Jes Hines

Operationalizing Network Theory for Ecosystem Service Assessments

Managing ecosystems to provide ecosystem services in the face of global change is a pressing challenge for policy and science. Predicting how alternative management actions and changing future conditions will alter services is complicated by interactions among components in ecological and socioeconomic systems. Failure to understand those interactions can lead to detrimental outcomes from management decisions. Network theory that integrates ecological and socioeconomic systems may provide a path to meeting this challenge. While network theory offers promising approaches to examine ecosystem services, few studies have identified how to operationalize networks for managing and assessing diverse ecosystem services. We propose a framework for how to use networks to assess how drivers and management actions will directly and indirectly alter ecosystem services.

fluxweb: a R package to easily estimate energy fluxes in food webs

Understanding how changes in biodiversity will impact the stability and functioning of ecosystems is a central challenge in ecology. Food-web approaches have been advocated to link community composition with ecosystem functioning by describing the fluxes of energy among species or trophic groups. However, estimating such fluxes remains problematic because current methods become unmanageable as network complexity increases. We developed a generalisation of previous indirect estimation methods assuming a steady state system [1, 2, 3]: the model estimates energy fluxes in a top-down manner assuming system equilibrium; each node’s losses (consumption and physiological) balances its consumptive gains. Jointly, we provide theoretical and practical guidelines to use the fluxweb R package (available on CRAN at https://bit.ly/2OC0uKF). We also present how the framework can merge with the allometric theory of ecology [4] to calculate fluxes based on easily obtainable organism-level data (i.e. body masses and species groups -eg, plants animals), opening its use to food webs of all complexities. Physiological losses (metabolic losses or losses due to death other than from predation within the food web) may be directly measured or estimated using allometric relationships based on the metabolic theory of ecology, and losses and gains due to predation are a function of ecological efficiencies that describe the proportion of energy that is used for biomass production. The primary output is a matrix of fluxes among the nodes of the food web. These fluxes can be used to describe the role of a species, a function of interest (e.g. predation; total fluxes to predators), multiple functions, or total energy flux (system throughflow or multitrophic functioning). Additionally, the package includes functions to calculate network stability based on the Jacobian matrix, providing insight into how resilient the network is to small perturbations at steady state. Overall, fluxweb provides a flexible set of functions that greatly increase the feasibility of implementing food-web energetic approaches to more complex systems. As such, the package facilitates novel opportunities for mechanistically linking quantitative food webs and ecosystem functioning in real and dynamic natural landscapes.

Mycorrhiza in tree diversity–ecosystem function relationships: conceptual framework and experimental implementation

The widely observed positive relationship between plant diversity and ecosystem functioning is thought to be substantially driven by complementary resource use of plant species. Recent work suggests that biotic interactions among plants and between plants and soil organisms drive key aspects of resource use complementarity. Here, we provide a conceptual framework for integrating positive biotic interactions across guilds of organisms, more specifically between plants and mycorrhizal types, to explain resource use complementarity in plants and its consequences for plant competition. Our overarching hypothesis is that ecosystem functioning increases when more plant species associate with functionally dissimilar mycorrhizal fungi because differing mycorrhizal types will increase coverage of habitat space for and reduce competition among plants. We introduce a recently established field experiment (MyDiv) that uses different pools of tree species that associate with either arbuscular or ectomycorrhizal fungi to create orthogonal experimental gradients in tree species richness and mycorrhizal associations and present initial results. Finally, we discuss options for future mechanistic studies on resource use complementarity within MyDiv. We show how mycorrhizal types and biotic interactions in MyDiv can be used in the future to test novel questions regarding the mechanisms underlying biodiversity–ecosystem function relationships.

The geography of the Anthropocene differs between the land and the sea

Climate change and other anthropogenic drivers of biodiversity change are unequally distributed across the world. Despite the implications for biodiversity change, it is unknown if the geographic patterns of drivers differ between the terrestrial and marine realm. Using global datasets on human population density, land and resource exploitation, pollution, species invasions, and climate change, we found stronger positive correlations among drivers in the terrestrial than in the marine realm, leading to areas of especially intense human impact on land. Climate change tended to be negatively correlated with other drivers in the terrestrial realm whereas the opposite was true in the marine realm. We show that different regions of the world are exposed to distinct ‘anthropogenic threat complexes’, comprising suites of drivers of varying intensities. Our global analysis highlights the broad conservation priorities needed to mitigate the drivers shaping biodiversity responses to anthropogenic change.

