Abstract: Spiders, as significant consumers, play a crucial role in maintaining biodiversity and ecosystem functions of pine plantations in arid and semi-arid regions. However, the diversity of ground-dwelling spiders in the Chinese pine forests in the areas where farmlands have been returned to forests of the Loess Plateau in northern Shaanxi remains poorly understood, limiting our understanding of the variations of spider community structure, ecological niches, and the maintenance mechanisms of spider diversity. In this study, four stands of Pinus tabuliformis with varying restoration ages were selected in Wuqi County, Yan’an City, along with an abandoned grassland as a control. Spider diversity was evaluated using the pitfall trapping method. One-way ANOVA and PCA were employed to compare species composition similarity, community diversity, and the niche characteristics of ground-dwelling spiders across different restoration years. The impacts of soil factors on spider diversity were analyzed. The results showed that: (1) The dominant ground-dwelling spider species in P. tabuliformis forests were Agroeca mongolica, Pardosa schenkeli, and Draconarius yananensis, which together accounted for over 50% of the total captures. (2) With increasing restoration years, the number of ground-dwelling spiders in P. tabuliformis forests gradually decreased. The species richness of spider communities did not significantly differ among restoration years, exhibiting a trend of initial decline followed by an increase. The evenness index and Shannon index initially increased, then decreased, and finally increased again. The Simpson index first decreased, then increased, and finally decreased again. The Jaccard similarity index among different habitats ranged from 0.39 to 0.72, indicating that ground-dwelling spider communities exhibited a moderate level of dissimilarity and similarity. (3) Among the spider species, Gnaphosa sinensis had the widest niche breadth and Gnaphosa songi had the narrowest. Niche overlap values for the primary ground-dwelling spiders varied from 0.33 to 1, with high overlap accounting for 37.88%, moderate overlap for 25.76%, and low overlap for 36.36%. The total niche response rate of the 12 main ground-dwelling spider species was positive, suggesting that they were in a developmental stage. (4) The key soil physicochemical factors influencing the distribution of ground-dwelling spiders in P. tabuliformis forests of varying restoration ages on the Loess Plateau included available potassium, capillary porosity, soil moisture, total nitrogen, pH, and alkaline hydrolyzable nitrogen. This study elucidates the variations and niche characteristics of ground-dwelling spiders in pine forests across different restoration years, thereby enhancing our understanding of spider population dynamics in artificial pine forests under the Grain for Green Program in northern Shaanxi.

Key words: ground-dwelling spider, variation pattern, ecological niche