental California mouse (Peromyscus californicus), paternal care has been linked to changes in the central and/or peripheral availability of oestrogen, progesterone, vasopressin and oxytocin, although it is not known whether these endocrine fluctuations are associated with changes in receptor availability in the brain. Thus, we compared mRNA expression of oestrogen receptor (ER)α, progesterone receptor (PR), vasopressin receptor (V1a) and oxytocin receptor (OTR) in brain regions implicated in paternal care [i.e. medial preoptic area (MPOA)], fear [i.e. medial amygdala (MeA)] and anxiety [i.e. bed nucleus of the stria terminalis (BNST)] between first-time fathers (n = 8) and age-matched virgin males (n = 7). Males from both reproductive conditions behaved paternally towards unrelated pups, whereas fathers showed significantly shorter latencies to behave paternally and less time investigating pups. Furthermore, fathers showed significantly lower PR, OTR and V1a receptor mRNA expression in the BNST compared to virgins. Fathers also showed a marginally significant (P = 0.07) reduction in progesterone receptor mRNA expression in the MPOA, although fatherhood was not associated with any other changes in receptor mRNA in the MPOA or MeA. The results of the present study indicate that behavioural and endocrine changes associated with the onset of fatherhood, and/or with cohabitation with a (breeding) female, are accompanied by changes in mRNA expression of hormone and neuropeptide receptors in the brain. PMID:25659593

  1. Migratory monarchs wintering in California experience low infection risk compared to monarchs breeding year-round on non-native milkweed.

    PubMed

    Satterfield, Dara A; Villablanca, Francis X; Maerz, John C; Altizer, Sonia

    2016-08-01

    Long-distance migration can lower infection risk for animal populations by removing infected individuals during strenuous journeys, spatially separating susceptible age classes, or allowing migrants to periodically escape from contaminated habitats. Many seasonal migrations are changing due to human activities including climate change and habitat alteration. Moreover, for some migratory populations, sedentary behaviors are becoming more common as migrants abandon or shorten their journeys in response to supplemental feeding or warming temperatures. Exploring the consequences of reduced movement for host-parasite interactions is needed to predict future responses of animal pathogens to anthropogenic change. Monarch butterflies (Danaus plexippus) and their specialist protozoan parasite Ophryocystis elektroscirrha (OE) provide a model system for examining how long-distance migration affects infectious disease processes in a rapidly changing world. Annual monarch migration from eastern North America to Mexico is known to reduce protozoan infection prevalence, and more recent work suggests that monarchs that forego migration to breed year-round on non-native milkweeds in the southeastern and south central Unites States face extremely high risk of infection. Here, we examined the prevalence of OE infection from 2013 to 2016 in western North America, and compared monarchs exhibiting migratory behavior (overwintering annually along the California coast) with those that exhibit year-round breeding. Data from field collections and a joint citizen science program of Monarch Health and Monarch Alert showed that infection frequency was over nine times higher for monarchs sampled in gardens with year-round milkweed as compared to migratory monarchs sampled at overwintering sites. Results here underscore the importance of animal migrations for lowering infection risk and motivate future studies of pathogen transmission in migratory species affected by environmental change. PMID

  2. Effects of reproductive experience on central expression of progesterone, oestrogen α, oxytocin and vasopressin receptor mRNA in male California mice (Peromyscus californicus).

    PubMed

    Perea-Rodriguez, J P; Takahashi, E Y; Amador, T M; Hao, R C; Saltzman, W; Trainor, B C

    2015-04-01

    Fatherhood in biparental mammals is accompanied by distinct neuroendocrine changes in males, involving some of the same hormones involved in maternal care. In the monogamous, biparental California mouse (Peromyscus californicus), paternal care has been linked to changes in the central and/or peripheral availability of oestrogen, progesterone, vasopressin and oxytocin, although it is not known whether these endocrine fluctuations are associated with changes in receptor availability in the brain. Thus, we compared mRNA expression of oestrogen receptor (ER)α, progesterone receptor (PR), vasopressin receptor (V1a) and oxytocin receptor (OTR) in brain regions implicated in paternal care [i.e. medial preoptic area (MPOA)], fear [i.e. medial amygdala (MeA)] and anxiety [i.e. bed nucleus of the stria terminalis (BNST)] between first-time fathers (n = 8) and age-matched virgin males (n = 7). Males from both reproductive conditions behaved paternally towards unrelated pups, whereas fathers showed significantly shorter latencies to behave paternally and less time investigating pups. Furthermore, fathers showed significantly lower PR, OTR and V1a receptor mRNA expression in the BNST compared to virgins. Fathers also showed a marginally significant (P = 0.07) reduction in progesterone receptor mRNA expression in the MPOA, although fatherhood was not associated with any other changes in receptor mRNA in the MPOA or MeA. The results of the present study indicate that behavioural and endocrine changes associated with the onset of fatherhood, and/or with cohabitation with a (breeding) female, are accompanied by changes in mRNA expression of hormone and neuropeptide receptors in the brain. PMID:25659593

  3. Effects of compost and manure additions on the greenhouse gas dynamics of managed grasslands

    NASA Astrophysics Data System (ADS)

    DeLonge, M. S.; Silver, W. L.

    2013-12-01

    Grasslands cover approximately 30% of the terrestrial land surface, and have significant potential to increase soil C storage and thus lower atmospheric CO2 concentrations. Organic matter amendments (e.g., compost, manure) have been shown to be effective at increasing grassland soil C both through direct addition and by increasing net primary productivity. However, organic matter additions can also increase N2O and CH4 fluxes. The effects of organic matter amendments on both soil C and greenhouse gas emissions are dependent on their physical and chemical qualities. To explore the impacts of organic matter amendments of different chemical and physical qualities on soil C and greenhouse gas emissions we established research plots on three managed annual grasslands in California. Three replicate blocks were established at each site and included an untreated control, a manure treatment, and a compost treatment. At one site, an additional compost with a lower nitrogen content was also tested. In October 2011, a 1 cm layer of the designated amendment was added to each plot. All plots were sampled for soil (C and N, bulk density, temperature, moisture) and plant (community, aboveground biomass) properties, prior to and for two years following treatment. Plots were also sampled intensively for N2O, CH4, and CO2 fluxes using static chambers on over 35 days throughout the two rainy seasons, where sampling days were selected to target pulses following rain events. Results show that the amendments differentially affected soil C and greenhouse gases among the treatments. One year after treatment, C concentrations in the top 10 cm of soils had increased at all three sites by a mean of 0.5-1% on plots that received either compost treatment, but not on those that received manure. Lower in the profile (10-30 cm), C concentrations were increased by a smaller amount (<0.3%) and only in two of the sites. The untreated grassland soils were a small source of N2O during the first few

  4. FIFE data analysis: Testing BIOME-BGC predictions for grasslands

    NASA Technical Reports Server (NTRS)

    Hunt, E. Raymond, Jr.

