Science.gov

Sample records for affect plant communities

  1. Plants are less negatively affected by flooding when growing in species-rich plant communities.

    PubMed

    Wright, Alexandra J; de Kroon, Hans; Visser, Eric J W; Buchmann, Tina; Ebeling, Anne; Eisenhauer, Nico; Fischer, Christine; Hildebrandt, Anke; Ravenek, Janneke; Roscher, Christiane; Weigelt, Alexandra; Weisser, Wolfgang; Voesenek, Laurentius A C J; Mommer, Liesje

    2017-01-01

    Flooding is expected to increase in frequency and severity in the future. The ecological consequences of flooding are the combined result of species-specific plant traits and ecological context. However, the majority of past flooding research has focused on individual model species under highly controlled conditions. An early summer flooding event in a grassland biodiversity experiment in Jena, Germany, provided the opportunity to assess flooding responses of 60 grassland species in monocultures and 16-species mixtures. We examined plant biomass, species-specific traits (plant height, specific leaf area (SLA), root aerenchyma, starch content) and soil porosity. We found that, on average, plant species were less negatively affected by the flood when grown in higher-diversity plots in July 2013. By September 2013, grasses were unaffected by the flood regardless of plant diversity, and legumes were severely negatively affected regardless of plant diversity. Plants with greater SLA and more root aerenchyma performed better in September. Soil porosity was higher in higher-diversity plots and had a positive effect on plant performance. As floods become more frequent and severe in the future, growing flood-sensitive plants in higher-diversity communities and in soil with greater soil aeration may attenuate the most negative effects of flooding.

  2. Fuel breaks affect nonnative species abundance in Californian plant communities

    USGS Publications Warehouse

    Merriam, K.E.; Keeley, J.E.; Beyers, J.L.

    2006-01-01

    We evaluated the abundance of nonnative plants on fuel breaks and in adjacent untreated areas to determine if fuel treatments promote the invasion of nonnative plant species. Understanding the relationship between fuel treatments and nonnative plants is becoming increasingly important as federal and state agencies are currently implementing large fuel treatment programs throughout the United States to reduce the threat of wildland fire. Our study included 24 fuel breaks located across the State of California. We found that nonnative plant abundance was over 200% higher on fuel breaks than in adjacent wildland areas. Relative nonnative cover was greater on fuel breaks constructed by bulldozers (28%) than on fuel breaks constructed by other methods (7%). Canopy cover, litter cover, and duff depth also were significantly lower on fuel breaks constructed by bulldozers, and these fuel breaks had significantly more exposed bare ground than other types of fuel breaks. There was a significant decline in relative nonnative cover with increasing distance from the fuel break, particularly in areas that had experienced more numerous fires during the past 50 years, and in areas that had been grazed. These data suggest that fuel breaks could provide establishment sites for nonnative plants, and that nonnatives may invade surrounding areas, especially after disturbances such as fire or grazing. Fuel break construction and maintenance methods that leave some overstory canopy and minimize exposure of bare ground may be less likely to promote nonnative plants. ?? 2006 by the Ecological Society of America.

  3. Plant community and target species affect responses to restoration strategies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increases in Kentucky bluegrass and smooth brome on northern Great Plains rangelands have the potential to negatively impact ecosystem function, lower plant diversity and alter seasonal forage distribution, but control strategies are lacking in the region. A project was initiated on a heavily invad...

  4. Arrival order among native plant functional groups does not affect invasibility of constructed dune communities.

    PubMed

    Mason, T J; French, K; Jolley, D

    2013-10-01

    Different arrival order scenarios of native functional groups to a site may influence both resource use during development and final community structure. Arrival order may then indirectly influence community resistance to invasion. We present a mesocosm experiment of constructed coastal dune communities that monitored biotic and abiotic responses to different arrival orders of native functional groups. Constructed communities were compared with unplanted mesocosms. We then simulated a single invasion event by bitou (Chrysanthemoides monilifera ssp. rotundata), a dominant exotic shrub of coastal communities. We evaluated the hypothesis that plantings with simultaneous representation of grass, herb and shrub functional groups at the beginning of the experiment would more completely sequester resources and limit invasion than staggered plantings. Staggered plantings in turn would offer greater resource use and invasion resistance than unplanted mesocosms. Contrary to our expectations, there were few effects of arrival order on abiotic variables for the duration of the experiment and arrival order was unimportant in final community invasibility. All planted mesocosms supported significantly more invader germinants and significantly less invader abundance than unplanted mesocosms. Native functional group plantings may have a nurse effect during the invader germination and establishment phase and a competitive function during the invader juvenile and adult phase. Arrival order per se did not affect resource use and community invasibility in our mesocosm experiment. While grass, herb and shrub functional group plantings will not prevent invasion success in restored communities, they may limit final invader biomass.

  5. Different degrees of plant invasion significantly affect the richness of the soil fungal community.

    PubMed

    Si, Chuncan; Liu, Xueyan; Wang, Congyan; Wang, Lei; Dai, Zhicong; Qi, Shanshan; Du, Daolin

    2013-01-01

    Several studies have shown that soil microorganisms play a key role in the success of plant invasion. Thus, ecologists have become increasingly interested in understanding the ecological effects of biological invasion on soil microbial communities given continuing increase in the effects of invasive plants on native ecosystems. This paper aims to provide a relatively complete depiction of the characteristics of soil microbial communities under different degrees of plant invasion. Rhizospheric soils of the notorious invasive plant Wedelia trilobata with different degrees of invasion (uninvaded, low-degree, and high-degree using its coverage in the invaded ecosystems) were collected from five discrete areas in Hainan Province, P. R. China. Soil physicochemical properties and community structure of soil microorganisms were assessed. Low degrees of W. trilobata invasion significantly increased soil pH values whereas high degrees of invasion did not significantly affected soil pH values. Moreover, the degree of W. trilobata invasion exerted significant effects on soil Ca concentration but did not significantly change other indices of soil physicochemical properties. Low and high degrees of W. trilobata invasion increased the richness of the soil fungal community but did not pose obvious effects on the soil bacterial community. W. trilobata invasion also exerted obvious effects on the community structure of soil microorganisms that take part in soil nitrogen cycling. These changes in soil physicochemical properties and community structure of soil microbial communities mediated by different degrees of W. trilobata invasion may present significant functions in further facilitating the invasion process.

  6. Different Degrees of Plant Invasion Significantly Affect the Richness of the Soil Fungal Community

    PubMed Central

    Si, Chuncan; Liu, Xueyan; Wang, Congyan; Wang, Lei; Dai, Zhicong; Qi, Shanshan; Du, Daolin

    2013-01-01

    Several studies have shown that soil microorganisms play a key role in the success of plant invasion. Thus, ecologists have become increasingly interested in understanding the ecological effects of biological invasion on soil microbial communities given continuing increase in the effects of invasive plants on native ecosystems. This paper aims to provide a relatively complete depiction of the characteristics of soil microbial communities under different degrees of plant invasion. Rhizospheric soils of the notorious invasive plant Wedelia trilobata with different degrees of invasion (uninvaded, low-degree, and high-degree using its coverage in the invaded ecosystems) were collected from five discrete areas in Hainan Province, P. R. China. Soil physicochemical properties and community structure of soil microorganisms were assessed. Low degrees of W. trilobata invasion significantly increased soil pH values whereas high degrees of invasion did not significantly affected soil pH values. Moreover, the degree of W. trilobata invasion exerted significant effects on soil Ca concentration but did not significantly change other indices of soil physicochemical properties. Low and high degrees of W. trilobata invasion increased the richness of the soil fungal community but did not pose obvious effects on the soil bacterial community. W. trilobata invasion also exerted obvious effects on the community structure of soil microorganisms that take part in soil nitrogen cycling. These changes in soil physicochemical properties and community structure of soil microbial communities mediated by different degrees of W. trilobata invasion may present significant functions in further facilitating the invasion process. PMID:24392015

  7. Plant hybrid zones affect biodiversity: Tools for a genetic-based understanding of community structure

    SciTech Connect

    Whitham, T.G.; Martinsen, G.D.; Keim, P.; Floate, K.D.; Dungey, H.S. |; Potts, B.M.

    1999-03-01

    Plant hybrid zones are dynamic centers of ecological and evolutionary processes for plants and their associated communities. Studies in the wild and in gardens with synthetic crosses showed that hybrid eucalypts supports the greatest species richness and abundances of insect and fungal taxa. In an updated review of 152 case studies of taxa associated with diverse hybridizing systems, there were 43 (28%) cases of hybrids being more susceptible than their parent species, 7 (5%) resistant, 35 (23%) additive, 35 (23%) dominant, and 32 (21%) showed no response to hybridization. Thus, most taxa respond to hybrids in ways that result in equal or greater abundance, and hybrids tend to accumulate the taxa of their parent species. These studies suggest that genetic-based plant traits affect the distribution of many species and that the variation in hybrids can be used as tools to examine the genetic components of community structure and biodiversity.

  8. Realistic diversity loss and variation in soil depth independently affect community-level plant nitrogen use.

    PubMed

    Selmants, Paul C; Zavaleta, Erika S; Wolf, Amelia A

    2014-01-01

    Numerous experiments have demonstrated that diverse plant communities use nitrogen (N) more completely and efficiently, with implications for how species conservation efforts might influence N cycling and retention in terrestrial ecosystems. However, most such experiments have randomly manipulated species richness and minimized environmental heterogeneity, two design aspects that may reduce applicability to real ecosystems. Here we present results from an experiment directly comparing how realistic and randomized plant species losses affect plant N use across a gradient of soil depth in a native-dominated serpentine grassland in California. We found that the strength of the species richness effect on plant N use did not increase with soil depth in either the realistic or randomized species loss scenarios, indicating that the increased vertical heterogeneity conferred by deeper soils did not lead to greater complementarity among species in this ecosystem. Realistic species losses significantly reduced plant N uptake and altered N-use efficiency, while randomized species losses had no effect on plant N use. Increasing soil depth positively affected plant N uptake in both loss order scenarios but had a weaker effect on plant N use than did realistic species losses. Our results illustrate that realistic species losses can have functional consequences that differ distinctly from randomized losses, and that species diversity effects can be independent of and outweigh those of environmental heterogeneity on ecosystem functioning. Our findings also support the value of conservation efforts aimed at maintaining biodiversity to help buffer ecosystems against increasing anthropogenic N loading.

  9. [Noise-reduction function and its affecting factors of urban plant communities in Shanghai].

    PubMed

    Zhang, Qing-Fei; Zheng, Si-Jun; Xia, Lei; Wu, Hai-Ping; Zhang, Ming-Li; Li, Ming-Sheng

    2007-10-01

    The factor analysis on the relationships between excess noise attenuation (decrement after noise propagating 30 m) and 8 structural characteristics of 19 urban plant communities in Shanghai showed that all the plant communities had notable effects on reducing noise, and the noise attenuation ability of the communities was significantly higher than that of lawn (P < 0.01). The plant communities could be divided into three groups base on their noise attenuation ability, i.e., those of > or = 10 dB(A), 6-10 dB(A), and < or = 6 dB(A). The main factors affecting the noise attenuation ability of the communities were leaf area index, average bifurcate height, average height, coverage, and average canopy diameter, and their correlation coefficients with noise attenuation were 0.343, 0.318, 0.285, 0.226 and 0.193, respectively. These five factors had a cumulative contribution rate of 65.47%, suggesting that they should be considered in stress when designing urban greenbelt for noise reduction.

  10. The root herbivore history of the soil affects the productivity of a grassland plant community and determines plant response to new root herbivore attack.

    PubMed

    Sonnemann, Ilja; Hempel, Stefan; Beutel, Maria; Hanauer, Nicola; Reidinger, Stefan; Wurst, Susanne

    2013-01-01

    Insect root herbivores can alter plant community structure by affecting the competitive ability of single plants. However, their effects can be modified by the soil environment. Root herbivory itself may induce changes in the soil biota community, and it has recently been shown that these changes can affect plant growth in a subsequent season or plant generation. However, so far it is not known whether these root herbivore history effects (i) are detectable at the plant community level and/or (ii) also determine plant species and plant community responses to new root herbivore attack. The present greenhouse study determined root herbivore history effects of click beetle larvae (Elateridae, Coleoptera, genus Agriotes) in a model grassland plant community consisting of six common species (Achillea millefolium, Plantago lanceolata, Taraxacum officinale, Holcus lanatus, Poa pratensis, Trifolium repens). Root herbivore history effects were generated in a first phase of the experiment by growing the plant community in soil with or without Agriotes larvae, and investigated in a second phase by growing it again in the soils that were either Agriotes trained or not. The root herbivore history of the soil affected plant community productivity (but not composition), with communities growing in root herbivore trained soil producing more biomass than those growing in untrained soil. Additionally, it influenced the response of certain plant species to new root herbivore attack. Effects may partly be explained by herbivore-induced shifts in the community of arbuscular mycorrhizal fungi. The root herbivore history of the soil proved to be a stronger driver of plant growth on the community level than an actual root herbivore attack which did not affect plant community parameters. History effects have to be taken into account when predicting the impact of root herbivores on grasslands.

  11. The Root Herbivore History of the Soil Affects the Productivity of a Grassland Plant Community and Determines Plant Response to New Root Herbivore Attack

    PubMed Central

    Sonnemann, Ilja; Hempel, Stefan; Beutel, Maria; Hanauer, Nicola; Reidinger, Stefan; Wurst, Susanne

    2013-01-01

    Insect root herbivores can alter plant community structure by affecting the competitive ability of single plants. However, their effects can be modified by the soil environment. Root herbivory itself may induce changes in the soil biota community, and it has recently been shown that these changes can affect plant growth in a subsequent season or plant generation. However, so far it is not known whether these root herbivore history effects (i) are detectable at the plant community level and/or (ii) also determine plant species and plant community responses to new root herbivore attack. The present greenhouse study determined root herbivore history effects of click beetle larvae (Elateridae, Coleoptera, genus Agriotes) in a model grassland plant community consisting of six common species (Achillea millefolium, Plantago lanceolata, Taraxacum officinale, Holcus lanatus, Poa pratensis, Trifolium repens). Root herbivore history effects were generated in a first phase of the experiment by growing the plant community in soil with or without Agriotes larvae, and investigated in a second phase by growing it again in the soils that were either Agriotes trained or not. The root herbivore history of the soil affected plant community productivity (but not composition), with communities growing in root herbivore trained soil producing more biomass than those growing in untrained soil. Additionally, it influenced the response of certain plant species to new root herbivore attack. Effects may partly be explained by herbivore-induced shifts in the community of arbuscular mycorrhizal fungi. The root herbivore history of the soil proved to be a stronger driver of plant growth on the community level than an actual root herbivore attack which did not affect plant community parameters. History effects have to be taken into account when predicting the impact of root herbivores on grasslands. PMID:23441201

  12. Plant age and genotype affect the bacterial community composition in the tuber rhizosphere of field-grown sweet potato plants.

    PubMed

    Marques, Joana M; da Silva, Thais F; Vollu, Renata E; Blank, Arie F; Ding, Guo-Chun; Seldin, Lucy; Smalla, Kornelia

    2014-05-01

    The hypothesis that sweet potato genotypes containing different starch yields in their tuberous roots can affect the bacterial communities present in the rhizosphere (soil adhering to tubers) was tested in this study. Tuberous roots of field-grown sweet potato of genotypes IPB-149 (commercial genotype), IPB-052, and IPB-137 were sampled three and six months after planting and analyzed by denaturing gradient gel electrophoresis (DGGE) and pyrosequencing analysis of 16S rRNA genes PCR-amplified from total community DNA. The statistical analysis of the DGGE fingerprints showed that both plant age and genotypes influenced the bacterial community structure in the tuber rhizosphere. Pyrosequencing analysis showed that the IPB-149 and IPB-052 (both with high starch content) displayed similar bacterial composition in the tuber rhizosphere, while IPB-137 with the lowest starch content was distinct. In comparison with bulk soil, higher 16S rRNA gene copy numbers (qPCR) and numerous genera with significantly increased abundance in the tuber rhizosphere of IPB-137 (Sphingobium, Pseudomonas, Acinetobacter, Stenotrophomonas, Chryseobacterium) indicated a stronger rhizosphere effect. The genus Bacillus was strongly enriched in the tuber rhizosphere samples of all sweet potato genotypes studied, while other genera showed a plant genotype-dependent abundance. This is the first report on the molecular identification of bacteria being associated with the tuber rhizosphere of different sweet potato genotypes.

  13. Species-abundance--seed-size patterns within a plant community affected by grazing disturbance.

    PubMed

    Wu, Gao-lin; Shang, Zhan-huan; Zhu, Yuan-jun; Ding, Lu-ming; Wang, Dong

    2015-04-01

    Seed size has been advanced as a key factor that influences the dynamics of plant communities, but there are few empirical or theoretical predictions of how community dynamics progress based on seed size patterns. Information on the abundance of adults, seedlings, soil seed banks, seed rains, and the seed mass of 96 species was collected in alpine meadows of the Qinghai-Tibetan Plateau (China), which had different levels of grazing disturbance. The relationships between seed-mass-abundance patterns for adults, seedlings, the soil seed bank, and seed rain in the plant community were evaluated using regression models. Results showed that grazing levels affected the relationship between seed size and abundance properties of adult species, seedlings, and the soil seed bank, suggesting that there is a shift in seed-size--species-abundance relationships as a response to the grazing gradient. Grazing had no effect on the pattern of seed-size-seed-rain-abundance at four grazing levels. Grazing also had little effect on the pattern of seed-size--species-abundance and pattern of seed-size--soil-seed-bank-abundance in meadows with no grazing, light grazing, and moderate grazing), but there was a significant negative effect in meadows with heavy grazing. Grazing had little effect on the pattern of seed-size--seedling-abundance with no grazing, but had significant negative effects with light, moderate, and heavy grazing, and the |r| values increased with grazing levels. This indicated that increasing grazing pressure enhanced the advantage of smaller-seeded species in terms of the abundances of adult species, seedlings, and soil seed banks, whereas only the light grazing level promoted the seed rain abundance of larger-seeded species in the plant communities. This study suggests that grazing disturbances are favorable for increasing the species abundance for smaller-seeded species but not for the larger-seeded species in an alpine meadow community. Hence, there is a clear

  14. Defoliation negatively affects plant growth and the ectomycorrhizal community of Pinus pinaster in Spain.

    PubMed

    Pestaña, Montserrat; Santolamazza-Carbone, Serena

    2011-03-01

    In this work, by artificially reproducing severe (75%) and moderate (25%) defoliation on maritime pines Pinus pinaster in NW Spain, we investigated, under natural conditions, the consequences of foliage loss on reproduction, abundance, diversity and richness of the fungal symbionts growing belowground and aboveground. The effect of defoliation on tree growth was also assessed. Mature needles were clipped during April 2007 and 2008. Root samples were collected in June-July 2007 and 2008. Collection of sporocarps was performed weekly from April 2007 to April 2009. Taxonomic identity of ectomycorrhizal fungi was assessed by using the internal transcribed spacer (ITS) regions of rDNA through the polymerase chain reaction (PCR) method, subsequent direct sequencing and BLAST search. Ectomycorrhizal colonization was significantly reduced (from 54 to 42%) in 2008 by 75% defoliation, accompanied with a decline in species richness and diversity. On the other hand, sporocarp abundance, richness and diversity were not affected by foliage loss. Some ECM fungal symbionts, which are assumed to have a higher carbon cost according to the morphotypes structure, were reduced due to severe (75%) defoliation. Furthermore, 75% foliage loss consistently depressed tree growth, which in turn affected the ectomycorrhizal growth pattern. Defoliation impact on ECM symbionts largely depends on the percentage of foliage removal and on the number of defoliation bouts. Severe defoliation (75%) in the short term (2 years) changed the composition of the ECM community likely because root biomass would be adjusted to lower levels in parallel with the depletion of the aboveground plant biomass, which probably promoted the competition among mycorrhizal types for host resources. The persistence of fungal biomass in mycorrhizal roots would be crucial for nutrient up-take and recovery from defoliation stress of the host plants.

  15. Drought induced changes of plant belowground carbon allocation affect soil microbial community function in a subalpine meadow

    NASA Astrophysics Data System (ADS)

    Fuchslueger, L.; Bahn, M.; Fritz, K.; Hasibeder, R.; Richter, A.

    2012-12-01

    There is growing evidence that climate extremes may affect ecosystem carbon dynamics more strongly than gradual changes in temperatures or precipitation. Climate projections suggest more frequent heat waves accompanied by extreme drought periods in many parts of Europe, including the Alps. Drought is considered to decrease plant C uptake and turnover, which may in turn decrease belowground C allocation and potentially has significant consequences for microbial community composition and functioning. However, information on effects of drought on C dynamics at the plant-soil interface in real ecosystems is still scarce. Our study aimed at understanding how summer drought affects soil microbial community composition and the uptake of recently assimilated plant C by different microbial groups in grassland. We hypothesized that under drought 1) the microbial community shifts, fungi being less affected than bacteria, 2) plants decrease belowground C allocation, which further reduces C transfer to soil microbes and 3) the combined effects of belowground C allocation, reduced soil C transport due to reduced soil moisture and shift in microbial communities cause an accumulation of extractable organic C in the soil. Our study was conducted as part of a rain-exclusion experiment in a subalpine meadow in the Austrian Central Alps. After eight weeks of rain exclusion we pulse labelled drought and control plots with 13CO2 and traced C in plant biomass, extractable organic C (EOC) and soil microbial communities using phospholipid fatty acids (PLFA). Drought induced a shift of the microbial community composition: gram-positive bacteria became more dominant, whereas gram-negative bacteria were not affected by drought. Also the relative abundance of fungal biomass was not affected by drought. While total microbial biomass (as estimated by total microbial PLFA content) increased during drought, less 13C was taken up. This reduction was pronounced for bacterial biomarkers. It reflects

  16. Agave salmiana Plant Communities in Central Mexico as Affected by Commercial Use

    NASA Astrophysics Data System (ADS)

    Martínez Salvador, Martin; Mata-González, Ricardo; Morales Nieto, Carlos; Valdez-Cepeda, Ricardo

    2012-01-01

    Agave salmiana is a native plant species harvested for the commercial production of mezcal ( Agave spirits) in the highlands of central Mexico. The objective of this study was to identify vegetation changes in natural communities where A. salmiana has been differentially harvested for commercial purposes. Three plant community categories were identified in the state of Zacatecas based on their history of A. salmiana utilization: short (less than 10 years of use), moderate (about 25 years), and long (60 or more years). Species cover, composition, and density were evaluated in field surveys by use category. A gradient of vegetation structure of the communities parallels the duration of A. salmiana use. A. salmiana density was greatest (3,125 plants ha-1) in the short-use areas and less (892 plants ha-1) in the moderate-use areas, associated with markedly greater density of shrubs (200%) and Opuntia spp. (50%) in moderate-use areas. The main shrubs were Larrea tridentata, Mimosa biuncifera, Jatropha dioica and Buddleia scordioides while the main Opuntia species were Opuntia leucotricha and Opuntia robusta. A. salmiana density was least (652 plants ha-1) in the long-use areas where shrubs were less abundant but Opuntia spp. density was 25% higher than in moderate-use areas. We suggest that shrubs may increase with moderate use creating an intermediate successional stage that facilitates the establishment of Opuntia spp. Long-term Agave use is generating new plant communities dominated by Opuntia spp. (nopaleras) as a replacement of the original communities dominated by A. salmiana (magueyeras).

  17. Agave salmiana plant communities in central Mexico as affected by commercial use.

    PubMed

    Martínez Salvador, Martin; Mata-González, Ricardo; Morales Nieto, Carlos; Valdez-Cepeda, Ricardo

    2012-01-01

    Agave salmiana is a native plant species harvested for the commercial production of mezcal (Agave spirits) in the highlands of central Mexico. The objective of this study was to identify vegetation changes in natural communities where A. salmiana has been differentially harvested for commercial purposes. Three plant community categories were identified in the state of Zacatecas based on their history of A. salmiana utilization: short (less than 10 years of use), moderate (about 25 years), and long (60 or more years). Species cover, composition, and density were evaluated in field surveys by use category. A gradient of vegetation structure of the communities parallels the duration of A. salmiana use. A. salmiana density was greatest (3,125 plants ha(-1)) in the short-use areas and less (892 plants ha(-1)) in the moderate-use areas, associated with markedly greater density of shrubs (200%) and Opuntia spp. (50%) in moderate-use areas. The main shrubs were Larrea tridentata, Mimosa biuncifera, Jatropha dioica and Buddleia scordioides while the main Opuntia species were Opuntia leucotricha and Opuntia robusta. A. salmiana density was least (652 plants ha(-1)) in the long-use areas where shrubs were less abundant but Opuntia spp. density was 25% higher than in moderate-use areas. We suggest that shrubs may increase with moderate use creating an intermediate successional stage that facilitates the establishment of Opuntia spp. Long-term Agave use is generating new plant communities dominated by Opuntia spp. (nopaleras) as a replacement of the original communities dominated by A. salmiana (magueyeras).

  18. Plant radiation history affects community assembly: evidence from the New Zealand alpine.

    PubMed

    Lee, William G; Tanentzap, Andrew J; Heenan, Peter B

    2012-08-23

    The hypothesis that early plant radiations on islands dampen diversification and reduce habitat occupancy of later radiations via niche pre-emption has never, to our knowledge, been tested. We investigated clade-level dynamics in plant radiations in the alpine zone, New Zealand. Our aim was to determine whether radiations from older colonizations influenced diversification and community dominance of species from later colonizations within a common bioclimatic zone over the past ca 10 Myr. We used stem ages derived from the phylogenies of 17 genera represented in alpine plant communities in the Murchison Mountains, Fiordland, and assessed their presence and cover in 262 (5 × 5 m) vegetation plots. Our results show clear age-related community assembly effects, whereby congenerics from older colonizing genera co-occur more frequently and with greater cover per unit area than those from younger colonizing genera. However, we find no evidence of increased species richness with age of colonization in the alpine zone. The data support priority effects via niche pre-emption among plant radiations influencing community assembly.

  19. Do postfire mulching treatments affect plant community recovery in California coastal sage scrub lands?

    PubMed

    McCullough, Sarah A; Endress, Bryan A

    2012-01-01

    In recent years, the use of postfire mulch treatments to stabilize slopes and reduce soil erosion in shrubland ecosystems has increased; however, the potential effects on plant recovery have not been examined. To evaluate the effects of mulching treatments on postfire plant recovery in southern California coastal sage scrub, we conducted a field experiment with three experimental treatments, consisting of two hydromulch products and an erosion control blanket, plus a control treatment. The area burned in 2007, and treatments were applied to six plot blocks before the 2008 growing season. Treatment effects on plant community recovery were analyzed with a mixed effects ANOVA analysis using a univariate repeated measures approach. Absolute plant cover increased from 13 to 90% by the end of the second growing season, and the mean relative cover of exotic species was 32%. The two hydromulch treatments had no effect on any plant community recovery response variable measured. For the erosion control blanket treatment, the amount of bare ground cover at the end of the second growing season was significantly lower (P = 0.01), and greater shrub height was observed (P < 0.01). We conclude that postfire mulch treatments did not provide either a major benefit or negative impact to coastal sage scrub recovery on the study area.

  20. Rhizosphere Microbial Community Composition Affects Cadmium and Zinc Uptake by the Metal-Hyperaccumulating Plant Arabidopsis halleri

    PubMed Central

    Muehe, E. Marie; Weigold, Pascal; Adaktylou, Irini J.; Planer-Friedrich, Britta; Kraemer, Ute; Kappler, Andreas

    2015-01-01

    The remediation of metal-contaminated soils by phytoextraction depends on plant growth and plant metal accessibility. Soil microorganisms can affect the accumulation of metals by plants either by directly or indirectly stimulating plant growth and activity or by (im)mobilizing and/or complexing metals. Understanding the intricate interplay of metal-accumulating plants with their rhizosphere microbiome is an important step toward the application and optimization of phytoremediation. We compared the effects of a “native” and a strongly disturbed (gamma-irradiated) soil microbial communities on cadmium and zinc accumulation by the plant Arabidopsis halleri in soil microcosm experiments. A. halleri accumulated 100% more cadmium and 15% more zinc when grown on the untreated than on the gamma-irradiated soil. Gamma irradiation affected neither plant growth nor the 1 M HCl-extractable metal content of the soil. However, it strongly altered the soil microbial community composition and overall cell numbers. Pyrosequencing of 16S rRNA gene amplicons of DNA extracted from rhizosphere samples of A. halleri identified microbial taxa (Lysobacter, Streptomyces, Agromyces, Nitrospira, “Candidatus Chloracidobacterium”) of higher relative sequence abundance in the rhizospheres of A. halleri plants grown on untreated than on gamma-irradiated soil, leading to hypotheses on their potential effect on plant metal uptake. However, further experimental evidence is required, and wherefore we discuss different mechanisms of interaction of A. halleri with its rhizosphere microbiome that might have directly or indirectly affected plant metal accumulation. Deciphering the complex interactions between A. halleri and individual microbial taxa will help to further develop soil metal phytoextraction as an efficient and sustainable remediation strategy. PMID:25595759

  1. Roads in northern hardwood forests affect adjacent plant communities and soil chemistry in proportion to the maintained roadside area.

    PubMed

    Neher, Deborah A; Asmussen, David; Lovell, Sarah Taylor

    2013-04-01

    The spatial extent of the transported materials from three road types was studied in forest soil and vegetative communities in Vermont. Hypotheses were two-fold: 1) soil chemical concentrations above background environment would reflect traffic volume and road type (highway>2-lane paved>gravel), and 2) plant communities close to the road and near roads with greater traffic will be disturbance-tolerant and adept at colonization. Soil samples were gathered from 12 randomly identified transects for each of three road types classified as "highway," "two-lane paved," and "gravel." Using GIS mapping, transects were constructed perpendicular to the road, and samples were gathered at the shoulder, ditch, backslope, 10 m from the edge of the forest, and 50 m from road center. Sample locations were analyzed for a suite of soil elements and parameters, as well as percent area coverage by plant species. The main effects from roads depended on the construction modifications required for a roadway (i.e., vegetation clearing and topography modification). The cleared area defined the type of plant community and the distance that road pollutants travel. Secondarily, road presence affected soil chemistry. Metal concentrations (e.g., Pb, Cd, Cu, and Zn) correlated positively with road type. Proximity to all road types made the soils more alkaline (pH 7.7) relative to the acidic soil of the adjacent native forest (pH 5.6). Roadside microtopography had marked effects on the composition of plant communities based on the direction of water flow. Ditch areas supported wetland plant species, greater soil moisture and sulfur content, while plant communities closer to the road were characteristic of drier upland zones. The area beyond the edge of the forest did not appear to be affected chemically or physically by any of the road types, possibly due to the dense vegetation that typically develops outside of the managed right-of-way.

  2. CO2, Temperature, and Soil Moisture Interactions Affect NDVI and Reproductive Phenology in Old-Field Plant Communities

    NASA Astrophysics Data System (ADS)

    Engel, C.; Weltzin, J.; Norby, R.

    2004-12-01

    Plant community composition and ecosystem function may be altered by global atmospheric and climate change, including increased atmospheric [CO2], temperature, and varying precipitation regimes. We are conducting an experiment at Oak Ridge National Laboratory (ORNL) utilizing open-top chambers to administer experimental treatments of elevated CO2 (+300 ppm), warming (+ 3 degrees Celsius), and varying soil moisture availability to experimental plant communities constructed of seven common old-field species, including C3 and C4 grasses, forbs, and legumes. During 2004 we monitored plant community phenology (NDVI) and plant reproductive phenology. Early in the year, NDVI was greater in wet treatment plots, and was unaffected by main effects of temperature or CO2. This result suggests that early in the season warming is insufficient to affect early canopy development. Differences in soil moisture sustained throughout the winter and into early spring may constitute an important control on early canopy greenup. Elevated CO2 alleviated detrimental effects of warming on NDVI, but only early in the season. As ambient temperatures increased, elevated temperatures negatively impacted NDVI only in the dry plots. Wetter conditions ameliorate the effects of warming on canopy greenness during the warmer seasons of the year. Warming increased rates of bolting, number of inflorescences, and time to reproductive maturity for Andropogon virginicus (a C4 bunchgrass). Solidago Canadensis (a C3 late-season forb) also produced flowers earlier in elevated temperatures. Conversely, none of the C3 grasses and forbs that bolt or flower in late spring or early summer responded to temperature or CO2. Results indicate that warming and drought may impact plant community phenology, and plant species reproductive phenology. Clearly community phenology is driven by complex interactions among temperature, water, and CO2 that change throughout the season. Our data stresses the importance of

  3. Plant Host Species and Geographic Distance Affect the Structure of Aboveground Fungal Symbiont Communities, and Environmental Filtering Affects Belowground Communities in a Coastal Dune Ecosystem.

    PubMed

    David, Aaron S; Seabloom, Eric W; May, Georgiana

    2016-05-01

    Microbial symbionts inhabit tissues of all plants and animals. Their community composition depends largely on two ecological processes: (1) filtering by abiotic conditions and host species determining the environments that symbionts are able to colonize and (2) dispersal-limitation determining the pool of symbionts available to colonize a given host and community spatial structure. In plants, the above- and belowground tissues represent such distinct habitats for symbionts that we expect different effects of filtering and spatial structuring on their symbiont communities. In this study, we characterized above- and belowground communities of fungal endophytes--fungi living asymptomatically within plants--to understand the contributions of filtering and spatial structure to endophyte community composition. We used a culture-based approach to characterize endophytes growing in leaves and roots of three species of coastal beachgrasses in dunes of the USA Pacific Northwest. For leaves, endophyte isolation frequency and OTU richness depended primarily on plant host species. In comparison, for roots, both isolation frequency and OTU richness increased from the nutrient-poor front of the dune to the higher-nutrient backdune. Endophyte community composition in leaves exhibited a distance-decay relationship across the region. In a laboratory assay, faster growth rates and lower spore production were more often associated with leaf- than root-inhabiting endophytes. Overall, our results reveal a greater importance of biotic filtering by host species and dispersal-limitation over regional geographic distances for aboveground leaf endophyte communities and stronger effects of abiotic environmental filtering and locally patchy distributions for belowground root endophyte communities.

  4. Soil contamination with olive mill wastes negatively affects microbial communities, invertebrates and plants.

    PubMed

    Hentati, Olfa; Oliveira, Vanessa; Sena, Clara; Bouji, Mohamed Seddik Mahmoud; Wali, Ahmed; Ksibi, Mohamed

    2016-10-01

    The aim of the present study was to evaluate the ecotoxicological effects of olive mill waste (OMW) on soil habitat function. To this end, soil samples from OMW evaporating ponds (S1-S5) located at Agareb (Sfax, Tunisia) and a reference soil (R) were collected. The effects of OMW on the springtails Folsomia candida (F.c.), the earthworm species Eisenia fetida (E.f.), Enchytraeus crypticus (E.c.) reproduction and on the soil living microbial communities were investigated. E.f. reproduction and tomato growth assays were performed in the reference soil amended with 0.43 to 7.60 % (wOMW/wref-soil) mass ratios of dried OMW. Changes in microbial function diversity were explored using sole-carbon-source utilization profiles (BiologEcoPlates(®)). E.f. absolutely avoided (100 %) the most polluted soil (S4) while the F.c. moderately avoided (37.5 ± 7.5 %) the same soil. E.c. reproduction in S4 was significantly lower than in S1, S2, S3 and S5, and was the highest in R soil. Estimated effect concentration EC50 for juveniles' production by E.f., and for tomato fresh weight and chlorophyll content were 0.138, 0.6 and 1.13 %, respectively. Community level physiological profiles (CLPPs) were remarkably different in R and S4 and a higher similarity was observed between soils S1, S2, S3 and S5. Principal component analysis (PCA) revealed that differences between soil microbial functional diversity were mainly due to high polyphenol concentrations, while the salinity negatively affected E.c. reproduction in OMW contaminated soils. These results clearly reflect the high toxicity of dried OMW when added to agricultural soils, causing severe threats to terrestrial ecosystem functions and services provided by invertebrates and microbial communities.

  5. Planting densities and bird and rodent absence affect size distributions of four dicots in synthetic tallgrass communities.

    PubMed

    Martínez-Garza, Cristina; Saha, Sonali; Torres, Veronica; Brown, Joel S; Howe, Henry F

    2004-05-01

    Variability in the size distributions of populations is usually studied in monocultures or in mixed plantings of two species. Variability of size distributions of populations in more complex communities has been neglected. The effects of seeding density (35 or 350 seeds/species/m2) and presence of small vertebrates on the variability of size distributions were studied for a total of 1,920 individuals of 4 species in replicated synthetic communities of 18 species in northern Illinois. End-of season height and above-ground biomass were measured for prairie perennials Dalea purpurea (purple prairie clover), Echinacea purpurea (purple coneflower), Desmanthus illinoensis (Illinois bundleflower) and Heliopsis helianthoides (early sunflower). Variability in biomass distribution of the four target species was twice as great at low than at high densities when small vertebrates were excluded. Our results suggest that inter- and intraspecific competition may affect all individuals more under high-density conditions, thereby reducing the variability in their biomass distributions within this community. This result, a consequence of plant-plant interaction, is obscured when small birds or mammals are present, presumably because either or both add variance that overwhelms the pattern.

  6. Fire and drought affect plant communities and the greenhouse gas balance in a Mediterranean shrubland

    NASA Astrophysics Data System (ADS)

    Moreno, José M.; Parra, Antonio; Dannenmann, Michael; Ramírez, David A.; Diaz-Pines, Eugenio; Tejedor, Javier; Kitzler, Barbara; Karhu, Kristina; Resco, Victor; Povoas, Luciano

    2010-05-01

    Predicted changes in the seasonality and amount of rainfall under a changing climate have the potential to dramatically alter ecosystem function and species composition. Moreover, in fire-prone ecosystems, the joint effects of fire and increasing aridity may create irreversible changes to the services these ecosystems provide. To understand the effects of increasing drought and fire in a Mediterranean shrubland, we implemented an automated rainfall manipulation system, with rain-out shelters which automatically fold and unfold when conditions are rainy and dry, respectively. In January 2009, we implemented five different treatments, where annual precipitation was reduced by diminishing summer rainfall from the long-term historical average, up to a 40% reduction, following IPCC scenarios. In September 2009, we uninstalled all the shelters to burn the different plots, and reinstalled the shelters immediately afterwards. In this talk, we will present the preliminary results of an integrated experiment which aims at understanding the concomitant effects of fire and different drought intensities on the species composition and greenhouse gas balance (CO2, N2O and CH4) of a Mediterranean shrubland. We observed that plant growth was more severely affected by drought in the more shallow-rooted, malacophyllous shrub (from 116 to -7.2 mg/g/d in Cistus ladanifer), than in a deeper-rooted heather (from 5.5 to 66.9 mg/g/day in Erica arborea). This growth response was mediated by species-specific differences in hydraulics, leaf morphology and photosynthetic gas exchange of each species. Analyses of changes in species composition after fire are currently undergoing. The precipitation reduction treatments exerted drought stress on CH4 oxidizing microorganisms and thus reduced the CH4 sink strength of the ecosystem during the pre-fire period. Furthermore, the net CH4 uptake at the soil-atmosphere interface was reduced by the fire for a period of at least one month. Pedosphere

  7. Denitrification potential and organic matter as affected by vegetation community, wetland age, and plant introduction in created wetlands.

    PubMed

    Hernandez, Maria E; Mitsch, William J

    2007-01-01

    Denitrification potential (DP) and organic matter (OM) in soils were compared in three different vegetation communities-emergent macrophyte, open water, and forested edge-in two 10-yr-old created riverine wetlands. Organic matter, cold water-extractable organic matter (CWEOM), anaerobic mineralizable carbon (AnMC), and DP varied significantly (P<0.05) among vegetation communities. The surface (0 to 9 cm) soils in the emergent macrophyte community (EMC) showed highest DP (0.07+/-0.01 mg N h-1 kg-1), OM (84.90+/-5.60 g kg-1), CWEOM (1.12+/-0.20 g kg-1), and AnMC (1.50+/-0.10 mg C h-1 kg-1). In the deeper layer (9 to 18 cm), DP and CWEOM (0.04+/-0.01 mg N h-1 kg-1 and 1.13+/-0.20 g kg-1, respectively) were significantly higher in the open water community (OWC) than in the emergent macrophyte and forested edge communities. Plant introduction did not affect DP or OM content and characteristics. After 10 yr of wetland development, mean DP increased 25-fold in the surface layer (from 0.002 to 0.053 mg N h-1 kg-1); OM content more than doubled to 90.80+/-19.22 g kg-1, and CWEOM and HWEOM increased 2.5 and 2.7 times respectively from 1993 (prewetland conditions) to 2004. Humic acids were the most abundant form of OM in 2004 and 1993 samples. Significant (P<0.05) positive relationships between DP and OM, CWEOM, and AnMC were found in the surface layer; in the 9- to 18-cm layer, significant positive relationships were found between DP and CWEOM and AnMC.

  8. The community structure of endophytic bacteria in different parts of Huanglongbing-affected citrus plants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The analyses methods of Pearson correlation coefficient (PCC), hierarchical cluster analysis and diversity index were used to study the relevance between citrus huanglongbing (HLB) and the endophytic bacteria in different branches and leaves as well as roots of huanglongbing (HLB)-affected citrus tr...

  9. WHEAT LEAF RUST SEVERITY AS AFFECTED BY PLANT DENSITY AND SPECIES PROPORTION IN SIMPLE COMMUNITIES OF WHEAT AND WILD OATS

    EPA Science Inventory

    While it is generally accepted that dense stands of plants exacerbate epidemics caused by foliar pathogens, there is little experimental evidence to support this view. We grew model plant communities consisting of wheat and wild oats at different densities and proportions and exp...

  10. WHEAT LEAF RUST SEVERITY AS AFFECTED BY PLANT DENSITY AND SPECIES PROPORTION IN SIMPLE COMMUNITIES OF WHEAT AND WILD OATS

    EPA Science Inventory

    While it is generally accepted that dense stands of plants exacerbate epidermics caused by foliar pathogens, there is little experimental evidence to support this view. We grew model plant communities consisting of wheat and wild oats at different densities and proportions and ex...

  11. 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

  12. How does altered precipitation and annual grass invasion affect plant N uptake in a native semi-arid shrub community?

    NASA Astrophysics Data System (ADS)

    Mauritz, M.; Lipson, D.; Cleland, E. E.

    2012-12-01

    Climate change is expected to alter precipitation patterns, which will change the timing and amount of plant resources. Precipitation patterns determine water and nitrogen (N) availability, because water stimulates microbial N turnover and N transport. In order for plants to utilize water and N, they must coincide with the phenology and meet physiological requirements of the plant. As resource supply shifts, differences in species' ability to acquire resources will affect plant community composition. Semiarid ecosystems, such as shrublands in Southern California, are particularly sensitive to shifts in precipitation because they are severely water limited. This study takes advantage of the altered phenology and resource demands presented by invasive annual grasses in a native semiarid shrubland. The goal is to understand how altered precipitation patterns affect plant N uptake. Rainfall levels were manipulated to 50% and 150% of ambient levels. It is expected that higher rainfall levels promote annual grass invasion because grasses have higher water and N requirements and begin to grow earlier in the season than shrubs. A 15N tracer was added with the first rain event and plant samples were collected regularly to track the movement of N into the plants. Net soil N accumulation was determined using resin bags. Invasive grasses altered the timing and amount of N uptake but amount of rainfall had less effect on N distribution. 15N was detected sooner and at higher level in grasses than shrubs. 24hours after the first rain event 15N was detectable in grasses, 15N accumulated rapidly and peaked 2 months earlier than shrubs. Shrub 15N levels remained at pre-rain event levels for the first 2 months and began to increase at the beginning of spring, peak mid-spring and decline as the shrubs entered summer dormancy. One year later 15N levels in annual grass litter remained high, while 15N levels in shrubs returned to initial background levels as a result of resorption. 15N

  13. Community structure affects behavior.

    PubMed

    Jaenson, C

    1991-06-01

    AID's prevention efforts can benefit from taking into account 5 main aspects (KEPRA) of community structure identified by anthropologists: 1) kinship patterns, 2) economics, 3) politics, 4) religion, and 5) associations. For example, in Uganda among the Basoga and paternal aunt or senga is responsible for female sex education. Such culturally determined patterns need to be targeted in order to enhance education and effectiveness. Economics can reflect differing systems of family support through sexual means. The example given involves a poor family with a teenager in Thailand who exchanges a water buffalo or basic necessity for this daughter's prostitution. Politics must be considered because every society identifies people who have the power to persuade, influence, exchange resources, coerce, or in some way get people to do what is wanted. Utilizing these resources whether its ministers of health, factory owners, or peers is exemplified in the Monterey, Mexico factor floor supervisor and canteen worker introducing to workers the hows and whys of a new AID's education program. His peer status will command more respect than the director with direct authority. Religious beliefs have explanations for causes of sickness or disease, or provide instruction in sex practices. The example given is of a health workers in Uganda discussing AIDS with rural women by saying that we all know that disease and deaths are caused by spells. "But not AIDS - slim. AIDS is different." Associations can help provide educational, economic, and emotional assistance to the AID's effort or families affected.

  14. Plant assemblage composition and soil P concentration differentially affect communities of AM and total fungi in a semi-arid grassland.

    PubMed

    Klabi, Rim; Bell, Terrence H; Hamel, Chantal; Iwaasa, Alan; Schellenberg, Mike; Raies, Aly; St-Arnaud, Marc

    2015-01-01

    Adding inorganic P- and N-fixing legumes to semi-arid grasslands can increase forage yield, but soil nutrient concentrations and plant cover may also interact to modify soil fungal populations, impacting short- and long-term forage production. We tested the effect of plant assemblage (seven native grasses, seven native grasses + the domesticated N-fixing legume Medicago sativa, seven native grasses + the native N-fixing legume Dalea purpurea or the introduced grass Bromus biebersteinii + M. sativa) and soil P concentration (addition of 0 or 200 P2O5 kg ha(-1) at sowing) on the diversity and community structure of arbuscular mycorrhizal (AM) fungi and total fungi over two consecutive years, using 454-pyrosequencing of 18S rDNA and ITS amplicons. Treatment effects were stronger in the wet year (2008) than the dry year (2009). The presence of an N-fixing legume with native grasses generally increased AM fungal diversity, while the interaction between soil P concentration and plant assemblage modified total fungal community structure in 2008. Excluding interannual variations, which are likely driven by moisture and plant productivity, AM fungal communities in semi-arid grasslands appear to be primarily affected by plant assemblage composition, while the composition of other fungi is more closely linked to soil P.

  15. Plant Communities of Rough Rock.

    ERIC Educational Resources Information Center

    Jacobs, Linda

    A unit of study on plants grown in the Navajo community of Rough Rock, Arizona, is presented in sketches providing the common Navajo name for the plant, a literal English translation, the English name of the plant, and the Latin name. A brief description of each plant includes where the plant grows, how the Navajos use the plant, and the color and…

  16. Pyrodiversity begets plant-pollinator community diversity.

    PubMed

    Ponisio, Lauren C; Wilkin, Kate; M'Gonigle, Leithen K; Kulhanek, Kelly; Cook, Lindsay; Thorp, Robbin; Griswold, Terry; Kremen, Claire

    2016-05-01

    negatively affect the richness of plant-pollinator communities across large spatial scales.

  17. Industrial contaminants and risks to plant communities

    SciTech Connect

    Vedagiri, U.

    1994-12-31

    Much of the ecological risk assessment work being done today is focused on invertebrates, herbivores and top carnivores at a site. The ecosystem is treated minimally as a backdrop for site characterization. Effects on vegetation, when considered, are mostly confined to single species toxicity tests. However, plant community-based assessment endpoints are also highly desirable for ERAs. This paper will present examples and case studies of metal, pesticide and organic contamination to illustrate the following: (a) The nature of the plant community is integral to defining the character and biogeochemistry of ecosystems and in governing the heterotrophic species composition and food webs occurring at a site, (b) impacts to the vegetation community affect not only the habitats and food webs, but also contaminant fate, transport and ecotoxicity, and assessment of the plant communities at a site is an essential part of the problem formulation, exposure, effects and risk characterization phases of a risk assessment.

  18. Air Pollution Affects Community Health

    ERIC Educational Resources Information Center

    Shy, Carl M.; Finklea, John F.

    1973-01-01

    Community Health and Environmental Surveillance System (CHESS), a nationwide program relating community health to environmental quality, is designed to evaluate existing environmental standards, obtain health intelligence for new standards, and document health benefits of air pollution control. (BL)

  19. A 3-year study reveals that plant growth stage, season and field site affect soil fungal communities while cultivar and GM-trait have minor effects.

    PubMed

    Hannula, Silja Emilia; de Boer, Wietse; van Veen, Johannes

    2012-01-01

    In this three year field study the impact of different potato (Solanum tuberosum L.) cultivars including a genetically modified (GM) amylopectin-accumulating potato line on rhizosphere fungal communities are investigated using molecular microbiological methods. The effects of growth stage of a plant, soil type and year on the rhizosphere fungi were included in this study. To compare the effects, one GM cultivar, the parental isoline, and four non-related cultivars were planted in the fields and analysed using T-RFLP on the basis of fungal phylum specific primers combined with multivariate statistical methods. Additionally, fungal biomass and some extracellular fungal enzymes (laccases, Mn-peroxidases and cellulases) were quantified in order to gain insight into the function of the fungal communities. Plant growth stage and year (and agricultural management) had the strongest effect on both diversity and function of the fungal communities while the GM-trait studied was the least explanatory factor. The impact of cultivar and soil type was intermediate. Occasional differences between cultivars, the amylopectin-accumulating potato line, and its parental variety were detected, but these differences were mostly transient in nature and detected either only in one soil, one growth stage or one year.

  20. A 3-Year Study Reveals That Plant Growth Stage, Season and Field Site Affect Soil Fungal Communities while Cultivar and GM-Trait Have Minor Effects

    PubMed Central

    Hannula, Silja Emilia; de Boer, Wietse; van Veen, Johannes

    2012-01-01

    In this three year field study the impact of different potato (Solanum tuberosum L.) cultivars including a genetically modified (GM) amylopectin-accumulating potato line on rhizosphere fungal communities are investigated using molecular microbiological methods. The effects of growth stage of a plant, soil type and year on the rhizosphere fungi were included in this study. To compare the effects, one GM cultivar, the parental isoline, and four non-related cultivars were planted in the fields and analysed using T-RFLP on the basis of fungal phylum specific primers combined with multivariate statistical methods. Additionally, fungal biomass and some extracellular fungal enzymes (laccases, Mn-peroxidases and cellulases) were quantified in order to gain insight into the function of the fungal communities. Plant growth stage and year (and agricultural management) had the strongest effect on both diversity and function of the fungal communities while the GM-trait studied was the least explanatory factor. The impact of cultivar and soil type was intermediate. Occasional differences between cultivars, the amylopectin-accumulating potato line, and its parental variety were detected, but these differences were mostly transient in nature and detected either only in one soil, one growth stage or one year. PMID:22529898

  1. Impacts of parasitic plants on natural communities.

    PubMed

    Press, Malcolm C; Phoenix, Gareth K

    2005-06-01

    Parasitic plants have profound effects on the ecosystems in which they occur. They are represented by some 4000 species and can be found in most major biomes. They acquire some or all of their water, carbon and nutrients via the vascular tissue of the host's roots or shoots. Parasitism has major impacts on host growth, allometry and reproduction, which lead to changes in competitive balances between host and nonhost species and therefore affect community structure, vegetation zonation and population dynamics. Impacts on hosts may further affect herbivores, pollinators and seed vectors, and the behaviour and diversity of these is often closely linked to the presence and abundance of parasitic plants. Parasitic plants can therefore be considered as keystone species. Community impacts are mediated by the host range of the parasite (the diversity of species that can potentially act as hosts) and by their preference and selection of particular host species. Parasitic plants can also alter the physical environment around them--including soil water and nutrients, atmospheric CO2 and temperature--and so may also be considered as ecosystem engineers. Such impacts can have further consequences in altering the resource supply to and behaviour of other organisms within parasitic plant communities.

  2. ASSESSING OFF-TARGET IMPACTS OF HERBICIDE DRIFT ON NATIVE PLANTS - IMPLICATIONS FOR PLANT COMMUNITIES AND WILDLIFE

    EPA Science Inventory

    The off target movement of herbicidess onto nontarget vegetation can affect native plants, plant communities and ecosystems. Within the agroecosystem, plants provide the basis for food and shelter for wildlife. The risk assessment process to determine potential pesticide impacts...

  3. The organization of plant communities: negative plant-soil feedbacks and semiarid grasslands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Estimates of species losses and evidence of positive plant diversity-productivity relationships have spurred interest in understanding the mechanism(s) regulating species coexistence and relative abundance. Plant-soil biota feedbacks appear to affect plant diversity and community structure by eithe...

  4. Complementarity among plant growth promoting traits in rhizospheric bacterial communities promotes plant growth.

    PubMed

    Singh, Mangal; Awasthi, Ashutosh; Soni, Sumit K; Singh, Rakshapal; Verma, Rajesh K; Kalra, Alok

    2015-10-27

    An assessment of roles of rhizospheric microbial diversity in plant growth is helpful in understanding plant-microbe interactions. Using random combinations of rhizospheric bacterial species at different richness levels, we analysed the contribution of species richness, compositions, interactions and identity on soil microbial respiration and plant biomass. We showed that bacterial inoculation in plant rhizosphere enhanced microbial respiration and plant biomass with complementary relationships among bacterial species. Plant growth was found to increase linearly with inoculation of rhizospheric bacterial communities with increasing levels of species or plant growth promoting trait diversity. However, inoculation of diverse bacterial communities having single plant growth promoting trait, i.e., nitrogen fixation could not enhance plant growth over inoculation of single bacteria. Our results indicate that bacterial diversity in rhizosphere affect ecosystem functioning through complementary relationship among plant growth promoting traits and may play significant roles in delivering microbial services to plants.

  5. Plant-fungus mutualism affects spider composition in successional fields.

    PubMed

    Finkes, Laura K; Cady, Alan B; Mulroy, Juliana C; Clay, Keith; Rudgers, Jennifer A

    2006-03-01

    Mutualistic symbionts are widespread in plants and may have strong, bottom-up influences on community structure. Here we show that a grass-endophyte mutualism shifts the composition of a generalist predator assemblage. In replicated, successional fields we manipulated endophyte infection by Neotyphodium coenophialum in a dominant, non-native plant (Lolium arundinaceum). We compared the magnitude of the endophyte effect with manipulations of thatch biomass, a habitat feature of known importance to spiders. The richness of both spider families and morphospecies was greater in the absence of the endophyte, although total spider abundance was not affected. Thatch removal reduced both spider abundance and richness, and endophyte and thatch effects were largely additive. Spider families differed in responses, with declines in Linyphiidae and Thomisidae due to the endophyte and declines in Lycosidae due to thatch removal. Results demonstrate that the community impacts of non-native plants can depend on plants' mutualistic associates, such as fungal endophytes.

  6. Vertebrate herbivores influence soil nematodes by modifying plant communities.

    PubMed

    Veen, G F; Olff, Han; Duyts, Henk; van der Putten, Wim H

    2010-03-01

    Abiotic soil properties, plant community composition, and herbivory all have been reported as important factors influencing the composition of soil communities. However, most studies thus far have considered these factors in isolation, whereas they strongly interact in the field. Here, we study how grazing by vertebrate herbivores influences the soil nematode community composition of a floodplain grassland while we account for effects of grazing on plant community composition and abiotic soil properties. Nematodes are the most ubiquitous invertebrates in the soil. They include a variety of feeding types, ranging from microbial feeders to herbivores and carnivores, and they perform key functions in soil food webs. Our hypothesis was that grazing affects nematode community structure and composition through altering plant community structure and composition. Alternatively, we tested whether the effects of grazing may, directly or indirectly, run via changes in soil abiotic properties. We used a long-term field experiment containing plots with and without vertebrate grazers (cattle and rabbits). We compared plant and nematode community structure and composition, as well as a number of key soil abiotic properties, and we applied structural equation modeling to investigate four possible pathways by which grazing may change nematode community composition. Aboveground grazing increased plant species richness and reduced both plant and nematode community heterogeneity. There was a positive relationship between plant and nematode diversity indices. Grazing decreased the number of bacterial-feeding nematodes, indicating that in these grasslands, top-down control of plant production by grazing leads to bottom-up control in the basal part of the bacterial channel of the soil food web. According to the structural equation model, grazing had a strong effect on soil abiotic properties and plant community composition, whereas plant community composition was the main determinant of

  7. Multispectral scanner imagery for plant community classification.

    NASA Technical Reports Server (NTRS)

    Driscoll, R. S.; Spencer, M. M.

    1973-01-01

    Optimum channel selection among 12 channels of multispectral scanner imagery identified six as providing the best information for computerized classification of 11 plant communities and two nonvegetation classes. Intensive preprocessing of the spectral data was required to eliminate bidirectional reflectance effects of the spectral imagery caused by scanner view angle and varying geometry of the plant canopy. Generalized plant community types - forest, grassland, and hydrophytic systems - were acceptably classified based on ecological analysis. Serious, but soluble, errors occurred with attempts to classify specific community types within the grassland system. However, special clustering analyses provided for improved classification of specific grassland communities.

  8. Host plant species determines symbiotic bacterial community mediating suppression of plant defenses.

    PubMed

    Chung, Seung Ho; Scully, Erin D; Peiffer, Michelle; Geib, Scott M; Rosa, Cristina; Hoover, Kelli; Felton, Gary W

    2017-01-03

    Herbivore associated bacteria are vital mediators of plant and insect interactions. Host plants play an important role in shaping the gut bacterial community of insects. Colorado potato beetles (CPB; Leptinotarsa decemlineata) use several Solanum plants as hosts in their natural environment. We previously showed that symbiotic gut bacteria from CPB larvae suppressed jasmonate (JA)-induced defenses in tomato. However, little is known about how changes in the bacterial community may be involved in the manipulation of induced defenses in wild and cultivated Solanum plants of CPB. Here, we examined suppression of JA-mediated defense in wild and cultivated hosts of CPB by chemical elicitors and their symbiotic bacteria. Furthermore, we investigated associations between the gut bacterial community and suppression of plant defenses using 16 S rRNA amplicon sequencing. Symbiotic bacteria decreased plant defenses in all Solanum hosts and there were different gut bacterial communities in CPB fed on different host plants. When larvae were reared on different hosts, defense suppression differed among host plants. These results demonstrate that host plants influence herbivore gut bacterial communities and consequently affect the herbivore's ability to manipulate JA-mediated plant defenses. Thus, the presence of symbiotic bacteria that suppress plant defenses might help CPB adapt to host plants.

  9. Host plant species determines symbiotic bacterial community mediating suppression of plant defenses

    PubMed Central

    Chung, Seung Ho; Scully, Erin D.; Peiffer, Michelle; Geib, Scott M.; Rosa, Cristina; Hoover, Kelli; Felton, Gary W.

    2017-01-01

    Herbivore associated bacteria are vital mediators of plant and insect interactions. Host plants play an important role in shaping the gut bacterial community of insects. Colorado potato beetles (CPB; Leptinotarsa decemlineata) use several Solanum plants as hosts in their natural environment. We previously showed that symbiotic gut bacteria from CPB larvae suppressed jasmonate (JA)-induced defenses in tomato. However, little is known about how changes in the bacterial community may be involved in the manipulation of induced defenses in wild and cultivated Solanum plants of CPB. Here, we examined suppression of JA-mediated defense in wild and cultivated hosts of CPB by chemical elicitors and their symbiotic bacteria. Furthermore, we investigated associations between the gut bacterial community and suppression of plant defenses using 16 S rRNA amplicon sequencing. Symbiotic bacteria decreased plant defenses in all Solanum hosts and there were different gut bacterial communities in CPB fed on different host plants. When larvae were reared on different hosts, defense suppression differed among host plants. These results demonstrate that host plants influence herbivore gut bacterial communities and consequently affect the herbivore’s ability to manipulate JA-mediated plant defenses. Thus, the presence of symbiotic bacteria that suppress plant defenses might help CPB adapt to host plants. PMID:28045052

  10. A 2-Year Field Study Shows Little Evidence That the Long-Term Planting of Transgenic Insect-Resistant Cotton Affects the Community Structure of Soil Nematodes

    PubMed Central

    Li, Xiaogang; Liu, Biao

    2013-01-01

    Transgenic insect-resistant cotton has been released into the environment for more than a decade in China to effectively control the cotton bollworm (Helicoverpa armigera) and other Lepidoptera. Because of concerns about undesirable ecological side-effects of transgenic crops, it is important to monitor the potential environmental impact of transgenic insect-resistant cotton after commercial release. Our 2-year study included 1 cotton field where non-transgenic cotton had been planted continuously and 2 other cotton fields where transgenic insect-resistant cotton had been planted for different lengths of time since 1997 and since 2002. In 2 consecutive years (2009 and 2010), we took soil samples from 3 cotton fields at 4 different growth stages (seedling, budding, boll-forming and boll-opening stages), collected soil nematodes from soil with the sugar flotation and centrifugation method and identified the soil nematodes to the genus level. The generic composition, individual densities and diversity indices of the soil nematodes did not differ significantly between the 2 transgenic cotton fields and the non-transgenic cotton field, but significant seasonal variation was found in the individual densities of the principal trophic groups and in the diversity indices of the nematodes in all 3 cotton fields. The study used a comparative perspective to monitor the impact of transgenic insect-resistant cotton grown in typical ‘real world’ conditions. The results of the study suggested that more than 10 years of cultivation of transgenic insect-resistant cotton had no significant effects–adverse or otherwise–on soil nematodes. This study provides a theoretical basis for ongoing environmental impact monitoring of transgenic plants. PMID:23613899

  11. Blackfeet Community Water Treatment Plant NPDES Permit

    EPA Pesticide Factsheets

    Under NPDES permit MT-0030643, the Blackfeet Tribe is authorized to discharge from its Blackfoot Community Water Treatment Plant in Glacier County, Montana, to an unnamed intermittent stream which flows to Two Medicine River.

  12. Revisiting methanotrophic communities in sewage treatment plants.

    PubMed

    Ho, Adrian; Vlaeminck, Siegfried E; Ettwig, Katharina F; Schneider, Bellinda; Frenzel, Peter; Boon, Nico

    2013-04-01

    The methanotrophic potential in sewage treatment sludge was investigated. We detected a diverse aerobic methanotrophic community that potentially plays a significant role in mitigating methane emission in this environment. The results suggest that community structure was determined by conditions specific to the processes in a sewage treatment plant.

  13. Soil and plant effects on microbial community structure.

    PubMed

    Buyer, Jeffrey S; Roberts, Daniel P; Russek-Cohen, Estelle

    2002-11-01

    We investigated the effects of two different plant species (corn and soybean) and three different soil types on microbial community structure in the rhizosphere. Our working hypothesis was that the rhizosphere effect would be strongest on fast-growing aerobic heterotrophs, while there would be little or no rhizosphere effect on oligotrophic and other slow-growing microorganisms. Culturable bacteria and fungi had larger population densities in the rhizosphere than in bulk soil. Communities were characterized by soil fatty acid analysis and by substrate utilization assays for bacteria and fungi. Fatty acid analysis revealed a very strong soil effect but little plant effect on the microbial community, indicating that the overall microbial community structure was not affected by the rhizosphere. There was a strong rhizosphere effect detected by the substrate utilization assay for fast-growing aerobic heterotrophic bacterial community structure, with soil controls and rhizosphere samples clearly distinguished from each other. There was a much weaker rhizosphere effect on fungal communities than on bacterial communities as measured by the substrate utilization assays. At this coarse level of community analysis, the rhizosphere microbial community was impacted most by soil effects, and the rhizosphere only affected a small portion of the total bacteria.

  14. The soil microbial community composition and soil microbial carbon uptake are more affected by soil type than by different vegetation types (C3 and C4 plants) and seasonal changes

    NASA Astrophysics Data System (ADS)

    Griselle Mellado Vazquez, Perla; Lange, Markus; Gleixner, Gerd

    2016-04-01

    This study investigates the influence of different vegetation types (C3 and C4 plants), soil type and seasonal changes on the soil microbial biomass, soil microbial community composition and soil microbial carbon (C) uptake. We collected soil samples in winter (non-growing season) and summer (growing season) in 2012 from an experimental site cropping C3 and C4 plants for 6 years on two different soil types (sandy and clayey). The amount of phospholipid fatty acids (PLFAs) and their compound-specific δ13C values were used to determined microbial biomass and the flow of C from plants to soil microorganisms, respectively. Higher microbial biomass was found in the growing season. The microbial community composition was mainly explained by soil type. Higher amounts of SOC were driving the predominance of G+ bacteria, actinobacteria and cyclic G- bacteria in sandy soils, whereas root biomass was significantly related to the increased proportions of G- bacteria in clayey soils. Plant-derived C in G- bacteria increased significantly in clayey soils in the growing season. This increase was positively and significantly driven by root biomass. Moreover, changes in plant-derived C among microbial groups pointed to specific capabilities of different microbial groups to decompose distinct sources of C. We concluded that soil texture and favorable growth conditions driven by rhizosphere interactions are the most important factors controlling the soil microbial community. Our results demonstrate that a change of C3 plants vs. C4 plants has only a minor effect on the soil microbial community. Thus, such experiments are well suited to investigate soil organic matter dynamics as they allow to trace the C flow from plants into the soil microbial community without changing the community abundance and composition.

  15. Contrasting Effects of Different Mammalian Herbivores on Sagebrush Plant Communities

    PubMed Central

    Veblen, Kari E.; Nehring, Kyle C.; McGlone, Christopher M.; Ritchie, Mark E.

