Effects of marsh wetland degradation on the soil nematode community composition and functions in the Songnen Plain, northeastern China

Wetland degradation is a major threat to global biodiversity. Knowing how soil nematodes respond to wetland degradation can help predict its impact on ecosystem functions. In this study, the impacts of wetland degradation on soil nematodes and the interactions with soil physicochemical characteristics were explored via high-throughput sequencing and network analysis under different degradation degrees. There was a significant decline in the diversity of soil nematode communities with increasing degradation. An increase in degradation was correlated with a higher abundance of Chromadorea and a decrease in the relative abundance of omnivorous-predatory nematodes. This suggests that with wetland degradation, the structure of the soil nematode community becomes less complex, and the nutrient sources for soil nematodes become scarce. Wetlands subjected to varying degrees of degradation exhibited significant alterations in the structure of soil nematode communities. Severe degradation was associated with a pronounced decrease in the Shannon diversity index. Non-metric multidimensional scaling analysis indicated that the different degradation levels differed in their impacts on soil nematode communities. Mantel analysis showed that soil pH, soil organic carbon, and total nitrogen play a crucial role in determining soil nematode community structure. Symbiotic network analysis revealed that wetland degradation decreased the number of links in the network of soil nematodes. The modifications to the soil environment induced by wetland degradation are likely to intensify the effects of these factors on the characteristics of soil nematode communities. Consequently, wetland degradation can be assessed and restored by studying the effects of soil nematode communities on the soil.