    1994-01-01

    The First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) was conducted in a 15 km by 15 km research area located 8 km south of Manhattan, Kansas. The site consists primarily of native tallgrass prairie mixed with gallery oak forests and croplands. The objectives of FIFE are to better understand the role of biology in controlling the interactions between the land and the atmosphere, and to determine the value of remotely sensed data for estimating climatological parameters. The goals of FIFE are twofold: the upscale integration of models, and algorithm development for satellite remote sensing. The specific objectives of the field campaigns carried out in 1987 and 1989 were the simultaneous acquisition of satellite, atmospheric, and surface data; and the understanding of the processes controlling surface energy and mass exchange. Collected data were used to study the dynamics of various ecosystem processes (photosynthesis, evaporation and transpiration, autotrophic and heterotrophic respiration, etc.). Modelling terrestrial ecosystems at scales larger than that of a homogeneous plot led to the development of simple, generalized models of biogeochemical cycles that can be accurately applied to different biomes through the use of remotely sensed data. A model was developed called BIOME-BGC (for BioGeochemical Cycles) from a coniferous forest ecosystem model, FOREST-BGC, where a biome is considered a combination of a life forms in a specified climate. A predominately C4-photosynthetic grassland is probably the most different from a coniferous forest possible, hence the FIFE site was an excellent study area for testing BIOME-BGC. The transition from an essentially one-dimensional calculation to three-dimensional, landscape scale simulations requires the introduction of such factors as meteorology, climatology, and geomorphology. By using remotely sensed geographic information data for important model inputs, process

  5. Soil fungal communities respond to grassland plant community richness and soil edaphics.

    PubMed

    LeBlanc, Nicholas; Kinkel, Linda L; Kistler, H Corby

    2015-07-01

    Fungal communities in soil have significant influences on terrestrial ecosystem dynamics, yet our understanding of the drivers of fungal diversity and community structure in soil is limited. Fungal communities associated with the rhizosphere of four native perennial grassland plant species, two legumes and two grasses, grown in monoculture and polyculture in a long-term field experiment were characterized. Reference databases were developed for, and amplicon libraries sequenced from, multiple-copy rRNA and single-copy protein-coding loci. Clustering and alignment-based pipelines were utilized to evaluate differences in fungal community structure and diversity in response to plant host, plant community richness, and soil edaphics. Fungal diversity increased in the rhizosphere of plants growing in polyculture plant communities as compared to monoculture plant communities. Fungal community structure was differentiated between legumes and grasses growing in monoculture but not in polyculture. To specifically monitor fungi in the genus Fusarium in the soil, the protein-coding locus was used to increase phylogenetic resolution and enrich for this taxon. These data show that fungal community richness and structure are strongly linked with plant community dynamics and associated soil edaphic characteristics in these grassland soils. PMID:25399511

  6. Long-term decline in grassland productivity driven by increasing dryness

    PubMed Central

    Brookshire, E. N. J.; Weaver, T.

    2015-01-01

    Increasing aridity and drought severity forecast for many land areas could reduce the land carbon (C) sink. However, with limited long-term direct measures, it is difficult to distinguish direct drying effects from counter effects of CO2 enrichment and nitrogen (N) deposition. Here, we document a >50% decline in production of a native C3 grassland over four decades and assign the forcing and timing to increasing aridity and specifically to declining late-summer rainfall. Analysis of C and N stable isotopes in biomass suggests that enhanced water use efficiency via CO2 enrichment may have slightly ameliorated the productivity decline but that changes in N had no effects. Identical declines in a long-term snow-addition experiment definitively identified increasing late-summer dryness as the cause. Our results demonstrate lasting consequences of recent climate change on grassland production and underscore the importance of understanding past climate–ecosystem coupling to predicting future responses to changing climate. PMID:25972300

  7. Taxonomic and Functional Resilience of Grasshoppers (Orthoptera, Caelifera) to Fire in South Brazilian Grasslands.

    PubMed

    Ferrando, C P R; Podgaiski, L R; Costa, M K M; Mendonça, M D S

    2016-08-01

    Fire is a frequent disturbance in grassland ecosystems enabling variability in habitat characteristics and creating important environmental filters for community assembly. Changes in vegetation have a large influence on herbivore insect assemblages. Here, we explored the responses of grasshoppers to disturbance by fire in grasslands of southern Brazil through a small-scale experiment based in paired control and burned plots. The resilience of grasshoppers was assessed by monitoring changes to their abundance, taxonomic, and functional parameters along time. Burned patches have been already recolonized by grasshoppers 1 month after fire and did not differ in terms of abundance and richness from control areas in any evaluated time within 1 year. Simpson diversity decreased 1 month after fire due to the increased dominance of Dichroplus misionensis (Carbonell) and Orphulella punctata (De Geer). In this period, grasshoppers presented in average a smaller body and a larger relative head size; these are typically nymph characteristics, which are possibly indicating a preference of juveniles for the young high-quality vegetation, or a diminished vulnerability to predation in open areas. Further, at 6 months after fire grasshoppers with smaller relative hind femur and thus lower dispersal ability seemed to be benefitted in burned patches. Finally, 1 year after fire grasshoppers became more similar to each other in relation to their set of traits. This study demonstrates how taxonomic and functional aspects of grasshopper assemblages can be complementary tools to understand their responses to environmental change. PMID:26957086

  8. Attenuation effects on the kerma rates in air after cesium depositions on grasslands.

    PubMed

    Jacob, P; Meckbach, R; Paretzke, H G; Likhtarev, I; Los, I; Kovgan, L; Komarikov, I

    1994-01-01

    Since the reactor accident of Chernobyl, cesium depth profiles and nuclide-specific kerma rates in air have been determined for various grassland sites in south Bavaria and in Ukraine. The sites are described by soil characteristics, annual precipitation, distance from release point, mode of deposition, and activity per unit area. The effects of surface roughness and migration of cesium into the soil on the kerma rate in air over grasslands was determined by two methods. The kerma rates in air obtained by the evaluations of in situ gamma-ray spectrometry results and of measured activity distributions in the soil showed only negligible differences for the observation period of 6 years after deposition. For the sites in Ukraine the kerma rate in air per activity per unit area was found to be systematically 40% higher than in Bavaria. The results from Bavaria on the attenuation of the kerma rate and a data set, including experiences from the weapons test fallout, are analytically approximated as a function of time up to 25 years after deposition. PMID:7809371

  9. Warming reduces carbon losses from grassland exposed to elevated atmospheric carbon dioxide.

    PubMed

    Pendall, Elise; Heisler-White, Jana L; Williams, David G; Dijkstra, Feike A; Carrillo, Yolima; Morgan, Jack A; Lecain, Daniel R

    2013-01-01

    The flux of carbon dioxide (CO2) between terrestrial ecosystems and the atmosphere may ameliorate or exacerbate climate change, depending on the relative responses of ecosystem photosynthesis and respiration to warming temperatures, rising atmospheric CO2, and altered precipitation. The combined effect of these global change factors is especially uncertain because of their potential for interactions and indirectly mediated conditions such as soil moisture. Here, we present observations of CO2 fluxes from a multi-factor experiment in semi-arid grassland that suggests a potentially strong climate - carbon cycle feedback under combined elevated [CO2] and warming. Elevated [CO2] alone, and in combination with warming, enhanced ecosystem respiration to a greater extent than photosynthesis, resulting in net C loss over four years. The effect of warming was to reduce respiration especially during years of below-average precipitation, by partially offsetting the effect of elevated [CO2] on soil moisture and C cycling. Carbon losses were explained partly by stimulated decomposition of soil organic matter with elevated [CO2]. The climate - carbon cycle feedback observed in this semiarid grassland was mediated by soil water content, which was reduced by warming and increased by elevated [CO2]. Ecosystem models should incorporate direct and indirect effects of climate change on soil water content in order to accurately predict terrestrial feedbacks and long-term storage of C in soil. PMID:23977180

  10. Does drought modify the decomposability of grassland species ? An incubation study

    NASA Astrophysics Data System (ADS)

    Gouskov, B.; Heim, A.; Abiven, S.