    2015-01-01

    Herbivory by both grazing and browsing ungulates shapes the structure and functioning of terrestrial ecosystems worldwide, and both types of herbivory have been implicated in major ecosystem state changes. Despite the ecological consequences of differences in diets and feeding habits among herbivores, studies that experimentally distinguish effects of grazing from spatially co-occurring, but temporally segregated browsing are extremely rare. Here we use a set of long-term exclosures in northern Utah, USA, to determine how domestic grazers vs. wild ungulate herbivores (including browsers and mixed feeders) affect sagebrush-dominated plant communities that historically covered ~62 million ha in North America. We sampled plant community properties and found that after 22 years grazing and browsing elicited perceptible changes in overall plant community composition and distinct responses by individual plant species. In the woody layer of the plant community, release from winter and spring wild ungulate herbivory increased densities of larger Wyoming big sagebrush (Artemisia tridentata, ssp. wyomingensis) at the expense of small sagebrush, while disturbance associated with either cattle or wild ungulate activity alone was sufficient to increase bare ground and reduce cover of biological soil crusts. The perennial bunchgrass, bottlebrush squirretail (Elymus elymoides), responded positively to release from summer cattle grazing, and in turn appeared to competitively suppress another more grazing tolerant perennial grass, Sandberg’s blue grass (Poa secunda). Grazing by domestic cattle also was associated with increased non-native species biomass. Together, these results illustrate that ungulate herbivory has not caused sagebrush plant communities to undergo dramatic state shifts; however clear, herbivore-driven shifts are evident. In a dry, perennial-dominated system where plant community changes can occur very slowly, our results provide insights into potential long

  16. Contrasting effects of different mammalian herbivores on sagebrush plant communities.

    PubMed

    Veblen, Kari E; Nehring, Kyle C; McGlone, Christopher M; Ritchie, Mark E

    2015-01-01

    Herbivory by both grazing and browsing ungulates shapes the structure and functioning of terrestrial ecosystems worldwide, and both types of herbivory have been implicated in major ecosystem state changes. Despite the ecological consequences of differences in diets and feeding habits among herbivores, studies that experimentally distinguish effects of grazing from spatially co-occurring, but temporally segregated browsing are extremely rare. Here we use a set of long-term exclosures in northern Utah, USA, to determine how domestic grazers vs. wild ungulate herbivores (including browsers and mixed feeders) affect sagebrush-dominated plant communities that historically covered ~62 million ha in North America. We sampled plant community properties and found that after 22 years grazing and browsing elicited perceptible changes in overall plant community composition and distinct responses by individual plant species. In the woody layer of the plant community, release from winter and spring wild ungulate herbivory increased densities of larger Wyoming big sagebrush (Artemisia tridentata, ssp. wyomingensis) at the expense of small sagebrush, while disturbance associated with either cattle or wild ungulate activity alone was sufficient to increase bare ground and reduce cover of biological soil crusts. The perennial bunchgrass, bottlebrush squirretail (Elymus elymoides), responded positively to release from summer cattle grazing, and in turn appeared to competitively suppress another more grazing tolerant perennial grass, Sandberg's blue grass (Poa secunda). Grazing by domestic cattle also was associated with increased non-native species biomass. Together, these results illustrate that ungulate herbivory has not caused sagebrush plant communities to undergo dramatic state shifts; however clear, herbivore-driven shifts are evident. In a dry, perennial-dominated system where plant community changes can occur very slowly, our results provide insights into potential long

  17. Functional identity versus species richness: herbivory resistance in plant communities

    PubMed Central

    Heimann, Juliane; Köhler, Günter; Mitschunas, Nadine; Weisser, Wolfgang W.

    2010-01-01

    The resistance of a plant community against herbivore attack may depend on plant species richness, with monocultures often much more severely affected than mixtures of plant species. Here, we used a plant–herbivore system to study the effects of selective herbivory on consumption resistance and recovery after herbivory in 81 experimental grassland plots. Communities were established from seed in 2002 and contained 1, 2, 4, 8, 16 or 60 plant species of 1, 2, 3 or 4 functional groups. In 2004, pairs of enclosure cages (1 m tall, 0.5 m diameter) were set up on all 81 plots. One randomly selected cage of each pair was stocked with 10 male and 10 female nymphs of the meadow grasshopper, Chorthippus parallelus. The grasshoppers fed for 2 months, and the vegetation was monitored over 1 year. Consumption resistance and recovery of vegetation were calculated as proportional changes in vegetation biomass. Overall, grasshopper herbivory averaged 6.8%. Herbivory resistance and recovery were influenced by plant functional group identity, but independent of plant species richness and number of functional groups. However, herbivory induced shifts in vegetation composition that depended on plant species richness. Grasshopper herbivory led to increases in herb cover at the expense of grasses. Herb cover increased more strongly in species-rich mixtures. We conclude that selective herbivory changes the functional composition of plant communities and that compositional changes due to selective herbivory depend on plant species richness. PMID:20429014

  18. Microbial population and community dynamics on plant roots and their feedbacks on plant communities.

    PubMed

    Bever, James D; Platt, Thomas G; Morton, Elise R

    2012-01-01

    The composition of the soil microbial community can be altered dramatically due to association with individual plant species, and these effects on the microbial community can have important feedbacks on plant ecology. Negative plant-soil feedback plays primary roles in maintaining plant community diversity, whereas positive plant-soil feedback may cause community conversion. Host-specific differentiation of the microbial community results from the trade-offs associated with overcoming plant defense and the specific benefits associated with plant rewards. Accumulation of host-specific pathogens likely generates negative feedback on the plant, while changes in the density of microbial mutualists likely generate positive feedback. However, the competitive dynamics among microbes depends on the multidimensional costs of virulence and mutualism, the fine-scale spatial structure within plant roots, and active plant allocation and localized defense. Because of this, incorporating a full view of microbial dynamics is essential to explaining the dynamics of plant-soil feedbacks and therefore plant community ecology.

  19. Corridors affect plants, animals, and their interactions in fragmented landscapes.

    SciTech Connect

    Tewksbury, Joshua, J.; Levey, Douglas, J.; Haddad, Nick, M.; Sargent, Sarah; Orrock, John, L.; Weldon, Aimee; Danielson, Brent, J.; Brinkerhoff, Jory; Damschen, Ellen, I.; Townsend, Patricia

    2002-10-01

    Tewksbury, J.J., D.J. Levey, N.M. Haddad, S. Sargent, J.L. Orrock, A. Weldon, B.J. Danielson, J. Brinkerhoff, E.I. Damschen, and P. Townsend. 2002. Corridors affect plants, animals, and their interactions in fragmented landscapes. PNAS 99(20):12923-12926. Among the most popular strategies for maintaining populations of both plants and animals in fragmented landscapes is to connect isolated patches with thin strips of habitat, called corridors. Corridors are thought to increase the exchange of individuals between habitat patches, promoting genetic exchange and reducing population fluctuations. Empirical studies addressing the effects of corridors have either been small in scale or have ignored confounding effects of increased habitat area created by the presence of a corridor. These methodological difficulties, coupled with a paucity of studies examining the effects of corridors on plants and plant-animal interactions, have sparked debate over the purported value of corridors in conservation planning. We report results of a large-scale experiment that directly address this debate. We demonstrate that corridors not only increase the exchange of animals between patches, but also facilitate two key plant-animal interactions: pollination and seed dispersal. Our results show that the beneficial effects of corridors extend beyond the area they add, and suggest that increased plant and animal movement through corridors will have positive impacts on plant populations and community interactions in fragmented landscapes.

  20. Do alterations in mesofauna community affect earthworms?

    PubMed

    Uvarov, Alexei V; Karaban, Kamil

    2015-11-01

    Interactions between the saprotrophic animal groups that strongly control soil microbial activities and the functioning of detrital food webs, such as earthworms and mesofauna, are not well understood. Earthworm trophic and engineering activities strongly affect mesofauna abundance and diversity through various direct and indirect pathways. In contrast, mesofauna effects on earthworm populations are less evident; however, their importance may be high, considering the keystone significance of earthworms for the functioning of the soil system. We studied effects of a diverse mesofauna community of a deciduous forest on two earthworm species representing epigeic (Lumbricus rubellus) and endogeic (Aporrectodea caliginosa) ecological groups. In microcosms, the density of total mesofauna or its separate groups (enchytraeids, collembolans, gamasid mites) was manipulated (increased) and responses of earthworms and soil systems were recorded. A rise in mesofauna density resulted in a decrease of biomass and an increased mortality in L. rubellus, presumably due to competition with mesofauna for litter resources. In contrast, similar mesofauna manipulations promoted reproduction of A. caliginosa, suggesting a facilitated exploitation of litter resources due to increased mesofauna activities. Changes of microcosm respiration rates, litter organic matter content and microbial activities across the manipulation treatments indicate that mesofauna modify responses of soil systems in the presence of earthworms. However, similar mesofauna manipulations could induce different responses in soil systems with either epigeic or endogeic lumbricids, which suggests that earthworm/mesofauna interactions are species-specific. Thus, mesofauna impacts should be treated as a factor affecting the engineering activities of epigeic and endogeic earthworms in the soil.

  1. Bacterial symbionts in insects or the story of communities affecting communities.

    PubMed

    Ferrari, Julia; Vavre, Fabrice

    2011-05-12

    Bacterial symbionts are widespread in insects and other animals. Most of them are predominantly vertically transmitted, along with their hosts' genes, and thus extend the heritable genetic variation present in one species. These passengers have a variety of repercussions on the host's phenotypes: besides the cost imposed on the host for maintaining the symbiont population, they can provide fitness advantages to the host or manipulate the host's reproduction. We argue that insect symbioses are ideal model systems for community genetics. First, bacterial symbionts directly or indirectly affect the interactions with other species within a community. Examples include their involvement in modifying the use of host plants by phytophagous insects, in providing resistance to natural enemies, but also in reducing the global genetic diversity or gene flow between populations within some species. Second, one emerging picture in insect symbioses is that many species are simultaneously infected with more than one symbiont, which permits studying the factors that shape bacterial communities; for example, horizontal transmission, interactions between host genotype, symbiont genotype and the environment and interactions among symbionts. One conclusion is that insects' symbiotic complements are dynamic communities that affect and are affected by the communities in which they are embedded.

  2. Plant community succession in modern Yellow River Delta, China*

    PubMed Central

    Zhang, Gao-sheng; Wang, Ren-qing; Song, Bai-min

    2007-01-01

    Data were collected in different successional stages using a simultaneous sampling method and analyzed through quantitative classification method. Three large groups and 12 classes were made to represent the community patterns of three succession stages and 12 succession communities. The succession series of plant community in the study area was as follows: saline bare land→community Suaeda salsa→community Tamarix chinensis→grassland. Succession degree and succession process of 12 succession communities were calculated. Most of these communities were in the lower succession stage, however, community Phragmites communis+Glycine soja and community Imperata cylindrica+G. soja were close to the succession stage of grassland climax. Five species diversity indices were used to study the changes in species richness, species evenness and diversity during succession of community. Heterogeneity index and richness index increased gradually during the community succession process, but species evenness tended to decrease with succession development. The relation between succession and environment was studied by ordination technique, and the results showed that the soil salt content was an important factor to halarch succession of the modern Yellow River Delta. It affected community structure, species composition and succession process. PMID:17657854

  3. Diversity protects plant communities against generalist molluscan herbivores

    PubMed Central

    Fabian, Yvonne; Sandau, Nadine; Bruggisser, Odile T; Kehrli, Patrik; Aebi, Alexandre; Rohr, Rudolf P; Naisbit, Russell E; Bersier, Louis-Félix

    2012-01-01

    Wildflower strips are used to increase natural enemies of crop pests and to conserve insect diversity on farmland. Mollusks, especially slugs, can affect the vegetation development in these strips considerably. Although recent theoretical work suggests that more diverse plant communities will exhibit greater resistance against herbivore pressure, empirical studies are scarce. We conducted a semi-natural experiment in wildflower strips, manipulating trophic structure (reduction in herbivorous mollusks and reduction in major predators) and plant diversity (2, 6, 12, 20 and 24 sown species). This design allowed us to assess the effect of plant diversity, biomass and composition on mollusks, and vice versa, the effect of mollusc abundance on vegetation. Seven species of mollusks were found in the strips, with the slugs Arion lusitanicus, Deroceras reticulatum and Deroceras panormitanum being most frequent. We found a negative relationship between plant diversity and mollusk abundance, which was due predominantly to a decrease in the agricultural pest species A. lusitanicus. These results are consistent with the hypothesis that plant diversity can reduce the impact of herbivores. However, plant identity also had an effect on mollusks, and accounted for a much larger fraction of the variation in mollusk communities than biodiversity effects. While overall plant diversity decreased during the 3 years of the study, in the final year the highest plant diversity was found in the plots where mollusk populations were experimentally reduced. We conclude that selective feeding by generalist herbivores leads to changes in plant community composition and hence reduced plant diversity. Our results highlight the importance of plant biodiversity as protection against generalist herbivores, which if abundant can in the long term negatively impact plant diversity, driving the system along a “low plant diversity – high mollusk abundance” trajectory. PMID:23145332

  4. Global change and terrestrial plant community dynamics

    PubMed Central

    Franklin, Janet; Serra-Diaz, Josep M.; Syphard, Alexandra D.; Regan, Helen M.

    2016-01-01

    Anthropogenic drivers of global change include rising atmospheric concentrations of carbon dioxide and other greenhouse gasses and resulting changes in the climate, as well as nitrogen deposition, biotic invasions, altered disturbance regimes, and land-use change. Predicting the effects of global change on terrestrial plant communities is crucial because of the ecosystem services vegetation provides, from climate regulation to forest products. In this paper, we present a framework for detecting vegetation changes and attributing them to global change drivers that incorporates multiple lines of evidence from spatially extensive monitoring networks, distributed experiments, remotely sensed data, and historical records. Based on a literature review, we summarize observed changes and then describe modeling tools that can forecast the impacts of multiple drivers on plant communities in an era of rapid change. Observed responses to changes in temperature, water, nutrients, land use, and disturbance show strong sensitivity of ecosystem productivity and plant population dynamics to water balance and long-lasting effects of disturbance on plant community dynamics. Persistent effects of land-use change and human-altered fire regimes on vegetation can overshadow or interact with climate change impacts. Models forecasting plant community responses to global change incorporate shifting ecological niches, population dynamics, species interactions, spatially explicit disturbance, ecosystem processes, and plant functional responses. Monitoring, experiments, and models evaluating multiple change drivers are needed to detect and predict vegetation changes in response to 21st century global change. PMID:26929338

  5. Global change and terrestrial plant community dynamics.

    PubMed

    Franklin, Janet; Serra-Diaz, Josep M; Syphard, Alexandra D; Regan, Helen M

    2016-04-05

    Anthropogenic drivers of global change include rising atmospheric concentrations of carbon dioxide and other greenhouse gasses and resulting changes in the climate, as well as nitrogen deposition, biotic invasions, altered disturbance regimes, and land-use change. Predicting the effects of global change on terrestrial plant communities is crucial because of the ecosystem services vegetation provides, from climate regulation to forest products. In this paper, we present a framework for detecting vegetation changes and attributing them to global change drivers that incorporates multiple lines of evidence from spatially extensive monitoring networks, distributed experiments, remotely sensed data, and historical records. Based on a literature review, we summarize observed changes and then describe modeling tools that can forecast the impacts of multiple drivers on plant communities in an era of rapid change. Observed responses to changes in temperature, water, nutrients, land use, and disturbance show strong sensitivity of ecosystem productivity and plant population dynamics to water balance and long-lasting effects of disturbance on plant community dynamics. Persistent effects of land-use change and human-altered fire regimes on vegetation can overshadow or interact with climate change impacts. Models forecasting plant community responses to global change incorporate shifting ecological niches, population dynamics, species interactions, spatially explicit disturbance, ecosystem processes, and plant functional responses. Monitoring, experiments, and models evaluating multiple change drivers are needed to detect and predict vegetation changes in response to 21st century global change.

  6. Intraspecific genetic variation and species coexistence in plant communities

    PubMed Central

    Ehlers, Bodil K.; Damgaard, Christian F.; Laroche, Fabien

    2016-01-01

    Many studies report that intraspecific genetic variation in plants can affect community composition and coexistence. However, less is known about which traits are responsible and the mechanisms by which variation in these traits affect the associated community. Focusing on plant–plant interactions, we review empirical studies exemplifying how intraspecific genetic variation in functional traits impacts plant coexistence. Intraspecific variation in chemical and architectural traits promotes species coexistence, by both increasing habitat heterogeneity and altering competitive hierarchies. Decomposing species interactions into interactions between genotypes shows that genotype × genotype interactions are often intransitive. The outcome of plant–plant interactions varies with local adaptation to the environment and with dominant neighbour genotypes, and some plants can recognize the genetic identity of neighbour plants if they have a common history of coexistence. Taken together, this reveals a very dynamic nature of coexistence. We outline how more traits mediating plant–plant interactions may be identified, and how future studies could use population genetic surveys of genotype distribution in nature and methods from trait-based ecology to better quantify the impact of intraspecific genetic variation on plant coexistence. PMID:26790707

  7. Interactive effects of mycorrhizae and a root hemiparasite on plant community productivity and diversity.

    PubMed

    Stein, Claudia; Rissmann, Cornelia; Hempel, Stefan; Renker, Carsten; Buscot, François; Prati, Daniel; Auge, Harald

    2009-02-01

    Plant communities can be affected both by arbuscular mycorrhizal fungi (AMF) and hemiparasitic plants. However, little is known about the interactive effects of these two biotic factors on the productivity and diversity of plant communities. To address this question, we set up a greenhouse study in which different AMF inocula and a hemiparasitic plant (Rhinanthus minor) were added to experimental grassland communities in a fully factorial design. In addition, single plants of each species in the grassland community were grown with the same treatments to distinguish direct AMF effects from indirect effects via plant competition. We found that AMF changed plant community structure by influencing the plant species differently. At the community level, AMF decreased the productivity by 15-24%, depending on the particular AMF treatment, mainly because two dominant species, Holcus lanatus and Plantago lanceolata, showed a negative mycorrhizal dependency. Concomitantly, plant diversity increased due to AMF inoculation and was highest in the treatment with a combination of two commercial AM strains. AMF had a positive effect on growth of the hemiparasite, and thereby induced a negative impact of the hemiparasite on host plant biomass which was not found in non-inoculated communities. However, the hemiparasite did not increase plant diversity. Our results highlight the importance of interactions with soil microbes for plant community structure and that these indirect effects can vary among AMF treatments. We conclude that mutualistic interactions with AMF, but not antagonistic interactions with a root hemiparasite, promote plant diversity in this grassland community.

  8. Impacts of climate change drivers on C4 grassland productivity: Scaling driver effects through the plant community

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Climate change drivers affect the plant community productivity via three pathways: 1) direct effects of drivers on plants, 2) the response of species abundances to drivers (community response), and 3) the feedback effect of community change on productivity (community effect). The contribution of e...

  9. Plant-plant interactions, environmental gradients and plant diversity: a global synthesis of community-level studies

    PubMed Central

    Soliveres, Santiago; Maestre, Fernando T.

    2015-01-01

    Previous syntheses on the effects of environmental conditions on the outcome of plant-plant interactions summarize results from pairwise studies. However, the upscaling to the community-level of such studies is problematic because of the existence of multiple species assemblages and species-specific responses to both the environmental conditions and the presence of neighbors. We conducted the first global synthesis of community-level studies from harsh environments, which included data from 71 alpine and 137 dryland communities. Here we: i) test how important are facilitative interactions as a driver of community structure, ii) evaluate whether the frequency of positive plant-plant interactions across differing environmental conditions and habitats is predictable, and iii) assess whether thresholds in the response of plant-plant interactions to environmental gradients exists between “moderate” and “extreme” stress levels. We also used those community-level studies performed across gradients of at least three points to evaluate how the average environmental conditions, the length of the gradient studied, and the number of points sampled across such gradient affect the form and strength of the facilitation-environment relationship. Over 25% of the species present were more spatially associated to nurse plants than expected by chance in both alpine and dryland areas, illustrating the high importance of positive plant-plant interactions for the maintenance of plant diversity. Facilitative interactions were more frequent, and more related to environmental conditions, in alpine than in dryland areas, perhaps because drylands are generally characterized by a larger variety of environmental stress factors and plant functional traits. The frequency of facilitative interactions in alpine communities peaked at 1000 mm of annual rainfall, and globally decreased with elevation. The frequency of positive interactions in dryland communities decreased globally with water

  10. Biotic and abiotic properties mediating plant diversity effects on soil microbial communities in an experimental grassland.

    PubMed

    Lange, Markus; Habekost, Maike; Eisenhauer, Nico; Roscher, Christiane; Bessler, Holger; Engels, Christof; Oelmann, Yvonne; Scheu, Stefan; Wilcke, Wolfgang; Schulze, Ernst-Detlef; Gleixner, Gerd

    2014-01-01

    Plant diversity drives changes in the soil microbial community which may result in alterations in ecosystem functions. However, the governing factors between the composition of soil microbial communities and plant diversity are not well understood. We investigated the impact of plant diversity (plant species richness and functional group richness) and plant functional group identity on soil microbial biomass and soil microbial community structure in experimental grassland ecosystems. Total microbial biomass and community structure were determined by phospholipid fatty acid (PLFA) analysis. The diversity gradient covered 1, 2, 4, 8, 16 and 60 plant species and 1, 2, 3 and 4 plant functional groups (grasses, legumes, small herbs and tall herbs). In May 2007, soil samples were taken from experimental plots and from nearby fields and meadows. Beside soil texture, plant species richness was the main driver of soil microbial biomass. Structural equation modeling revealed that the positive plant diversity effect was mainly mediated by higher leaf area index resulting in higher soil moisture in the top soil layer. The fungal-to-bacterial biomass ratio was positively affected by plant functional group richness and negatively by the presence of legumes. Bacteria were more closely related to abiotic differences caused by plant diversity, while fungi were more affected by plant-derived organic matter inputs. We found diverse plant communities promoted faster transition of soil microbial communities typical for arable land towards grassland communities. Although some mechanisms underlying the plant diversity effect on soil microorganisms could be identified, future studies have to determine plant traits shaping soil microbial community structure. We suspect differences in root traits among different plant communities, such as root turnover rates and chemical composition of root exudates, to structure soil microbial communities.

  11. Biotic and Abiotic Properties Mediating Plant Diversity Effects on Soil Microbial Communities in an Experimental Grassland

    PubMed Central

    Lange, Markus; Habekost, Maike; Eisenhauer, Nico; Roscher, Christiane; Bessler, Holger; Engels, Christof; Oelmann, Yvonne; Scheu, Stefan; Wilcke, Wolfgang; Schulze, Ernst-Detlef; Gleixner, Gerd

    2014-01-01

    Plant diversity drives changes in the soil microbial community which may result in alterations in ecosystem functions. However, the governing factors between the composition of soil microbial communities and plant diversity are not well understood. We investigated the impact of plant diversity (plant species richness and functional group richness) and plant functional group identity on soil microbial biomass and soil microbial community structure in experimental grassland ecosystems. Total microbial biomass and community structure were determined by phospholipid fatty acid (PLFA) analysis. The diversity gradient covered 1, 2, 4, 8, 16 and 60 plant species and 1, 2, 3 and 4 plant functional groups (grasses, legumes, small herbs and tall herbs). In May 2007, soil samples were taken from experimental plots and from nearby fields and meadows. Beside soil texture, plant species richness was the main driver of soil microbial biomass. Structural equation modeling revealed that the positive plant diversity effect was mainly mediated by higher leaf area index resulting in higher soil moisture in the top soil layer. The fungal-to-bacterial biomass ratio was positively affected by plant functional group richness and negatively by the presence of legumes. Bacteria were more closely related to abiotic differences caused by plant diversity, while fungi were more affected by plant-derived organic matter inputs. We found diverse plant communities promoted faster transition of soil microbial communities typical for arable land towards grassland communities. Although some mechanisms underlying the plant diversity effect on soil microorganisms could be identified, future studies have to determine plant traits shaping soil microbial community structure. We suspect differences in root traits among different plant communities, such as root turnover rates and chemical composition of root exudates, to structure soil microbial communities. PMID:24816860

  12. Designing Invasion Resistant Plant Communities: The Role of Plant Functional Traits

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Establishing and maintaining weed-resistant plant communities is a central goal of sustainable invasive plant management programs. Plant community characteristics that improve invasion resistance, however, are poorly understood. Here we synthesize data from multiple studies and show traits related ...

  13. Curvilinear Effects of Invasive Plants on Plant Diversity: Plant Community Invaded by Sphagneticola trilobata

    PubMed Central

    Zhai, De-Li; Chen, Si-Chong; Si, Chun-Can; Huang, Ping; Wang, Rui-Ping; Zhong, Qiong-Xin; Du, Dao-Lin

    2014-01-01

    The effects of invasive plants on the species diversity of plant communities are controversial, showing either a positive or negative linear relationship. Based on community data collected from forty 5 m×5 m plots invaded by Sphagneticola trilobata in eight cities across Hainan Island, China, we found S. trilobata decreased plant community diversity once its cover was beyond 10%. We demonstrated that the effects of invasive/native plants on the plant diversity of communities invaded by S. trilobata were curvilinear. These effects, which showed peaks under different degrees of vegetation cover, appeared not only for S. trilobata and all invasive plants, but also for all native plants. Invasive plants primarily had negative effects on plant diversity when they became abundant at a much lower cover level (less than 35%), compared with the native plants (over 60%). Thus, it is necessary to distinguish a range for assessing the effects of plants, especially invasive plants. Our results also confirmed that the invasion intensity of invasive alien plants increased with the intensity of local economic development. We highlight and further discuss the critical importance of curvilinear effects of biological invasion to provide ideas regarding the conservation of local biodiversity and the management of invasive plants. PMID:25426856

  14. Curvilinear effects of invasive plants on plant diversity: plant community invaded by Sphagneticola trilobata.

    PubMed

    Qi, Shan-Shan; Dai, Zhi-Cong; Zhai, De-Li; Chen, Si-Chong; Si, Chun-Can; Huang, Ping; Wang, Rui-Ping; Zhong, Qiong-Xin; Du, Dao-Lin

    2014-01-01

    The effects of invasive plants on the species diversity of plant communities are controversial, showing either a positive or negative linear relationship. Based on community data collected from forty 5 m×5 m plots invaded by Sphagneticola trilobata in eight cities across Hainan Island, China, we found S. trilobata decreased plant community diversity once its cover was beyond 10%. We demonstrated that the effects of invasive/native plants on the plant diversity of communities invaded by S. trilobata were curvilinear. These effects, which showed peaks under different degrees of vegetation cover, appeared not only for S. trilobata and all invasive plants, but also for all native plants. Invasive plants primarily had negative effects on plant diversity when they became abundant at a much lower cover level (less than 35%), compared with the native plants (over 60%). Thus, it is necessary to distinguish a range for assessing the effects of plants, especially invasive plants. Our results also confirmed that the invasion intensity of invasive alien plants increased with the intensity of local economic development. We highlight and further discuss the critical importance of curvilinear effects of biological invasion to provide ideas regarding the conservation of local biodiversity and the management of invasive plants.

  15. Multiple climate drivers accelerate Arctic plant community senescence

    NASA Astrophysics Data System (ADS)

    Livensperger, C.; Steltzer, H.; Wallenstein, M. D.; Weintraub, M. N.

    2015-12-01

    Alteration of seasonal phenology cues due to climate change has led to changes in the onset and duration of the growing season. While photoperiod often acts as an ultimate control on phenological events, recent studies have shown that environmental cues such as temperature and soil water content can modify the direction and rate of senescence processes. Warmer temperatures have resulted in an observed trend towards delayed senescence across temperate latitudes. However, Arctic regions are characterized by extreme seasonality and rapidly decreasing photoperiod, and consequently senescence may not shift as climate warms. We monitored the timing of Arctic plant community senescence for three years under the framework of an experimental manipulation that altered seasonal phenological cues through warming and earlier snowmelt. Alternative models of senescence were tested to determine if microclimate (air temperature, soil temperature, and soil moisture) or start of season phenology affect the timing and rate of community senescence. We found that all three microclimate predictors contributed to explaining variation in timing of senescence, suggesting that photoperiod is not the sole control on timing of senescence in Arctic plant communities. Rather, increased air and soil temperatures along with drier soil conditions, led to acceleration in the onset of senescence at a community level. Our data suggest that (1) multiple climate drivers predict timing of plant community senescence, and (2) climate change could result in a shorter peak season due to earlier onset of senescence, which would decrease the potential carbon uptake in moist acidic tundra.

  16. Values Undergirding Policies Affecting Community Colleges.

    ERIC Educational Resources Information Center

    Townsend, Barbara K.

    2001-01-01

    Uses the examples of remedial education, K-16 initiatives, and workforce preparation to illustrate how these values influence higher education policy at community colleges. Policymakers should recognize that these values may conflict, therefore leading to controversy. States that cultural/social values dominating the development of educational…

  17. Ohmic resistance affects microbial community and ...

    EPA Pesticide Factsheets

    Multi-anode microbial electrochemical cells (MXCs) are considered as one of the most promising configurations for scale-up of MXCs, but fundamental understanding of anode kinetics governing current density is limited in the MXCs. In this study we first assessed microbial community and electrochemical kinetic parameters for biofilms on individual anodes in a multi-anode MXC to better comprehend anode fundamentals. Microbial community analysis using 16S rRNA illumine sequencing showed that Geobactor genus, one of the most kinetically efficient anode-respiring bacteria (ARB), was abundant (87%) only on the biofilm anode closest to a reference electrode in which current density was the highest among four anodes. In comparison, Geobacter populations were less than 11% for other three anodes more distant from the reference electrode, generating small current density. Half-saturation anode potential (EKA) was the lowest at -0.251 to -0.242 V (vs. standard hydrogen electrode) for the closest anode, while EKA was as high as -0.134 V for the farthest anode. Our study clearly proves that ohmic resistance changes anode potential which mainly causes different biofilm communities on individual anodes and consequently influences anode kinetics. This study explored the use of multiple anodes in microelectrochemical cells and the microbial community on these anodes, as a function of the efficiency in producing hydrogen peroxide.

  18. Methods of affecting nitrogen assimilation in plants

    DOEpatents

    Coruzzi, Gloria; Gutierrez, Rodrigo A.; Nero, Damion C.

    2016-10-11

    Provided herein are compositions and methods for producing transgenic plants. In specific embodiments, transgenic plants comprise a construct comprising a polynucleotide encoding CCA1, GLK1 or bZIP1, operably linked to a plant-specific promote, wherein the CCA1, GLK1 or bZIP1 is ectopically overexpressed in the transgenic plants, and wherein the promoter is optionally a constitutive or inducible promoter. In other embodiments, transgenic plants in which express a lower level of CCA1, GLK1 or bZIP1 are provided. Also provided herein are commercial products (e.g., pulp, paper, paper products, or lumber) derived from the transgenic plants (e.g., transgenic trees) produced using the methods provided herein.

  19. Effects of trampling limitation on coastal dune plant communities.

    PubMed

    Santoro, Riccardo; Jucker, Tommaso; Prisco, Irene; Carboni, Marta; Battisti, Corrado; Acosta, Alicia T R

    2012-03-01

    Sandy coastlines are sensitive ecosystems where human activities can have considerable negative impacts. In particular, trampling by beach visitors is a disturbance that affects dune vegetation both at the species and community level. In this study we assess the effects of the limitation of human trampling on dune vegetation in a coastal protected area of Central Italy. We compare plant species diversity in two recently fenced sectors with that of an unfenced area (and therefore subject to human trampling) using rarefaction curves and a diversity/dominance approach during a two year study period. Our results indicate that limiting human trampling seems to be a key factor in driving changes in the plant diversity of dune systems. In 2007 the regression lines of species abundance as a function of rank showed steep slopes and high Y-intercept values in all sectors, indicating a comparable level of stress and dominance across the entire study site. On the contrary, in 2009 the regression lines of the two fenced sectors clearly diverge from that of the open sector, showing less steep slopes. This change in the slopes of the tendency lines, evidenced by the diversity/dominance diagrams and related to an increase in species diversity, suggests the recovery of plant communities in the two fences between 2007 and 2009. In general, plant communities subject to trampling tended to be poorer in species and less structured, since only dominant and tolerant plant species persisted. Furthermore, limiting trampling appears to have produced positive changes in the dune vegetation assemblage after a period of only two years. These results are encouraging for the management of coastal dune systems. They highlight how a simple and cost-effective management strategy, based on passive recovery conservation measures (i.e., fence building), can be a quick (1–2 years) and effective method for improving and safeguarding the diversity of dune plant communities.

  20. Decomposers (Lumbricidae, Collembola) affect plant performance in model grasslands of different diversity.

    PubMed

    Partsch, Stephan; Milcu, Alexandru; Scheu, Stefan

    2006-10-01

    Decomposer invertebrates influence soil structure and nutrient mineralization as well as the activity and composition of the microbial community in soil and therefore likely affect plant performance and plant competition. We established model grassland communities in a greenhouse to study the interrelationship between two different functional groups of decomposer invertebrates, Lumbricidae and Collembola, and their effect on plant performance and plant nitrogen uptake in a plant diversity gradient. Common plant species of Central European Arrhenatherion grasslands were transplanted into microcosms with numbers of plant species varying from one to eight and plant functional groups varying from one to four. Separate and combined treatments with earthworms and collembolans were set up. Microcosms contained 15N labeled litter to track N fluxes into plant shoots. Presence of decomposers strongly increased total plant and plant shoot biomass. Root biomass decreased in the presence of collembolans and even more in the presence of earthworms. However, it increased when both animal groups were present. Also, presence of decomposers increased total N concentration and 15N enrichment of grasses, legumes, and small herbs. Small herbs were at a maximum in the combined treatment with earthworms and collembolans. The impact of earthworms and collembolans on plant performance strongly varied with plant functional group identity and plant species diversity and was modified when both decomposers were present. Both decomposer groups generally increased aboveground plant productivity through effects on litter decomposition and nutrient mineralization leading to an increased plant nutrient acquisition. The non-uniform effects of earthworms and collembolans suggest that functional diversity of soil decomposer animals matters and that the interactions between soil animal functional groups affect the structure of plant communities.

  1. Plant Hormones: How They Affect Root Formation.

    ERIC Educational Resources Information Center

    Reinhard, Diana Hereda

    This science study aid, produced by the U.S. Department of Agriculture, includes a series of plant rooting activities for secondary science classes. The material in the pamphlet is written for students and includes background information on plant hormones, a vocabulary list, and five learning activities. Objectives, needed materials, and…

  2. Mutualistic fungus promotes plant invasion into diverse communities.

    PubMed

    Rudgers, Jennifer A; Mattingly, W Brett; Koslow, Jennifer M

    2005-07-01

    Reducing the biological diversity of a community may decrease its resistance to invasion by exotic species. Manipulative experiments typically support this hypothesis but have focused mainly on one trophic level (i.e., primary producers). To date, we know little about how positive interactions among species may influence the relationship between diversity and invasibility, which suggests a need for research that addresses the question: under what conditions does diversity affect resistance to invasion? We used experimental manipulations of both plant diversity and the presence of an endophytic fungus to test whether a fungal mutualist of an invasive grass species (Lolium arundinaceum) switches the relationship between plant community diversity and resistance to invasion. Association with the fungal endophyte (Neotyphodium coenophialum) increased the ability of L. arundinaceum to invade communities with greater species diversity. In the absence of the endophyte, the initial diversity of the community significantly reduced the establishment of L. arundinaceum. However, establishment was independent of initial diversity in the presence of the endophyte. Fungal symbionts, like other key species, are often overlooked in studies of plant diversity, yet their presence may explain variation among studies in the effect of diversity on resistance to invasion.

  3. Trophic network architecture of root-associated bacterial communities determines pathogen invasion and plant health.

    PubMed

    Wei, Zhong; Yang, Tianjie; Friman, Ville-Petri; Xu, Yangchun; Shen, Qirong; Jousset, Alexandre

    2015-09-24

    Host-associated bacterial communities can function as an important line of defence against pathogens in animals and plants. Empirical evidence and theoretical predictions suggest that species-rich communities are more resistant to pathogen invasions. Yet, the underlying mechanisms are unclear. Here, we experimentally test how the underlying resource competition networks of resident bacterial communities affect invasion resistance to the plant pathogen Ralstonia solanacearum in microcosms and in tomato plant rhizosphere. We find that bipartite resource competition networks are better predictors of invasion resistance compared with resident community diversity. Specifically, communities with a combination of stabilizing configurations (low nestedness and high connectance), and a clear niche overlap with the pathogen, reduce pathogen invasion success, constrain pathogen growth within invaded communities and have lower levels of diseased plants in greenhouse experiments. Bacterial resource competition network characteristics can thus be important in explaining positive diversity-invasion resistance relationships in bacterial rhizosphere communities.

  4. Divergent composition but similar function of soil food webs of individual plants: plant species and community effects.

    PubMed

    Bezemer, T M; Fountain, M T; Barea, J M; Christensen, S; Dekker, S C; Duyts, H; van Hal, R; Harvey, J A; Hedlund, K; Maraun, M; Mikola, J; Mladenov, A G; Robin, C; de Ruiter, P C; Scheu, S; Setälä, H; Smilauer, P; van der Putten, W H

    2010-10-01

    Soils are extremely rich in biodiversity, and soil organisms play pivotal roles in supporting terrestrial life, but the role that individual plants and plant communities play in influencing the diversity and functioning of soil food webs remains highly debated. Plants, as primary producers and providers of resources to the soil food web, are of vital importance for the composition, structure, and functioning of soil communities. However, whether natural soil food webs that are completely open to immigration and emigration differ underneath individual plants remains unknown. In a biodiversity restoration experiment we first compared the soil nematode communities of 228 individual plants belonging to eight herbaceous species. We included grass, leguminous, and non-leguminous species. Each individual plant grew intermingled with other species, but all plant species had a different nematode community. Moreover, nematode communities were more similar when plant individuals were growing in the same as compared to different plant communities, and these effects were most apparent for the groups of bacterivorous, carnivorous, and omnivorous nematodes. Subsequently, we analyzed the composition, structure, and functioning of the complete soil food webs of 58 individual plants, belonging to two of the plant species, Lotus corniculatus (Fabaceae) and Plantago lanceolata (Plantaginaceae). We isolated and identified more than 150 taxa/groups of soil organisms. The soil community composition and structure of the entire food webs were influenced both by the species identity of the plant individual and the surrounding plant community. Unexpectedly, plant identity had the strongest effects on decomposing soil organisms, widely believed to be generalist feeders. In contrast, quantitative food web modeling showed that the composition of the plant community influenced nitrogen mineralization under individual plants, but that plant species identity did not affect nitrogen or carbon

  5. How Do Learning Communities Affect First-Year Latino Students?

    ERIC Educational Resources Information Center

    Huerta, Juan Carlos; Bray, Jennifer J.

    2013-01-01

    Do learning communities with pedagogies of active learning, collaborative learning, and integration of course material affect the learning, achievement, and persistence of first-year Latino university students? The data for this project was obtained from a survey of 1,330 first-year students in the First-Year Learning Community Program at Texas…

  6. Osmolyte cooperation affects turgor dynamics in plants

    PubMed Central

    Argiolas, Alfredo; Puleo, Gian Luigi; Sinibaldi, Edoardo; Mazzolai, Barbara

    2016-01-01

    Scientists have identified turgor-based actuation as a fundamental mechanism in plant movements. Plant cell turgor is generated by water influx due to the osmolyte concentration gradient through the cell wall and the plasma membrane behaving as an osmotic barrier. Previous studies have focused on turgor modulation with respect to potassium chloride (KCl) concentration changes, although KCl is not efficiently retained in the cell, and many other compounds, including L-glutamine (L-Gln) and D-glucose (D-Glc), are present in the cytosol. In fact, the contributions of other osmolytes to turgor dynamics remain to be elucidated. Here, we show the association of osmolytes and their consequent cooperative effects on the time-dependent turgor profile generated in a model cytosol consisting of KCl, D-Glc and L-Gln at experimentally measured plant motor/generic cell concentrations and at modified concentrations. We demonstrate the influence and association of the osmolytes using osmometry and NMR measurements. We also show, using a plant cell-inspired device we previously developed, that osmolyte complexes, rather than single osmolytes, permit to obtain higher turgor required by plant movements. We provide quantitative cues for deeper investigations of osmolyte transport for plant movement, and reveal the possibility of developing osmotic actuators exploiting a dynamically varying concentration of osmolytes. PMID:27445173

  7. Osmolyte cooperation affects turgor dynamics in plants

    NASA Astrophysics Data System (ADS)

    Argiolas, Alfredo; Puleo, Gian Luigi; Sinibaldi, Edoardo; Mazzolai, Barbara

    2016-07-01

    Scientists have identified turgor-based actuation as a fundamental mechanism in plant movements. Plant cell turgor is generated by water influx due to the osmolyte concentration gradient through the cell wall and the plasma membrane behaving as an osmotic barrier. Previous studies have focused on turgor modulation with respect to potassium chloride (KCl) concentration changes, although KCl is not efficiently retained in the cell, and many other compounds, including L-glutamine (L-Gln) and D-glucose (D-Glc), are present in the cytosol. In fact, the contributions of other osmolytes to turgor dynamics remain to be elucidated. Here, we show the association of osmolytes and their consequent cooperative effects on the time-dependent turgor profile generated in a model cytosol consisting of KCl, D-Glc and L-Gln at experimentally measured plant motor/generic cell concentrations and at modified concentrations. We demonstrate the influence and association of the osmolytes using osmometry and NMR measurements. We also show, using a plant cell-inspired device we previously developed, that osmolyte complexes, rather than single osmolytes, permit to obtain higher turgor required by plant movements. We provide quantitative cues for deeper investigations of osmolyte transport for plant movement, and reveal the possibility of developing osmotic actuators exploiting a dynamically varying concentration of osmolytes.

  8. Mutualistic rhizobia reduce plant diversity and alter community composition.

    PubMed

    Keller, Kane R

    2014-12-01

    Mutualistic interactions can be just as important to community dynamics as antagonistic species interactions like competition and predation. Because of their large effects on both abiotic and biotic environmental variables, resource mutualisms, in particular, have the potential to influence plant communities. Moreover, the effects of resource mutualists such as nitrogen-fixing rhizobia on diversity and community composition may be more pronounced in nutrient-limited environments. I experimentally manipulated the presence of rhizobia across a nitrogen gradient in early assembling mesocosm communities with identical starting species composition to test how the classic mutualism between nitrogen-fixing rhizobia and their legume host influence diversity and community composition. After harvest, I assessed changes in α-diversity, community composition, β-diversity, and ecosystem properties such as inorganic nitrogen availability and productivity as a result of rhizobia and nitrogen availability. The presence of rhizobia decreased plant community diversity, increased community convergence (reduced β-diversity), altered plant community composition, and increased total community productivity. These community-level effects resulted from rhizobia increasing the competitive dominance of their legume host Chamaecrista fasciculata. Moreover, different non-leguminous species responded both negatively and positively to the presence of rhizobia, indicating that rhizobia are driving both inhibitory and potentially facilitative effects in communities. These findings expand our understanding of plant communities by incorporating the effects of positive symbiotic interactions on plant diversity and composition. In particular, rhizobia that specialize on dominant plants may serve as keystone mutualists in terrestrial plant communities, reducing diversity by more than 40%.

  9. Community 15N isoscapes to resolve plant-plant-interactions at the spatial scale

    NASA Astrophysics Data System (ADS)

    Hellmann, Christine; Rascher, Katherine G.; Máguas, Cristina; Werner, Christiane

    2014-05-01

    Isoscapes have greatly improved our ability to understand biogeochemical processes on continental to global scales. However, the isoscapes framework may also have significant potential to resolve the spatial component of within-community interactions. For example, exotic plant invaders often exert strong impacts on ecosystem functioning, particularly regarding water-, carbon- and nutrient-cycles, but the spatial extent of such alterations is largely unknown. Here we show that massive N input by the N2-fixing exotic invasive Acacia longifolia to a Portuguese dune system can be traced using spatially resolved information on native plants' leaf δ15N. We found isotopic signatures of N to differ strongly between the native system (δ15N c. -10 o) and the atmospherically derived N in A. longifolia phyllodes (δ15N c. 0 o). Thus, sources of N for native plants could be readily distinguished. Leaf δ15N of a native, non-fixing species was increasingly enriched the closer the plant grew to the invader, indicating uptake of fixed N provided by A. longifolia. The enrichment was evident far beyond the stands of the invader, demonstrating that A. longifolia affected N budgets of native species up to a distance of 8 m exceeding the margin of the canopy. Furthermore, using the isoscapes approach, we were able to quantify the total area of N enrichment and could thus show that the area affected by invasion was at least 3.5 times larger than the area actually occupied by the invader. However, a native N2-fixing species had no such effects. Thus, downscaling isoscapes to the community level opens new frontiers in quantifying the spatial dimension of functional changes associated with plant invasions. Moreover, considering the feasibility and applicability of this approach, it may provide a promising tool to identify, quantify and monitor different types of functional plant-plant interactions within communities at a spatially explicit scale.

  10. How have fisheries affected parasite communities?

    USGS Publications Warehouse

    Wood, Chelsea L.; Lafferty, Kevin D.

    2015-01-01

    To understand how fisheries affect parasites, we conducted a meta-analysis of studies that contrasted parasite assemblages in fished and unfished areas. Parasite diversity was lower in hosts from fished areas. Larger hosts had a greater abundance of parasites, suggesting that fishing might reduce the abundance of parasites by selectively removing the largest, most heavily parasitized individuals. After controlling for size, the effect of fishing on parasite abundance varied according to whether the host was fished and the parasite's life cycle. Parasites of unfished hosts were more likely to increase in abundance in response to fishing than were parasites of fished hosts, possibly due to compensatory increases in the abundance of unfished hosts. While complex life cycle parasites tended to decline in abundance in response to fishing, directly transmitted parasites tended to increase. Among complex life cycle parasites, those with fished hosts tended to decline in abundance in response to fishing, while those with unfished hosts tended to increase. However, among directly transmitted parasites, responses did not differ between parasites with and without fished hosts. This work suggests that parasite assemblages are likely to change substantially in composition in increasingly fished ecosystems, and that parasite life history and fishing status of the host are important in predicting the response of individual parasite species or groups to fishing.

  11. Conceptual hierarchical modeling to describe wetland plant community organization

    USGS Publications Warehouse

    Little, A.M.; Guntenspergen, G.R.; Allen, T.F.H.

    2010-01-01

    Using multivariate analysis, we created a hierarchical modeling process that describes how differently-scaled environmental factors interact to affect wetland-scale plant community organization in a system of small, isolated wetlands on Mount Desert Island, Maine. We followed the procedure: 1) delineate wetland groups using cluster analysis, 2) identify differently scaled environmental gradients using non-metric multidimensional scaling, 3) order gradient hierarchical levels according to spatiotem-poral scale of fluctuation, and 4) assemble hierarchical model using group relationships with ordination axes and post-hoc tests of environmental differences. Using this process, we determined 1) large wetland size and poor surface water chemistry led to the development of shrub fen wetland vegetation, 2) Sphagnum and water chemistry differences affected fen vs. marsh / sedge meadows status within small wetlands, and 3) small-scale hydrologic differences explained transitions between forested vs. non-forested and marsh vs. sedge meadow vegetation. This hierarchical modeling process can help explain how upper level contextual processes constrain biotic community response to lower-level environmental changes. It creates models with more nuanced spatiotemporal complexity than classification and regression tree procedures. Using this process, wetland scientists will be able to generate more generalizable theories of plant community organization, and useful management models. ?? Society of Wetland Scientists 2009.

  12. Community Support of Ethanol Plants: Does Local Ownership Matter?

    ERIC Educational Resources Information Center

    Bain, Carmen; Prokos, Anastasia; Liu, Hexuan

    2012-01-01

    Drawing on data from six communities in Kansas and Iowa, we explore the factors that are related to community members' current levels of overall support for local ethanol plants. What are residents' opinions about the benefits and drawbacks of local ownership of ethanol plants? How does that awareness lead to overall support of plants? Our…

  13. Investigating Effects of Invasive Species on Plant Community Structure

    ERIC Educational Resources Information Center

    Franklin, Wilfred

    2008-01-01

    In this article, the author presents a field study project that explores factors influencing forest community structure and lifts the veil off of "plant blindness." This ecological study consists of three laboratories: (1) preliminary field trip to the study site; (2) plant survey; and (3) analyzing plant community structure with descriptive…

  14. Asynchronous responses of soil microbial community and understory plant community to simulated nitrogen deposition in a subtropical forest.

    PubMed

    Wu, Jianping; Liu, Wenfei; Fan, Houbao; Huang, Guomin; Wan, Songze; Yuan, Yinghong; Ji, Chunfeng

    2013-10-01

    Atmospheric nitrogen (N) deposition greatly affects ecosystem processes and properties. However, few studies have simultaneously examined the responses of both the above- and belowground communities to N deposition. Here, we investigated the effects of 8 years of simulated N deposition on soil microbial communities and plant diversity in a subtropical forest. The quantities of experimental N added (g of N m(-2) year(-1)) and treatment codes were 0 (N0, control), 6 (N1), 12 (N2), and 24 (N3). Phospholipid fatty acids (PLFAs) analysis was used to characterize the soil microbial community while plant diversity and coverage were determined in the permanent field plots. Microbial abundance was reduced by the N3 treatment, and plant species richness and coverage were reduced by both N2 and N3 treatments. Declines in plant species richness were associated with decreased abundance of arbuscular mycorrhizal fungi, increased bacterial stress index, and reduced soil pH. The plasticity of soil microbial community would be more related to the different responses among treatments when compared with plant community. These results indicate that long-term N deposition has greater effects on the understory plant community than on the soil microbial community and different conservation strategies should be considered.

  15. Alien Roadside Species More Easily Invade Alpine than Lowland Plant Communities in a Subarctic Mountain Ecosystem

    PubMed Central

    Lembrechts, Jonas J.; Milbau, Ann; Nijs, Ivan

    2014-01-01

    Effects of roads on plant communities are not well known in cold-climate mountain ecosystems, where road building and development are expected to increase in future decades. Knowledge of the sensitivity of mountain plant communities to disturbance by roads is however important for future conservation purposes. We investigate the effects of roads on species richness and composition, including the plant strategies that are most affected, along three elevational gradients in a subarctic mountain ecosystem. We also examine whether mountain roads promote the introduction and invasion of alien plant species from the lowlands to the alpine zone. Observations of plant community composition were made together with abiotic, biotic and anthropogenic factors in 60 T-shaped transects. Alpine plant communities reacted differently to road disturbances than their lowland counterparts. On high elevations, the roadside species composition was more similar to that of the local natural communities. Less competitive and ruderal species were present at high compared with lower elevation roadsides. While the effects of roads thus seem to be mitigated in the alpine environment for plant species in general, mountain plant communities are more invasible than lowland communities. More precisely, relatively more alien species present in the roadside were found to invade into the surrounding natural community at high compared to low elevations. We conclude that effects of roads and introduction of alien species in lowlands cannot simply be extrapolated to the alpine and subarctic environment. PMID:24586947

  16. [Maintenance capacity of plant community diversity of wetlands in patch scale].

    PubMed

    Sun, Xian-bin; Liu, Hong-yu; Zhang, Xiao-hong; Hu, Jun-na

    2009-03-01

    Based on GIS and principal component analysis method, this paper analyzed the relationships between the patch characteristics and the plant community diversity in the patches of wetlands in Naoli River Watershed in 1950, 1967, 1983 and 2000. The results showed that in 1950-2000, the average patch size of the wetlands and the number of the patches that had the capacity of maintaining more than two types of wetland plant community decreased dramatically, and the minimum patch size was 10.1 km2. Both the plant community diversity index and the number of plant community types had significant positive correlations with the patch size of the wetlands. The larger the patch size, the higher maintenance capacity of plant community diversity. With the decrease of patch size, the patch fragmentation index and patch fragmental dimension increased, while the patch shape index and the plant community diversity index in the patches decreased. With the increase of patch spatial separation, the plant community diversity index in the patches decreased. Principal component analysis indicated that patch size was the most important factor affecting the plant community diversity of wetlands, followed by patch fragmentation and separation.

  17. The impact of plant chemical diversity on plant-herbivore interactions at the community level.

    PubMed

    Salazar, Diego; Jaramillo, Alejandra; Marquis, Robert J

    2016-08-01

    Understanding the role of diversity in ecosystem processes and species interactions is a central goal of ecology. For plant-herbivore interactions, it has been hypothesized that when plant species diversity is reduced, loss of plant biomass to herbivores increases. Although long-standing, this hypothesis has received mixed support. Increasing plant chemical diversity with increasing plant taxonomic diversity is likely to be important for plant-herbivore interactions at the community level, but the role of chemical diversity is unexplored. Here we assess the effect of volatile chemical diversity on patterns of herbivore damage in naturally occurring patches of Piper (Piperaceae) shrubs in a Costa Rican lowland wet forest. Volatile chemical diversity negatively affected total, specialist, and generalist herbivore damage. Furthermore, there were differences between the effects of high-volatility and low-volatility chemical diversity on herbivore damage. High-volatility diversity reduced specialist herbivory, while low-volatility diversity reduced generalist herbivory. Our data suggest that, although increased plant diversity is expected to reduce average herbivore damage, this pattern is likely mediated by the diversity of defensive compounds and general classes of anti-herbivore traits, as well as the degree of specialization of the herbivores attacking those plants.

  18. Plant community response to landscape connectivity and patch shape.

    SciTech Connect

    Damschen, Ellen I.

    2005-07-01

    Ph.D Dissertation. North Carolina State University. Raleigh, North Carolina. 135 pp. Abstract. Land transformation is the single most important factor promoting the global loss of terrestrial biological diversity. Remaining habitat fragments contain more edges, less interior habitat, and are more isolated from other habitat fragments, all of which decrease rates of colonization following local extinctions, reduce reproductive rates and gene flow between populations, and ultimately lead to species extinctions. The best approach to prevent species loss, therefore, is to preserve greater areas of habitat. In many cases, however, habitat has already been fragmented and strategies are needed to configure and manage the remaining land. Land managers often create reserve networks that incorporate the use of landscape corridors, linear strips of habitat connecting isolated patches, to reduce species loss by increasing colonizations and decreasing extinctions. Most empirical tests of corridors have been limited to individuals and populations, leaving corridor effects on diversity largely unknown, especially at large spatial scales. Additionally, only a handful of studies have examined corridor effects on plants, which may be especially sensitive to the abiotic changes resulting from alterations in patch shape due to dispersal limitation. Using one of the best-replicated, large-scale habitat fragmentation experiments, I tested explicitly for corridor effects on plant community diversity and composition by examining the established plant community and the soil seedbank. My experimental design distinguished among the three possible ways corridors can affect between-patch processes: by acting as a movement conduit between connected patches (“connectivity effects”), by increasing area alone (“area effects”), and by intercepting organisms moving across the landscape and filtering them into connected patches (“drift-fence effects”). Additionally, I tested for the

  19. Rhizosphere microbiome assemblage is affected by plant development

    PubMed Central

    Chaparro, Jacqueline M; Badri, Dayakar V; Vivanco, Jorge M

    2014-01-01

    There is a concerted understanding of the ability of root exudates to influence the structure of rhizosphere microbial communities. However, our knowledge of the connection between plant development, root exudation and microbiome assemblage is limited. Here, we analyzed the structure of the rhizospheric bacterial community associated with Arabidopsis at four time points corresponding to distinct stages of plant development: seedling, vegetative, bolting and flowering. Overall, there were no significant differences in bacterial community structure, but we observed that the microbial community at the seedling stage was distinct from the other developmental time points. At a closer level, phylum such as Acidobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria and specific genera within those phyla followed distinct patterns associated with plant development and root exudation. These results suggested that the plant can select a subset of microbes at different stages of development, presumably for specific functions. Accordingly, metatranscriptomics analysis of the rhizosphere microbiome revealed that 81 unique transcripts were significantly (P<0.05) expressed at different stages of plant development. For instance, genes involved in streptomycin synthesis were significantly induced at bolting and flowering stages, presumably for disease suppression. We surmise that plants secrete blends of compounds and specific phytochemicals in the root exudates that are differentially produced at distinct stages of development to help orchestrate rhizosphere microbiome assemblage. PMID:24196324

  20. An Exploration of Hypotheses that Explain Herbivore and Pathogen Attack in Restored Plant Communities

    PubMed Central

    Blaisdell, G. Kai; Roy, Bitty A.; Pfeifer-Meister, Laurel; Bridgham, Scott D.

    2015-01-01

    Many hypotheses address the associations of plant community composition with natural enemies, including: (i) plant species diversity may reduce enemy attack, (ii) attack may increase as host abundance increases, (iii) enemy spillover may lead to increased attack on one host species due to transmission from another host species, or enemy dilution may lead to reduced attack on a host that would otherwise have more attack, (iv) physical characteristics of the plant community may influence attack, and (v) plant vigor may affect attack. Restoration experiments with replicated plant communities provide an exceptional opportunity to explore these hypotheses. To explore the relative predictive strengths of these related hypotheses and to investigate the potential effect of several restoration site preparation techniques, we surveyed arthropod herbivore and fungal pathogen attack on the six most common native plant species in a restoration experiment. Multi-model inference revealed a weak but consistent negative correlation with pathogen attack and host diversity across the plant community, and no correlation between herbivory and host diversity. Our analyses also revealed host species-specific relationships between attack and abundance of the target host species, other native plant species, introduced plant species, and physical community characteristics. We found no relationship between enemy attack and plant vigor. We found minimal differences in plant community composition among several diverse site preparation techniques, and limited effects of site preparation techniques on attack. The strongest associations of community characteristics with attack varied among plant species with no community-wide patterns, suggesting that no single hypothesis successfully predicts the dominant community-wide trends in enemy attack. PMID:25699672

  1. Mesoherbivores affect grasshopper communities in a megaherbivore-dominated South African savannah.

    PubMed

    van der Plas, Fons; Olff, Han

    2014-06-01

    African savannahs are among the few places on earth where diverse communities of mega- and meso-sized ungulate grazers dominate ecosystem functioning. Less conspicuous, but even more diverse, are the communities of herbivorous insects such as grasshoppers, which share the same food. Various studies investigated the community assembly of these groups separately, but it is poorly known how ungulate communities shape grasshopper communities. Here, we investigated how ungulate species of different body size alter grasshopper communities in a South African savannah. White rhino is the most abundant vertebrate herbivore in our study site. Other common mesoherbivores include buffalo, zebra and impala. We hypothesized that white rhinos would have greater impact than mesoherbivores on grasshopper communities. Using 10-year-old exclosures, at eight sites we compared the effects of ungulates on grasshopper communities in three nested treatments: (i) unfenced plots ('control plots') with all vertebrate herbivores present, (ii) plots with a low cable fence, excluding white rhino ('megaherbivore exclosures'), and (iii) plots with tall fences, excluding all herbivores larger than rodents ('complete ungulate exclosures'). In each plot, we collected data of vegetation structure, grass and grasshopper community composition. Complete ungulate exclosures contained 30% taller vegetation than megaherbivore exclosures and they were dominated by different grass and grasshopper species. Grasshoppers in complete ungulate exclosures were on average 3.5 mm longer than grasshoppers in megaherbivore exclosures, possibly due to changes in plant communities or vegetation structure. We conclude that surprisingly, in this megaherbivore hotspot, mesoherbivores, instead of megaherbivores, most strongly affect grasshopper communities.

  2. Fungal-fungal associations affect the assembly of endophyte communities in maize (Zea mays).

    PubMed

    Pan, Jean J; May, Georgiana

    2009-10-01

    Many factors can affect the assembly of communities, ranging from species pools to habitat effects to interspecific interactions. In microbial communities, the predominant focus has been on the well-touted ability of microbes to disperse and the environment acting as a selective filter to determine which species are present. In this study, we investigated the role of biotic interactions (e.g., competition, facilitation) in fungal endophyte community assembly by examining endophyte species co-occurrences within communities using null models. We used recombinant inbred lines (genotypes) of maize (Zea mays) to examine community assembly at multiple habitat levels, at the individual plant and host genotype levels. Both culture-dependent and culture-independent approaches were used to assess endophyte communities. Communities were analyzed using the complete fungal operational taxonomic unit (OTU) dataset or only the dominant (most abundant) OTUs in order to ascertain whether species co-occurrences were different for dominant members compared to when all members were included. In the culture-dependent approach, we found that for both datasets, OTUs co-occurred on maize genotypes more frequently than expected under the null model of random species co-occurrences. In the culture-independent approach, we found that OTUs negatively co-occurred at the individual plant level but were not significantly different from random at the genotype level for either the dominant or complete datasets. Our results showed that interspecific interactions can affect endophyte community assembly, but the effects can be complex and depend on host habitat level. To our knowledge, this is the first study to examine endophyte community assembly in the same host species at multiple habitat levels. Understanding the processes and mechanisms that shape microbial communities will provide important insights into microbial community structure and the maintenance of microbial biodiversity.

  3. Earthworm-mycorrhiza interactions can affect the diversity, structure and functioning of establishing model grassland communities.

    PubMed

    Zaller, Johann G; Heigl, Florian; Grabmaier, Andrea; Lichtenegger, Claudia; Piller, Katja; Allabashi, Roza; Frank, Thomas; Drapela, Thomas

    2011-01-01

    Both earthworms and arbuscular mycorrhizal fungi (AMF) are important ecosystem engineers co-occurring in temperate grasslands. However, their combined impacts during grassland establishment are poorly understood and have never been studied. We used large mesocosms to study the effects of different functional groups of earthworms (i.e., vertically burrowing anecics vs. horizontally burrowing endogeics) and a mix of four AMF taxa on the establishment, diversity and productivity of plant communities after a simulated seed rain of 18 grassland species comprising grasses, non-leguminous forbs and legumes. Moreover, effects of earthworms and/or AMF on water infiltration and leaching of ammonium, nitrate and phosphate were determined after a simulated extreme rainfall event (40 l m(-2)). AMF colonisation of all three plant functional groups was altered by earthworms. Seedling emergence and diversity was reduced by anecic earthworms, however only when AMF were present. Plant density was decreased in AMF-free mesocosms when both anecic and endogeic earthworms were active; with AMF also anecics reduced plant density. Plant shoot and root biomass was only affected by earthworms in AMF-free mesocosms: shoot biomass increased due to the activity of either anecics or endogeics; root biomass increased only when anecics were active. Water infiltration increased when earthworms were present in the mesocosms but remained unaffected by AMF. Ammonium leaching was increased only when anecics or a mixed earthworm community was active but was unaffected by AMF; nitrate and phosphate leaching was neither affected by earthworms nor AMF. Ammonium leaching decreased with increasing plant density, nitrate leaching decreased with increasing plant diversity and density. In order to understand the underlying processes of these interactions further investigations possibly under field conditions using more diverse belowground communities are required. Nevertheless, this study demonstrates that

  4. Genetics-based interactions among plants, pathogens, and herbivores define arthropod community structure.

    PubMed

    Busby, Posy E; Lamit, Louis J; Keith, Arthur R; Newcombe, George; Gehring, Catherine A; Whitham, Thomas G; Dirzo, Rodolfo

    2015-07-01

    Plant resistance to pathogens or insect herbivores is common, but its potential for indirectly influencing plant-associated communities is poorly known. Here, we test whether pathogens' indirect effects on arthropod communities and herbivory depend on plant resistance to pathogens and/or herbivores, and address the overarching interacting foundation species hypothesis that genetics-based interactions among a few highly interactive species can structure a much larger community. In a manipulative field experiment using replicated genotypes of two Populus species and their interspecific hybrids, we found that genetic variation in plant resistance to both pathogens and insect herbivores modulated the strength of pathogens' indirect effects on arthropod communities and insect herbivory. First, due in part to the pathogens' differential impacts on leaf biomass among the two Populus species and the hybrids, the pathogen most strongly impacted arthropod community composition, richness, and abundance on the pathogen-susceptible tree species. Second, we found similar patterns comparing pathogen-susceptible and pathogen-resistant genotypes within species. Third, within a plant species, pathogens caused a fivefold greater reduction in herbivory on insect-herbivore-susceptible plant genotypes than on herbivore-resistant genotypes, demonstrating that the pathogen-herbivore interaction is genotype dependent. We conclude that interactions among plants, pathogens, and herbivores can structure multitrophic communities, supporting the interacting foundation species hypothesis. Because these interactions are genetically based, evolutionary changes in genetic resistance could result in ecological changes in associated communities, which may in turn feed back to affect plant fitness.

  5. Herbivore exclusion promotes a more stochastic plant community assembly in a natural grassland.

    PubMed

    Alberti, Juan; Bakker, Elisabeth S; van Klink, Roel; Olff, Han; Smit, Christian

    2017-04-01

    Both bottom-up (e.g., nutrients) and top-down (e.g., herbivory) forces structure plant communities, but it remains unclear how they affect the relative importance of stochastic and deterministic processes in plant community assembly. Moreover, different-sized herbivores have been shown to have contrasting effects on community structure and function, but their effects on the processes governing community assembly (i.e., how they generate the impacts on structure) remain largely unknown. We evaluated the influence of bottom-up and top-down forces on the relative importance of deterministic and stochastic processes during plant community assembly. We used the data of a 7-yr factorial experiment manipulating nutrient availability (ambient and increased) and the presence of vertebrate herbivores (>1 kg) of different body size in a floodplain grassland in The Netherlands. We used a null model that describes a community composition expected by chance (i.e., stochastic assembly) and compared the plant community composition in the different treatments with this null model (the larger the difference, the more deterministically assembled). Our results showed that herbivore exclusion promoted a more stochastic plant community assembly, whereas increased nutrients played a relatively minor role in determining the relative importance of stochasticity in community assembly. Large herbivores facilitated intermediate-sized mammal herbivores, resulting in synergistic effects of enhanced grazing pressure and a more deterministic and convergent plant community assembly. We conclude that herbivores can act as strong deterministic forces during community assembly in natural systems. Our results also reveal that although large- and intermediate-sized mammal herbivores often have contrasting effects on many community and ecosystem properties, they can also synergistically homogenize plant communities.

  6. Community structure affects trophic ontogeny in a predatory fish.

    PubMed

    Sánchez-Hernández, Javier; Eloranta, Antti P; Finstad, Anders G; Amundsen, Per-Arne

    2017-01-01

    While most studies have focused on the timing and nature of ontogenetic niche shifts, information is scarce about the effects of community structure on trophic ontogeny of top predators. We investigated how community structure affects ontogenetic niche shifts (i.e., relationships between body length, trophic position, and individual dietary specialization) of a predatory fish, brown trout (Salmo trutta). We used stable isotope and stomach content analyses to test how functional characteristics of lake fish community compositions (competition and prey availability) modulate niche shifts in terms of (i) piscivorous behavior, (ii) trophic position, and (iii) individual dietary specialization. Northern Scandinavian freshwater fish communities were used as a study system, including nine subarctic lakes with contrasting fish community configurations: (i) trout-only systems, (ii) two-species systems (brown trout and Arctic charr [Salvelinus alpinus] coexisting), and (iii) three-species systems (brown trout, Arctic charr, and three-spined sticklebacks [Gasterosteus aculeatus] coexisting). We expected that the presence of profitable small prey (stickleback) and mixed competitor-prey fish species (charr) supports early piscivory and high individual dietary specialization among trout in multispecies communities, whereas minor ontogenetic shifts were expected in trout-only systems. From logistic regression models, the presence of a suitable prey fish species (stickleback) emerged as the principal variable determining the size at ontogenetic niche shifts. Generalized additive mixed models indicated that fish community structure shaped ontogenetic niche shifts in trout, with the strongest positive relationships between body length, trophic position, and individual dietary specialization being observed in three-species communities. Our findings revealed that the presence of a small-sized prey fish species (stickleback) rather than a mixed competitor-prey fish species (charr) was

  7. Affective state and community integration after traumatic brain injury.

    PubMed

    Juengst, Shannon B; Arenth, Patricia M; Raina, Ketki D; McCue, Michael; Skidmore, Elizabeth R

    2014-12-01

    Previous studies investigating the relationship between affective state and community integration have focused primarily on the influence of depression and anxiety. In addition, they have focused on frequency of participation in various activities, failing to address an individual's subjective satisfaction with participation. The purpose of this study was to examine how affective state contributes to frequency of participation and satisfaction with participation after traumatic brain injury among participants with and without a current major depressive episode. Sixty-four community-dwelling participants with a history of complicated mild-to-severe traumatic brain injury participated in this cross-sectional cohort study. High positive affect contributed significantly to frequency of participation (β = 0.401, P = 0.001), and both high positive affect and low negative affect significantly contributed to better satisfaction with participation (F2,61 = 13.63, P < 0.001). Further investigation to assess the direction of these relationships may better inform effective targets for intervention. These findings highlight the importance of assessing affective state after traumatic brain injury and incorporating a subjective measure of participation when considering community integration outcomes.

