Effects of Harvesting Disturbance on Soil Nematode Diversity and Soil Properties in Ophiocordyceps sinensis Excavation Areas of the Qinghai–Tibet Plateau

Ophiocordyceps sinensis (O. sinensis) is a valuable medicinal fungus distributed in the Qinghai–Tibet Plateau and adjacent high-altitude regions. Wild excavation has raised increasing concerns about its impact on fragile alpine soil ecosystems. Soil nematodes are sensitive indicators of soil environmental change and can effectively reflect disturbance-induced shifts in soil biotic communities. Understanding the effects of O. sinensis excavation on soil nematode diversity is essential for assessing soil biological health and supporting sustainable management of alpine ecosystems. However, most existing studies are limited to single regions, and few have simultaneously analyzed changes in soil properties, nematode diversity, and soil–nematode relationships across heterogeneous landscapes. The goal of this study was to reveal the impacts of O. sinensis excavation on soil physicochemical properties, nematode diversity and community composition, as well as soil–nematode relationships in typical producing areas, and to assess the ecological risks of current harvesting practices. We investigated five typical O. sinensis-producing regions in Qinghai Province (Henan, Hualong, Maqin, Yushu, Zaduo) and compared excavated and non-excavated sites to evaluate disturbance effects. The results showed strong regional heterogeneity in soil responses to excavation. Soil available potassium (AK) was significantly and consistently lower in all excavated sites (p < 0.01), whereas changes in other soil nutrients varied by region. Nematode α-diversity was generally stable, with a significant decrease in the Shannon index only in Henan (from 2.91 to 2.46). Soil nematode community composition was highly similar between treatments, with more than 70% of shared genera and species remaining largely unchanged and dominant taxa unchanged. Correlation analysis indicated that excavation reshaped soil–nematode relationships, and AK may act as a potential influencing factor associated with nematode diversity in disturbed sites. Overall, under current excavation intensity, the impacts of O. sinensis harvesting on total soil nematode diversity are relatively limited. However, the widespread reduction in AK and localized diversity decline suggest potential long-term ecological risks under intensive or prolonged disturbance.