    2009-04-01

    Climate projections in Europe predict an increase in length and frequency of droughts within the next decades. This might be particularly an issue in sensitive ecosystems that are considered as carbon sink, like for example alpine grasslands. A variation in moisture content directly affects both litter decomposition and biomass production. Additionally, drought may alsopotentially affect the biochemical quality of plant litter reaching the soil. Under water limiting conditions, significant modifications of plant tissues composition have been observed (for example an increase of the cutin content), which could modify decomposition dynamics of the litter layer. In this study, we followed the decomposition of three grassland species (Poa pratensis L., Lolium multiflorum et Trifolium repens L.) that grew i/ under real climate and ii/ during an artificial drought. These plants were sampled on an experimental site (Chamau, Switzerland) during a three-year drought simulation experiment. The biochemical characteristics of the different plants were estimated by C, N content, water-soluble C, Diffuse Reflectance Infrared Fourier Transform Spectroscopy and lignin CuO oxidation. We followed the microbial community structure before and after the decomposition study using a Biolog system. The decomposition of the organic matter was followed under controlled conditions (23°C, water level regularly adjusted). The decomposition dynamics were measured by CO2 trapping in NaOH. First results show that Trifolium litter that grew under drought decomposes more slowly than one that grew under regular conditions. No significant difference was found for the other species.

  11. Plant diversity effects on grassland productivity are robust to both nutrient enrichment and drought

    PubMed Central

    Isbell, Forest; Manning, Pete; Connolly, John; Bruelheide, Helge; Ebeling, Anne; Roscher, Christiane; van Ruijven, Jasper; Weigelt, Alexandra; Wilsey, Brian; Beierkuhnlein, Carl; de Luca, Enrica; Griffin, John N.; Hautier, Yann; Hector, Andy; Jentsch, Anke; Kreyling, Jürgen; Lanta, Vojtech; Loreau, Michel; Meyer, Sebastian T.; Mori, Akira S.; Naeem, Shahid; Palmborg, Cecilia; Polley, H. Wayne; Reich, Peter B.; Schmid, Bernhard; Siebenkäs, Alrun; Seabloom, Eric; Thakur, Madhav P.; Tilman, David; Vogel, Anja; Eisenhauer, Nico

    2016-01-01

    Global change drivers are rapidly altering resource availability and biodiversity. While there is consensus that greater biodiversity increases the functioning of ecosystems, the extent to which biodiversity buffers ecosystem productivity in response to changes in resource availability remains unclear. We use data from 16 grassland experiments across North America and Europe that manipulated plant species richness and one of two essential resources—soil nutrients or water—to assess the direction and strength of the interaction between plant diversity and resource alteration on above-ground productivity and net biodiversity, complementarity, and selection effects. Despite strong increases in productivity with nutrient addition and decreases in productivity with drought, we found that resource alterations did not alter biodiversity–ecosystem functioning relationships. Our results suggest that these relationships are largely determined by increases in complementarity effects along plant species richness gradients. Although nutrient addition reduced complementarity effects at high diversity, this appears to be due to high biomass in monocultures under nutrient enrichment. Our results indicate that diversity and the complementarity of species are important regulators of grassland ecosystem productivity, regardless of changes in other drivers of ecosystem function. PMID:27114579

  12. Effects of Simulated Climate Conditions on Phosphorus Cycling in an Annual Grassland Ecosystem

    NASA Astrophysics Data System (ADS)

    Mellett, T.; Paytan, A.; Defforey, D.; Roberts, K.

    2014-12-01

    The Jasper Ridge Global Change Experiment is a long-term study of the effects of simulated climate change conditions on an annual grassland ecosystem. The different treatments consist of elevated atmospheric CO2 levels, enhanced nitrate deposition, as well as higher temperatures and precipitation rates. A representative portion of the above ground vegetation from each plot is harvested. The aim of this study is to investigate the effects of different climate conditions on the phosphorus content and phosphorus cycling in terrestrial plants. Since phosphorus only has one stable isotope, the δ18O signature in phosphate is used as a proxy to investigate phosphorus cycling. Although this technique has been successful in determining phosphorous cycling in aquatic systems, only a few studies have used this approach for terrestrial ecosystems. We analyzed the δ18O of the most abundant grass from each of the plots and treatments. The δ18O values of each sample are compared to elemental budgets of carbon, nitrogen, and phosphorous for correlation as well as soil enzyme activities. and the combination of measures are assessed as indicators for phosphorus limitation in each respective treatment site and provide a better understanding of phosphorus cycling in annual grasslands and the potential effects of climate change on phosphorus cycling.

  13. Effects of Simulated Climate Conditions on Phosphorus Cycling in an Annual Grassland

    NASA Astrophysics Data System (ADS)

    Mellett, T.; Defforey, D.; Paytan, A.

    2012-12-01

    The Jasper Ridge Global Change Experiment is a long-term study of the effects of simulated climate change conditions on an annual grassland. The different treatments consist of elevated atmospheric CO2 levels, enhanced nitrate deposition, as well as higher temperatures and precipitation rates. The above ground vegetation from each plot is harvested and separated by species, with the dominant species being selected for analysis. The aim of this study is to investigate the effects of different climate conditions on the phosphorus content and phosphorus cycling in terrestrial plants. Phosphorus content in grass samples is determined using the colorimetric reaction (soluble reactive phosphorus content), as well as combustion and acid digestion (total phosphorus content). Since phosphorus only has one stable isotope, the δ18O signature in phosphate is used as a proxy to investigate phosphorus cycling in this ecosystem. These three tools will be combined and evaluated as indicators for phosphorus limitation in each respective treatment site and provide a better understanding of phosphorus cycling in annual grasslands and the potential effects of climate change on phosphorus cycling.

  14. Nitrogen deposition effects on subalpine grassland: The role of nutrient limitations and changes in mycorrhizal abundance

    NASA Astrophysics Data System (ADS)

    Blanke, Verena; Bassin, Seraina; Volk, Matthias; Fuhrer, Jürg

    2012-11-01

    To better understand how increasing atmospheric nitrogen (N) deposition may affect subalpine grassland, we carried out a nutrient addition experiment in the Swiss Alps. N addition (+N) was combined with phosphorus (P) addition (+P) to determine nutrient limitations in plant functional groups. To examine responses of arbuscular mycorrhizal fungi (AMF) and AMF effects on plant growth, in-growth cores containing local plant species (phytometers) were inserted, and in half of them the external mycelium was disrupted weekly to impede mycorrhizal functioning. At harvest, aboveground biomass and element concentrations of the established vegetation were measured, as well as phytometer shoot and root mass, and the percentage of root length colonized (%RLC) by AMF. Only productivity of grasses increased under +N and +P, while other groups showed no or negative growth responses. +P decreased %RLC in all phytometers, whereas +N increased %RLC in the most abundant grass species, and reduced the relative abundance of arbuscules to total intraradical mycelium in the other species. Weekly destruction of the external mycelium reduced %RLC in most species, but did not affect plant biomass. The results suggest that increased N deposition in such N- and P-co-limited grassland will lead to shifts in plant functional group composition due to differences in the plants' nutrient demand, that +N will affect AMF abundance and mutualistic functioning, but that changes in AMF abundance may not considerably affect plant growth.

