The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Richard D Bardgett - One of the best experts on this subject based on the ideXlab platform.
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effects of Species Evenness and dominant Species identity on multiple ecosystem functions in model grassland communities
Oecologia, 2014Co-Authors: Kate H Orwin, N J Ostle, Andrew Wilby, Richard D BardgettAbstract:Ecosystems provide multiple services upon which humans depend. Understanding the drivers of the ecosystem functions that support these services is therefore important. Much research has investigated how Species richness influences functioning, but we lack knowledge of how other community attributes affect ecosystem functioning. Species Evenness, Species spatial arrangement, and the identity of dominant Species are three attributes that could affect ecosystem functioning, by altering the relative abundance of functional traits and the probability of synergistic Species interactions such as facilitation and complementary resource use. We tested the effect of these three community attributes and their interactions on ecosystem functions over a growing season, using model grassland communities consisting of three plant Species from three functional groups: a grass (Anthoxanthum odoratum), a forb (Plantago lanceolata), and a N-fixing forb (Lotus corniculatus). We measured multiple ecosystem functions that support ecosystem services, including ecosystem gas exchange, water retention, C and N loss in leachates, and plant biomass production. Species Evenness and dominant Species identity strongly influenced the ecosystem functions measured, but spatial arrangement had few effects. By the end of the growing season, Evenness consistently enhanced ecosystem functioning and this effect occurred regardless of dominant Species identity. The identity of the dominant Species under which the highest level of functioning was attained varied across the growing season. Spatial arrangement had the weakest effect on functioning, but interacted with dominant Species identity to affect some functions. Our results highlight the importance of understanding the role of multiple community attributes in driving ecosystem functioning.
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changes in Species Evenness of litter have no effect on decomposition processes
Soil Biology & Biochemistry, 2002Co-Authors: Rosalind King, Karsten M Dromph, Richard D BardgettAbstract:Most studies on the importance of litter diversity to decomposition processes have examined effects of Species richness, and have not considered the other important aspect of biodiversity, namely Evenness (relative abundance of Species). Using microcosms, we investigated how changes in Species Evenness and identity of litters (taken from a regenerating Betula pendula forest) affected decomposition processes. We showed that single litter Species varied in their rate of decomposition (bilberry 44.4%, willow 49.9%, rowan 53.7% and birch 54.8% weight loss after 234 days). However, when in mixtures, changes in the Evenness of these litters and the identity of the dominant Species had no detectable effect on measures of decomposition such as weight loss (42.6–56.6% after 234 days), microbial respiration and dissolved organic carbon and inorganic nitrogen release. Dissolved organic nitrogen release was found to be significantly greater from high Evenness litter mixtures, 0.236 mg l−1, than the single Species treatments, 0.145 mg l−1, but only during the initial stages of the experiment. These results, therefore, provide no support for the idea that changes in Evenness of litter inputs and the identity of dominant litters will affect decomposition processes and soil nutrient availability.
Matthew Scott Luskin - One of the best experts on this subject based on the ideXlab platform.
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global signal of top down control of terrestrial plant communities by herbivores
Proceedings of the National Academy of Sciences of the United States of America, 2018Co-Authors: Shihong Jia, Xugao Wang, Zuoqiang Yuan, Fei Lin, Zhanqing Hao, Matthew Scott LuskinAbstract:The theory of "top-down" ecological regulation predicts that herbivory suppresses plant abundance, biomass, and survival but increases diversity through the disproportionate consumption of dominant Species, which inhibits competitive exclusion. To date, these outcomes have been clear in aquatic ecosystems but not on land. We explicate this discrepancy using a meta-analysis of experimental results from 123 native animal exclusions in natural terrestrial ecosystems (623 pairwise comparisons). Consistent with top-down predictions, we found that herbivores significantly reduced plant abundance, biomass, survival, and reproduction (all P < 0.01) and increased Species Evenness but not richness (P = 0.06 and P = 0.59, respectively). However, when examining patterns in the strength of top-down effects, with few exceptions, we were unable to detect significantly different effect sizes among biomes, based on local site characteristics (climate or productivity) or study characteristics (study duration or exclosure size). The positive effects on diversity were only significant in studies excluding large animals or located in temperate grasslands. The results demonstrate that top-down regulation by herbivores is a pervasive process shaping terrestrial plant communities at the global scale, but its strength is highly site specific and not predicted by basic site conditions. We suggest that including herbivore densities as a covariate in future exclosure studies will facilitate the discovery of unresolved macroecology trends in the strength of herbivore-plant interactions.