  8. Pyridine-type alkaloid composition affects bacterial community composition of floral nectar

    PubMed Central

    Aizenberg-Gershtein, Yana; Izhaki, Ido; Santhanam, Rakesh; Kumar, Pavan; Baldwin, Ian T.; Halpern, Malka

    2015-01-01

    Pyridine-type alkaloids are most common in Nicotiana species. To study the effect of alkaloid composition on bacterial community composition in floral nectar, we compared the nicotine-rich wild type (WT) N. attenuata, the nicotine biosynthesis-silenced N. attenuata that was rich in anatabine and the anabasine-rich WT N. glauca plants. We found that the composition of these secondary metabolites in the floral nectar drastically affected the bacterial community richness, diversity and composition. Significant differences were found between the bacterial community compositions in the nectar of the three plants with a much greater species richness and diversity in the nectar from the transgenic plant. The highest community composition similarity index was detected between the two wild type plants. The different microbiome composition and diversity, caused by the different pyridine-type alkaloid composition, could modify the nutritional content of the nectar and consequently, may contribute to the change in the nectar consumption and visitation. These may indirectly have an effect on plant fitness. PMID:26122961

  9. Increasing land-use intensity decreases floral colour diversity of plant communities in temperate grasslands.

    PubMed

    Binkenstein, Julia; Renoult, Julien P; Schaefer, H Martin

    2013-10-01

    To preserve biodiversity and ecosystem functions in a globally changing world it is crucial to understand the effect of land use on ecosystem processes such as pollination. Floral colouration is known to be central in plant-pollinator interactions. To date, it is still unknown whether land use affects the colouration of flowering plant communities. To assess the effect of land use on the diversity and composition of flower colours in temperate grasslands, we collected data on the number of flowering plant species, blossom cover and flower reflectance spectra from 69 plant communities in two German regions, Schwäbische Alb (SA) and Hainich-Dün (HD). We analysed reflectance data of flower colours as they are perceived by honeybees and studied floral colour diversity based upon spectral loci of each flowering plant species in the Maxwell triangle. Before the first mowing, flower colour diversity decreased with increasing land-use intensity in SA, accompanied by a shift of mean flower colours of communities towards an increasing proportion of white blossom cover in both regions. By changing colour characteristics of grasslands, we suggest that increasing land-use intensity can affect the flower visitor fauna in terms of visitor behaviour and diversity. These changes may in turn influence plant reproduction in grassland plant communities. Our results indicate that land use is likely to affect communication processes between plants and flower visitors by altering flower colour traits.

  10. Host plant species affects virulence in monarch butterfly parasites.

    PubMed

    de Roode, Jacobus C; Pedersen, Amy B; Hunter, Mark D; Altizer, Sonia

    2008-01-01

    1. Studies have considered how intrinsic host and parasite properties determine parasite virulence, but have largely ignored the role of extrinsic ecological factors in its expression. 2. We studied how parasite genotype and host plant species interact to determine virulence of the protozoan parasite Ophryocystis elektroscirrha (McLaughlin & Myers 1970) in the monarch butterfly Danaus plexippus L. We infected monarch larvae with one of four parasite genotypes and reared them on two milkweed species that differed in their levels of cardenolides: toxic chemicals involved in predator defence. 3. Parasite infection, replication and virulence were affected strongly by host plant species. While uninfected monarchs lived equally long on both plant species, infected monarchs suffered a greater reduction in their life spans (55% vs. 30%) on the low-cardenolide vs. the high-cardenolide host plant. These life span differences resulted from different levels of parasite replication in monarchs reared on the two plant species. 4. The virulence rank order of parasite genotypes was unaffected by host plant species, suggesting that host plant species affected parasite genotypes similarly, rather than through complex plant species-parasite genotype interactions. 5. Our results demonstrate that host ecology importantly affects parasite virulence, with implications for host-parasite dynamics in natural populations.

  11. Nutrient enrichment alters impacts of Hydrocotyle vulgaris invasion on native plant communities

    PubMed Central

    Liu, Lin; Quan, Han; Dong, Bi-Cheng; Bu, Xiang-Qi; Li, Lin; Liu, Fu-De; Lei, Guang-Chun; Li, Hong-Li

    2016-01-01

    Nutrients may affect the invasiveness of alien plants and the invasibility of native plant communities. We performed a greenhouse experiment to investigate the interactive effect of invasion by a clonal herb Hydrocotyle vulgaris and nutrient enrichment on biomass and evenness of native plant communities. We established three types of plant communities (H. vulgaris alone, native plant communities without or with H. vulgaris) under low and high levels of nutrients. Native communities consisted of eight native, terrestrial species of three functional groups, i.e. four grasses, two legumes, and two forbs. Invasion of H. vulgaris had no effect on biomass of the native community, the functional groups, or the individual species. High nutrients increased biomass of grasses, but reduced evenness of the community. High nutrients also decreased the competitive effect, and the relative dominance index of H. vulgaris. Therefore, high nutrients reduced the competitive ability of H. vulgaris and enhanced the resistance of the native community to invasion. The results provide a basis for management strategies to control the invasion and spread of H. vulgaris by manipulating resource availability to support native communities. PMID:27995984

  12. Plant community influence on soil microbial response after a wildfire in Sierra Nevada National Park (Spain).

    PubMed

    Bárcenas-Moreno, Gema; García-Orenes, Fuensanta; Mataix-Solera, Jorge; Mataix-Beneyto, Jorge

    2016-12-15

    Plant community influence on microbial response after fire has been studied in a Sierra Nevada National Park area affected by a wildfire in 2005. Two different plant communities adapted to different altitudes were selected to analyse possible differences on soil microbial recolonisation process after fire, in oak forest and high mountain shrub communities. Microbial abundance, activity and community composition were monitored to evaluate medium-term changes. Microbial abundance was studied by mean of microbial biomass carbon and plate count methods; microbial activity was analysed by microbial respiration and bacterial growth while microbial community composition was determined by analysing phospholipid fatty acid pattern. Under unburnt conditions oak forest showed higher nutrient content, pH and microbial abundance and activity values than the high mountain shrubs community. Different parameters studied showed different trends with time, highlighting important changes in microbial community composition in high mountain shrubs from first sampling to the second one. Post-fire recolonisation process was different depending on plant community studied. Highlighting fungal response and microbial activity were stimulated in burnt high mountain shrubs community whilst it was negatively affected in oak forest. Fire induced changes in oak forest were almost neutralized 20months after the fire, while high mountain shrubs community still showed fire-induced changes at the end of the study.

  13. Microbial abundance and community in subsurface flow constructed wetland microcosms: role of plant presence.

    PubMed

    Wang, Qian; Xie, Huijun; Ngo, Huu Hao; Guo, Wenshan; Zhang, Jian; Liu, Cui; Liang, Shuang; Hu, Zhen; Yang, Zhongchen; Zhao, Congcong

    2016-03-01

    In this research, the role of plants in improving microorganism growth conditions in subsurface flow constructed wetland (CW) microcosms was determined. In particular, microbial abundance and community were investigated during summer and winter in Phragmites australis-planted CW microcosms (PA) and unplanted CW microcosms (control, CT). Results revealed that the removal efficiencies of pollutants and microbial community structure varied in winter with variable microbial abundance. During summer, PA comprised more dominant phyla (e.g., Proteobacteria, Actinobacteria, and Bacteroidetes), whereas CT contained more Cyanobacteria and photosynthetic bacteria. During winter, the abundance of Proteobacteria was >40 % in PA but dramatically decreased in CT. Moreover, Cyanobacteria and photosynthetic bacterial dominance in CT decreased. In both seasons, bacteria were more abundant in root surfaces than in sand. Plant presence positively affected microbial abundance and community. The potential removal ability of CT, in which Cyanobacteria and photosynthetic bacteria were abundant during summer, was more significantly affected by temperature reduction than that of PA with plant presence.

  14. Plant lignin content altered by soil microbial community.

    PubMed

    Bennett, Alison E; Grussu, Dominic; Kam, Jason; Caul, Sandra; Halpin, Claire

    2015-04-01

    Questions have been raised in various fields of research about the consequences of plants with modified lignin production. As a result of their roles in nutrient cycling and plant diversity, plant-soil interactions should be a major focus of ecological studies on lignin-modified plants. However, most studies have been decomposition studies conducted in a single soil or in sterile soil. Thus, we understand little about plant-soil interactions in living lignin-modified plants. In lignin mutants of three different barley (Hordeum vulgare) cultivars and their corresponding wild-types associated with three different soil microbial communities, we asked: do plant-soil microbiome interactions influence the lignin content of plants?; does a mutation in lignin production alter the outcome of plant-soil microbiome interactions?; does the outcome of plant-soil microbiome interactions depend on host genotype or the presence of a mutation altering lignin production? In roots, the soil community explained 6% of the variation in lignin content, but, in shoots, the soil community explained 21% of the variation in lignin content and was the only factor influencing lignin content. Neither genotype nor mutations in lignin production explained associations with fungi. Lignin content changes in response to a plant's soil microbial community, and may be a defensive response to particular components of the soil community.

  15. Plant volatiles induced by herbivore egg deposition affect insects of different trophic levels.

    PubMed

    Fatouros, Nina E; Lucas-Barbosa, Dani; Weldegergis, Berhane T; Pashalidou, Foteini G; van Loon, Joop J A; Dicke, Marcel; Harvey, Jeffrey A; Gols, Rieta; Huigens, Martinus E

    2012-01-01

    Plants release volatiles induced by herbivore feeding that may affect the diversity and composition of plant-associated arthropod communities. However, the specificity and role of plant volatiles induced during the early phase of attack, i.e. egg deposition by herbivorous insects, and their consequences on insects of different trophic levels remain poorly explored. In olfactometer and wind tunnel set-ups, we investigated behavioural responses of a specialist cabbage butterfly (Pieris brassicae) and two of its parasitic wasps (Trichogramma brassicae and Cotesia glomerata) to volatiles of a wild crucifer (Brassica nigra) induced by oviposition of the specialist butterfly and an additional generalist moth (Mamestra brassicae). Gravid butterflies were repelled by volatiles from plants induced by cabbage white butterfly eggs, probably as a means of avoiding competition, whereas both parasitic wasp species were attracted. In contrast, volatiles from plants induced by eggs of the generalist moth did neither repel nor attract any of the tested community members. Analysis of the plant's volatile metabolomic profile by gas chromatography-mass spectrometry and the structure of the plant-egg interface by scanning electron microscopy confirmed that the plant responds differently to egg deposition by the two lepidopteran species. Our findings imply that prior to actual feeding damage, egg deposition can induce specific plant responses that significantly influence various members of higher trophic levels.

  16. The relationships between floral traits and specificity of pollination systems in three Scandinavian plant communities.

    PubMed

    Lázaro, Amparo; Hegland, Stein Joar; Totland, Orjan

    2008-08-01

    The pollination syndrome hypothesis has provided a major conceptual framework for how plants and pollinators interact. However, the assumption of specialization in pollination systems and the reliability of floral traits in predicting the main pollinators have been questioned recently. In addition, the relationship between ecological and evolutionary specialization in pollination interactions is still poorly understood. We used data of 62 plant species from three communities across southern Norway to test: (1) the relationships between floral traits and the identity of pollinators, (2) the association between floral traits (evolutionary specialization) and ecological generalization, and (3) the consistency of both relationships across communities. Floral traits significantly affected the identity of pollinators in the three communities in a way consistent with the predictions derived from the pollination syndrome concept. However, hover flies and butterflies visited flowers with different shapes in different communities, which we mainly attribute to among-community variation in pollinator assemblages. Interestingly, ecological generalization depended more on the community-context (i.e. the plant and pollinator assemblages in the communities) than on specific floral traits. While open yellow and white flowers were the most generalist in two communities, they were the most specialist in the alpine community. Our results warn against the use of single measures of ecological generalization to question the pollination syndrome concept, and highlight the importance of community comparisons to assess the pollination syndromes, and to understand the relationships between ecological and evolutionary specialization in plant-pollinator interactions.

  17. Soil nutrients trump intraspecific effects on understory plant communities.

    PubMed

    Crutsinger, Gregory M; Carter, Benjamin E; Rudgers, Jennifer A

    2013-12-01

    Understanding the links between intraspecific genetic variation and patterns of diversity in associated communities has been the primary focus of community genetics or 'genes-to-ecosystem' research in ecology. While other ecological factors, such as the abiotic environment, have well-documented influences on communities, the relative contributions of genetic variation versus the environment to species interactions remains poorly explored. In this study, we use a common garden experiment to study a coastal dune plant community dominated by the shrub, Baccharis pilularis, which displays a morphological dimorphism in plant architecture. We found the differences in the understory plant community between erect and prostrate morphs of Baccharis to be statistically significant, but small relative to the impacts of nutrient additions (NPK and C additions), for the richness, cover, and biomass of the understory plant community. There were no significant interactions between Baccharis morphology and nutrient-addition treatments, suggesting the influence of nutrient addition was consistent between erect and prostrate morphs. Moreover, we found no difference in overall plant community composition between Baccharis morphs, while NPK additions led to shifts in understory community composition compared to unfertilized shrubs. In sum, our results indicate that nutrients are the more important factor governing understory plant community structure in a coastal dunes ecosystem followed by intraspecific variation in dominant shrub architecture. Our results address a growing call to understand the extended consequences of intraspecific variation across heterogeneous environments in terrestrial ecosystems.

  18. Landscape fragmentation affects responses of avian communities to climate change.

    PubMed

    Jarzyna, Marta A; Porter, William F; Maurer, Brian A; Zuckerberg, Benjamin; Finley, Andrew O

    2015-08-01

    Forecasting the consequences of climate change is contingent upon our understanding of the relationship between biodiversity patterns and climatic variability. While the impacts of climate change on individual species have been well-documented, there is a paucity of studies on climate-mediated changes in community dynamics. Our objectives were to investigate the relationship between temporal turnover in avian biodiversity and changes in climatic conditions and to assess the role of landscape fragmentation in affecting this relationship. We hypothesized that community turnover would be highest in regions experiencing the most pronounced changes in climate and that these patterns would be reduced in human-dominated landscapes. To test this hypothesis, we quantified temporal turnover in avian communities over a 20-year period using data from the New York State Breeding Atlases collected during 1980-1985 and 2000-2005. We applied Bayesian spatially varying intercept models to evaluate the relationship between temporal turnover and temporal trends in climatic conditions and landscape fragmentation. We found that models including interaction terms between climate change and landscape fragmentation were superior to models without the interaction terms, suggesting that the relationship between avian community turnover and changes in climatic conditions was affected by the level of landscape fragmentation. Specifically, we found weaker associations between temporal turnover and climatic change in regions with prevalent habitat fragmentation. We suggest that avian communities in fragmented landscapes are more robust to climate change than communities found in contiguous habitats because they are comprised of species with wider thermal niches and thus are less susceptible to shifts in climatic variability. We conclude that highly fragmented regions are likely to undergo less pronounced changes in composition and structure of faunal communities as a result of climate change

  19. Does distance from the sea affect a soil microarthropod community?

    NASA Astrophysics Data System (ADS)

    Wasserstrom, Haggai; Steinberger, Yosef

    2016-10-01

    Coastal sand dunes are dynamic ecosystems characterized by strong abiotic gradients from the seashore inland. Due to significant differences in the abiotic parameters in such an environment, there is great interest in biotic adaptation in these habitats. The aim of the present study, which was conducted in the northern Sharon sand-dune area of Israel, was to illustrate the spatial changes of a soil microarthropod community along a gradient from the seashore inland. Soil samples were collected from the 0-10 cm depth at five locations at different distances, from the seashore inland. Samples were taken from the bare open spaces during the wet winter and dry summer seasons. The soil microarthropod community exhibited dependence both on seasonality and sampling location across the gradient. The community was more abundant during the wet winter seasons, with an increasing trend from the shore inland, while during the dry summers, such a trend was not observed and community density was lower. The dominant groups within soil Acari were Prostigmata and Endeostigmata, groups known to have many representatives with adaptation to xeric or psammic environments. In addition, mite diversity tended to be higher at the more distant locations from the seashore, and lower at the closer locations, a trend that appeared only during the wet winters. This study demonstrated the heterogeneity of a soil microarthropod community in a coastal dune field in a Mediterranean ecosystem, indicating that the gradient abiotic parameters also affect the abundance and composition of a soil microarthropod community in sand dunes.

  20. The impact of herbivore–plant coevolution on plant community structure

    PubMed Central

    Becerra, Judith X.

    2007-01-01

    Coevolutionary theory proposes that the diversity of chemical structures found in plants is, in large part, the result of selection by herbivores. Because herbivores often feed on chemically similar plants, they should impose selective pressures on plants to diverge chemically or bias community assembly toward chemical divergence. Using a coevolved interaction between a group of chrysomelid beetles and their host plants, I tested whether coexisting plants of the Mexican tropical dry forest tend to be chemically more dissimilar than random. Results show that some of the communities are chemically overdispersed and that overdispersion is related to the tightness of the interaction between plants and herbivores and the spatial scale at which communities are measured. As coevolutionary specialization increases and spatial scale decreases, communities tend to be more chemically dissimilar. At fairly local scales and where herbivores have tight, one-to-one interactions with plants, communities have a strong pattern of chemical disparity. PMID:17456606

  1. Forest Management Intensity Affects Aquatic Communities in Artificial Tree Holes

    PubMed Central

    Petermann, Jana S.; Rohland, Anja; Sichardt, Nora; Lade, Peggy; Guidetti, Brenda; Weisser, Wolfgang W.; Gossner, Martin M.

    2016-01-01

    Forest management could potentially affect organisms in all forest habitats. However, aquatic communities in water-filled tree-holes may be especially sensitive because of small population sizes, the risk of drought and potential dispersal limitation. We set up artificial tree holes in forest stands subject to different management intensities in two regions in Germany and assessed the influence of local environmental properties (tree-hole opening type, tree diameter, water volume and water temperature) as well as regional drivers (forest management intensity, tree-hole density) on tree-hole insect communities (not considering other organisms such as nematodes or rotifers), detritus content, oxygen and nutrient concentrations. In addition, we compared data from artificial tree holes with data from natural tree holes in the same area to evaluate the methodological approach of using tree-hole analogues. We found that forest management had strong effects on communities in artificial tree holes in both regions and across the season. Abundance and species richness declined, community composition shifted and detritus content declined with increasing forest management intensity. Environmental variables, such as tree-hole density and tree diameter partly explained these changes. However, dispersal limitation, indicated by effects of tree-hole density, generally showed rather weak impacts on communities. Artificial tree holes had higher water temperatures (on average 2°C higher) and oxygen concentrations (on average 25% higher) than natural tree holes. The abundance of organisms was higher but species richness was lower in artificial tree holes. Community composition differed between artificial and natural tree holes. Negative management effects were detectable in both tree-hole systems, despite their abiotic and biotic differences. Our results indicate that forest management has substantial and pervasive effects on tree-hole communities and may alter their structure and

  2. Forest Management Intensity Affects Aquatic Communities in Artificial Tree Holes.

    PubMed

    Petermann, Jana S; Rohland, Anja; Sichardt, Nora; Lade, Peggy; Guidetti, Brenda; Weisser, Wolfgang W; Gossner, Martin M

    2016-01-01

    Forest management could potentially affect organisms in all forest habitats. However, aquatic communities in water-filled tree-holes may be especially sensitive because of small population sizes, the risk of drought and potential dispersal limitation. We set up artificial tree holes in forest stands subject to different management intensities in two regions in Germany and assessed the influence of local environmental properties (tree-hole opening type, tree diameter, water volume and water temperature) as well as regional drivers (forest management intensity, tree-hole density) on tree-hole insect communities (not considering other organisms such as nematodes or rotifers), detritus content, oxygen and nutrient concentrations. In addition, we compared data from artificial tree holes with data from natural tree holes in the same area to evaluate the methodological approach of using tree-hole analogues. We found that forest management had strong effects on communities in artificial tree holes in both regions and across the season. Abundance and species richness declined, community composition shifted and detritus content declined with increasing forest management intensity. Environmental variables, such as tree-hole density and tree diameter partly explained these changes. However, dispersal limitation, indicated by effects of tree-hole density, generally showed rather weak impacts on communities. Artificial tree holes had higher water temperatures (on average 2°C higher) and oxygen concentrations (on average 25% higher) than natural tree holes. The abundance of organisms was higher but species richness was lower in artificial tree holes. Community composition differed between artificial and natural tree holes. Negative management effects were detectable in both tree-hole systems, despite their abiotic and biotic differences. Our results indicate that forest management has substantial and pervasive effects on tree-hole communities and may alter their structure and

  3. Species area relationships in mediterranean-climate plant communities

    USGS Publications Warehouse

    Keeley, Jon E.; Fotheringham, C.J.

    2003-01-01

    Aim To determine the best-fit model of species–area relationships for Mediterranean-type plant communities and evaluate how community structure affects these species–area models.Location Data were collected from California shrublands and woodlands and compared with literature reports for other Mediterranean-climate regions.Methods The number of species was recorded from 1, 100 and 1000 m2 nested plots. Best fit to the power model or exponential model was determined by comparing adjusted r2 values from the least squares regression, pattern of residuals, homoscedasticity across scales, and semi-log slopes at 1–100 m2 and 100–1000 m2. Dominance–diversity curves were tested for fit to the lognormal model, MacArthur's broken stick model, and the geometric and harmonic series.Results Early successional Western Australia and California shrublands represented the extremes and provide an interesting contrast as the exponential model was the best fit for the former, and the power model for the latter, despite similar total species richness. We hypothesize that structural differences in these communities account for the different species–area curves and are tied to patterns of dominance, equitability and life form distribution. Dominance–diversity relationships for Western Australian heathlands exhibited a close fit to MacArthur's broken stick model, indicating more equitable distribution of species. In contrast, Californian shrublands, both postfire and mature stands, were best fit by the geometric model indicating strong dominance and many minor subordinate species. These regions differ in life form distribution, with annuals being a major component of diversity in early successional Californian shrublands although they are largely lacking in mature stands. Both young and old Australian heathlands are dominated by perennials, and annuals are largely absent. Inherent in all of these ecosystems is cyclical disequilibrium caused by periodic fires. The

  4. Changes in hardwood forest understory plant communities in response to European earthworm invasions.

    PubMed

    Hale, Cindy M; Frelich, Lee E; Reich, Peter B

    2006-07-01

    European earthworms are colonizing earthworm-free northern hardwood forests across North America. Leading edges of earthworm invasion provide an opportunity to investigate the response of understory plant communities to earthworm invasion and whether the species composition of the earthworm community influences that response. Four sugar maple-dominated forest sites with active earthworm invasions were identified in the Chippewa National Forest in north central Minnesota, USA. In each site, we established a 30 x 150 m sample grid that spanned a visible leading edge of earthworm invasion and sampled earthworm populations and understory vegetation over four years. Across leading edges of earthworm invasion, increasing total earthworm biomass was associated with decreasing diversity and abundance of herbaceous plants in two of four study sites, and the abundance and density of tree seedlings decreased in three of four study sites. Sample points with the most diverse earthworm species assemblage, independent of biomass, had the lowest plant diversity. Changes in understory plant community composition were most affected by increasing biomass of the earthworm species Lumbricus rubellus. Where L. rubellus was absent there was a diverse community of native herbaceous plants, but where L. rubellus biomass reached its maximum, the herbaceous-plant community was dominated by Carex pensylvanica and Arisaema triphyllum and, in some cases, was completely absent. Evidence from these forest sites suggests that earthworm invasion can lead to dramatic changes in the understory community and that the nature of these changes is influenced by the species composition of the invading earthworm community.

  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.

  6. Loving transgressions: Queer of color bodies, affective ties, transformative community.

    PubMed

    Carrillo Rowe, Aimee; Royster, Francesca T

    2016-09-12

    This introductory article considers the importance of queer woman of color theorizations of affect in thinking more fully the recent interdisciplinary turn to affect. The affective turn has vitally invited culture and feminist critics to interrogate emotion beyond the individual to examine the political and cultural production of emotion. Even as women of color are often associated with excessive affect, the theoretical contributions women of color make to the field of affect studies are often overlooked. Our introduction and this special issue more broadly examine how this solipsism shapes projects invested in critical knowledge production, as well as the stakes of centering a queer woman of color genealogy. For instance, we argue for the importance of retaining U.S. third-world feminist concepts-like interpellation, oppositional consciousness, and the generative force of negative affects-even as they fall out of favor within affect studies. Centering theory that emerges from the vexed spaces of queer women of color lived experiences generates a vital interdisciplinary conversation that contributes to the ongoing political task of mobilizing affect for social action as a critical praxis. In the articles that follow we see this critical praxis at work in the form of community organizing, music, poetry, and performance art.

  7. Opposing plant community responses to warming with and without herbivores

    PubMed Central

    Post, Eric; Pedersen, Christian

    2008-01-01

    If controls over primary productivity and plant community composition are mainly environmental, as opposed to biological, then global change may result in large-scale alterations in ecosystem structure and function. This view appears to be favored among investigations of plant biomass and community responses to experimental and observed warming. In far northern and arctic ecosystems, such studies predict increasing dominance of woody shrubs with future warming and emphasize the carbon (C)-sequestration potential and consequent atmospheric feedback potential of such responses. In contrast to previous studies, we incorporated natural herbivory by muskoxen and caribou into a 5-year experimental investigation of arctic plant community response to warming. In accordance with other studies, warming increased total community biomass by promoting growth of deciduous shrubs (dwarf birch and gray willow). However, muskoxen and caribou reduced total community biomass response, and responses of birch and willow, to warming by 19%, 46%, and 11%, respectively. Furthermore, under warming alone, the plant community shifted after 5 years away from graminoid-dominated toward dwarf birch-dominated. In contrast, where herbivores grazed, plant community composition on warmed plots did not differ from that on ambient plots after 5 years. These results highlight the potentially important and overlooked influences of vertebrate herbivores on plant community response to warming and emphasize that conservation and management of large herbivores may be an important component of mitigating ecosystem response to climate change. PMID:18719116

  8. Plant Volatiles Induced by Herbivore Egg Deposition Affect Insects of Different Trophic Levels

    PubMed Central

    Fatouros, Nina E.; Lucas-Barbosa, Dani; Weldegergis, Berhane T.; Pashalidou, Foteini G.; van Loon, Joop J. A.; Dicke, Marcel; Harvey, Jeffrey A.; Gols, Rieta; Huigens, Martinus E.

    2012-01-01

    Plants release volatiles induced by herbivore feeding that may affect the diversity and composition of plant-associated arthropod communities. However, the specificity and role of plant volatiles induced during the early phase of attack, i.e. egg deposition by herbivorous insects, and their consequences on insects of different trophic levels remain poorly explored. In olfactometer and wind tunnel set-ups, we investigated behavioural responses of a specialist cabbage butterfly (Pieris brassicae) and two of its parasitic wasps (Trichogramma brassicae and Cotesia glomerata) to volatiles of a wild crucifer (Brassica nigra) induced by oviposition of the specialist butterfly and an additional generalist moth (Mamestra brassicae). Gravid butterflies were repelled by volatiles from plants induced by cabbage white butterfly eggs, probably as a means of avoiding competition, whereas both parasitic wasp species were attracted. In contrast, volatiles from plants induced by eggs of the generalist moth did neither repel nor attract any of the tested community members. Analysis of the plant’s volatile metabolomic profile by gas chromatography-mass spectrometry and the structure of the plant-egg interface by scanning electron microscopy confirmed that the plant responds differently to egg deposition by the two lepidopteran species. Our findings imply that prior to actual feeding damage, egg deposition can induce specific plant responses that significantly influence various members of higher trophic levels. PMID:22912893

  9. Effects of plant genotype and growth stage on the structure of bacterial communities associated with potato (Solanum tuberosum L.).

    PubMed

    van Overbeek, Leo; van Elsas, Jan Dirk

    2008-05-01

    The effects of genotype, plant growth and experimental factors (soil and year) on potato-associated bacterial communities were studied. Cultivars Achirana Inta, Désirée, Merkur and transgenic Désirée line DL12 (containing T4 lysozyme gene) were assessed in two field experiments. Cross-comparisons between both experiments were made using Désirée plants. Culture-dependent and -independent approaches were used to demonstrate effects on total bacterial, actinobacterial and Pseudomonas communities in bulk and rhizosphere soils and endospheres. PCR-denaturing gradient gel electrophoresis fingerprints prepared with group-specific primers were analyzed using multivariate analyses and revealed that bacterial communities in Achirana Inta plants differed most from those of Désirée and Merkur. No significant effects were found between Désirée and DL12 lines. Plant growth stage strongly affected different plant-associated communities in both experiments. To investigate the effect of plant-associated communities on plant health, 800 isolates from rhizospheres and endospheres at the flowering stage were tested for suppression of Ralstonia solanacearum biovar 2 and/or Rhizoctonia solani AG3. A group of isolates closely resembling Lysobacter sp. dominated in young plants. Its prevalence was affected by plant growth stage and experiment rather than by plant genotype. It was concluded that plant growth stage overwhelmed any effect of plant genotype on the bacterial communities associated with potato.

  10. Plant domestication and the assembly of bacterial and fungal communities associated with strains of the common sunflower, Helianthus annuus.

    PubMed

    Leff, Jonathan W; Lynch, Ryan C; Kane, Nolan C; Fierer, Noah

    2017-04-01

    Root and rhizosphere microbial communities can affect plant health, but it remains undetermined how plant domestication may influence these bacterial and fungal communities. We grew 33 sunflower (Helianthus annuus) strains (n = 5) that varied in their extent of domestication and assessed rhizosphere and root endosphere bacterial and fungal communities. We also assessed fungal communities in the sunflower seeds to investigate the degree to which root and rhizosphere communities were influenced by vertical transmission of the microbiome through seeds. Neither root nor rhizosphere bacterial communities were affected by the extent of sunflower domestication, but domestication did affect the composition of rhizosphere fungal communities. In particular, more modern sunflower strains had lower relative abundances of putative fungal pathogens. Seed-associated fungal communities strongly differed across strains, but several lines of evidence suggest that there is minimal vertical transmission of fungi from seeds to the adult plants. Our results indicate that plant-associated fungal communities are more strongly influenced by host genetic factors and plant breeding than bacterial communities, a finding that could influence strategies for optimizing microbial communities to improve crop yields.

  11. Absence of snow cover reduces understory plant cover and alters plant community composition in boreal forests.

    PubMed

    Kreyling, Juergen; Haei, Mahsa; Laudon, Hjalmar

    2012-02-01

    Snow regimes affect biogeochemistry of boreal ecosystems and are altered by climate change. The effects on plant communities, however, are largely unexplored despite their influence on relevant processes. Here, the impact of snow cover on understory community composition and below-ground production in a boreal Picea abies forest was investigated using a long-term (8-year) snow cover manipulation experiment consisting of the treatments: snow removal, increased insulation (styrofoam pellets), and control. The snow removal treatment caused longer (118 vs. 57 days) and deeper soil frost (mean minimum temperature -5.5 vs. -2.2°C) at 10 cm soil depth in comparison to control. Understory species composition was strongly altered by the snow cover manipulations; vegetation cover declined by more than 50% in the snow removal treatment. In particular, the dominant dwarf shrub Vaccinium myrtillus (-82%) and the most abundant mosses Pleurozium schreberi (-74%) and Dicranum scoparium (-60%) declined strongly. The C:N ratio in V. myrtillus leaves and plant available N in the soil indicated no altered nitrogen nutrition. Fine-root biomass in summer, however, was negatively affected by the reduced snow cover (-50%). Observed effects are attributed to direct frost damage of roots and/ or shoots. Besides the obvious relevance of winter processes on plant ecology and distribution, we propose that shifts in the vegetation caused by frost damage may be an important driver of the reported alterations in biogeochemistry in response to altered snow cover. Understory plant performance clearly needs to be considered in the biogeochemistry of boreal systems in the face of climate change.

  12. Impacts of Grazing Intensity and Plant Community Composition on Soil Bacterial Community Diversity in a Steppe Grassland.

    PubMed

    Qu, Tong-Bao; Du, Wei-Chao; Yuan, Xia; Yang, Zhi-Ming; Liu, Dong-Bo; Wang, De-Li; Yu, Li-Jun

    2016-01-01

    Soil bacteria play a key role in the ecological and evolutionary responses of agricultural ecosystems. Domestic herbivore grazing is known to influence soil bacterial community. However, the effects of grazing and its major driving factors on soil bacterial community remain unknown for different plant community compositions under increasing grazing intensity. Thus, to investigate soil bacterial community diversity under five plant community compositions (Grass; Leymus chinensis; Forb; L. chinensis & Forb; and Legume), we performed a four-year field experiment with different grazing intensity treatments (no grazing; light grazing, 4 sheep·ha-1; and heavy grazing, 6 sheep·ha-1) in a grassland in China. Total DNA was obtained from soil samples collected from the plots in August, and polymerase chain reaction (PCR) analysis and denaturing gradient gel electrophoresis (DGGE) fingerprinting were used to investigate soil bacterial community. The results showed that light grazing significantly increased indices of soil bacterial community diversity for the Forb and Legume groups but not the Grass and L. chinensis groups. Heavy grazing significantly reduced these soil bacterial diversity indices, except for the Pielou evenness index in the Legume group. Further analyses revealed that the soil N/P ratio, electrical conductivity (EC), total nitrogen (TN) and pH were the major environmental factors affecting the soil bacterial community. Our study suggests that the soil bacterial community diversity was influenced by grazing intensity and plant community composition in a meadow steppe. The present study provides a baseline assessment of the soil bacterial community diversity in a temperate meadow steppe.

  13. Impacts of Grazing Intensity and Plant Community Composition on Soil Bacterial Community Diversity in a Steppe Grassland

    PubMed Central

    Qu, Tong-bao; Du, Wei-chao; Yuan, Xia; Yang, Zhi-ming; Liu, Dong-bo; Wang, De-li; Yu, Li-jun

    2016-01-01

    Soil bacteria play a key role in the ecological and evolutionary responses of agricultural ecosystems. Domestic herbivore grazing is known to influence soil bacterial community. However, the effects of grazing and its major driving factors on soil bacterial community remain unknown for different plant community compositions under increasing grazing intensity. Thus, to investigate soil bacterial community diversity under five plant community compositions (Grass; Leymus chinensis; Forb; L. chinensis & Forb; and Legume), we performed a four-year field experiment with different grazing intensity treatments (no grazing; light grazing, 4 sheep·ha−1; and heavy grazing, 6 sheep·ha−1) in a grassland in China. Total DNA was obtained from soil samples collected from the plots in August, and polymerase chain reaction (PCR) analysis and denaturing gradient gel electrophoresis (DGGE) fingerprinting were used to investigate soil bacterial community. The results showed that light grazing significantly increased indices of soil bacterial community diversity for the Forb and Legume groups but not the Grass and L. chinensis groups. Heavy grazing significantly reduced these soil bacterial diversity indices, except for the Pielou evenness index in the Legume group. Further analyses revealed that the soil N/P ratio, electrical conductivity (EC), total nitrogen (TN) and pH were the major environmental factors affecting the soil bacterial community. Our study suggests that the soil bacterial community diversity was influenced by grazing intensity and plant community composition in a meadow steppe. The present study provides a baseline assessment of the soil bacterial community diversity in a temperate meadow steppe. PMID:27467221

  14. Strategic rehabilitation of the earthquake affected microhydropower plants in Nepal

    NASA Astrophysics Data System (ADS)

    Baidar, B.; Koirala, R.; Neopane, H. P.; Shrestha, M. V.; Thapa, B.

    2016-11-01

    Most people in the rural areas of Nepal rely on Micro-hydro Power Plants (MHPs) for their energy sources. With around four decade experiences in design and development of MHPs, Nepalese techno-entrepreneurs have gained wider reputation in the South Asian region and the beyond. However with the lack of competences in developing Francis turbines, majority of the MHPs are equipped with either Pelton of Cross Flow turbine, even though Francis units are suitable. With the devastating earthquake of a 7.6 magnitude that struck in the Gorkha district on Saturday, 25 April 2015, about 76 km northwest of the capital city Kathmandu, and the aftershocks followed claimed more than 8000 lives. It did not leave hydropower plants either. Many big plants have been affected and hundreds of MHPs were damaged, needing short to long term rehabilitation. The preliminary assessment of the 61 affected MHPs in the 6 earthquake affected districts shows more than 50% sites are suitable for Francis turbine. Hence the strategic rehabilitation plan has been developed in the present paper for the affected plants considering issues like geographical shift, dislocation of people and also with the focus on replacing the old turbine with Francis turbine in the suitable sites. The similar strategy can also be implemented in other developing countries with such situations.

  15. Secondary bacterial symbiont community in aphids responds to plant diversity.

    PubMed

    Zytynska, Sharon E; Meyer, Sebastian T; Sturm, Sarah; Ullmann, Wiebke; Mehrparvar, Mohsen; Weisser, Wolfgang W

    2016-03-01

    Biodiversity is important for ecosystem functioning and biotic interactions. In experimental grasslands, increasing plant species richness is known to increase the diversity of associated herbivores and their predators. If these interactions can also involve endosymbionts that reside within a plant or animal host is currently unknown. In plant-feeding aphids, secondary bacterial symbionts can have strong fitness effects on the host, e.g. resistance to natural enemies or fungal pathogens. We examined the secondary symbiont community in three species of aphid, each feeding on a unique host plant across experimental plots that varied in plant species richness. Aphids were collected in May and June, and the symbiont community identified using species-specific PCR assays. Aphis fabae aphids were found to host six different symbiont species with individual aphids co-hosting up to four symbionts. Uroleucon jaceae and Macrosiphum rosae hosted two and three symbiont species, respectively. We found that, at the aphid population level, increasing plant species richness increased the diversity of the aphid symbiont community, whereas at the individual aphid level, the opposite was found. These effects are potentially driven by varying selective pressures across different plant communities of varying diversities, mediated by defensive protection responses and a changing cost-benefit trade-off to the aphid for hosting multiple secondary symbionts. Our work extends documented effects of plant diversity beyond visible biotic interactions to changes in endosymbiont communities, with potentially far-reaching consequences to related ecosystem processes.

  16. How much biomass do plant communities pack per unit volume?

    PubMed Central

    Rheault, Guillaume; Bonin, Laurianne; Roca, Irene Torrecilla; Martin, Charles A.; Desrochers, Louis; Seiferling, Ian

    2015-01-01

    Aboveground production in terrestrial plant communities is commonly expressed in amount of carbon, or biomass, per unit surface. Alternatively, expressing production per unit volume allows the comparison of communities by their fundamental capacities in packing carbon. In this work we reanalyzed published data from more than 900 plant communities across nine ecosystems to show that standing dry biomass per unit volume (biomass packing) consistently averages around 1 kg/m3 and rarely exceeds 5 kg/m3 across ecosystem types. Furthermore, we examined how empirical relationships between aboveground production and plant species richness are modified when standing biomass is expressed per unit volume rather than surface. We propose that biomass packing emphasizes species coexistence mechanisms and may be an indicator of resource use efficiency in plant communities. PMID:25802814

  17. Local Factors Determine Plant Community Structure on Closely Neighbored Islands

    PubMed Central

    Lu, Jianbo; Jiang, Lin; Yu, Lin; Sun, Que

    2011-01-01

    Despite the recent popularity of the metacommunity concept, ecologists have not evaluated the applicability of different metacommunity frameworks to insular organisms. We surveyed 50 closely spaced islands in the Thousand-Island Lake of China to examine the role of local (environmental) and regional (dispersal) factors in structuring woody plant assemblages (tree and shrub species) on these islands. By partitioning the variation in plant community structure into local and regional causes, we showed that local environmental conditions, specifically island morphometric characteristics, accounted for the majority of the variation in plant community structure among the studied islands. Spatial variables, representing the potential importance of species dispersal, explained little variation. We conclude that one metacommunity framework–species sorting–best characterizes these plant communities. This result reinforces the idea that the traditional approach of emphasizing the local perspective when studying ecological communities continues to hold its value. PMID:21572960

  18. Postfire seeding and plant community recovery in the Great Basin

    Technology Transfer Automated Retrieval System (TEKTRAN)

    As wildland fire frequency increases around the globe, increased understanding of plant community recovery in burned landscapes is needed to improve effectiveness of rehabilitation efforts. We measured establishment of seeded species, colonization of Bromus tectorum L. (cheatgrass), and recovery of ...

  19. Plant toxicity, adaptive herbivory, and plant community dynamics

    USGS Publications Warehouse

    Feng, Z.; Liu, R.; DeAngelis, D.L.; Bryant, J.P.; Kielland, K.; Stuart, Chapin F.; Swihart, R.K.

    2009-01-01

    We model effects of interspecific plant competition, herbivory, and a plant's toxic defenses against herbivores on vegetation dynamics. The model predicts that, when a generalist herbivore feeds in the absence of plant toxins, adaptive foraging generally increases the probability of coexistence of plant species populations, because the herbivore switches more of its effort to whichever plant species is more common and accessible. In contrast, toxin-determined selective herbivory can drive plant succession toward dominance by the more toxic species, as previously documented in boreal forests and prairies. When the toxin concentrations in different plant species are similar, but species have different toxins with nonadditive effects, herbivores tend to diversify foraging efforts to avoid high intakes of any one toxin. This diversification leads the herbivore to focus more feeding on the less common plant species. Thus, uncommon plants may experience depensatory mortality from herbivory, reducing local species diversity. The depensatory effect of herbivory may inhibit the invasion of other plant species that are more palatable or have different toxins. These predictions were tested and confirmed in the Alaskan boreal forest. ?? 2009 Springer Science+Business Media, LLC.

  20. Impact of plant functional group, plant species, and sampling time on the composition of nirK-type denitrifier communities in soil.

    PubMed

    Bremer, Christina; Braker, Gesche; Matthies, Diethart; Reuter, Andreas; Engels, Christof; Conrad, Ralf

    2007-11-01

    We studied the influence of eight nonleguminous grassland plant species belonging to two functional groups (grasses and forbs) on the composition of soil denitrifier communities in experimental microcosms over two consecutive years. Denitrifier community composition was analyzed by terminal restriction fragment length polymorphism (T-RFLP) of PCR-amplified nirK gene fragments coding for the copper-containing nitrite reductase. The impact of experimental factors (plant functional group, plant species, sampling time, and interactions between them) on the structure of soil denitrifier communities (i.e., T-RFLP patterns) was analyzed by canonical correspondence analysis. While the functional group of a plant did not affect nirK-type denitrifier communities, plant species identity did influence their composition. This effect changed with sampling time, indicating community changes due to seasonal conditions and a development of the plants in the microcosms. Differences in total soil nitrogen and carbon, soil pH, and root biomass were observed at the end of the experiment. However, statistical analysis revealed that the plants affected the nirK-type denitrifier community composition directly, e.g., through root exudates. Assignment of abundant T-RFs to cloned nirK sequences from the soil and subsequent phylogenetic analysis indicated a dominance of yet-unknown nirK genotypes and of genes related to nirK from denitrifiers of the order Rhizobiales. In conclusion, individual species of nonleguminous plants directly influenced the composition of denitrifier communities in soil, but environmental conditions had additional significant effects.

  1. Effects of migratory geese on plant communities of an Alaskan salt marsh

    USGS Publications Warehouse

    Zacheis, Amy B.; Hupp, J.W.; Ruess, Roger W.

    2001-01-01

    pressure can alter plant communities and affect forage availability.

  2. Plant community composition promotes multiple ecosystem functions in grassland at low and high soil fertility

    NASA Astrophysics Data System (ADS)

    de Deyn, Gerlinde; Ostle, Nick; Bardgett, Richard

    2010-05-01

    It is well known that plant species richness can enhance primary productivity through complementarity in resource use by component plant species. Fewer studies have explored the role of plant species diversity and composition for the delivery of other ecosystem services than primary production and its dependency on resource availability. In this study we investigated how carbon (C) and nitrogen (N) stocks in vegetation, soil and soil microbes, the loss of C and N from soil through leaching and ecosystem exchange rates of CO2 are affected by the composition and richness of grassland plant communities and soil fertility. We used two soils of contrasting fertility in which we planted plant communities using a pool of six plant species from one of three functional groups (legumes, forbs and C3 grasses). The levels of plant species richness were one, two, three or six species and were composed of one, two or three functional groups. Soil fertility stimulated pools of C and N in shoots and roots, and the soil microbial biomass, but also increased significantly with increased plant functional group and plant species richness. Moreover, plant diversity suppressed N and water loss via soil leaching. We also found changes in the C and N content in soil, but these were not related to the richness of plant species or functional groups. The changes in soil were rather specifically due to the abundance of the legumes. The leaching of water and N was related negative to plant species richness but also specifically to the abundance of the forb species. Our findings show that the relation between plant community composition and storage of C and N in vegetation is not directly reflected in the changes in C and N storage in soil. These soil based storage functions, and the leaching of N from soil, appeared to be most strongly related to different key plant species. Together these results indicate that the maintenance of plant diversity is important to sustain the multiple functions

  3. Influence of Plant Community Composition on Biomass Production in Planted Grasslands

    PubMed Central

    Henschell, Max A.; Webster, Christopher R.; Flaspohler, David J.; Fortin, Chad R.

    2015-01-01

    United States energy policy mandates increased use of renewable fuels. Restoring grasslands could contribute to a portion of this requirement through biomass harvest for bioenergy use. We investigated which plant community characteristics are associated with differences in biomass yield from a range of realistic native prairie plantings (n = 11; i.e., conservation planting, restoration, and wildlife cover). Our primary goal was to understand whether patterns in plant community composition and the Floristic Quality Index (FQI) were related to productivity as evidenced by dormant season biomass yield. FQI is an objective measure of how closely a plant community represents that of a pre-European settlement community. Our research was conducted in planted fields of native tallgrass prairie species, and provided a gradient in floristic quality index, species richness, species diversity, and species evenness in south-central Wisconsin during 2008 and 2009. We used a network of 15 randomly located 1 m2 plots within each field to characterize the plant community and estimate biomass yield by clipping the plots at the end of each growing season. While plant community composition and diversity varied significantly by planting type, biomass yield did not vary significantly among planting types (ANOVA; P >0.05). Biomass yield was positively correlated with plant community evenness, richness, C4 grass cover, and floristic quality index, but negatively correlated with plant species diversity in our multi-season multiple linear mixed effects models. Concordantly, plots with biomass yield in the lowest quartile (biomass yield < 3500 kh/ha) had 8% lower plant community evenness and 9% lower FQI scores than those in the upper quartile (biomass yield > 5800 kh/ha). Our results suggest that promoting the establishment of fields with high species evenness and floristic quality may increase biomass yield, while simultaneously supporting biodiversity. PMID:26018412

  4. Plant community associations of the invasive thistles

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In order to combat the growing problems associated with biological invasions, many researchers have focused on identifying which communities are most vulnerable to invasion by exotic species. Once established, invasive species can significantly change the composition of the communities that they inv...

  5. Shifts in rhizoplane communities of aquatic plants after cadmium exposure.

    PubMed

    Stout, Lisa M; Nüsslein, Klaus

    2005-05-01

    In this study we present the comparative molecular analysis of bacterial communities of the aquatic plant Lemna minor from a contaminated site (RCP) and from a laboratory culture (EPA), as well as each of these with the addition of cadmium. Plants were identified as L. minor by analysis of the rpl16 chloroplast region. Comparative bacterial community studies were based on the analyses of 16S rRNA clone libraries, each containing about 100 clones from the root surfaces of plants. Bacterial communities were compared at three phylogenetic levels of resolution. At the level of bacterial divisions, differences in diversity index scores between treatments, with and without cadmium within the same plant type (EPA or RCP), were small, indicating that cadmium had little effect. When we compared genera within the most dominant group, the beta-proteobacteria, differences between unamended and cadmium-amended libraries were much larger. Bacterial diversity increased upon cadmium addition for both EPA and RCP libraries. Analyses of diversity at the phylotype level showed parallel shifts to more even communities upon cadmium addition; that is, percentage changes in diversity indices due to cadmium addition were the same for either plant type, indicating that contamination history might be independent of disturbance-induced diversity shifts. At finer phylogenetic levels of resolution, the effects of cadmium addition on bacterial communities were very noticeable. This study is a first step in understanding the role of aquatic plant-associated microbial communities in phytoremediation of heavy metals.

  6. Structure and composition of oligohaline marsh plant communities exposed to salinity pulses

    USGS Publications Warehouse

    Howard, R.J.; Mendelssohn, I.A.

    2000-01-01

    The response of two oligohaline marsh macrophyte communities to pulses of increased salinity was studied over a single growing season in a greenhouse experiment. The plant communities were allowed a recovery period in freshwater following the pulse events. The experimental treatments included: (1) salinity influx rate (rate of salinity increase from 0 to 12 gl-1); (2) duration of exposure to elevated salinity; and (3) water depth. The communities both included Sagittaria lancifolia L.; the codominant species were Eleocharis palustris (L.) Roemer and J.A. Schultes in community 1 and Schoenoplectus americanus (Pers.) Volk. ex Schinz and R. Keller in community 2. Effects of the treatments on sediment chemical characteristics (salinity, pH, redox potential, and sulfide and ammonium concentrations) and plant community attributes (aboveground and belowground biomass, stem density, leaf tissue nutrients, and species richness) were examined. The treatment effects often interacted to influence sediment and plant communities characteristics following recovery in fresh water. Salinity influx rate per se, however, had little effect on the abiotic or biotic response variables; significant influx effects were found when the 0 gl-1 (zero influx) treatment was compared to the 12 gl-1 treatments, regardless of the rate salinity was raised. A salinity level of 12 gl-1 had negative effects on plant community structure and composition; these effects were usually associated with 3 months of salinity exposure. Water depth often interacted with exposure duration, but increased water depth did independently decrease the values of some community response measures. Community 1 was affected more than community 2 in the most extreme salinity treatment (3 months exposure/15-cm water depth). Although species richness in both communities was reduced, structural changes were more dramatic in community 1. Biomass and stem density were reduced in community 1 overall and in both dominant species

  7. Zinc stress affects ionome and metabolome in tea plants.

    PubMed

    Zhang, Yinfei; Wang, Yu; Ding, Zhaotang; Wang, Hui; Song, Lubin; Jia, Sisi; Ma, Dexin

    2017-02-01

    The research of physiological responses to Zn stress in plants has been extensively studied. However, the ionomics and metabolomics responses of plants to Zn stress remain largely unknown. In present study, the nutrient elements were identified involved in ion homeostasis and metabolomics changes related to Zn deficiency or excess in tea plants. Nutrient element analysis demonstrated that the concentrations of Zn affected the ion-uptake in roots and the nutrient element transportation to leaves, leading to the different distribution of P, S, Al, Ca, Fe and Cu in the tea leaves or roots. Metabolomics analysis revealed that Zn deficiency or excess differentially influenced the metabolic pathways in the tea leaves. More specifically, Zn deficiency affected the metabolism of carbohydrates, and Zn excess affected flavonoids metabolism. Additionally, the results showed that both Zn deficiency and Zn excess led to reduced nicotinamide levels, which speeded up NAD(+) degradation and thus reduced energy metabolism. Furthermore, element-metabolite correlation analysis illustrated that Zn contents in the tea leaves were positively correlated with organic acids, nitrogenous metabolites and some carbohydrate metabolites, and negatively correlated with the metabolites involved in secondary metabolism and some other carbohydrate metabolites. Meanwhile, metabolite-metabolite correlation analysis demonstrated that organic acids, sugars, amino acids and flavonoids played dominant roles in the regulation of the tea leaf metabolism under Zn stress. Therefore, the conclusion should be drawn that the tea plants responded to Zn stress by coordinating ion-uptake and regulation of metabolism of carbohydrates, nitrogenous metabolites, and flavonoids.

  8. Herbivory and dominance shifts among exotic and congeneric native plant species during plant community establishment.

    PubMed

    Engelkes, Tim; Meisner, Annelein; Morriën, Elly; Kostenko, Olga; Van der Putten, Wim H; Macel, Mirka

    2016-02-01

    Invasive exotic plant species often have fewer natural enemies and suffer less damage from herbivores in their new range than genetically or functionally related species that are native to that area. Although we might expect that having fewer enemies would promote the invasiveness of the introduced exotic plant species due to reduced enemy exposure, few studies have actually analyzed the ecological consequences of this situation in the field. Here, we examined how exposure to aboveground herbivores influences shifts in dominance among exotic and phylogenetically related native plant species in a riparian ecosystem during early establishment of invaded communities. We planted ten plant communities each consisting of three individuals of each of six exotic plant species as well as six phylogenetically related natives. Exotic plant species were selected based on a rapid recent increase in regional abundance, the presence of a congeneric native species, and their co-occurrence in the riparian ecosystem. All plant communities were covered by tents with insect mesh. Five tents were open on the leeward side to allow herbivory. The other five tents were completely closed in order to exclude insects and vertebrates. Herbivory reduced aboveground biomass by half and influenced which of the plant species dominated the establishing communities. Exposure to herbivory did not reduce the total biomass of natives more than that of exotics, so aboveground herbivory did not selectively enhance exotics during this early stage of plant community development. Effects of herbivores on plant biomass depended on plant species or genus but not on plant status (i.e., exotic vs native). Thus, aboveground herbivory did not promote the dominance of exotic plant species during early establishment of the phylogenetically balanced plant communities.

  9. AQUATIC PLANT COMMUNITIES FOR IMPACT MONITORING AND ASSESSMENT

    EPA Science Inventory

    The studies revewed here suggest that both structural and functional assessments of aquatic plant communities are valuable tools in the determination of environmental impacts and water quality. I am not suggesting that aquatic plants be used in lieu of macronivertebrates or fish ...

  10. Linking Wildfire and Climate as Drivers of Plant Species and Community-level Change

    NASA Astrophysics Data System (ADS)

    Newingham, B. A.; Hudak, A. T.; Bright, B. C.

    2015-12-01

    Plant species distributions and community shifts after fire are affected by burn severity, elevation, aspect, and climate. However, little empirical data exists on long-term (decadal) recovery after fire across these interacting factors, limiting understanding of fire regime characteristics and climate in post-fire community trajectories. We examined plant species and community responses a decade after fire across five fires in ponderosa pine, dry mixed coniferous, and moist mixed coniferous forests across the western USA. Using field data, we determined changes in plant communities one and ten years post-fire across gradients of burn severity, elevation, and aspect. Existing published work has shown that plant species distributions can be accurately predicted from physiologically relevant climate variables using non-parametric Random Forests models; such models have also been linked to projected climate profiles in 2030, 2060, and 2090 generated from three commonly used general circulation models (GCMs). We explore the possibility that fire and climate are coupled drivers affecting plant species distributions. Climate change may not manifest as a slow shift in plant species distributions, but as sudden, localized events tied to changing fire and other disturbance regimes.

  11. Purple Pitcher Plant (Sarracenia rosea) Dieback and Partial Community Disassembly following Experimental Storm Surge in a Coastal Pitcher Plant Bog

    PubMed Central

    Abbott, Matthew J.; Battaglia, Loretta L.

    2015-01-01

    Sea-level rise and frequent intense hurricanes associated with climate change will result in recurrent flooding of inland systems such as Gulf Coastal pitcher plant bogs by storm surges. These surges can transport salt water and sediment to freshwater bogs, greatly affecting their biological integrity. Purple pitcher plants (Sarracenia rosea) are Gulf Coast pitcher plant bog inhabitants that could be at a disadvantage under this scenario because their pitcher morphology may leave them prone to collection of saline water and sediment after a surge. We investigated the effects of storm surge water salinity and sediment type on S. rosea vitality, plant community structure, and bog soil-water conductivity. Plots (containing ≥1 ramet of S. rosea) were experimentally flooded with fresh or saline water crossed with one of three sediment types (local, foreign, or no sediment). There were no treatment effects on soil-water conductivity; nevertheless, direct exposure to saline water resulted in significantly lower S. rosea cover until the following season when a prescribed fire and regional drought contributed to the decline of all the S. rosea to near zero percent cover. There were also significant differences in plant community structure between treatments over time, reflecting how numerous species increased in abundance and a few species decreased in abundance. However, in contrast to S. rosea, most of the other species in the community appeared resilient to the effects of storm surge. Thus, although the community may be somewhat affected by storm surge, those few species that are particularly sensitive to the storm surge disturbance will likely drop out of the community and be replaced by more resilient species. Depending on the longevity of these biological legacies, Gulf Coastal pitcher plant bogs may be incapable of fully recovering if they become exposed to storm surge more frequently due to climate change. PMID:25874369

  12. Purple pitcher plant (Sarracenia rosea) Dieback and partial community disassembly following experimental storm surge in a coastal pitcher plant bog.

    PubMed

    Abbott, Matthew J; Battaglia, Loretta L

    2015-01-01

    Sea-level rise and frequent intense hurricanes associated with climate change will result in recurrent flooding of inland systems such as Gulf Coastal pitcher plant bogs by storm surges. These surges can transport salt water and sediment to freshwater bogs, greatly affecting their biological integrity. Purple pitcher plants (Sarracenia rosea) are Gulf Coast pitcher plant bog inhabitants that could be at a disadvantage under this scenario because their pitcher morphology may leave them prone to collection of saline water and sediment after a surge. We investigated the effects of storm surge water salinity and sediment type on S. rosea vitality, plant community structure, and bog soil-water conductivity. Plots (containing ≥1 ramet of S. rosea) were experimentally flooded with fresh or saline water crossed with one of three sediment types (local, foreign, or no sediment). There were no treatment effects on soil-water conductivity; nevertheless, direct exposure to saline water resulted in significantly lower S. rosea cover until the following season when a prescribed fire and regional drought contributed to the decline of all the S. rosea to near zero percent cover. There were also significant differences in plant community structure between treatments over time, reflecting how numerous species increased in abundance and a few species decreased in abundance. However, in contrast to S. rosea, most of the other species in the community appeared resilient to the effects of storm surge. Thus, although the community may be somewhat affected by storm surge, those few species that are particularly sensitive to the storm surge disturbance will likely drop out of the community and be replaced by more resilient species. Depending on the longevity of these biological legacies, Gulf Coastal pitcher plant bogs may be incapable of fully recovering if they become exposed to storm surge more frequently due to climate change.

  13. A proposed aquatic plant community biotic index for Wisconsin lakes

    USGS Publications Warehouse

    Nichols, S.; Weber, S.; Shaw, B.

    2000-01-01

    The Aquatic Macrophyte Community Index (AMCI) is a multipurpose tool developed to assess the biological quality of aquatic plant communities in lakes. It can be used to specifically analyze aquatic plant communities or as part of a multimetric system to assess overall lake quality for regulatory, planning, management, educational, or research purposes. The components of the index are maximum depth of plant growth; percentage of the littoral zone vegetated; Simpson's diversity index; the relative frequencies of submersed, sensitive, and exotic species; and taxa number. Each parameter was scaled based on data distributions from a statewide database, and scaled values were totaled for the AMCI value. AMCI values were grouped and tested by ecoregion and lake type (natural lakes and impoundments) to define quality on a regional basis. This analysis suggested that aquatic plant communities are divided into four groups: (1) Northern Lakes and Forests lakes and impoundments, (2) North-Central Hardwood Forests lakes and impoundments, (3) Southeastern Wisconsin Till Plains lakes, and (4) Southeastern Wisconsin Till Plains impoundments, Driftless Area Lakes, and Mississippi River Backwater lakes. AMCI values decline from group 1 to group 4 and reflect general water quality and human use trends in Wisconsin. The upper quartile of AMCI values in any region are the highest quality or benchmark plant communities. The interquartile range consists of normally impacted communities for the region and the lower quartile contains severely impacted or degraded plant communities. When AMCI values were applied to case studies, the values reflected known impacts to the lakes. However, quality criteria cannot be used uncritically, especially in lakes that initially have low nutrient levels.The Aquatic Macrophyte Community Index (AMCI) is a multipurpose tool developed to assess the biological quality of aquatic plant communities in lakes. It can be used to specifically analyze aquatic plant

  14. Phylogenetic composition of host plant communities drives plant-herbivore food web structure.

    PubMed

    Volf, Martin; Pyszko, Petr; Abe, Tomokazu; Libra, Martin; Kotásková, Nela; Šigut, Martin; Kumar, Rajesh; Kaman, Ondřej; Butterill, Philip T; Šipoš, Jan; Abe, Haruka; Fukushima, Hiroaki; Drozd, Pavel; Kamata, Naoto; Murakami, Masashi; Novotny, Vojtech

    2017-02-01

    Insects tend to feed on related hosts. The phylogenetic composition of host plant communities thus plays a prominent role in determining insect specialization, food web structure, and diversity. Previous studies showed a high preference of insect herbivores for congeneric and confamilial hosts suggesting that some levels of host plant relationships may play more prominent role that others. We aim to quantify the effects of host phylogeny on the structure of quantitative plant-herbivore food webs. Further, we identify specific patterns in three insect guilds with different life histories and discuss the role of host plant phylogeny in maintaining their diversity. We studied herbivore assemblages in three temperate forests in Japan and the Czech Republic. Sampling from a canopy crane, a cherry picker and felled trees allowed a complete census of plant-herbivore interactions within three 0·1 ha plots for leaf chewing larvae, miners, and gallers. We analyzed the effects of host phylogeny by comparing the observed food webs with randomized models of host selection. Larval leaf chewers exhibited high generality at all three sites, whereas gallers and miners were almost exclusively monophagous. Leaf chewer generality dropped rapidly when older host lineages (5-80 myr) were collated into a single lineage but only decreased slightly when the most closely related congeneric hosts were collated. This shows that leaf chewer generality has been maintained by feeding on confamilial hosts while only a few herbivores were shared between more distant plant lineages and, surprisingly, between some congeneric hosts. In contrast, miner and galler generality was maintained mainly by the terminal nodes of the host phylogeny and dropped immediately after collating congeneric hosts into single lineages. We show that not all levels of host plant phylogeny are equal in their effect on structuring plant-herbivore food webs. In the case of generalist guilds, it is the phylogeny of deeper

  15. Host plant species determines symbiotic bacterial community mediating suppression of plant defenses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Herbivore associated bacteria are vital mediators of plant and insect interactions. Host plants play an important role in shaping the gut bacterial community of insects. Colorado potato beetles (CPB; Leptinotarsa decemlineata) use several Solanum plants as hosts in their natural environment. We prev...

  16. Plant community diversity and native plant abundance decline with increasing abundance of an exotic annual grass

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Exotic plants are generally considered a serious problem in wildlands around the globe. However, some argue that the impacts of exotic plants have been exaggerated and that biodiversity and other important plant community characteristics are commonly improved with invasion. Thus, disagreement exis...

  17. ADP1 Affects Plant Architecture by Regulating Local Auxin Biosynthesis

    PubMed Central

    Li, Shibai; Qin, Genji; Novák, Ondřej; Pěnčík, Aleš; Ljung, Karin; Aoyama, Takashi; Liu, Jingjing; Murphy, Angus; Gu, Hongya; Tsuge, Tomohiko; Qu, Li-Jia

    2014-01-01

    Plant architecture is one of the key factors that affect plant survival and productivity. Plant body structure is established through the iterative initiation and outgrowth of lateral organs, which are derived from the shoot apical meristem and root apical meristem, after embryogenesis. Here we report that ADP1, a putative MATE (multidrug and toxic compound extrusion) transporter, plays an essential role in regulating lateral organ outgrowth, and thus in maintaining normal architecture of Arabidopsis. Elevated expression levels of ADP1 resulted in accelerated plant growth rate, and increased the numbers of axillary branches and flowers. Our molecular and genetic evidence demonstrated that the phenotypes of plants over-expressing ADP1 were caused by reduction of local auxin levels in the meristematic regions. We further discovered that this reduction was probably due to decreased levels of auxin biosynthesis in the local meristematic regions based on the measured reduction in IAA levels and the gene expression data. Simultaneous inactivation of ADP1 and its three closest homologs led to growth retardation, relative reduction of lateral organ number and slightly elevated auxin level. Our results indicated that ADP1-mediated regulation of the local auxin level in meristematic regions is an essential determinant for plant architecture maintenance by restraining the outgrowth of lateral organs. PMID:24391508

  18. ADP1 affects plant architecture by regulating local auxin biosynthesis.

    PubMed

    Li, Ruixi; Li, Jieru; Li, Shibai; Qin, Genji; Novák, Ondřej; Pěnčík, Aleš; Ljung, Karin; Aoyama, Takashi; Liu, Jingjing; Murphy, Angus; Gu, Hongya; Tsuge, Tomohiko; Qu, Li-Jia

    2014-01-01

    Plant architecture is one of the key factors that affect plant survival and productivity. Plant body structure is established through the iterative initiation and outgrowth of lateral organs, which are derived from the shoot apical meristem and root apical meristem, after embryogenesis. Here we report that ADP1, a putative MATE (multidrug and toxic compound extrusion) transporter, plays an essential role in regulating lateral organ outgrowth, and thus in maintaining normal architecture of Arabidopsis. Elevated expression levels of ADP1 resulted in accelerated plant growth rate, and increased the numbers of axillary branches and flowers. Our molecular and genetic evidence demonstrated that the phenotypes of plants over-expressing ADP1 were caused by reduction of local auxin levels in the meristematic regions. We further discovered that this reduction was probably due to decreased levels of auxin biosynthesis in the local meristematic regions based on the measured reduction in IAA levels and the gene expression data. Simultaneous inactivation of ADP1 and its three closest homologs led to growth retardation, relative reduction of lateral organ number and slightly elevated auxin level. Our results indicated that ADP1-mediated regulation of the local auxin level in meristematic regions is an essential determinant for plant architecture maintenance by restraining the outgrowth of lateral organs.

  19. Pattern recognition of native plant communities: Manitou Colorado test site

    NASA Technical Reports Server (NTRS)

    Driscoll, R. S.

    1972-01-01

    Optimum channel selection among 12 channels of multispectral scanner imagery identified six as providing the best information about 11 vegetation classes and two nonvegetation classes at the Manitou Experimental Forest. Intensive preprocessing of the scanner signals was required to eliminate a serious scan angle effect. Final processing of the normalized data provided acceptable recognition results of generalized plant community types. Serious errors occurred with attempts to classify specific community types within upland grassland areas. The consideration of the convex mixtures concept (effects of amounts of live plant cover, exposed soil, and plant litter cover on apparent scene radiances) significantly improved the classification of some of the grassland classes.

