Analysis of complex trophic networks reveals the signature of land-use intensification on soil communities in agroecosystems

Increasing evidence suggests that agricultural intensification is a threat to many groups of soil biota, but how the impacts of land-use intensity on soil organisms translate into changes in comprehensive soil interaction networks remains unclear. Here for the first time, we use environmental DNA to examine total soil multi-trophic diversity and food web structure for temperate agroecosystems along a gradient of land-use intensity. We tested for response patterns in key properties of the soil food webs in sixteen fields ranging from arable crops to grazed permanent grasslands as part of a long-term management experiment. We found that agricultural intensification drives reductions in trophic group diversity, although taxa richness remained unchanged. Intensification generally reduced the complexity and connectance of soil interaction networks and induced consistent changes in energy pathways, but the magnitude of management-induced changes depended on the variable considered. Average path length (an indicator of food web redundancy and resilience) did not respond to our management intensity gradient. Moreover, turnover of network structure showed little response to increasing management intensity. Our data demonstrates the importance of considering different facets of trophic networks for a clearer understanding of agriculture-biodiversity relationships, with implications for nature-based solutions and sustainable agriculture

How plot shape and spatial arrangement affect plant species richness counts: implications for sampling design and rarefaction analyses

Questions: How does the spatial configuration of sampling units influence recorded plant species richness values at small spatial scales? What are the consequences of these findings for sampling methodology and rarefaction analyses?. Location: Six semi-natural grasslands in Western Eurasia (France, Germany, Bulgaria, Hungary, Italy, Turkey). Methods: In each site we established six blocks of 40 cm × 280 cm, subdivided into 5 cm × 5 cm micro-quadrats, on which we recorded vascular plant species presence with the rooted (all sites) and shoot (four sites) presence method. Data of these micro-quadrats were then combined to achieve larger sampling units of 0.01, 0.04 and 0.16 m² grain size with six different spatial configurations (square, 4:1 rectangle, 16:1 rectangle, three variants of discontiguous randomly placed micro-quadrats). The effect of the spatial configurations on species richness was quantified as relative richness compared to the mean richness of the square of the same surface area. Results: Square sampling units had significantly lower species richness than other spatial configurations in all countries. For 4:1 and 16:1 rectangles, the increase of rooted richness was on average about 2% and 8%, respectively. In contrast, the average richness increase for discontiguous configurations was 7%, 17% and 40%. In general, increases were higher with shoot presence than with rooted presence. Overall, the patterns of richness increase were highly consistent across six countries, three grain sizes and two recording methods. Conclusions: Our findings suggest that the shape of sampling units has negligible effects on species richness values when the length–width ratio is up to 4:1, and the effects remain small even for more elongated contiguous configurations. In contrast, results from discontiguous sampling units are not directly comparable with those of contiguous sampling units, and are strongly confounded by spatial extent. This is particularly problematic for rarefaction studies where spatial extent is often not controlled for. We suggest that the concept of effective area is a useful tool to report effects of spatial configuration on richness values, and introduce species–extent relationships (SERs) to describe richness increases of different spatial configurations of sampling units. © 2016 International Association for Vegetation Scienc

Global change effects on plant communities are magnified by time and the number of global change factors imposed

Global change drivers (GCDs) are expected to alter community structure and consequently, the services that ecosystems provide. Yet, few experimental investigations have examined effects of GCDs on plant community structure across multiple ecosystem types, and those that do exist present conflicting patterns. In an unprecedented global synthesis of over 100 experiments that manipulated factors linked to GCDs, we show that herbaceous plant community responses depend on experimental manipulation length and number of factors manipulated. We found that plant communities are fairly resistant to experimentally manipulated GCDs in the short term (<10 y). In contrast, long-term (≥10 y) experiments show increasing community divergence of treatments from control conditions. Surprisingly, these community responses occurred with similar frequency across the GCD types manipulated in our database. However, community responses were more common when 3 or more GCDs were simultaneously manipulated, suggesting the emergence of additive or synergistic effects of multiple drivers, particularly over long time periods. In half of the cases, GCD manipulations caused a difference in community composition without a corresponding species richness difference, indicating that species reordering or replacement is an important mechanism of community responses to GCDs and should be given greater consideration when examining consequences of GCDs for the biodiversity–ecosystem function relationship. Human activities are currently driving unparalleled global changes worldwide. Our analyses provide the most comprehensive evidence to date that these human activities may have widespread impacts on plant community composition globally, which will increase in frequency over time and be greater in areas where communities face multiple GCDs simultaneously