Rebecca R Hernandez - One of the best experts on this subject based on the ideXlab platform.
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late successional biological soil crusts in a biodiversity hotspot an example of congruency in Species richness
Biodiversity and Conservation, 2012Co-Authors: Rebecca R Hernandez, Kerry KnudsenAbstract:Understanding the biodiversity of functionally important communities in Earth's ecosystems is vital in the apportionment of limited ecosystem management funds and efforts. In southern California shrublands, which lie in a global biodiversity hotspot, biological soil crusts (BSCs) confer critical ecosystem services; however, their biodiver- sity remains unknown. In this study, six sites (n = 4 each, 25 m 2 ) were established along a mediterranean shrubland environmental gradient in southern California. Here, the biodi- versity of all BSC-forming lichens and bryophytes was evaluated, related to environmental traits along the gradient, and compared to Species richness among North American eco- systems supporting BSCs (data from previous studies). In total, 59 BSC-forming lichens and bryophytes were observed, including the very rare Sarcogyne crustacea, a rare moss, and five endemic lichen Species. Over half (61%) of the Species observed were found at a single site. Along the gradient, Species Evenness of late-successional BSC was related to dew point and elevation, and both Evenness and richness were related to distance to coast. Using an ordination analysis, five distinct late-successional BSC communities were identified: Riversidian, Spike moss, Casperian, Alisian, and Lagunian. Twenty-five lichens and 19 bryophytes are newly reported for North American BSC-forming organisms, now comprising *1/2 of the North American total. BSCs in North American hot and cold
Sara M Kross - One of the best experts on this subject based on the ideXlab platform.
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a bustle in the hedgerow woody field margins boost on farm avian diversity and abundance in an intensive agricultural landscape
Biological Conservation, 2017Co-Authors: Sacha K Heath, Candan U Soykan, Karen L Velas, Rodd Kelsey, Sara M KrossAbstract:Abstract Considerable funding has been allocated to conservation management of non-crop habitat in agricultural landscapes, particularly field margin habitat such as hedgerows. Evaluation of the biodiversity benefits of non-crop habitat has lagged behind implementation, however, especially in the United States where this habitat has the potential to supply important resources for both common and rare Species of birds. We examined the effects of woody field margin vegetation on winter and breeding season avian communities at 103 fields, row crops, and orchards in California's Central Valley, one of the most intensively-farmed landscapes on Earth. We found that margins with hedgerows, treelines or remnant riparian habitat harbored 2–3 times as many bird Species, significantly greater Species Evenness, and 3–6 times higher maximum total abundances of birds than bare or weedy margins. The effect of margin type on richness was modulated by water year, whereas the effect of margin type on maximum total abundance was modulated by adjacent crop type. At the landscape scale, hedgerow and riparian margins that were further from woodland harbored greater Species richness; a result that supports our recommendation for targeted development of hedgerows in simplified agricultural landscapes. These results demonstrate that non-crop woody habitats, both planted and remnant native patches, increase the biodiversity value of farms, providing support for policies to preserve remaining habitat and incentivize installation of woody hedgerows.
Brian J Wilsey - One of the best experts on this subject based on the ideXlab platform.
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Biodiversity and tallgrass prairie decomposition: the relative importance of Species identity, Evenness, richness, and micro-topography
Plant Ecology, 2009Co-Authors: Timothy L. Dickson, Brian J WilseyAbstract:Biodiversity has been declining in many areas, and there is great interest in determining whether this decline affects ecosystem functioning. Most biodiversity—ecosystem functioning studies have focused on the effects of Species richness on net primary productivity. However, biodiversity encompasses both Species richness and Evenness, ecosystem functioning includes other important processes such as decomposition, and the effects of richness on ecosystem functioning may change at different levels of Evenness. Here, we present two experiments on the effects of litter Species Evenness and richness on litter decomposition. In the first experiment, we varied the Species Evenness (three levels), identity of the dominant Species (three Species), and micro-topographic position (low points [gilgais] or high points between gilgais) of litter in three-Species mixtures in a prairie in Texas, USA. In a second experiment, we varied the Species Evenness (three levels), richness (one, two, or four Species per bag), and composition (random draws) of litter in a prairie in Iowa, USA. Greater Species Evenness significantly increased decomposition, but this effect was dependent on the environmental context. Higher Evenness increased decomposition rates only under conditions of higher water availability (in gilgais in the first experiment) or during the earliest stages of decomposition (second experiment). Species richness had no significant effect on decomposition, nor did it interact with Evenness. Micro-topographic position and Species identity and composition had larger effects on decomposition than Species Evenness. These results suggest that the effects of litter Species diversity on decomposition are more likely to be manifested through the Evenness component of diversity than the richness component, and that diversity effects are likely to be environmentally context dependent.