  15. Plant diversity effects on grassland productivity are robust to both nutrient enrichment and drought.

    PubMed

    Craven, Dylan; Isbell, Forest; Manning, Pete; Connolly, John; Bruelheide, Helge; Ebeling, Anne; Roscher, Christiane; van Ruijven, Jasper; Weigelt, Alexandra; Wilsey, Brian; Beierkuhnlein, Carl; de Luca, Enrica; Griffin, John N; Hautier, Yann; Hector, Andy; Jentsch, Anke; Kreyling, Jürgen; Lanta, Vojtech; Loreau, Michel; Meyer, Sebastian T; Mori, Akira S; Naeem, Shahid; Palmborg, Cecilia; Polley, H Wayne; Reich, Peter B; Schmid, Bernhard; Siebenkäs, Alrun; Seabloom, Eric; Thakur, Madhav P; Tilman, David; Vogel, Anja; Eisenhauer, Nico

    2016-05-19

    Global change drivers are rapidly altering resource availability and biodiversity. While there is consensus that greater biodiversity increases the functioning of ecosystems, the extent to which biodiversity buffers ecosystem productivity in response to changes in resource availability remains unclear. We use data from 16 grassland experiments across North America and Europe that manipulated plant species richness and one of two essential resources-soil nutrients or water-to assess the direction and strength of the interaction between plant diversity and resource alteration on above-ground productivity and net biodiversity, complementarity, and selection effects. Despite strong increases in productivity with nutrient addition and decreases in productivity with drought, we found that resource alterations did not alter biodiversity-ecosystem functioning relationships. Our results suggest that these relationships are largely determined by increases in complementarity effects along plant species richness gradients. Although nutrient addition reduced complementarity effects at high diversity, this appears to be due to high biomass in monocultures under nutrient enrichment. Our results indicate that diversity and the complementarity of species are important regulators of grassland ecosystem productivity, regardless of changes in other drivers of ecosystem function. PMID:27114579

  16. Nitric oxide emission from arid grassland and shrubland ecosystems in southern New Mexico

    SciTech Connect

    Hartley, A.E.; Schlesinger, W.H. )

    1993-06-01

    Soil nitrogen losses are characteristic of the transition from semi-arid grassland to arid shrubland in the southwestern United States. Nitrogen gas emission from soil microbial activity contributes to the long-term reduction of soil fertility associated with desertification. We investigated nitric Oxide (NO) emission from arid soils in the Jornada Experimental Range, near Las Cruces, New Mexico. During the dry season, mean NO fluxes from coarse-textured soils in a Boutelcua grassland and a Larrea shrubland were similar (0.12 and 0.15 ng NO-N cm[sup [minus]2] hr[sup [minus]1], respectively), and higher than flexes from fine-textured soils in a Flourensia shrubland (0.02 ng NO-N cm[sup [minus]2] hr[sup [minus]1]). In a wetting experiment, mean NO fluxes were higher under shrub canopies of Larrea and Flourensia, reflecting the accumulation of soil organic matter under shrubs in islands of fertility. In the Larrea shrubland, mean NO fluxes were ten times higher under shrubs than between shrubs (12.9 vs. 1.29 ng NO-N cm[sup [minus]2] hr[sup [minus]1]).

  17. Long-term decline in grassland productivity driven by increasing dryness.

    PubMed

    Brookshire, E N J; Weaver, T

    2015-01-01

    Increasing aridity and drought severity forecast for many land areas could reduce the land carbon (C) sink. However, with limited long-term direct measures, it is difficult to distinguish direct drying effects from counter effects of CO2 enrichment and nitrogen (N) deposition. Here, we document a >50% decline in production of a native C3 grassland over four decades and assign the forcing and timing to increasing aridity and specifically to declining late-summer rainfall. Analysis of C and N stable isotopes in biomass suggests that enhanced water use efficiency via CO2 enrichment may have slightly ameliorated the productivity decline but that changes in N had no effects. Identical declines in a long-term snow-addition experiment definitively identified increasing late-summer dryness as the cause. Our results demonstrate lasting consequences of recent climate change on grassland production and underscore the importance of understanding past climate-ecosystem coupling to predicting future responses to changing climate. PMID:25972300

  18. Using Shrub Clearing, Draining, and Herbivory to Control Bramble Invasion in Mediterranean Dry Grasslands.

    PubMed

    Masson, Solène; Mesléard, François; Dutoit, Thierry

    2015-10-01

    For centuries, the dry grassland of the plain of La Crau (south-eastern France) has been subjected to numerous disturbances resulting in the destruction and the fragmentation of this emblematic rangeland ecosystem of the Mediterranean. Today, this ecosystem is facing a new threat from a proliferating native species, the bramble (Rubus ulmifolius Schott), which preferentially colonizes areas that were formerly cultivated and/or exposed to water infiltration. To identify a strategy for effective control of this colonization, in situ experiments testing disturbance regimes (shrub clearing and/or mixed grazing by sheep and goats) combined with the control of access to water resources (with or without drainage trenches) were undertaken between 2010 and 2013. Only clearing and grazing combined over 3 years led to significant changes in vegetation height and bramble cover as well as modifications in the floristic composition, diversity, similarity, and richness of the plant community. Neither a clearing operation carried out in 2010 alone, nor grazing alone, reduced bramble cover, and neither treatment increased the species richness of the plant community. Similarly, digging drainage trenches had no significant impact either on the plant community or on bramble cover. Our study suggests that only annual mechanical clearing coupled with sheep and goats grazing can significantly reduce bramble cover. This combined restoration treatment needs to be applied for at least 3 consecutive years to induce significant changes and enable this ecosystem to return to the dry grassland succession. PMID:26013075

  19. Using Shrub Clearing, Draining, and Herbivory to Control Bramble Invasion in Mediterranean Dry Grasslands

    NASA Astrophysics Data System (ADS)

    Masson, Solène; Mesléard, François; Dutoit, Thierry

    2015-10-01

    For centuries, the dry grassland of the plain of La Crau (south-eastern France) has been subjected to numerous disturbances resulting in the destruction and the fragmentation of this emblematic rangeland ecosystem of the Mediterranean. Today, this ecosystem is facing a new threat from a proliferating native species, the bramble ( Rubus ulmifolius Schott), which preferentially colonizes areas that were formerly cultivated and/or exposed to water infiltration. To identify a strategy for effective control of this colonization, in situ experiments testing disturbance regimes (shrub clearing and/or mixed grazing by sheep and goats) combined with the control of access to water resources (with or without drainage trenches) were undertaken between 2010 and 2013. Only clearing and grazing combined over 3 years led to significant changes in vegetation height and bramble cover as well as modifications in the floristic composition, diversity, similarity, and richness of the plant community. Neither a clearing operation carried out in 2010 alone, nor grazing alone, reduced bramble cover, and neither treatment increased the species richness of the plant community. Similarly, digging drainage trenches had no significant impact either on the plant community or on bramble cover. Our study suggests that only annual mechanical clearing coupled with sheep and goats grazing can significantly reduce bramble cover. This combined restoration treatment needs to be applied for at least 3 consecutive years to induce significant changes and enable this ecosystem to return to the dry grassland succession.

  20. Cellulolytic potential under environmental changes in microbial communities from grassland litter

    DOE PAGESBeta

    Berlemont, Renaud; Allison, Steven D.; Weihe, Claudia; Lu, Ying; Brodie, Eoin L.; Martiny, Jennifer B. H.; Martiny, Adam C.

    2014-11-25

    In many ecosystems, global changes are likely to profoundly affect microorganisms. In Southern California, changes in precipitation and nitrogen deposition may influence the composition and functional potential of microbial communities and their resulting ability to degrade plant material. To test whether such environmental changes impact the distribution of functional groups involved in leaf litter degradation, we determined how the genomic diversity of microbial communities in a semi-arid grassland ecosystem changed under reduced precipitation or increased N deposition. We monitored communities seasonally over a period of 2 years to place environmental change responses into the context of natural variation. Fungal andmore » bacterial communities displayed strong seasonal patterns, Fungi being mostly detected during the dry season whereas Bacteria were common during wet periods. Most putative cellulose degraders were associated with 33 bacterial genera and predicted to constitute 18% of the microbial community. Precipitation reduction reduced bacterial abundance and cellulolytic potential whereas nitrogen addition did not affect the cellulolytic potential of the microbial community. Finally, we detected a strong correlation between the frequencies of genera of putative cellulose degraders and cellulase genes. Thus, microbial taxonomic composition was predictive of cellulolytic potential. This work provides a framework for how environmental changes affect microorganisms responsible for plant litter deconstruction.« less

  1. Cellulolytic potential under environmental changes in microbial communities from grassland litter

    SciTech Connect

    Berlemont, Renaud; Allison, Steven D.; Weihe, Claudia; Lu, Ying; Brodie, Eoin L.; Martiny, Jennifer B. H.; Martiny, Adam C.

