Anthropogenic global change alters the activity and functional composition of soil communities that are responsible for crucial ecosystem functions and services. Two of the most pervasive global change drivers are drought and nutrient enrichment. However, the responses of soil organisms to interacting global change drivers remain widely unknown. We tested the interactive effects of extreme drought and fertilization on soil biota ranging from microbes to invertebrates across seasons. We expected drought to reduce the activity of soil organisms and fertilization to induce positive bottom-up effects via increased plant productivity. Furthermore, we hypothesized fertilization to reinforce drought effects through enhanced plant growth, resulting in even drier soil conditions. Our results revealed that drought had detrimental effects on soil invertebrate feeding activity and simplified nematode community structure, whereas soil microbial activity and biomass were unaffected. Microbial biomass increased in response to fertilization, whereas invertebrate feeding activity substantially declined. Notably, these effects were consistent across seasons. The dissimilar responses suggest that soil biota differ vastly in their vulnerability to global change drivers. Thus, important ecosystem processes like decomposition and nutrient cycling, which are driven by the interdependent activity of soil microorganisms and invertebrates, may be disrupted under future conditions.
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.
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