藏北高寒草甸土壤线虫群落结构和多样性对增氮的响应

土壤线虫在高寒草甸生态系统物质循环和能量传递过程中起重要作用。高寒草甸植物对氮沉降极为敏感，但增氮对土壤线虫群落结构和多样性的影响仍不明确。本研究在西藏那曲高寒草甸开展模拟氮沉降试验，设置0、7、20、40 kg N·hm^-2·a^-14个增氮水平(硝酸铵)，研究增氮对高寒草甸土壤线虫群落结构和多样性的影响。结果表明：1)增氮显著改变了高寒草甸土壤线虫的群落组成，并且降低了线虫多样性和均匀度；2)N₂₀、N₄₀显著提高了食细菌线虫(Ba)类群的相对丰度，较对照组分别提高了30.4%和31.7%;3)线虫多样性指数(H’)和均匀度指数(J)均表现为N_ck>N₄₀>N₂₀>N₇，不同处理间植物寄生线虫指数(plant parasite index,PPI)、自由线虫成熟度指数(maturity index,MI)、瓦斯乐思卡指数(wasilewska index,WI)无显著差异。在不同增氮条件下，线...

Response of soil nematode community structure and diversity to increased nitrogen in alpine meadows of northern Tibet

Soil nematodes play an important role in material cycling and energy transfer processes in alpine meadow ecosystems. Alpine meadow plants are extremely sensitive to nitrogen deposition， but the effect of increased nitrogen on the structure and diversity of the soil nematode community remains unclear. In this study， we conducted a simulated nitrogen deposition experiment in alpine meadows in Nagqu， Tibet， with four levels of nitrogen enrichment： 0 （CK）， 7， 20， and 40 kg N·ha^-1·yr^-1. Then， we investigated the effects of nitrogen enrichment on the structure and diversity of the soil nematode community. The results showed that： 1） Increased nitrogen significantly changed the soil nematode community composition in alpine meadows and reduced nematode diversity and evenness； 2） the N₂₀ and N₄₀ treatments significantly increased the relative abundance of bacterivore （Ba） taxa by 30.4% and 31.7%， respectively， compared with the control group； 3） The treatments could be ranked， from highest nematode diversity index and evenness index to lowest， as follows： N_ck>N₄₀>N₂₀>N₇. There were no significant differences in the plant parasite index， maturity index， and Wasilewska index （WI） among the treatments. The nematode channel ratio was greater than 0.5 and the WI was greater than 1 under different nitrogen enrichment conditions， indicating that the soil nematode taxa in the study area were mainly bacterivore nematodes， and that the main players in the mineralization pathway were bacterivore and fungivore nematodes； 4） The ammonia nitrogen content in soil was significantly and positively correlated with the total numbers of nematodes and bacterivores. This study clarified that the increase in the total number of soil nematodes in the alpine meadows of northern Tibet under nitrogen deposition is because of increased numbers of bacterivore nematodes. These results provide a reference for exploring how alpine meadow ecosystems in northern Tibet will respond to nitrogen deposition.