A synthesis of soil nematode responses to global change factors

Human-induced global changes may significantly alter the structure and function of terrestrial ecosystems. Although nematodes play a critical role in material cycles and soil food webs, the overall trend and magnitude of changes in nematode responses to global change remain unclear. In this study, we synthesized nematode responses to the major global change factors (i.e., nitrogen (N) deposition, climate warming, elevated CO2, and drought) using data extracted from published global change experiments. We found that nematode and soil micro-food web responses differed among the global change scenarios. Specifically, N addition significantly decreased generic richness (−9%) and the abundance of fungivores (−14%) and omnivore-predators (−26%). Warming had minor effects on soil nematodes. Elevated CO2 significantly increased total nematode abundance (20%), the abundance of fungivores (42%) and herbivores (22%), and the ratio of fungivorous nematodes/bacterivorous nematodes (32%) but decreased nematode generic richness. Drought reduced total nematode abundance (−20%). Soil nematode responses to global change factors were influenced by the experimental system (i.e., ecosystem types and experimental duration) and environmental factors (i.e., mean annual temperature, mean annual precipitation, and latitude). Our synthesis indicates that soil pH, NH4+ content, N-application rate, ecosystem types, and experimental duration may be the main factors explaining the negative effects of N addition on soil nematodes, and that the warming effects may be best explained by soil moisture and ecosystem types. These findings can help to better predict how global change factors affect soil nematodes.