    2014-11-25

    In many ecosystems, global changes are likely to profoundly affect microorganisms. In Southern California, changes in precipitation and nitrogen deposition may influence the composition and functional potential of microbial communities and their resulting ability to degrade plant material. To test whether such environmental changes impact the distribution of functional groups involved in leaf litter degradation, we determined how the genomic diversity of microbial communities in a semi-arid grassland ecosystem changed under reduced precipitation or increased N deposition. We monitored communities seasonally over a period of 2 years to place environmental change responses into the context of natural variation. Fungal and bacterial communities displayed strong seasonal patterns, Fungi being mostly detected during the dry season whereas Bacteria were common during wet periods. Most putative cellulose degraders were associated with 33 bacterial genera and predicted to constitute 18% of the microbial community. Precipitation reduction reduced bacterial abundance and cellulolytic potential whereas nitrogen addition did not affect the cellulolytic potential of the microbial community. Finally, we detected a strong correlation between the frequencies of genera of putative cellulose degraders and cellulase genes. Thus, microbial taxonomic composition was predictive of cellulolytic potential. This work provides a framework for how environmental changes affect microorganisms responsible for plant litter deconstruction.

  2. Non-destructive assessment of the effects of elevated CO 2 on plant community structure in a calcareous grassland

    NASA Astrophysics Data System (ADS)

    Rötzel, Christina; Leadley, Paul W.; Körner, Christian

    Calcareous grassland was exposed to ambient or elevated CO 2 using a Screen-Aided CO 2 Control (SACC) system starting in March 1994. The effects of elevated CO 2 on plant community structure were studied using the point intercept method. Measurements were made in March 1994 prior to the start of CO 2 exposure and again in June 1994 at peak plant biomass. There were no significant differences in the initial structure of the communities based on their assigned CO 2 treatments in March. After 9 weeks of exposure of the community to elevated CO 2, the total number of intercepts per plot was not significantly different between CO 2 treatments; however, Carex flacca and Cirsium acaule had marginally significant (P=0.055 and P=0.06) increases in the % sward of the community at elevated CO 2 (number of intercepts for a single species divided by the total number of intercepts for all species). Measurements of leaf extension in Carex flacca showed that at least part of the increase in % sward at elevated CO 2 could be explained by greater leaf length per plant (P=0.02). These measurements and other experiments with calcareous grassland species and communities suggest that rising atmospheric CO 2 concentrations will probably alter the structure of calcareous grassland communities.

  3. Mesocarnivore Surveys on Lawrence Livermore National Laboratory Site 300, Alameda and San Joaquin Counties, California

    SciTech Connect

    Clark, H O; Smith, D A; Cypher, B L; Kelly, P A; Woollett, J S

    2004-11-16

    Lawrence Livermore National Laboratory (LLNL), operated under cooperative agreement between the University of California and the U. S. Department of Energy, administers and operates an approximately 11 mi{sup 2} (28 km{sup 2}) test site in the remote hills at the northern end of the South Coast Ranges of Central California (Figure 1). Known as Site 300, this expanse of rolling hills and canyons supports a diverse array of grassland communities typical of lowland central California. The facility serves a variety of functions related to testing non-nuclear explosives, lasers, and weapons subsystems. The primary purpose of this project was to determine the presence of any mesocarnivores on Site 300 that use the property for foraging, denning, and other related activities. The surveys occurred from mid-September to mid-October, 2002.

  4. Co-evolving Physical and Biological Organization in Step-pool Channels: Experiments from a Restoration Reach on Wildcat Creek, California

    NASA Astrophysics Data System (ADS)

    Chin, A.; O'Dowd, A. P.; Mendez, P. K.; Velasco, K. Z.; Leventhal, R. D.; Storesund, R.; Laurencio, L. R.

    2014-12-01

    Step-pools are important features in fluvial systems. Through energy dissipation, step-pools provide stability in high-energy environments that otherwise may erode and degrade. Although research has focused on geomorphological aspects of step-pool channels, the ecological significance of step-pool streams is increasingly recognized. Step-pool streams often contain higher density and diversity of benthic macroinvertebrates and are critical habitats for organisms such as salmonids and tailed frogs. Step-pools are therefore increasingly used to restore eroding channels and improve ecological conditions. This paper addresses a restoration reach of Wildcat Creek in Berkeley, California that featured an installation of step-pools in 2012. The design framework recognized step-pool formation as a self-organizing process that produces a rhythmic morphology. After placing step particles at locations where step-pools are expected to form according to hydraulic theory, the self-organizing approach allowed fluvial processes to refine the rocks into adjusted sequences over time. In addition, a 30-meter "experimental" reach was created to explore the co-evolution of geomorphological and ecological characteristics. After constructing a plane bed channel, boulders and cobbles piled at the upstream end allowed natural flows to mobilize and sort them into step-pool sequences. Ground surveys and LiDAR recorded the development of step-pool sequences over several seasons. Concurrent sampling of benthic macroinvertebrates documented the formation of biological communities in conjunction with habitat. Biological sampling in an upstream reference reach provided a comparison with the restored reach over time. Results to date show an emergent step-pool channel with steps that segment the plane bed into initial step and pool habitats. Biological communities are beginning to form, showing more distinction among habitat types during some seasons, although they do not yet approach reference

  5. Species richness and the temporal stability of biomass production: A new analysis of recent biodiversity experiments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this study, we investigate how species richness affects temporal stability of biomass production by analyzing 27 recent biodiversity experiments conducted in grassland and freshwater algal communities. We find that, in grasslands, increasing species richness stabilizes whole-community biomass pro...

  6. Balancing forest-regeneration probabilities and maintenance costs in dry grasslands of high conservation priority

    USGS Publications Warehouse

    Bolliger, Janine; Edwards, Thomas C., Jr.; Eggenberg, Stefan; Ismail, Sascha; Seidl, Irmi; Kienast, Felix

    2011-01-01

    Abandonment of agricultural land has resulted in forest regeneration in species-rich dry grasslands across European mountain regions and threatens conservation efforts in this vegetation type. To support national conservation strategies, we used a site-selection algorithm (MARXAN) to find optimum sets of floristic regions (reporting units) that contain grasslands of high conservation priority. We sought optimum sets that would accommodate 136 important dry-grassland species and that would minimize forest regeneration and costs of management needed to forestall predicted forest regeneration. We did not consider other conservation elements of dry grasslands, such as animal species richness, cultural heritage, and changes due to climate change. Optimal sets that included 95–100% of the dry grassland species encompassed an average of 56–59 floristic regions (standard deviation, SD 5). This is about 15% of approximately 400 floristic regions that contain dry-grassland sites and translates to 4800–5300 ha of dry grassland out of a total of approximately 23,000 ha for the entire study area. Projected costs to manage the grasslands in these optimum sets ranged from CHF (Swiss francs) 5.2 to 6.0 million/year. This is only 15–20% of the current total estimated cost of approximately CHF30–45 million/year required if all dry grasslands were to be protected. The grasslands of the optimal sets may be viewed as core sites in a national conservation strategy.

  7. Differences in spatial and temporal root lifespan of temperate steppes across Inner Mongolia grasslands

    NASA Astrophysics Data System (ADS)

    Bai, W.-M.; Zhou, M.; Fang, Y.; Zhang, W.-H.

