jenatron-an-experimental-approach-to-study-effects-plant-history-soil

JenaTron - An Experimental Approach to Study the Effects of Plant History and Soil History on Grassland Ecosystem Functioning

The global loss of biodiversity has motivated many studies that experimentally vary plant species richness and examine the consequences for ecosystem ...

German Centre for integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig

Friedrich Schiller University Jena

Global change alters ecological communities with consequences for ecosystem processes. Such processes and functions are a central aspect of ecological research and vital to understanding and mitigating the consequences of global change, but also those of other drivers of change in organism communities. In this context, the concept of energy flux through trophic networks integrates food-web theory and biodiversity-ecosystem functioning theory and connects biodiversity to multitrophic ecosystem functioning. As such, the energy-flux approach is a strikingly effective tool to answer central questions in ecology and global-change research. This might seem straight forward, given that the theoretical background and software to efficiently calculate energy flux are readily available. However, the implementation of such calculations is not always straight forward, especially for those who are new to the topic and not familiar with concepts central to this line of research, such as food-web theory or metabolic theory. To facilitate wider use of energy flux in ecological research, we thus provide a guide to adopting energy-flux calculations for people new to the method, struggling with its implementation, or simply looking for background reading, important resources, and standard solutions to the problems everyone faces when starting to quantify energy fluxes for their community data. First, we introduce energy flux and its use in community and ecosystem ecology. Then, we provide a comprehensive explanation of the single steps towards calculating energy flux for community data. Finally, we discuss remaining challenges and exciting research frontiers for future energy-flux research.

For flux's sake: General considerations for energy-flux calculations in ecological communities.

Anthropogenic global warming has major implications for mobile terrestrial insects, including long-term effects from constant warming, for example, on species distribution patterns, and short-term effects from heat extremes that induce immediate physiological responses. To cope with heat extremes, they either have to reduce their activity or move to preferable microhabitats. The availability of favorable microhabitat conditions is strongly promoted by the spatial heterogeneity of habitats, which is often reduced by anthropogenic land transformation. Thus, it is decisive to understand the combined effects of these global change drivers on insect activity. Here, we assessed the movement activity of six insect species (from three orders) in response to heat stress using a unique tracking approach via radio frequency identification. We tracked 465 individuals at the iDiv Ecotron across a temperature gradient up to 38.7°C. In addition, we varied microhabitat conditions by adding leaf litter from four different tree species to the experimental units, either spatially separated or well mixed. Our results show opposing effects of heat extremes on insect activity depending on the microhabitat conditions. The insect community significantly decreased its activity in the mixed litter scenario, while we found a strong positive effect on activity in the separated litter scenario. We hypothesize that the simultaneous availability of thermal refugia as well as resources provided by the mixed litter scenario allows animals to reduce their activity and save energy in response to heat stress. Contrary, the spatial separation of beneficial microclimatic conditions and resources forces animals to increase their activity to fulfill their energetic needs. Thus, our study highlights the importance of habitat heterogeneity on smaller scales, because it may buffer the consequences of extreme temperatures of insect performance and survival under global change.

Microhabitat conditions remedy heat stress effects on insect activity.

Artificial light at night (ALAN) is predicted to have far-reaching consequences for natural ecosystems given its influence on organismal physiology and behaviour, species interactions and community composition. Movement and predation are fundamental ecological processes that are of critical importance to ecosystem functioning. The natural movements and foraging behaviours of nocturnal invertebrates may be particularly sensitive to the presence of ALAN. However, we still lack evidence of how these processes respond to ALAN within a community context. We assembled insect communities to quantify their movement activity and predation rates during simulated Moon cycles across a gradient of diffuse night-time illuminance including the full range of observed skyglow intensities. Using radio frequency identification, we tracked the movements of insects within a fragmented grassland Ecotron experiment. We additionally quantified predation rates using prey dummies. Our results reveal that even low-intensity skyglow causes a temporal shift in movement activity from day to night, and a spatial shift towards open habitats at night. Changes in movement activity are associated with indirect shifts in predation rates. Spatio-temporal shifts in movement and predation have important implications for ecological networks and ecosystem functioning, highlighting the disruptive potential of ALAN for global biodiversity and the provision of ecosystem services. This article is part of the theme issue 'Light pollution in complex ecological systems'.

Insect communities under skyglow: diffuse night-time illuminance induces spatio-temporal shifts in movement and predation.

Ecosystem functioning depends on biodiversity at multiple trophic levels, yet relationships between multitrophic diversity and ecosystem multifunctionality have been poorly explored, with studies often focusing on individual trophic levels and functions and on specific ecosystem types. Here, we show that plant diversity can affect ecosystem functioning both directly and by affecting other trophic levels. Using data on 13 trophic groups and 13 ecosystem functions from two large biodiversity experiments-one representing temperate grasslands and the other subtropical forests-we found that plant diversity increases multifunctionality through elevated multitrophic diversity. Across both experiments, the association between multitrophic diversity and multifunctionality was stronger than the relationship between the diversity of individual trophic groups and multifunctionality. Our results also suggest that the role of multitrophic diversity is greater in forests than in grasslands. These findings imply that, to promote sustained ecosystem multifunctionality, conservation planning must consider the diversity of both plants and higher trophic levels.

