Showing papers in "Advances in Ecological Research in 2019"

A multitrophic perspective on biodiversity-ecosystem functioning research

Abstract: Concern about the functional consequences of unprecedented loss in biodiversity has prompted biodiversity–ecosystem functioning (BEF) research to become one of the most active fields of ecological research in the past 25 years. Hundreds of experiments have manipulated biodiversity as an independent variable and found compelling support that the functioning of ecosystems increases with the diversity of their ecological communities. This research has also identified some of the mechanisms underlying BEF relationships, some context-dependencies of the strength of relationships, as well as implications for various ecosystem services that humankind depends upon. In this chapter, we argue that a multitrophic perspective of biotic interactions in random and non-random biodiversity change scenarios is key to advance future BEF research and to address some of its most important remaining challenges. We discuss that the study and the quantification of multitrophic interactions in space and time facilitates scaling up from small-scale biodiversity manipulations and ecosystem function assessments to management-relevant spatial scales across ecosystem boundaries. We specifically consider multitrophic conceptual frameworks to understand and predict the context-dependency of BEF relationships. Moreover, we highlight the importance of the eco-evolutionary underpinnings of multitrophic BEF relationships. We outline that FAIR data (meeting the standards of findability, accessibility, interoperability, and reusability) and reproducible processing will be key to advance this field of research by making it more integrative. Finally, we show how these BEF insights may be implemented for ecosystem management, society, and policy. Given that human well-being critically depends on the multiple services provided by diverse, multitrophic communities, integrating the approaches of evolutionary ecology, community ecology, and ecosystem ecology in future BEF research will be key to refine conservation targets and develop sustainable management strategies.

Transferring biodiversity-ecosystem function research to the management of ‘real-world’ ecosystems

Abstract: Biodiversity-ecosystem functioning (BEF) research grew rapidly following concerns that biodiversity loss would negatively affect ecosystem functions and the ecosystem services they underpin. However, despite evidence that biodiversity strongly affects ecosystem functioning, the influence of BEF research upon policy and the management of ‘real-world’ ecosystems, i.e., semi-natural habitats and agroecosystems, has been limited. Here, we address this issue by classifying BEF research into three clusters based on the degree of human control over species composition and the spatial scale, in terms of grain, of the study, and discussing how the research of each cluster is best suited to inform particular fields of ecosystem management. Research in the first cluster, small-grain highly controlled studies, is best able to provide general insights into mechanisms and to inform the management of species-poor and highly managed systems such as croplands, plantations, and the restoration of heavily degraded ecosystems. Research from the second cluster, small-grain observational studies, and species removal and addition studies, may allow for direct predictions of the impacts of species loss in specific semi-natural ecosystems. Research in the third cluster, large-grain uncontrolled studies, may best inform landscape-scale management and national-scale policy. We discuss barriers to transfer within each cluster and suggest how new research and knowledge exchange mechanisms may overcome these challenges. To meet the potential for BEF research to address global challenges, we recommend transdisciplinary research that goes beyond these current clusters and considers the social-ecological context of the ecosystems in which BEF knowledge is generated. This requires recognizing the social and economic value of biodiversity for ecosystem services at scales, and in units, that matter to land managers and policy makers.

Adaptive capacity in ecosystems

Abstract: Understanding the capacity of ecosystems to adapt and to cope (i.e. adaptive capacity) with change is crucial to their management. However, definitions of adaptive capacity are often unclear and confusing, making application of this concept difficult. In this paper, we revisit definitions of adaptive capacity and operationalize the concept. We define adaptive capacity as the latent potential of an ecosystem to alter resilience in response to change. We present testable hypotheses to evaluate complementary attributes of adaptive capacity that may help further clarify the components and relevance of the concept. We suggest how sampling, inference and modelling can reduce key uncertainties incrementally over time and increase learning about adaptive capacity. Improved quantitative assessments of adaptive capacity are needed because of the high uncertainty about global change and its potential effect on the capacity of ecosystems to adapt to social and ecological change. An improved understanding of adaptive capacity might ultimately allow for more efficient and targeted management.