    2015-12-01

    Lifespan of fine roots plays important roles in regulating carbon (C) cycling in terrestrial ecosystems. Determination of root lifespan and elucidation of its regulatory mechanism in different plant communities are essential for accurate prediction of C cycling from ecosystem to regional scales. Temperate steppes in Inner Mongolia grasslands have three major types, i.e., Stipa krylovii, Stipa grandis and Stipa breviflora grasslands. There have been no studies to compare the root dynamics among the three types of grasslands. In the present study, we determined root lifespan of the three grasslands using the rhizotron. We found that root lifespan differed substantially among the three types of grasslands within the temperate steppes of Inner Mongolia, such that root lifespan of Stipa breviflora > Stipa grandis > Stipa krylovii grasslands. Root lifespan across the three types of grasslands in the Inner Mongolian temperate steppes displayed a similar temporal pattern, i.e. lifespan of the roots produced in spring and autumn was shortest and longest, respectively, whereas lifespan of summer-produced roots was between that of roots produced in spring and autumn. The spatial and temporal differences in root lifespan across the three types of grasslands were mainly determined by contents of soluble sugars in roots of the dominant species. The differences in root lifespan across the major types of grasslands and different seasons highlight the necessity to take into account these differences in the prediction of C cycling within grassland ecosystem by the simulating model.

  8. Effectiveness of voluntary habitat stewardship in conserving grassland: case of operation burrowing owl in Saskatchewan.

    PubMed

    Warnock, Robert G; Skeel, Margaret A

    2004-03-01

    There have been no published performance evaluations of nongovernmental, voluntary habitat stewardship programs. The Operation Burrowing Owl (OBO) stewardship program, initiated in 1987, was evaluated for its effectiveness in conservation of grassland habitat during 1986-1993. The 108 OBO sites from 1987 to 88 and 98 randomly selected non-OBO sites that were grassland in 1986 in the Regina-Weyburn, Saskatchewan study area were classified by size and agricultural soil suitability. By 1993, 41 (38%) of the 108 OBO sites had been withdrawn from the program. The 1986 area of grassland was compared with grassland area calculated from digitized 1993 LANDSAT imagery. A correction for satellite inaccuracies was determined. Grassland retention in 1993 was significantly higher at OBO sites (66%) than at random sites (49%), demonstrating that the OBO voluntary program effectively conserved habitat. Also, grassland retention was significantly lower on sites with better agricultural soils, and for sites <12 ha in size. Site type (OBO or random), size and their interaction, followed by agricultural soil suitability, had the greatest effects on grassland retention. During an era of accelerated grassland loss, OBO strongly and positively (statistically significant) affected conservation of grassland sites most at risk: sites <12 ha in size and with good to excellent agricultural soils. This suggests that grassland conservation efforts focus on vulnerable sites (small size and/or good agricultural soils) to provide nesting habitat for burrowing owls. Our study demonstrates that a voluntary stewardship program can significantly increase conservation of habitat. PMID:15037954

  9. Assemblages of breeding birds as indicators of grassland condition

    USGS Publications Warehouse

    Browder, S.F.; Johnson, D.H.; Ball, I.J.

    2002-01-01

    We developed a measure of biological integrity for grasslands (GI) based on the most influential habitat types in the Prairie Pothole Region of North Dakota. GI is based on proportions of habitat types and the relationships of these habitat types to breeding birds. Habitat types were identified by digital aerial photography, verified on the ground, and quantified using GIS, We then developed an index to GI based on the presence or abundance of breeding bird species. Species abundance data were obtained from 3 min roadside point counts at 889 points in 44, 4050 ha study plots over a 2-year period. Using a modified North American Breeding Bird Survey protocol, species were recorded in each of four quadrants at each point. Fifty species selected for analysis included all grassland species that occurred in at least 15 quadrants and all other bird species that occurred in at least 1 % of quadrants. We constructed preliminary models using data from each of the 2 years, then tested their predictive ability by cross-validation with data from the other year. These cross-validation tests indicated that the index consistently predicted grassland integrity. The final four models (presence and abundance models at 200 and 400 m scales) included only those species that were statistically significant (P ??? 0.05) in all preliminary models. Finally, we interpreted the components of the indices by examining associations between individual species and habitat types. Logistic regression identified 386 statistically significant relationships between species and habitat types at 200 and 400m scales. This method, though labor-intensive, successfully uses the presence of grassland-dependent species and absence of species associated with woody vegetation or cropland to provide an index to grassland integrity. Once regional associations of species with habitat types have been identified, such indices can be applied relatively inexpensively to monitor grassland integrity over large

  10. Assemblages of breeding birds as indicators of grassland condition

    USGS Publications Warehouse

    Browder, S.F.; Johnson, D.H.; Ball, I.J.

    2002-01-01

    We developed a measure of biological integrity for grasslands (GI) based on the most influential habitat types in the Prairie Pothole Region of North Dakota. GI is based on proportions of habitat types and the relationships of these habitat types to breeding birds. Habitat types were identified by digital aerial photography, verified on the ground, and quantified using GIS. We then developed an index to GI based on the presence or abundance of breeding bird species. Species abundance data were obtained from 3 min roadside point counts at 889 points in 44, 4050 ha study plots over a 2-year period. Using a modified North American Breeding Bird Survey protocol, species were recorded in each of four quadrants at each point. Fifty species selected for analysis included all grassland species that occurred in at least 15 quadrants and all other bird species that occurred in at least 1% of quadrants. We constructed preliminary models using data from each of the 2 years, then tested their predictive ability by cross-validation with data from the other year. These cross-validation tests indicated that the index consistently predicted grassland integrity. The final four models (presence and abundance models at 200 and 400 m scales) included only those species that were statistically significant (P 0.05) in all preliminary models. Finally we interpreted the components of the indices by examining associations between individual species and habitat types. Logistic regression identified 386 statistically significant relationships between species and habitat types at 200 and 400 m scales. This method, though labor-intensive, successfully uses the presence of grassland-dependent species and absence of species associated with woody vegetation or cropland to provide an index to grassland integrity. Once regional associations of species with habitat types have been identified, such indices can be applied relatively inexpensively to monitor grassland integrity over large geographic

  11. Mechanisms maintaining grassland biodiversity and ecosystem stability

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ecologists need to know how particular processes influence biodiversity and ecosystem stability. We demonstrate how data from biodiversity-ecosystem functioning experiments can be used to identify and quantify the classes of mechanisms maintaining biodiversity and ecosystem stability. We predicted...

  12. Effects of exotic grasses on soil seed banks in Southeastern Arizona grasslands

    USGS Publications Warehouse

    McLaughlin, S.P.; Bowers, Janice E.

    2007-01-01

    At the Appleton-Whittell Research Ranch, an ungrazed grassland preserve in southeastern Arizona, soil seed banks were sampled in June, August, and October 2002 and June 2003. Wildfire had previously burned 90% of the research ranch in May 2002. Seed density and species richness in burned native grassland (2 plots) were compared to those in burned exotic grassland (2 plots). Averaged over 4 sample dates, seed densities were as follows: burned native grassland, 591 ?? 243.1 seeds??m-2 and 784 ?? 334.9 seeds??m-2; burned exotic grassland, 501 ?? 198.9 seeds??m-2 and 196 ?? 123.8 seeds??m-2. Species richness in the seed bank, also averaged over 4 sample dates, was as follows: burned native grassland, 16.3 ?? 1.7 species??m -2 and 19.5 ?? 1.0 species??m-2; burned exotic grassland, 12.0 ?? 3.4 species??m-2 and 11.06 ?? 2.5 species??m-2. The seed bank of burned exotic grassland contained significantly fewer seeds and species than that of burned native grassland. In addition, the seed bank in burned exotic grassland comprised mainly exotic grasses, whereas annual and perennial herbs, most of them native, dominated the seed bank of burned native grassland. Of the 50 species detected in soil samples, only 20 had a persistent seed bank, and only 1 of these was a native perennial bunchgrass. The preponderance of transient species means that eradication of exotic grasses must be followed by reseeding of native grasses and herbs, perhaps repeatedly, if native grassland is to replace exotic grassland.

