Impacts of bacterivorous nematode identity and abundances on soil greenhouse gas emissions

Soil organisms are essential drivers of greenhouse gas (GHG) emissions, with bacterivorous nematodes playing a crucial role in regulating soil carbon and nitrogen cycling processes. These nematodes influence microbial communities and nutrient dynamics, which in turn affect GHG fluxes. However, their species-specific contributions to GHG dynamics remain poorly understood. This study investigated the effects of two bacterivorous nematode species, Protorhabditis spp. and Caenorhabditis elegans on soil GHG emissions using a 20-day microcosm experiment. Seven treatments were established: a control (without nematodes) and inoculations of Protorhabditis spp. or C. elegans at densities of 1, 2, and 3 individuals per gram of dry soil. The results showed that C. elegans significantly increased the cumulative emissions of CO₂ and N₂O compared to the control. Random forest analysis identified C. elegans abundance was the most critical factor influencing cumulative GHG production. However, Protorhabditis spp. did not significantly affect CO₂ emissions compared to the control, despite its faster population growth rate and higher abundance over the experimental period. The contrasting effects of the two bacterivorous nematodes on GHG emissions highlight the distinct ecological roles of nematode species in regulating soil processes. These findings suggest that nematode species-specific traits exert a greater influence on soil GHG emissions than nematode abundance alone. In addition, the density-dependent effects observed for C. elegans demonstrate that abundance can also be an important determinant of GHG fluxes. This study provides novel insights into the differential roles of bacterivorous nematodes in soil biogeochemical processes and underscores the importance of species composition in regulating soil GHG emissions.