Responses of soil nematode metabolic rate and energy flow to nitrogen addition and precipitation pattern change in a typical northern grassland

Aims: Soil nematodes are crucial soil organisms that are highly sensitive to environmental changes.Their diverse groups occupy multiple trophic levels within the soil food web, and their metabolic rates and energy fluxes can thus serve as powerful metrics for assessing ecosystem functioning.Global climate change has resulted in significant shifts in the nitrogen deposition and precipitation pattern in northern temperate grasslands, but it remains largely unknown how these shifts and their interactions might affect soil nematode metabolic rate and energy flow.The study aims toinvestigate the responses of nematode metabolic rates and energy flows to the interaction between nitrogen addition and precipitation intensity change.Methods: We conducted an eight-year controlled experiment with precipitation and nitrogen addition in the Duolun region of Inner Mongolia.The experiment assessed five levels of precipitation intensity while maintaining a constant total and varying frequency.The experiment's total nitrogen addition included 10 gm -2 yr -1 .Results: The results showed that the interaction between nitrogen addition and precipitation pattern change had significant negative impacts on nematode metabolic rate and energy flux.Under changing precipitation patterns, shifting towards higher intensity and lower frequency events, nematode metabolic rates and energy fluxes initially increased with increasing precipitation intensity, peaking at high intensity before declining.However, this trend was weakened by the effects of interactions between nitrogen addition and precipitation pattern change.Under the interaction effects of nitrogen addition and precipitation pattern change, nematode metabolic rate and energy flow were primarily driven by bottom-up effects of food resources within the nematode food web.Conclusions: The experiment showed that soil nematode metabolic rates and energy flows are negatively impacted by the interaction between nitrogen addition and precipitation pattern change.This research provides insights into the impacts of multi-factor interactions on underground biological communities in the context of global climate change.