Chapter One - A multitrophic perspective on biodiversity–ecosystem functioning research

Abstract: Concern about the functional consequences of unprecedented loss in biodiversity has prompted biodiversity-ecosystem functioning (BEF) research to become one of the most active fields of ecological research in the past 25 years. Hundreds of experiments have manipulated biodiversity as an independent variable and found compelling support that the functioning of ecosystems increases with the diversity of their ecological communities. This research has also identified some of the mechanisms underlying BEF relationships, some context-dependencies of the strength of relationships, as well as implications for various ecosystem services that mankind depends upon. In this paper, we argue that a multitrophic perspective of biotic interactions in random and non-random biodiversity change scenarios is key to advance future BEF research and to address some of its most important remaining challenges. We discuss that the study and the quantification of multitrophic interactions in space and time facilitates scaling up from small-scale biodiversity manipulations and ecosystem function assessments to management-relevant spatial scales across ecosystem boundaries. We specifically consider multitrophic conceptual frameworks to understand and predict the context-dependency of BEF relationships. Moreover, we highlight the importance of the eco-evolutionary underpinnings of multitrophic BEF relationships. We outline that FAIR data (meeting the standards of findability, accessibility, interoperability, and reusability) and reproducible processing will be key to advance this field of research by making it more integrative. Finally, we show how these BEF insights may be implemented for ecosystem management, society, and policy. Given that human well-being critically depends on the multiple services provided by diverse, multitrophic communities, integrating the approaches of evolutionary ecology, community ecology, and ecosystem ecology in future BEF research will be key to refine conservation targets and develop sustainable management strategies.

How plant diversity impacts the coupled water, nutrient and carbon cycles

Abstract: Soils are important for ecosystem functions and services. However, soil processes are complex and changes of solid phase soil properties, such as soil organic matter contents are slow. As a consequence, a comprehensive understanding of the role of soil in the biodiversity-ecosystem functioning (BEF) relationship is still lacking. Thus, long-term observations and experiments are needed in biodiversity research in order to better understand how biodiversity influences soil properties and thus the BEF relationships. To elucidate the integrated response of soil-related functions and processes to plant diversity, we reviewed literature on the water, nutrient and carbon cycles in biodiversity research with specific focus on the Jena Experiment. Furthermore, we took advantage of the long-term observations of water, nutrient and carbon dynamics gathered in the Jena Experiment to investigate changes of the plant diversity effect over time on theses cycles and the accompanying plant-microbial interactions. We found that soil organic carbon and soil nitrogen stocks in the top 15 cm constantly increased over time and that this increase was positively related to plant species richness. In contrast, the concentrations of the quantitatively most important nutrient ions nitrate and phosphate in soil solution decreased with time, likely because of the ongoing removal of nutrients by plant biomass harvest. We furthermore observed a shift in the microbial community composition, which was triggered by an increased availability of plant-derived carbon at higher plant species richness over time, suggesting that plant communities compensated for nutrient losses by stimulating the microbial nutrient cycling. In addition, water including dissolved nutrients and carbon percolated deeper in plots of higher plant diversity. Thereby, higher plant diversity spatially extended the nutrient cycling through the microbial communities to deeper soil layers from which nutrients are transferred to the topsoil by deep-rooting plants. Although microbial nutrient cycling cannot fully compensate for negative plant diversity effects on nutrient availability in soil solution, this suggests that over time the role of plant-derived inputs becomes increasingly important for ecosystem functioning. It furthermore implies that plant species richness tightens plant-microbial interactions, which in the long-term feed back on other ecosystem functions, such as productivity.

Extensive grassland-use sustains high levels of soil biological activity, but does not alleviate detrimental climate change effects