Plant diversity enhances ecosystem multifunctionality via multitrophic diversity.

Climate change and land-use intensification are threatening soil communities and ecosystem functions. Understanding the combined effects of climate change and land use is crucial for predicting future impacts on soil biodiversity and ecosystem functioning in agroecosystems. Here, we used a field experiment to quantify the combined effects of climate change (warming and altered precipitation patterns) and land use (agricultural type and management intensity) on soil food webs across nematodes, micro-, and macroarthropods. Specifically, we investigated two types of agricultural systems-croplands and grasslands-under both high- and low-intensity management. We focused on assessing the functioning of soil food webs by investigating changes in energy flux to consumers in the main trophic groups: decomposers, microbivores, herbivores, and predators. While the total energy flux and detritivory, herbivory and predation in the soil food web remained unchanged across treatments, low-intensity land use-compared to high intensity-led to higher microbivory and microbial control under future climate conditions (i.e., warming and summer drought) in croplands and grasslands. At the same time, microbial and herbivore control were higher under low-intensity land use in croplands and grasslands. Overall, our results underscore the potential benefits of less intensive, more sustainable management practices for soil food-web functioning under current and future climate scenarios.

Sustainable Land Use Strengthens Microbial and Herbivore Controls in Soil Food Webs in Current and Future Climates.

Biodiversity experiments revealed that plant diversity loss can decrease ecosystem functions across trophic levels. To address why such biodiversity-function relationships strengthen over time, we established experimental mesocosms replicating a gradient in plant species richness across treatments of shared versus non-shared history of (1) the plant community and (2) the soil fauna community. After 4 months, we assessed the multitrophic functioning of soil fauna via biomass stocks and energy fluxes across the food webs. We find that soil community history significantly enhanced belowground multitrophic function via changes in biomass stocks and community-average body masses across the food webs. However, variation in plant diversity and plant community history had unclear effects. Our findings underscore the importance of long-term community assembly processes for soil fauna-driven ecosystem function, with species richness and short-term plant adaptations playing a minimal role. Disturbances that disrupt soil community stability may hinder fauna-driven ecosystem functions, while recovery may require several years.

Soil community history strengthens belowground multitrophic functioning across plant diversity levels in a grassland experiment.

Trait-based approaches have been increasingly used to relate plants to soil microbial communities. Using the recently described root economics space as an approach to explain the structure of soil-borne fungal communities, our study in a grassland diversity experiment reveals distinct root trait strategies at the plant community level. In addition to significant effects of plant species richness, we show that the collaboration and conservation gradient are strong drivers of the composition of the different guilds of soil fungi. Saprotrophic fungi are most diverse in species-rich plant communities with 'slow' root traits, whereas plant pathogenic fungi are most diverse and abundant in communities with 'fast' and 'DIY' root traits. Fungal biomass is strongly driven by plant species richness. Our results illustrate that the root economics space and plant species richness jointly determine the effects of plants on soil fungal communities and their potential role in plant fitness and ecosystem functioning.

Plant Species Richness and the Root Economics Space Drive Soil Fungal Communities.

The relationship of plant diversity and several ecosystem functions strengthens over time. This suggests that the restructuring of biotic interactions in the process of a community's assembly and the associated changes in function differ between species-rich and species-poor communities. An important component of these changes is the feedback between plant and soil community history. In this study, we examined the interactive effects of plant richness and community history on the trophic functions of the soil fauna community. We hypothesized that experimental removal of either soil or plant community history would diminish the positive effects of plant richness on the multitrophic functions of the soil food web, compared to mature communities. We tested this hypothesis in a long-term grassland biodiversity experiment by comparing plots across three treatments (without plant history, without plant and soil history, controls with ~20 years of plot-specific community history). We found that the relationship between plant richness and below-ground multitrophic functionality is indeed stronger in communities with shared plant and soil community history. Our findings indicate that anthropogenic disturbance can impact the functioning of the soil community through the loss of plant species but also by preventing feedbacks that develop in the process of community assembly.

Article	Year
For flux's sake: General considerations for energy-flux calculations in ecological communities. Ecology and evolution\| PubMed ID: 34646445	2021
Microhabitat conditions remedy heat stress effects on insect activity. Global change biology\| PubMed ID: 37186484	2023
Insect communities under skyglow: diffuse night-time illuminance induces spatio-temporal shifts in movement and predation. Philosophical transactions of the Royal Society of London. Series B, Biological sciences\| PubMed ID: 37899019	2023
Plant diversity enhances ecosystem multifunctionality via multitrophic diversity. Nature ecology & evolution\| PubMed ID: 39209981	2024
Sustainable Land Use Strengthens Microbial and Herbivore Controls in Soil Food Webs in Current and Future Climates. Global change biology\| PubMed ID: 39545329	2024
Soil community history strengthens belowground multitrophic functioning across plant diversity levels in a grassland experiment. Nature communications\| PubMed ID: 39562617	2024
Plant Species Richness and the Root Economics Space Drive Soil Fungal Communities. Ecology letters\| PubMed ID: 39737799	2025
Shared community history strengthens plant diversity effects on below-ground multitrophic functioning. The Journal of animal ecology\| PubMed ID: 39887967	2025

Angelos Amyntas

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