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Orthoptera species abundance: Trophic Structure: Insect Species Diversity, Abundance and Body Size

The goal of this study was to examine the populations of insects in prairies and savannas. Most of the prairies had developed after being abandoned from agriculture, but none of the savannas had been cultivated. The history of burning varied between sites. The main sampling for this study was conducted in 1992 by the lead investigators: John Haarstad, Evan Siemann, and David Tilman. Insects were sampled via sweep-net sampling, pitfalls and ant scent plates throughout the growing season in each of 49 grassland fields and savannas. In total, 89,596 individuals of 1,167 species were captured and enumerated. Body size was measured for a subset of grasshoppers collected. In 2004, John Haarstad conducted two similar studies by identifying and enumerating all insects collected in sweepnet samples taken in old fields (prairies) as part of E014 grasshopper studies and from sweepnet samples taken in savannas.

Formicidae species (ants) abundance: Trophic Structure: Insect Species Diversity, Abundance and Body Size

All Insect Savanna Sweepnet Sampling 2004:Trophic Structure: Insect Species Diversity, Abundance and Body Size

Old Field All Arthropod Sweepnet Sampling 2004 :Trophic Structure: Insect Species Diversity, Abundance and Body Size

opencc-zeroDec 2014View details →

Data from: The good, the bad and the Ulva: the density dependent role of macroalgal subsidies in influencing diversity and trophic structure of an estuarine community

Worldwide, ecological subsidies enhance ecosystem productivity and therefore trophic support for greater biodiversity of taxa. While studies in terrestrial and aquatic ecosystems demonstrate that the magnitude of subsidies into ecosystems differs widely, the thresholds where subsidies may switch from exerting positive to negative effects are poorly understood. In estuaries, eutrophication promotes drift macroalgae that deposit on the benthos, cover intertidal flats for months and serve as pressed resource subsidies for benthic consumers. We hypothesized there would be a critical threshold of macroalgal biomass where ecosystem-level effects would turn from positive to negative. We used manipulative field experiments varying macroalgal mat thickness (0.5, 1.5 and 4 cm) over eight weeks and quantified effects on macrofauna on a lagoon mudflat in California. We documented that plots with mat depths of 0.5 and 1.5 cm had higher diversity by supporting both surface feeding and burrowing detritivores. Non-metric multidimensional scaling showed that the benthic community diverged with mat depth over the course of the experiment. After eight weeks, surface deposit feeders were associated mainly with 0.5 cm macroalgal subsidies, whereas subsurface deposit feeding capitellids were closely linked with 4 cm mats. Depth profiles of pore water sulfide concentration collected from 4 cm mats were 7622 ± 5294 μM, mean ± s.e., (mean of means across depth profiles), whereas 0.5 cm treatments resulted in sulfide concentrations that were 0.25% of the 4 cm treatments. This suggests that the mechanism of negative effects for elevated macroalgal subsidies was development of anoxic conditions promoting sulfide accumulation. Thus, our study was the first to find a critical threshold, or ecological tipping point, beyond which the effects of anthropogenically enhanced subsidies to estuarine mudflat communities switched from positive to negative and to describe the mechanism by which elevated subsides altered the abiotic environment and likely reduced ecosystem functioning.

opencc-zeroDec 2018View details →

Data from: Tree diversity increases robustness of multi-trophic interactions

Multi-trophic interactions maintain critical ecosystem functions. Biodiversity is declining globally, while responses of trophic interactions to biodiversity change are largely unclear. Thus, studying responses of multi-trophic interaction robustness to biodiversity change is crucial for understanding ecosystem functioning and persistence. We investigate plant-Hemiptera- (antagonism) and Hemiptera-ant- (mutualism) interaction networks in response to experimental manipulation of tree diversity. We show increased diversity at both higher trophic levels (Hemiptera and ants) and increased robustness through redundancy of lower level species of multi-trophic interactions when tree diversity increased. Hemiptera and ant diversity increased with tree diversity through non-additive diversity effects. Network analyses identified that tree diversity also increased the number of tree and Hemiptera species utilized by Hemiptera and ant species, and decreased the specialization on lower trophic level species in both mutualistic and antagonist interactions. Our results demonstrate that bottom-up effects of tree diversity ascend through trophic levels regardless of interaction type. Thus, local tree diversity is a key driver of multi-trophic community diversity and interaction robustness in forests.

opencc-zeroFeb 2022View details →

Data from: Partitioning the effects of plant diversity on ecosystem functions at different trophic levels

Biodiversity effects on ecosystem functioning can be partitioned into complementarity effects, driven by many species, and selection effects, driven by few. Selection effects occur through interspecific abundance shifts (dominance) and intraspecific shifts in functioning. Complementarity and selection effects are often calculated for biomass, but very rarely for secondary productivity, i.e. energy transfer to higher trophic levels. We calculated diversity effects for three functions: aboveground biomass, insect herbivory and pathogen infection, the latter two as proxies for energy transfer to higher trophic levels, in a grassland experiment (PaNDiv) manipulating species richness, functional composition, nitrogen enrichment and fungicide treatment. Complementarity effects were on average positive and selection effects negative for biomass production and pathogen infection and multiple species contributed to diversity effects in mixtures. Diversity effects were on average less pronounced for herbivory. Diversity effects for the three functions were not correlated, because different species drove the different diversity effects. Benefits (and costs) from growing in diverse communities, be it reduced herbivore or pathogen damage or increased productivity either due to abundance increases or increased productivity per area were distributed across different plant species, leading to highly variable contributions of single species to diversity effects on different functions. These results show that different underlying ecological mechanisms can result in similar overall diversity effects across functions.

opencc-zeroMar 2022View details →

Data from: Energy and physiological tolerance explain multi-trophic soil diversity in temperate mountains

Aim – Although soil biodiversity is extremely rich and spatially variable, both in terms of species and trophic groups, we still know little about its main drivers. Here, we contrast four long-standing hypotheses to explain the spatial variation of soil multi-trophic diversity: energy, physiological tolerance, habitat heterogeneity, and resource heterogeneity. Location – French Alps Methods – We built on a large-scale observatory across the French Alps (Orchamp) made of seventeen elevational gradients (~90 plots) ranging from low to very high altitude (280 - 3160 m), and encompassing large variations in climate, vegetation and pedological conditions. Biodiversity measurements of 36 soil trophic groups were obtained through environmental DNA metabarcoding. Using a machine learning approach, we assessed 1) the relative importance of predictors linked to different ecological hypotheses in explaining overall multi-trophic soil biodiversity, and 2) the consistency of the response curves across trophic groups. Results – We showed that predictors associated with the four hypotheses had a statistically significant influence on soil multi-trophic diversity, with the strongest support for the energy and physiological tolerance hypotheses. Physiological tolerance explained spatial variation in soil diversity consistently across trophic groups, and was an especially strong predictor for bacteria, protists and microfauna. The effect of energy was more group-specific, with energy input through soil organic matter strongly affecting groups related to the detritus channel. Habitat and resource heterogeneity had overall weaker and more specific impacts on biodiversity with habitat heterogeneity affecting mostly autotrophs, and resource heterogeneity affecting bacterivores, phytophagous insects, enchytraeids and saprotrophic fungi. Main Conclusions – Despite the variability of responses to the environmental drivers found across soil trophic groups, major commonalities on the ecological processes structuring soil biodiversity emerged. We conclude that among the major ecological hypotheses traditionally applied to aboveground organisms, some are particularly relevant to predict the spatial variation in soil biodiversity across the major soil trophic groups.