Abstract: Climate change and intensified land use simultaneously affect the magnitude and resilience of soil-derived ecosystem functions, such as nutrient cycling and decomposition. Thus far, the responses of soil organisms to interacting global change drivers remain poorly explored and our knowledge of below-ground phenology is particularly limited. Previous studies suggest that extensive land-use management has the potential to buffer detrimental climate change impacts, via biodiversity-mediated effects. According to the insurance hypothesis of biodiversity, a higher biodiversity of soil communities and thus an elevated response diversity to climate change would facilitate a more stable provisioning of ecosystem functions under environmental stress. Here we present results of a two-year study investigating, at fine temporal resolution, the effects of predicted climate change scenarios (altered precipitation patterns; passive warming) on three grassland types, differing in land-use intensity, soil biological activity, and in resilience. We show that future climate conditions consistently reduced soil biological activity, revealing an overall negative effect of predicted climate change. Furthermore, future climate caused earlier and significantly lower peaks of biological activity in the soil. Land-use intensity also significantly decreased soil biological activity, but contrary to general expectations, extensive land use did not alleviate the detrimental effects of simulated climate change. Instead, the greatest reduction in soil biological activity was observed in extensively-used grasslands, highlighting their potential vulnerability to predicted climate change. To assure high levels of biological activity in resilient agroecosystems, extensive land use needs to be complemented by other management approaches, such as the adoption of specific plant species compositions that secure ecosystem functioning in a changing world.

A new experimental approach to test why biodiversity effects strengthen as ecosystems age

Abstract: Previous experimental studies found strengthening relationships between biodiversity and ecosystem functioning (BEF) over time. Simultaneous temporal changes of abiotic and biotic conditions, such as in the composition of soil communities, soil carbon and nutrient concentrations, plant community assembly or selection processes, are currently discussed as potential drivers for strengthening BEF relationships. Despite the popularity of these explanations, experimental tests of underlying mechanisms of strengthening BEF relationships over time are scarce, and confounding influences of calendar year cannot be ruled out unless ecosystems of different age are compared in the same calendar years. To address this critical gap of knowledge, we reestablished the plant communities of a long-term biodiversity experiment that had started in 2002 (the Jena Experiment) with new seeds and old or new soil again in 2016. Comparing these treatments with the original communities set up in 2002, we tested whether old communities had stronger plant diversity effects on plant productivity than young ones and if this depended on soil- or plant-related processes. Our first results show that in old communities, the effect of plant diversity on productivity was indeed stronger than in young communities and that this could not be explained by the age of the soil only. However, we found significant effects of soil on the composition of soil organisms, which might be relevant for other ecosystem functions and may have stronger effects over time. Our new experimental approach enables us to test which mechanisms cause strengthening BEF relationships for many different ecosystem functions independent of the study year.

Above- and belowground overyielding are related at the community and species level in a grassland biodiversity experiment

Abstract: Plant species richness positively affects plant productivity both above- and belowground. While this suggests that they are related at the community level, few studies have calculated above- and belowground overyielding simultaneously. It thus remains unknown whether above- and belowground overyielding are correlated. Moreover, it is unknown how belowground community level overyielding translates to the species level. We investigated above- and belowground overyielding in the Jena Trait-Based Biodiversity Experiment, at both the community and species level and across two 8-species pools. We found that above- and belowground overyielding were positively correlated at the community level and at the species level—for seven out of the 13 investigated species. Some plant species performed better in mixtures compared to monocultures and others performed worse, but the majority did so simultaneously above- and belowground. However, plants invested more in aboveground overyielding than belowground. Based on this disproportional investment in overyielding aboveground, we conclude that light was more limiting than belowground resources in the present study, which requires individual species to compete more for light than for belowground resources.

Plant functional trait identity and diversity effects on soil meso- and macrofauna in an experimental grassland

Abstract: Understanding aboveground-belowground linkages and their consequences for ecosystem functioning is a major challenge in soil ecology. It is already well established that soil communities drive essential ecosystem processes, such as nutrient cycling, decomposition, or carbon storage. However, knowledge of how plant diversity affects belowground community structure is limited. Such knowledge can be gained from studying the main plant functional traits that modulate plant community effects on soil fauna. Here, we used a grassland experiment manipulating plant species richness and plant functional diversity to explore the effects of community-level plant traits on soil meso- and macrofauna and the trophic structure of soil fauna by differentiating predators and prey. The functional composition of plant communities was described by six plant traits related to spatial and temporal resource use: plant height, leaf area, rooting depth, root length density, growth start, and flowering start. Community-Weighted Means (CWMs), Functional Dissimilarity (FDis), and Functional Richness (FRic) were calculated for each trait. Community-level plant traits better explained variability in soil fauna than did plant species richness. Notably, each soil fauna group was affected by a unique set of plant traits. Moreover, the identity of plant traits (CWM) explained more variance of soil fauna groups than trait diversity. The abundances of soil fauna at the lower trophic levels were better explained by community-level plant traits than higher trophic levels soil fauna groups. Taken together, our results highlight the importance of the identity of different plant functional traits in driving the diversity and trophic structure of soil food communities.

