Effects of environmental warming and drought on size‐structured soil food webs

Abstract

Soil systems maintain important ecosystem processes crucial for plant life and food production. Especially agricultural systems are strongly affected by climate change due to low vegetation cover associated with high temperatures and drought. Nevertheless, the response of soil systems to climate change is little explored. We used microcosms with a simplified soil community to address effects of climate change using independent temperature and dryness gradients and addressed their effects on top–down control and litter decomposition. The community consisted of maize litter as a basal resource, fungi, springtails and as top predators mites and centipedes. As the body‐size structure is of high importance for communities, we included differently‐sized springtails and predator species. After seven weeks, the experiment was terminated, and the impact of climate change on direct feeding interactions and indirect effects across trophic levels was analysed. With increasing temperature and dryness, consumption rates increased, thereby amplifying the negative influence of consumer populations on their resources. Hence, these climate‐change variables increased the top–down control of 1) predators (mainly mites) on springtails and 2) fungi on litter decomposition. In addition, we found that the climate‐change variables strengthened trophic cascades from predators on fungi whose density was thus increasingly decoupled from top–down control by their springtail consumers. Their increased decomposition rates are of high importance for carbon cycling and may result in accelerated nutrient turnover. In conclusion, our results suggest that climate change may strongly influence the structure and functioning of soil systems by strengthening consumption rates and trophic cascades, which will have far reaching consequences for the nutrient turnover and productivity of agricultural ecosystems.

Trophic cascades in the bryosphere: the impact of global change factors on top‐down control of cyanobacterial N2‐fixation

“…the decomposers of organic matter (Lensing & Wise ) or the predators (Lang et al . ). Together, these examples emphasise the importance of testing the context dependency of trophic cascades and top‐down control.…”

“…Further, the effects of environmental change on trophic cascades in decomposer food webs depend on which trophic level is most strongly affected, i.e. the decomposers of organic matter (Lensing & Wise 2006) or the predators (Lang et al 2014). Together, these examples emphasise the importance of testing the context dependency of trophic cascades and top-down control.…”

Impacts of altered precipitation regimes on soil communities and biogeochemistry in arid and semi‐arid ecosystems

“…These fauna influence microbial abundance, activity, and turnover (e.g., Griffiths, 1994;Cole et al, 2004), and may be key in moderating microbial responses to altered climate (A' Bear et al, 2012). For instance, a recent study showed that drought and increased temperature impact top-down effects of predatory soil invertebrates in an agricultural soil (Lang et al, 2014). While many studies have shown impacts of altered precipitation regimes on soil biota in mesic ecosystems (e.g., reviewed by Borken & Matzner, 2009), results are ecosystem dependent (e.g., Stafford Smith & Morton, 1990), and relatively fewer studies have taken place in drylands than other ecosystems.…”

The use of DNA barcodes in food web construction—terrestrial and aquatic ecologists unite!

“…our review above). Among terrestrial webs, some recent research focuses on size as a structuring factor, with soil food webs being among the environments where trophic interactions may be strongly structured by size (Digel et al 2014;Lang et al 2014). In other environments, the structuring force seems to vary with the specific type of interaction examined (Petchey et al 2008;Dunne et al 2013).…”