  20. Conservation and restoration of indigenous plants to improve community livelihoods: the Useful Plants Project

    NASA Astrophysics Data System (ADS)

    Ulian, Tiziana; Sacandé, Moctar; Mattana, Efisio

    2014-05-01

    Kew's Millennium Seed Bank partnership (MSBP) is one of the largest ex situ plant conservation initiatives, which is focused on saving plants in and from regions most at risk, particularly in drylands. Seeds are collected and stored in seed banks in the country of origin and duplicated in the Millennium Seed Bank in the UK. The MSBP also strengthens the capacity of local communities to successfully conserve and sustainably use indigenous plants, which are important for their wellbeing. Since 2007, high quality seed collections and research information have been gathered on ca. 700 useful indigenous plant species that were selected by communities in Botswana, Kenya, Mali, Mexico and South Africa through Project MGU - The Useful Plants Project. These communities range from various farmer's groups and organisations to traditional healers, organic cotton/crop producers and primary schools. The information on seed conservation and plant propagation was used to train communities and to propagate ca. 200 species that were then planted in local gardens, and as species reintroduced for reforestation programmes and enriching village forests. Experimental plots have also been established to further investigate the field performance (plant survival and growth rate) of indigenous species, using low cost procedures. In addition, the activities support revenue generation for local communities directly through the sustainable use of plant products or indirectly through wider environmental and cultural services. This project has confirmed the potential of biodiversity conservation to improve food security and human health, enhance community livelihoods and strengthen the resilience of land and people to the changing climate. This approach of using indigenous species and having local communities play a central role from the selection of species to their planting and establishment, supported by complementary research, may represent a model for other regions of the world, where

  1. Carers' representations of affective mental disorders in British Chinese communities.

    PubMed

    Koo, Kevin

    2012-11-01

    Infrequent use of and delayed presentation to professional services have increased the burden of mental illness in minority ethnic communities. Within the growing literature on informal carers, the Chinese remain relatively unstudied. This article reports a qualitative study of 14 carers to explore illness representations of affective disorders in British Chinese communities. Firstly, it places the study within a theoretical framework that permits an understanding of mental health and illness in different sociocultural belief systems. Next, it presents carers' narrative accounts in conceptualising mental illness, including its causes, manifestations and impact on patients and carers, and contextualises the findings within the existing literature. Finally, the article examines how the caring role may be constructed from the broader social experience of carers and their relationships within a community structure that values the group over the individual. Coping mechanisms are discussed in the context of the practice of caring as a moral obligation and of policy implications for more culturally appropriate support services for both Chinese carers and mental health patients.

  2. Nematode Assemblages in Native Plant Communities of Molokai, Hawaii

    PubMed Central

    Bernard, E. C.; Schmitt, D. P.

    2005-01-01

    Four native plant community types (in decreasing elevation: montane bog, rain forest, wet mesic forest, drier forest) on Molokai were sampled for nematodes. Six samples of 10 cores each were gathered from each community. Nematodes were extracted from 200 cm³ soil by elutriation. All extracted nematodes were counted and identified to species-level taxa. Sixty-seven species were identified among the four plant communities; only eight species occurred in all four communities. Species diversity and evenness were greater in the rain forest and mesic forest than in the bog and the drier forest, but the drier forest and mesic forest had similar species communities. The bog nematode community was not similar to the other three sites. In a presence/absence cluster analysis, all six bog sample assemblages clustered together. The rain forest samples also clustered together but were associated with the mesic forest sample closest to the rain forest edge. Of 11 nematode orders collected, Tylenchida accounted for 40% to 73% of all individuals, followed by Dorylaimida (5% to 17%). Diplogasterida were absent. No plant-parasitic nematodes of known Hawaiian agricultural importance or occurrence were collected in these native plant communities. Calculated nematode densities (76,000 to 321,300/m²) were comparable to those reported for some other Pacific tropical forests. PMID:19262867

  3. Can microcystins affect zooplankton structure community in tropical eutrophic reservoirs?

    PubMed

    Paes, T A S V; Costa, I A S; Silva, A P C; Eskinazi-Sant'Anna, E M

    2016-06-01

    The aim of our study was to assess whether cyanotoxins (microcystins) can affect the composition of the zooplankton community, leading to domination of microzooplankton forms (protozoans and rotifers). Temporal variations in concentrations of microcystins and zooplankton biomass were analyzed in three eutrophic reservoirs in the semi-arid northeast region of Brazil. The concentration of microcystins in water proved to be correlated with the cyanobacterial biovolume, indicating the contributions from colonial forms such as Microcystis in the production of cyanotoxins. At the community level, the total biomass of zooplankton was not correlated with the concentration of microcystin (r2 = 0.00; P > 0.001), but in a population-level analysis, the biomass of rotifers and cladocerans showed a weak positive correlation. Cyclopoid copepods, which are considered to be relatively inefficient in ingesting cyanobacteria, were negatively correlated (r2 = - 0.01; P > 0.01) with the concentration of cyanotoxins. Surprisingly, the biomass of calanoid copepods was positively correlated with the microcystin concentration (r2 = 0.44; P > 0.001). The results indicate that allelopathic control mechanisms (negative effects of microcystin on zooplankton biomass) do not seem to substantially affect the composition of mesozooplankton, which showed a constant and high biomass compared to the microzooplankton (rotifers). These results may be important to better understand the trophic interactions between zooplankton and cyanobacteria and the potential effects of allelopathic compounds on zooplankton.

  4. Does iodine biofortification affect oxidative metabolism in lettuce plants?

    PubMed

    Blasco, Begoña; Ríos, Juan Jose; Leyva, Rocío; Cervilla, Luis Miguel; Sánchez-Rodríguez, Eva; Rubio-Wilhelmi, María Mar; Rosales, Miguel Angel; Ruiz, Juan Manuel; Romero, Luis

    2011-09-01

    Plants produce low levels of reactive oxygen species (ROS), which form part of basic cell chemical communication; however, different types of stress can lead to an overexpression of ROS that can damage macromolecules essential for plant growth and development. Iodine is vital to human health, and iodine biofortification programs help improve the human intake through plant consumption. This biofortification process has been shown to influence the antioxidant capacity of lettuce plants, suggesting that the oxidative metabolism of the plant may be affected. The results of this study demonstrate that the response to oxidative stress is variable and depends on the form of iodine applied. Application of iodide (I(-)) to lettuce plants produces a reduction in superoxide dismutase (SOD) activity and an increase in catalase (CAT) and L-galactono dehydrogenase enzyme activities and in the activity of antioxidant compounds such as ascorbate (AA) and glutathione. This did not prove a very effective approach since a dose of 80 μM produced a reduction in the biomass of the plants. For its part, application of iodate (IO (3) (-) ) produced an increase in the activities of SOD, ascorbate peroxidase, and CAT, the main enzymes involved in ROS detoxification; it also increased the concentration of AA and the regenerative activities of the Halliwell-Asada cycle. These data confirm the non-phytotoxicity of IO (3) (-) since there is no lipid peroxidation or biomass reduction. According to our results, the ability of IO (3) (-) to induce the antioxidant system indicates that application of this form of iodine may be an effective strategy to improve the response of plants to different types of stress.

  5. Plant ecology. Anthropogenic environmental changes affect ecosystem stability via biodiversity.

    PubMed

    Hautier, Yann; Tilman, David; Isbell, Forest; Seabloom, Eric W; Borer, Elizabeth T; Reich, Peter B

    2015-04-17

    Human-driven environmental changes may simultaneously affect the biodiversity, productivity, and stability of Earth's ecosystems, but there is no consensus on the causal relationships linking these variables. Data from 12 multiyear experiments that manipulate important anthropogenic drivers, including plant diversity, nitrogen, carbon dioxide, fire, herbivory, and water, show that each driver influences ecosystem productivity. However, the stability of ecosystem productivity is only changed by those drivers that alter biodiversity, with a given decrease in plant species numbers leading to a quantitatively similar decrease in ecosystem stability regardless of which driver caused the biodiversity loss. These results suggest that changes in biodiversity caused by drivers of environmental change may be a major factor determining how global environmental changes affect ecosystem stability.

  6. Relative abundance of an invasive alien plant affects insect-flower interaction networks in Ireland

    NASA Astrophysics Data System (ADS)

    Stout, Jane C.; Casey, Leanne M.

    2014-02-01

    Invasive alien flowering plants may affect native plant pollinator interactions and have knock on impacts on populations of native plants and animals. The magnitude of these impacts, however, may be modified by the relative abundance of the invasive plant and the number of flowers it presents.We tested this by examining the structure of insect-flower interaction networks in six sites with increasing levels of invasion by Rhododendron ponticum in Ireland.Neither flower-visiting insect abundance, species richness nor diversity were related to R. ponticum flower abundance, but the composition of insect communities was. The total number of flowers in a site increased with the relative abundance of R. ponticum flowers but the number of co-flowering native plant species in these sites was low (<6), making interaction networks relatively small.As a result, changes in interaction network properties (connectance, interaction evenness and network level specialisation), which correlated with R. ponticum flower abundance, were a result of the small network size rather than due to changes in the resilience of networks.Overall, we conclude that the impacts of invasive alien plants on native plant-pollinator interactions are not only species specific, but site specific, according to the abundance of flowers produced by both the invasive and the native plants.

  7. Unravelling Linkages between Plant Community Composition and the Pathogen-Suppressive Potential of Soils

    PubMed Central

    Latz, Ellen; Eisenhauer, Nico; Rall, Björn Christian; Scheu, Stefan; Jousset, Alexandre

    2016-01-01

    Plant diseases cause dramatic yield losses worldwide. Current disease control practices can be deleterious for the environment and human health, calling for alternative and sustainable management regimes. Soils harbour microorganisms that can efficiently suppress pathogens. Uncovering mediators driving their functioning in the field still remains challenging, but represents an essential step in order to develop strategies for increased soil health. We set up plant communities of varying richness to experimentally test the potential of soils differing in plant community history to suppress the pathogen Rhizoctonia solani. The results indicate that plant communities shape soil-disease suppression via changes in abiotic soil properties and the abundance of bacterial groups including species of the genera Actinomyces, Bacillus and Pseudomonas. Further, the results suggest that pairwise interactions between specific plant species strongly affect soil suppressiveness. Using structural equation modelling, we provide a pathway orientated framework showing how the complex interactions between plants, soil and microorganisms jointly shape soil suppressiveness. Our results stress the importance of plant community composition as a determinant of soil functioning, such as the disease suppressive potential of soils. PMID:27021053

  8. Are organisational factors affecting the emotional withdrawal of community nurses?

    PubMed

    Karimi, Leila; Leggat, Sandra G; Cheng, Cindy; Donohue, Lisa; Bartram, Timothy; Oakman, Jodi

    2016-12-05

    Objective The aim of the present study was to investigate the effects of work organisation on the emotional labour withdrawal behaviour of Australian community nurses.Methods Using a paper-based survey, a sample of 312 Australian community nurses reported on their emotional dissonance, withdrawal behaviours (i.e. job neglect, job dissatisfaction, stress-related presenteeism) and work organisation. A model to determine the partial mediation effect of work organisation was developed based on a literature review. The fit of the proposed model was assessed via structural equation modelling using Analysis of Moment Structures (AMOS; IMB).Results Community nurses with higher levels of emotional dissonance were less likely to be satisfied with their job and work organisation and had a higher tendency to exhibit withdrawal behaviours. Work organisational factors mediated this relationship.Conclusion Emotional dissonance can be a potential stressor for community nurses that can trigger withdrawal behaviours. Improving work organisational factors may help reduce emotional conflict and its effect on withdrawal behaviours.What is known about the topic? Although emotional labour has been broadly investigated in the literature, very few studies have addressed the effect of the quality of work organisation on nurses' withdrawal behaviours in a nursing setting.What does this paper add? This paper provides evidence that work organisation affects levels of emotional dissonance and has an effect on job neglect through stress-related presenteeism.What are the implications for practitioners? In order to minimise stress-related presenteeism and job neglect, healthcare organisations need to establish a positive working environment, designed to improve the quality of relationships with management, provide appropriate rewards, recognition and effective workload management and support high-quality relationships with colleagues.

  9. Different farming and water regimes in Italian rice fields affect arbuscular mycorrhizal fungal soil communities.

    PubMed

    Lumini, Erica; Vallino, Marta; Alguacil, Maria M; Romani, Marco; Bianciotto, Valeria

    2011-07-01

    Arbuscular mycorrhizal fungi (AMF) comprise one of the main components of soil microbiota in most agroecosystems. These obligate mutualistic symbionts colonize the roots of most plants, including crop plants. Many papers have indicated that different crop management practices could affect AMF communities and their root colonization. However, there is little knowledge available on the influence of conventional and low-input agriculture on root colonization and AMF molecular diversity in rice fields. Two different agroecosystems (continuous conventional high-input rice monocropping and organic farming with a five-year crop rotation) and two different water management regimes have been considered in this study. Both morphological and molecular analyses were performed. The soil mycorrhizal potential, estimated using clover trap cultures, was high and similar in the two agroecosystems. The diversity of the AMF community in the soil, calculated by means of PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) and 18S rDNA sequencing on clover trap cultures roots, was higher for the organic cultivation. The rice roots cultivated in the conventional agrosystem or under permanent flooding showed no AMF colonization, while the rice plants grown under the organic agriculture system showed typical mycorrhization patterns. Considered together, our data suggest that a high-input cropping system and conventional flooding depress AMF colonization in rice roots and that organic managements could help maintain a higher diversity of AMF communities in soil.

  10. Ionizing radiation from Chernobyl affects development of wild carrot plants

    PubMed Central

    Boratyński, Zbyszek; Arias, Javi Miranda; Garcia, Cristina; Mappes, Tapio; Mousseau, Timothy A.; Møller, Anders P.; Pajares, Antonio Jesús Muñoz; Piwczyński, Marcin; Tukalenko, Eugene

    2016-01-01

    Radioactivity released from disasters like Chernobyl and Fukushima is a global hazard and a threat to exposed biota. To minimize the deleterious effects of stressors organisms adopt various strategies. Plants, for example, may delay germination or stay dormant during stressful periods. However, an intense stress may halt germination or heavily affect various developmental stages and select for life history changes. Here, we test for the consequence of exposure to ionizing radiation on plant development. We conducted a common garden experiment in an uncontaminated greenhouse using 660 seeds originating from 33 wild carrots (Daucus carota) collected near the Chernobyl nuclear power plant. These maternal plants had been exposed to radiation levels that varied by three orders of magnitude. We found strong negative effects of elevated radiation on the timing and rates of seed germination. In addition, later stages of development and the timing of emergence of consecutive leaves were delayed by exposure to radiation. We hypothesize that low quality of resources stored in seeds, damaged DNA, or both, delayed development and halted germination of seeds from plants exposed to elevated levels of ionizing radiation. We propose that high levels of spatial heterogeneity in background radiation may hamper adaptive life history responses. PMID:27982121

  11. Ionizing radiation from Chernobyl affects development of wild carrot plants

    NASA Astrophysics Data System (ADS)

    Boratyński, Zbyszek; Arias, Javi Miranda; Garcia, Cristina; Mappes, Tapio; Mousseau, Timothy A.; Møller, Anders P.; Pajares, Antonio Jesús Muñoz; Piwczyński, Marcin; Tukalenko, Eugene

    2016-12-01

    Radioactivity released from disasters like Chernobyl and Fukushima is a global hazard and a threat to exposed biota. To minimize the deleterious effects of stressors organisms adopt various strategies. Plants, for example, may delay germination or stay dormant during stressful periods. However, an intense stress may halt germination or heavily affect various developmental stages and select for life history changes. Here, we test for the consequence of exposure to ionizing radiation on plant development. We conducted a common garden experiment in an uncontaminated greenhouse using 660 seeds originating from 33 wild carrots (Daucus carota) collected near the Chernobyl nuclear power plant. These maternal plants had been exposed to radiation levels that varied by three orders of magnitude. We found strong negative effects of elevated radiation on the timing and rates of seed germination. In addition, later stages of development and the timing of emergence of consecutive leaves were delayed by exposure to radiation. We hypothesize that low quality of resources stored in seeds, damaged DNA, or both, delayed development and halted germination of seeds from plants exposed to elevated levels of ionizing radiation. We propose that high levels of spatial heterogeneity in background radiation may hamper adaptive life history responses.

  12. Opposing phylogenetic diversity gradients of plant and soil bacterial communities

    PubMed Central

    Goberna, Marta; Navarro-Cano, Jose A.; Verdú, Miguel

    2016-01-01

    Plants and soil microbes show parallel patterns of species-level diversity. Diverse plant communities release a wider range of organics that are consumed by more microbial species. We speculated, however, that diversity metrics accounting for the evolutionary distance across community members would reveal opposing patterns between plant and soil bacterial phylogenetic diversity. Plant phylogenetic diversity enhances plant productivity and thus expectedly soil fertility. This, in turn, might reduce bacterial phylogenetic diversity by favouring one (or a few) competitive bacterial clade. We collected topsoils in 15 semi-arid plant patches and adjacent low-cover areas configuring a plant phylodiversity gradient, pyrosequenced the 16S rRNA gene to identify bacterial taxa and analysed soil fertility parameters. Structural equation modelling showed positive effects of both plant richness and phylogenetic diversity on soil fertility. Fertility increased bacterial richness but reduced bacterial phylogenetic diversity. This might be attributed to the competitive dominance of a lineage based on its high relative fitness. This suggests biotic interactions as determinants of the soil bacterial community assembly, while emphasizing the need to use phylogeny-informed metrics to tease apart the processes underlying the patterns of diversity. PMID:26888037

  13. Opposing phylogenetic diversity gradients of plant and soil bacterial communities.

    PubMed

    Goberna, Marta; Navarro-Cano, Jose A; Verdú, Miguel

    2016-02-24

    Plants and soil microbes show parallel patterns of species-level diversity. Diverse plant communities release a wider range of organics that are consumed by more microbial species. We speculated, however, that diversity metrics accounting for the evolutionary distance across community members would reveal opposing patterns between plant and soil bacterial phylogenetic diversity. Plant phylogenetic diversity enhances plant productivity and thus expectedly soil fertility. This, in turn, might reduce bacterial phylogenetic diversity by favouring one (or a few) competitive bacterial clade. We collected topsoils in 15 semi-arid plant patches and adjacent low-cover areas configuring a plant phylodiversity gradient, pyrosequenced the 16S rRNA gene to identify bacterial taxa and analysed soil fertility parameters. Structural equation modelling showed positive effects of both plant richness and phylogenetic diversity on soil fertility. Fertility increased bacterial richness but reduced bacterial phylogenetic diversity. This might be attributed to the competitive dominance of a lineage based on its high relative fitness. This suggests biotic interactions as determinants of the soil bacterial community assembly, while emphasizing the need to use phylogeny-informed metrics to tease apart the processes underlying the patterns of diversity.

  14. Marker gene tethering by nucleoporins affects gene expression in plants.

    PubMed

    Smith, Sarah; Galinha, Carla; Desset, Sophie; Tolmie, Frances; Evans, David; Tatout, Christophe; Graumann, Katja

    2015-01-01

    In non-plant systems, chromatin association with the nuclear periphery affects gene expression, where interactions with nuclear envelope proteins can repress and interactions with nucleoporins can enhance transcription. In plants, both hetero- and euchromatin can localize at the nuclear periphery, but the effect of proximity to the nuclear periphery on gene expression remains largely unknown. This study explores the putative function of Seh1 and Nup50a nucleoporins on gene expression by using the Lac Operator / Lac Repressor (LacI-LacO) system adapted to Arabidopsis thaliana. We used LacO fused to the luciferase reporter gene (LacO:Luc) to investigate whether binding of the LacO:Luc transgene to nucleoporin:LacI protein fusions alters luciferase expression. Two separate nucleoporin-LacI-YFP fusions were introduced into single insert, homozygous LacO:Luc Arabidopsis plants. Homozygous plants carrying LacO:Luc and a single insert of either Seh1-LacI-YFP or Nup50a-LacI-YFP were tested for luciferase activity and compared to plants containing LacO:Luc only. Seh1-LacI-YFP increased, while Nup50a-LacI-YFP decreased luciferase activity. Seh1-LacI-YFP accumulated at the nuclear periphery as expected, while Nup50a-LacI-YFP was nucleoplasmic and was not selected for further study. Protein and RNA levels of luciferase were quantified by western blotting and RT-qPCR, respectively. Increased luciferase activity in LacO:Luc+Seh1-LacI-YFP plants was correlated with increased luciferase protein and RNA levels. This change of luciferase expression was abolished by disruption of LacI-LacO binding by treating with IPTG in young seedlings, rosette leaves and inflorescences. This study suggests that association with the nuclear periphery is involved in the regulation of gene expression in plants.

  15. Granivory of invasive, naturalized, and native plants in communities differentially susceptible to invasion.

    PubMed

    Connolly, B M; Pearson, D E; Mack, R N

    2014-07-01

    mammals predicts plant establishment for our test species within these communities but not between them. Accumulating evidence suggests that seed predation can be an important biotic filter affecting plant establishment via differences in consumer preferences and abundance with important ramifications for plant invasions and in situ community assembly.

  16. Plant communities as drivers of soil respiration: pathways, mechanisms, and significance for global change

    NASA Astrophysics Data System (ADS)

    Metcalfe, D. B.; Fisher, R. A.; Wardle, D. A.

    2011-08-01

    Understanding the impacts of plant community characteristics on soil carbon dioxide efflux (R) is a key prerequisite for accurate prediction of the future carbon (C) balance of terrestrial ecosystems under climate change. However, developing a mechanistic understanding of the determinants of R is complicated by the presence of multiple different sources of respiratory C within soil - such as soil microbes, plant roots and their mycorrhizal symbionts - each with their distinct dynamics and drivers. In this review, we synthesize relevant information from a wide spectrum of sources to evaluate the current state of knowledge about plant community effects on R, examine how this information is incorporated into global climate models, and highlight priorities for future research. Despite often large variation amongst studies and methods, several general trends emerge. Mechanisms whereby plants affect R may be grouped into effects on belowground C allocation, aboveground litter properties and microclimate. Within vegetation types, the amount of C diverted belowground, and hence R, may be controlled mainly by the rate of photosynthetic C uptake, while amongst vegetation types this should be more dependent upon the specific C allocation strategies of the plant life form. We make the case that plant community composition, rather than diversity, is usually the dominant control on R in natural systems. Individual species impacts on R may be largest where the species accounts for most of the biomass in the ecosystem, has very distinct traits to the rest of the community and/or modulates the occurrence of major natural disturbances. We show that climate vegetation models incorporate a number of pathways whereby plants can affect R, but that simplifications regarding allocation schemes and drivers of litter decomposition may limit model accuracy. We also suggest that under a warmer future climate, many plant communities may shift towards dominance by fast growing plants which

  17. Carbon nanotubes as plant growth regulators: effects on tomato growth, reproductive system, and soil microbial community.

    PubMed

    Khodakovskaya, Mariya V; Kim, Bong-Soo; Kim, Jong Nam; Alimohammadi, Mohammad; Dervishi, Enkeleda; Mustafa, Thikra; Cernigla, Carl E

    2013-01-14

    Multi-walled carbon nanotubes (CNTs) can affect plant phenotype and the composition of soil microbiota. Tomato plants grown in soil supplemented with CNTs produce two times more flowers and fruit compared to plants grown in control soil. The effect of carbon nanotubes on microbial community of CNT-treated soil is determined by denaturing gradient gel electrophoresis and pyrosequencing analysis. Phylogenetic analysis indicates that Proteobacteria and Bacteroidetes are the most dominant groups in the microbial community of soil. The relative abundances of Bacteroidetes and Firmicutes are found to increase, whereas Proteobacteria and Verrucomicorbia decrease with increasing concentration of CNTs. The results of comparing diversity indices and species level phylotypes (OTUs) between samples showed that there is not a significant affect on bacterial diversity.

  18. Belowground induction by Delia radicum or phytohormones affect aboveground herbivore communities on field-grown broccoli

    PubMed Central

    Pierre, S. P.; Dugravot, S.; Hervé, M. R.; Hassan, H. M.; van Dam, N. M.; Cortesero, A. M.

    2013-01-01

    Induced plant defence in response to phytophagous insects is a well described phenomenon. However, so far little is known about the effect of induced plant responses on subsequently colonizing herbivores in the field. Broccoli plants were induced in the belowground compartment using (i) infestation by the root-herbivore Delia radicum, (ii) root application of jasmonic acid (JA) or (iii) root application of salicylic acid (SA). The abundance of D. radicum and six aboveground herbivores displaying contrasting levels of host specialization were surveyed for 5 weeks. Our study showed that the response of herbivores was found to differ from one another, depending on the herbivore species, its degree of specialization and the root treatment. The abundance of the root herbivore D. radicum and particularly the number of emerging adults was decreased by both phytohormone treatments, while the number of D. radicum eggs was increased on conspecific infested plants. The root infestation exhibited moderate effects on the aboveground community. The abundance of the aphid Brevicoryne brassicae was strongly increased on D. radicum infested plants, but the other species were not impacted. Root hormone applications exhibited a strong effect on the abundance of specialist foliar herbivores. A higher number of B. brassicae and Pieris brassicae and a lower number of Plutella xylostella were found on JA treated plants. On SA treated plants we observed a decrease of the abundance of B. brassicae, Pi. rapae, and P. xylostella. Surprisingly, generalist species, Mamestra brassicae and Myzus persicae were not affected by root induction treatments. Finally, root treatments had no significant effect on either glucosinolate (GLS) profiles of the heads or on plant quality parameters. These results are discussed from the perspective of below- aboveground interactions and adaptations of phytophagous insects to induced plant responses according to their trophic specialization level. PMID:23970888

  19. Nitrogen-limitation and invasive sweetclover impacts vary between two Great Plains plant communities

    USGS Publications Warehouse

    Van Riper, Laura C.; Larson, Diane L.; Larson, Jennifer L.

    2010-01-01

    Yellow sweetclover is an exotic herbaceous legume common in the Great Plains of the US. Although woody legumes have been shown to affect ecosystem processes through nitrogen (N) fixation (i.e., they can be considered "transformers" sensu Richardson et al. (2000)), the same has not been shown for short-lived herbaceous species. The objectives of this study were to (1) quantify the effects of yellow sweetclover on N mineralization and nitrification and (2) assess the effects of N fertilization on two plant communities, badlands sparse vegetation and western wheatgrass prairie. We used in situ (in wheatgrass prairie) and laboratory incubations (for both plant communities) to assess N dynamics at sites with high and low sweetclover cover in the two plant communities. We found that both N mineralization and nitrification were higher in the high sweetclover plots in the sparse plant community, but not in the wheatgrass prairie. To assess fertilization effects and determine if nutrients or water were limiting at our sites, we conducted a field experiment with five resource addition treatments, (1) N, (2) N + water, (3) water, (4) phosphorus, and (5) no addition. Water was limiting in the wheatgrass prairie but contrary to expectation, N was not. In contrast, N was limiting in the sparse community, where a fertilization effect was seen in exotic forbs, especially the toxic invader Halogeton glomeratus. Our results emphasize the contingent nature of plant invasion in which effects are largely dependent on attributes of the recipient vegetation.

  20. Coal mining activities change plant community structure due to air pollution and soil degradation.

    PubMed

    Pandey, Bhanu; Agrawal, Madhoolika; Singh, Siddharth

    2014-10-01

    The aim of this study was to investigate the effects of coal mining activities on the community structures of woody and herbaceous plants. The response of individual plants of community to defilement caused by coal mining was also assessed. Air monitoring, soil physico-chemical and phytosociological analyses were carried around Jharia coalfield (JCF) and Raniganj coalfield. The importance value index of sensitive species minified and those of tolerant species enhanced with increasing pollution load and altered soil quality around coal mining areas. Although the species richness of woody and herbaceous plants decreased with higher pollution load, a large number of species acclimatized to the stress caused by the coal mining activities. Woody plant community at JCF was more affected by coal mining than herbaceous community. Canonical correspondence analysis revealed that structure of herbaceous community was mainly driven by soil total organic carbon, soil nitrogen, whereas woody layer community was influenced by sulphur dioxide in ambient air, soil sulphate and soil phosphorus. The changes in species diversity observed at mining areas indicated an increase in the proportion of resistant herbs and grasses showing a tendency towards a definite selection strategy of ecosystem in response to air pollution and altered soil characteristics.

  1. Plant community associations of two invasive thistles

    PubMed Central

    Rauschert, Emily S.J.; Shea, Katriona; Goslee, Sarah

    2015-01-01

    In order to combat the growing problems associated with biological invasions, many researchers have focused on identifying which communities are most vulnerable to invasion by exotic species. However, once established, invasive species can significantly change the composition of the communities that they invade. The first step to disentangling the direction of causality is to discern whether a relationship with other vegetation exists at all. Carduus nutans and C. acanthoides are similar invasive thistles, which have caused substantial economic damage worldwide. We assessed the associations between the thistles and the standing flora in four sites in central Pennsylvania in which they co-occur. After sampling nearly 2000 plots of 1 m2, we used partial Mantel tests to assess the differences in vegetation between thistle and non-thistle plots after accounting for location, and non-metric multidimensional scaling to visualize differences among plots and sites. We found significant differences in community composition in plots with and without Carduus thistles. The non-native species Sisymbrium officinale and Coronilla varia were consistently associated with the presence of Carduus thistles. Several species were associated with areas that were free of Carduus thistles, including an important non-native pasture species (Trifolium repens). We found no evidence for differences in composition between plots with C. nutans versus C. acanthoides, suggesting that they have similar associations with the vegetation community. We conclude that even at the within-field scale, areas invaded by Carduus thistles have different vegetation associations than uninvaded areas, allowing us to target future research about the role of vegetation structure in resisting and responding to invasion. PMID:26038126

  2. Physicochemical conditions in affecting the distribution of spring phytoplankton community

    NASA Astrophysics Data System (ADS)

    Wei, Yuqiu; Liu, Haijiao; Zhang, Xiaodong; Xue, Bing; Munir, Sonia; Sun, Jun

    2017-03-01

    To better understand the physicochemical conditions in affecting regional distribution of phytoplankton community, one research cruise was carried out in the Bohai Sea and Yellow Sea during 3rd and 23th May, 2010. The phytoplankton community, including Bacillariophyta (105 taxa), Pyrrophyta (54 taxa), Chrysophyta (1 taxon) and Chlorophyta (2 taxa), had been identified and clearly described from six ecological provinces. And, the six ecological provinces were partitioned based on the top twenty dominant species related with notable physicochemical parameters. In general, the regional distributions of phytoplankton ecological provinces were predominantly influenced by the physicochemical properties induced by the variable water masses and circulations. The predominant diatoms in most of water samples showed well adaptability in turbulent and eutrophic conditions. However, several species of dinoflagellates e.g., Protoperidinium conicum, Protoperidinium triestinum, Protoperidinium sp. and Gymnodinium lohmanni preferred warmer, saltier and nutrient-poor environment. Moreover, the dinoflagellates with high frequency in the Yellow Sea might be transported from the Yellow Sea Warm Current. The horizontal distribution of phytoplankton was depicted by diatoms and controlled by phosphate concentration, while the vertical distribution was mainly supported by light and nutrients availability in the subsurface and bottom layers, respectively.

  3. Do unpaved, low-traffic roads affect bird communities?

    NASA Astrophysics Data System (ADS)

    Mammides, Christos; Kounnamas, Constantinos; Goodale, Eben; Kadis, Costas

    2016-02-01

    Unpaved, low traffic roads are often assumed to have minimal effects on biodiversity. To explore this assertion, we sampled the bird communities in fifteen randomly selected sites in Pafos Forest, Cyprus and used multiple regression to quantify the effects of such roads on the total species richness. Moreover, we classified birds according to their migratory status and their global population trends, and tested each category separately. Besides the total length of unpaved roads, we also tested: a. the site's habitat diversity, b. the coefficient of variation in habitat (patch) size, c. the distance to the nearest agricultural field, and d. the human population size of the nearest village. We measured our variables at six different distances from the bird point-count locations. We found a strong negative relationship between the total bird richness and the total length of unpaved roads. The human population size of the nearest village also had a negative effect. Habitat diversity was positively related to species richness. When the categories were tested, we found that the passage migrants were influenced more by the road network while resident breeders were influenced by habitat diversity. Species with increasing and stable populations were only marginally affected by the variables tested, but the effect of road networks on species with decreasing populations was large. We conclude that unpaved and sporadically used roads can have detrimental effects on the bird communities, especially on vulnerable species. We propose that actions are taken to limit the extent of road networks within protected areas, especially in sites designated for their rich avifauna, such as Pafos Forest, where several of the affected species are species of European and global importance.

  4. Relationships among plants, soils and microbial communities along a hydrological gradient in the New Jersey Pinelands, USA

    PubMed Central

    Yu, Shen; Ehrenfeld, Joan G.

    2010-01-01

    Background and Aims Understanding the role of different components of hydrology in structuring wetland communities is not well developed. A sequence of adjacent wetlands located on a catenary sequence of soils and receiving the same sources and qualities of water is used to examine specifically the role of water-table median position and variability in affecting plant and microbial community composition and soil properties. Methods Two replicates of three types of wetland found adjacent to each other along a hydrological gradient in the New Jersey Pinelands (USA) were studied. Plant-community and water-table data were obtained within a 100-m2 plot in each community (pine swamp, maple swamp and Atlantic-white-cedar swamp). Monthly soil samples from each plot were analysed for soil moisture, organic matter, extractable nitrogen fractions, N mineralization rate and microbial community composition. Multivariate ordination methods were used to compare patterns among sites within and between data sets. Key Results The maple and pine wetlands were more similar to each other in plant community composition, soil properties and microbial community composition than either was to the cedar swamps. However, maple and pine wetlands differed from each other in water-table descriptors as much as they differed from the cedar swamps. All microbial communities were dominated by Gram-positive bacteria despite hydrologic differences among the sites. Water-table variability was as important as water-table level in affecting microbial communities. Conclusions Water tables affect wetland communities through both median level and variability. Differentiation of both plant and microbial communities are not simple transforms of differences in water-table position, even when other hydrologic factors are kept constant. Rather, soil genesis, a result of both water-table position and geologic history, appears to be the main factor affecting plant and microbial community similarities. PMID

  5. Behavioural and community ecology of plants that cry for help.

    PubMed

    Dicke, Marcel

    2009-06-01

    Plants respond to insect herbivory with the production of volatiles that attract carnivorous enemies of the herbivores, a phenomenon called indirect defence or 'plants crying for help'. Plants are under selection to maximize Darwinian fitness, and this can be done by making the right 'decisions' (i.e. by responding to environmental stress in ways that maximize seed production). Plant decisions related to the response to herbivory in terms of the emission of herbivore-induced volatiles include 'to respond or not to respond', 'how fast to respond', 'how to respond' and 'when to stop responding'. In this review, the state-of-the-art of the research field is presented in the context of these decisions that plants face. New questions and directions for future research are identified. To understand the consequences of plant responses in a community context, it is important to expand research from individual interactions to multispecies interactions in a community context. To achieve this, detailed information on underlying mechanisms is essential and first steps on this road have been made. This selective review addresses the ecology of herbivore-induced plant volatiles (HIPVs) by integrating information on mechanisms and ecological functions. New questions are identified as well as challenges for extending current information to community ecology.

  6. Genetic diversity within a dominant plant outweighs plant species diversity in structuring an arthropod community.

    PubMed

    Crawford, Kerri M; Rudgers, Jennifer A

    2013-05-01

    Plant biodiversity is being lost at a rapid rate. This has spurred much interest in elucidating the consequences of this loss for higher trophic levels. Experimental tests have shown that both plant species diversity and genetic diversity within a plant species can influence arthropod community structure. However, the majority of these studies have been conducted in separate systems, so their relative importance is currently unresolved. Furthermore, potential interactions between the two levels of diversity, which likely occur in natural systems, have not been investigated. To clarify these issues, we conducted three experiments in a freshwater sand dune ecosystem. We (1) independently manipulated plant species diversity, (2) independently manipulated genetic diversity within the dominant plant species, Ammophila breviligulata, and (3) jointly manipulated genetic diversity within the dominant plant and species diversity. We found that genetic diversity within the dominant plant species, Ammophila breviligulata, more strongly influenced arthropod communities than plant species diversity, but this effect was dependent on the presence of other species. In species mixtures, A. breviligulata genetic diversity altered overall arthropod community composition, and arthropod richness and abundance peaked at the highest level of genetic diversity. Positive nonadditive effects of diversity were detected, suggesting that arthropods respond to emergent properties of diverse plant communities. However, in the independent manipulations where A. breviligulata was alone, effects of genetic diversity were weaker, with only arthropod richness responding. In contrast, plant species diversity only influenced arthropods when A. breviligulata was absent, and then only influenced herbivore abundance. In addition to showing that genetic diversity within a dominant plant species can have large effects on arthropod community composition, these results suggest that understanding how species

  7. Links between plant community composition, soil organic matter quality and microbial communities in contrasting tundra habitats.

    PubMed

    Eskelinen, Anu; Stark, Sari; Männistö, Minna

    2009-08-01

    Plant communities, soil organic matter and microbial communities are predicted to be interlinked and to exhibit concordant patterns along major environmental gradients. We investigated the relationships between plant functional type composition, soil organic matter quality and decomposer community composition, and how these are related to major environmental variation in non-acid and acid soils derived from calcareous versus siliceous bedrocks, respectively. We analysed vegetation, organic matter and microbial community compositions from five non-acidic and five acidic heath sites in alpine tundra in northern Europe. Sequential organic matter fractionation was used to characterize organic matter quality and phospholipid fatty acid analysis to detect major variation in decomposer communities. Non-acidic and acidic heaths differed substantially in vegetation composition, and these disparities were associated with congruent shifts in soil organic matter and microbial communities. A high proportion of forbs in the vegetation was positively associated with low C:N and high soluble N:phenolics ratios in soil organic matter, and a high proportion of bacteria in the microbial community. On the contrary, dwarf shrub-rich vegetation was associated with high C:N and low soluble N:phenolics ratios, and a high proportion of fungi in the microbial community. Our study demonstrates a strong link between the plant community composition, soil organic matter quality, and microbial community composition, and that differences in one compartment are paralleled by changes in others. Variation in the forb-shrub gradient of vegetation may largely dictate variations in the chemical quality of organic matter and decomposer communities in tundra ecosystems. Soil pH, through its direct and indirect effects on plant and microbial communities, seems to function as an ultimate environmental driver that gives rise to and amplifies the interactions between above- and belowground systems.

  8. Interplay between Senecio jacobaea and plant, soil, and aboveground insect community composition.

    PubMed

    Bezemer, T Martijn; Harvey, Jeffrey A; Kowalchuk, George A; Korpershoek, Hanna; van der Putten, Wim H

    2006-08-01

    To elucidate the factors that affect the performance of plants in their natural environment, it is essential to study interactions with other neighboring plants, as well as with above- and belowground higher trophic organisms. We used a long-term field experiment to study how local plant community diversity influenced colonization by the biennial composite Senecio jacobaea in its native range in The Netherlands in Europe. We tested the effect of sowing later-succession plant species (0, 4, or 15 species) on plant succession and S. jacobaea performance. Over a period of eight years, the percent cover of S. jacobaea was relatively low in communities sown with 15 or 4 later-succession plant species compared to plots that were not sown, but that were colonized naturally. However, after four years of high abundance, the density of S. jacobaea in unsown plots started to decline, and the size of the individual plants was smaller than in the plots sown with 15 or 4 plant species. In the unsown plots, densities of aboveground leaf-mining, flower-feeding, and stem-boring insects on S. jacobaea plants were lower than on plants in sown plots, and there was a strong positive relationship between plant size and levels of herbivory. In a greenhouse experiment, we grew S. jacobaea in sterilized soil inoculated with soil from the different sowing treatments of the field experiment. Biomass production was lower when S. jacobaea test plants were grown in soil from the unsown plots than in soil from the sown plots (4 or 15 species). Molecular analysis of the fungal and bacterial communities revealed that the composition of fungal communities in unsown plots differed significantly from those in sown plots, suggesting that soil fungi could have been involved in the relative growth reduction of S. jacobaea in the greenhouse bioassay. Our results show that, in its native habitat, the abundance of S. jacobaea depends on the initial composition of the plant community and that, on a scale of

  9. Interaction of historical and nonhistorical disturbances maintains native plant communities.

    PubMed

    Davies, K W; Svejcar, T J; Bates, J D

    2009-09-01

    Historical disturbance regimes are often considered a critical element in maintaining native plant communities. However, the response of plant communities to disturbance may be fundamentally altered as a consequence of invasive plants, climate change, or prior disturbances. The appropriateness of historical disturbance patterns under modern conditions and the interactions among disturbances are issues that ecologists must address to protect and restore native plant communities. We evaluated the response of Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh plant communities to their historical disturbance regime compared to other disturbance regimes. The historical disturbance regime of these plant communities was periodic fires with minimal grazing by large herbivores. We also investigated the influence of prior disturbance (grazing) on the response of these communities to subsequent disturbance (burning). Treatments were: (1) ungrazed (livestock grazing excluded since 1936) and unburned, (2) grazed and unburned, (3) ungrazed and burned (burned in 1993), and (4) grazed and burned. The ungrazed-burned treatment emulated the historical disturbance regime. Vegetation cover, density, and biomass production were measured the 12th, 13th, and 14th year post-burning. Prior to burning the presence of Bromus tectorum L., an exotic annual grass, was minimal (<0.5% cover), and vegetation characteristics were similar between grazed and ungrazed treatments. However, litter accumulation was almost twofold greater in ungrazed than in grazed treatments. Long-term grazing exclusion followed by burning resulted in a substantial B. tectorum invasion, but burning the grazed areas did not produce an invasion. The ungrazed-burned treatment also had less perennial vegetation than other treatments. The accumulation of litter (fuel) in ungrazed treatments may have resulted in greater fire-induced mortality of perennial vegetation in ungrazed compared to grazed treatments

  10. Quantification of Heavy Metals in Mining Affected Soil and Their Bioaccumulation in Native Plant Species.

    PubMed

    Nawab, Javed; Khan, Sardar; Shah, Mohammad Tahir; Khan, Kifayatullah; Huang, Qing; Ali, Roshan

    2015-01-01

    Several anthropogenic and natural sources are considered as the primary sources of toxic metals in the environment. The current study investigates the level of heavy metals contamination in the flora associated with serpentine soil along the Mafic and Ultramafic rocks northern-Pakistan. Soil and wild native plant species were collected from chromites mining affected areas and analyzed for heavy metals (Cr, Ni, Fe, Mn, Co, Cu and Zn) using atomic absorption spectrometer (AAS-PEA-700). The heavy metal concentrations were significantly (p < 0.01) higher in mine affected soil as compared to reference soil, however Cr and Ni exceeded maximum allowable limit (250 and 60 mg kg(-1), respectively) set by SEPA for soil. Inter-metal correlations between soil, roots and shoots showed that the sources of contamination of heavy metals were mainly associated with chromites mining. All the plant species accumulated significantly higher concentrations of heavy metals as compared to reference plant. The open dumping of mine wastes can create serious problems (food crops and drinking water contamination with heavy metals) for local community of the study area. The native wild plant species (Nepeta cataria, Impatiens bicolor royle, Tegetis minuta) growing on mining affected sites may be used for soil reclamation contaminated with heavy metals.

  11. Land-use history alters contemporary insect herbivore community composition and decouples plant-herbivore relationships.

    PubMed

    Hahn, Philip G; Orrock, John L

    2015-05-01

    Past land use can create altered soil conditions and plant communities that persist for decades, although the effects of these altered conditions on consumers are rarely investigated. Using a large-scale field study at 36 sites in longleaf pine (Pinus palustris) woodlands, we examined whether historic agricultural land use leads to differences in the abundance and community composition of insect herbivores (grasshoppers, families Acrididae and Tettigoniidae). We measured the cover of six plant functional groups and several environmental variables to determine whether historic agricultural land use affects the relationships between plant cover or environmental conditions and grasshopper assemblages. Land-use history had taxa-specific effects and interacted with herbaceous plant cover to alter grasshopper abundances, leading to significant changes in community composition. Abundance of most grasshopper taxa increased with herbaceous cover in woodlands with no history of agriculture, but there was no relationship in post-agricultural woodlands. We also found that grasshopper abundance was negatively correlated with leaf litter cover. Soil hardness was greater in post-agricultural sites (i.e. more compacted) and was associated with grasshopper community composition. Both herbaceous cover and leaf litter cover are influenced by fire frequency, suggesting a potential indirect role of fire on grasshopper assemblages. Our results demonstrate that historic land use may create persistent differences in the composition of grasshopper assemblages, while contemporary disturbances (e.g. prescribed fire) may be important for determining the abundance of grasshoppers, largely through the effect of fire on plants and leaf litter. Therefore, our results suggest that changes in the contemporary management regimes (e.g. increasing prescribed fire) may not be sufficient to shift the structure of grasshopper communities in post-agricultural sites towards communities in non

  12. Land-use history alters contemporary insect herbivore community composition and decouples plant-herbivore relationships.

    SciTech Connect

    Hahn, Philip G.; Orrock, John L.

    2015-04-01

    1. Past land use can create altered soil conditions and plant communities that persist for decades, although the effects of these altered conditions on consumers are rarely investigated. 2. Using a large-scale field study at 36 sites in longleaf pine (Pinus palustris) woodlands, we examined whether historic agricultural land use leads to differences in the abundance and community composition of insect herbivores (grasshoppers, families Acrididae and Tettigoniidae). 3. We measured the cover of six plant functional groups and several environmental variables to determine whether historic agricultural land use affects the relationships between plant cover or environmental conditions and grasshopper assemblages. 4. Land-use history had taxa-specific effects and interacted with herbaceous plant cover to alter grasshopper abundances, leading to significant changes in community composition. Abundance of most grasshopper taxa increased with herbaceous cover in woodlands with no history of agriculture, but there was no relationship in post-agricultural woodlands. We also found that grasshopper abundance was negatively correlated with leaf litter cover. Soil hardness was greater in post-agricultural sites (i.e. more compacted) and was associated with grasshopper community composition. Both herbaceous cover and leaf litter cover are influenced by fire frequency, suggesting a potential indirect role of fire on grasshopper assemblages. 5. Our results demonstrate that historic land use may create persistent differences in the composition of grasshopper assemblages, while contemporary disturbances (e.g. prescribed fire) may be important for determining the abundance of grasshoppers, largely through the effect of fire on plants and leaf litter. Therefore, our results suggest that changes in the contemporary management regimes (e.g. increasing prescribed fire) may not be sufficient to shift the structure of grasshopper communities in post-agricultural sites towards communities in

  13. Plant-mediated interactions between two herbivores differentially affect a subsequently arriving third herbivore in populations of wild cabbage.

    PubMed

    Kroes, A; Stam, J M; David, A; Boland, W; van Loon, J J A; Dicke, M; Poelman, E H

    2016-11-01

    Plants are part of biodiverse communities and frequently suffer from attack by multiple herbivorous insects. Plant responses to these herbivores are specific for insect feeding guilds: aphids and caterpillars induce different plant phenotypes. Moreover, plants respond differentially to single or dual herbivory, which may cascade into a chain of interactions in terms of resistance to other community members. Whether differential responses to single or dual herbivory have consequences for plant resistance to yet a third herbivore is unknown. We assessed the effects of single or dual herbivory by Brevicoryne brassicae aphids and/or Plutella xylostella caterpillars on resistance of plants from three natural populations of wild cabbage to feeding by caterpillars of Mamestra brassicae. We measured plant gene expression and phytohormone concentrations to illustrate mechanisms involved in induced responses. Performance of both B. brassicae and P. xylostella was reduced when feeding simultaneously with the other herbivore, compared to feeding alone. Gene expression and phytohormone concentrations in plants exposed to dual herbivory were different from those found in plants exposed to herbivory by either insect alone. Plants previously induced by both P. xylostella and B. brassicae negatively affected growth of the subsequently arriving M. brassicae. Furthermore, induced responses varied between wild cabbage populations. Feeding by multiple herbivores differentially activates plant defences, which has plant-mediated negative consequences for a subsequently arriving herbivore. Plant population-specific responses suggest that plant populations adapt to the specific communities of insect herbivores. Our study contributes to the understanding of plant defence plasticity in response to multiple insect attacks.

  14. Bacterial Communities Associated with Different Anthurium andraeanum L. Plant Tissues.

    PubMed

    Sarria-Guzmán, Yohanna; Chávez-Romero, Yosef; Gómez-Acata, Selene; Montes-Molina, Joaquín Adolfo; Morales-Salazar, Eleacin; Dendooven, Luc; Navarro-Noya, Yendi E

    2016-09-29

    Plant-associated microbes have specific beneficial functions and are considered key drivers for plant health. The bacterial community structure of healthy Anthurium andraeanum L. plants was studied by 16S rRNA gene pyrosequencing associated with different plant parts and the rhizosphere. A limited number of bacterial taxa, i.e., Sinorhizobium, Fimbriimonadales, and Gammaproteobacteria HTCC2089 were enriched in the A. andraeanum rhizosphere. Endophytes were more diverse in the roots than in the shoots, whereas all shoot endophytes were found in the roots. Streptomyces, Flavobacterium succinicans, and Asteroleplasma were only found in the roots, Variovorax paradoxus only in the stem, and Fimbriimonas 97%-OTUs only in the spathe, i.e., considered specialists, while Brevibacillus, Lachnospiraceae, Pseudomonas, and Pseudomonas pseudoalcaligenes were generalist and colonized all plant parts. The anaerobic diazotrophic bacteria Lachnospiraceae, Clostridium sp., and Clostridium bifermentans colonized the shoot system. Phylotypes belonging to Pseudomonas were detected in the rhizosphere and in the substrate (an equiproportional mixture of soil, cow manure, and peat), and dominated the endosphere. Pseudomonas included nine 97%-OTUs with different patterns of distribution and phylogenetic affiliations with different species. P. pseudoalcaligenes and P. putida dominated the shoots, but were also found in the roots and rhizosphere. P. fluorescens was present in all plant parts, while P. resinovorans, P. denitrificans, P. aeruginosa, and P. stutzeri were only detected in the substrate and rhizosphere. The composition of plant-associated bacterial communities is generally considered to be suitable as an indicator of plant health.

  15. Bacterial Communities Associated with Different Anthurium andraeanum L. Plant Tissues

    PubMed Central

    Sarria-Guzmán, Yohanna; Chávez-Romero, Yosef; Gómez-Acata, Selene; Montes-Molina, Joaquín Adolfo; Morales-Salazar, Eleacin; Dendooven, Luc; Navarro-Noya, Yendi E.

    2016-01-01

    Plant-associated microbes have specific beneficial functions and are considered key drivers for plant health. The bacterial community structure of healthy Anthurium andraeanum L. plants was studied by 16S rRNA gene pyrosequencing associated with different plant parts and the rhizosphere. A limited number of bacterial taxa, i.e., Sinorhizobium, Fimbriimonadales, and Gammaproteobacteria HTCC2089 were enriched in the A. andraeanum rhizosphere. Endophytes were more diverse in the roots than in the shoots, whereas all shoot endophytes were found in the roots. Streptomyces, Flavobacterium succinicans, and Asteroleplasma were only found in the roots, Variovorax paradoxus only in the stem, and Fimbriimonas 97%-OTUs only in the spathe, i.e., considered specialists, while Brevibacillus, Lachnospiraceae, Pseudomonas, and Pseudomonas pseudoalcaligenes were generalist and colonized all plant parts. The anaerobic diazotrophic bacteria Lachnospiraceae, Clostridium sp., and Clostridium bifermentans colonized the shoot system. Phylotypes belonging to Pseudomonas were detected in the rhizosphere and in the substrate (an equiproportional mixture of soil, cow manure, and peat), and dominated the endosphere. Pseudomonas included nine 97%-OTUs with different patterns of distribution and phylogenetic affiliations with different species. P. pseudoalcaligenes and P. putida dominated the shoots, but were also found in the roots and rhizosphere. P. fluorescens was present in all plant parts, while P. resinovorans, P. denitrificans, P. aeruginosa, and P. stutzeri were only detected in the substrate and rhizosphere. The composition of plant-associated bacterial communities is generally considered to be suitable as an indicator of plant health. PMID:27524305

  16. Plant nitrogen uptake drives rhizosphere bacterial community assembly during plant growth

    Technology Transfer Automated Retrieval System (TEKTRAN)

    When plant species establish in novel environments, they often modify microbial communities and soil properties in ways that enhance their own success. Upon invasion, the C3 annual grass Bromus tectorum appears to support soil microbial communities that have higher soil nitrogen (N) mineralization r...

  17. Planting Healthy Roots: Using Documentary Film to Evaluate and Disseminate Community-Based Participatory Research.

    PubMed

    Brandt, Heather M; Freedman, Darcy A; Friedman, Daniela B; Choi, Seul Ki; Seel, Jessica S; Guest, M Aaron; Khang, Leepao

    2016-01-01

    Documentary filmmaking approaches incorporating community engagement and awareness raising strategies may be a promising approach to evaluate community-based participatory research. The study purpose was 2-fold: (1) to evaluate a documentary film featuring the formation and implementation of a farmers' market and (2) to assess whether the film affected awareness regarding food access issues in a food-desert community with high rates of obesity. The coalition model of filmmaking, a model consistent with a community-based participatory research (CBPR) approach, and personal stories, community profiles, and expert interviews were used to develop a documentary film (Planting Healthy Roots). The evaluation demonstrated high levels of approval and satisfaction with the film and CBPR essence of the film. The documentary film aligned with a CBPR approach to document, evaluate, and disseminate research processes and outcomes.

  18. Nighttime warming enhances drought resistance of plant communities in a temperate steppe

    PubMed Central

    Yang, Zhongling; Jiang, Lin; Su, Fanglong; Zhang, Qian; Xia, Jianyang; Wan, Shiqiang

    2016-01-01

    Drought events could have profound influence on plant community structure and ecosystem function, and have subsequent impacts on community stability, but we know little about how different climate warming scenarios affect community resistance and resilience to drought. Combining a daytime and nighttime warming experiment in the temperate steppe of north China with a natural drought event during the study period, we tested how daytime and nighttime warming influences drought resistance and resilience. Our results showed that the semi-arid steppe in north China was resistant to both daytime and nighttime warming, but vulnerable to drought. Nighttime warming, but not daytime warming, enhanced community resistance to drought via stimulating carbon sequestration, whereas neither daytime nor nighttime warming affected community resilience to drought. Large decline in plant community cover, primarily caused by the reduction in the cover of dominant and rare species rather than subordinate species during drought, did not preclude rapid ecosystem recovery. These findings suggest that nighttime warming may facilitate ecosystem sustainability and highlight the need to assess the effects of climate extremes on ecosystem functions at finer temporal resolutions than based on diurnal mean temperature. PMID:26987482

  19. Nighttime warming enhances drought resistance of plant communities in a temperate steppe

    NASA Astrophysics Data System (ADS)

    Yang, Zhongling; Jiang, Lin; Su, Fanglong; Zhang, Qian; Xia, Jianyang; Wan, Shiqiang

    2016-03-01

    Drought events could have profound influence on plant community structure and ecosystem function, and have subsequent impacts on community stability, but we know little about how different climate warming scenarios affect community resistance and resilience to drought. Combining a daytime and nighttime warming experiment in the temperate steppe of north China with a natural drought event during the study period, we tested how daytime and nighttime warming influences drought resistance and resilience. Our results showed that the semi-arid steppe in north China was resistant to both daytime and nighttime warming, but vulnerable to drought. Nighttime warming, but not daytime warming, enhanced community resistance to drought via stimulating carbon sequestration, whereas neither daytime nor nighttime warming affected community resilience to drought. Large decline in plant community cover, primarily caused by the reduction in the cover of dominant and rare species rather than subordinate species during drought, did not preclude rapid ecosystem recovery. These findings suggest that nighttime warming may facilitate ecosystem sustainability and highlight the need to assess the effects of climate extremes on ecosystem functions at finer temporal resolutions than based on diurnal mean temperature.

  20. Designing the School Plant as a Community Center.

    ERIC Educational Resources Information Center

    New York State Education Dept., Albany. Div. of School Buildings and Grounds.

    In the planning of school plants to serve the educational, social, civic, recreational, and cultural needs of the entire community, factors which receive special consideration are location of facilities, heat distribution, zoning, storage space, and special appointments and service features. (RH)

  1. MEDUSAHEAD DISPERSAL AND ESTABLISHMENT IN SAGEBRUSH PLANT COMMUNITIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Medusahead (Taeniatherum caput-medusae (L.) Nevski) is an invasive annual grass that that is rapidly invading sagebrush plant communities. To prevent medusahead invasion land managers need to know 1) when and how far medusahead seeds disperse and 2) its establishment rates and interactions with the...

  2. Soil nitrogen availability and plant genotype modify the nutrition strategies of M. truncatula and the associated rhizosphere microbial communities.

    PubMed

    Zancarini, Anouk; Mougel, Christophe; Voisin, Anne-Sophie; Prudent, Marion; Salon, Christophe; Munier-Jolain, Nathalie

    2012-01-01

    Plant and soil types are usually considered as the two main drivers of the rhizosphere microbial communities. The aim of this work was to study the effect of both N availability and plant genotype on the plant associated rhizosphere microbial communities, in relation to the nutritional strategies of the plant-microbe interactions, for six contrasted Medicago truncatula genotypes. The plants were provided with two different nutrient solutions varying in their nitrate concentrations (0 mM and 10 mM). First, the influence of both nitrogen availability and Medicago truncatula genotype on the genetic structure of the soil bacterial and fungal communities was determined by DNA fingerprint using Automated Ribosomal Intergenic Spacer Analysis (ARISA). Secondly, the different nutritional strategies of the plant-microbe interactions were evaluated using an ecophysiological framework. We observed that nitrogen availability affected rhizosphere bacterial communities only in presence of the plant. Furthermore, we showed that the influence of nitrogen availability on rhizosphere bacterial communities was dependent on the different genotypes of Medicago truncatula. Finally, the nutritional strategies of the plant varied greatly in response to a modification of nitrogen availability. A new conceptual framework was thus developed to study plant-microbe interactions. This framework led to the identification of three contrasted structural and functional adaptive responses of plant-microbe interactions to nitrogen availability.

  3. Earthworms drive succession of both plant and Collembola communities in post-mining sites

    NASA Astrophysics Data System (ADS)

    Mudrák, Obdřej; Frouz, Jan

    2015-04-01

    Previous field observations indicated that earthworms promote late-successional plant species and reduce collembolan numbers at post-mining sites in the Sokolov coal mining district (Czech Republic). Here, we established a laboratory pot experiment to test the effect of earthworms (Aporrectodea caliginosa Savigny and Lumbricus rubellus Hoffm.) and litter of low, medium, and high quality (the grass Calamagrostis epigejos, the willow Salix caprea, and the alder Alnus glutinosa, respectively) on late successional plants (grasses Arrhenatherum elatius and Agrostis capillaris, legumes Lotus corniculatus and Trifolium medium, and non-leguminous dicots Centaurea jacea and Plantago lanceolata) in spoil substrate originating from Sokolov post-mining sites and naturally inhabited by abundant numbers of Collembola. The earthworms increased plant biomass, especially that of the large-seeded A. elatius, but reduced the number of plant individuals, mainly that of the small-seeded A. capillaris and both legumes. Litter quality affected plant biomass, which was highest with S. caprea litter, but did not change the number of plant individuals. Litter quality did not modify the effect of earthworms on plants; the effect of litter quality and earthworms was only additive. Species composition of Collembola community was altered by litter quality, but earthworms reduced the number of individuals, increased the number of species, and increased species evenness consistently across the litter qualities. Because the results of this experiment were consistent with the field observations, we conclude that earthworms help drive succession of both plant and Collembola communities on post-mining sites.

  4. Earthworms drive succession of both plant and Collembola communities in post-mining sites

    NASA Astrophysics Data System (ADS)

    Mudrák, Ondřej; Uteseny, Karoline; Frouz, Jan

    2016-04-01

    Previous field observations indicated that earthworms promote late-successional plant species and reduce collembolan numbers at post-mining sites in the Sokolov coal mining district (Czech Republic). Here, we established a laboratory pot experiment to test the effect of earthworms (Aporrectodea caliginosa Savigny and Lumbricus rubellus Hoffm.) and litter of low, medium, and high quality (the grass Calamagrostis epigejos, the willow Salix caprea, and the alder Alnus glutinosa, respectively) on late successional plants (grasses Arrhenatherum elatius and Agrostis capillaris, legumes Lotus corniculatus and Trifolium medium, and non-leguminous dicots Centaurea jacea and Plantago lanceolata) in spoil substrate originating from Sokolov post-mining sites and naturally inhabited by abundant numbers of Collembola. The earthworms increased plant biomass, especially that of the large-seeded A. elatius, but reduced the number of plant individuals, mainly that of the small-seeded A. capillaris and both legumes. Litter quality affected plant biomass, which was highest with S. caprea litter, but did not change the number of plant individuals. Litter quality did not modify the effect of earthworms on plants; the effect of litter quality and earthworms was only additive. Species composition of Collembola community was altered by litter quality, but earthworms reduced the number of individuals, increased the number of species, and increased species evenness consistently across the litter qualities. Because the results of this experiment were consistent with the field observations, we conclude that earthworms help drive succession of both plant and Collembola communities on post-mining sites.

  5. Hierarchical organization of a Sardinian sand dune plant community

    PubMed Central

    Ceccherelli, Giulia; Bertness, Mark

    2016-01-01

    Coastal sand dunes have attracted the attention of plant ecologists for over a century, but they have largely relied on correlations to explain dune plant community organization. We examined long-standing hypotheses experimentally that sand binding, inter-specific interactions, abiotic factors and seedling recruitment are drivers of sand dune plant community structure in Sardinia, Italy. Removing foundation species from the fore-, middle- and back-dune habitats over three years led to erosion and habitat loss on the fore-dune and limited plant recovery that increased with dune elevation. Reciprocal species removals in all zones suggested that inter-specific competition is common, but that dominance is transient, particularly due to sand burial disturbance in the middle-dune. A fully factorial 2-year manipulation of water, nutrient availability and substrate stability revealed no significant proximate response to these physical factors in any dune zone. In the fore- and middle-dune, plant seeds are trapped under adult plants during seed germination, and seedling survivorship and growth generally increase with dune height in spite of increased herbivory in the back-dune. Sand and seed erosion leads to limited seed recruitment on the fore-dune while high summer temperatures and preemption of space lead to competitive dominance of woody plants in the back-dune. Our results suggest that Sardinian sand dune plant communities are organized hierarchically, structured by sand binding foundation species on the fore-dune, sand burial in the middle-dune and increasingly successful seedling recruitment, growth and competitive dominance in the back-dune. PMID:27478701

  6. Hierarchical organization of a Sardinian sand dune plant community.

    PubMed

    Cusseddu, Valentina; Ceccherelli, Giulia; Bertness, Mark

    2016-01-01

    Coastal sand dunes have attracted the attention of plant ecologists for over a century, but they have largely relied on correlations to explain dune plant community organization. We examined long-standing hypotheses experimentally that sand binding, inter-specific interactions, abiotic factors and seedling recruitment are drivers of sand dune plant community structure in Sardinia, Italy. Removing foundation species from the fore-, middle- and back-dune habitats over three years led to erosion and habitat loss on the fore-dune and limited plant recovery that increased with dune elevation. Reciprocal species removals in all zones suggested that inter-specific competition is common, but that dominance is transient, particularly due to sand burial disturbance in the middle-dune. A fully factorial 2-year manipulation of water, nutrient availability and substrate stability revealed no significant proximate response to these physical factors in any dune zone. In the fore- and middle-dune, plant seeds are trapped under adult plants during seed germination, and seedling survivorship and growth generally increase with dune height in spite of increased herbivory in the back-dune. Sand and seed erosion leads to limited seed recruitment on the fore-dune while high summer temperatures and preemption of space lead to competitive dominance of woody plants in the back-dune. Our results suggest that Sardinian sand dune plant communities are organized hierarchically, structured by sand binding foundation species on the fore-dune, sand burial in the middle-dune and increasingly successful seedling recruitment, growth and competitive dominance in the back-dune.

  7. Planting richness affects the recovery of vegetation and soil processes in constructed wetlands following disturbance.

    PubMed

    Means, Mary M; Ahn, Changwoo; Noe, Gregory B

    2017-02-01

    The resilience of constructed wetland ecosystems to severe disturbance, such as a mass herbivory eat-out or soil disturbance, remains poorly understood. In this study, we use a controlled mesocosm experiment to examine how original planting diversity affects the ability of constructed freshwater wetlands to recover structurally and functionally after a disturbance (i.e., aboveground harvesting and soil coring). We assessed if the planting richness of macrophyte species influences recovery of constructed wetlands one year after a disturbance. Mesocosms were planted in richness groups with various combinations of either 1, 2, 3, or 4 species (RG 1-4) to create a gradient of richness. Structural wetland traits measured include morphological regrowth of macrophytes, soil bulk density, soil moisture, soil %C, and soil %N. Functional wetland traits measured include above ground biomass production, soil potential denitrification, and soil potential microbial respiration. Total mesocosm cover increased along the gradient of plant richness (43.5% in RG 1 to 84.5% in RG 4) in the growing season after the disturbance, although not all planted individuals recovered. This was largely attributed to the dominance of the obligate annual species. The morphology of each species was affected negatively by the disturbance, producing shorter, and fewer stems than in the years prior to the disturbance, suggesting that the communities had not fully recovered one year after the disturbance. Soil characteristics were almost uniform across the planting richness gradient, but for a few exceptions (%C, C:N, and non-growing season soil moisture were higher slightly in RG 2). Denitrification potential (DEA) increased with increasing planting richness and was influenced by the abundance and quality of soil C. Increased open space in unplanted mesocosms and mesocosms with lower species richness increased labile C, leading to higher C mineralization rates.

  8. Community history affects the predictability of microbial ecosystem development.

    PubMed

    Pagaling, Eulyn; Strathdee, Fiona; Spears, Bryan M; Cates, Michael E; Allen, Rosalind J; Free, Andrew

    2014-01-01

    Microbial communities mediate crucial biogeochemical, biomedical and biotechnological processes, yet our understanding of their assembly, and our ability to control its outcome, remain poor. Existing evidence presents conflicting views on whether microbial ecosystem assembly is predictable, or inherently unpredictable. We address this issue using a well-controlled laboratory model system, in which source microbial communities colonize a pristine environment to form complex, nutrient-cycling ecosystems. When the source communities colonize a novel environment, final community composition and function (as measured by redox potential) are unpredictable, although a signature of the community's previous history is maintained. However, when the source communities are pre-conditioned to their new habitat, community development is more reproducible. This situation contrasts with some studies of communities of macro-organisms, where strong selection under novel environmental conditions leads to reproducible community structure, whereas communities under weaker selection show more variability. Our results suggest that the microbial rare biosphere may have an important role in the predictability of microbial community development, and that pre-conditioning may help to reduce unpredictability in the design of microbial communities for biotechnological applications.

