Responses of ground-active arthropods to black locust (Robinia pseudoacacia L.) afforestation in the Loess Plateau of China

Afforestation is one of the most common management approaches for preventing soil erosion. Robinia pseudoacacia (RP), a pioneer and nitrogen-fixing tree, have been widely used for afforestation in the highly eroded regions of the Loess Plateau. While its effects on soil properties are well known, there have been few studies on the biodiversity, especially the belowground biodiversity. Here, we investigated vegetation communities, soil properties, and ground-active arthropod diversity in areas where RP was planted 16, 19, and 31 years (Y) ago and natural control areas without RP plantation in the Loess Plateau. We recorded 2335 individuals that belonged to 23 taxonomic groups in the study site. At the community level, the overall ground-active arthropod abundance and Simpson index (except 16-Y plots) did not significantly vary between the control and afforested RP plots, whereas richness and Shannon index were higher in the RP plots (except 16-Y plots) compared with the control plots. At the functional group level, the abundance and richness of predator did not significantly vary between the control and afforested RP plots, but the phytophage richness was significantly higher in the afforested RP plots (except 16-Y plots). We also found that the richness and/or diversity of ground-active arthropods at both levels generally increased with increasing plantation age. Additionally, the community composition differed among the four habitats, and these differences were primarily attributed to differences in soil temperature and pH, most likely in response to the RP plantation. The results demonstrated that functional groups had differing responses to RP plantation; in particular, RP plantation and plantation age had positive effects on ground-active arthropod diversity. These findings indicated that RP plantation can produce positive conservation outcomes for ground-active arthropods in the Loess Plateau, except at their early age.