The Dark Side of Animal Phenology

Research exploring the timing of recurring biological events has shown that anthropogenic climate change dramatically alters the phenology of many plants and animals. However, we still lack studies on how climate change might alter the phenology of soil invertebrates as well as how this can subsequently affect ecosystem functions.

Global gaps in soil biodiversity data

To the Editor — Soil biodiversity represents a major terrestrial biodiversity pool, supports key ecosystem services and is under pressure from human activities1. Yet soil biodiversity has been neglected from many global biodiversity assessments and policies. This omission is undoubtedly related to the paucity of comprehensive information on soil biodiversity, particularly on larger spatial scales. Information on belowground species distributions, population trends, endemism and threats to belowground diversity is important for conservation prioritization, but is practically non-existent. As a consequence, much of our understanding of global macroecological patterns in biodiversity, as well as mapping of global biodiversity hotspots, has been based on aboveground taxa (such as plants2) and has not considered the functionally vital, but less visible, biodiversity found in soil. We mapped the study sites from existing global datasets on soil biodiversity (soil macrofauna3, fungi4 and bacteria5) to examine key data gaps (Fig. 1). Our map indicates significant gaps in soil biodiversity data across northern latitudes, including most of Russia and Canada. Data are also lacking from much of central Asia and central Africa (for example, the Sahara Desert), as well as many tropical regions. The higher density of soil biodiversity sampling sites in Europe and the United States is similar to patterns observed for data on terrestrial bird, mammal and amphibian species6, as well as plants7. Yet, in such aboveground datasets, the gaps in understudied regions are much less pronounced than in the soil biodiversity datasets shown here. The comparative lack of soil biodiversity data across these regions limits our ability to examine global macroecological patterns and to quantify potential mismatches between aboveground and soil biodiversity. The potential for such mismatches (areas with high aboveground diversity, but low soil biodiversity, or vice versa) may be substantial, as evidence suggests that plant species richness declines more rapidly towards the North Pole than fungal species richness, which reaches a plateau4. Soil ecologists are increasingly conducting their own large-scale assessments (such as the African Soil Microbiology Project8) and additional databases on soil biodiversity are beginning to be developed9, in part through the Global Soil Biodiversity Initiative. However, increased efforts to fill these gaps and to compile additional global datasets on other soil taxa (for example, mesofauna) are needed to allow more detailed analyses of soil biodiversity on broad spatial scales. Of major concern is the lack of a global consensus on sampling strategies and methodological approaches to assess soil biodiversity, which in many cases makes it challenging to compare datasets directly. Furthermore, greater cooperation with conservation biologists and policymakers is needed to better integrate soil biodiversity into global policies. For instance, soil biodiversity should be more explicitly considered in the post-2020 global biodiversity framework10 that will follow the Strategic Plan for Biodiversity 2011–2020 and in future assessments of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services11. These evident gaps in soil biodiversity data restrict our ability to develop policies to protect soil biodiversity. We argue that addressing these data gaps will ultimately benefit human well-being1 and provide an impetus for increased policy-relevant research on soil biodiversity. ❐

Multiple facets of biodiversity drive the diversity–stability relationship

A substantial body of evidence has demonstrated that biodiversity stabilizes ecosystem functioning over time in grassland ecosystems. However, the relative importance of different facets of biodiversity underlying the diversity–stability relationship remains unclear. Here we use data from 39 grassland biodiversity experiments and structural equation modelling to investigate the roles of species richness, phylogenetic diversity and both the diversity and community-weighted mean of functional traits representing the ‘fast–slow’ leaf economics spectrum in driving the diversity–stability relationship. We found that high species richness and phylogenetic diversity stabilize biomass production via enhanced asynchrony in the performance of co-occurring species. Contrary to expectations, low phylogenetic diversity enhances ecosystem stability directly, albeit weakly. While the diversity of fast–slow functional traits has a weak effect on ecosystem stability, communities dominated by slow species enhance ecosystem stability by increasing mean biomass production relative to the standard deviation of biomass over time. Our in-depth, integrative assessment of factors influencing the diversity–stability relationship demonstrates a more multicausal relationship than has been previously acknowledged.Analysing data from 39 grassland biodiversity experiments, the authors uncover the direct and indirect contributions to ecosystem stability of taxonomic, phylogenetic and functional trait diversity.