  13. Reforestation or conservation? The attributes of old growth grasslands in South Africa.

    PubMed

    Zaloumis, Nicholas P; Bond, William J

    2016-09-19

    Deforestation as a result of burning and land conversion in the tropics and subtropics has been widely studied and active restoration of forests has been widely promoted. Besides other benefits, reforestation can sequester carbon thereby reducing CO2 emissions to the atmosphere. However, before grasslands are targeted for 'reforestation', it is necessary to distinguish whether they are ancient natural grasslands or secondary vegetation colonizing deforested areas. Here we report the results of a study comparing primary grasslands in South Africa with 4-40 year old secondary grasslands recovering from afforestation with Pinus species. Primary grasslands had significantly higher plant species richness overall, especially of forb species. Ground cover of primary grasslands was more evenly distributed among species than secondary grasslands which tended to mono-dominance. Forbs with underground storage organs (USOs) were common in primary grasslands but conspicuously absent in the recovering systems. Comparison of secondary grasslands of different ages (up to 40 years) showed negligible recovery of the original species composition. Three key features distinguish old growth primary from secondary grasslands: total and forb species numbers, evenness of species contributions to cover and the presence of USOs. Old growth grasslands also differed in their fire response, showing significant post-burn resprouting and fire-stimulated flowering in contrast to secondary grasslands. Though similar contrasting attributes of ancient and secondary grasslands have been reported in South America, more studies are needed to explore their generality in other geographical regions.This article is part of the themed issue 'Tropical grassy biomes: linking ecology, human use and conservation'. PMID:27502375

  14. The Development of a Comprehensive First-Year Experience Program for the University of Southern California: Using an Innovation Gap Analysis Model

    ERIC Educational Resources Information Center

    Studdert, Thomas Patrick

    2013-01-01

    Using an innovation adaptation of the gap analysis approach of Richard Clark and Fred Estes, the collegiate First-Year Experience (FYE) consisting of comprehensive and intentional curricular and co-curricular initiatives was examined. Conceptualization and operationalization of the goal for a FYE program was based on 3 student development theories…

  15. Claremont Reading Conference Forty-Fourth Yearbook: Reading: A Humanizing Experience; Proceedings of the Claremont Reading Conference (47th, Claremont, California, January 18-19, 1980).

    ERIC Educational Resources Information Center

    Douglass, Malcolm P., Ed.

    The 25 articles in this collection focus on reading as a humanizing experience. The topics covered include the following: (1) the politics of literacy; (2) the holographic nature of the reading process; (3) literacy through language communication; (4) life-long reading; (5) diagnosis of reading disabilities based on psychoeducational analysis of…

  16. Quantification of Water Erosion on Subalpine Grassland with Rain Simulators

    NASA Astrophysics Data System (ADS)

    Schindler, Y.; Alewell, Ch.; Burri, K.; Bänninger, D.

    2009-04-01

    Intensive land use and increasing storm events trigger rain erosion, thus its quantification is important. The aim of this study was to asses the influence of the vegetation on runoff and water erosion in an alpine grassland area. Further, we estimated the influence of vegetation on the soil characteristics matrix stability and C/N ratio and assessed the relationship between those parameters as well as the grain size distribution with erosion and runoff rate. To test the above hypotheses a field spray nozzles drop former hybrid simulator, consisting of a full-core Lechler nozzle and a meshed fixed below to improve the rain drop distribution, was used. Prior to the field experiment, we compared this simulator with a drop former simulator in the laboratory at the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) in terms of drop size distribution and kinetic energy. Thereby, we could estimate the accuracy of the field simulator. The rain drop size distribution and the total kinetic energy of the drops at a rain intensity of 60 mm h-1 were measured with a Joss-Waldvogel distrometer. To compare the effect of the two rain simulators as well as the influence of the soil texture on erosion and runoff rate, we used 6 silty soil monoliths and 6 clayish monoliths. To get comparable initial conditions, every soil monolith was irrigated only one time, starting at field capacity. The soil moisture was continuously recorded by TDR probes during the simulation. The comparison of the two rain simulators showed a close similarity in the drop size distributions. For both simulators, the most frequent drop size class is in the range of 1 mm in diameter. Natural rain typically shows a larger mean drop size at an intensity of 60 mm h-1. In comparison to the natural rain, the total kinetic energy of the simulated rain of both of the simulators was too small as well. These results lead to the conclusion, that the true simulation of a natural rain is hardly realizable

  17. California: Library Information Technologies.

    ERIC Educational Resources Information Center

    Will, Barbara, Ed.

    1996-01-01

    Describes six information technology projects in California libraries, including Internet access in public libraries; digital library developments at the University of California, Berkeley; the World Wide Web home page for the state library; Pacific Bell's role in statewide connectivity; state government initiatives; and services of the state…

  18. How California Ranks

    ERIC Educational Resources Information Center

    EdSource, 2010

    2010-01-01

    Public education supports California's economic growth and creates opportunities for the state's youth. Given that, it is important for Californians to understand how much the state is investing in its schools and how that money is being spent. Comparing California with the nation and other similar states can provide a useful perspective in…

  19. California's English Learner Students

    ERIC Educational Resources Information Center

    Hill, Laura E.

    2012-01-01

    English Learner (EL) students in California's schools are numerous and diverse, and they lag behind their native-English-speaking peers. Closing the achievement gap for EL students has been a long-standing goal for California educators, and there are some signs of success. Now that EL funding and curriculum issues are receiving a fresh level of…

  20. [California State Archives.

    ERIC Educational Resources Information Center

    Rea, Jay W.

    The first paper on the California State Archives treats the administrative status, legal basis of the archives program, and organization of the archives program. The problem areas in this States' archival program are discussed at length. The second paper gives a crude sketch of the legal and administrative history of the California State Archives,…

  1. Root dynamics in native grassland exposed to elevated CO2 and warming

    NASA Astrophysics Data System (ADS)

    Pendall, E.; Carrillo, Y.; Morgan, J. A.; Newcomb, J.

    2011-12-01

    Responses of belowground processes to global change play a major role in terrestrial ecosystem carbon (C) storage and feedbacks to climate, but remain understudied in comparison to aboveground processes. In grasslands, roots comprise about 75 percent of the biomass, and are responsible for increased inputs of C to soil pools under elevated CO2. Root exudation may also be responsible for increased rates of soil organic matter decomposition, or priming, potentially offsetting inputs of new C. Understanding the fate of belowground C allocation requires a better understanding of root processes including growth, rhizodeposition, turnover and decomposition. We studied root dynamics in mixed C3/C4 grassland at the Prairie Heating and CO2 Enrichment experiment near Cheyenne, WY, where Free-Air CO2 Enrichment is applied at 600 ppm during daytime in the growing season, and temperature is elevated by 1.5/3 deg C day/night all year. We applied several belowground techniques, including direct biomass measurements coupled with C isotope labeling, root litter decomposition measured in litter bags and in plots with herbicide applied, and image analysis of intact and harvested root systems . Direct measurements indicated that elevated CO2 increased root biomass, a trend that became increasingly significant over the first four years of treatments. Warming by itself tended to decrease root biomass in the first two years, and this effect declined in the next two years of the experiment, suggesting a transient negative response of root growth to warming. Continuous 13C labeling in elevated CO2 plots allowed detection of a greater proportion of new C in warmed than ambient temperature plots, demonstrating greater allocation of C to roots exposed to both elevated CO2 and warming. A root litter bag decomposition experiment showed that C3 grass roots decomposed more rapidly with elevated CO2 alone, but more slowly when elevated CO2 was combined with warming, possibly due to soil drying. C4

  2. California Community College Transfer Rates: Who Is Counted Makes a Difference. MPR Research Brief

    ERIC Educational Resources Information Center

    Horn, Laura; Lew, Stephen

    2007-01-01

    This is the first in a series of MPR Research Briefs published on the outcomes and experiences of California community college students. California Community Colleges (CCC) enroll roughly two-thirds of all California college students and nearly one-fourth of all community college students in the nation. Their low fees and open-admission policies…

  3. Biochar application reduces N2O emission in intensively managed temperate grassland

    NASA Astrophysics Data System (ADS)

    Felber, R.; Leifeld, J.; Neftel, A.