  9. Deteriorating Farm Finances Affect Rural Banks and Communities.

    ERIC Educational Resources Information Center

    Milkove, Daniel L.; And Others

    1986-01-01

    Problem farm debts may translate into slow growth for rural communities, with local banks unable to offer credit even to credit worthy borrowers. Communities served by branches of large banking organizations are probably better off than communities served only by small independent banks. (Author)

  10. Community history affects the predictability of microbial ecosystem development

    PubMed Central

    Pagaling, Eulyn; Strathdee, Fiona; Spears, Bryan M; Cates, Michael E; Allen, Rosalind J; Free, Andrew

    2014-01-01

    Microbial communities mediate crucial biogeochemical, biomedical and biotechnological processes, yet our understanding of their assembly, and our ability to control its outcome, remain poor. Existing evidence presents conflicting views on whether microbial ecosystem assembly is predictable, or inherently unpredictable. We address this issue using a well-controlled laboratory model system, in which source microbial communities colonize a pristine environment to form complex, nutrient-cycling ecosystems. When the source communities colonize a novel environment, final community composition and function (as measured by redox potential) are unpredictable, although a signature of the community's previous history is maintained. However, when the source communities are pre-conditioned to their new habitat, community development is more reproducible. This situation contrasts with some studies of communities of macro-organisms, where strong selection under novel environmental conditions leads to reproducible community structure, whereas communities under weaker selection show more variability. Our results suggest that the microbial rare biosphere may have an important role in the predictability of microbial community development, and that pre-conditioning may help to reduce unpredictability in the design of microbial communities for biotechnological applications. PMID:23985743

  11. Assessing the diversity of bacterial communities associated with plants

    PubMed Central

    Andreote, Fernando Dini; Azevedo, João Lúcio; Araújo, Welington Luiz

    2009-01-01

    Plant–bacteria interactions result from reciprocal recognition between both species. These interactions are responsible for essential biological processes in plant development and health status. Here, we present a review of the methodologies applied to investigate shifts in bacterial communities associated with plants. A description of techniques is made from initial isolations to culture-independent approaches focusing on quantitative Polymerase Chain Reaction in real time (qPCR), Denaturing Gradient Gel Electrophoresis (DGGE), clone library construction and analysis, the application of multivariate analyses to microbial ecology data and the upcoming high throughput methodologies such as microarrays and pyrosequencing. This review supplies information about the development of traditional methods and a general overview about the new insights into bacterial communities associated with plants. PMID:24031382

  12. Belowground Controls on the Dynamics of Plant Communities

    NASA Astrophysics Data System (ADS)

    Sivandran, G.

    2013-12-01

    Arid regions are characterized by high variability in the arrival of rainfall, and species found in these areas have adapted mechanisms to ensure the capture of this scarce resource. In particular, the rooting strategies employed by vegetation can be critical to their survival. These rooting strategies also dictate the competitive outcomes within plant communities. A dynamic rooting scheme was incorporated into tRIBS+VEGGIE (a physically-based, distributed ecohydrologic model). The dynamic rooting scheme allows vegetation the freedom to alter its rooting profile in response to changes in rainfall and soil conditions, in a way that more closely mimics observed phenotypic plasticity. A simple competition-colonization model was combined with the new dynamic root scheme to explore the role of root adaptability in plant competition and landscape evolution in semi-arid environments. The influence of model representation of rooting strategy on the long term plant community composition

  13. How plants connect pollination and herbivory networks and their contribution to community stability.

    PubMed

    Sauve, Alix M C; Thébault, Elisa; Pocock, Michael J O; Fontaine, Colin

    2016-04-01

    Pollination and herbivory networks have mainly been studied separately, highlighting their distinct structural characteristics and the related processes and dynamics. However, most plants interact with both pollinators and herbivores, and there is evidence that both types of interaction affect each other. Here we investigated the way plants connect these mutualistic and antagonistic networks together, and the consequences for community stability. Using an empirical data set, we show that the way plants connect pollination and herbivory networks is not random and promotes community stability. Analyses of the structure of binary and quantitative networks show different results: the plants' generalism with regard to pollinators is positively correlated to their generalism with regard to herbivores when considering binary interactions, but not when considering quantitative interactions. We also show that plants that share the same pollinators do not share the same herbivores. However, the way plants connect pollination and herbivory networks promotes stability for both binary and quantitative networks. Our results highlight the relevance of considering the diversity of interaction types in ecological communities, and stress the need to better quantify the costs and benefits of interactions, as well as to develop new metrics characterizing the way different interaction types are combined within ecological networks.

  14. Habitat Fragmentation Drives Plant Community Assembly Processes across Life Stages

    PubMed Central

    Hu, Guang; Feeley, Kenneth J.; Yu, Mingjian

    2016-01-01

    Habitat fragmentation is one of the principal causes of biodiversity loss and hence understanding its impacts on community assembly and disassembly is an important topic in ecology. We studied the relationships between fragmentation and community assembly processes in the land-bridge island system of Thousand Island Lake in East China. We focused on the changes in species diversity and phylogenetic diversity that occurred between life stages of woody plants growing on these islands. The observed diversities were compared with the expected diversities from random null models to characterize assembly processes. Regression tree analysis was used to illustrate the relationships between island attributes and community assembly processes. We found that different assembly processes predominate in the seedlings-to-saplings life-stage transition (SS) vs. the saplings-to-trees transition (ST). Island area was the main attribute driving the assembly process in SS. In ST, island isolation was more important. Within a fragmented landscape, the factors driving community assembly processes were found to differ between life stage transitions. Environmental filtering had a strong effect on the seedlings-to-saplings life-stage transition. Habitat isolation and dispersal limitation influenced all plant life stages, but had a weaker effect on communities than area. These findings add to our understanding of the processes driving community assembly and species coexistence in the context of pervasive and widespread habitat loss and fragmentation. PMID:27427960

  15. Plant community resistance to invasion by Bromus species – the roles of community attributes, Bromus Interactions with plant communities, and Bromus traits

    USGS Publications Warehouse

    Chambers, Jeanne; Germino, Matthew; Belnap, Jayne; Brown, Cynthia; Schupp, Eugene W.; St. Clair, Samuel B

    2016-01-01

    The factors that determine plant community resistance to exotic annual Bromus species (Bromushereafter) are diverse and context specific. They are influenced by the environmental characteristics and attributes of the community, the traits of Bromus species, and the direct and indirect interactions of Bromus with the plant community. Environmental factors, in particular ambient and soil temperatures, have significant effects on the ability of Bromus to establish and spread. Seasonality of precipitation relative to temperature influences plant community resistance toBromus through effects on soil water storage, timing of water and nutrient availability, and dominant plant life forms. Differences among plant communities in how well soil resource use by the plant community matches resource supply rates can influence the magnitude of resource fluctuations due to either climate or disturbance and thus the opportunities for invasion. The spatial and temporal patterns of resource availability and acquisition of growth resources by Bromus versus native species strongly influence resistance to invasion. Traits of Bromus that confer a “priority advantage” for resource use in many communities include early-season germination and high growth and reproductive rates. Resistance to Bromus can be overwhelmed by high propagule supply, low innate seed dormancy, and large, if short-lived, seed banks. Biological crusts can inhibit germination and establishment of invasive annual plants, including several annual Bromus species, but are effective only in the absence of disturbance. Herbivores can have negative direct effects on Bromus, but positive indirect effects through decreases in competitors. Management strategies can be improved through increased understanding of community resistance to exotic annual Bromus species.

  16. Ethnobotany of dye plants in Dong communities of China

    PubMed Central

    2014-01-01

    Background Dyes derived from plants have an extensive history of use for coloring food and clothing in Dong communities and other indigenous areas in the uplands of China. In addition to use as coloring agents, Dong communities have historically utilized dye plants for their value for enhancing the nutritive, medicinal and preservative properties of foods. However, the persistence of plant-derived dyes and associated cultural practices and traditional knowledge is threatened with rapid socio-economic change in China. Research is needed to document the ethnobotany of dye plants in indigenous communities towards their conservation and potential commercialization as a sustainable means of supporting local development initiatives. Methods Semi-structured surveys on plants used for coloring agents and associated traditional knowledge were conducted in fifteen Dong villages of Tongdao County in Hunan Province of South Central China during 2011–2012. Transect walks were carried out with key informants identified from semi-structured surveys to collect samples and voucher specimens for each documented plant species for taxonomic identification. Results Dong households at the study sites utilize the flowers, bark, stems, tubers and roots of 13 plant species from 9 families as dyes to color their customary clothing and food. Out of the documented plants, a total of 7 are used for coloring food, 3 for coloring clothing and 3 for both food and clothing. Documented plants consist of 3 species that yield black pigments, 3 for brownish red/russet pigments, 3 for red pigments, 2 for dark blue pigments and 2 for yellow pigments. In addition to dyes, the plants have multiple uses including medicinal, ornamental, sacrificial, edible, and for timber. Conclusions The use of dyes derived from plants persists at the study sites for their important role in expressing Dong cultural identity through customary clothing and food. Further research is needed to evaluate the safety of dye

  17. [A phylogenetic analysis of plant communities of Teberda Biosphere Reserve].

    PubMed

    Shulakov, A A; Egorov, A V; Onipchenko, V G

    2016-01-01

    Phylogenetic analysis of communities is based on the comparison of distances on the phylogenetic tree between species of a community under study and those distances in random samples taken out of local flora. It makes it possible to determine to what extent a community composition is formed by more closely related species (i.e., "clustered") or, on the opposite, it is more even and includes species that are less related with each other. The first case is usually interpreted as a result of strong influence caused by abiotic factors, due to which species with similar ecology, a priori more closely related, would remain: In the second case, biotic factors, such as competition, may come to the fore and lead to forming a community out of distant clades due to divergence of their ecological niches: The aim of this' study Was Ad explore the phylogenetic structure in communities of the northwestern Caucasus at two spatial scales - the scale of area from 4 to 100 m2 and the smaller scale within a community. The list of local flora of the alpine belt has been composed using the database of geobotanic descriptions carried out in Teberda Biosphere Reserve at true altitudes exceeding.1800 m. It includes 585 species of flowering plants belonging to 57 families. Basal groups of flowering plants are.not represented in the list. At the scale of communities of three classes, namely Thlaspietea rotundifolii - commumties formed on screes and pebbles, Calluno-Ulicetea - alpine meadow, and Mulgedio-Aconitetea subalpine meadows, have not demonstrated significant distinction of phylogenetic structure. At intra level, for alpine meadows the larger share of closely related species. (clustered community) is detected. Significantly clustered happen to be those communities developing on rocks (class Asplenietea trichomanis) and alpine (class Juncetea trifidi). At the same time, alpine lichen proved to have even phylogenetic structure at the small scale. Alpine (class Salicetea herbaceae) that

  18. Carbon storage potential by four macrophytes as affected by planting diversity in a created wetland.

    PubMed

    Means, Mary M; Ahn, Changwoo; Korol, Alicia R; Williams, Lisa D

    2016-01-01

    Wetland creation has become a commonplace method for mitigating the loss of natural wetlands. Often mitigation projects fail to restore ecosystem services of the impacted natural wetlands. One of the key ecosystem services of newly created wetlands is carbon accumulation/sequestration, but little is known about how planting diversity (PD) affects the ability of herbaceous wetland plants to store carbon in newly created wetlands. Most mitigation projects involve a planting regime, but PD, which may be critical in establishing biologically diverse and ecologically functioning wetlands, is seldom required. Using a set of 34 mesocosms (∼1 m(2) each), we investigated the effects of planting diversity on carbon storage potential of four native wetland plant species that are commonly planted in created mitigation wetlands in Virginia - Carex vulpinoidea, Eleocharis obtusa, Juncus effusus, and Mimulus ringens. The plants were grown under the four distinctive PD treatments [i.e., monoculture (PD 1) through four different species mixture (PD 4)]. Plant biomass was harvested after two growing seasons and analyzed for tissue carbon content. Competition values (CV) were calculated to understand how the PD treatment affected the competitive ability of plants relative to their biomass production and thus carbon storage potentials. Aboveground biomass ranged from 988 g/m(2) - 1515 g/m(2), being greatest in monocultures, but only when compared to the most diverse mixture (p = 0.021). However, carbon storage potential estimates per mesocosm ranged between 344 g C/m(2) in the most diverse mesocosms (PD 4) to 610 g C/m(2) in monoculture ones with no significant difference (p = 0.089). CV of E. obtusa and C. vulpinoidea showed a declining trend when grown in the most diverse mixtures but J. effusus and M. ringens displayed no difference across the PD gradient (p = 0.910). In monocultures, both M. ringens, and J. effusus appeared to store carbon as biomass more

  19. Homestead tree planting in two rural Swazi communities

    USGS Publications Warehouse

    Allen, James A.

    1990-01-01

    Tree planting practices were investigated on a total of 95 homesteads in two communities in rural Swaziland. Information was also collected on socioeconomic characteristics of the homesteads. In both the study areas, Sigombeni and Bhekinkosi, there was considerable variation amongst individual homesteads in size, relative wealth (as indicated by cattle and motor vehicle ownership), and amount and types of trees planted. Eighty-five percent of all homesteads in Sigombeni and 73% in Bhekinkosi had planted at least one tree. Common forms of planting included small woodlots, fruit trees, and ornamentals. Virtually all the woodlots consisted of two introduced wattle species (Acacia mearnsii and A. decurrens). The most commonly planted fruit trees were avocados, bananas, and peaches. No complex or labor-intensive agroforestry practices (such as maize/leucaena intercropping) were observed. There was some evidence that the poorest and newest homesteads were the least likely to have planted any trees and that the richest homesteads were the most likely to have planted woodlots. The results indicate that forestry research and extension efforts should take into account homestead characteristics, and strive to offer a range of tree planting options that vary in input requirements, labor needs, and complexity.

  20. Effects of Plant Genotype and Growth Stage on the Betaproteobacterial Communities Associated with Different Potato Cultivars in Two Fields▿ †

    PubMed Central

    İnceoğlu, Özgül; Salles, Joana Falcão; van Overbeek, Leo; van Elsas, Jan Dirk

    2010-01-01

    Bacterial communities in the rhizosphere are dynamic and susceptible to changes in plant conditions. Among the bacteria, the betaproteobacteria play key roles in nutrient cycling and plant growth promotion, and hence the dynamics of their community structures in the rhizosphere should be investigated. Here, the effects of plant cultivar, growth stage, and soil type on the communities associated with potato cultivars Aveka, Aventra, Karnico, Modena, Premiere, and Désirée were assessed for two different fields containing sandy soil with either a high or low organic compound content. Thus, bacterial and betaproteobacterial PCR-denaturing gradient gel electrophoresis analyses were performed to analyze the effects of plant cultivar and growth on the rhizosphere community structure. The analyses showed that in both fields all cultivars had a rhizosphere effect on the total bacterial and betaproteobacterial communities. In addition, the plant growth stage strongly affected the betaproteobacterial communities in both fields. Moreover, the community structures were affected by cultivar, and cultivars differed in physiology, as reflected in their growth rates, root development, and estimated tuber starch contents. Analyses of betaproteobacterial clone libraries constructed for two selected cultivars (one cultivar that produced low-starch-content tubers and one cultivar that produced high-starch-content tubers), as well as bulk soil, revealed that the rhizospheres of the two cultivars selected for specific bacteria, including plant-growth-promoting bacteria, such as Variovorax and Achromobacter spp. In addition, quantitative PCR-based quantification of the Variovorax paradoxus-specific functional gene asfA (involved in desulfonation) indicated that there were clear potato rhizosphere effects on the abundance of this gene. Interestingly, both cultivar type and plant growth stage affected the community under some circumstances. PMID:20363788

  1. Effects of plant genotype and growth stage on the betaproteobacterial communities associated with different potato cultivars in two fields.

    PubMed

    Inceoğlu, Ozgül; Salles, Joana Falcão; van Overbeek, Leo; van Elsas, Jan Dirk

    2010-06-01

    Bacterial communities in the rhizosphere are dynamic and susceptible to changes in plant conditions. Among the bacteria, the betaproteobacteria play key roles in nutrient cycling and plant growth promotion, and hence the dynamics of their community structures in the rhizosphere should be investigated. Here, the effects of plant cultivar, growth stage, and soil type on the communities associated with potato cultivars Aveka, Aventra, Karnico, Modena, Premiere, and Désirée were assessed for two different fields containing sandy soil with either a high or low organic compound content. Thus, bacterial and betaproteobacterial PCR-denaturing gradient gel electrophoresis analyses were performed to analyze the effects of plant cultivar and growth on the rhizosphere community structure. The analyses showed that in both fields all cultivars had a rhizosphere effect on the total bacterial and betaproteobacterial communities. In addition, the plant growth stage strongly affected the betaproteobacterial communities in both fields. Moreover, the community structures were affected by cultivar, and cultivars differed in physiology, as reflected in their growth rates, root development, and estimated tuber starch contents. Analyses of betaproteobacterial clone libraries constructed for two selected cultivars (one cultivar that produced low-starch-content tubers and one cultivar that produced high-starch-content tubers), as well as bulk soil, revealed that the rhizospheres of the two cultivars selected for specific bacteria, including plant-growth-promoting bacteria, such as Variovorax and Achromobacter spp. In addition, quantitative PCR-based quantification of the Variovorax paradoxus-specific functional gene asfA (involved in desulfonation) indicated that there were clear potato rhizosphere effects on the abundance of this gene. Interestingly, both cultivar type and plant growth stage affected the community under some circumstances.

  2. The role of large predators in maintaining riparian plant communities and river morphology

    NASA Astrophysics Data System (ADS)

    Beschta, Robert L.; Ripple, William J.

    2012-07-01

    Studies assessing the potential for large predators to affect, via trophic cascades, the dynamics of riparian plant communities and the morphology of river channels have been largely absent in the scientific literature. Herein, we consider the results of recent studies involving three national parks in the western United States: Yellowstone, Olympic, and Zion. Within each park, key large predators were extirpated or displaced in the early 1900s and subsequent browsing pressure by native ungulates initiated long-term declines in recruitment (i.e., growth of seedlings/sprouts into tall saplings and trees) of palatable woody species and impairment of other resources. Channel responses to browsing-suppressed riparian vegetation included increased widths of active channels via accelerated bank erosion, erosion of floodplains and erraces, increased area of unvegetated alluvium, channel incision, and increased braiding. A reduced frequency of overbank flows indicated these rivers have become increasingly disconnected from historical floodplains because of channel widening/incision. Results from Zion National Park also identified major biodiversity affects (e.g., reduced abundance of plant and animal species). Although these studies were conducted in national parks, results may have implications concerning riparian plant communities, biodiversity, and channel morphology for streams and rivers draining other public lands in the western US. It is on these lands that native and introduced ungulates have often heavily utilized riparian areas, largely in the absence of key predators, with significant consequences to plant communities and channels.

  3. Phylogenetic plant community structure along elevation is lineage specific

    PubMed Central

    Ndiribe, Charlotte; Pellissier, Loïc; Antonelli, Silvia; Dubuis, Anne; Pottier, Julien; Vittoz, Pascal; Guisan, Antoine; Salamin, Nicolas

    2013-01-01

    The trend of closely related taxa to retain similar environmental preferences mediated by inherited traits suggests that several patterns observed at the community scale originate from longer evolutionary processes. While the effects of phylogenetic relatedness have been previously studied within a single genus or family, lineage-specific effects on the ecological processes governing community assembly have rarely been studied for entire communities or flora. Here, we measured how community phylogenetic structure varies across a wide elevation gradient for plant lineages represented by 35 families, using a co-occurrence index and net relatedness index (NRI). We propose a framework that analyses each lineage separately and reveals the trend of ecological assembly at tree nodes. We found prevailing phylogenetic clustering for more ancient nodes and overdispersion in more recent tree nodes. Closely related species may thus rapidly evolve new environmental tolerances to radiate into distinct communities, while older lineages likely retain inherent environmental tolerances to occupy communities in similar environments, either through efficient dispersal mechanisms or the exclusion of older lineages with more divergent environmental tolerances. Our study illustrates the importance of disentangling the patterns of community assembly among lineages to better interpret the ecological role of traits. It also sheds light on studies reporting absence of phylogenetic signal, and opens new perspectives on the analysis of niche and trait conservatism across lineages. PMID:24455126

  4. Characterizing photosynthesis and transpiration of plant communities in controlled environments

    NASA Technical Reports Server (NTRS)

    Monje, O.; Bugbee, B.

    1996-01-01

    CO2 and water vapor fluxes of hydroponically grown wheat and soybean canopies were measured continuously in several environments with an open gas exchange system. Canopy CO2 fluxes reflect the photosynthetic efficiency of a plant community, and provide a record of plant growth and health. There were significant diurnal fluctuations in root and shoot CO2 fluxes, and in shoot water vapor fluxes. Canopy stomatal conductance (Gc) to water vapor was calculated from simultaneous measurements of canopy temperature (Tcan) and transpiration rates (Tr). Tr in the dark was substantial, and there were large diurnal fluctuations in both Gc and Tr. Canopy net Photosynthesis (Pnet), Tr, and Gc increased with increasing net radiation. Gc increased with Tr, suggesting that the stomata of plants in controlled environments (CEs) behave differently from field-grown plants. A transpiration model based on measurements of Gc was developed for CEs. The model accurately predicted Tr from a soybean canopy.

  5. Plant Community Responses to Simultaneous Changes in Temperature, Nitrogen Availability, and Invasion

    PubMed Central

    Gornish, Elise S.; Miller, Thomas E.

    2015-01-01

    Background Increasing rates of change in climate have been observed across the planet and have contributed to the ongoing range shifts observed for many species. Although ecologists are now using a variety of approaches to study how much and through what mechanisms increasing temperature and nutrient pollution may influence the invasions inherent in range shifts, accurate predictions are still lacking. Methods and Results In this study, we conducted a factorial experiment, simultaneously manipulating warming, nitrogen addition and introduction of Pityopsis aspera, to determine how range-shifting species affect a plant community. We quantified the resident community using ordination scores, then used structural equation modeling to examine hypotheses related to how plants respond to a network of experimental treatments and environmental variables. Variation in soil pH explained plant community response to nitrogen addition in the absence of invasion. However, in the presence of invasion, the direct effect of nitrogen on the community was negligible and soil moisture was important for explaining nitrogen effects. We did not find effects of warming on the native plant community in the absence of invasion. In the presence of invasion, however, warming had negative effects on functional richness directly and invasion and herbivory explained the overall positive effect of warming on the plant community. Conclusions and Significance This work highlights the variation in the biotic and abiotic factors responsible for explaining independent and collective climate change effects over a short time scale. Future work should consider the complex and non-additive relationships among factors of climate change and invasion in order to capture more ecologically relevant features of our changing environment. PMID:25879440

  6. Cascading effects of fire retardant on plant-microbe interactions, community composition, and invasion.

    PubMed

    Marshall, Abigail; Waller, Lauren; Lekberg, Ylva

    2016-06-01

    Climate change, historical fire suppression, and a rise in human movements in urban-forest boundaries have resulted in an increased use of long-term fire retardant (LTFR). While LTFR is an effective fire-fighting tool, it contains high concentrations of nitrogen and phosphorus, and little is known about how this nutrient pulse affects terrestrial ecosystems. We used field surveys and greenhouse experiments to quantify effects of LTFR on plant productivity, community composition, and plant interactions with the ubiquitous root symbiont arbuscular mycorrhizal fungi (AMF). In the field, LTFR applications were associated with persistent shifts in plant communities toward exotic annuals with little or no dependency of AMF. Plants exposed to LTFR were less colonized by AMF, both in field surveys and in the greenhouse, and this was most likely due to the substantial and persistent increase in soil available phosphorus. All plants grew bigger with LTFR in the greenhouse, but the invasive annual cheatgrass (Bromus tectorum) benefitted most. While LTFR can control fires, it may cause long-term changes in soil nutrient availabilities, disrupt plant interactions with beneficial soil microbes, and exasperate invasion by some exotic plants.

  7. Pollution-induced community tolerance to non-steroidal anti-inflammatory drugs (NSAIDs) in fluvial biofilm communities affected by WWTP effluents.

    PubMed

    Corcoll, Natàlia; Acuña, Vicenç; Barceló, Damià; Casellas, Maria; Guasch, Helena; Huerta, Belinda; Petrovic, Mira; Ponsatí, Lidia; Rodríguez-Mozaz, Sara; Sabater, Sergi

    2014-10-01

    We assessed the tolerance acquired by stream biofilms to two non-steroidal anti-inflammatory-drugs (NSAIDs), ibuprofen and diclofenac. Biofilms came from a stream system receiving the effluent of a wastewater treatment plant (WWTP). The response of biofilms from a non-polluted site (upstream the WWTP) was compared to that of others downstream with relevant and decreasing levels of NSAIDs. Experiments performed in the laboratory following the pollution-induced community tolerance (PICT) approach determined that both algae and microbial communities from biofilms of the sites exposed at the highest concentrations of ibuprofen and diclofenac acquired tolerance to the mixture of these NSAIDs occurring at the sites. It was also observed that the chronic pollution by the WWTP effluent affected the microbial metabolic profile, as well as the structure of the algal community. The low (at ng L(-1) level) but chronic inputs of pharmaceuticals to the river ecosystem result in tolerant communities of lower diversity and altered microbial metabolism.

  8. Prey community structure affects how predators select for Mullerian mimicry.

    PubMed

    Ihalainen, Eira; Rowland, Hannah M; Speed, Michael P; Ruxton, Graeme D; Mappes, Johanna

    2012-06-07

    Müllerian mimicry describes the close resemblance between aposematic prey species; it is thought to be beneficial because sharing a warning signal decreases the mortality caused by sampling by inexperienced predators learning to avoid the signal. It has been hypothesized that selection for mimicry is strongest in multi-species prey communities where predators are more prone to misidentify the prey than in simple communities. In this study, wild great tits (Parus major) foraged from either simple (few prey appearances) or complex (several prey appearances) artificial prey communities where a specific model prey was always present. Owing to slower learning, the model did suffer higher mortality in complex communities when the birds were inexperienced. However, in a subsequent generalization test to potential mimics of the model prey (a continuum of signal accuracy), only birds that had foraged from simple communities selected against inaccurate mimics. Therefore, accurate mimicry is more likely to evolve in simple communities even though predator avoidance learning is slower in complex communities. For mimicry to evolve, prey species must have a common predator; the effective community consists of the predator's diet. In diverse environments, the limited diets of specialist predators could create 'simple community pockets' where accurate mimicry is selected for.

  9. Taxonomic homogenization of woodland plant communities over 70 years.

    PubMed

    Keith, Sally A; Newton, Adrian C; Morecroft, Michael D; Bealey, Clive E; Bullock, James M

    2009-10-07

    Taxonomic homogenization (TH) is the increasing similarity of the species composition of ecological communities over time. Such homogenization represents a form of biodiversity loss and can result from local species turnover. Evidence for TH is limited, reflecting a lack of suitable historical datasets, and previous analyses have generated contrasting conclusions. We present an analysis of woodland patches across a southern English county (Dorset) in which we quantified 70 years of change in the composition of vascular plant communities. We tested the hypotheses that over this time patches decreased in species richness, homogenized, or shifted towards novel communities. Although mean species richness at the patch scale did not change, we found increased similarity in species composition among woodlands over time. We concluded that the woodlands have undergone TH without experiencing declines in local diversity or shifts towards novel communities. Analysis of species characteristics suggested that these changes were not driven by non-native species invasions or climate change, but instead reflected reorganization of the native plant communities in response to eutrophication and increasingly shaded conditions. These analyses provide, to our knowledge, the first direct evidence of TH in the UK and highlight the potential importance of this phenomenon as a contributor to biodiversity loss.

  10. Diversity of Riparian Plants among and within Species Shapes River Communities

    PubMed Central

    Jackrel, Sara L.; Wootton, J. Timothy

    2015-01-01

    Organismal diversity among and within species may affect ecosystem function with effects transmitting across ecosystem boundaries. Whether recipient communities adjust their composition, in turn, to maximize their function in response to changes in donor composition at these two scales of diversity is unknown. We use small stream communities that rely on riparian subsidies as a model system. We used leaf pack experiments to ask how variation in plants growing beside streams in the Olympic Peninsula of Washington State, USA affects stream communities via leaf subsidies. Leaves from red alder (Alnus rubra), vine maple (Acer cinereus), bigleaf maple (Acer macrophyllum) and western hemlock (Tsuga heterophylla) were assembled in leaf packs to contrast low versus high diversity, and deployed in streams to compare local versus non-local leaf sources at the among and within species scales. Leaves from individuals within species decomposed at varying rates; most notably thin leaves decomposed rapidly. Among deciduous species, vine maple decomposed most rapidly, harbored the least algal abundance, and supported the greatest diversity of aquatic invertebrates, while bigleaf maple was at the opposite extreme for these three metrics. Recipient communities decomposed leaves from local species rapidly: leaves from early successional plants decomposed rapidly in stream reaches surrounded by early successional forest and leaves from later successional plants decomposed rapidly adjacent to later successional forest. The species diversity of leaves inconsistently affected decomposition, algal abundance and invertebrate metrics. Intraspecific diversity of leaf packs also did not affect decomposition or invertebrate diversity. However, locally sourced alder leaves decomposed more rapidly and harbored greater levels of algae than leaves sourced from conspecifics growing in other areas on the Olympic Peninsula, but did not harbor greater aquatic invertebrate diversity. In contrast to

  11. Diversity of Riparian Plants among and within Species Shapes River Communities.

    PubMed

    Jackrel, Sara L; Wootton, J Timothy

    2015-01-01

    Organismal diversity among and within species may affect ecosystem function with effects transmitting across ecosystem boundaries. Whether recipient communities adjust their composition, in turn, to maximize their function in response to changes in donor composition at these two scales of diversity is unknown. We use small stream communities that rely on riparian subsidies as a model system. We used leaf pack experiments to ask how variation in plants growing beside streams in the Olympic Peninsula of Washington State, USA affects stream communities via leaf subsidies. Leaves from red alder (Alnus rubra), vine maple (Acer cinereus), bigleaf maple (Acer macrophyllum) and western hemlock (Tsuga heterophylla) were assembled in leaf packs to contrast low versus high diversity, and deployed in streams to compare local versus non-local leaf sources at the among and within species scales. Leaves from individuals within species decomposed at varying rates; most notably thin leaves decomposed rapidly. Among deciduous species, vine maple decomposed most rapidly, harbored the least algal abundance, and supported the greatest diversity of aquatic invertebrates, while bigleaf maple was at the opposite extreme for these three metrics. Recipient communities decomposed leaves from local species rapidly: leaves from early successional plants decomposed rapidly in stream reaches surrounded by early successional forest and leaves from later successional plants decomposed rapidly adjacent to later successional forest. The species diversity of leaves inconsistently affected decomposition, algal abundance and invertebrate metrics. Intraspecific diversity of leaf packs also did not affect decomposition or invertebrate diversity. However, locally sourced alder leaves decomposed more rapidly and harbored greater levels of algae than leaves sourced from conspecifics growing in other areas on the Olympic Peninsula, but did not harbor greater aquatic invertebrate diversity. In contrast to

  12. Use and management of traditional medicinal plants by Maale and Ari ethnic communities in southern Ethiopia

    PubMed Central

    2014-01-01

    Background Around 80% of the people of Ethiopia are estimated to be relying on medicinal plants for the treatment of different types of human health problems. The purpose of this study was to describe and analyse the use and management of medicinal plants used for the treatment of human health problems by the Maale and Ari communities in southern Ethiopia. Methods Quantitative and qualitative ethnobotanical field inquiries and analytical methods including individual and focus group discussions (18), observations, individual interviews (n = 74), preference ranking and paired comparison were used. Data were collected in three study sites and from two markets; the latter surveyed every 15 days from February 2011 to February 2012. Results A total of 128 medicinal plant species, belonging to 111 genera and 49 families, used as herbal medicine by Maale and Ari communities were documented. Predominantly harvested plant parts were leaves, which are known to have relatively low impact on medicinal plant resources. Species with high familiarity indices included Solanum dasyphyllum, Indigofera spicata, Ruta chalepensis, Plumbago zeylanica and Meyna tetraphylla. Low Jaccards similarity indices (≤ 0.33) indicated little correspondence in medicinal plant use among sites and between ethnic communities. The dominant ways of medicinal plant knowledge acquisition and transfer is vertical: from parents to children through oral means. Gender and site significantly influenced the number of human medicinal plants known currently in the study sites. Age was only a factor of significance in Maale. Marketing of medicinal plants harvested from wild and semi-wild stands is not common. Expansion of agricultural land and lack of cultivation efforts by local communities are mentioned by locals to affect the availability of medicinal plant resources. Conclusion S. dasyphyllum, I. spicata, P. zeylanica, M. tetraphylla, and Oxalis radicosa need to be considered for phytochemical and

  13. Plant community composition and vegetation height, Barrow, Alaska, Ver. 1

    DOE Data Explorer

    Sloan, Victoria; Norby, Richard; Siegrist, Julia; Iversen, Colleen; Brooks, Jonathan; Liebig, Jennifer; Wood, Sarah

    2014-04-25

    This dataset contains i) the results of field surveys of plant community composition and vegetation height made between 17th and 29th July 2012 in 48, 1 x 1 m plots located in areas A-D of Intensive Site 1 at the Next-Generation Ecosystem Experiments (NGEE) Arctic site near Barrow, Alaska and ii) results of a mapping exercise undertaken in August 2013 using two perpendicular transects across each polygon containing vegetation plots to determine the boundaries of vegetation communities described in 2012.

  14. Community Violence and Youth: Affect, Behavior, Substance Use, and Academics

    ERIC Educational Resources Information Center

    Cooley-Strickland, Michele; Quille, Tanya J.; Griffin, Robert S.; Stuart, Elizabeth A.; Bradshaw, Catherine P.; Furr-Holden, Debra

    2009-01-01

    Community violence is recognized as a major public health problem (WHO, "World Report on Violence and Health," 2002) that Americans increasingly understand has adverse implications beyond inner-cities. However, the majority of research on chronic community violence exposure focuses on ethnic minority, impoverished, and/or crime-ridden communities…

  15. The factors controlling species density in herbaceous plant communities: An assessment

    USGS Publications Warehouse

    Grace, J.B.

    1999-01-01

    This paper evaluates both the ideas and empirical evidence pertaining to the control of species density in herbaceous plant communities. While most theoretical discussions of species density have emphasized the importance of habitat productivity and disturbance regimes, many other factors (e.g. species pools, plant litter accumulation, plant morphology) have been proposed to be important. A review of literature presenting observations on the density of species in small plots (in the vicinity of a few square meters or less), as well as experimental studies, suggests several generalizations: (1) Available data are consistent with an underlying unimodal relationship between species density and total community biomass. While variance in species density is often poorly explained by predictor variables, there is strong evidence that high levels of community biomass are antagonistic to high species density. (2) Community biomass is just one of several factors affecting variations in species density. Multivariate analyses typically explain more than twice as much variance in species density as can be explained by community biomass alone. (3) Disturbance has important and sometimes complex effects on species density. In general, the evidence is consistent with the intermediate disturbance hypothesis but exceptions exist and effects can be complex. (4) Gradients in the species pool can have important influences on patterns of species density. Evidence is mounting that a considerable amount of the observed variability in species density within a landscape or region may result from environmental effects on the species pool. (5) Several additional factors deserve greater consideration, including time lags, species composition, plant morphology, plant density and soil microbial effects. Based on the available evidence, a conceptual model of the primary factors controlling species density is presented here. This model suggests that species density is controlled by the effects of

  16. Plant community and white-tailed deer nutritional carrying capacity response to intercropping switchgrass in loblolly pine plantations

    NASA Astrophysics Data System (ADS)

    Greene, Ethan Jacob

    Switchgrass (Panicum virgatum L.) is a cellulosic feedstock for alternative energy production that could grow well between planted pines (Pinus spp.). Southeastern planted pine occupies 15.8 million hectares and thus, switchgrass intercropping could affect biodiversity if broadly implemented. Therefore, I evaluated effects of intercropping switchgrass in loblolly pine (P. taeda L.) plantations on plant community diversity, plant biomass production, and white-tailed deer (Odocoileus virginianus Zimmerman) nutritional carrying capacity. In a randomized complete block design, I assigned three treatments (switchgrass intercropped, switchgrass monoculture, and a "control" of traditional pine management) to 4 replicates of 10-ha experimental units in Kemper County, Mississippi during 2014-2015. I detected 246 different plant species. Switchgrass intercropping reduced plant species richness and diversity but maintained evenness. I observed reduced forb and high-use deer forage biomass but only in intercropped alleys (interbeds). Soil micronutrient interactions affected forage protein of deer plants. White-tailed deer nutritional carrying capacity remained unaffected.

  17. Host tree phenology affects vascular epiphytes at the physiological, demographic and community level

    PubMed Central

    Einzmann, Helena J. R.; Beyschlag, Joachim; Hofhansl, Florian; Wanek, Wolfgang; Zotz, Gerhard

    2015-01-01

    The processes that govern diverse tropical plant communities have rarely been studied in life forms other than trees. Structurally dependent vascular epiphytes, a major part of tropical biodiversity, grow in a three-dimensional matrix defined by their hosts, but trees differ in their architecture, bark structure/chemistry and leaf phenology. We hypothesized that the resulting seasonal differences in microclimatic conditions in evergreen vs. deciduous trees would affect epiphytes at different levels, from organ physiology to community structure. We studied the influence of tree leaf phenology on vascular epiphytes on the Island of Barro Colorado, Panama. Five tree species were selected, which were deciduous, semi-deciduous or evergreen. The crowns of drought-deciduous trees, characterized by sunnier and drier microclimates, hosted fewer individuals and less diverse epiphyte assemblages. Differences were also observed at a functional level, e.g. epiphyte assemblages in deciduous trees had larger proportions of Crassulacean acid metabolism species and individuals. At the population level a drier microclimate was associated with lower individual growth and survival in a xerophytic fern. Some species also showed, as expected, lower specific leaf area and higher δ13C values when growing in deciduous trees compared with evergreen trees. As hypothesized, host tree leaf phenology influences vascular epiphytes at different levels. Our results suggest a cascading effect of tree composition and associated differences in tree phenology on the diversity and functioning of epiphyte communities in tropical lowland forests. PMID:25392188

  18. Host tree phenology affects vascular epiphytes at the physiological, demographic and community level.

    PubMed

    Einzmann, Helena J R; Beyschlag, Joachim; Hofhansl, Florian; Wanek, Wolfgang; Zotz, Gerhard

    2014-11-11

    The processes that govern diverse tropical plant communities have rarely been studied in life forms other than trees. Structurally dependent vascular epiphytes, a major part of tropical biodiversity, grow in a three-dimensional matrix defined by their hosts, but trees differ in their architecture, bark structure/chemistry and leaf phenology. We hypothesized that the resulting seasonal differences in microclimatic conditions in evergreen vs. deciduous trees would affect epiphytes at different levels, from organ physiology to community structure. We studied the influence of tree leaf phenology on vascular epiphytes on the Island of Barro Colorado, Panama. Five tree species were selected, which were deciduous, semi-deciduous or evergreen. The crowns of drought-deciduous trees, characterized by sunnier and drier microclimates, hosted fewer individuals and less diverse epiphyte assemblages. Differences were also observed at a functional level, e.g. epiphyte assemblages in deciduous trees had larger proportions of Crassulacean acid metabolism species and individuals. At the population level a drier microclimate was associated with lower individual growth and survival in a xerophytic fern. Some species also showed, as expected, lower specific leaf area and higher δ(13)C values when growing in deciduous trees compared with evergreen trees. As hypothesized, host tree leaf phenology influences vascular epiphytes at different levels. Our results suggest a cascading effect of tree composition and associated differences in tree phenology on the diversity and functioning of epiphyte communities in tropical lowland forests.

  19. Wetland plant communities, Galveston Bay system. Final report

    SciTech Connect

    White, W.A.; Paine, J.G.

    1992-03-01

    The report is the culmination of a field investigation of wetland plant communities, and is one phase of the project, Trends and Status of Wetland and Aquatic Habitats of the Galveston Bay System, Texas, sponsored by the Galveston Bay National Estuary Program. For purpose of the topical report, wetlands are defined and classified in terms of more classical definitions, for example, salt, brackish, and fresh marshes, in accordance with project requirements. More than 150 sites were examined in the Galveston Bay system.

  20. Extrafloral nectaries alter arthropod community structure and mediate peach (Prunus persica) plant defense.

    PubMed

    Mathews, Clarissa R; Bottrell, Dale G; Brown, Mark W

    2009-04-01

    We investigated the role of extrafloral nectaries (EFNs) in mediating plant defense for newly established peach (Prunus persica) trees. We used peaches of a single cultivar ("Lovell") that varied with respect to EFN leaf phenotype (with or without EFNs) to determine if the EFNs affected the structure of the arthropod community colonizing newly planted seedlings. We also tested if the plants producing EFNs benefited from reduced herbivory or enhanced productivity. In the first year following planting, the young peach trees with EFNs were dominated by ants, and arthropod community diversity was lower than for trees without EFNs. The young trees with EFNs harbored fewer herbivores and experienced a twofold reduction in folivory compared to trees without EFNs. Productivity was also enhanced for the trees with EFNs, which attained significantly higher rates of trunk growth, greater terminal carbon composition, and a threefold increase in buds produced in subsequent years. In the second year of the field study, ants remained numerically dominant on trees with EFNs, but arthropod community diversity was higher than for trees without EFNs. An additional study revealed that folivory rates in May increased dramatically for trees with EFNs if ants were excluded from their canopies, indicating that ants have a protective function when the perennial trees produce new leaves. However, in later months, regardless of ants' presence, the trees with EFNs suffered less folivory than trees lacking EFNs. The diversity and richness of the predator trophic group increased when ants were excluded from trees with EFNs, but overall community diversity (i.e., herbivores and predators combined) was not affected by the ants' presence. Our research indicates that the EFNs play an important role in attracting predators that protect the trees from herbivores, and the EFN host-plant characteristic should be retained in future peach cultivar selections. Furthermore, peach production programs aimed

  1. Resource colimitation governs plant community responses to altered precipitation

    PubMed Central

    Eskelinen, Anu; Harrison, Susan P.

    2015-01-01

    Ecological theory and evidence suggest that plant community biomass and composition may often be jointly controlled by climatic water availability and soil nutrient supply. To the extent that such colimitation operates, alterations in water availability caused by climatic change may have relatively little effect on plant communities on nutrient-poor soils. We tested this prediction with a 5-y rainfall and nutrient manipulation in a semiarid annual grassland system with highly heterogeneous soil nutrient supplies. On nutrient-poor soils, rainfall addition alone had little impact, but rainfall and nutrient addition synergized to cause large increases in biomass, declines in diversity, and near-complete species turnover. Plant species with resource-conservative functional traits (low specific leaf area, short stature) were replaced by species with resource-acquisitive functional traits (high specific leaf area, tall stature). On nutrient-rich soils, in contrast, rainfall addition alone caused substantial increases in biomass, whereas fertilization had little effect. Our results highlight that multiple resource limitation is a critical aspect when predicting the relative vulnerability of natural communities to climatically induced compositional change and diversity loss. PMID:26438856

  2. Advances of Community-Level Plant DNA Barcoding in China

    PubMed Central

    Pei, Nancai; Chen, Bufeng; Kress, W. J.

    2017-01-01

    DNA barcoding is a commonly used bio-technology in multiple disciplines including biology, environmental science, forensics and inspection, etc. Forest dynamic plots provide a unique opportunity to carry out large-scale, comparative, and multidisciplinary research for plant DNA barcoding. The paper concisely reviewed four previous progresses in China; specifically, species discrimination, community phylogenetic reconstruction, phylogenetic community structure exploration, and biodiversity index evaluation. Further, we demonstrated three major challenges; specifically, building the impetus to generate DNA barcodes using multiple plant DNA markers for all woody species at forest community levels, analyzing massive DNA barcoding sequence data, and promoting theoretical innovation. Lastly, we raised five possible directions; specifically, proposing a “purpose-driven barcode” fit for multi-level applications, developing new integrative sequencing strategies, pushing DNA barcoding beyond terrestrial ecosystem, constructing national-level DNA barcode sequence libraries for special plant groups, and establishing intelligent identification systems or online server platforms. These efforts will be potentially valuable to explore large-scale biodiversity patterns, the origin and evolution of life, and will also facilitate preservation and utilization of biodiversity resources. PMID:28270824

  3. Advances of Community-Level Plant DNA Barcoding in China.

    PubMed

    Pei, Nancai; Chen, Bufeng; Kress, W J

    2017-01-01

    DNA barcoding is a commonly used bio-technology in multiple disciplines including biology, environmental science, forensics and inspection, etc. Forest dynamic plots provide a unique opportunity to carry out large-scale, comparative, and multidisciplinary research for plant DNA barcoding. The paper concisely reviewed four previous progresses in China; specifically, species discrimination, community phylogenetic reconstruction, phylogenetic community structure exploration, and biodiversity index evaluation. Further, we demonstrated three major challenges; specifically, building the impetus to generate DNA barcodes using multiple plant DNA markers for all woody species at forest community levels, analyzing massive DNA barcoding sequence data, and promoting theoretical innovation. Lastly, we raised five possible directions; specifically, proposing a "purpose-driven barcode" fit for multi-level applications, developing new integrative sequencing strategies, pushing DNA barcoding beyond terrestrial ecosystem, constructing national-level DNA barcode sequence libraries for special plant groups, and establishing intelligent identification systems or online server platforms. These efforts will be potentially valuable to explore large-scale biodiversity patterns, the origin and evolution of life, and will also facilitate preservation and utilization of biodiversity resources.

  4. Metaproteome analysis of the microbial communities in agricultural biogas plants.

    PubMed

    Heyer, R; Kohrs, F; Benndorf, D; Rapp, E; Kausmann, R; Heiermann, M; Klocke, M; Reichl, U

    2013-09-25

    In biogas plants agricultural waste and energy crops are converted by complex microbial communities to methane for the production of renewable energy. In Germany, this process is widely applied namely in context of agricultural production systems. However, process disturbances, are one of the major causes for economic losses. In addition, the conversion of biomass, in particular of cellulose, is in most cases incomplete and, hence, insufficient. Besides technical aspects, a more profound characterization concerning the functionality of the microbial communities involved would strongly support the improvement of yield and stability in biogas production. To monitor these communities on the functional level, metaproteome analysis was applied in this study to full-scale agricultural biogas plants. Proteins were extracted directly from sludge for separation by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and subsequent identification with mass spectrometry. Protein profiles obtained with SDS-PAGE were specific for different biogas plants and often stable for several months. Differences of protein profiles were visualized by clustering, which allowed not only the discrimination between mesophilic and thermophilic operated biogas plants but also the detection of process disturbances such as acidification. In particular, acidification of a biogas plant was detected in advance by disappearance of major bands in SDS-PAGE. Identification of proteins from SDS-PAGE gels revealed that methyl CoM reductase, which is responsible for the release of methane during methanogenesis, from the order Methanosarcinales was significantly decreased. Hence, it is assumed that this enzyme might be a promising candidate to serve as a predictive biomarker for acidification.

  5. Diclofop-methyl affects microbial rhizosphere community and induces systemic acquired resistance in rice.

    PubMed

    Chen, Si; Li, Xingxing; Lavoie, Michel; Jin, Yujian; Xu, Jiahui; Fu, Zhengwei; Qian, Haifeng

    2017-01-01

    Diclofop-methyl (DM), a widely used herbicide in food crops, may partly contaminate the soil surface of natural ecosystems in agricultural area and exert toxic effects at low dose to nontarget plants. Even though rhizosphere microorganisms strongly interact with root cells, little is known regarding their potential modulating effect on herbicide toxicity in plants. Here we exposed rice seedlings (Xiushui 63) to 100μg/L DM for 2 to 8days and studied the effects of DM on rice rhizosphere microorganisms, rice systemic acquired resistance (SAR) and rice-microorganisms interactions. The results of metagenomic 16S rDNA Illumina tags show that DM increases bacterial biomass and affects their community structure in the rice rhizosphere. After DM treatment, the relative abundance of the bacterium genera Massilia and Anderseniella increased the most relative to the control. In parallel, malate and oxalate exudation by rice roots increased, potentially acting as a carbon source for several rhizosphere bacteria. Transcriptomic analyses suggest that DM induced SAR in rice seedlings through the salicylic acid (but not the jasmonic acid) signal pathway. This response to DM stress conferred resistance to infection by a pathogenic bacterium, but was not influenced by the presence of bacteria in the rhizosphere since SAR transcripts did not change significantly in xenic and axenic plant roots exposed to DM. The present study provides new insights on the response of rice and its associated microorganisms to DM stress.

  6. Incorporating the soil environment and microbial community into plant competition theory

    PubMed Central

    Ke, Po-Ju; Miki, Takeshi

    2015-01-01

    Plants affect microbial communities and abiotic properties of nearby soils, which in turn influence plant growth and interspecific interaction, forming a plant-soil feedback (PSF). PSF is a key determinant influencing plant population dynamics, community structure, and ecosystem functions. Despite accumulating evidence for the importance of PSF and development of specific PSF models, different models are not yet fully integrated. Here, we review the theoretical progress in understanding PSF. When first proposed, PSF was integrated with various mathematical frameworks to discuss its influence on plant competition. Recent theoretical models have advanced PSF research at different levels of ecological organizations by considering multiple species, applying spatially explicit simulations to examine how local-scale predictions apply to larger scales, and assessing the effect of PSF on plant temporal dynamics over the course of succession. We then review two foundational models for microbial- and litter-mediated PSF. We present a theoretical framework to illustrate that although the two models are typically presented separately, their behavior can be understood together by invasibility analysis. We conclude with suggestions for future directions in PSF theoretical studies, which include specifically addressing microbial diversity to integrate litter- and microbial-mediated PSF, and apply PSF to general coexistence theory through a trait-based approach. PMID:26500621

  7. Population variation affects interactions between two California salt marsh plant species more than precipitation.

    PubMed

    Noto, Akana E; Shurin, Jonathan B

    2016-02-01

    Species that occur along broad environmental gradients often vary in phenotypic traits that make them better adapted to local conditions. Variation in species interactions across gradients could therefore be due to either phenotypic differences among populations or environmental conditions that shift the balance between competition and facilitation. To understand how the environment (precipitation) and variation among populations affect species interactions, we conducted a common garden experiment using two common salt marsh plant species, Salicornia pacifica and Jaumea carnosa, from six salt marshes along the California coast encompassing a large precipitation gradient. Plants were grown alone or with an individual of the opposite species from the same site and exposed to one of three precipitation regimes. J. carnosa was negatively affected in the presence of S. pacifica, while S. pacifica was facilitated by J. carnosa. The strength of these interactions varied by site of origin but not by precipitation treatment. These results suggest that phenotypic variation among populations can affect interaction strength more than environment, despite a threefold difference in precipitation. Geographic intraspecific variation may therefore play an important role in determining the strength of interactions in communities.

  8. Phytochemical diversity drives plant-insect community diversity.

    PubMed

    Richards, Lora A; Dyer, Lee A; Forister, Matthew L; Smilanich, Angela M; Dodson, Craig D; Leonard, Michael D; Jeffrey, Christopher S

    2015-09-01

    What are the ecological causes and consequences of variation in phytochemical diversity within and between plant taxa? Despite decades of natural products discovery by organic chemists and research by chemical ecologists, our understanding of phytochemically mediated ecological processes in natural communities has been restricted to studies of either broad classes of compounds or a small number of well-characterized molecules. Until now, no studies have assessed the ecological causes or consequences of rigorously quantified phytochemical diversity across taxa in natural systems. Consequently, hypotheses that attempt to explain variation in phytochemical diversity among plants remain largely untested. We use spectral data from crude plant extracts to characterize phytochemical diversity in a suite of co-occurring plants in the tropical genus Piper (Piperaceae). In combination with 20 years of data focused on Piper-associated insects, we find that phytochemical diversity has a direct and positive effect on the diversity of herbivores but also reduces overall herbivore damage. Elevated chemical diversity is associated with more specialized assemblages of herbivores, and the cascading positive effect of phytochemistry on herbivore enemies is stronger as herbivore diet breadth narrows. These results are consistent with traditional hypotheses that predict positive associations between plant chemical diversity, insect herbivore diversity, and trophic specialization. It is clear from these results that high phytochemical diversity not only enhances the diversity of plant-associated insects but also contributes to the ecological predominance of specialized insect herbivores.

  9. Selection for niche differentiation in plant communities increases biodiversity effects.

    PubMed

    Zuppinger-Dingley, Debra; Schmid, Bernhard; Petermann, Jana S; Yadav, Varuna; De Deyn, Gerlinde B; Flynn, Dan F B

    2014-11-06

    In experimental plant communities, relationships between biodiversity and ecosystem functioning have been found to strengthen over time, a fact often attributed to increased resource complementarity between species in mixtures and negative plant-soil feedbacks in monocultures. Here we show that selection for niche differentiation between species can drive this increasing biodiversity effect. Growing 12 grassland species in test monocultures and mixtures, we found character displacement between species and increased biodiversity effects when plants had been selected over 8 years in species mixtures rather than in monocultures. When grown in mixtures, relative differences in height and specific leaf area between plant species selected in mixtures (mixture types) were greater than between species selected in monocultures (monoculture types). Furthermore, net biodiversity and complementarity effects were greater in mixtures of mixture types than in mixtures of monoculture types. Our study demonstrates a novel mechanism for the increase in biodiversity effects: selection for increased niche differentiation through character displacement. Selection in diverse mixtures may therefore increase species coexistence and ecosystem functioning in natural communities and may also allow increased mixture yields in agriculture or forestry. However, loss of biodiversity and prolonged selection of crops in monoculture may compromise this potential for selection in the longer term.

  10. Plant community responses to experimental warming across the tundra biome.

    PubMed

    Walker, Marilyn D; Wahren, C Henrik; Hollister, Robert D; Henry, Greg H R; Ahlquist, Lorraine E; Alatalo, Juha M; Bret-Harte, M Syndonia; Calef, Monika P; Callaghan, Terry V; Carroll, Amy B; Epstein, Howard E; Jónsdóttir, Ingibjörg S; Klein, Julia A; Magnússon, Borgthór; Molau, Ulf; Oberbauer, Steven F; Rewa, Steven P; Robinson, Clare H; Shaver, Gaius R; Suding, Katharine N; Thompson, Catharine C; Tolvanen, Anne; Totland, Ørjan; Turner, P Lee; Tweedie, Craig E; Webber, Patrick J; Wookey, Philip A

    2006-01-31

    Recent observations of changes in some tundra ecosystems appear to be responses to a warming climate. Several experimental studies have shown that tundra plants and ecosystems can respond strongly to environmental change, including warming; however, most studies were limited to a single location and were of short duration and based on a variety of experimental designs. In addition, comparisons among studies are difficult because a variety of techniques have been used to achieve experimental warming and different measurements have been used to assess responses. We used metaanalysis on plant community measurements from standardized warming experiments at 11 locations across the tundra biome involved in the International Tundra Experiment. The passive warming treatment increased plant-level air temperature by 1-3 degrees C, which is in the range of predicted and observed warming for tundra regions. Responses were rapid and detected in whole plant communities after only two growing seasons. Overall, warming increased height and cover of deciduous shrubs and graminoids, decreased cover of mosses and lichens, and decreased species diversity and evenness. These results predict that warming will cause a decline in biodiversity across a wide variety of tundra, at least in the short term. They also provide rigorous experimental evidence that recently observed increases in shrub cover in many tundra regions are in response to climate warming. These changes have important implications for processes and interactions within tundra ecosystems and between tundra and the atmosphere.

  11. Plant community responses to experimental warming across the tundra biome

    PubMed Central

    Walker, Marilyn D.; Wahren, C. Henrik; Hollister, Robert D.; Henry, Greg H. R.; Ahlquist, Lorraine E.; Alatalo, Juha M.; Bret-Harte, M. Syndonia; Calef, Monika P.; Callaghan, Terry V.; Carroll, Amy B.; Epstein, Howard E.; Jónsdóttir, Ingibjörg S.; Klein, Julia A.; Magnússon, Borgþór; Molau, Ulf; Oberbauer, Steven F.; Rewa, Steven P.; Robinson, Clare H.; Shaver, Gaius R.; Suding, Katharine N.; Thompson, Catharine C.; Tolvanen, Anne; Totland, Ørjan; Turner, P. Lee; Tweedie, Craig E.; Webber, Patrick J.; Wookey, Philip A.

    2006-01-01

    Recent observations of changes in some tundra ecosystems appear to be responses to a warming climate. Several experimental studies have shown that tundra plants and ecosystems can respond strongly to environmental change, including warming; however, most studies were limited to a single location and were of short duration and based on a variety of experimental designs. In addition, comparisons among studies are difficult because a variety of techniques have been used to achieve experimental warming and different measurements have been used to assess responses. We used metaanalysis on plant community measurements from standardized warming experiments at 11 locations across the tundra biome involved in the International Tundra Experiment. The passive warming treatment increased plant-level air temperature by 1-3°C, which is in the range of predicted and observed warming for tundra regions. Responses were rapid and detected in whole plant communities after only two growing seasons. Overall, warming increased height and cover of deciduous shrubs and graminoids, decreased cover of mosses and lichens, and decreased species diversity and evenness. These results predict that warming will cause a decline in biodiversity across a wide variety of tundra, at least in the short term. They also provide rigorous experimental evidence that recently observed increases in shrub cover in many tundra regions are in response to climate warming. These changes have important implications for processes and interactions within tundra ecosystems and between tundra and the atmosphere. PMID:16428292

  12. Connecting plant-microbial interactions above and belowground: a fungal endophyte affects decomposition.

    PubMed

    Lemons, Alisha; Clay, Keith; Rudgers, Jennifer A

    2005-10-01

    Mutualisms can strongly affect the structure of communities, but their influence on ecosystem processes is not well resolved. Here we show that a plant-microbial mutualism affects the rate of leaf litter decomposition using the widespread interaction between tall fescue grass (Lolium arundinaceum) and the fungal endophyte Neotyphodium coenophialum. In grasses, fungal endophytes live symbiotically in the aboveground tissues, where the fungi gain protection and nutrients from their host and often protect host plants from biotic and abiotic stress. In a field experiment, decomposition rate depended on a complex interaction between the litter source (collected from endophyte-infected or endophyte-free plots), the decomposition microenvironment (endophyte-infected or endophyte-free plots), and the presence of mesoinvertebrates (manipulated by the mesh size of litter bags). Over all treatments, decomposition was slower for endophyte-infected fescue litter than for endophyte-free litter. When mesoinvertebrates were excluded using fine mesh and litter was placed in a microenvironment with the endophyte, the difference between endophyte-infected and endophyte-free litter was strongest. In the presence of mesoinvertebrates, endophyte-infected litter decomposed faster in microenvironments with the endophyte than in microenvironments lacking the endophyte, suggesting that plots differ in the detritivore assemblage. Indeed, the presence of the endophyte in plots shifted the composition of Collembola, with more Hypogastruridae in the presence of the endophyte and more Isotomidae in endophyte-free plots. In a separate outdoor pot experiment, we did not find strong effects of the litter source or the soil microbial/microinvertebrate community on decomposition, which may reflect differences between pot and field conditions or other differences in methodology. Our work is among the first to demonstrate an effect of plant-endophyte mutualisms on ecosystem processes under field

  13. Arctic Late Cretaceous and Paleocene Plant Community Succession

    NASA Astrophysics Data System (ADS)

    Herman, Alexei; Spicer, Robert; Daly, Robert; Jolley, David; Ahlberg, Anders; Moiseeva, Maria

    2010-05-01

    The Arctic abounds with Late Cretaceous and Paleocene plant fossils attesting to a thriving, diverse, but now extinct polar ecosystem that sequestered vast amounts of carbon. Through detailed examination of plant remains and their distributions in time and space with respect to their entombing sedimentary facies, it has been possible to reconstruct changes in Arctic vegetation composition and dynamics through the Late Cretaceous and into the Paleocene. Based on over 10,000 leaf remains, fossil wood and palynomorph assemblages from northeastern Russia and northern Alaska and palynological data from elsewhere in the Arctic we identify a number of successional plant communities (SPCs) representing seral development from early (pioneer), through middle to late SPCs and climax vegetation. We recognise that (1) Equisetites and some ferns (typically Birisia, but after the beginning of the Maastrichtian, Onoclea) were obligatory components of the early SPCs; (2) first rare angiosperms (e.g. the dicot Vitiphyllum multifidum) appeared in the middle SPCs of the Arctic in the Early - Middle Albian; (3) from late Albian times onwards angiosperms became abundant in the middle SPCs of the Arctic, but were still rare in the earlier and later SPCs; (4) monocots appeared in the Maastrichtian early SPCs; (5) all Arctic Cretaceous late SPCs (and climax vegetation) were dominated by conifers; (6) Arctic SPCs were more numerous and diverse under warm climates than cold; (7) during the Albian and late Cretaceous, advanced (Cenophytic, angiosperm-dominated) plant communities coexisted with those of a more relictual (Mesophytic, dominated by ferns and gymnosperms) aspect, and plants composing these communities did not mix; (8) coal-forming environments (mires) remained conifer, fern and bryophyte dominated throughout the late Cretaceous and Paleocene with little penetration of woody angiosperm components and thus are conservative and predominantly Mesophytic in character; (9) bryophytes

  14. Hemiparasitic plant impacts animal and plant communities across four trophic levels.

    PubMed

    Hartley, S E; Green, P; Massey, F P; Press, M C P; Stewart, J A; John, E A

    2015-09-01

    Understanding the impact of species on community structure is a fundamental question in ecology. There is a growing body of evidence that suggests that both subdominant species and parasites can have disproportionately large effects on other organisms. Here we report those impacts for a species that is both subdominant and parasitic, the hemiparasite Rhinanthus minor. While the impact of parasitic angiosperms on their hosts and, to a lesser degree, coexisting plant species, has been well characterized, much less is known about their effects on higher trophic levels: We experimentally manipulated field densities of the hemiparasite Rhinanthus minor in a species-rich grassland, comparing the plant and invertebrate communities in plots where it was removed, present at natural densities, or present at enhanced densities. Plots with natural and enhanced densities of R. minor had lower plant biomass than plots without the hemiparasite, but enhanced densities almost doubled the abundance of invertebrates within the plots across all trophic levels, with effects evident in herbivores, predators, and detritivores. The hemiparasite R. minor, despite being a subdominant and transient component within plant communities that it inhabits, has profound effects on four different trophic levels. These effects persist beyond the life of the hemiparasite, emphasizing its role as a keystone species in grassland communities.

  15. 40 CFR 230.75 - Actions affecting plant and animal populations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 26 2013-07-01 2013-07-01 false Actions affecting plant and animal... Actions To Minimize Adverse Effects § 230.75 Actions affecting plant and animal populations. Minimization of adverse effects on populations of plants and animals can be achieved by: (a) Avoiding changes...

  16. 40 CFR 230.75 - Actions affecting plant and animal populations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 25 2011-07-01 2011-07-01 false Actions affecting plant and animal... Actions To Minimize Adverse Effects § 230.75 Actions affecting plant and animal populations. Minimization of adverse effects on populations of plants and animals can be achieved by: (a) Avoiding changes...

  17. 40 CFR 230.75 - Actions affecting plant and animal populations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 26 2012-07-01 2011-07-01 true Actions affecting plant and animal... Actions To Minimize Adverse Effects § 230.75 Actions affecting plant and animal populations. Minimization of adverse effects on populations of plants and animals can be achieved by: (a) Avoiding changes...

  18. 40 CFR 230.75 - Actions affecting plant and animal populations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 25 2014-07-01 2014-07-01 false Actions affecting plant and animal... Actions To Minimize Adverse Effects § 230.75 Actions affecting plant and animal populations. Minimization of adverse effects on populations of plants and animals can be achieved by: (a) Avoiding changes...

  19. 40 CFR 230.75 - Actions affecting plant and animal populations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Actions affecting plant and animal... Actions To Minimize Adverse Effects § 230.75 Actions affecting plant and animal populations. Minimization of adverse effects on populations of plants and animals can be achieved by: (a) Avoiding changes...

  20. Isolated and Community Contexts Produce Distinct Responses by Host Plants to the Presence of Ant-Aphid Interaction: Plant Productivity and Seed Viability.

    PubMed

    Canedo-Júnior, Ernesto Oliveira; Santiago, Graziele Silva; Zurlo, Luana Fonseca; Ribas, Carla Rodrigues; Carvalho, Rafaela Pereira; Alves, Guilherme Pereira; Carvalho, Mariana Comanucci Silva; Souza, Brígida

    2017-01-01

    Ant-aphid interactions may affect host plants in several ways, however, most studies measure only the amount of fruit and seed produced, and do not test seed viability. Therefore, the aim of this study was to assess the effects of the presence of ant-aphid interactions upon host plant productivity and seed viability in two different contexts: isolated and within an arthropod community. For this purpose we tested the hypothesis that in both isolated and community contexts, the presence of an ant-aphid interaction will have a positive effect on fruit and seed production, seed biomass and rate of seed germination, and a negative effect on abnormal seedling rates, in comparison to plants without ants. We performed a field mesocosm experiment containing five treatments: Ant-aphid, Aphid, Community, Ant-free community and Control. We counted fruits and seeds produced by each treatment, and conducted experiments for seed biomass and germinability. We found that in the community context the presence of an ant-aphid interaction negatively affected fruit and seed production. We think this may be because aphid attendance by tending-ants promotes aphid damage to the host plant, but without an affect on seed weight and viability. On the other hand, when isolated, the presence of an ant-aphid interaction positively affected fruit and seed production. These positive effects are related to the cleaning services offered to aphids by tending-ants, which prevent the development of saprophytic fungi on the surface of leaves, which would cause a decrease in photosynthetic rates. Our study is important because we evaluated some parameters of plant fitness that have not been addressed very well by other studies involving the effects of ant-aphid interactions mainly on plants with short life cycles. Lastly, our context dependent approach sheds new light on how ecological interactions can vary among different methods of crop management.

  1. Isolated and Community Contexts Produce Distinct Responses by Host Plants to the Presence of Ant-Aphid Interaction: Plant Productivity and Seed Viability

    PubMed Central

    Santiago, Graziele Silva; Zurlo, Luana Fonseca; Ribas, Carla Rodrigues; Carvalho, Rafaela Pereira; Alves, Guilherme Pereira; Carvalho, Mariana Comanucci Silva; Souza, Brígida

    2017-01-01

    Ant-aphid interactions may affect host plants in several ways, however, most studies measure only the amount of fruit and seed produced, and do not test seed viability. Therefore, the aim of this study was to assess the effects of the presence of ant-aphid interactions upon host plant productivity and seed viability in two different contexts: isolated and within an arthropod community. For this purpose we tested the hypothesis that in both isolated and community contexts, the presence of an ant-aphid interaction will have a positive effect on fruit and seed production, seed biomass and rate of seed germination, and a negative effect on abnormal seedling rates, in comparison to plants without ants. We performed a field mesocosm experiment containing five treatments: Ant-aphid, Aphid, Community, Ant-free community and Control. We counted fruits and seeds produced by each treatment, and conducted experiments for seed biomass and germinability. We found that in the community context the presence of an ant-aphid interaction negatively affected fruit and seed production. We think this may be because aphid attendance by tending-ants promotes aphid damage to the host plant, but without an affect on seed weight and viability. On the other hand, when isolated, the presence of an ant-aphid interaction positively affected fruit and seed production. These positive effects are related to the cleaning services offered to aphids by tending-ants, which prevent the development of saprophytic fungi on the surface of leaves, which would cause a decrease in photosynthetic rates. Our study is important because we evaluated some parameters of plant fitness that have not been addressed very well by other studies involving the effects of ant-aphid interactions mainly on plants with short life cycles. Lastly, our context dependent approach sheds new light on how ecological interactions can vary among different methods of crop management. PMID:28141849

  2. Characterizing the Seasonal Dynamics of Plant Community Photosynthesis Across a Range of Vegetation Types

    SciTech Connect

    Gu, Lianhong; Post, Wilfred M; Baldocchi, Dennis; Black, Andy; Suyker, A.E.,; Verma, Shashi; Vesala, Timo; Wofsy, Steve

    2009-01-01

    found that while the growing season length affected how much carbon dioxide could be potentially assimilated by a plant community over the course of a growing season, other factors that affect canopy photosynthetic capacity (e.g. nutrients, water) could be more important at this time scale. These results and insights demonstrate that the proposed method of analysis and system of terminology can serve as a foundation for studying the dynamics of plant community photosynthesis and such studies can be fruitful.