Eighteen years of upland grassland carbon flux data: reference datasets, processing, and gap-filling procedure

Abstract Plant-atmosphere exchange fluxes of CO2 measured with the Eddy covariance method are used extensively for the assessment of ecosystem carbon budgets worldwide. The present paper describes eddy flux measurements for a managed upland grassland in Central France studied over two decades (2003–2021). We present the site meteorological data for this measurement period, and we describe the pre-processing and post-processing approaches used to overcome issues of data gaps, commonly associated with long-term EC datasets. Recent progress in eddy flux technology and machine learning now paves the way to produce robust long-term datasets, based on normalised data processing techniques, but such reference datasets remain rare for grasslands. Here, we combined two gap-filling techniques, Marginal Distribution Sampling (short gaps) and Random Forest (long gaps), to complete two reference flux datasets at the half-hour and daily-scales respectively. The resulting datasets are valuable for assessing the response of grassland ecosystems to (past) climate change, but also for model evaluation and validation with respect to future global change research with the carbon-cycle community

Appendix 1. PRISMA work flow dragram;Appendix 2. Literature list;Appendix 3. Dataset for meta-analysis;Appendix 4. Meta-analysis of other covariates;Appendix 5. Publication bias from Species richness alters spatial nutrient heterogeneity effects on above-ground plant biomass

to show how studies were searched and selected;A list of literature selected for meta-analysis;Dataset extracted for the meta-analysis;meta-analysis for other covariates ;details on analysis of publication bia

Data from: Patterns and drivers of biodiversity-stability relationships under climate extremes

Interactions between biodiversity loss and climate change present significant challenges for research, policy and management of ecosystems. Evidence suggests that high species diversity tends to increase plant community stability under interannual climate fluctuations and mild dry and wet events, but the overall pattern of diversity–stability relationships under climate extremes is unclear. We comprehensively review results from observational and experimental studies to assess the importance of diversity effects for ecosystem function under climate extremes. Both the broad literature review and a meta-analysis focused on the effects of extreme precipitation events on above-ground biomass reveal no significant interaction between species richness and climate extremes. Causes for variation in diversity effects under climate extremes are explored, from stress thresholds to biotic interactions and community assembly, and we consider how these may modulate the outcomes of biodiversity–stability relationships. We also examine how specific characteristics of climate extremes and timing of measurements may interact with mechanisms of diversity–stability relationships. Synthesis. Hypotheses tailored to the complexity of diversity effects, the implementation of standardised experiments and the use of trait-based biodiversity measures rather than species richness should lead to better causal understanding of whether and how biodiversity may protect ecosystems from adverse effects of climate extremes

Patterns and drivers of biodiversity–stability relationships under climate extremes

Interactions between biodiversity loss and climate change present significant challenges for research, policy and management of ecosystems. Evidence suggests that high species diversity tends to increase plant community stability under interannual climate fluctuations and mild dry and wet events, but the overall pattern of diversity–stability relationships under climate extremes is unclear. We comprehensively review results from observational and experimental studies to assess the importance of diversity effects for ecosystem function under climate extremes. Both the broad literature review and a meta-analysis focused on the effects of extreme precipitation events on above-ground biomass reveal no significant interaction between species richness and climate extremes. Causes for variation in diversity effects under climate extremes are explored, from stress thresholds to biotic interactions and community assembly, and we consider how these may modulate the outcomes of biodiversity–stability relationships. We also examine how specific characteristics of climate extremes and timing of measurements may interact with mechanisms of diversity–stability relationships. Synthesis. Hypotheses tailored to the complexity of diversity effects, the implementation of standardised experiments and the use of trait-based biodiversity measures rather than species richness should lead to better causal understanding of whether and how biodiversity may protect ecosystems from adverse effects of climate extremes