Abstract:

This study aimed to determine the effects of exogenous nutrient addition on soil arthropod communities in the alpine meadows. Three nutrient addition treatments （nitrogen， N； phosphorus， P； and combined nitrogen and phosphorus， NP） were established in Hongyuan County， northwest Sichuan， China， in late May 2012. Each nutrient treatment was applied at three concentrations： 10 g·m^–2 （N₁₀， P₁₀， and NP₁₀）， 20 g·m^–2 （N₂₀， P₂₀， and NP₂₀）， and 30 g·m^–2 （N₃₀， P₃₀， and NP₃₀）， with six replicate plots of 3 m×3 m. Another six 3 m×3 m plots in natural alpine meadow served as control plots. The nutrient treatments were added every year for continued eight years. The soil arthropods and soil environmental factors in each plot were evaluated in August 2017 and 2020. Soil arthropods were extracted from the soil samples for 48 h at 38 ℃ using the Tullgren method in the laboratory. The main findings were as follows： 1） N， P， and NP additions in the alpine meadow increased the individual density and diversity of soil arthropods， with the strongest effects in the 20 g·m^-2 and NP treatments； 2） The abundances， taxonomic richness， and Shannon’s diversity index of the soil arthropod communities in the N-addition and P-addition treatments increased significantly from 2017 to 2020 （P<0.05）， while the abundance and taxonomic richness of soil arthropod communities in the NP-addition treatment declined significantly from 2017 to 2020 （P<0.05）， but no significant change was detected for Shannon’s diversity index （P>0.05）； 3） The abundance of Entomobryomorpha was significantly increased in the N-addition and P-addition treatments （P<0.05） and the abundances of Oribatida and Mesostigmata were significantly increased in the NP-addition treatment （P<0.05）； 4） The results of multiple regression analysis and canonical correspondence analysis showed that the main environmental factors influencing the composition of soil arthropod communities were the contents of soil total N， total P and soil organic matter， pH， aboveground biomass， and plant community cover. Our results showed that the soil arthropod communities respond differently to different exogenous nutrient additions and nutrient gradients； and that the diversity of soil arthropods in alpine meadows can be promoted by N-addition and P-addition but restrained by mixed N and P additions after continued eight years additions. We recommend that the additions of mixed N and P to the alpine meadows should be controlled at 20 g·m^–2 per year and should not exceed eight years.

Key words: N and P addition, alpine meadows, mites, collembola, diversity