  3. Effects of contaminated dredge spoils on wetland plant communities: A literature review

    USGS Publications Warehouse

    Stewart, Paul M.; Garza, Eric L.; Butcher, Jason T.; Simon, Thomas P.

    2003-01-01

    Contaminated dredge spoil is a national concern due to its scope and effects on biota, water quality, and the physical environment. This literature review discusses the effects of contaminated dredge spoils on wetland plant communities. Plant communities naturally shift over time with changing environmental conditions. Addition of toxins and nutrients and changes in hydrology may influence plant community structure. The storage and disposal of nutrient and metal contaminated dredge spoils may cause shifts in nearby plant communities. Shifts in species composition and diversity may not be observed for decades after nutrient enrichment, causing any disturbance to remain undetected. Plant community shifts often have great amounts of inertia and are difficult to reverse.

  4. [Edge effect of the plant community structure on land-bridge islands in the Thousand Island Lake].

    PubMed

    Su, Xiao-Fei; Yuan, Jin-Feng; Hu, Guang; Xu, Gao-Fu; Yu, Ming-Jian

    2014-01-01

    The research was conducted on 29 land-bridge islands in the Thousand Island Lake (TIL), where long-term monitoring plots were set up during 2009-2010. The community attributes including species richness, Shannon index, plant mean height, plant mean diameter at breast height (DBH) and plant density along the edge-interior gradient from edge to interior forest were calculated to investigate the edge effect. The results showed that the species richness and Shannon index were affected through the whole gradient (larger than 50 m), while the range of edge effect was 20-30 m on mean plant height, and 10 m on plant density and mean DBH. Community attributes differed significantly among the edge gradients. The species richness and Shannon index peaked at the intermediate edge gradient. Plant density decreased and plant mean height increased along the edge to interior gradient. All five community attributes were significantly associated with the edge gradient, also different functional groups, evergreen or deciduous species, trees or shrubs, shade tolerant or shade intolerant species, were differentially influenced by the edge effect. It was demonstrated the influence of edge effect on the fragmented forest community varied with community attributes and functional groups.

  5. Links between soil microbial communities and plant traits in a species-rich grassland under long-term climate change.

    PubMed

    Sayer, Emma J; Oliver, Anna E; Fridley, Jason D; Askew, Andrew P; Mills, Robert T E; Grime, J Philip

    2017-02-01

    Climate change can influence soil microorganisms directly by altering their growth and activity but also indirectly via effects on the vegetation, which modifies the availability of resources. Direct impacts of climate change on soil microorganisms can occur rapidly, whereas indirect effects mediated by shifts in plant community composition are not immediately apparent and likely to increase over time. We used molecular fingerprinting of bacterial and fungal communities in the soil to investigate the effects of 17 years of temperature and rainfall manipulations in a species-rich grassland near Buxton, UK. We compared shifts in microbial community structure to changes in plant species composition and key plant traits across 78 microsites within plots subjected to winter heating, rainfall supplementation, or summer drought. We observed marked shifts in soil fungal and bacterial community structure in response to chronic summer drought. Importantly, although dominant microbial taxa were largely unaffected by drought, there were substantial changes in the abundances of subordinate fungal and bacterial taxa. In contrast to short-term studies that report high resistance of soil fungi to drought, we observed substantial losses of fungal taxa in the summer drought treatments. There was moderate concordance between soil microbial communities and plant species composition within microsites. Vector fitting of community-weighted mean plant traits to ordinations of soil bacterial and fungal communities showed that shifts in soil microbial community structure were related to plant traits representing the quality of resources available to soil microorganisms: the construction cost of leaf material, foliar carbon-to-nitrogen ratios, and leaf dry matter content. Thus, our study provides evidence that climate change could affect soil microbial communities indirectly via changes in plant inputs and highlights the importance of considering long-term climate change effects, especially

  6. Composition of fungal soil communities varies with plant abundance and geographic origin

    PubMed Central

    Reininger, Vanessa; Martinez-Garcia, Laura B.; Sanderson, Laura; Antunes, Pedro M.

    2015-01-01

    Interactions of belowground fungal communities with exotic and native plant species may be important drivers of plant community structure in invaded grasslands. However, field surveys linking plant community structure with belowground fungal communities are missing. We investigated whether a selected number of abundant and relatively rare plants, either native or exotic, from an old-field site associate with different fungal communities. We also assessed whether these plants showed different symbiotic relationships with soil biota through their roots. We characterized the plant community and collected roots to investigate fungal communities using 454 pyrosequencing and assessed arbuscular mycorrhizal colonization and enemy-induced lesions. Differences in fungal communities were considered based on the assessment of α- and β diversity depending on plant ‘abundance’ and ‘origin’. Plant abundance and origin determined the fungal community. Fungal richness was higher for native abundant as opposed to relatively rare native plant species. However, this was not observed for exotics of contrasting abundance. Regardless of their origin, β diversity was higher for rare than for abundant species. Abundant exotics in the community, which happen to be grasses, were the least mycorrhizal whereas rare natives were most susceptible to enemy attack. Our results suggest that compared with exotics, the relative abundance of remnant native plant species in our old-field site is still linked to the structure of belowground fungal communities. In contrast, exotic species may act as a disturbing agent contributing towards the homogenization of soil fungal communities, potentially changing feedback interactions. PMID:26371291

  7. A solar thermal electric power plant for small communities

    NASA Technical Reports Server (NTRS)

    Holl, R. J.

    1979-01-01

    A solar power plant has been designed with a rating of 1000-kW electric and a 0.4 annual capacity factor. It was configured as a prototype for plants in the 1000 to 10,000-kWe size range for application to small communities or industrial users either grid-connected or isolated from a utility grid. A small central receiver was selected for solar energy collection after being compared with alternative distributed collectors. Further trade studies resulted in the selection of Hitec (heat transfer salt composed of 53 percent KNO3, 40 percent NaNO2, 7 percent NaNO3) as both the receiver coolant and the sensible heat thermal stroage medium and the steam Rankine cycle for power conversion. The plant is configured with road-transportable units to accommodate remote sites and minimize site assembly requirements. Results of the analyses indicate that busbar energy costs are competitive with diesel-electric plants in certain situations, e.g., off-grid, remote regions with high insolation. Sensitivity of energy costs to plant power rating and system capacity factor are given.

  8. Spatial and temporal dynamics of soil moisture and salinity in typical plant communities of Sangonghe Basin

    NASA Astrophysics Data System (ADS)

    Gu, Fengxue; Chu, Yu; Zhang, Yuandong; Liu, Yongqiang; Anabiek, Subai; Ye, Qian; Pan, Xiaoling

    2003-07-01

    Soil moisture, salinity, ground water table and salt concentration were measured monthly in seven typical plant communities for one year in Sangonghe basin of Xinjiang. Temporal dynamics of soil water and salinity during growing season were compared within these communities. The dominant species in each of these communities were Suaeda physophora, Reaumuria soongorica, Anabasis aphylla and Kalidium foliatum, Tamarix ramosissima, Alhagi pseudalhagi and Haloxylon ammodendron respectively. Results show that soil water content and salinity were significantly different among all these communities. In the edge of alluvial fan and low reaches of the river, ground water table was high, soil profile was moist, and salt concentrated in the soil upper layers and surface. Soils were all saline with dominant species of T. ramosissima, A. aphylla and K. foliatum. In the plain area, communities were dominated by R. soongoricaand S. physophora Ground water table was generally low, but soil surface and up layer contained high salt concentration. Soil here belonged to strong to medium salinized soil. In ecotone, ground water table increased due to the irrigation in the nearby oasis. From soil surface to deep layers, water content increased gradually with no salt accumulation for all the layers. Vegetation in ecotone was stable and dominated by A. pseudalhagi. In intervale of desert, ground water table was very deep and soil was very dry throughout of the profile. There were no significant differences in vertical and temporal change of soil moisture. Communities were dominated by H. ammodendron. Spatial and temporal dynamics of the soil moisture and salinity caused community subrogation, and were the two main factors that affected distribution and succession of plant communities.

  9. The Effect of Nitrogen Deposition on Plant Performance and Community Structure: Is It Life Stage Specific?

    PubMed Central

    2016-01-01

    Nitrogen (N) deposition is a key global change factor that is increasing and affecting the structure and function of many ecosystems. To determine the influence of N deposition on specific systems, however, it is crucial to understand the temporal and spatial patterns of deposition as well as the response to that deposition. Response of the receiving plant communities may depend on the life stage-specific performance of individual species. We focus on the California oak savanna because N deposition to this system is complex—characterized by hotspots on the landscape and seasonal pulses. In a greenhouse experiment, we investigated the relative influence of N deposition on plant performance during early growth, peak biomass, and senescent life stages across different soil types, light, and community compositions. To represent the community we used three grass species—a native, naturalized exotic, and invasive exotic. At early growth and peak biomass stages performance was measured as height, and shoot and root biomass, and at the senescent stage as seed production. Simulated N deposition 1) increased shoot biomass and height of the native and, even more so, the naturalized exotic during early growth, 2) positively affected root biomass in all species during peak biomass, and 3) had no influence on seed production at the senescent stage. Alone, N deposition was not a strong driver of plant performance; however, small differences in performance among species in response to N deposition could affect community composition in future years. In particular, if there is a pulse of N deposition during the early growth stage, the naturalized exotic may have a competitive advantage that could result in its spread. Including spatial and temporal heterogeneity in a complex, manipulative experiment provides a clearer picture of not only where N management efforts should be targeted on the landscape, but also when. PMID:27253718

  10. SAMPLING EFFORT AFFECTS MULTIVARIATE COMPARISONS OF STREAM COMMUNITIES

    EPA Science Inventory

    The estimation of ecological trends and patterns is often dependent on the size of individual samples from each site (sample size) or spatial scale in general. Multivariate analysis is widely used for determining patterns of community structure, inferring species-environment rela...

  11. Deodorants and antiperspirants affect the axillary bacterial community.

    PubMed

    Callewaert, Chris; Hutapea, Prawira; Van de Wiele, Tom; Boon, Nico

    2014-10-01

    The use of underarm cosmetics is common practice in the Western society to obtain better body odor and/or to prevent excessive sweating. A survey indicated that 95 % of the young adult Belgians generally use an underarm deodorant or antiperspirant. The effect of deodorants and antiperspirants on the axillary bacterial community was examined on nine healthy subjects, who were restrained from using deodorant/antiperspirant for 1 month. Denaturing gradient gel electrophoresis was used to investigate the individual microbial dynamics. The microbial profiles were unique for every person. A stable bacterial community was seen when underarm cosmetics were applied on a daily basis and when no underarm cosmetics were applied. A distinct community difference was seen when the habits were changed from daily use to no use of deodorant/antiperspirant and vice versa. The richness was higher when deodorants and antiperspirants were applied. Especially when antiperspirants were applied, the microbiome showed an increase in diversity. Antiperspirant usage led toward an increase of Actinobacteria, which is an unfavorable situation with respect to body odor development. These initial results show that axillary cosmetics modify the microbial community and can stimulate odor-producing bacteria.

  12. Predation and landscape characteristics independently affect reef fish community organization.

    PubMed

    Stier, Adrian C; Hanson, Katharine M; Holbrook, Sally J; Schmitt, Russell J; Brooks, Andrew J

    2014-05-01

    Trophic island biogeography theory predicts that the effects of predators on prey diversity are context dependent in heterogeneous landscapes. Specifically, models predict that the positive effect of habitat area on prey diversity should decline in the presence of predators, and that predators should modify the partitioning of alpha and beta diversity across patchy landscapes. However, experimental tests of the predicted context dependency in top-down control remain limited. Using a factorial field experiment we quantify the effects of a focal predatory fish species (grouper) and habitat characteristics (patch size, fragmentation) on the partitioning of diversity and assembly of coral reef fish communities. We found independent effects of groupers and patch characteristics on prey communities. Groupers reduced prey abundance by 50% and gamma diversity by 45%, with a disproportionate removal of rare species relative to common species (64% and 36% reduction, respectively; an oddity effect). Further, there was a 77% reduction in beta diversity. Null model analysis demonstrated that groupers increased the importance of stochastic community assembly relative to patches without groupers. With regard to patch size, larger patches contained more fishes, but a doubling of patch size led to a modest (36%) increase in prey abundance. Patch size had no effect on prey diversity; however, fragmented patches had 50% higher species richness and modified species composition relative to unfragmented patches. Our findings suggest two different pathways (i.e., habitat or predator shifts) by which natural and/or anthropogenic processes can drive variation in fish biodiversity and community assembly.

  13. Ethical Issues Affecting Human Participants in Community College Research

    ERIC Educational Resources Information Center

    Wurtz, Keith

    2011-01-01

    The increasing demand of constituents to conduct analyses in order to help inform the decision-making process has led to the need for Institutional Research (IR) guidelines for community college educators. One method of maintaining the quality of research conducted by IR staff is to include professional development about ethics. This article…

  14. How Military Service Affects Student Veteran Success at Community Colleges

    ERIC Educational Resources Information Center

    O'Rourke, Patrick C., Jr.

    2013-01-01

    Increasingly more service members are separating from the military as the United States draws down the force and moves towards a post-war era. Tens of thousands of these veterans will leverage their GI Bill tuition and housing benefits in an attempt to access Southern California community colleges and bolster their transition into mainstream…

  15. Abandoned floodplain plant communities along a regulated dryland river

    USGS Publications Warehouse

    Reynolds, L. V.; Shafroth, Patrick B.; House, P. K.

    2014-01-01

    Rivers and their floodplains worldwide have changed dramatically over the last century because of regulation by dams, flow diversions and channel stabilization. Floodplains no longer inundated by river flows following dam-induced flood reduction comprise large areas of bottomland habitat, but the effects of abandonment on plant communities are not well understood. Using a hydraulic flow model, geomorphic mapping and field surveys, we addressed the following questions along the Bill Williams River, Arizona: (i) What per cent of the bottomland do abandoned floodplains comprise? and (ii) Are abandoned floodplains quantitatively different from adjacent xeric and riparian surfaces in terms of vegetation composition and surface sediment? We found that nearly 70% of active channel and floodplain area was abandoned following dam installation. Abandoned floodplains along the Bill Williams River tend to be similar to each other yet distinct from neighbouring habitats: they have been altered physically from their historic state, leading to distinct combinations of surface sediments, hydrology and plant communities. Abandoned floodplains may transition to xeric communities over time but are likely to retain some riparian qualities as long as there is access to relatively shallow ground water. With expected increases in water demand and drying climatic conditions in many regions, these surfaces and associated vegetation will continue to be extensive in riparian landscapes worldwide

  16. Affective imagery and acceptance of replacing nuclear power plants.

    PubMed

    Keller, Carmen; Visschers, Vivianne; Siegrist, Michael

    2012-03-01

    This study examined the relationship between the content of spontaneous associations with nuclear power plants and the acceptance of using new-generation nuclear power plants to replace old ones. The study also considered gender as a variable. A representative sample of the German- and French-speaking population of Switzerland (N= 1,221) was used. Log-linear models revealed significant two-way interactions between the association content and acceptance, association content and gender, and gender and acceptance. Correspondence analysis revealed that participants who were opposed to nuclear power plants mainly associated nuclear power plants with risk, negative feelings, accidents, radioactivity, waste disposal, military use, and negative consequences for health and environment; whereas participants favoring nuclear power plants mainly associated them with energy, appearance descriptions of nuclear power plants, and necessity. Thus, individuals opposing nuclear power plants had both more concrete and more diverse associations with them than people who were in favor of nuclear power plants. In addition, participants who were undecided often mentioned similar associations to those participants who were in favor. Males more often expressed associations with energy, waste disposal, and negative health effects. Females more often made associations with appearance descriptions, negative feelings, and negative environmental effects. The results further suggest that acceptance of replacing nuclear power plants was higher in the German-speaking part of the country, where all of the Swiss nuclear power plants are physically located. Practical implications for risk communication are discussed.

  17. Community Structures of Arbuscular Mycorrhizal Fungi in Soils and Plant Roots Inhabiting Abandoned Mines of Korea

    PubMed Central

    Park, Hyeok; Lee, Eun-Hwa; Ka, Kang-Hyeon

    2016-01-01

    In this study, we collected rhizosphere soils and root samples from a post-mining area and a natural forest area in Jecheon, Korea. We extracted spores of arbuscular mycorrhizal fungi (AMF) from rhizospheres, and then examined the sequences of 18S rDNA genes of the AMF from the collected roots of plants. We compared the AMF communities in the post-mining area and the natural forest area by sequence analysis of the AMF spores from soils and of the AMF clones from roots. Consequently, we confirmed that the structure of AMF communities varied between the post-mining area and the natural forest area and showed significant relationship with heavy metal contents in soils. These results suggest that heavy metal contamination by mining activity significantly affects the AMF community structure. PMID:28154485

  18. Community Structures of Arbuscular Mycorrhizal Fungi in Soils and Plant Roots Inhabiting Abandoned Mines of Korea.

    PubMed

    Park, Hyeok; Lee, Eun-Hwa; Ka, Kang-Hyeon; Eom, Ahn-Heum

    2016-12-01

    In this study, we collected rhizosphere soils and root samples from a post-mining area and a natural forest area in Jecheon, Korea. We extracted spores of arbuscular mycorrhizal fungi (AMF) from rhizospheres, and then examined the sequences of 18S rDNA genes of the AMF from the collected roots of plants. We compared the AMF communities in the post-mining area and the natural forest area by sequence analysis of the AMF spores from soils and of the AMF clones from roots. Consequently, we confirmed that the structure of AMF communities varied between the post-mining area and the natural forest area and showed significant relationship with heavy metal contents in soils. These results suggest that heavy metal contamination by mining activity significantly affects the AMF community structure.

  19. Compost may affect volatile and semi-volatile plant emissions through nitrogen supply and chlorophyll fluorescence.

    PubMed

    Ormeño, Elena; Olivier, Romain; Mévy, Jean Philippe; Baldy, Virginie; Fernandez, Catherine

    2009-09-01

    The use of composted biosolids as an amendment for forest regeneration in degraded ecosystems is growing since sewage-sludge dumping has been banned in the European Community. Its consequences on plant terpenes are however unknown. Terpene emissions of both Rosmarinus officinalis (a terpene-storing species) and Quercus coccifera (a non-storing species) and terpene content of the former, were studied after a middle-term exposure to compost at intermediate (50tha(-1): D50) and high (100tha(-1): D100) compost rates, in a seven-year-old post-fire shrubland ecosystem. Some chlorophyll fluorescence parameters (Fv/Fm, ETR, Phi(PSII)), soil and plant enrichment in phosphorus (P) and nitrogen (N) were monitored simultaneously in amended and non-amended plots in order to establish what factors were responsible for possible compost effect on terpenes. Compost affected all studied parameters with the exception of Fv/Fm and terpene content. For both species, mono- and sesquiterpene basal emissions were intensified solely under D50 plots. On the contrary leaf P, leaf N levels reached in D50 were partly responsible of terpene changes, suggesting that optimal N conditions occurred therein. N also affected ETR and Phi(PSII) which were, in turn, robustly correlated to terpene emissions. These results imply that emissions of terpene-storing and non-storing species were under nitrogen and chlorophyll fluorescence control, and that a correct management of compost rates applied on soil may modify terpene emission rate of plants, which in turn has consequences in air quality and plant defense mechanisms.

  20. The relative importance of host-plant genetic diversity in structuring the associated herbivore community.

    PubMed

    Tack, Ayco J M; Roslin, Tomas

    2011-08-01

    Recent studies suggest that intraspecific genetic diversity in one species may leave a substantial imprint on the surrounding community and ecosystem. Here, we test the hypothesis that genetic diversity within host-plant patches translates into consistent and ecologically important changes in the associated herbivore community. More specifically, we use potted, grafted oak saplings to construct 41 patches of four saplings each, with one, two, or four tree genotypes represented among the host plants. These patches were divided among two common gardens. Focusing first at the level of individual trees, we assess how tree-specific genotypic identity, patch-level genetic diversity, garden-level environmental variation, and their interactions affect the structure of the herbivore community. At the level of host-plant patches, we analyze whether the joint responses of herbivore species to environmental variation and genetic diversity result in differences in species diversity among tree quartets. Strikingly, both species-specific abundances and species diversity varied substantially among host-tree genotypes, among common gardens, and among specific locations within individual gardens. In contrast, the genetic diversity of the patch left a detectable imprint on local abundances of only two herbivore taxa. In both cases, the effect of genetic diversity was inconsistent among gardens and among host-plant genotypes. While the insect community differed significantly among individual host-plant genotypes, there were no interactive effects of the number of different genotypes within the patch. Overall, additive effects of intraspecific genetic diversity of the host plant explained a similar or lower proportion (7-10%) of variation in herbivore species diversity than did variation among common gardens. Combined with the few previous studies published to date, our study suggests that the impact of host-plant genetic diversity on the herbivore community can range from none to

  1. Receding Water Line and Interspecific Competition Determines Plant Community Composition and Diversity in Wetlands in Beijing

    PubMed Central

    Wang, Zhengjun; Gong, Huili; Zhang, Jing

    2015-01-01

    Climate and human-induced wetland degradation has accelerated in recent years, not only resulting in reduced ecosystem services but also greatly affecting the composition and diversity of wetland plant communities. To date, the knowledge of the differences in community parameters and their successional trends in degraded wetlands remains scarce. Here based on remote sensing images, geographic information system technology, and statistical methods, we produced a successional gradient map of the Yeyahu Wetland Nature Reserve in Beijing, which has experienced a steady decline in water level in recent decades. In addition, we analyzed community composition and diversity along with each identified gradient. The results showed that community diversity decreases while dominance increases with the progress of succession, with the highest diversity occurring during the early stage of succession. Moreover, the community demonstrates greater similarity among subareas during later successional stages, and the similarity coefficients calculated from the important value (IV) of each species are more accurate. Correlation analysis showed that the impact of soil factors on diversity was not significant at a subarea scale, although these nutrients showed an increasing trend with the community succession. Furthermore, the IVs of the dominant species had a particularly significant impact on diversity, showing a significantly negative correlation with diversity indices and a significantly positive correlation with dominance indices. Further analysis showed that the retreat of water level resulted from sustained drought and local human activities was a major extrinsic driving force resulting in observed differences in the community successional stages, which resulted in differences in community composition and diversity. On the other hand, interspecific competition was the main intrinsic mechanism, which significantly influenced the IVs of the dominant species and community diversity

  2. Convergence in mycorrhizal fungal communities due to drought, plant competition, parasitism, and susceptibility to herbivory: consequences for fungi and host plants

    PubMed Central

    Gehring, Catherine A.; Mueller, Rebecca C.; Haskins, Kristin E.; Rubow, Tine K.; Whitham, Thomas G.

    2014-01-01

    Plants and mycorrhizal fungi influence each other’s abundance, diversity, and distribution. How other biotic interactions affect the mycorrhizal symbiosis is less well understood. Likewise, we know little about the effects of climate change on the fungal component of the symbiosis or its function. We synthesized our long-term studies on the influence of plant parasites, insect herbivores, competing trees, and drought on the ectomycorrhizal fungal communities associated with a foundation tree species of the southwestern United States, pinyon pine (Pinus edulis), and described how these changes feed back to affect host plant performance. We found that drought and all three of the biotic interactions studied resulted in similar shifts in ectomycorrhizal fungal community composition, demonstrating a convergence of the community towards dominance by a few closely related fungal taxa. Ectomycorrhizal fungi responded similarly to each of these stressors resulting in a predictable trajectory of community disassembly, consistent with ecological theory. Although we predicted that the fungal communities associated with trees stressed by drought, herbivory, competition, and parasitism would be poor mutualists, we found the opposite pattern in field studies. Our results suggest that climate change and the increased importance of herbivores, competitors, and parasites that can be associated with it, may ultimately lead to reductions in ectomycorrhizal fungal diversity, but that the remaining fungal community may be beneficial to host trees under the current climate and the warmer, drier climate predicted for the future. PMID:25009537

  3. Key players of methane dynamics in alpine fens: interaction of vascular plants and microbial communities

    NASA Astrophysics Data System (ADS)

    Cheema, S.; Zeyer, J. A.; Henneberger, R.

    2014-12-01

    Natural wetlands are important emitters of the potent greenhouse gas methane (CH4), contributing an estimated 26 - 42% to the global emissions. In these habitats CH4 is generated by methanogenic archaea mediating the terminal steps of organic matter degradation under anoxic conditions. The produced CH4 is partly oxidized by methanotrophic bacteria in oxic zones, thereby mitigating CH4 release. Various factors can influence CH4 emissions from wetlands, including the presence of vascular plants, as their aerenchyma can serve as conduits for CH4 release to the atmosphere. In the present study, we investigated the CH4 dynamics in two Swiss alpine fens (1900 - 2300 m a.s.l), and sampling locations within these fens were characterized by distinct dominant vascular plants, namely Carex spp. and Eriophorum spp.. Analyses of the microbial communities present in the fen soils were complemented by in situ measurements of CH4 emissions and analyses of physico-chemical pore water properties. Methane emissions and pore water concentrations varied depending on fen and dominating plant species, with generally higher CH4 emissions observed from the Carex dominated locations. Active methanotrophic and methanogenic microorganisms (transcripts of specific marker genes) were detected at different depths, independent of O2 and CH4 pore water concentrations. The expected separation of oxic methanotrophic and anoxic methanogenic zones was not observed. Yet, composition analyses of the different communities showed a clear clustering according to fen and dominating plant species. Within each location, variation of composition with depth was only observed for the methanogenic communities. Detailed profiling of CH4 emissions with respect to changes in light and temperature is currently being carried out. Our results represent a comprehensive in situ study on factors affecting CH4 emissions from alpine fens, highlighting the influence of vascular plants on the microbial communities involved.

  4. Influence of weather variables and plant communities on grasshopper density in the Southern Pampas, Argentina.

    PubMed

    de Wysiecki, María Laura; Arturi, Marcelo; Torrusio, Sandra; Cigliano, María Marta

    2011-01-01

    A study was conducted to evaluate the influence of weather (precipitation and temperature) and plant communities on grasshopper density over a 14-year period (1996-2009) in Benito Juárez County, Southern Pampas, Argentina. Total density strongly varied among plant communities. Highest values were registered in 2001 and 2003 in highly disturbed pastures and in 2002 and 2009 in halophilous grasslands. Native grasslands had the lowest density values. Seasonal precipitation and temperature had no significant effect on total grasshopper density. Dichroplus elongatus (Giglio-Tos) (Orthoptera: Acridoidea), Covasacris pallidinota (Bruner), Dichroplus pratensis Bruner, Scotussa lemniscata Stål, Borellia bruneri (Rehn) and Dichroplus maculipennis (Blanchard) comprised, on average, 64% of the grasshopper assemblages during low density years and 79% during high density years. Dichroplus elongatus, S. lemniscata and C. pallidinota were the most abundant species in 2001, 2002 and 2003, while D. elongatus, B. brunneri and C. pallidinota in 2009. Dichroplus elongatus and D. pratensis, mixed feeders species, were positively affected by summer rainfall. This suggests that the increase in summer precipitation had a positive effect on the quantity and quality forage production, affecting these grasshopper populations. Scotussa lemniscata and C. pallidinota were negatively affected by winter and fall temperature, possibly affecting the embryonic development before diapause and hatching. Dichroplus elongatus and D. pratensis were associated with highly disturbed pastures, S. lemniscata with pastures and B. bruneri and D. maculipennis with halophilous grasslands. Covasacris pallidinota was closely associated with halophilous grasslands and moderately disturbed pastures. Weather conditions changed over the years, with 2001, 2002 and 2003 having excessive rainfall while 2008 and 2009 were the driest years since the study started. We suggest that although seasonal precipitation and

  5. Influence of Weather Variables and Plant Communities on Grasshopper Density in the Southern Pampas, Argentina

    PubMed Central

    de Wysiecki, María Laura; Arturi, Marcelo; Torrusio, Sandra; Cigliano, María Marta

    2011-01-01

    A study was conducted to evaluate the influence of weather (precipitation and temperature) and plant communities on grasshopper density over a 14-year period (1996–2009) in Benito Juárez County, Southern Pampas, Argentina. Total density strongly varied among plant communities. Highest values were registered in 2001 and 2003 in highly disturbed pastures and in 2002 and 2009 in halophilous grasslands. Native grasslands had the lowest density values. Seasonal precipitation and temperature had no significant effect on total grasshopper density. Dichroplus elongatus (Giglio-Tos) (Orthoptera: Acridoidea), Covasacris pallidinota (Bruner), Dichroplus pratensis Bruner, Scotussa lemniscata Stål, Borellia bruneri (Rehn) and Dichroplus maculipennis (Blanchard) comprised, on average, 64% of the grasshopper assemblages during low density years and 79% during high density years. Dichroplus elongatus, S. lemniscata and C. pallidinota were the most abundant species in 2001, 2002 and 2003, while D. elongatus, B. brunneri and C. pallidinota in 2009. Dichroplus elongatus and D. pratensis, mixed feeders species, were positively affected by summer rainfall. This suggests that the increase in summer precipitation had a positive effect on the quantity and quality forage production, affecting these grasshopper populations. Scotussa lemniscata and C. pallidinota were negatively affected by winter and fall temperature, possibly affecting the embryonic development before diapause and hatching. Dichroplus elongatus and D. pratensis were associated with highly disturbed pastures, S. lemniscata with pastures and B. bruneri and D. maculipennis with halophilous grasslands. Covasacris pallidinota was closely associated with halophilous grasslands and moderately disturbed pastures. Weather conditions changed over the years, with 2001, 2002 and 2003 having excessive rainfall while 2008 and 2009 were the driest years since the study started. We suggest that although seasonal precipitation and

  6. Additive and interactive effects of plant genotypic diversity on arthropod communities and plant fitness.

    PubMed

    Johnson, Marc T J; Lajeunesse, Marc J; Agrawal, Anurag A

    2006-01-01

    Recent research suggests that genetic diversity in plant populations can shape the diversity and abundance of consumer communities. We tested this hypothesis in a field experiment by manipulating patches of Evening Primrose (Oenothera biennis) to contain one, four or eight plant genotypes. We then surveyed 92 species of naturally colonizing arthropods. Genetically diverse plant patches had 18% more arthropod species, and a greater abundance of omnivorous and predacious arthropods, but not herbivores, compared with monocultures. The effects of genotypic diversity on arthropod communities were due to a combination of interactive and additive effects among genotypes within genetically diverse patches. Greater genetic diversity also led to a selective feedback, as mean genotype fitness was 27% higher in diverse patches than in monocultures. A comparison between our results and the literature reveals that genetic diversity and species diversity can have similar qualitative and quantitative effects on arthropod communities. Our findings also illustrate the benefit of preserving genetic variation to conserve species diversity and interactions within multitrophic communities.

  7. Disturbance alters the phylogenetic composition and structure of plant communities in an old field system.

    PubMed

    Dinnage, Russell

    2009-09-18

    The changes in phylogenetic composition and structure of communities during succession following disturbance can give us insights into the forces that are shaping communities over time. In abandoned agricultural fields, community composition changes rapidly when a field is plowed, and is thought to reflect a relaxation of competition due to the elimination of dominant species which take time to re-establish. Competition can drive phylogenetic overdispersion, due to phylogenetic conservation of 'niche' traits that allow species to partition resources. Therefore, undisturbed old field communities should exhibit higher phylogenetic dispersion than recently disturbed systems, which should be relatively 'clustered' with respect to phylogenetic relationships. Several measures of phylogenetic structure between plant communities were measured in recently plowed areas and nearby 'undisturbed' sites. There was no difference in the absolute values of these measures between disturbed and 'undisturbed' sites. However, there was a difference in the 'expected' phylogenetic structure between habitats, leading to significantly lower than expected phylogenetic diversity in disturbed plots, and no difference from random expectation in 'undisturbed' plots. This suggests that plant species characteristic of each habitat are fairly evenly distributed on the shared species pool phylogeny, but that once the initial sorting of species into the two habitat types has occurred, the processes operating on them affect each habitat differently. These results were consistent with an analysis of correlation between phylogenetic distance and co-occurrence indices of species pairs in the two habitat types. This study supports the notion that disturbed plots are more clustered than expected, rather than 'undisturbed' plots being more overdispersed, suggesting that disturbed plant communities are being more strongly influenced by environmental filtering of conserved niche traits.

  8. Nutrient enrichment affects the mechanical resistance of aquatic plants

    PubMed Central

    Puijalon, Sara

    2012-01-01

    For many plant species, nutrient availability induces important anatomical responses, particularly the production of low-density tissues to the detriment of supporting tissues. Due to the contrasting biomechanical properties of plant tissues, these anatomical responses may induce important modifications in the biomechanical properties of plant organs. The aim of this study was to determine the effects of nutrient enrichment on the anatomical traits of two freshwater plant species and its consequences on plant biomechanical performance. Two plant species were grown under controlled conditions in low versus high nutrient levels. The anatomical and biomechanical traits of the plant stems were measured. Both species produced tissues with lower densities under nutrient-rich conditions, accompanied by modifications in the structure of the aerenchyma for one species. As expected, nutrient enrichment also led to important modifications in the biomechanical properties of the stem for both species. In particular, mechanical resistance (breaking force and strength) and stiffness of stems were significantly reduced under nutrient rich conditions. The production of weaker stem tissues as a result of nutrient enrichment may increase the risk of plants to mechanical failure, thus challenging plant maintenance in mechanically stressful or disturbed habitats. PMID:23028018

  9. The Brazilian research contribution to knowledge of the plant communities from Antarctic ice free areas.

    PubMed

    Pereira, Antonio B; Putzke, Jair

    2013-09-01

    This work aims to summarize the results of research carried out by Brazilian researchers on the plant communities of Antarctic ice free areas during the last twenty five years. Since 1988 field work has been carried out in Elephant Island, King George Island, Nelson Island and Deception Island. During this period six papers were published on the chemistry of lichens, seven papers on plant taxonomy, five papers on plant biology, two studies on UVB photoprotection, three studies about the relationships between plant communities and bird colonies and eleven papers on plant communities from ice free areas. At the present, Brazilian botanists are researching the plant communities of Antarctic ice free areas in order to understand their relationships to soil microbial communities, the biodiversity, the distribution of the plants populations and their relationship with birds colonies. In addition to these activities, a group of Brazilian researchers are undertaking studies related to Antarctic plant genetic diversity, plant chemistry and their biotechnological applications.

  10. 7-Rhamnosylated Flavonols Modulate Homeostasis of the Plant Hormone Auxin and Affect Plant Development*

    PubMed Central

    Kuhn, Benjamin M.; Errafi, Sanae; Bucher, Rahel; Dobrev, Petre; Geisler, Markus; Bigler, Laurent; Zažímalová, Eva; Ringli, Christoph

    2016-01-01

    Flavonols are a group of secondary metabolites that affect diverse cellular processes. They are considered putative negative regulators of the transport of the phytohormone auxin, by which they influence auxin distribution and concomitantly take part in the control of plant organ development. Flavonols are accumulating in a large number of glycosidic forms. Whether these have distinct functions and diverse cellular targets is not well understood. The rol1-2 mutant of Arabidopsis thaliana is characterized by a modified flavonol glycosylation profile that is inducing changes in auxin transport and growth defects in shoot tissues. To determine whether specific flavonol glycosides are responsible for these phenotypes, a suppressor screen was performed on the rol1-2 mutant, resulting in the identification of an allelic series of UGT89C1, a gene encoding a flavonol 7-O-rhamnosyltransferase. A detailed analysis revealed that interfering with flavonol rhamnosylation increases the concentration of auxin precursors and auxin metabolites, whereas auxin transport is not affected. This finding provides an additional level of complexity to the possible ways by which flavonols influence auxin distribution and suggests that flavonol glycosides play an important role in regulating plant development. PMID:26742840

  11. 7-Rhamnosylated Flavonols Modulate Homeostasis of the Plant Hormone Auxin and Affect Plant Development.

    PubMed

    Kuhn, Benjamin M; Errafi, Sanae; Bucher, Rahel; Dobrev, Petre; Geisler, Markus; Bigler, Laurent; Zažímalová, Eva; Ringli, Christoph

    2016-03-04

    Flavonols are a group of secondary metabolites that affect diverse cellular processes. They are considered putative negative regulators of the transport of the phytohormone auxin, by which they influence auxin distribution and concomitantly take part in the control of plant organ development. Flavonols are accumulating in a large number of glycosidic forms. Whether these have distinct functions and diverse cellular targets is not well understood. The rol1-2 mutant of Arabidopsis thaliana is characterized by a modified flavonol glycosylation profile that is inducing changes in auxin transport and growth defects in shoot tissues. To determine whether specific flavonol glycosides are responsible for these phenotypes, a suppressor screen was performed on the rol1-2 mutant, resulting in the identification of an allelic series of UGT89C1, a gene encoding a flavonol 7-O-rhamnosyltransferase. A detailed analysis revealed that interfering with flavonol rhamnosylation increases the concentration of auxin precursors and auxin metabolites, whereas auxin transport is not affected. This finding provides an additional level of complexity to the possible ways by which flavonols influence auxin distribution and suggests that flavonol glycosides play an important role in regulating plant development.

  12. Shrub communities as inhibitors of plant succession in southern Quebec

    NASA Astrophysics Data System (ADS)

    Meilleur, Alain; Véronneau, Hélène; Bouchard, André

    1994-11-01

    The purpose of our research was to identify shrub species growing in southern Quebec that inhibit ecological succession in power-line corridors. Results are presented in three parts. First, clonal characteristics that allowed the establishment of stable communities were identified. Second, successional vector analysis identified those species that have the potential to inhibit succession. In poorly drained sites those species were Cornus stolonifera, C. obliqua, Salix petiolaris, and Spiraea alba. In well-drained sites, those species were Zanthoxylum americanum, Rubus idaeus, Spiraea alba, Rhus typhina, and Thuja occidentalis. Third, analysis of variance showed that there is a significantly larger number of tree seedlings found in adjacent herbaceous communities than found under the dense cover of Cornus stolonifera, C. obliqua, Salix petiolaris, Spiraea alba, Rhus typhina, Rubus idaeus, Thuya occidentalis, and Zanthoxylum americanum. These results indicate that the planting of selected shrub species could, through biological control, delay reforestation.

  13. Balancing positive and negative plant interactions: how mosses structure vascular plant communities.

    PubMed

    Gornall, Jemma L; Woodin, Sarah J; Jónsdóttir, Ingibjorg S; van der Wal, René

    2011-07-01

    Our understanding of positive and negative plant interactions is primarily based on vascular plants, as is the prediction that facilitative effects dominate in harsh environments. It remains unclear whether this understanding is also applicable to moss-vascular plant interactions, which are likely to be influential in low-temperature environments with extensive moss ground cover such as boreal forest and arctic tundra. In a field experiment in high-arctic tundra, we investigated positive and negative impacts of the moss layer on vascular plants. Ramets of the shrub Salix polaris, herb Bistorta vivipara, grass Alopecurus borealis and rush Luzula confusa were transplanted into plots manipulated to contain bare soil, shallow moss (3 cm) and deep moss (6 cm) and harvested after three growing seasons. The moss layer had both positive and negative impacts upon vascular plant growth, the relative extent of which varied among vascular plant species. Deep moss cover reduced soil temperature and nitrogen availability, and this was reflected in reduced graminoid productivity. Shrub and herb biomass were greatest in shallow moss, where soil moisture also appeared to be highest. The relative importance of the mechanisms by which moss may influence vascular plants, through effects on soil temperature, moisture and nitrogen availability, was investigated in a phytotron growth experiment. Soil temperature, and not nutrient availability, determined Alopecurus growth, whereas Salix only responded to increased temperature if soil nitrogen was also increased. We propose a conceptual model showing the relative importance of positive and negative influences of the moss mat on vascular plants along a gradient of moss depth and illustrate species-specific outcomes. Our findings suggest that, through their strong influence on the soil environment, mat-forming mosses structure the composition of vascular plant communities. Thus, for plant interaction theory to be widely applicable to

  14. Engineering a plant community to deliver multiple ecosystem services.

    PubMed

    Storkey, Jonathan; Döring, Thomas; Baddeley, John; Collins, Rosemary; Roderick, Stephen; Jones, Hannah; Watson, Christine

    2015-06-01

    The sustainable delivery of multiple ecosystem services requires the management of functionally diverse biological communities. In an agricultural context, an emphasis on food production has often led to a loss of biodiversity to the detriment of other ecosystem services such as the maintenance of soil health and pest regulation. In scenarios where multiple species can be grown together, it may be possible to better balance environmental and agronomic services through the targeted selection of companion species. We used the case study of legume-based cover crops to engineer a plant community that delivered the optimal balance of six ecosystem services: early productivity, regrowth following mowing, weed suppression, support of invertebrates, soil fertility building (measured as yield of following crop), and conservation of nutrients in the soil. An experimental species pool of 12 cultivated legume species was screened for a range of functional traits and ecosystem services at five sites across a geographical gradient in the United Kingdom. All possible species combinations were then analyzed, using a process-based model of plant competition, to identify the community that delivered the best balance of services at each site. In our system, low to intermediate levels of species richness (one to four species) that exploited functional contrasts in growth habit and phenology were identified as being optimal. The optimal solution was determined largely by the number of species and functional diversity represented by the starting species pool, emphasizing the importance of the initial selection of species for the screening experiments. The approach of using relationships between functional traits and ecosystem services to design multifunctional biological communities has the potential to inform the design of agricultural systems that better balance agronomic and environmental services and meet the current objective of European agricultural policy to maintain viable food

  15. Everglades Plant Community Response to 20th Century Hydrologic Changes

    NASA Astrophysics Data System (ADS)

    Willard, D. A.; Bernhardt, C. E.; Holmes, C. W.; Weimer, L. M.

    2002-05-01

    Pollen records in sediment cores from sites in the historic Everglades allowed us to document the natural variability of the ecosystem over the past 2,000 years and contrast it to 20th century changes in wetland plant communities. The natural system included extensive water-lily sloughs, sawgrass ridges, and scattered tree islands extending from Lake Okeechobee southward through Shark River Slough. Between ~1000 AD and 1200 AD, weedy species such as Amaranthus (water hemp) became more abundant, indicating decreased annual rainfall, shorter hydroperiods, and shallower water depths during this time. After ~1200 AD, vegetation returned to its pre-1000 AD composition. During the 20th century, two phases of hydrologic alteration occurred. Completed by 1930, the first phase included construction of the Hoover Dike, canals linking Lake Okeechobee to the Atlantic Ocean, and the Tamiami Trail. Reconstructions of plant communities indicate that these changes shortened hydroperiods and lowered water depths throughout the Everglades. The extent of water-lily slough communities decreased, and tree islands became larger in Shark River Slough. The second phase resulted from construction of canals and levees in the 1950s, creating three Water Conservation Areas. The response of plant communities to these changes varied widely depending on location in the Everglades. In Loxahatchee NWR, weedy and short-hydroperiod plant species became more abundant in marshes, and species composition of tree islands changed. In Water Conservation Area 2A, cattail replaced sawgrass in marshes with high nutrient influx; the ridge and slough structure of the marshes was replaced by more homogeneous sawgrass marshes; sustained high water levels for more than a decade resulted in loss of tree islands that had existed for more than 1,000 years. In Everglades National Park, the extent of slough vegetation decreased further. Near Florida Bay, the rate of mangrove intrusion into fresh-water marshes

  16. Population and community ecology of the rare plant amsinckia grandiflora

    SciTech Connect

    Carlsen, T.M.

    1996-11-01

    Research was conducted between the fall of 1992 and the spring on the population and community ecology of the rare annual plant, Amsinckia glandiflora (Gray) Kleeb. ex Greene (Boraginaceae). The research goal was to investigate the causes of the species rarity, data useful to restorative efforts. The work focused on the examination of competitive suppression by exotic annual grasses; comparisons with common, weedy congener; and the role of litter cover and seed germination and seedling establishment. Annual exotic grasses reduced A. grandiflora reproductive output to a greater extent than did the native perennial bunch grass.

  17. Major National Societal Trends Likely to Affect the Marin Community Colleges through the Year 2000. Societal Factors Affecting Education.

    ERIC Educational Resources Information Center

    Stetson, Nancy E.

    Societal trends likely to affect the Marin Community Colleges (MCC) through the year 2000 are examined in this study of college planning for the next 5 years. Following information on the background, significance, and procedures of the study, a review is presented of six publications, selected for their particular relevance to the community…

  18. Community violence as it affects child development: issues of definition.

    PubMed

    Trickett, Penelope K; Durán, Lorena; Horn, John L

    2003-12-01

    The state of the art of definition of community violence as it relates to child development was examined in terms of the definitions used in 23 empirical studies. In all cases community violence was defined in terms of what were assumed to be measurements obtained as linear combinations of a priori numerical weighting of responses to questions--asked either of a child or of the parent of a child--about experiencing and/or witnessing and/or hearing about instances of violence. Thus, the definitions can be seen to represent the perspectives of 2 kinds of observers--the child or the child's parent--and 3 levels of closeness to violence--experiencing, witnessing, or hearing about violence. Combining these perspectives and levels, the following 8 different definitions could be seen to be used in the practice of 1 or more of the 23 empirical studies: Child Self-Report (perception) of either (1) experiencing, or (2) witnessing, or (3) experiencing and witnessing, and hearing about violence; or Parent Report (perception) of the Child (4) experiencing, or (5) witnessing, or (6) experiencing and witnessing and hearing about violence, or (7) = (1) + (4), or (8) = (3) + (6). In almost all the examples of research definitions it was assumed implicitly and without test of the assumption that different violent events were interchangeable, and usually it was assumed (again without test) that the magnitudes of different violence events were equal. Usually, an unstated theory of stress appeared to guide the measurement definition, but in one study definitions were developed and tested in terms of a clearly-stated theory of learning. It was concluded that definition of community violence is a measurement problem; that very likely it is multidimensional; that it could be more nearly solved if better attention were given to specifying it in terms of theory that can be put to test and by attending to basic assumptions and principles of measurement.

  19. The movement ecology and dynamics of plant communities in fragmented landscapes.

    PubMed

    Damschen, Ellen I; Brudvig, Lars A; Haddad, Nick M; Levey, Douglas J; Orrock, John L; Tewksbury, Joshua J

    2008-12-09

    A conceptual model of movement ecology has recently been advanced to explain all movement by considering the interaction of four elements: internal state, motion capacity, navigation capacities, and external factors. We modified this framework to generate predictions for species richness dynamics of fragmented plant communities and tested them in experimental landscapes across a 7-year time series. We found that two external factors, dispersal vectors and habitat features, affected species colonization and recolonization in habitat fragments and their effects varied and depended on motion capacity. Bird-dispersed species richness showed connectivity effects that reached an asymptote over time, but no edge effects, whereas wind-dispersed species richness showed steadily accumulating edge and connectivity effects, with no indication of an asymptote. Unassisted species also showed increasing differences caused by connectivity over time, whereas edges had no effect. Our limited use of proxies for movement ecology (e.g., dispersal mode as a proxy for motion capacity) resulted in moderate predictive power for communities and, in some cases, highlighted the importance of a more complete understanding of movement ecology for predicting how landscape conservation actions affect plant community dynamics.

  20. Factors affecting plant growth in membrane nutrient delivery

    NASA Technical Reports Server (NTRS)

    Dreschel, T. W.; Wheeler, R. M.; Sager, J. C.; Knott, W. M.

    1990-01-01

    The development of the tubular membrane plant growth unit for the delivery of water and nutrients to roots in microgravity has recently focused on measuring the effects of changes in physical variables controlling solution availability to the plants. Significant effects of membrane pore size and the negative pressure used to contain the solution were demonstrated. Generally, wheat grew better in units with a larger pore size but equal negative pressure and in units with the same pore size but less negative pressure. Lettuce also exhibited better plant growth at less negative pressure.

  1. A preliminary classification of wetland plant communities in north-central Minnesota

    USGS Publications Warehouse

    Cowardin, L.M.; Johnson, D.H.

    1973-01-01

    A classification of wetland plant communities was developed for a study area in north-central Minnesota in order to analyze data on waterfowl use of habitat that were gathered by radio telemetry. The classification employs features of several earlier classifications in addition to new classes for bogs and lakeshore communities. Brief descriptions are given for each community, and the important plant species are listed. Discriminant function analysis was used for 40 plant species. Seventy-five percent of the stands studied were classified correctly by this technique. Average probabilities of assignment to communities were calculated and helped to identify distinct and poorly defined communities as well as the relationship among communities.

  2. A comparison of fungal communities from four salt marsh plants using automated ribosomal intergenic spacer analysis (ARISA).

    PubMed

    Torzilli, Albert P; Sikaroodi, Masoumeh; Chalkley, David; Gillevet, Patrick M

    2006-01-01

    Fungal decomposers are important contributors to the detritus-based food webs of salt marsh ecosystems. Knowing the composition of salt marsh fungal communities is essential in understanding how detritus processing is affected by changes in community dynamics. Automated ribosomal intergenic spacer analysis (ARISA) was used to examine the composition of fungal communities associated with four temperate salt marsh plants, Spartina alterniflora (short and tall forms), Juncus roemerianus, Distichlis spicata and Sarcocornia perennis. Plant tissues were homogenized and subjected to a particle-filtration protocol that yielded 106 microm particulate fractions, which were used as a source of fungal isolates and fungal DNA. Genera identified from sporulating cultures demonstrated that the 106 microm particles from each host plant were reliable sources of fungal DNA for ARISA. Analysis of ARISA data by principal component analysis (PCA), principal coordinate analysis (PCO) and species diversity comparisons indicated that the fungal communities from the two grasses, S. alterniflora and D. spicata were more similar to each other than they were to the distinct communities associated with J. roemerianus and S. perennis. Principal component analysis also showed no consistent, seasonal pattern in the composition of these fungal communities. Comparisons of ARISA fingerprints from the different fungal communities and those from pure cultures of selected Spartina ascomycetes supported the host/substrate specificity observed for the fungal communities.

  3. Neighboring trees affect ectomycorrhizal fungal community composition in a woodland-forest ecotone.

    PubMed

    Hubert, Nathaniel A; Gehring, Catherine A

    2008-09-01

    Ectomycorrhizal fungi (EMF) are frequently species rich and functionally diverse; yet, our knowledge of the environmental factors that influence local EMF diversity and species composition remains poor. In particular, little is known about the influence of neighboring plants on EMF community structure. We tested the hypothesis that the EMF of plants with heterospecific neighbors would differ in species richness and community composition from the EMF of plants with conspecific neighbors. We conducted our study at the ecotone between pinyon (Pinus edulis)-juniper (Juniperus monosperma) woodland and ponderosa pine (Pinus ponderosa) forest in northern Arizona, USA where the dominant trees formed associations with either EMF (P. edulis and P. ponderosa) or arbuscular mycorrhizal fungi (AMF; J. monosperma). We also compared the EMF communities of pinyon and ponderosa pines where their rhizospheres overlapped. The EMF community composition, but not species richness of pinyon pines was significantly influenced by neighboring AM juniper, but not by neighboring EM ponderosa pine. Ponderosa pine EMF communities were different in species composition when growing in association with pinyon pine than when growing in association with a conspecific. The EMF communities of pinyon and ponderosa pines were similar where their rhizospheres overlapped consisting of primarily the same species in similar relative abundance. Our findings suggest that neighboring tree species identity shaped EMF community structure, but that these effects were specific to host-neighbor combinations. The overlap in community composition between pinyon pine and ponderosa pine suggests that these tree species may serve as reservoirs of EMF inoculum for one another.

  4. Soil ecosystem functioning under climate change: plant species and community effects.

    PubMed

    Kardol, Paul; Cregger, Melissa A; Campany, Courtney E; Classen, Aimee T

    2010-03-01

    Feedbacks of terrestrial ecosystems to atmospheric and climate change depend on soil ecosystem dynamics. Soil ecosystems can directly and indirectly respond to climate change. For example, warming directly alters microbial communities by increasing their activity. Climate change may also alter plant community composition, thus indirectly altering the soil communities that depend on their inputs. To better understand how climate change may directly and indirectly alter soil ecosystem functioning, we investigated old-field plant community and soil ecosystem responses to single and combined effects of elevated [CO2], warming, and precipitation in Tennessee (USA). Specifically, we collected soils at the plot level (plant community soils) and beneath dominant plant species (plant-specific soils). We used microbial enzyme activities and soil nematodes as indicators for soil ecosystem functioning. Our study resulted in two main findings: (1) Overall, while there were some interactions, water, relative to increases in [CO2] and warming, had the largest impact on plant community composition, soil enzyme activity, and soil nematodes. Multiple climate-change factors can interact to shape ecosystems, but in our study, those interactions were largely driven by changes in water. (2) Indirect effects of climate change, via changes in plant communities, had a significant impact on soil ecosystem functioning, and this impact was not obvious when looking at plant community soils. Climate-change effects on enzyme activities and soil nematode abundance and community structure strongly differed between plant community soils and plant-specific soils, but also within plant-specific soils. These results indicate that accurate assessments of climate-change impacts on soil ecosystem functioning require incorporating the concurrent changes in plant function and plant community composition. Climate-change-induced shifts in plant community composition will likely modify or counteract the

  5. Alaska Melilotus invasions: Distribution, origin, and susceptibility of plant communities

    USGS Publications Warehouse

    Conn, J.S.; Beattie, K.L.; Shephard, M.A.; Carlson, M.L.; Lapina, I.; Hebert, M.; Gronquist, R.; Densmore, R.; Rasy, M.

    2008-01-01

    Melilotus alba and M. officinalis were introduced to Alaska in 1913 as potential forage crops. These species have become naturalized and are now invading large, exotic plant-free regions of Alaska. We determined distributions of M. alba and M. officinalis in Alaska from surveys conducted each summer from 2002 to 2005. Melilotus alba and M. officinalis occurred at 721 and 205 sites, respectively (39,756 total sites surveyed). The northward limit for M. alba and M. officinalis was 67.15??N and 64.87??N, respectively. Both species were strictly associated with soil disturbance. Melilotus alba extended no farther than 15 m from road edges except where M. alba on roadsides met river floodplains and dispersed downriver (Matanuska and Nenana Rivers). Melilotus has now reached the Tanana River, a tributary of the Yukon River. Populations on floodplains were most extensive on braided sections. On the Nenana River, soil characteristics did not differ between where M. alba was growing versus similar areas where it had not yet reached. The pH of river soils (7.9-8.3) was higher than highway soils (7.3). Upland taiga plant communities grow on acid soils which may protect them from invasion by Melilotus, which prefer alkaline soils; however, early succession communities on river floodplains are susceptible because soils are alkaline. ?? 2008 Regents of the University of Colorado.

  6. Above–Belowground Herbivore Interactions in Mixed Plant Communities Are Influenced by Altered Precipitation Patterns

    PubMed Central

    Ryalls, James M. W.; Moore, Ben D.; Riegler, Markus; Johnson, Scott N.

    2016-01-01

    Root- and shoot-feeding herbivores have the capacity to influence one another by modifying the chemistry of the shared host plant. This can alter rates of nutrient mineralization and uptake by neighboring plants and influence plant–plant competition, particularly in mixtures combining grasses and legumes. Root herbivory-induced exudation of nitrogen (N) from legume roots, for example, may increase N acquisition by co-occurring grasses, with knock-on effects on grassland community composition. Little is known about how climate change may affect these interactions, but an important and timely question is how will grass–legume mixtures respond in a future with an increasing reliance on legume N mineralization in terrestrial ecosystems. Using a model grass–legume mixture, this study investigated how simultaneous attack on lucerne (Medicago sativa) by belowground weevils (Sitona discoideus) and aboveground aphids (Acyrthosiphon pisum) affected a neighboring grass (Phalaris aquatica) when subjected to drought, ambient, and elevated precipitation. Feeding on rhizobial nodules by weevil larvae enhanced soil water retention under ambient and elevated precipitation, but only when aphids were absent. While drought decreased nodulation and root N content in lucerne, grass root and shoot chemistry were unaffected by changes in precipitation. However, plant communities containing weevils but not aphids showed increased grass height and N concentrations, most likely associated with the transfer of N from weevil-attacked lucerne plants containing more nodules and higher root N concentrations compared with insect-free plants. Drought decreased aphid abundance by 54% but increased total and some specific amino acid concentrations (glycine, lysine, methionine, tyrosine, cysteine, histidine, arginine, aspartate, and glutamate), suggesting that aphid declines were being driven by other facets of drought (e.g., reduced phloem hydraulics). The presence of weevil larvae belowground

  7. Exogenously treated mammalian sex hormones affect inorganic constituents of plants.

    PubMed

    Erdal, Serkan; Dumlupinar, Rahmi

    2011-10-01

    The present study was undertaken to reveal the changes in inorganic constituents of plants exposed to mammalian sex hormones (MSH). Chickpea leaves were sprayed with 10(-4), 10(-6), 10(-9), 10(-12), and 10(-15) M concentrations of progesterone, β-estradiol, and androsterone at 7th day after sowing. The plants were harvested at the end of 18 days after treatment of MSH solutions and the inorganic components determined using a wavelength-dispersive X-ray fluorescence spectroscopy technique. At all of the concentrations tested, MSH significantly increased the contents of K, S, Na, Ca, Mg, Zn, Fe, P, Cu, and Ni. Interestingly, only Mn and Cl contents decreased. The maximum changes in the inorganic composition were recorded at 10(-6) M for plants treated with progesterone and 10(-9) M for plants treated with β-estradiol and androsterone.

  8. Plant toxins that affect nicotinic acetylcholine receptors: A review

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plants produce wide variety of chemical compounds termed secondary metabolites that are not involved in basic metabolism, photosynthesis or reproduction. These compounds are used as flavors, fragrances, insecticides, dyes, hallucinogens, nutritional supplements, poisons, and pharmaceutical agents. ...

  9. A novel family of small proteins that affect plant development

    SciTech Connect

    John Charles Walker

    2011-04-29

    The DVL genes represent a new group of plant proteins that influence plant growth and development. Overexpression of DVL1, and other members of the DVL family, causes striking phenotypic changes. The DVL proteins share sequence homology in their C-terminal half. Point mutations in the C-terminal domain show it is necessary and deletion studies demonstrate the C-terminal domain is sufficient to confer the overexpression phenotypes. The phenotypes observed, and the conservation of the protein sequence in the plant kingdom, does suggest the DVL proteins have a role in modulating plant growth and development. Our working hypothesis is the DVL proteins function as regulators of cellular signaling pathways that control growth and development.

  10. Coastal Freshwater Wetland Plant Community Response to Seasonal Drought and Flooding in Northwestern Costa Rica

    EPA Science Inventory

    In tropical wet-dry climates, seasonal hydrologic cycles drive wetland plant community change and produce distinct seasonal plant assemblages. In this study, we examined the plant community response to seasonal flooding and drought in a large coastal freshwater wetland in northwe...

  11. Plant surface wax affects parasitoid's response to host footprints

    NASA Astrophysics Data System (ADS)

    Rostás, Michael; Ruf, Daniel; Zabka, Vanessa; Hildebrandt, Ulrich

    2008-10-01

    The plant surface is the substrate upon which herbivorous insects and natural enemies meet and thus represents the stage for interactions between the three trophic levels. Plant surfaces are covered by an epicuticular wax layer which is highly variable depending on species, cultivar or plant part. Differences in wax chemistry may modulate ecological interactions. We explored whether caterpillars of Spodoptera frugiperda, when walking over a plant surface, leave a chemical trail (kairomones) that can be detected by the parasitoid Cotesia marginiventris. Chemistry and micromorphology of cuticular waxes of two barley eceriferum wax mutants ( cer-za.126, cer-yp.949) and wild-type cv. Bonus (wt) were assessed. The plants were then used to investigate potential surface effects on the detectability of caterpillar kairomones. Here we provide evidence that C. marginiventris responds to chemical footprints of its host. Parasitoids were able to detect the kairomone on wild-type plants and on both cer mutants but the response to cer-yp.949 (reduced wax, high aldehyde fraction) was less pronounced. Experiments with caterpillar-treated wt and mutant leaves offered simultaneously, confirmed this observation: no difference in wasp response was found when wt was tested against cer-za.126 (reduced wax, wt-like chemical composition) but wt was significantly more attractive than cer-yp.949. This demonstrates for the first time that the wax layer can modulate the detectability of host kairomones.

  12. Plant community structure regulates responses of prairie soil respiration to decadal experimental warming.

    PubMed

    Xu, Xia; Shi, Zheng; Li, Dejun; Zhou, Xuhui; Sherry, Rebecca A; Luo, Yiqi

    2015-10-01

    Soil respiration is recognized to be influenced by temperature, moisture, and ecosystem production. However, little is known about how plant community structure regulates responses of soil respiration to climate change. Here, we used a 13-year field warming experiment to explore the mechanisms underlying plant community regulation on feedbacks of soil respiration to climate change in a tallgrass prairie in Oklahoma, USA. Infrared heaters were used to elevate temperature about 2 °C since November 1999. Annual clipping was used to mimic hay harvest. Our results showed that experimental warming significantly increased soil respiration approximately from 10% in the first 7 years (2000-2006) to 30% in the next 6 years (2007-2012). The two-stage warming stimulation of soil respiration was closely related to warming-induced increases in ecosystem production over the years. Moreover, we found that across the 13 years, warming-induced increases in soil respiration were positively affected by the proportion of aboveground net primary production (ANPP) contributed by C3 forbs. Functional composition of the plant community regulated warming-induced increases in soil respiration through the quantity and quality of organic matter inputs to soil and the amount of photosynthetic carbon (C) allocated belowground. Clipping, the interaction of clipping with warming, and warming-induced changes in soil temperature and moisture all had little effect on soil respiration over the years (all P > 0.05). Our results suggest that climate warming may drive an increase in soil respiration through altering composition of plant communities in grassland ecosystems.

  13. Feeding type affects microplastic ingestion in a coastal invertebrate community.

    PubMed

    Setälä, Outi; Norkko, Joanna; Lehtiniemi, Maiju

    2016-01-15

    Marine litter is one of the problems marine ecosystems face at present, coastal habitats and food webs being the most vulnerable as they are closest to the sources of litter. A range of animals (bivalves, free swimming crustaceans and benthic, deposit-feeding animals), of a coastal community of the northern Baltic Sea were exposed to relatively low concentrations of 10 μm microbeads. The experiment was carried out as a small scale mesocosm study to mimic natural habitat. The beads were ingested by all animals in all experimental concentrations (5, 50 and 250 beads mL(-1)). Bivalves (Mytilus trossulus, Macoma balthica) contained significantly higher amounts of beads compared with the other groups. Free-swimming crustaceans ingested more beads compared with the benthic animals that were feeding only on the sediment surface. Ingestion of the beads was concluded to be the result of particle concentration, feeding mode and the encounter rate in a patchy environment.

  14. How personal health budgets may affect community nursing teams.

    PubMed

    Hewitt-Taylor, Jaqui

    2008-08-01

    In social care, there has for some time been the option for individuals to use direct payments to manage their own support, and more recently individual budgets have been piloted. While this approach has not been available for healthcare payments, there is the potential for this to change. This paper outlines the implementation of direct payments and personal budgets and then discusses some of the issues which should be considered if such arrangements are introduced in healthcare. These include: preparing existing staff for such changes in funding and the implications for them; clarifying the new roles and responsibilities of community nursing teams, training opportunities for staff who are employed directly by individuals; staff recruitment and retention, and designing evaluation mechanisms which assess quality as well as cost.

  15. CO2 enrichment accelerates successional development of an understory plant community

    SciTech Connect

    Souza, Lara; Belote, R. Travis Travis; Kardol, Paul; Weltzin, Jake; Norby, Richard J

    2010-01-01

    Rising concentrations of atmospheric carbon dioxide ([CO{sub 2}]) may influence forest successional development and species composition of understory plant communities by altering biomass production of plant species of functional groups. Here, we describe how elevated [CO{sub 2}] (eCO{sub 2}) affects aboveground biomass within the understory community of a temperate deciduous forest at the Oak Ridge National Laboratory sweetgum (Liquidambar styraciflua) free-air carbon dioxide enrichment (FACE) facility in eastern Tennessee, USA. We asked if (i) CO{sub 2} enrichment affected total understory biomass and (ii) whether total biomass responses could be explained by changes in understory species composition or changes in relative abundance of functional groups through time. The FACE experiment started in 1998 with three rings receiving ambient [CO{sub 2}] (aCO{sub 2}) and two rings receiving eCO{sub 2}. From 2001 to 2003, we estimated species-specific, woody versus herbaceous and total aboveground biomass by harvesting four 1 x 0.5-m subplots within the established understory plant community in each FACE plot. In 2008, we estimated herbaceous biomass as previously but used allometric relationships to estimate woody biomass across two 5 x 5-m quadrats in each FACE plot. Across years, aboveground biomass of the understory community was on average 25% greater in eCO{sub 2} than in aCO{sub 2} plots. We could not detect differences in plant species composition between aCO{sub 2} and eCO{sub 2} treatments. However, we did observe shifts in the relative abundance of plant functional groups, which reflect important structural changes in the understory community. In 2001-03, little of the understory biomass was in woody species; herbaceous species made up 94% of the total understory biomass across [CO{sub 2}] treatments. Through time, woody species increased in importance, mostly in eCO{sub 2}, and in 2008, the contribution of herbaceous species to total understory biomass was

  16. A Hardy Plant Facilitates Nitrogen Removal via Microbial Communities in Subsurface Flow Constructed Wetlands in Winter

    NASA Astrophysics Data System (ADS)

    Wang, Penghe; Zhang, Hui; Zuo, Jie; Zhao, Dehua; Zou, Xiangxu; Zhu, Zhengjie; Jeelani, Nasreen; Leng, Xin; An, Shuqing

    2016-09-01

    The plants effect in subsurface flow constructed wetlands (SSF-CWs) is controversial, especially at low temperatures. Consequently, several SSF-CWs planted with Iris pseudacorus (CWI) or Typha orientalis Presl. (CWT) and several unplanted ones (CWC) were set up and fed with secondary effluent of sewage treatment plant during the winter in Eastern China. The 16S rDNA Illumina Miseq sequencing analysis indicated the positive effects of I. pseudacorus on the bacterial community richness and diversity in the substrate. Moreover, the community compositions of the bacteria involved with denitrification presented a significant difference in the three systems. Additionally, higher relative abundances of nitrifying bacteria (0.4140%, 0.2402% and 0.4318% for Nitrosomonas, Nitrosospira and Nitrospira, respectively) were recorded in CWI compared with CWT (0.2074%, 0.0648% and 0.0181%, respectively) and CWC (0.3013%, 0.1107% and 0.1185%, respectively). Meanwhile, the average removal rates of NH4+-N and TN in CWI showed a prominent advantage compared to CWC, but no distinct advantage was found in CWT. The hardy plant I. pseudacorus, which still had active root oxygen release in cold temperatures, positively affected the abundance of nitrifying bacteria in the substrate, and accordingly was supposed to contribute to a comparatively high nitrogen removal efficiency of the system during the winter.