    2012-04-01

    Biochar, a pyrolysis product of organic residues, is seen as an amendment for agricultural soils to improve soil fertility, sequester CO2 and reduce N2O emissions. Mainly used in highly weathered tropical soils, the interest of using biochar in intensively managed temperate soils is increasing. Our previous laboratory incubations have shown N2O reduction potentials of between 20 and 100% for temperate soils after biochar application (Felber et al., Biogeosciences Discuss, 2012). To assess the effect of biochar application under field conditions, a plot experiment (3 control vs. 3 biochar amended plots of 3x3 m size at a rate of 15 t ha-1) was set up in a temperate intensively managed grassland soil. N2O and CO2 emissions were quasi-continuously measured by static chambers under standard management practice over 8 months. In parallel soil samples were taken monthly from all plots and their N2O and CO2 productions were measured under controlled conditions in the lab. At the beginning of the field measurements (April 2011) cumulative N2O fluxes from biochar amended plots were above those of control plots, but the pattern reversed towards reduced fluxes from biochar plots after 3 months and the reduction reached about 15% by the end of 2011. The biochar effect on reducing N2O emissions in the laboratory was two times that of the field measurements, indicating that results from laboratory experiments are not directly transferable to field conditions. The experiments indicate a substantial N2O emission reduction potential of biochar in temperate grassland fields.

  4. Resuspension and redistribution of radionuclides during grassland and forest fires in the Chernobyl exclusion zone: part II. Modeling the transport process.

    PubMed

    Yoschenko, V I; Kashparov, V A; Levchuk, S E; Glukhovskiy, A S; Khomutinin, Yu V; Protsak, V P; Lundin, S M; Tschiersch, J

    2006-01-01

    To predict parameters of radionuclide resuspension, transport and deposition during forest and grassland fires, several model modules were developed and adapted. Experimental data of controlled burning of prepared experimental plots in the Chernobyl exclusion zone have been used to evaluate the prognostic power of the models. The predicted trajectories and elevations of the plume match with those visually observed during the fire experiments in the grassland and forest sites. Experimentally determined parameters could be successfully used for the calculation of the initial plume parameters which provide the tools for the description of various fire scenarios and enable prognostic calculations. In summary, the model predicts a release of some per thousand from the radionuclide inventory of the fuel material by the grassland fires. During the forest fire, up to 4% of (137)Cs and (90)Sr and up to 1% of the Pu isotopes can be released from the forest litter according to the model calculations. However, these results depend on the parameters of the fire events. In general, the modeling results are in good accordance with the experimental data. Therefore, the considered models were successfully validated and can be recommended for the assessment of the resuspension and redistribution of radionuclides during grassland and forest fires in contaminated territories. PMID:16476511

  5. Knowledge gained from video-monitoring grassland passerine nests

    USGS Publications Warehouse

    Pietz, Pamela J.; Granfors, D.A.; Ribic, Christine A.

    2012-01-01

    In the mid-1990s, researchers began using miniature cameras to videotape activities at cryptic passerine nests in grasslands.In subsequent years, use of these video surveillance systems spread dramatically, leading to major strides in our knowledge of nest predation and nesting ecology of many species.Studies using video nest surveillance have helped overturn or substantiate many long-standing assumptions and have provided insights on a wide range of topics.Using examples from grasslands, we highlight the accumulated knowledge about activities at nests documented with video; we also discuss implications of this knowledge for our understanding of avian ecology.Like all tools, video nest surveillance has potential limitations, and users must take precautions to minimize possible sources of bias in data collection and interpretation.

  6. [CO2 release from typical Stipa grandis grassland soil].

    PubMed

    Cui, X; Chen, S; Chen, Z

    2000-06-01

    Determinations on the soil respiration in a typical Stipa grandis grassland of Inner Mongolica by the method of static chamber/alkaline absorbing show that there existed great spatial and temporal variances of soil respiration, and the factors controlling these variances were different. The seasonal variance of soil respiration had a close relationship with the aboveground biomass of S. grandis and the status of soil moisture. The total amount of annual CO2 release in 1995, 1997 and 1998 was estimated as 180, 45.8 and 225 gC.m-2.yr-1, respectively. Overgrazing greatly decreased the biomass of the community, and also, decreased the CO2 release from the soil. The possibility of establishing a dynamic model of soil respiration in grassland with precipitation as a driven factor was discussed. PMID:11767639

  7. Direct effects of cattle on grassland birds in Canada.

    PubMed

    Bleho, Barbara I; Koper, Nicola; Machtans, Craig S

    2014-06-01

    Effects of grazing on grassland birds are generally thought to be indirect, through alteration of vegetation structure; however, livestock can also affect nest survival directly through trampling and other disturbances (e.g., livestock-induced abandonment). We extracted data on nest fates from 18 grazing studies conducted in Canada. We used these data to assess rates of nest destruction by cattle among 9 ecoregions and between seasonal and rotational grazing systems. Overall, few nests were destroyed by cattle (average 1.5% of 9132 nests). Nest destruction was positively correlated with grazing pressure (i.e., stocking rate or grazing intensity), but nest survival was higher in more heavily grazed areas for some species. Because rates of destruction of grassland bird nests by cattle are low in Canada, management efforts to reduce such destruction may not be of ecological or economic value in Canada. PMID:24617945

  8. AmeriFlux US-Wkg Walnut Gulch Kendall Grasslands

    SciTech Connect

    Scott, Russell

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-Wkg Walnut Gulch Kendall Grasslands. Site Description - This site is located in a small, intensively-studied, experimental watershed within USDA-ARS's Walnut Gulch Experimental Watershed. Eddy covariance measurements of energy, water and CO2 fluxes began in the spring of 2004, though meteorological (including Bowen ratio) and hydrological measurements are available much further back.

  9. Management options to limit nitrate leaching from grassland

    NASA Astrophysics Data System (ADS)

    Cuttle, S. P.; Scholefield, D.

    1995-12-01

    Nitrate leaching can be reduced by the adoption of less intensive grassland systems which, though requiring a greater land area to achieve the same agricultural output, result in less nitrate leaching per unit of production than do intensively managed grasslands. The economic penalties associated with reductions in output can be partly offset by greater reliance on symbiotic nitrogen fixation and the use of clover-based swards in place of synthetic N fertilisers. Alternatively, specific measures can be adopted to improve the efficiency of nitrogen use in intensively managed systems in order to maintain high outputs but with reduced losses. Controls should take account of other forms of loss and flows of nitrogen between grassland and other components of the whole-farm system and, in most instances, should result in an overall reduction in nitrogen inputs. Removing stock from the fields earlier in the grazing season will reduce the accumulation of high concentrations of potentially leachable nitrate in the soil of grazed pastures but will increase the quantity of manure produced by housed animals and the need to recycle this effectively. Supplementing grass diets with low-nitrogen forages such as maize silage will reduce the quantity of nitrogen excreted by livestock but may increase the potential for nitrate leaching elsewhere on the farm if changes to cropping patterns involve more frequent cultivation of grassland. Improved utilisation by the sward of nitrogen in animal excreta and manures and released by mineralisation of soil organic matter will permit equivalent reductions to be made in fertiliser inputs, provided that adequate information is available about the supply of nitrogen from these non-fertiliser sources.

  10. 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.

  11. Plant species com