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realistically low Species Evenness does not alter grassland Species richness productivity relationships
Ecology, 2004Co-Authors: Brian J Wilsey, Wayne H PolleyAbstract:Biodiversity is declining worldwide from reductions in both Species richness and Evenness. Field experiments have shown that primary productivity is often reduced when richness of plant Species is lowered. However, experiments testing richness effects have used Evenness levels that are much higher than normally encountered in plant com- munities and have been based on the assumption that Species extinctions are random. We experimentally varied, for the first time, both Species richness (1-8 perennial Species/m 2 ) and Species Evenness (near maximal vs. realistically low) in grassland plots. Net primary productivity (NPP) and ecosystem CO2 uptake declined when richness was reduced, and reductions were similar between Evenness treatments. Richness effects were associated more with a selection effect than with complementarity (found only with high Evenness). Im- portantly, extinctions in plots during the second year were not random, but were greater at low than at high Evenness (i.e., with increased rarity) and in Species with low aboveground growth rates. Thus, Species Evenness can affect grassland ecosystem processes indirectly by affecting Species richness, and it will be imperative to understand how nonrandom extinctions affect NPP in future studies. Our results indicate that richness studies may not be biased by using mixtures with artificially high Evenness levels, but the results also demonstrate that results from these studies are directly applicable only to communities in which plant extinctions are random.
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do Species Evenness and plant density influence the magnitude of selection and complementarity effects in annual plant Species mixtures
Ecology Letters, 2003Co-Authors: Wayne H Polley, Brian J Wilsey, Justin D DernerAbstract:Plant Species richness influences primary productivity via mechanisms that (1) favour Species with particular traits (selection effect) and (2) promote niche differentiation between Species (complementarity). Influences of Species Evenness, plant density and other properties of plant communities on productivity are poorly defined, but may depend on whether selection or complementarity prevails in Species mixtures. We predicted that selection effects are insensitive to Species Evenness but increase with plant density, and that the converse is true for complementarity. To test predictions, we grew three Species of annuals in monocultures and in three-Species mixtures in which Evenness of established plants was varied at each of three plant densities in a cultivated field in Texas, USA. Above-ground biomass was smaller in mixtures than expected from monocultures because of negative complementarity and a negative selection effect. Neither selection nor complementarity varied with Species Evenness, but selection effects increased at the greatest plant density as predicted.
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reductions in grassland Species Evenness increase dicot seedling invasion and spittle bug infestation
Ecology Letters, 2002Co-Authors: Brian J Wilsey, Wayne H PolleyAbstract:Previous experiments that tested whether diverse plant communities have lower invasibility have all varied Species richness. We experimentally varied Evenness of four grassland Species (three grasses and one forb) by planting a field experiment in Texas, and monitored the number of unplanted dicot and monocot Species that invaded plots for two growing seasons. By varying Evenness, we eliminated any sampling effect in our diversity treatment, because all plots contained the same plant Species. Experimentally reducing Evenness led to a greater number of dicot invaders, which emerged in plots throughout the growing season, but had less of an effect on monocot invaders, which emerged in flushes when experimental plants were semi-dormant. Frequency of Solidago canadensis (altissima) stems with spittle bugs significantly increased with reductions in Evenness during the first year, apparently because the greater number of Solidago stems in high Evenness plots diluted the spittle-bug effect. These results support the view that higher diversity plant communities are more resistant to dicot invaders and insect herbivores.
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biodiversity and ecosystem functioning importance of Species Evenness in an old field
Ecology, 2000Co-Authors: Brian J Wilsey, Catherine PotvinAbstract:Changes in land use, habitat fragmentation, nutrient enrichment, and environmental stress often lead to reduced plant diversity in ecosystems. However, it remains controversial whether these reductions in diversity will affect energy flow and nutrient cycling. Diversity has two components: Species richness, or the number of plant Species in a given area, and Species Evenness, or how well distributed abundance or biomass is among Species within a community. We experimentally varied Species Evenness and the identity of the dominant plant Species in an old field of Quebec to test whether plant productivity would increase with increasing levels of Evenness, and whether relationships would be invariant with respect to Species identity. Total and belowground biomass increased linearly with increasing levels of Evenness after one growing season. These relationships did not depend on the identity of the dominant Species. Relationships between aboveground biomass and Evenness varied and depended on the identity of...