  17. A Hardy Plant Facilitates Nitrogen Removal via Microbial Communities in Subsurface Flow Constructed Wetlands in Winter

    PubMed Central

    Wang, Penghe; Zhang, Hui; Zuo, Jie; Zhao, Dehua; Zou, Xiangxu; Zhu, Zhengjie; Jeelani, Nasreen; Leng, Xin; An, Shuqing

    2016-01-01

    The plants effect in subsurface flow constructed wetlands (SSF-CWs) is controversial, especially at low temperatures. Consequently, several SSF-CWs planted with Iris pseudacorus (CWI) or Typha orientalis Presl. (CWT) and several unplanted ones (CWC) were set up and fed with secondary effluent of sewage treatment plant during the winter in Eastern China. The 16S rDNA Illumina Miseq sequencing analysis indicated the positive effects of I. pseudacorus on the bacterial community richness and diversity in the substrate. Moreover, the community compositions of the bacteria involved with denitrification presented a significant difference in the three systems. Additionally, higher relative abundances of nitrifying bacteria (0.4140%, 0.2402% and 0.4318% for Nitrosomonas, Nitrosospira and Nitrospira, respectively) were recorded in CWI compared with CWT (0.2074%, 0.0648% and 0.0181%, respectively) and CWC (0.3013%, 0.1107% and 0.1185%, respectively). Meanwhile, the average removal rates of NH4+-N and TN in CWI showed a prominent advantage compared to CWC, but no distinct advantage was found in CWT. The hardy plant I. pseudacorus, which still had active root oxygen release in cold temperatures, positively affected the abundance of nitrifying bacteria in the substrate, and accordingly was supposed to contribute to a comparatively high nitrogen removal efficiency of the system during the winter. PMID:27646687

  18. Metaproteomics of complex microbial communities in biogas plants

    PubMed Central

    Heyer, Robert; Kohrs, Fabian; Reichl, Udo; Benndorf, Dirk

    2015-01-01

    Production of biogas from agricultural biomass or organic wastes is an important source of renewable energy. Although thousands of biogas plants (BGPs) are operating in Germany, there is still a significant potential to improve yields, e.g. from fibrous substrates. In addition, process stability should be optimized. Besides evaluating technical measures, improving our understanding of microbial communities involved into the biogas process is considered as key issue to achieve both goals. Microscopic and genetic approaches to analyse community composition provide valuable experimental data, but fail to detect presence of enzymes and overall metabolic activity of microbial communities. Therefore, metaproteomics can significantly contribute to elucidate critical steps in the conversion of biomass to methane as it delivers combined functional and phylogenetic data. Although metaproteomics analyses are challenged by sample impurities, sample complexity and redundant protein identification, and are still limited by the availability of genome sequences, recent studies have shown promising results. In the following, the workflow and potential pitfalls for metaproteomics of samples from full-scale BGP are discussed. In addition, the value of metaproteomics to contribute to the further advancement of microbial ecology is evaluated. Finally, synergistic effects expected when metaproteomics is combined with advanced imaging techniques, metagenomics, metatranscriptomics and metabolomics are addressed. PMID:25874383

  19. Classification and ordination of main plant communities along an altitudinal gradient in the arid and temperate climates of northeastern Mexico.

    PubMed

    Castillón, Eduardo Estrada; Arévalo, José Ramón; Quintanilla, José Ángel Villarreal; Rodríguez, María Magdalena Salinas; Encina-Domínguez, Juan Antonio; Rodríguez, Humberto González; Ayala, César Martín Cantú

    2015-10-01

    Quantitative data on the ecology of the main plant communities along an altitudinal gradient in northeastern Mexico were obtained with the aim of identifying the most important environmental variables that affect plant distribution and composition. The main threats to these communities were also investigated. Importance value index (IVi) of the 39 most important species and 16 environmental variables were recorded at 35 altitudinal gradients each spaced at intervals of at least 100-m altitude. Classification and ordination of vegetation showed six well-differentiated but overlapping plant communities: alpine meadow, cold conifer forest, mesic mixed forest, xeric scrub, Tamaulipan piedmont scrub, and halophytic grassland. Altitude, minimum and average temperatures, and organic matter content are the main variables affecting the plant distribution in northeastern Mexico. Urban growth, mechanized agriculture, and changes in land use are the main threats in the short and medium term to plant communities in this area. Climate change also seems to be having an impact at present or in the near future as shown by the presence of exotic shrubs from warmer areas in mesic and temperate areas inhabited by oak and oak-pine forest.

  20. Classification and ordination of main plant communities along an altitudinal gradient in the arid and temperate climates of northeastern Mexico

    NASA Astrophysics Data System (ADS)

    Castillón, Eduardo Estrada; Arévalo, José Ramón; Quintanilla, José Ángel Villarreal; Rodríguez, María Magdalena Salinas; Encina-Domínguez, Juan Antonio; Rodríguez, Humberto González; Ayala, César Martín Cantú

    2015-10-01

    Quantitative data on the ecology of the main plant communities along an altitudinal gradient in northeastern Mexico were obtained with the aim of identifying the most important environmental variables that affect plant distribution and composition. The main threats to these communities were also investigated. Importance value index (IVi) of the 39 most important species and 16 environmental variables were recorded at 35 altitudinal gradients each spaced at intervals of at least 100-m altitude. Classification and ordination of vegetation showed six well-differentiated but overlapping plant communities: alpine meadow, cold conifer forest, mesic mixed forest, xeric scrub, Tamaulipan piedmont scrub, and halophytic grassland. Altitude, minimum and average temperatures, and organic matter content are the main variables affecting the plant distribution in northeastern Mexico. Urban growth, mechanized agriculture, and changes in land use are the main threats in the short and medium term to plant communities in this area. Climate change also seems to be having an impact at present or in the near future as shown by the presence of exotic shrubs from warmer areas in mesic and temperate areas inhabited by oak and oak-pine forest.

  1. Analysis of factors affecting the accuracy, reproducibility, and interpretation of microbial community carbon source utilization patterns

    USGS Publications Warehouse

    Haack, S.K.; Garchow, H.; Klug, M.J.; Forney, L.J.

    1995-01-01

    We determined factors that affect responses of bacterial isolates and model bacterial communities to the 95 carbon substrates in Biolog microliter plates. For isolates and communities of three to six bacterial strains, substrate oxidation rates were typically nonlinear and were delayed by dilution of the inoculum. When inoculum density was controlled, patterns of positive and negative responses exhibited by microbial communities to each of the carbon sources were reproducible. Rates and extents of substrate oxidation by the communities were also reproducible but were not simply the sum of those exhibited by community members when tested separately. Replicates of the same model community clustered when analyzed by principal- components analysis (PCA), and model communities with different compositions were clearly separated un the first PCA axis, which accounted for >60% of the dataset variation. PCA discrimination among different model communities depended on the extent to which specific substrates were oxidized. However, the substrates interpreted by PCA to be most significant in distinguishing the communities changed with reading time, reflecting the nonlinearity of substrate oxidation rates. Although whole-community substrate utilization profiles were reproducible signatures for a given community, the extent of oxidation of specific substrates and the numbers or activities of microorganisms using those substrates in a given community were not correlated. Replicate soil samples varied significantly in the rate and extent of oxidation of seven tested substrates, suggesting microscale heterogeneity in composition of the soil microbial community.

  2. Cooperative Agreements to Support Communities Affected by the BP Oil Spill

    EPA Pesticide Factsheets

    The environmental justice cooperative agreements are designed to support communities in Alabama, Florida, Louisiana, Mississippi, and Texas that are directly affected by the Deepwater Horizon oil spill in the Gulf of Mexico.

  3. Links between plant and rhizoplane bacterial communities in grassland soils, characterized using molecular techniques.

    PubMed

    Nunan, Naoise; Daniell, Timothy J; Singh, Brajesh K; Papert, Artemis; McNicol, James W; Prosser, James I

    2005-11-01

    Molecular analysis of grassland rhizosphere soil has demonstrated complex and diverse bacterial communities, with resultant difficulties in detecting links between plant and bacterial communities. These studies have, however, analyzed "bulk" rhizosphere soil, rather than rhizoplane communities, which interact most closely with plants through utilization of root exudates. The aim of this study was to test the hypothesis that plant species was a major driver for bacterial rhizoplane community composition on individual plant roots. DNA extracted from individual roots was used to determine plant identity, by analysis of the plastid tRNA leucine (trnL) UAA gene intron, and plant-related bacterial communities. Bacterial communities were characterized by analysis of PCR-amplified 16S rRNA genes using two fingerprinting methods: terminal restriction fragment length polymorphisms (T-RFLP) and denaturing gradient gel electrophoresis (DGGE). Links between plant and bacterial rhizoplane communities could not be detected by visual examination of T-RFLP patterns or DGGE banding profiles. Statistical analysis of fingerprint patterns did not reveal a relationship between bacterial community composition and plant species but did demonstrate an influence of plant community composition. The data also indicated that topography and other, uncharacterized, environmental factors are important in driving bacterial community composition in grassland soils. T-RFLP had greater potential resolving power than DGGE, but findings from the two methods were not significantly different.

  4. Climate impacts on bird and plant communities from altered animal-plant interactions

    NASA Astrophysics Data System (ADS)

    Martin, Thomas E.; Maron, John L.

    2012-03-01

    The contribution of climate change to declining populations of organisms remains a question of outstanding concern. Much attention to declining populations has focused on how changing climate drives phenological mismatches between animals and their food. Effects of climate on plant communities may provide an alternative, but particularly powerful, influence on animal populations because plants provide their habitats. Here, we show that abundances of deciduous trees and associated songbirds have declined with decreasing snowfall over 22 years of study in montane Arizona, USA. We experimentally tested the hypothesis that declining snowfall indirectly influences plants and associated birds by allowing greater over-winter herbivory by elk (Cervus canadensis). We excluded elk from one of two paired snowmelt drainages (10 ha per drainage), and replicated this paired experiment across three distant canyons. Over six years, we reversed multi-decade declines in plant and bird populations by experimentally inhibiting heavy winter herbivory associated with declining snowfall. Moreover, predation rates on songbird nests decreased in exclosures, despite higher abundances of nest predators, demonstrating the over-riding importance of habitat quality to avian recruitment. Thus, our results suggest that climate impacts on plant-animal interactions can have forceful ramifying effects on plants, birds, and ecological interactions.

  5. Impacts of climate change drivers on C4 grassland productivity: scaling driver effects through the plant community.

    PubMed

    Polley, H Wayne; Derner, Justin D; Jackson, Robert B; Wilsey, Brian J; Fay, Philip A

    2014-07-01

    Climate change drivers affect plant community productivity via three pathways: (i) direct effects of drivers on plants; (ii) the response of species abundances to drivers (community response); and (iii) the feedback effect of community change on productivity (community effect). The contribution of each pathway to driver-productivity relationships depends on functional traits of dominant species. We used data from three experiments in Texas, USA, to assess the role of community dynamics in the aboveground net primary productivity (ANPP) response of C4 grasslands to two climate drivers applied singly: atmospheric CO2 enrichment and augmented summer precipitation. The ANPP-driver response differed among experiments because community responses and effects differed. ANPP increased by 80-120g m(-2) per 100 μl l(-1) rise in CO2 in separate experiments with pasture and tallgrass prairie assemblages. Augmenting ambient precipitation by 128mm during one summer month each year increased ANPP more in native than in exotic communities in a third experiment. The community effect accounted for 21-38% of the ANPP CO2 response in the prairie experiment but little of the response in the pasture experiment. The community response to CO2 was linked to species traits associated with greater soil water from reduced transpiration (e.g. greater height). Community effects on the ANPP CO2 response and the greater ANPP response of native than exotic communities to augmented precipitation depended on species differences in transpiration efficiency. These results indicate that feedbacks from community change influenced ANPP-driver responses. However, the species traits that regulated community effects on ANPP differed from the traits that determined how communities responded to drivers.

  6. Emerging Trends and Critical Issues Affecting Private Fund-Raising among Community Colleges.

    ERIC Educational Resources Information Center

    Jackson, Karen Luke; Glass, Jr., J. Conrad

    2000-01-01

    Identifies and rank orders emerging trends and critical issues affecting private fund-raising among community colleges. Development officers representing 42 North Carolina community colleges participated in the study. The greatest number of participants identified trends related to business and industry, the need for private funds, and increased…

  7. Teachers' Challenges, Strategies, and Support Needs in Schools Affected by Community Violence: A Qualitative Study

    ERIC Educational Resources Information Center

    Maring, Elisabeth F.; Koblinsky, Sally A.

    2013-01-01

    Background: Exposure to community violence compromises teacher effectiveness, student learning, and socioemotional well-being. This study examined the challenges, strategies, and support needs of teachers in urban schools affected by high levels of community violence. Methods: Twenty teachers from 3 urban middle schools with predominantly…

  8. Host plant affects morphometric variation of Diaphorina citri (Hemiptera: Liviidae)

    PubMed Central

    Paris, Thomson M.; Hall, David G.; Hentz, Matthew G.; Hetesy, Gabriella; Stansly, Philip A.

    2016-01-01

    The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, is one of the most serious citrus pests worldwide due to its role as vector of huanglongbing or citrus greening disease. While some optimal plant species for ACP oviposition and development have been identified, little is known of the influence of host plants on ACP size and shape. Our goal was to determine how size and shape of ACP wing and body size varies when development occurs on different host plants in a controlled rearing environment. ACP were reared on six different rutaceous species; Bergera koenigii, Citrus aurantifolia, Citrus macrophylla, Citrus maxima, Citrus taiwanica and Murraya paniculata. Adults were examined for morphometric variation using traditional and geometric analysis based on 12 traits or landmarks. ACP reared on C. taiwanica were consistently smaller than those reared on the other plant species. Wing aspect ratio also differed between C. maxima and C. taiwanica. Significant differences in shape were detected with those reared on M. paniculata having narrower wings than those reared on C. macrophylla. This study provides evidence of wing size and shape differences of ACP based on host plant species which potentially may impact dispersal. Further study is needed to determine if behavioral and physiological differences are associated with the observed phenotypic differences. PMID:27833820

  9. Host plant affects morphometric variation of Diaphorina citri (Hemiptera: Liviidae).

    PubMed

    Paris, Thomson M; Allan, Sandra A; Hall, David G; Hentz, Matthew G; Hetesy, Gabriella; Stansly, Philip A

    2016-01-01

    The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, is one of the most serious citrus pests worldwide due to its role as vector of huanglongbing or citrus greening disease. While some optimal plant species for ACP oviposition and development have been identified, little is known of the influence of host plants on ACP size and shape. Our goal was to determine how size and shape of ACP wing and body size varies when development occurs on different host plants in a controlled rearing environment. ACP were reared on six different rutaceous species; Bergera koenigii, Citrus aurantifolia, Citrus macrophylla, Citrus maxima, Citrus taiwanica and Murraya paniculata. Adults were examined for morphometric variation using traditional and geometric analysis based on 12 traits or landmarks. ACP reared on C. taiwanica were consistently smaller than those reared on the other plant species. Wing aspect ratio also differed between C. maxima and C. taiwanica. Significant differences in shape were detected with those reared on M. paniculata having narrower wings than those reared on C. macrophylla. This study provides evidence of wing size and shape differences of ACP based on host plant species which potentially may impact dispersal. Further study is needed to determine if behavioral and physiological differences are associated with the observed phenotypic differences.

  10. Understanding Plant Community Responses to Combinations of Biotic and Abiotic Factors in Different Phases of the Plant Growth Cycle

    PubMed Central

    Wood, Kevin A.; Stillman, Richard A.; Clarke, Ralph T.; Daunt, Francis; O’Hare, Matthew T.

    2012-01-01

    Understanding plant community responses to combinations of biotic and abiotic factors is critical for predicting ecosystem response to environmental change. However, studies of plant community regulation have seldom considered how responses to such factors vary with the different phases of the plant growth cycle. To address this deficit we studied an aquatic plant community in an ecosystem subject to gradients in mute swan (Cygnus olor) herbivory, riparian shading, water temperature and distance downstream of the river source. We quantified abundance, species richness, evenness, flowering and dominance in relation to biotic and abiotic factors during the growth-, peak-, and recession-phases of the plant growth cycle. We show that the relative importance of biotic and abiotic factors varied between plant community properties and between different phases of the plant growth cycle. Herbivory became more important during the later phases of peak abundance and recession due to an influx of swans from adjacent pasture fields. Shading by riparian vegetation also had a greater depressing effect on biomass in later seasons, probably due to increased leaf abundance reducing light intensity reaching the aquatic plants. The effect of temperature on community diversity varied between upstream and downstream sites by altering the relative competitiveness of species at these sites. These results highlight the importance of seasonal patterns in the regulation of plant community structure and function by multiple factors. PMID:23166777

  11. Understanding plant community responses to combinations of biotic and abiotic factors in different phases of the plant growth cycle.

    PubMed

    Wood, Kevin A; Stillman, Richard A; Clarke, Ralph T; Daunt, Francis; O'Hare, Matthew T

    2012-01-01

    Understanding plant community responses to combinations of biotic and abiotic factors is critical for predicting ecosystem response to environmental change. However, studies of plant community regulation have seldom considered how responses to such factors vary with the different phases of the plant growth cycle. To address this deficit we studied an aquatic plant community in an ecosystem subject to gradients in mute swan (Cygnus olor) herbivory, riparian shading, water temperature and distance downstream of the river source. We quantified abundance, species richness, evenness, flowering and dominance in relation to biotic and abiotic factors during the growth-, peak-, and recession-phases of the plant growth cycle. We show that the relative importance of biotic and abiotic factors varied between plant community properties and between different phases of the plant growth cycle. Herbivory became more important during the later phases of peak abundance and recession due to an influx of swans from adjacent pasture fields. Shading by riparian vegetation also had a greater depressing effect on biomass in later seasons, probably due to increased leaf abundance reducing light intensity reaching the aquatic plants. The effect of temperature on community diversity varied between upstream and downstream sites by altering the relative competitiveness of species at these sites. These results highlight the importance of seasonal patterns in the regulation of plant community structure and function by multiple factors.

  12. Incorporating Peatland Plant Communities into the Enzymic 'Latch' Hypothesis: Can Vegetation Influence Carbon Storage Mechanisms?

    NASA Astrophysics Data System (ADS)

    Romanowicz, K. J.; Daniels, A. L.; Potvin, L. R.; Kane, E. S.; Kolka, R. K.; Chimner, R. A.; Lilleskov, E. A.

    2012-12-01

    High water table conditions in peatland ecosystems are known to favor plant production over decomposition and carbon is stored. Dominant plant communities change in response to water table but little is know of how these changes affect belowground carbon storage. One hypothesis known as the enzymic 'latch' proposed by Freeman et al. suggests that oxygen limitations due to high water table conditions inhibit microorganisms from synthesizing specific extracellular enzymes essential for carbon and nutrient mineralization, allowing carbon to be stored as decomposition is reduced. Yet, this hypothesis excludes plant community interactions on carbon storage. We hypothesize that the dominant vascular plant communities, sedges and ericaceous shrubs, will have inherently different effects on peatland carbon storage, especially in response to declines in water table. Sedges greatly increase in abundance following water table decline and create extensive carbon oxidation and mineralization hotspots through the production of deep roots with aerenchyma (air channels in roots). Increased oxidation may enhance aerobic microbial activity including increased enzyme activity, leading to peat subsidence and carbon loss. In contrast, ericaceous shrubs utilize enzymatically active ericoid mycorrhizal fungi that suppress free-living heterotrophs, promoting decreased carbon mineralization by mediating changes in rhizosphere microbial communities and enzyme activity regardless of water table declines. Beginning May 2010, bog monoliths were harvested, housed in mesocosm chambers, and manipulated into three vegetation treatments: unmanipulated (+sedge, +Ericaceae), sedge (+sedge, -Ericaceae), and Ericaceae (-sedge, +Ericaceae). Following vegetation manipulations, two distinct water table manipulations targeting water table seasonal profiles were implemented: (low intra-seasonal variability, higher mean water table; high intra-seasonal variability, lower mean water table). In 2012, peat

  13. Land-use intensification effects on functional properties in tropical plant communities.

    PubMed

    Carreño-Rocabado, Geovana; Peña-Claros, Marielos; Bongers, Frans; Díaz, Sandra; Quetier, Fabien; Chuviña, José; Poorter, Lourens

    2016-01-01

    There is consensus that plant diversity and ecosystem processes are negatively affected by land-use intensification (LUI), but, at the same time, there is empirical evidence that a large heterogeneity can be found in the responses. This heterogeneity is especially poorly understood in tropical ecosystems. We evaluated changes in community functional properties across five common land-use types in the wet tropics with different land-use intensity: mature forest, logged forest, secondary forest, agricultural land, and pastureland, located in the lowlands of Bolivia. For the dominant plant species, we measured 12 functional response traits related to their life history, acquisition and conservation of resources, plant domestication, and breeding. We used three single-trait metrics to describe community functional properties: community abundance-weighted mean (CWM) traits values, coefficient of variation, and kurtosis of distribution. The CWM of all 12 traits clearly responded to LUI. Overall, we found that an increase in LUI resulted in communities dominated by plants with acquisitive leaf trait values. However, contrary to our expectations, secondary forests had more conservative trait values (i.e., lower specific leaf area) than mature and logged forest, probably because they were dominated by palm species. Functional variation peaked at intermediate land-use intensity (high coefficient of variation and low kurtosis), which included secondary forest but, unexpectedly, also agricultural land, which is an intensely managed system. The high functional variation of these systems is due to a combination of how response traits (and species) are filtered out by biophysical filters and how management practices introduced a range of exotic species and their trait values into the local species pool. Our results showed that, at local scales and depending on prevailing environmental and management practices, LUI does not necessarily result in communities with more acquisitive

  14. Cadmium content of plants as affected by soil cadmium concentration

    SciTech Connect

    Lehoczky, E.; Szabados, I.; Marth, P.

    1996-12-31

    Pot experiments were conducted in greenhouse conditions to study the effects of increasing cadmium (Cd) levels on biomass production and Cd contents in corn, (Zea mays L.), garlic (Allium sativum L.), and spinach (Spinacia oleracea L.). Plants were grown in two soil types: Eutric cambisol soil and A gleyic luvisol soil. Spinach proved to be the most sensitive to Cd treatments as its biomass considerably decreased with the increasing Cd levels. Cadmium contents of the three crops increased with increasing levels of Cd applications. Statistical differences were observed in the Cd contents of crops depending on soil type. With the same Cd rates, Cd tissue concentration of test plants grown in the strongly acidic Gleyic luvisol soil were many times higher than that of plants grown in a neutral Eutric cambisol soil. 14 refs., 4 tabs.

  15. Composition of hydroponic medium affects thorium uptake by tobacco plants.

    PubMed

    Soudek, Petr; Kufner, Daniel; Petrová, Sárka; Mihaljevič, Martin; Vaněk, Tomáš

    2013-08-01

    The ability of thorium uptake as well as responses to heavy metal stress were tested in tobacco cultivar La Burley 21. Thorium was accumulated preferentially in the root system. The presence of citric, tartaric and oxalic acids in hydroponic medium increased thorium accumulation in all plant organs. On the other hand, the addition of diamines and polyamines, the important antioxidants in plants, resulted in decrease of thorium accumulation, especially in the root system. Negative correlation was found between putrescine concentration and thorium accumulation. Nevertheless, the most important factor influencing the accumulation of thorium was the absence of phosphate ions in a hydroponic medium that caused more than 10-fold increase of thorium uptake in all plant parts. Accumulation and distribution of thorium was followed in six cultivars and 14 selected transformants. Cultivar La Barley 21 represented an average between the tested genotypes, having a very good distribution ratio between roots, stems and leaves.

  16. PERCEIVED RACISM AND NEGATIVE AFFECT: ANALYSES OF TRAIT AND STATE MEASURES OF AFFECT IN A COMMUNITY SAMPLE.

    PubMed

    Brondolo, Elizabeth; Brady, Nisha; Thompson, Shola; Tobin, Jonathan N; Cassells, Andrea; Sweeney, Monica; McFarlane, Delano; Contrada, Richard J

    2008-02-01

    Racism is a significant psychosocial stressor that is hypothesized to have negative psychological and physical health consequences. The Reserve Capacity Model (Gallo & Matthews, 2003) suggests that low socioeconomic status may influence health through its effects on negative affect. We extend this model to study the effects of racism, examining the association of lifetime perceived racism to trait and daily negative affect. A multiethnic sample of 362 American-born Black and Latino adults completed the Perceived Ethnic Discrimination Questionnaire-Community Version (PEDQ-CV). Trait negative affect was assessed with the Positive and Negative Affect Schedule (PANAS), and state negative affect was measured using ecological momentary assessments (EMA), in the form of an electronic diary. Analyses revealed a significant relationship of lifetime perceived racism to both daily negative affect and trait negative affect, even when controlling for trait hostility and socioeconomic status. The relationship of perceived racism to negative affect was moderated by education, such that the relationships were strongest for those with less than a high school education. The findings support aspects of the Reserve Capacity Model and identify pathways through which perceived racism may affect health status.

  17. Treatment of Diarrhoea in Rural African Communities: An Overview of Measures to Maximise the Medicinal Potentials of Indigenous Plants

    PubMed Central

    Njume, Collise; Goduka, Nomalungelo I.

    2012-01-01

    Diarrhoea is a major cause of morbidity and mortality in rural communities in Africa, particularly in children under the age of five. This calls for the development of cost effective alternative strategies such as the use of herbal drugs in the treatment of diarrhoea in these communities. Expenses associated with the use of orthodox medicines have generated renewed interest and reliance on indigenous medicinal plants in the treatment and management of diarrhoeal infections in rural communities. The properties of many phenolic constituents of medicinal plants such as their ability to inhibit enteropooling and delay gastrointestinal transit are very useful in the control of diarrhoea, but problems such as scarcity of valuable medicinal plants, lack of standardization of methods of preparation, poor storage conditions and incertitude in some traditional health practitioners are issues that affect the efficacy and the practice of traditional medicine in rural African communities. This review appraises the current strategies used in the treatment of diarrhoea according to the Western orthodox and indigenous African health-care systems and points out major areas that could be targeted by health-promotion efforts as a means to improve management and alleviate suffering associated with diarrhoea in rural areas of the developing world. Community education and research with indigenous knowledge holders on ways to maximise the medicinal potentials in indigenous plants could improve diarrhoea management in African rural communities. PMID:23202823

  18. How neighbor canopy architecture affects target plant performance

    SciTech Connect

    Tremmel, D.C.; Bazzaz, F.A. )

    1993-10-01

    Plant competition occurs through the negative effects that individual plants have on resource availability to neighboring individuals. Therefore competition experiments need to examine how different species change resource availability to their neighbors, and how different species respond to these changes-allocationally, architecturally, and physiologically-through time. In a greenhouse study we used a model system of annuals to examine how canopies of species having differing morphologies differed in their architectures and light-interception abilities, and how different species performed when grown in these canopies. Abutilon theophrasti, Datura stramonium, and Polygonum pensylvanicum were grown as [open quotes]targets[close quotes]. Plants were grown in pots, with one target plant and four neighbor plants. Detailed measurements of neighbor canopy structure and target plant canopy architecture were made at five harvests. Species with different morphologies showed large differences in canopy structure, particularly when grass and forb species were compared. Setaria, a grass, had a more open canopy than the other species (all forbs), and was a consistently weak competitor. Overall, however, the relative effects of different neighbors on target biomass varied with target species. Target biomass was poorly correlated with neighbor biomass and leaf area, but was highly correlated with a measure of target light-interception ability that took into account both target leaf deployment and neighbor light interception. Despite clear differences among neighbor species in canopy structure and effect on light penetration, the results suggest no broad generalizations about the effects of different species as neighbors. Knowledge of morphological, physiological, and life history characteristics of both the target and neighbor species may be necessary to explain the results of their competition. 53 refs., 4 figs., 4 tabs.

  19. Plant extracts affect in vitro rumen microbial fermentation.

    PubMed

    Busquet, M; Calsamiglia, S; Ferret, A; Kamel, C

    2006-02-01

    Different doses of 12 plant extracts and 6 secondary plant metabolites were incubated for 24 h in diluted ruminal fluid with a 50:50 forage:concentrate diet. Treatments were: control (no additive), plant extracts (anise oil, cade oil, capsicum oil, cinnamon oil, clove bud oil, dill oil, fenugreek, garlic oil, ginger oil, oregano oil, tea tree oil, and yucca), and secondary plant metabolites (anethol, benzyl salicylate, carvacrol, carvone, cinnamaldehyde, and eugenol). Each treatment was supplied at 3, 30, 300, and 3,000 mg/L of culture fluid. At 3,000 mg/L, most treatments decreased total volatile fatty acid concentration, but cade oil, capsicum oil, dill oil, fenugreek, ginger oil, and yucca had no effect. Different doses of anethol, anise oil, carvone, and tea tree oil decreased the proportion of acetate and propionate, which suggests that these compounds may not be nutritionally beneficial to dairy cattle. Garlic oil (300 and 3,000 mg/L) and benzyl salicylate (300 and 3,000 mg/L) reduced acetate and increased propionate and butyrate proportions, suggesting that methane production was inhibited. At 3,000 mg/L, capsicum oil, carvacrol, carvone, cinnamaldehyde, cinnamon oil, clove bud oil, eugenol, fenugreek, and oregano oil resulted in a 30 to 50% reduction in ammonia N concentration. Careful selection and combination of these extracts may allow the manipulation of rumen microbial fermentation.

  20. Host plant affects morphometric variation of Diaphorina citri (Hemiptera: Liviidae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Asian citrus psyllid (ACP), due to its potential to vector the pathogen causing citrus greening disease or huanglongbing, is one of the most serious citrus pests worldwide. While optimal plant cultivars for ACP oviposition and development have been determined, little is known of the influence of...

  1. Maximizing plant density affects broccoli yield and quality

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increased demand for fresh market bunch broccoli (Brassica oleracea L. var. italica) has led to increased production along the United States east coast. Maximizing broccoli yields is a primary concern for quickly expanding southeastern commercial markets. This broccoli plant density study was carr...

  2. Grazing Intensity Does Not Affect Plant Diversity in Shortgrass Steppe

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Responses of livestock gain and forage production to grazing intensity in shortgrass steppe are well-established, but effects on basal cover and plant diversity are less so. A long-term grazing intensity study was initiated on shortgrass steppe at the Central Plains Experimental Range (USDA-Agricult...

  3. Above- and belowground linkages in Sphagnum peatland: climate warming affects plant-microbial interactions.

    PubMed

    Jassey, Vincent E J; Chiapusio, Geneviève; Binet, Philippe; Buttler, Alexandre; Laggoun-Défarge, Fatima; Delarue, Frédéric; Bernard, Nadine; Mitchell, Edward A D; Toussaint, Marie-Laure; Francez, André-Jean; Gilbert, Daniel

    2013-03-01

    Peatlands contain approximately one third of all soil organic carbon (SOC). Warming can alter above- and belowground linkages that regulate soil organic carbon dynamics and C-balance in peatlands. Here we examine the multiyear impact of in situ experimental warming on the microbial food web, vegetation, and their feedbacks with soil chemistry. We provide evidence of both positive and negative impacts of warming on specific microbial functional groups, leading to destabilization of the microbial food web. We observed a strong reduction (70%) in the biomass of top-predators (testate amoebae) in warmed plots. Such a loss caused a shortening of microbial food chains, which in turn stimulated microbial activity, leading to slight increases in levels of nutrients and labile C in water. We further show that warming altered the regulatory role of Sphagnum-polyphenols on microbial community structure with a potential inhibition of top predators. In addition, warming caused a decrease in Sphagnum cover and an increase in vascular plant cover. Using structural equation modelling, we show that changes in the microbial food web affected the relationships between plants, soil water chemistry, and microbial communities. These results suggest that warming will destabilize C and nutrient recycling of peatlands via changes in above- and belowground linkages, and therefore, the microbial food web associated with mosses will feedback positively to global warming by destabilizing the carbon cycle. This study confirms that microbial food webs thus constitute a key element in the functioning of peatland ecosystems. Their study can help understand how mosses, as ecosystem engineers, tightly regulate biogeochemical cycling and climate feedback in peatlands.

  4. Communities of different plant diversity respond similarly to drought stress: experimental evidence from field non-weeded and greenhouse conditions.

    PubMed

    Lanta, Vojtěch; Doležal, Jiří; Zemková, Lenka; Lepš, Jan

    2012-06-01

    Accelerating rate of species loss has prompted researchers to study the role of species diversity in processes that control ecosystem functioning. Although negative impact of species loss has been documented, the evidence concerning its impact on ecosystem stability is still limited. Here, we studied the effects of declining species and functional diversity on plant community responses to drought in the field (open to weed colonization) and greenhouse conditions. Both species and functional diversity positively affected the average yields of field communities. However, this pattern was similar in both drought-stressed and control plots. No effect of diversity on community resistance, biomass recovery after drought and resilience was found because drought reduced biomass production similarly at each level of diversity by approximately 30%. The use of dissimilarity (characterized by Euclidean distance) revealed higher variation under changing environments (drought-stressed vs. control) in more diverse communities compared to less species-rich assemblages. In the greenhouse experiment, the effect of species diversity affected community resistance, indicating that more diverse communities suffered more from drought than species-poor ones. We conclude that our study did not support the insurance hypothesis (stability properties of a community should increase with species richness) because species diversity had an equivocal effect on ecosystem resistance and resilience in an environment held under non-weeded practice, regardless of the positive relationship between sown species diversity and community biomass production. More species-rich communities were less resistant against drought-stressed conditions than species-poor ones grown in greenhouse conditions.

  5. Communities of different plant diversity respond similarly to drought stress: experimental evidence from field non-weeded and greenhouse conditions

    NASA Astrophysics Data System (ADS)

    Lanta, Vojtěch; Doležal, Jiří; Zemková, Lenka; Lepš, Jan

    2012-06-01

    Accelerating rate of species loss has prompted researchers to study the role of species diversity in processes that control ecosystem functioning. Although negative impact of species loss has been documented, the evidence concerning its impact on ecosystem stability is still limited. Here, we studied the effects of declining species and functional diversity on plant community responses to drought in the field (open to weed colonization) and greenhouse conditions. Both species and functional diversity positively affected the average yields of field communities. However, this pattern was similar in both drought-stressed and control plots. No effect of diversity on community resistance, biomass recovery after drought and resilience was found because drought reduced biomass production similarly at each level of diversity by approximately 30 %. The use of dissimilarity (characterized by Euclidean distance) revealed higher variation under changing environments (drought-stressed vs. control) in more diverse communities compared to less species-rich assemblages. In the greenhouse experiment, the effect of species diversity affected community resistance, indicating that more diverse communities suffered more from drought than species-poor ones. We conclude that our study did not support the insurance hypothesis (stability properties of a community should increase with species richness) because species diversity had an equivocal effect on ecosystem resistance and resilience in an environment held under non-weeded practice, regardless of the positive relationship between sown species diversity and community biomass production. More species-rich communities were less resistant against drought-stressed conditions than species-poor ones grown in greenhouse conditions.

  6. Climate impacts on bird and plant communities from altered animal-plant interactions

    USGS Publications Warehouse

    Martin, Thomas E.; Maron, John L.

    2012-01-01

    The contribution of climate change to declining populations of organisms remains a question of outstanding concern. Much attention to declining populations has focused on how changing climate drives phenological mismatches between animals and their food. Effects of climate on plant communities may provide an alternative, but particularly powerful, influence on animal populations because plants provide their habitats. Here, we show that abundances of deciduous trees and associated songbirds have declined with decreasing snowfall over 22 years of study in montane Arizona, USA. We experimentally tested the hypothesis that declining snowfall indirectly influences plants and associated birds by allowing greater over-winter herbivory by elk (Cervus canadensis). We excluded elk from one of two paired snowmelt drainages (10 ha per drainage), and replicated this paired experiment across three distant canyons. Over six years, we reversed multi-decade declines in plant and bird populations by experimentally inhibiting heavy winter herbivory associated with declining snowfall. Moreover, predation rates on songbird nests decreased in exclosures, despite higher abundances of nest predators, demonstrating the over-riding importance of habitat quality to avian recruitment. Thus, our results suggest that climate impacts on plant–animal interactions can have forceful ramifying effects on plants, birds, and ecological interactions.

  7. Linkage between bacterial and fungal rhizosphere communities in hydrocarbon-contaminated soils is related to plant phylogeny

    PubMed Central

    Bell, Terrence H; El-Din Hassan, Saad; Lauron-Moreau, Aurélien; Al-Otaibi, Fahad; Hijri, Mohamed; Yergeau, Etienne; St-Arnaud, Marc

    2014-01-01

    Phytoremediation is an attractive alternative to excavating and chemically treating contaminated soils. Certain plants can directly bioremediate by sequestering and/or transforming pollutants, but plants may also enhance bioremediation by promoting contaminant-degrading microorganisms in soils. In this study, we used high-throughput sequencing of bacterial 16S rRNA genes and the fungal internal transcribed spacer (ITS) region to compare the community composition of 66 soil samples from the rhizosphere of planted willows (Salix spp.) and six unplanted control samples at the site of a former petrochemical plant. The Bray–Curtis distance between bacterial communities across willow cultivars was significantly correlated with the distance between fungal communities in uncontaminated and moderately contaminated soils but not in highly contaminated (HC) soils (>2000 mg kg−1 hydrocarbons). The mean dissimilarity between fungal, but not bacterial, communities from the rhizosphere of different cultivars increased substantially in the HC blocks. This divergence was partly related to high fungal sensitivity to hydrocarbon contaminants, as demonstrated by reduced Shannon diversity, but also to a stronger influence of willows on fungal communities. Abundance of the fungal class Pezizomycetes in HC soils was directly related to willow phylogeny, with Pezizomycetes dominating the rhizosphere of a monophyletic cluster of cultivars, while remaining in low relative abundance in other soils. This has implications for plant selection in phytoremediation, as fungal associations may affect the health of introduced plants and the success of co-inoculated microbial strains. An integrated understanding of the relationships between fungi, bacteria and plants will enable the design of treatments that specifically promote effective bioremediating communities. PMID:23985744

  8. Driving factors of the communities of phytophagous and predatory mites in a physic nut plantation and spontaneous plants associated.

    PubMed

    Cruz, Wilton P; Sarmento, Renato A; Teodoro, Adenir V; Neto, Marçal P; Ignacio, Maíra

    2013-08-01

    Seasonal changes in climate and plant diversity are known to affect the population dynamics of both pests and natural enemies within agroecosystems. In Brazil, spontaneous plants are usually tolerated in small-scale physic nut plantations over the year, which in turn may mediate interactions between pests and natural enemies within this agroecosystem. Here, we aimed to access the influence of seasonal variation of abiotic (temperature, relative humidity and rainfall) and biotic (diversity of spontaneous plants, overall richness and density of mites) factors on the communities of phytophagous and predatory mites found in a physic nut plantation and its associated spontaneous plants. Mite sampling was monthly conducted in dicotyledonous and monocotyledonous leaves of spontaneous plants as well as in physic nut shrubs over an entire year. In the dry season there was a higher abundance of phytophagous mites (Tenuipalpidae, Tarsonemidae and Tetranychidae) on spontaneous plants than on physic nut shrubs, while predatory mites (Phytoseiidae) showed the opposite pattern. The overall density of mites on spontaneous plants increased with relative humidity and diversity of spontaneous plants. Rainfall was the variable that most influenced the density of mites inhabiting physic nut shrubs. Agroecosystems comprising spontaneous plants associated with crops harbour a rich mite community including species of different trophic levels which potentially benefit natural pest control due to increased diversity and abundance of natural enemies.

  9. Plant Litter Submergence Affects the Water Quality of a Constructed Wetland.

    PubMed

    Pan, Xu; Ping, Yunmei; Cui, Lijuan; Li, Wei; Zhang, Xiaodong; Zhou, Jian; Yu, Fei-Hai; Prinzing, Andreas

    2017-01-01

    Plant litter is an indispensable component of constructed wetlands, but how the submergence of plant litter affects their ecosystem functions and services, such as water purification, is still unclear. Moreover, it is also unclear whether the effects of plant litter submergence depend on other factors such as the duration of litter submergence, water source or litter species identity. Here we conducted a greenhouse experiment by submerging the litter of 7 wetland plant species into three types of water substrates and monitoring changes in water nutrient concentrations. Litter submergence affected water quality positively via decreasing the concentration of nitrate nitrogen and negatively via increasing the concentrations of total nitrogen, ammonium nitrogen and total phosphorus. The effects of litter submergence depended on the duration of litter submergence, the water source, the litter species identity, and the plant life form. Different plant species had different effects on the water nutrient concentrations during litter submergence, and the effects of floating plants might be more negative than that of emergent plants. These results are novel evidence of how the submergence of different plant (life form) litter may affect the purification function of constructed wetlands. For water at low eutrophication levels, submerging a relative small amount of plant litter might improve water quality, via benefiting the denitrification process in water. These findings emphasized the management of floating plant litter (a potential removal) during the maintenance of human-controlled wetland ecosystems and provided a potential tool to improve the water quality of constructed wetlands via submerging plant litter of different types.

  10. Humans as Long-Distance Dispersers of Rural Plant Communities

    PubMed Central

    Auffret, Alistair G.; Cousins, Sara A. O.

    2013-01-01

    Humans are known for their capacity to disperse organisms long distances. Long-distance dispersal can be important for species threatened by habitat destruction, but research into human-mediated dispersal is often focused upon few and/or invasive species. Here we use citizen science to identify the capacity for humans to disperse seeds on their clothes and footwear from a known species pool in a valuable habitat, allowing for an assessment of the fraction and types of species dispersed by humans in an alternative context. We collected material from volunteers cutting 48 species-rich meadows throughout Sweden. We counted 24 354 seeds of 197 species, representing 34% of the available species pool, including several rare and protected species. However, 71 species (36%) are considered invasive elsewhere in the world. Trait analysis showed that seeds with hooks or other appendages were more likely to be dispersed by humans, as well as those with a persistent seed bank. More activity in a meadow resulted in more dispersal, both in terms of species and representation of the source communities. Average potential dispersal distances were measured at 13 km. We consider humans capable seed dispersers, transporting a significant proportion of the plant communities in which they are active, just like more traditional vectors such as livestock. When rural populations were larger, people might have been regular and effective seed dispersers, and the net rural-urban migration resulting in a reduction in humans in the landscape may have exacerbated the dispersal failure evident in declining plant populations today. With the fragmentation of habitat and changes in land use resulting from agricultural change, and the increased mobility of humans worldwide, the dispersal role of humans may have shifted from providers of regular local and landscape dispersal to providers of much rarer long-distance and regional dispersal, and international invasion. PMID:23658770

  11. Effects of flooding, salinity and herbivory on coastal plant communities, Louisiana, United States

    USGS Publications Warehouse

    Gough, L.; Grace, J.B.

    1998-01-01

    Flooding and salinity stress are predicted to increase in coastal Louisiana as relative sea level rise (RSLR) continues in the Gulf of Mexico region. Although wetland plant species are adapted to these stressors, questions persist as to how marshes may respond to changed abiotic variables caused by RSLR, and how herbivory by native and non-native mammals may affect this response. The effects of altered flooding and salinity on coastal marsh communities were examined in two field experiments that simultaneously manipulated herbivore pressure. Marsh sods subjected to increased or decreased flooding (by lowering or raising sods, respectively), and increased or decreased salinity (by reciprocally transplanting sods between a brackish and fresh marsh), were monitored inside and outside mammalian herbivore exclosures for three growing seasons. Increased flooding stress reduced species numbers and biomass; alleviating flooding stress did not significantly alter species numbers while community biomass increased. Increased salinity reduced species numbers and biomass, more so if herbivores were present. Decreasing salinity had an unexpected effect: herbivores selectively consumed plants transplanted from the higher-salinity site. In plots protected from herbivory, decreased salinity had little effect on species numbers or biomass, but community composition changed. Overall, herbivore pressure further reduced species richness and biomass under conditions of increased flooding and increased salinity, supporting other findings that coastal marsh species can tolerate increasingly stressful conditions unless another factor, e.g., herbivory, is also present. Also, species dropped out of more stressful treatments much faster than they were added when stresses were alleviated, likely due to restrictions on dispersal. The rate at which plant communities will shift as a result of changed abiotic variables will determine if marshes remain viable when subjected to RSLR.

  12. Relationships of human disturbance, bird communities, and plant communities along the land-water interface of a large reservoir.

    PubMed

    Francl, Karen E; Schnell, Gary D

    2002-01-01

    We examined the relationships of human activity, bird communities, and plant communities along the land-water interface of Lake Texoma, a large human-made reservoir on the Texas-Oklahoma border. Measurements of human activity, plant surveys, and bird surveys were performed at 40 paired transects, one with human disturbance, the other undisturbed. Both principal components and correspondence analyses of bird-survey data separated disturbed sites from paired undisturbed sites, and typical disturbance-tolerant species from those less tolerant of human activity. Compared to undisturbed sites, disturbed sites tended to have more individual birds per survey, pavement, and mowed lawns, and less canopy, vegetation volume, and vegetation vertical diversity. A principal components analysis of quantitative disturbance measurements revealed that most bird and plant measures were highly correlated with the first disturbance component. However, the correlation between birds and human activity was much stronger than that between birds and plants, or between plants and disturbance. Our data suggest that bird-species composition is regulated more by human activity than by plant-community composition. Also, in this system, bird communities are a better choice than plant communities to index the effect of human disturbance. To maintain regional diversity of both birds and plants, undisturbed areas should be maintained around reservoirs.

  13. Phylogenetic diversity of dominant bacterial and archaeal communities in plant-microbial fuel cells using rice plants.

    PubMed

    Ahn, Jae-Hyung; Jeong, Woo-Suk; Choi, Min-Young; Kim, Byung-Yong; Song, Jaekyeong; Weon, Hang-Yeon

    2014-12-28

    In this study, the phylogenetic diversities of bacterial and archaeal communities in a plantmicrobial fuel cell (P-MFC) were investigated together with the environmental parameters, affecting its performance by using rice as a model plant. The beneficial effect of the plant appeared only during a certain period of the rice-growing season, at which point the maximum power density was approximately 3-fold higher with rice plants. The temperature, electrical conductivity (EC), and pH in the cathodic and anodic compartments changed considerably during the rice-growing season, and a higher temperature, reduced difference in pH between the cathodic and anodic compartments, and higher EC were advantageous to the performance of the P-MFC. A 16S rRNA pyrosequencing analysis showed that the 16S rRNAs of Deltaproteobacteria and those of Gammaproteobacteria were enriched on the anodes and the cathodes, respectively, when the electrical circuit was connected. At the species level, the operational taxonomic units (OTUs) related to Rhizobiales, Geobacter, Myxococcus, Deferrisoma, and Desulfobulbus were enriched on the anodes, while an OTU related to Acidiferrobacter thiooxydans occupied the highest proportion on the cathodes and occurred only when the circuit was connected. Furthermore, the connection of the electrical circuit decreased the abundance of 16S rRNAs of acetotrophic methanogens and increased that of hydrogenotrophic methanogens. The control of these physicochemical and microbiological factors is expected to be able to improve the performance of P-MFCs.

  14. Bacterial communities involved in sulfur transformations in wastewater treatment plants.

    PubMed

    Meyer, Daniel Derrossi; de Andrade, Pedro Avelino Maia; Durrer, Ademir; Andreote, Fernando Dini; Corção, Gertrudes; Brandelli, Adriano

    2016-12-01

    The main sulfate-reducing (SRB) and sulfur-oxidizing bacteria (SOB) in six wastewater treatment plants (WWTPs) located at southern Brazil were described based on high-throughput sequencing of the 16S rDNA. Specific taxa of SRB and SOB were correlated with some abiotic factors, such as the source of the wastewater, oxygen content, sample type, and physical chemical attributes of these WWTPs. When the 22 families of SRB and SOB were clustered together, the samples presented a striking distribution, demonstrating grouping patterns according to the sample type. For SOB, the most abundant families were Spirochaetaceae, Chromatiaceae, Helicobacteriaceae, Rhodospirillaceae, and Neisseriaceae, whereas, for SRB, were Syntrophaceae, Desulfobacteraceae, Nitrospiraceae, and Desulfovibriaceae. The structure and composition of the major families related to the sulfur cycle were also influenced by six chemical attributes (sulfur, potassium, zinc, manganese, phosphorus, and nitrogen). Sulfur was the chemical attribute that most influenced the variation of bacterial communities in the WWTPs (λ = 0.14, p = 0.008). The OTUs affiliated to Syntrophus showed the highest response to the increase of total sulfur. All these findings can contribute to improve the understanding in relation to the sulfur-oxidizing and sulfate-reducing communities in WWTPs aiming to reduce H2S emissions.

  15. Linking river flow regimes to riparian plant guilds: a community-wide modeling approach.

    PubMed

    Lytle, David A; Merritt, David M; Tonkin, Jonathan D; Olden, Julian D; Reynolds, Lindsay V

    2017-03-06

    Modeling riparian plant dynamics along rivers is complicated by the fact that plants have different edaphic and hydrologic requirements at different life-stages. With intensifying human demands for water and continued human alteration of rivers, there is a growing need for predicting responses of vegetation to flow alteration, including responses related to climate change and river flow management. We developed a coupled structured population model that coombines stage-specific responses of plant guilds with specific attributes of river hydrologic regime. The model uses information on the vital rates of guilds as they relate to different hydrologic conditions (flood, drought, and baseflow), but deliberately omits biotic interactions from the structure ("interaction neutral"). Our intent was to: 1) consolidate key vital rates concerning plant population dynamics and to incorporate these data into a quantitative framework, 2) determine whether complex plant stand dynamics, including biotic interactions, can be predicted from basic vital rates and river hydrology, and 3) project how altered flow regimes might affect riparian communities. We illustrated the approach using five flow-response guilds that encompass much of the river floodplain community: hydroriparian tree, xeroriparian shrub, hydroriparian shrub, mesoriparian meadow, and desert shrub. We also developed novel network-based tools for predicting community-wide effects of climate-driven shifts and deliberately altered flow regimes. The model recovered known patterns of hydroriparian tree vs. xeroriparian shrub dominance, including the relative proportion of these two guilds as a function of river flow modification. By simulating flow alteration scenarios ranging from increased drought to shifts in flood timing, the model predicted that mature hydroriparian forest should be most abundant near the observed natural flow regime. Multiguild sensitivity analysis identified substantial network connectivity (many

  16. Mountain pastures of Qilian Shan: plant communities, grazing impact and degradation status (Gansu province, NW China)

    NASA Astrophysics Data System (ADS)

    Baranova, Alina; Schickhoff, Udo; Shunli, Wang; Ming, Jin

    2015-04-01

    Qilian Mountains are the water source region for the low arid reaches of HeiHe river basin (Gansu province, NW China). Due to overstocking and overgrazing during the last decades adverse ecological ef¬fects, in particular on soil properties and hydrological cycle, are to be expected in growing land areas. Vegetation cover is very important to prevent erosion process and to sustain stable subsurface runoff and ground water flow. The aim of this research is to identify plant communities, detecting grazing-induced and spatially differentiated changes in vegetation patterns, and to evaluate status of pasture land degradation.The study area is located in the spring/autumn pasture area of South Qilian Mountains between 2600-3600 m a.s.l., covering five main vegetation types: spruce forest, alpine shrubland, shrubby grassland, mountain grassland, degraded mountain grassland. In order to analyze gradual changes in vegetation patterns along altitudinal and grazing gradients and to classify related plant communities, quantitative and qualitative relevé data were collected (coverage, species composition, abundance of unpalatable plants, plant functional types, etc.). Vegetation was classified using hierarchical cluster analyses. Indirect Detrended Correspondence Analysis (DCA) was used to analyze variation in relationships between vegetation, environmental factors, and grazing impact. According to DCA results, distribution of the plant communities was strongly affected by altitude and exposition. Grassland floristic gradients showed greater dependence on grazing impact, which correlated contrarily with soil organic content, soil moisture and pH. Highest numbers of species richness and alpha diversity were detected in alpine shrubland vegetation type. Comparing the monitoring data for the recent nine years, a trend of deterioration, species successions and shift in dominant species becomes obvious. Species indicating degrading site environmental conditions were identified

  17. Neighbourhood association of Cortaderia selloana invasion, soil properties and plant community structure in Mediterranean coastal grasslands

    NASA Astrophysics Data System (ADS)

    Domènech, Roser; Vilà, Montserrat; Gesti, Josep; Serrasolses, Isabel

    2006-03-01

    Invasion by alien species is threatening the conservation of native plant communities and the integrity of ecosystems. To gain a better understanding of such impacts, many studies have examined the traits that make alien species successful invaders as well as the factors involved in community invasibility. However, it is necessary to link invader effects on community structure and on ecosystem processes in order to unravel the mechanisms of impact. Cortaderia selloana is a perennial grass native to South America that is invading abandoned agricultural lands close to coastal human settlements in Catalonia (NE Spain). In invaded pastures, we examined the association between C. selloana invasion, soil properties and vegetation structure changes in pastures, comparing the neighbourhood area of influence of C. selloana with areas far from C. selloana. Areas under the influence of C. selloana had lower total soil nitrogen values and higher C/N values than in areas far from C. selloana. Furthermore, the areas affected by C. selloana had lower species, family and life form richness and diversity, and less plant cover. In addition, C. selloana also increased the vertical vegetation structure and changed species composition (only 44% similarity between invaded and non-invaded areas). Our results point out that C. selloana has an effect on its neighbourhood leading to an increase in small-scale variability within invaded fields.

  18. 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

  19. Species Composition of Bacterial Communities Influences Attraction of Mosquitoes to Experimental Plant Infusions

    PubMed Central

    Ponnusamy, Loganathan; Wesson, Dawn M.; Arellano, Consuelo; Schal, Coby

    2013-01-01

    In the container habitats of immature mosquitoes, catabolism of plant matter and other organic detritus by microbial organisms produces metabolites that mediate the oviposition behavior of Aedes aegypti and Aedes albopictus. Public health agencies commonly use oviposition traps containing plant infusions for monitoring populations of these mosquito species, which are global vectors of dengue viruses. In laboratory experiments, gravid females exhibited significantly diminished responses to experimental infusions made with sterilized white oak leaves, showing that attractive odorants were produced through microbial metabolic activity. We evaluated effects of infusion concentration and fermentation time on attraction of gravid females to infusions made from senescent bamboo or white oak leaves. We used plate counts of heterotrophic bacteria, total counts of 4′,6-diamidino-2-phenylindole-stained bacterial cells, and 16S ribosomal DNA (rDNA) polymerase chain reaction–denaturing gradient gel electrophoresis (DGGE) to show that changes in the relative abundance of bacteria and the species composition of bacterial communities influenced attraction of gravid A. aegypti and A. albopictus mosquitoes to infusions. DGGE profiles showed that bacterial species composition in infusions changed over time. Principal components analysis indicated that oviposition responses to plant infusions were in general most affected by bacterial diversity and abundance. Analysis of bacterial 16S rDNA sequences derived from DGGE bands revealed that Proteo-bacteria (Alpha-, Beta-, Delta-, and Gamma-) were the predominant bacteria detected in both types of plant infusions. Gravid A. aegypti were significantly attracted to a mix of 14 bacterial species cultured from bamboo leaf infusion. The oviposition response of gravid mosquitoes to plant infusions is strongly influenced by abundance and diversity of bacterial species, which in turn is affected by plant species, leaf biomass, and fermentation

  20. Succession Stages of Tundra Plant Communities Following Wildfire Disturbance in Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Breen, A. L.; Hollingsworth, T. N.; Mack, M. C.; Jones, B. M.

    2015-12-01

    Rapid climate change is affecting climate-sensitive disturbance regimes throughout the world. In particular, the impacts of climate change on Arctic disturbance regimes are poorly understood because landscape-scale disturbances are infrequent or occur in remote localities. Wildfire in Arctic Alaska is presently limited by ignition source and favorable burn weather. With rapid climate change, a lengthening growing season, and subsequent increase in plant biomass and productivity, wildfire frequency and annual area burned in tundra ecosystems is expected to increase over the next century. Yet, post-fire tundra vegetation succession is inadequately characterized except at a few point locations. We identify succession stages of tussock tundra communities following wildfire using a chronosequence of 65 relevés in 10 tundra fire scars (1971-2011) and nearby unburned tundra from sites on the Seward Peninsula and northern foothills of the Brooks Range. We used the Braun-Blanquét approach to classify plant communities, and applied nonmetric multidimentional scaling (NMDS) to identify ecological gradients underlying community differentiation. The ordination revealed a clear differentiation between unburned and burned tundra communities. Ecological gradients, reflected by ordination axes, correspond to fire history (e.g., time since last fire, number of times burned, burn severity) and a complex productivity gradient. Post-fire species richness is less than unburned tundra; primarily reflected as a decrease in lichen species and turnover of bryophyte species immediately post-fire. Species richness of grasses increases post-fire and is greatest in communities that burned more than once in the past 30 years. Shrub cover and total aboveground biomass are greatest in repeat burn sites. We review and discuss our results focusing on the implications of a changing tundra fire regime, its effect on vegetation succession trajectories, and subsequent rates of carbon sequestration and

  1. Habitats as Complex Odour Environments: How Does Plant Diversity Affect Herbivore and Parasitoid Orientation?

    PubMed Central

    Wäschke, Nicole; Hardge, Kristin; Hancock, Christine; Hilker, Monika; Obermaier, Elisabeth; Meiners, Torsten

    2014-01-01

    Plant diversity is known to affect success of host location by pest insects, but its effect on olfactory orientation of non-pest insect species has hardly been addressed. First, we tested in laboratory experiments the hypothesis that non-host plants, which increase odour complexity in habitats, affect the host location ability of herbivores and parasitoids. Furthermore, we recorded field data of plant diversity in addition to herbivore and parasitoid abundance at 77 grassland sites in three different regions in Germany in order to elucidate whether our laboratory results reflect the field situation. As a model system we used the herb Plantago lanceolata, the herbivorous weevil Mecinus pascuorum, and its larval parasitoid Mesopolobus incultus. The laboratory bioassays revealed that both the herbivorous weevil and its larval parasitoid can locate their host plant and host via olfactory cues even in the presence of non-host odour. In a newly established two-circle olfactometer, the weeviĺs capability to detect host plant odour was not affected by odours from non-host plants. However, addition of non-host plant odours to host plant odour enhanced the weeviĺs foraging activity. The parasitoid was attracted by a combination of host plant and host volatiles in both the absence and presence of non-host plant volatiles in a Y-tube olfactometer. In dual choice tests the parasitoid preferred the blend of host plant and host volatiles over its combination with non-host plant volatiles. In the field, no indication was found that high plant diversity disturbs host (plant) location by the weevil and its parasitoid. In contrast, plant diversity was positively correlated with weevil abundance, whereas parasitoid abundance was independent of plant diversity. Therefore, we conclude that weevils and parasitoids showed the sensory capacity to successfully cope with complex vegetation odours when searching for hosts. PMID:24416354

  2. Exploring the Influence of Environmental Factors on Bacterial Communities within the Rhizosphere of the Cu-tolerant plant, Elsholtzia splendens

    NASA Astrophysics Data System (ADS)

    Jiang, Longfei; Song, Mengke; Yang, Li; Zhang, Dayi; Sun, Yingtao; Shen, Zhenguo; Luo, Chunling; Zhang, Gan

    2016-10-01

    Bacterial communities of rhizospheric soils play an important role in the tolerance and uptake of metal-tolerant/hyperaccumulating plants to metals, e.g. the Cu-tolerant Elsholtzia splendens native to China. In this work, pyrosequencing of the bacterial 16S rRNA gene was firstly applied to investigate the rhizospheric bacterial community of E. splendens grown at Cu contaminated sites. The 47 phyla including 11 dominant phyla (>1%) in E. splendens rhizosphere were presented. The effects of Cu and other environmental factors (total organic carbon, total nitrogen and pH) on the rhizospheric bacterial community were studied comprehensively. The phyla abundances were affected by the environmental factors to different extent, and we found pH, instead of Cu concentration, influenced UniFrac distance significantly and was identified as the most important environmental factor affecting bacterial community. In addition, the influence of environmental factors on gene profiles was explored according to the predicted metagenomes obtained by PICRUSt (phylogenetic investigation of communities by reconstruction of unobserved states). Our study illustrates a view about Cu-tolerant E. splendens rhizospheric bacterial communities (composition, diversity and gene profiles) and their influencing factors, giving a hand for the understanding on bacterial community is formed and affected in rhizosphere.

  3. Exploring the Influence of Environmental Factors on Bacterial Communities within the Rhizosphere of the Cu-tolerant plant, Elsholtzia splendens

    PubMed Central

    Jiang, Longfei; Song, Mengke; Yang, Li; Zhang, Dayi; Sun, Yingtao; Shen, Zhenguo; Luo, Chunling; Zhang, Gan

    2016-01-01

    Bacterial communities of rhizospheric soils play an important role in the tolerance and uptake of metal-tolerant/hyperaccumulating plants to metals, e.g. the Cu-tolerant Elsholtzia splendens native to China. In this work, pyrosequencing of the bacterial 16S rRNA gene was firstly applied to investigate the rhizospheric bacterial community of E. splendens grown at Cu contaminated sites. The 47 phyla including 11 dominant phyla (>1%) in E. splendens rhizosphere were presented. The effects of Cu and other environmental factors (total organic carbon, total nitrogen and pH) on the rhizospheric bacterial community were studied comprehensively. The phyla abundances were affected by the environmental factors to different extent, and we found pH, instead of Cu concentration, influenced UniFrac distance significantly and was identified as the most important environmental factor affecting bacterial community. In addition, the influence of environmental factors on gene profiles was explored according to the predicted metagenomes obtained by PICRUSt (phylogenetic investigation of communities by reconstruction of unobserved states). Our study illustrates a view about Cu-tolerant E. splendens rhizospheric bacterial communities (composition, diversity and gene profiles) and their influencing factors, giving a hand for the understanding on bacterial community is formed and affected in rhizosphere. PMID:27782202

  4. Land-use intensity and host plant identity interactively shape communities of arbuscular mycorrhizal fungi in roots of grassland plants.

    PubMed

    Vályi, Kriszta; Rillig, Matthias C; Hempel, Stefan

    2015-03-01

    We studied the effect of host plant identity and land-use intensity (LUI) on arbuscular mycorrhizal fungi (AMF, Glomeromycota) communities in roots of grassland plants. These are relevant factors for intraradical AMF communities in temperate grasslands, which are habitats where AMF are present in high abundance and diversity. In order to focus on fungi that directly interact with the plant at the time, we investigated root-colonizing communities. Our study sites represent an LUI gradient with different combinations of grazing, mowing, and fertilization. We used massively parallel multitag pyrosequencing to investigate AMF communities in a large number of root samples, while being able to track the identity of the host. We showed that host plants significantly differed in AMF community composition, while land use modified this effect in a plant species-specific manner. Communities in medium and low land-use sites were subsets of high land-use communities, suggesting a differential effect of land use on the dispersal of AMF species with different abundances and competitive abilities. We demonstrate that in these grasslands, there is a small group of highly abundant, generalist fungi which represent the dominating species in the AMF community.

  5. Role of invasive Melilotus officinalis in two native plant communities

    USGS Publications Warehouse

    Van Riper, Laura C.; Larson, Diane L.

    2009-01-01

    This study examines the impact of the exotic nitrogen-fixing legume Melilotus officinalis (L.) Lam. on native and exotic species cover in two Great Plains ecosystems in Badlands National Park, South Dakota. Melilotus is still widely planted and its effects on native ecosystems are not well studied. Melilotus could have direct effects on native plants, such as through competition or facilitation. Alternatively, Melilotus may have indirect effects on natives, e.g., by favoring exotic species which in turn have a negative effect on native species. This study examined these interactions across a 4-year period in two contrasting vegetation types: Badlands sparse vegetation and western wheatgrass (Pascopyrum smithii) mixed-grass prairie. Structural equation models were used to analyze the pathways through which Melilotus, native species, and other exotic species interact over a series of 2-year time steps. Melilotus can affect native and exotic species both in the current year and in the years after its death (a lag effect). A lag effect is possible because the death of a Melilotus plant can leave an open, potentially nitrogen-enriched site on the landscape. The results showed that the relationship between Melilotus and native and exotic species varied depending on the habitat and the year. In Badlands sparse vegetation, there was a consistent, strong, and positive relationship between Melilotus cover and native and exotic species cover suggesting that Melilotus is acting as a nurse plant and facilitating the growth of other species. In contrast, in western wheatgrass prairie, Melilotus was acting as a weak competitor and had no consistent effect on other species. In both habitats, there was little evidence for a direct lag effect of Melilotus on other species. Together, these results suggest both facilitative and competitive roles for Melilotus, depending on the vegetation type it invades.

  6. Linking geology and microbiology: inactive pockmarks affect sediment microbial community structure.

    PubMed

    Haverkamp, Thomas H A; Hammer, Øyvind; Jakobsen, Kjetill S

    2014-01-01

    Pockmarks are geological features that are found on the bottom of lakes and oceans all over the globe. Some are active, seeping oil or methane, while others are inactive. Active pockmarks are well studied since they harbor specialized microbial communities that proliferate on the seeping compounds. Such communities are not found in inactive pockmarks. Interestingly, inactive pockmarks are known to have different macrofaunal communities compared to the surrounding sediments. It is undetermined what the microbial composition of inactive pockmarks is and if it shows a similar pattern as the macrofauna. The Norwegian Oslofjord contains many inactive pockmarks and they are well suited to study the influence of these geological features on the microbial community in the sediment. Here we present a detailed analysis of the microbial communities found in three inactive pockmarks and two control samples at two core depth intervals. The communities were analyzed using high-throughput amplicon sequencing of the 16S rRNA V3 region. Microbial communities of surface pockmark sediments were indistinguishable from communities found in the surrounding seabed. In contrast, pockmark communities at 40 cm sediment depth had a significantly different community structure from normal sediments at the same depth. Statistical analysis of chemical variables indicated significant differences in the concentrations of total carbon and non-particulate organic carbon between 40 cm pockmarks and reference sample sediments. We discuss these results in comparison with the taxonomic classification of the OTUs identified in our samples. Our results indicate that microbial communities at the sediment surface are affected by the water column, while the deeper (40 cm) sediment communities are affected by local conditions within the sediment.

