Are there links between responses of soil microbes and ecosystem functioning to elevated CO₂, N deposition and warming? A global perspective

Abstract

In recent years, there has been an increase in research to understand how global changes' impacts on soil biota translate into altered ecosystem functioning. However, results vary between global change effects, soil taxa, and ecosystem processes studied, and a synthesis of relationships is lacking. Therefore, here we initiate such a synthesis to assess whether the effect size of global change drivers (elevated CO2, N deposition, and warming) on soil microbial abundance is related with the effect size of these drivers on ecosystem functioning (plant biomass, soil C cycle, and soil N cycle) using meta-analysis and structural equation modeling. For N deposition and warming, the global change effect size on soil microbes was positively associated with the global change effect size on ecosystem functioning, and these relationships were consistent across taxa and ecosystem processes. However, for elevated CO2, such links were more taxon and ecosystem process specific. For example, fungal abundance responses to elevated CO2 were positively correlated with those of plant biomass but negatively with those of the N cycle. Our results go beyond previous assessments of the sensitivity of soil microbes and ecosystem processes to global change, and demonstrate the existence of general links between the responses of soil microbial abundance and ecosystem functioning. Further we identify critical areas for future research, specifically altered precipitation, soil fauna, soil community composition, and litter decomposition, that are need to better quantify the ecosystem consequences of global change impacts on soil biodiversity.

Soil Biodiversity and the Environment

“…Global change is unquestionably one of the greatest threats to soil biodiversity, with recent work indicating that global change impacts on soil biota moderate at least some ecosystem functions (86,87). Although we are accumulating knowledge of the impact of global change drivers such as climate change, eCO 2 concentrations, and land-use changes, there is still much to learn before we can make any broad predictions about their impacts in the longer term.…”

Effects of nitrogen enrichment on belowground communities in grassland: Relative role of soil nitrogen availability vs. soil acidification

“…Nitrogen deposition can also result in soil acidification, leading to the suppression of plant growth in grassland (Van Breemen and Van Dijk, 1988;Chen et al, 2013) or forest ecosystems (Berg and Verhoef, 1998;Bobbink et al, 2010). Although nitrogen impacts on plant communities are relatively well understood, we lack a comprehensive understanding of how nitrogen deposition affects belowground organisms and their interaction with plants, even though the belowground community greatly affects ecosystem structure and functioning (Wardle et al, 2004;Bardgett and Wardle, 2010;García-Palacios et al, 2015).…”

“…However, while nitrogen deposition increases nitrogen availability, it simultaneously causes soil acidification, which will also affect carbon allocation to soils (and hence the belowground food web) by changing the concentration of H þ ions and soil base cations (Van Breemen and Van Dijk, 1988;Kuperman and Edwards, 1997). In addition, a number of studies have focused on how the diversity or taxonomic group of belowground communities (mostly soil microbes) changes in response to nitrogen enrichment (Campbell et al, 2010;Ramirez et al, 2010), but the changes lack consistency García-Palacios et al, 2015). Surprisingly, few studies have simultaneously examined how multiple trophic levels of the belowground food web (e.g., microbes and nematodes) are affected by nitrogen enrichment (Fierer et al, 2009;Eisenhauer et al, 2012).…”

Toward a global platform for linking soil biodiversity data

“…However, we still lack baseline values for soil biodiversity as well as reference values (either abundance ranges or occurrence) that may prove critical in assessing the current status of soils and implementing management and policy efforts to keeping soils and soil biodiversity in a so-called "normal operating range" (Jackson et al, 2007;Koch et al, 2013). This will be particularly important as we continue to understand the impact of certain global changes on soil biodiversity and their interactions within functioning food webs (Blankinship et al, 2011;García-Palacios et al, 2015). For example, agricultural intensification reduces the abundance of soil fungi relative to bacteria, reduces earthworms, mycorrhizal fungi, and increases the numbers of plant parasitic nematodes (Tsiafouli et al, 2015).…”