Biocrusts regulate the seasonal dynamics of soil nematode diversity in a semiarid ecosystem

Drylands are of the most stressful environments and covered by biocrusts which create biotic islands essential for other soil organisms. Although the roles of biocrusts as moderators of microbial community assembly have been extensively studied, much less is known whether soil fauna are affected by these biocrusts and their seasonal dynamics. Here, we used soil nematodes as indicators of soil fauna to assess how different biocrust types affect the seasonal dynamics of nematode abundance and diversity on the northern Loess Plateau of China. We unveiled that biocrusts are highly critical for reshaping soil nematode community in drylands, where the total number, Patrick index, and Shannon-Wiener index of nematode community in biocrusts were 357 %, 260 %, and 91 % higher than that of bare soil, respectively. Biocrust traits and their alteration on soil properties are the principal factors through which affect soil nematode community. Furthermore, those soil nematodes were also primarily affected the seasonal fluctuations of soil temperature, moisture, and the contents of organic matter, NO₃⁻-N, NH₄⁺-N, and chlorophyll, resulting in a distinct seasonal pattern of nematode community underneath biocrusts. In summary, our findings indicated that biocrusts facilitate the development of soil nematode (fauna) community in drylands through increasing soil stability and food sources, but the level of their influences are determined by biocrust types and seasons. We highlight the critical roles of biocrusts in shaping soil fauna assembly in dryland ecosystem, by which further mediating ecosystem processes and services.