  7. Spatial heterogeneity of plant-soil feedback affects root interactions and interspecific competition.

    PubMed

    Hendriks, Marloes; Ravenek, Janneke M; Smit-Tiekstra, Annemiek E; van der Paauw, Jan Willem; de Caluwe, Hannie; van der Putten, Wim H; de Kroon, Hans; Mommer, Liesje

    2015-08-01

    Plant-soil feedback is receiving increasing interest as a factor influencing plant competition and species coexistence in grasslands. However, we do not know how spatial distribution of plant-soil feedback affects plant below-ground interactions. We investigated the way in which spatial heterogeneity of soil biota affects competitive interactions in grassland plant species. We performed a pairwise competition experiment combined with heterogeneous distribution of soil biota using four grassland plant species and their soil biota. Patches were applied as quadrants of 'own' and 'foreign' soils from all plant species in all pairwise combinations. To evaluate interspecific root responses, species-specific root biomass was quantified using real-time PCR. All plant species suffered negative soil feedback, but strength was species-specific, reflected by a decrease in root growth in own compared with foreign soil. Reduction in root growth in own patches by the superior plant competitor provided opportunities for inferior competitors to increase root biomass in these patches. These patterns did not cascade into above-ground effects during our experiment. We show that root distributions can be determined by spatial heterogeneity of soil biota, affecting plant below-ground competitive interactions. Thus, spatial heterogeneity of soil biota may contribute to plant species coexistence in species-rich grasslands.

  8. Natural and anthropogenic factors affecting the structure of the benthic macroinvertebrate community in an effluent-dominated reach of the Santa Cruz River, AZ

    USGS Publications Warehouse

    Boyle, T.P.; Fraleigh, H.D.

    2003-01-01

    This study provides an assessment of the ecological conditions of a 46-km effluent-dominated stream section of the Santa Cruz River in the vicinity of the International Waste Water Treatment Plant, Nogales, AZ. We associated changes in the structure of the macroinvertebrate community to natural and anthropogenic chemical and physical variables using multivariate analysis. The analysis shows that biological criteria for effluent-dominated streams can be established using macroinvertebrate community attributes only with an understanding of the contribution of three classes of variables on the community structure: (1) low flow hydrological discharge as affected by groundwater withdrawals, treatment plant discharge, and subsurface geomorphology; (2) chemical composition of the treatment plant discharge and natural dilution; and (3) naturally produced floods resulting from seasonality of precipitation. ?? 2003 Elsevier Science Ltd. All rights reserved.

  9. Functional Richness and Identity Do Not Strongly Affect Invasibility of Constructed Dune Communities.

    PubMed

    Mason, Tanya J; French, Kristine; Jolley, Dianne F

    2017-01-01

    Biotic effects are often used to explain community structure and invasion resistance. We evaluated the contribution of functional richness and identity to invasion resistance and abiotic resource availability using a mesocosm experiment. We predicted that higher functional richness would confer greater invasion resistance through greater resource sequestration. We also predicted that niche pre-emption and invasion resistance would be higher in communities which included functional groups similar to the invader than communities where all functional groups were distinct from the invader. We constructed communities of different functional richness and identity but maintained constant species richness and numbers of individuals in the resident community. The constructed communities represented potential fore dune conditions following invader control activities along the Australian east coast. We then simulated an invasion event by bitou (Chrysanthemoides monilifera ssp. rotundata DC. Norl.), a South African shrub invader. We used the same bitou propagule pressure across all treatments and monitored invasion success and resource availability for 13 months. Contrary to our predictions, we found that functional richness did not mediate the number of bitou individuals or bitou cover and functional identity had little effect on invasion success: there was a trend for the grass single functional group treatment to supress bitou individuals, but this trend was obscured when grasses were in multi functional group treatments. We found that all constructed communities facilitated bitou establishment and suppressed bitou cover relative to unplanted mesocosms. Abiotic resource use was either similar among planted communities, or differences did not relate to invasion success (with the exception of light availability). We attribute invasion resistance to bulk plant biomass across planted treatments rather than their functional group arrangement.

  10. Functional Richness and Identity Do Not Strongly Affect Invasibility of Constructed Dune Communities

    PubMed Central

    Mason, Tanya J.; French, Kristine; Jolley, Dianne F.

    2017-01-01

    Biotic effects are often used to explain community structure and invasion resistance. We evaluated the contribution of functional richness and identity to invasion resistance and abiotic resource availability using a mesocosm experiment. We predicted that higher functional richness would confer greater invasion resistance through greater resource sequestration. We also predicted that niche pre-emption and invasion resistance would be higher in communities which included functional groups similar to the invader than communities where all functional groups were distinct from the invader. We constructed communities of different functional richness and identity but maintained constant species richness and numbers of individuals in the resident community. The constructed communities represented potential fore dune conditions following invader control activities along the Australian east coast. We then simulated an invasion event by bitou (Chrysanthemoides monilifera ssp. rotundata DC. Norl.), a South African shrub invader. We used the same bitou propagule pressure across all treatments and monitored invasion success and resource availability for 13 months. Contrary to our predictions, we found that functional richness did not mediate the number of bitou individuals or bitou cover and functional identity had little effect on invasion success: there was a trend for the grass single functional group treatment to supress bitou individuals, but this trend was obscured when grasses were in multi functional group treatments. We found that all constructed communities facilitated bitou establishment and suppressed bitou cover relative to unplanted mesocosms. Abiotic resource use was either similar among planted communities, or differences did not relate to invasion success (with the exception of light availability). We attribute invasion resistance to bulk plant biomass across planted treatments rather than their functional group arrangement. PMID:28072854

  11. Soil phosphorus depletion and shifts in plant communities change bacterial community structure in a long-term grassland management trial.

    PubMed

    Adair, Karen L; Wratten, Steve; Lear, Gavin

    2013-06-01

    Agricultural systems rely on healthy soils and their sustainability requires understanding the long-term impacts of agricultural practices on soils, including microbial communities. We examined the impact of 17 years of land management on soil bacterial communities in a New Zealand randomized-block pasture trial. Significant variation in bacterial community structure related to mowing and plant biomass removal, while nitrogen fertilizer had no effect. Changes in soil chemistry and legume abundance described 52% of the observed variation in the bacterial community structure. Legumes (Trifolium species) were absent in unmanaged plots but increased in abundance with management intensity; 11% of the variation in soil bacterial community structure was attributed to this shift in the plant community. Olsen P explained 10% of the observed heterogeneity, which is likely due to persistent biomass removal resulting in P limitation; Olsen P was significantly lower in plots with biomass removed (14 mg kg(-1) ± 1.3SE) compared with plots that were not mown, or where biomass was left after mowing (32 mg kg(-1) ± 1.6SE). Our results suggest that removal of plant biomass and associated phosphorus, as well as shifts in the plant community, have greater long-term impacts on soil bacterial community structure than application of nitrogen fertilizers.

  12. Quantitative Analysis of Plant Consumption and Preference by Oedaleus asiaticus (Acrididae: Oedipodinae) in Changed Plant Communities Consisting of Three Grass Species.

    PubMed

    Huang, X; McNeill, M; Zhang, Z

    2016-02-01

    We used Oedaleus asiaticus Bey-Bienko (Acrididae: Oedipodinae) as a model species to examine how plant community composition influenced grasshopper population densities and feeding habits. Our results show that in the Xinli Gol Grassland ecosystem, both plant community composition and grasshopper density vary considerably over fairly small distances, and that O. asiaticus density was directly related to the proportional abundance of specific plant species. A 60-d field-cage study showed that O. asiaticus food preference and consumption differed when the ratios of three dominant grass species (Leymus chinensis (Trin.) Tzvel, Stipa krylovii Roshev, and Cleistogenes squarrosa (Trin.) Keng) differed. The consumption of both S. krylovii and C. squarrosa increased with a corresponding increase in their respective biomass availability. Although O. asiaticus preferred S. krylovii and ate only small amounts of L. chinensis, a specific amount of L. chinensis was always consumed. Feeding of these three plant species could be divided into three levels based on diet selectivity index (SI), with O. asiaticus showing a strong preference for S. krylovii (SI > 1), over that for C. squarrosa (0.5 < SI ≤ 1), and a low acceptance for L. chinensis (0 < SI ≤ 0.5). Plant consumption and preference by O. asiaticus was in decreasing order S. krylovii>C. squarrosa>L. chinensis. This study shows that small-scale changes in plant community composition can have large affects on grasshopper diets and populations. As such, this study is useful for developing guidelines for the monitoring of O. asiaticus impacts against the background of vegetation succession and changing plant communities in response to grazing or human activities.

  13. Filtration properties of activated sludge in municipal MBR wastewater treatment plants are related to microbial community structure.

    PubMed

    Bugge, Thomas V; Larsen, Poul; Saunders, Aaron M; Kragelund, Caroline; Wybrandt, Lisbeth; Keiding, Kristian; Christensen, Morten L; Nielsen, Per H

    2013-11-01

    In the conventional activated sludge process, a number of important parameters determining the efficiency of settling and dewatering are often linked to specific groups of bacteria in the sludge--namely floc size, residual turbidity, shear sensitivity and composition of extracellular polymeric substances (EPS). In membrane bioreactors (MBRs) the nature of solids separation at the membrane has much in common with sludge dewaterability but less is known about the effect of specific microbial groups on the sludge characteristics that affect this process. In this study, six full-scale MBR plants were investigated to identify correlations between sludge filterability, sludge characteristics, and microbial community structure. The microbial community structure was described by quantitative fluorescence in situ hybridization and sludge filterability by a low-pressure filtration method. A strong correlation between the degree of flocculation (ratio between floc size and residual turbidity) and sludge filterability at low pressure was found. A good balance between EPS and cations in the sludge correlated with good flocculation, relatively large sludge flocs, and low amounts of small particles and single cells in the bulk phase (measured as residual turbidity), all leading to a good filterability. Floc properties could also be linked to the microbial community structure. Bacterial species forming strong microcolonies such as Nitrospira and Accumulibacter were present in plants with good flocculation and filtration properties, while few strong microcolonies and many filamentous bacteria in the plants correlated with poor flocculation and filtration problems. In conclusion this study extends the hitherto accepted perception that plant operation affects floc properties which affects fouling. Additionally, plant operation also affects species composition, which affects floc properties and in the end fouling propensity.

  14. Allocation, stress tolerance and carbon transport in plants: how does phloem physiology affect plant ecology?

    PubMed

    Savage, Jessica A; Clearwater, Michael J; Haines, Dustin F; Klein, Tamir; Mencuccini, Maurizio; Sevanto, Sanna; Turgeon, Robert; Zhang, Cankui

    2016-04-01

    Despite the crucial role of carbon transport in whole plant physiology and its impact on plant-environment interactions and ecosystem function, relatively little research has tried to examine how phloem physiology impacts plant ecology. In this review, we highlight several areas of active research where inquiry into phloem physiology has increased our understanding of whole plant function and ecological processes. We consider how xylem-phloem interactions impact plant drought tolerance and reproduction, how phloem transport influences carbon allocation in trees and carbon cycling in ecosystems and how phloem function mediates plant relations with insects, pests, microbes and symbiotes. We argue that in spite of challenges that exist in studying phloem physiology, it is critical that we consider the role of this dynamic vascular system when examining the relationship between plants and their biotic and abiotic environment.

  15. Eco-geophysical imaging of watershed-scale soil patterns links with plant community spatial patterns

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The extent to which soil resource availability, nutrients or 1 moisture, control the structure, function and diversity of plant communities has aroused considerable interest in the past decade, and remains topical in light of global change. Numerous plant communities are controlled either by water o...

  16. A Post Licensing Study of Community Effects at Two Operating Nuclear Power Plants. Final Report.

    ERIC Educational Resources Information Center

    Purdy, Bruce J.; And Others

    In an effort to identify and assess the social, economic, and political effects of nuclear power plant construction and operation upon two host communities (Plymouth, Massachusetts and Waterford, Connecticut), a post-licensing review revealed that the primary impact of the nuclear power plants in both communities was an increase in the property…

  17. Investigating the Effect of Livestock Grazing and Associated Plant Community Shifts on Carbon and Nutrient Cycling in Alberta, Canada

    NASA Astrophysics Data System (ADS)

    Hewins, D. B.; Chuan, S.; Stolnikova, E.; Bork, E. W.; Carlyle, C. N.; Chang, S. X.

    2015-12-01

    Grassland ecosystems are ubiquitous across the globe covering an estimated 40 % of Earth's terrestrial landmass. These ecosystems are widely valued for providing forage for domestic livestock and a suite of important ecosystem goods and services including carbon (C) storage. Despite storing more than 30 % of soil C globally, the effect of both livestock grazing and the associated change in plant community structure in response to grazing on C and nutrient cycling remains uncertain. To gain a quantitative understanding of the direct and indirect effects of livestock grazing on C and nutrient cycling, we established study sites at 15 existing site localities with paired long-term grazing (ca. 30 y) and non-grazed treatments (totaling 30 unique plant communities). Our sites were distributed widely across Alberta in three distinct grassland bioclimatic zones allowing us to make comparisons across the broad range of climate variability typical of western Canadian grasslands. In each plant community we decomposed 5 common plant species that are known to increase or decrease in response to grazing pressure, a unique plant community sample, and a cellulose paper control. We measured mass loss, initial lignin, C and N concentrations at 0, 1, 3, 6 and 12 months of field incubation. In addition we assayed hydrolytic and oxidative extracellular enzymes associated with for C (n= 5 hydrolytic; phenoloxidase and peroxidase) and nutrients (i.e. N and P; n=1 ea.) cycling from each litter sample at each collection. Our results suggest that by changing the plant community structure, grazing can affect rates of decomposition and associated biogeochemical cycling by changing plant species and associated litter inputs. Moreover, measures of microbial function are controlled by site-specific conditions (e.g. temperature and precipitation), litter chemistry over the course of our incubation.

  18. Dissipation and effects of tricyclazole on soil microbial communities and rice growth as affected by amendment with alperujo compost.

    PubMed

    García-Jaramillo, M; Redondo-Gómez, S; Barcia-Piedras, J M; Aguilar, M; Jurado, V; Hermosín, M C; Cox, L

    2016-04-15

    The presence of pesticides in surface and groundwater has grown considerably in the last decades as a consequence of the intensive farming activity. Several studies have shown the benefits of using organic amendments to prevent losses of pesticides from runoff or leaching. A particular soil from the Guadalquivir valley was placed in open air ponds and amended at 1 or 2% (w/w) with alperujo compost (AC), a byproduct from the olive oil industry. Tricyclazole dissipation, rice growth and microbial diversity were monitored along an entire rice growing season. An increase in the net photosynthetic rate of Oryza sativa plants grown in the ponds with AC was observed. These plants produced between 1100 and 1300kgha(-1) more rice than plants from the unamended ponds. No significant differences were observed in tricyclazole dissipation, monitored for a month in soil, surface and drainage water, between the amended and unamended ponds. The structure and diversity of bacteria and fungi communities were also studied by the use of the polymerase chain reaction denaturing gel electrophoresis (PCR-DGGE) from DNA extracted directly from soil samples. The banding pattern was similar for all treatments, although the density of bands varied throughout the time. Apparently, tricyclazole did not affect the structure and diversity of bacteria and fungi communities, and this was attributed to its low bioavailability. Rice cultivation under paddy field conditions may be more efficient under the effects of this compost, due to its positive effects on soil properties, rice yield, and soil microbial diversity.

  19. Links between plant and fungal communities across a deforestation chronosequence in the Amazon rainforest

    PubMed Central

    Mueller, Rebecca C; Paula, Fabiana S; Mirza, Babur S; Rodrigues, Jorge LM; Nüsslein, Klaus; Bohannan, Brendan JM

    2014-01-01

    Understanding the interactions among microbial communities, plant communities and soil properties following deforestation could provide insights into the long-term effects of land-use change on ecosystem functions, and may help identify approaches that promote the recovery of degraded sites. We combined high-throughput sequencing of fungal rDNA and molecular barcoding of plant roots to estimate fungal and plant community composition in soil sampled across a chronosequence of deforestation. We found significant effects of land-use change on fungal community composition, which was more closely correlated to plant community composition than to changes in soil properties or geographic distance, providing evidence for strong links between above- and below-ground communities in tropical forests. PMID:24451208

  20. Links between plant and fungal communities across a deforestation chronosequence in the Amazon rainforest.

    PubMed

    Mueller, Rebecca C; Paula, Fabiana S; Mirza, Babur S; Rodrigues, Jorge L M; Nüsslein, Klaus; Bohannan, Brendan J M

    2014-07-01

    Understanding the interactions among microbial communities, plant communities and soil properties following deforestation could provide insights into the long-term effects of land-use change on ecosystem functions, and may help identify approaches that promote the recovery of degraded sites. We combined high-throughput sequencing of fungal rDNA and molecular barcoding of plant roots to estimate fungal and plant community composition in soil sampled across a chronosequence of deforestation. We found significant effects of land-use change on fungal community composition, which was more closely correlated to plant community composition than to changes in soil properties or geographic distance, providing evidence for strong links between above- and below-ground communities in tropical forests.

  1. Developing restoration planting mixes for active ski slopes: a multi-site reference community approach.

    PubMed

    Burt, Jennifer Williamson

    2012-03-01

    Downhill ski areas occupy large expanses of mountainous lands where restoration of ecosystem function is of increasing importance and interest. Establishing diverse native plant communities on ski runs should enhance sediment and water retention, wildlife habitat, biodiversity and aesthetics. Because ski slopes are managed for recreation, ski slope revegetation mixes must consist of low-stature or herbaceous plants that can tolerate typical environmental conditions on ski slopes (high elevation, disturbed soils, open, steep slopes). The most appropriate reference communities for selecting ski slope revegetation species are thus successional, or seral plant communities in similar environments (i.e., other ski slopes). Using results from a broad-scale reference community analysis, I evaluated plant communities naturally occurring on ski slopes from 21 active and abandoned ski areas throughout the northern Sierra Nevada to identify native plant species suitable for use in ski slope restoration. I constructed a baseline planting palette of regionally appropriate plant species (for restoration of either newly created or already existing ski runs) that is functionally diverse and is likely to succeed across a broad range of environments. I also identify a more comprehensive list of species for more specialized planting mixes based on site-specific goals and particular environmental settings. Establishing seral plant communities may be an appropriate restoration goal for many other types of managed lands, including roadsides, firebreaks and utility rights-of-way. This study describes an ecological (and potentially cost-effective) approach to developing restoration planting palettes for such managed lands.

  2. Developing Restoration Planting Mixes for Active Ski Slopes: A Multi-Site Reference Community Approach

    NASA Astrophysics Data System (ADS)

    Burt, Jennifer Williamson

    2012-03-01

    Downhill ski areas occupy large expanses of mountainous lands where restoration of ecosystem function is of increasing importance and interest. Establishing diverse native plant communities on ski runs should enhance sediment and water retention, wildlife habitat, biodiversity and aesthetics. Because ski slopes are managed for recreation, ski slope revegetation mixes must consist of low-stature or herbaceous plants that can tolerate typical environmental conditions on ski slopes (high elevation, disturbed soils, open, steep slopes). The most appropriate reference communities for selecting ski slope revegetation species are thus successional, or seral plant communities in similar environments (i.e., other ski slopes). Using results from a broad-scale reference community analysis, I evaluated plant communities naturally occurring on ski slopes from 21 active and abandoned ski areas throughout the northern Sierra Nevada to identify native plant species suitable for use in ski slope restoration. I constructed a baseline planting palette of regionally appropriate plant species (for restoration of either newly created or already existing ski runs) that is functionally diverse and is likely to succeed across a broad range of environments. I also identify a more comprehensive list of species for more specialized planting mixes based on site-specific goals and particular environmental settings. Establishing seral plant communities may be an appropriate restoration goal for many other types of managed lands, including roadsides, firebreaks and utility rights-of-way. This study describes an ecological (and potentially cost-effective) approach to developing restoration planting palettes for such managed lands.

  3. Fusion and metabolism of plant cells as affected by microgravity.

    PubMed

    Hampp, R; Hoffmann, E; Schönherr, K; Johann, P; De Filippis, L

    1997-01-01

    Plant cell protoplasts derived from leaf tissue of two different tobacco species (Nicotiana tabacum., N. rustica L.) were exposed to short-term (sounding rocket experiments) and long-term (spacelab) microgravity environments in order to study both (electro) cell fusion and cell metabolism during early and later stages of tissue regeneration. The period of exposure to microgravity varied from 10 min (sounding rocket) to 10 d (space shuttle). The process of electro fusion of protoplasts was improved under conditions of microgravity: the time needed to establish close membrane contact between protoplasts (alignment time) was reduced (5 as compared to 15 s under 1 g) and numbers of fusion products between protoplasts of different specific density were increased by a factor of about 10. In addition, viability of fusion products, as shown by the ability to form callus, increased from about 60% to more than 90%. Regenerated fusion products obtained from both sounding-rocket and spacelab experiments showed a wide range of intermediate properties between the two parental plants. This was verified by isozyme analysis and random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). In order to address potential metabolic responses, more general markers such as the overall energy state (ATP/ADP ratio), the redox charge of the diphosphopyridine nucleotide system (NADH/NAD ratio), and the pool size of fructose-2,6-bisphosphate (Fru 2,6 bisp), a regulator of the balance between glycolysis and gluconeogenesis, were determined. Responses of these parameters were different with regard to short-term and long-term exposure. Shortly after transition to reduced gravitation (sounding rocket) ratios of ATP/ADP exhibited strong fluctuation while the pool size of NAD decreased (indicating an increased NADH/NAD ratio) and that of Fru 2,6 bisp increased. As similar changes can be observed under stress conditions, this response is probably indicative of a metabolic stress

  4. RESEARCH: Plant Community Structure in Relation to Long-Term Disturbance by Mechanized Military Maneuvers in a Semiarid Region.

    PubMed

    Milchunas; Schulz; Shaw

    2000-05-01

    / Mechanized military maneuvers are an intensive form of disturbance to plant communities in large areas throughout the world. Tracking by heavy vehicles can cause direct mortality and indirectly affect plant communities through soil compaction and by altering competitive relationships. We assessed the long-term condition of structural attributes of open woodland, grassland, and shrubland communities at Fort Carson, Colorado, in relation to levels of disturbance and soil texture. Covariate analyses were used to help separate the directional forcings by the chronic disturbance from the regenerative capacities in order to assess the relative resistance and resilience of the communities and to determine whether the continual disturbance-recovery processes balanced under current levels of utilization. All three communities responded differently to disturbance. In open woodlands, altered understory/overstory relationships were suggested by increased grass, forb, shrub, and total vegetation cover and smaller decreases in shorter than taller woody species with increasing levels of disturbance. Grassland communities generally displayed greater responses to disturbance than other communities, but temporal dynamics were often similar, indicating relatively less resistance but greater resilience of this community. Weed and exotic species increased both temporally and in relation to levels of disturbance in all three community types. Temporal trends in community-level indices of dissimilarity and diversity also indicate that rates of disturbance were greater than rates of recovery. Few variables were related to within-community differences in soil texture. While total aerial cover was temporally stable, changes in species composition and in basal cover in grasslands and shrublands suggest increasing erosion potential.

  5. Halophyte plant colonization as a driver of the composition of bacterial communities in salt marshes chronically exposed to oil hydrocarbons.

    PubMed

    Oliveira, Vanessa; Gomes, Newton C M; Cleary, Daniel F R; Almeida, Adelaide; Silva, Artur M S; Simões, Mário M Q; Silva, Helena; Cunha, Ângela

    2014-12-01

    In this study, two molecular techniques [denaturing gradient gel electrophoresis (DGGE) and barcoded pyrosequencing] were used to evaluate the composition of bacterial communities in salt marsh microhabitats [bulk sediment and sediment surrounding the roots (rhizosphere) of Halimione portulacoides and Sarcocornia perennis ssp. perennis] that have been differentially affected by oil hydrocarbon (OH) pollution. Both DGGE and pyrosequencing revealed that bacterial composition is structured by microhabitat. Rhizosphere sediment from both plant species revealed enrichment of operational taxonomic units closely related to Acidimicrobiales, Myxococcales and Sphingomonadales. The in silico metagenome analyses suggest that homologous genes related to OH degradation appeared to be more frequent in both plant rhizospheres than in bulk sediment. In summary, this study suggests that halophyte plant colonization is an important driver of hydrocarbonoclastic bacterial community composition in estuarine environments, which can be exploited for in situ phytoremediation of OH in salt marsh environments.

  6. Understand the air-pollution laws that affect CPI plants

    SciTech Connect

    Not Available

    1992-04-01

    The Clean Air Act Amendments of 1990 promise to further refine and strengthen air-pollution control. The resulting Clean Air Act has a more direct and pervasive impact on our everyday lives than any other environmental law. The Act: establishes health-based air-quality standards; provides for the preparation, approval, and enforcement of state implementation plans to meet the air-quality standards; and provides for the control of new emissions that have the potential to endanger public health. It also provides for the control of new sources of emissions of hazardous air pollutants, for the prevention of significant deterioration of clean air areas, for the reduction of emissions from automobile and other mobile sources, and for the control of acid ran. Finally, the Act provides for permit programs and civil and criminal enforcement. Compliance with the Clean Air Act and the regulations and standards established under it must be integrated into the design and operation of every chemical process industries (CPI) plant. This article provides a brief overview of the Clean Air Act's various air-quality programs.

  7. Reassessment of selected factors affecting siting of Nuclear Power Plants

    SciTech Connect

    Davis, R.E.; Hanson, A.L.; Mubayi, V.; Nourbakhsh, H.P.

    1997-02-01

    Brookhaven National Laboratory has performed a series of probabilistic consequence assessment calculations for nuclear reactor siting. This study takes into account recent insights into severe accident source terms and examines consequences in a risk based format consistent with the quantitative health objectives (QHOs) of the NRC`s Safety Goal Policy. Simplified severe accident source terms developed in this study are based on the risk insights of NUREG-1150. The results of the study indicate that both the quantity of radioactivity released in a severe accident as well as the likelihood of a release are lower than those predicted in earlier studies. The accident risks using the simplified source terms are examined at a series of generic plant sites, that vary in population distribution, meteorological conditions, and exclusion area boundary distances. Sensitivity calculations are performed to evaluate the effects of emergency protective action assumptions on the risk of prompt fatality and latent cancers fatality, and population relocation. The study finds that based on the new source terms the prompt and latent fatality risks at all generic sites meet the QHOs of the NRC`s Safety Goal Policy by margins ranging from one to more than three orders of magnitude. 4 refs., 17 figs., 24 tabs.

  8. Plant community structure in an oligohaline tidal marsh

    USGS Publications Warehouse

    Brewer, J.S.; Grace, J.B.

    1990-01-01

    An oligohaline tidal marsh on the northern shore of Lake Pontchartrain, LA was characterized with respect to the distributions and abundances of plant species over spatial and temporal gradients using Detrended Correspondence Analysis (DCA). In addition, the species distributions were correlated to several physical environmental factors using Detrended Canonical Correspondence Analysis (DCCA). The distributions of species were best correlated with distance from Lake Pontchartrain, and to a lesser extent with elevation and substrate organic matter. They were least correlated with mean soil salinity (referred to here as background salinity). Of the three mid-seasonal dominant species, the perennial grass, Spartina patens, is the most salt tolerant and was found closest to the lake. Further inland the dominant perennial was Sagittaria lancifolia, which has a salt tolerance less than that of Spartina patens. The perennial sedge, Cladium jamaicense, which is the least salt tolerant of the three, was dominant furthest inland. Background salinity levels were generally low (<5 ppt.) and did not explain species distributions. We hypothesize that the distribution of species is regulated by occasional storm-generated salt pulses that generate strong, short-lived salinity gradients as a function of distance from the lake. Biotic interactions likely also play a role in structuring the plant community. The distributions of several annuals depended on the size and life history of the mid-seasonal dominant perennials. Most of the annuals frequently co-occurred with Sagittaria lancifolia, which was the shortest in stature and had the least persistent canopy of the three mid-seasonal dominant perennials.

  9. Biological support media influence the bacterial biofouling community in reverse osmosis water reclamation demonstration plants.

    PubMed

    Ferrera, Isabel; Mas, Jordi; Taberna, Elisenda; Sanz, Joan; Sánchez, Olga

    2015-01-01

    The diversity of the bacterial community developed in different stages of two reverse osmosis (RO) water reclamation demonstration plants designed in a wastewater treatment plant (WWTP) in Tarragona (Spain) was characterized by applying 454-pyrosequencing of the 16S rRNA gene. The plants were fed by secondary treated effluent to a conventional pretreatment train prior to the two-pass RO system. Plants differed in the material used in the filtration process, which was sand in one demonstration plant and Scandinavian schists in the second plant. The results showed the presence of a highly diverse and complex community in the biofilms, mainly composed of members of the Betaproteobacteria and Bacteroidetes in all stages, with the presence of some typical wastewater bacteria, suggesting a feed water origin. Community similarities analyses revealed that samples clustered according to filter type, highlighting the critical influence of the biological supporting medium in biofilm community structure.

  10. The role of volatile metabolites in microbial communities of the lSS higher plant link

    NASA Astrophysics Data System (ADS)

    Tirranen, L. S.; Gitelson, I. I.

    The possibility of controlling the microbial community composition through metabolites produced by microbes has been considered. Basing on the comparative analysis of the experimental data we have revealed the greater contribution of volatile metabolites to microbial interaction than non-volatile. Investigations proved that the interaction between microorganisms through extracted volatile materials is a widespread phenomenon peculiar to many microorganisms. Most cultures inhibited each other's growth, in a number of cases displayed bactericidal action. Stimulatory action occurred 6 - 8 times rarely. The individuality of affect on studied test-cultures growth and the spectrum of microbial resistance to volatile metabolites have been revealed. Based on the comparative cluster analysis of these spectra from 100 studied cultures we have revealed that studied organisms produce a complex of volatile metabolites including 82 inhibiting and 52 stimulating. It was found that excretion of volatile metabolites of studied microorganisms depended upon the culture age, concentration of nutrient medium separate components and volatile by-products excreted by other microorganisms. The production can be increased or decreased by volatile by-products of other microbes. This is related to strain features and the culture age. The prospects of using these regulating metabolites can be defined by the "range", specificity and safety for other members of the microbial community in insufficient concentrations. Volatile metabolites of either plants and microorganisms or other system links - humans and technological equipment installed inside the closed ecosystem - can influence the formation of microbial communities, gas composition of the system atmosphere and state of the plants through the atmosphere. Special experiments showed that volatile microorganism metabolites could accumulate in the environment, dissolve in atmospheric water and maintain their biological activity for many days

  11. Endangered light-footed clapper rail affects parasite community structure in coastal wetlands.

    PubMed

    Whitney, Kathleen L; Hechinger, Ryan F; Kuris, Armand M; Lafferty, Kevin D

    2007-09-01

    An extinction necessarily affects community members that have obligate relationships with the extinct species. Indirect or cascading effects can lead to even broader changes at the community or ecosystem level. However, it is not clear whether generalist parasites should be affected by the extinction of one of their hosts. We tested the prediction that loss of a host species could affect the structure of a generalist parasite community by investigating the role of endangered Light-footed Clapper Rails (Rallus longirostris levipes) in structuring trematode communities in four tidal wetlands in southern California, U.S.A. (Carpinteria Salt Marsh, Mugu Lagoon) and Mexico (Estero de Punta Banda, Bahia Falsa-San Quintin). We used larval trematode parasites in first intermediate host snails (Cerithidea californica) as windows into the adult trematodes that parasitize Clapper Rails. Within and among wetlands, we found positive associations between Clapper Rails and four trematode species, particularly in the vegetated marsh habitat where Clapper Rails typically occur. This suggests that further loss of Clapper Rails is likely to affect the abundance of several competitively dominant trematode species in wetlands with California horn snails, with possible indirect effects on the trematode community and changes in the impacts of these parasites on fishes and invertebrates.

  12. Psychological Impact of a Nuclear Power Plant: Changing Perceptions of Community and Neighborhood.

    ERIC Educational Resources Information Center

    Hughey, Joseph B.

    1986-01-01

    Examines change in attitude toward community and descriptions of neighborhood environments of 217 residents of rural host community for a nuclear power plant. Finds negative attitude change and less positive descriptions of neighborhoods. Discusses implications for community psychology and preventive intervention. (LFL)

  13. Life Form and Life History Explain Variation in Population Processes in a Grassland Community Invaded by Exotic Plants and Mammals

    PubMed Central

    Nelis, Lisa Castillo

    2012-01-01

    The existence of general characteristics of plant invasiveness is still debated. One reason we may not have found these characteristics is because we do not yet understand how processes underlying population dynamics contribute to community composition in invaded communities. Here I modify Ricker stock-recruitment models to parameterize processes important to community dynamics in an invaded grassland community: immigration, maximum intrinsic growth rate, self-regulation, and limitation by other species. I then used the parameterized models in a multi-species stochastic simulation to determine how processes affected long-term community dynamics. By parameterizing the models using the frequency of the 18 most common species in the grassland, I determined that life history and life form are stronger predictors of underlying processes than is native status. Immigration maintains exotic annual grasses and the dominant native perennial grass in the community. Growth rate maintains other perennial species. While the model mirrors the frequency of native species well, exotic species have lower observed than parameterized frequencies, suggesting that they are not reaching their potential frequency. These results, combined with results from past research, suggest that disturbance may be key to maintaining exotic species in the community. Here I showed that a continuous modified Ricker model fit discrete grassland frequency data well. This allowed me to model the dominant species in the community simultaneously and gain insight into the processes that determine community composition. PMID:22916178

  14. Effects of plant biomass, plant diversity, and water content on bacterial communities in soil lysimeters: implications for the determinants of bacterial diversity.

    PubMed

    Zul, Delita; Denzel, Sabine; Kotz, Andrea; Overmann, Jörg

    2007-11-01

    Soils may comprise tens of thousands to millions of bacterial species. It is still unclear whether this high level of diversity is governed by functional redundancy or by a multitude of ecological niches. In order to address this question, we analyzed the reproducibility of bacterial community composition after different experimental manipulations. Soil lysimeters were planted with four different types of plant communities, and the water content was adjusted. Group-specific phylogenetic fingerprinting by PCR-denaturing gradient gel electrophoresis revealed clear differences in the composition of Alphaproteobacteria, Betaproteobacteria, Bacteroidetes, Chloroflexi, Planctomycetes, and Verrucomicrobia populations in soils without plants compared to that of populations in planted soils, whereas no influence of plant species composition on bacterial diversity could be discerned. These results indicate that the presence of higher plant species affects the species composition of bacterial groups in a reproducible manner and even outside of the rhizosphere. In contrast, the environmental factors tested did not affect the composition of Acidobacteria, Actinobacteria, Archaea, and Firmicutes populations. One-third (52 out of 160) of the sequence types were found to be specifically and reproducibly associated with the absence or presence of plants. Unexpectedly, this was also true for numerous minor constituents of the soil bacterial assemblage. Subsequently, one of the low-abundance phylotypes (beta10) was selected for studying the interdependence under particular experimental conditions and the underlying causes in more detail. This so-far-uncultured phylotype of the Betaproteobacteria species represented up to 0.18% of all bacterial cells in planted lysimeters compared to 0.017% in unplanted systems. A cultured representative of this phylotype exhibited high physiological flexibility and was capable of utilizing major constituents of root exudates. Our results suggest that

  15. Effects of invasive species on plant communities: an example using submersed aquatic plants at the regional level

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Submerged aquatic plants have a key role in maintaining functioning aquatic ecosystems through their effects in the hydrological regime, sedimentation, nutrient cycling and habitats of associated fauna. Modifications of aquatic plant communities, as for example through the introduction of invasive s...

  16. Habitat Heterogeneity Affects Plant and Arthropod Species Diversity and Turnover in Traditional Cornfields.

    PubMed

    Martínez, Eliana; Rös, Matthias; Bonilla, María Argenis; Dirzo, Rodolfo

    2015-01-01

    The expansion of the agricultural frontier by the clearing of remnant forests has led to human-dominated landscape mosaics. Previous studies have evaluated the effect of these landscape mosaics on arthropod diversity at local spatial scales in temperate and tropical regions, but little is known about fragmentation effects in crop systems, such as the complex tropical traditional crop systems that maintain a high diversity of weeds and arthropods in low-Andean regions. To understand the factors that influence patterns of diversity in human-dominated landscapes, we investigate the effect of land use types on plant and arthropod diversity in traditionally managed cornfields, via surveys of plants and arthropods in twelve traditional cornfields in the Colombian Andes. We estimated alpha and beta diversity to analyze changes in diversity related to land uses within a radius of 100 m to 1 km around each cornfield. We observed that forests influenced alpha diversity of plants, but not of arthropods. Agricultural lands had a positive relationship with plants and herbivores, but a negative relationship with predators. Pastures positively influenced the diversity of plants and arthropods. In addition, forest cover seemed to influence changes in plant species composition and species turnover of herbivore communities among cornfields. The dominant plant species varied among fields, resulting in high differentiation of plant communities. Predator communities also exhibited high turnover among cornfields, but differences in composition arose mainly among rare species. The crop system evaluated in this study represents a widespread situation in the tropics, therefore, our results can be of broad significance. Our findings suggest that traditional agriculture may not homogenize biological communities, but instead could maintain the regional pool of species through high beta diversity.

  17. Habitat Heterogeneity Affects Plant and Arthropod Species Diversity and Turnover in Traditional Cornfields

    PubMed Central

    Martínez, Eliana; Rös, Matthias; Bonilla, María Argenis; Dirzo, Rodolfo

    2015-01-01

    The expansion of the agricultural frontier by the clearing of remnant forests has led to human-dominated landscape mosaics. Previous studies have evaluated the effect of these landscape mosaics on arthropod diversity at local spatial scales in temperate and tropical regions, but little is known about fragmentation effects in crop systems, such as the complex tropical traditional crop systems that maintain a high diversity of weeds and arthropods in low-Andean regions. To understand the factors that influence patterns of diversity in human-dominated landscapes, we investigate the effect of land use types on plant and arthropod diversity in traditionally managed cornfields, via surveys of plants and arthropods in twelve traditional cornfields in the Colombian Andes. We estimated alpha and beta diversity to analyze changes in diversity related to land uses within a radius of 100 m to 1 km around each cornfield. We observed that forests influenced alpha diversity of plants, but not of arthropods. Agricultural lands had a positive relationship with plants and herbivores, but a negative relationship with predators. Pastures positively influenced the diversity of plants and arthropods. In addition, forest cover seemed to influence changes in plant species composition and species turnover of herbivore communities among cornfields. The dominant plant species varied among fields, resulting in high differentiation of plant communities. Predator communities also exhibited high turnover among cornfields, but differences in composition arose mainly among rare species. The crop system evaluated in this study represents a widespread situation in the tropics, therefore, our results can be of broad significance. Our findings suggest that traditional agriculture may not homogenize biological communities, but instead could maintain the regional pool of species through high beta diversity. PMID:26197473

  18. Moving forward on facilitation research: response to changing environments and effects on the diversity, functioning and evolution of plant communities.

    PubMed

    Soliveres, Santiago; Smit, Christian; Maestre, Fernando T

    2015-02-01

    Once seen as anomalous, facilitative interactions among plants and their importance for community structure and functioning are now widely recognized. The growing body of modelling, descriptive and experimental studies on facilitation covers a wide variety of terrestrial and aquatic systems throughout the globe. However, the lack of a general body of theory linking facilitation among different types of organisms and biomes and their responses to environmental changes prevents further advances in our knowledge regarding the evolutionary and ecological implications of facilitation in plant communities. Moreover, insights gathered from alternative lines of inquiry may substantially improve our understanding of facilitation, but these have been largely neglected thus far. Despite over 15 years of research and debate on this topic, there is no consensus on the degree to which plant-plant interactions change predictably along environmental gradients (i.e. the stress-gradient hypothesis), and this hinders our ability to predict how plant-plant interactions may affect the response of plant communities to ongoing global environmental change. The existing controversies regarding the response of plant-plant interactions across environmental gradients can be reconciled when clearly considering and determining the species-specificity of the response, the functional or individual stress type, and the scale of interest (pairwise interactions or community-level response). Here, we introduce a theoretical framework to do this, supported by multiple lines of empirical evidence. We also discuss current gaps in our knowledge regarding how plant-plant interactions change along environmental gradients. These include the existence of thresholds in the amount of species-specific stress that a benefactor can alleviate, the linearity or non-linearity of the response of pairwise interactions across distance from the ecological optimum of the beneficiary, and the need to explore further how

  19. Influences of Plant Species, Season and Location on Leaf Endophytic Bacterial Communities of Non-Cultivated Plants.

    PubMed

    Ding, Tao; Melcher, Ulrich

    2016-01-01

    Bacteria are known to be associated endophytically with plants. Research on endophytic bacteria has identified their importance in food safety, agricultural production and phytoremediation. However, the diversity of endophytic bacterial communities and the forces that shape their compositions in non-cultivated plants are largely uncharacterized. In this study, we explored the diversity, community structure, and dynamics of endophytic bacteria in different plant species in the Tallgrass Prairie Preserve of northern Oklahoma, USA. High throughput sequencing of amplified segments of bacterial rDNA from 81 samples collected at four sampling times from five plant species at four locations identified 335 distinct OTUs at 97% sequence similarity, representing 16 phyla. Proteobacteria was the dominant phylum in the communities, followed by the phyla Bacteriodetes and Actinobacteria. Bacteria from four classes of Proteobacteria were detected with Alphaproteobacteria as the dominant class. Analysis of molecular variance revealed that host plant species and collecting date had significant influences on the compositions of the leaf endophytic bacterial communities. The proportion of Alphaproteobacteria was much higher in the communities from Asclepias viridis than from other plant species and differed from month to month. The most dominant bacterial groups identified in LDA Effect Size analysis showed host-specific patterns, indicating mutual selection between host plants and endophytic bacteria and that leaf endophytic bacterial compositions were dynamic, varying with the host plant's growing season in three distinct patterns. In summary, next generation sequencing has revealed variations in the taxonomic compositions of leaf endophytic bacterial communities dependent primarily on the nature of the plant host species.

  20. Plant water use efficiency over geological time--evolution of leaf stomata configurations affecting plant gas exchange.

    PubMed

    Assouline, Shmuel; Or, Dani

    2013-01-01

    Plant gas exchange is a key process shaping global hydrological and carbon cycles and is often characterized by plant water use efficiency (WUE - the ratio of CO2 gain to water vapor loss). Plant fossil record suggests that plant adaptation to changing atmospheric CO2 involved correlated evolution of stomata density (d) and size (s), and related maximal aperture, amax . We interpreted the fossil record of s and d correlated evolution during the Phanerozoic to quantify impacts on gas conductance affecting plant transpiration, E, and CO2 uptake, A, independently, and consequently, on plant WUE. A shift in stomata configuration from large s-low d to small s-high d in response to decreasing atmospheric CO2 resulted in large changes in plant gas exchange characteristics. The relationships between gas conductance, gws , A and E and maximal relative transpiring leaf area, (amax ⋅d), exhibited hysteretic-like behavior. The new WUE trend derived from independent estimates of A and E differs from established WUE-CO2 trends for atmospheric CO2 concentrations exceeding 1,200 ppm. In contrast with a nearly-linear decrease in WUE with decreasing CO2 obtained by standard methods, the newly estimated WUE trend exhibits remarkably stable values for an extended geologic period during which atmospheric CO2 dropped from 3,500 to 1,200 ppm. Pending additional tests, the findings may affect projected impacts of increased atmospheric CO2 on components of the global hydrological cycle.

  1. Educational Plant Survey: Polk Community College, June 6-10, 1994.

    ERIC Educational Resources Information Center

    Bullock, Thomas K.; And Others

    Polk Community College's educational plant survey was conducted as a systematic study and evaluation of existing educational facilities and the determination of future educational plant needs. The educational plant survey is intended to assist the District Board of Trustees in the formulation of plans for housing the educational program, student…

  2. Loss of a large grazer impacts savanna grassland plant communities similarly in North America and South Africa.

    PubMed

    Eby, Stephanie; Burkepile, Deron E; Fynn, Richard W S; Burns, Catherine E; Govender, Navashni; Hagenah, Nicole; Koerner, Sally E; Matchett, Katherine J; Thompson, Dave I; Wilcox, Kevin R; Collins, Scott L; Kirkman, Kevin P; Knapp, Alan K; Smith, Melinda D

    2014-05-01

    Large herbivore grazing is a widespread disturbance in mesic savanna grasslands which increases herbaceous plant community richness and diversity. However, humans are modifying the impacts of grazing on these ecosystems by removing grazers. A more general understanding of how grazer loss will impact these ecosystems is hampered by differences in the diversity of large herbivore assemblages among savanna grasslands, which can affect the way that grazing influences plant communities. To avoid this we used two unique enclosures each containing a single, functionally similar large herbivore species. Specifically, we studied a bison (Bos bison) enclosure at Konza Prairie Biological Station, USA and an African buffalo (Syncerus caffer) enclosure in Kruger National Park, South Africa. Within these enclosures we erected exclosures in annually burned and unburned sites to determine how grazer loss would impact herbaceous plant communities, while controlling for potential fire-grazing interactions. At both sites, removal of the only grazer decreased grass and forb richness, evenness and diversity, over time. However, in Kruger these changes only occurred with burning. At both sites, changes in plant communities were driven by increased dominance with herbivore exclusion. At Konza, this was caused by increased abundance of one grass species, Andropogon gerardii, while at Kruger, three grasses, Themeda triandra, Panicum coloratum, and Digitaria eriantha increased in abundance.

  3. Spatial scale affects community concordance among fishes, benthic macroinvertebrates, and bryophytes in streams.

    PubMed

    Paavola, Riku; Muotka, Timo; Virtanen, Risto; Heino, Jani; Jackson, Donald; Maki-Petäys, Aki

    2006-02-01

    Owing to the lack of information about the distribution patterns of many taxonomic groups, biodiversity conservation strategies commonly rely on a surrogate taxa approach for identifying areas of maximum conservation potential. Macroinvertebrates or fish are the most likely candidates for such a role in many freshwater systems. The usefulness of the surrogate taxa depends largely on community concordance, i.e., the degree of similarity in community patterns among taxonomic groups across a set of sites. We examined the effect of the spatial scale of a. study on the strength of community concordance among macroinvertebrates, bryophytes, and fish by comparing the concordance between ordinations of these groups in 101 boreal stream sites. We specifically asked if communities spanning several drainages are more concordant than those originating from a single drainage system. Our results indicate that community concordance is affected by spatial extent, being variable and generally weak at the scale of individual drainages, but strong across multiple drainage systems and ecoregions. We attribute this finding to different taxonomic groups responding to similar environmental factors and sharing a similar latitudinal gradient of community structure when viewed across large spatial scales. We also identified a "gradient of concordance," with sites contributing disproportionately to community concordance being in relatively large streams with high microhabitat variability. Overall, our results suggest that the degree of community concordance among freshwater organism groups depends critically on the spatial extent of the study, and surrogate groups at the scale of single river systems should be used with caution.

  4. Microbial community analysis of switchgrass planted and unplanted soil microcosms displaying PCB dechlorination

    PubMed Central

    Liang, Yi; Meggo, Richard; Hu, Dingfei; Schnoor, Jerald L.; Mattes, Timothy E.

    2015-01-01

    Polychlorinated biphenyls (PCBs) pose potential risks to human and environmental health because they are carcinogenic, persistent and bioaccumulative. In this study we investigated bacterial communities in soil microcosms spiked with PCB 52, 77 and 153. Switchgrass (Panicum virgatum) was employed to improve overall PCB removal and redox cycling (i.e. sequential periods of flooding followed by periods of no flooding) was performed in an effort to promote PCB dechlorination. Lesser chlorinated PCB transformation products were detected in all microcosms, indicating the occurrence of PCB dechlorination. Terminal restriction fragment length polymorphism (T-RFLP) and clone library analysis showed that PCB spiking, switchgrass planting and redox cycling affected the microbial community structure. Putative organohalide-respiring Chloroflexi populations, which were not found in unflooded microcosms, were enriched after two weeks of flooding in the redox-cycled microcosms. Sequences classified as Geobacter sp. were detected in all microcosms, and were most abundant in the switchgrass-planted microcosm spiked with PCB congeners. The presence of possible organohalide-respiring bacteria in these soil microcosms suggests they play a role in PCB dechlorination therein. PMID:25820643

  5. Plant Litter Submergence Affects the Water Quality of a Constructed Wetland

    PubMed Central

    Cui, Lijuan; Li, Wei; Zhang, Xiaodong; Zhou, Jian; Yu, Fei-Hai; Prinzing, Andreas

    2017-01-01

    Plant litter is an indispensable component of constructed wetlands, but how the submergence of plant litter affects their ecosystem functions and services, such as water purification, is still unclear. Moreover, it is also unclear whether the effects of plant litter submergence depend on other factors such as the duration of litter submergence, water source or litter species identity. Here we conducted a greenhouse experiment by submerging the litter of 7 wetland plant species into three types of water substrates and monitoring changes in water nutrient concentrations. Litter submergence affected water quality positively via decreasing the concentration of nitrate nitrogen and negatively via increasing the concentrations of total nitrogen, ammonium nitrogen and total phosphorus. The effects of litter submergence depended on the duration of litter submergence, the water source, the litter species identity, and the plant life form. Different plant species had different effects on the water nutrient concentrations during litter submergence, and the effects of floating plants might be more negative than that of emergent plants. These results are novel evidence of how the submergence of different plant (life form) litter may affect the purification function of constructed wetlands. For water at low eutrophication levels, submerging a relative small amount of plant litter might improve water quality, via benefiting the denitrification process in water. These findings emphasized the management of floating plant litter (a potential removal) during the maintenance of human-controlled wetland ecosystems and provided a potential tool to improve the water quality of constructed wetlands via submerging plant litter of different types. PMID:28129405

  6. Above- and below-ground vertebrate herbivory may each favour a different subordinate species in an aquatic plant community.

    PubMed

    Hidding, Bert; Nolet, Bart A; de Boer, Thijs; de Vries, Peter P; Klaassen, Marcel

    2010-01-01

    At least two distinct trade-offs are thought to facilitate higher diversity in productive plant communities under herbivory. Higher investment in defence and enhanced colonization potential may both correlate with decreased competitive ability in plants. Herbivory may thus promote coexistence of plant species exhibiting divergent life history strategies. How different seasonally tied herbivore assemblages simultaneously affect plant community composition and diversity is, however, largely unknown. Two contrasting types of herbivory can be distinguished in the aquatic vegetation of the shallow lake Lauwersmeer. In summer, predominantly above-ground tissues are eaten, whereas in winter, waterfowl forage on below-ground plant propagules. In a 4-year exclosure study we experimentally separated above-ground herbivory by waterfowl and large fish in summer from below-ground herbivory by Bewick's swans in winter. We measured the individual and combined effects of both herbivory periods on the composition of the three-species aquatic plant community. Herbivory effect sizes varied considerably from year to year. In 2 years herbivore exclusion in summer reinforced dominance of Potamogeton pectinatus with a concomitant decrease in Potamogeton pusillus, whereas no strong, unequivocal effect was observed in the other 2 years. Winter exclusion, on the other hand, had a negative effect on Zannichellia palustris, but the effect size differed considerably between years. We suggest that the colonization ability of Z. palustris may have enabled this species to be more abundant after reduction of P. pectinatus tuber densities by swans. Evenness decreased due to herbivore exclusion in summer. We conclude that seasonally tied above- and below-ground herbivory may each stimulate different components of a macrophyte community as they each favoured a different subordinate plant species.

  7. Plant Invasions Associated with Change in Root-Zone Microbial Community Structure and Diversity

    PubMed Central

    Rodrigues, Richard R.; Pineda, Rosana P.; Barney, Jacob N.; Nilsen, Erik T.; Barrett, John E.; Williams, Mark A.

    2015-01-01

    The importance of plant-microbe associations for the invasion of plant species have not been often tested under field conditions. The research sought to determine patterns of change in microbial communities associated with the establishment of invasive plants with different taxonomic and phenetic traits. Three independent locations in Virginia, USA were selected. One site was invaded by a grass (Microstegium vimineum), another by a shrub (Rhamnus davurica), and the third by a tree (Ailanthus altissima). The native vegetation from these sites was used as reference. 16S rRNA and ITS regions were sequenced to study root-zone bacterial and fungal communities, respectively, in invaded and non-invaded samples and analyzed using Quantitative Insights Into Microbial Ecology (QIIME). Though root-zone microbial community structure initially differed across locations, plant invasion shifted communities in similar ways. Indicator species analysis revealed that Operational Taxonomic Units (OTUs) closely related to Proteobacteria, Acidobacteria, Actinobacteria, and Ascomycota increased in abundance due to plant invasions. The Hyphomonadaceae family in the Rhodobacterales order and ammonia-oxidizing Nitrospirae phylum showed greater relative abundance in the invaded root-zone soils. Hyphomicrobiaceae, another bacterial family within the phyla Proteobacteria increased as a result of plant invasion, but the effect associated most strongly with root-zones of M. vimineum and R. davurica. Functional analysis using Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) showed bacteria responsible for nitrogen cycling in soil increased in relative abundance in association with plant invasion. In agreement with phylogenetic and functional analyses, greater turnover of ammonium and nitrate was associated with plant invasion. Overall, bacterial and fungal communities changed congruently across plant invaders, and support the hypothesis that nitrogen

  8. Plant Invasions Associated with Change in Root-Zone Microbial Community Structure and Diversity.

    PubMed

    Rodrigues, Richard R; Pineda, Rosana P; Barney, Jacob N; Nilsen, Erik T; Barrett, John E; Williams, Mark A

    2015-01-01

    The importance of plant-microbe associations for the invasion of plant species have not been often tested under field conditions. The research sought to determine patterns of change in microbial communities associated with the establishment of invasive plants with different taxonomic and phenetic traits. Three independent locations in Virginia, USA were selected. One site was invaded by a grass (Microstegium vimineum), another by a shrub (Rhamnus davurica), and the third by a tree (Ailanthus altissima). The native vegetation from these sites was used as reference. 16S rRNA and ITS regions were sequenced to study root-zone bacterial and fungal communities, respectively, in invaded and non-invaded samples and analyzed using Quantitative Insights Into Microbial Ecology (QIIME). Though root-zone microbial community structure initially differed across locations, plant invasion shifted communities in similar ways. Indicator species analysis revealed that Operational Taxonomic Units (OTUs) closely related to Proteobacteria, Acidobacteria, Actinobacteria, and Ascomycota increased in abundance due to plant invasions. The Hyphomonadaceae family in the Rhodobacterales order and ammonia-oxidizing Nitrospirae phylum showed greater relative abundance in the invaded root-zone soils. Hyphomicrobiaceae, another bacterial family within the phyla Proteobacteria increased as a result of plant invasion, but the effect associated most strongly with root-zones of M. vimineum and R. davurica. Functional analysis using Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) showed bacteria responsible for nitrogen cycling in soil increased in relative abundance in association with plant invasion. In agreement with phylogenetic and functional analyses, greater turnover of ammonium and nitrate was associated with plant invasion. Overall, bacterial and fungal communities changed congruently across plant invaders, and support the hypothesis that nitrogen

  9. Climate warming affects biological invasions by shifting interactions of plants and herbivores.

    PubMed

    Lu, Xinmin; Siemann, Evan; Shao, Xu; Wei, Hui; Ding, Jianqing

    2013-08-01

    Plants and herbivorous insects can each be dramatically affected by temperature. Climate warming may impact plant invasion success directly but also indirectly through changes in their natural enemies. To date, however, there are no tests of how climate warming shifts the interactions among invasive plants and their natural enemies to affect invasion success. Field surveys covering the full latitudinal range of invasive Alternanthera philoxeroides in China showed that a beetle introduced for biocontrol was rare or absent at higher latitudes. In contrast, plant cover and mass increased with latitude. In a 2-year field experiment near the northern limit of beetle distribution, we found the beetle sustained populations across years under elevated temperature, dramatically decreasing A. philoxeroides growth, but it failed to overwinter in ambient temperature. Together, these results suggest that warming will allow the natural enemy to expand its range, potentially benefiting biocontrol in regions that are currently too cold for the natural enemy. However, the invader may also expand its range further north in response to warming. In such cases where plants tolerate cold better than their natural enemies, the geographical gap between plant and herbivorous insect ranges may not disappear but will shift to higher latitudes, leading to a new zone of enemy release. Therefore, warming will not only affect plant invasions directly but also drive either enemy release or increase that will result in contrasting effects on invasive plants. The findings are also critical for future management of invasive species under climate change.

  10. Negative effects of fluoranthene on the ecophysiology of tomato plants (Lycopersicon esculentum Mill) Fluoranthene mists negatively affected tomato plants.

    PubMed

    Oguntimehin, Ilemobayo; Eissa, Fawzy; Sakugawa, Hiroshi

    2010-02-01

    Cherry tomato plants (Lycopersicon esculentum Mill) were sprayed with fluoranthene and mixture of fluoranthene and mannitol solutions for 30d. The exposure was carried out in growth chambers in field conditions, and the air was filtered through charcoal filters to remove atmospheric contaminants. Plants were sprayed with 10microM fluoranthene as mist until they reached the fruiting stage, and the eco-physiological parameters were measured to determine the effects of the treatments. We measured CO(2) uptake and water vapour exchange, chlorophyll fluorescence, leaf pigment contents, visual symptoms and biomass allocation. Fluoranthene which was deposited as mist onto leaves negatively affected both growth and the quality of tomato plants, while other treatments did not. The photosynthetic rate measured at saturated irradiance was approximately 37% lower in fluoranthene-treated plants compared with the control group. Other variables, such as stomata conductance, the photochemical efficiency of PSII in the dark, Chl a, Chl b, and the total chlorophyll contents of the tomato leaves were significantly reduced in the fluoranthene-treated plants. Tomato plants treated with fluoranthene showed severe visible injury symptoms on the foliage during the exposure period. Mannitol (a reactive oxygen scavenger) mitigated effects of fluoranthene; thus, reactive oxygen species generated through fluoranthene may be responsible for the damaged tomato plants. It is possible for fluoranthene to decrease the aesthetic and hence the economic value of this valuable crop plant.

  11. Disparate effects of plant genotypic diversity on foliage and litter arthropod communities.

    PubMed

    Crutsinger, Gregory M; Reynolds, W Nicholas; Classen, Aimée T; Sanders, Nathan J

    2008-11-01

    Intraspecific diversity can influence the structure of associated communities, though whether litter-based and foliage-based arthropod communities respond to intraspecific diversity in similar ways remains unclear. In this study, we compared the effects of host-plant genotype and genotypic diversity of the perennial plant, Solidago altissima, on the arthropod community associated with living plant tissue (foliage-based community) and microarthropods associated with leaf litter (litter-based community). We found that variation among host-plant genotypes had strong effects on the diversity and composition of foliage-based arthropods, but only weak effects on litter-based microarthropods. Furthermore, host-plant genotypic diversity was positively related to the abundance and diversity of foliage-based arthropods, and within the herbivore and predator trophic levels. In contrast, there were minimal effects of plant genotypic diversity on litter-based microarthropods in any trophic level. Our study illustrates that incorporating communities associated with living foliage and senesced litter into studies of community genetics can lead to very different conclusions about the importance of intraspecific diversity than when only foliage-based community responses are considered in isolation.

  12. Microbial composition in a deep saline aquifer in the North German Basin -microbiologically induced corrosion and mineral precipitation affecting geothermal plant operation and the effects of plant downtime

    NASA Astrophysics Data System (ADS)

    Lerm, Stephanie; Westphal, Anke; Miethling-Graff, Rona; Alawi, Mashal; Seibt, Andrea; Wolfgramm, Markus; Würdemann, Hilke

    2013-04-01

    The microbial composition in fluids of a deep saline geothermal used aquifer in the North German Basin was characterized over a period of five years. The genetic fingerprinting techniques PCR-SSCP and PCR-DGGE revealed distinct microbial communities in fluids produced from the cold and warm side of the aquifer. Direct cell counting and quantification of 16S rRNA genes and dissimilatory sulfite reductase (dsrA) genes by real-time PCR proved different population sizes in fluids, showing higher abundance of Bacteria and sulfate reducing bacteria (SRB) in cold fluids compared to warm fluids. Predominating SRB in the cold well probably accounted for corrosion damage to the submersible well pump, and iron sulfide precipitates in the near wellbore area and topside facility filters. This corresponded to a lower sulfate content in fluids produced from the cold well as well as higher content of hydrogen gas that was probably released from corrosion, and maybe favoured growth of hydrogenotrophic SRB. Plant downtime significantly influenced the microbial biocenosis in fluids. Samples taken after plant restart gave indications about the processes occurring downhole during those phases. High DNA concentrations in fluids at the beginning of the restart process with a decreasing trend over time indicated a higher abundance of microbes during plant downtime compared to regular plant operation. It is likely that a gradual drop in temperature as well as stagnant conditions favoured the growth of microbes and maturation of biofilms at the casing and in pores of the reservoir rock in the near wellbore area. Furthermore, it became obvious that the microorganisms were more associated to particles then free-living. This study reflects the high influence of microbial populations for geothermal plant operation, because microbiologically induced precipitative and corrosive processes adversely affect plant reliability. Those processes may favourably occur during plant downtime due to enhanced

  13. Minimum Wage and Community College Attendance: How Economic Circumstances Affect Educational Choices

    ERIC Educational Resources Information Center

    Williams, Betsy

    2013-01-01

    How do changes in minimum wages affect community college enrollment and employment? In particular, among adults without associate's or bachelor's degrees who may earn near the minimum wage, do endowment effects of a higher minimum wage encourage school attendance? Among adults without associate's or bachelor's degrees who may earn near the minimum…

  14. Death and Grief: A Plan for Principals to Deal with Tragedy Affecting the School Community.

    ERIC Educational Resources Information Center

    Powers, Harry L.

    1987-01-01

    Spurred by the "Challenger" space shuttle tragedy, this article provides principals with guidelines for informing individual students about family deaths and dealing with grief affecting the entire school community. Thorough preparation can reduce intensity and misconceived actions associated with grief and demonstrate administrative leadership.…

  15. Plant compartment and biogeography affect microbiome composition in cultivated and native Agave species.

    PubMed

    Coleman-Derr, Devin; Desgarennes, Damaris; Fonseca-Garcia, Citlali; Gross, Stephen; Clingenpeel, Scott; Woyke, Tanja; North, Gretchen; Visel, Axel; Partida-Martinez, Laila P; Tringe, Susannah G

    2016-01-01

    Desert plants are hypothesized to survive the environmental stress inherent to these regions in part thanks to symbioses with microorganisms, and yet these microbial species, the communities they form, and the forces that influence them are poorly understood. Here we report the first comprehensive investigation of the microbial communities associated with species of Agave, which are native to semiarid and arid regions of Central and North America and are emerging as biofuel feedstocks. We examined prokaryotic and fungal communities in the rhizosphere, phyllosphere, leaf and root endosphere, as well as proximal and distal soil samples from cultivated and native agaves, through Illumina amplicon sequencing. Phylogenetic profiling revealed that the composition of prokaryotic communities was primarily determined by the plant compartment, whereas the composition of fungal communities was mainly influenced by the biogeography of the host species. Cultivated A. tequilana exhibited lower levels of prokaryotic diversity compared with native agaves, although no differences in microbial diversity were found in the endosphere. Agaves shared core prokaryotic and fungal taxa known to promote plant growth and confer tolerance to abiotic stress, which suggests common principles underpinning Agave-microbe interactions.

  16. Crop size, plant aggregation, and microhabitat type affect fruit removal by birds from individual melastome plants in the Upper Amazon.

    PubMed

    Blendinger, Pedro G; Loiselle, Bette A; Blake, John G

    2008-11-01

    We studied the efficiency (proportion of the crop removed) and quantitative effectiveness (number of fruits removed) of dispersal of Miconia fosteri and M. serrulata (Melastomataceae) seeds by birds in lowland tropical wet forest of Ecuador. Specifically, we examined variation in fruit removal in order to reveal the spatial scale at which crop size influences seed dispersal outcome of individual plants, and to evaluate how the effect of crop size on plant dispersal success may be affected by conspecific fruit abundance and by the spatial distribution of frugivore abundance. We established two 9-ha plots in undisturbed terra-firme understory, where six manakin species (Pipridae) disperse most seeds of these two plant species. Mean levels of fruit removal were low for both species, with high variability among plants. In general, plants with larger crop sizes experienced greater efficiency and effectiveness of fruit removal than plants with smaller crops. Fruit removal, however, was also influenced by microhabitat, such as local topography and local neighborhood. Fruit-rich and disperser-rich patches overlapped spatially for M. fosteri but not M. serrulata, nonetheless fruit removal of M. serrulata was still much greater in fruit-rich patches. Fruit removal from individual plants did not decrease in patches with many fruiting conspecifics and, in fact, removal effectiveness was enhanced for M. fosteri with small crop sizes when such plants were in patches with more conspecifics. These results suggest that benefits of attracting dispersers to a patch balanced or outweighed the costs of competition for dispersers. Spatial pattern of fruit removal, a measure of plant fitness, depended on a complex interaction among plant traits, spatial patterns of plant distribution, and disperser behavior.

  17. The effects of timing of grazing on plant and arthropod communities in high-elevation grasslands.

    PubMed

    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.

  18. Mechanisms and ecological consequences of plant defence induction and suppression in herbivore communities

    PubMed Central

    Kant, M. R.; Jonckheere, W.; Knegt, B.; Lemos, F.; Liu, J.; Schimmel, B. C. J.; Villarroel, C. A.; Ataide, L. M. S.; Dermauw, W.; Glas, J. J.; Egas, M.; Janssen, A.; Van Leeuwen, T.; Schuurink, R. C.; Sabelis, M. W.; Alba, J. M.

    2015-01-01

    give rise to exploitative competition and facilitation within ecological communities “inhabiting” a plant. Conclusions Herbivores have evolved diverse strategies, which are not mutually exclusive, to decrease the negative effects of plant defences in order to maximize the conversion of plant material into offspring. Numerous adaptations have been found in herbivores, enabling them to dismantle or bypass defensive barriers, to avoid tissues with relatively high levels of defensive chemicals or to metabolize these chemicals once ingested. In addition, some herbivores interfere with the onset or completion of induced plant defences, resulting in the plant’s resistance being partly or fully suppressed. The ability to suppress induced plant defences appears to occur across plant parasites from different kingdoms, including herbivorous arthropods, and there is remarkable diversity in suppression mechanisms. Suppression may strongly affect the structure of the food web, because the ability to suppress the activation of defences of a communal host may facilitate competitors, whereas the ability of a herbivore to cope with activated plant defences will not. Further characterization of the mechanisms and traits that give rise to suppression of plant defences will enable us to determine their role in shaping direct and indirect interactions in food webs and the extent to which these determine the coexistence and persistence of species. PMID:26019168

  19. Land use imperils plant and animal communi