Linking local species coexistence to ecosystem functioning: a conceptual framework from ecological first principles in grassland ecosystems

Abstract: One of the unifying goals of ecology is understanding the mechanisms that drive ecological patterns. For any particular observed pattern, ecologists have proposed varied mechanistic models. However, in spite of their differences, all of these mechanistic models rely on either abiotic conditions or biotic conditions, our “ecological first principles”. These major components underlie all of the major mechanistic explanations for patterns of diversity like the latitudinal gradient in diversity, the maintenance of diversity, and the (often positive) biodiversity-ecosystem functioning relationship. These components and their interactions alter the dynamics of plant populations, which ultimately determine local coexistence at the community level, and functioning at the ecosystem level. We present a review, starting from ecological first principles of the ways in which ecosystem functioning may be linked to local coexistence in plant communities via mutual effects on and reactions to the abiotic and biotic conditions in which they are imbedded.

Modelling land use dynamics in socio-ecological systems: A case study in the UK uplands

Abstract: It is well-recognised that to achieve long-term sustainable and resilient land management we need to understand the coupled dynamics of social and ecological systems. Land use change scenarios will often aim to understand (i) the behaviours of land management, influenced by direct and indirect drivers, (ii) the resulting changes in land use and (iii) the environmental implications of these changes. While the literature in this field is extensive, approaches to parameterise coupled systems through integration of empirical social science based models and ecology based models still need further development. We propose an approach to land use dynamics modelling based on the integration of behavioural models derived from choice experiments and spatially explicit systems dynamics modelling. This involves the specification of a choice model to parameterise land use behaviour and the integration with a spatial habitat succession model. We test this approach in an upland socio-ecological system in the United Kingdom. We conduct a choice experiment with land managers in the Peak District National Park. The elicited preferences form the basis for a behavioural model, which is integrated with a habitat succession model to predict the landscape level vegetation impacts. The integrated model allows us to create projections of how land use may change in the future under different environmental and policy scenarios, and the impact this may have on landscape vegetation patterns. We illustrate this by showing future projection of landscape changes related to hypothetical changes to EU level agricultural management incentives. The advantages of this approach are (i) the approach takes into account potential environmental and management feedbacks, an aspect often ignored in choice modelling, (ii) the behavioural rules are revealed from actual and hypothetical choice data, which allow the research to test the empirical evidence for various determinants of choice, (iii) the behavioural choice models generate probabilities of alternative behaviours which make them ideally suited for integration with simulation models. The paper concludes that the modelling approach offers a promising route for linking socio-economic and ecological features of socio-ecological systems. Furthermore, our proposed approach allows testing of the underlying socio-economic and environmental drivers and their interaction in real environmental systems.

Employing an ecosystem services framework to deliver decision ready science

Abstract: Public land managers have limited information to allow for integration and balancing of multiple objectives in land management decisions including the social (cultural and health), economic (monetary and nonmonetary), and environmental aspects. In this article, we document an approach to consider the many facets of decision making by incorporating them into a decision context using an ecosystem services framework. This analysis is based on a multi-partner project led by the US Geological Survey and the US Fish and Wildlife Service to provide land management decision support for the Great Dismal Swamp National Wildlife Refuge. It is an integrated ecologic-economic analysis of baseline (current) and potential future quantities, qualities, and values of selected ecosystem services in the refuge. Alternative management scenarios are modeled to consider the impact of specific management actions or natural disturbances on priority ecosystem services. We examine the benefits and challenges of using this framework. Key lessons learned from this effort include the mismatch in timing between physical and social science; the challenge of integrating methods from multiple disciplines; the importance of frequent communication to overcome siloed research; and the utility of an integrating framework such as ecosystem services and supporting tools such as the dynamic ecosystem model.