摘 要 ：以中国科学院内蒙古草原生态系统定位研究站典型草原施肥小区为对象，研究了连续5a施氮肥（不施肥对照-CK，N525、N105、N175和N280 kg hm-2）和磷肥（P9、P37和P75 kg hm-2）对土壤生物多样性的影响。结果表明，连续5a施氮磷肥，随施肥量增加，土壤微生物量碳氮、微生物活性和代谢熵显著降低，而土壤微生物量磷则显著增加。高氮（N280）和高磷（P75）处理，不仅显著降低了微生物利用碳源的能力和微生物功能多样性，而且改变了微生物利用碳功能群结构，施氮肥处理更为明显。大量施用氮肥显著降低了土壤线虫总数和不同营养类群的数量，而施磷肥对线虫总数影响并不显著，相反，施磷肥和少量氮肥却提高了食细菌线虫的数量和比例。施用氮肥土壤原生动物总数呈下降趋势，而施磷肥则显著增加，但适度施用氮肥和磷肥时，土壤原生动物群落最为旺盛，尤其是施磷肥后肉足虫数量大幅度提高。氮磷肥对土壤理化性质和植被组成影响的差异，可能是土壤生物对不同肥料及其用量的响应存在较大差异的原因所在，其中施氮肥多以负效应为主，而施磷肥则多以正效应为主。
Abstract:The objective of this study was to explore the effects of N and P fertilization for 5 years on soil biodiversity in the Inner Mongolia steppe. The soil samples were collected from the following treatment: control (no fertilizer), N fertilizer (N 52.5, 105, 175 and 280 kg hm-2) and P fertilizer (P 9, 37 and 75 kg hm-2), which were established in 2000. The results showed N and P fertilizer applications significantly reduced the soil microbial biomass C and N content, microbial activity and metabolic quotient, but increased the soil microbial biomass P. The ability of microorganisms to use carbon sources and microbial functional diversity were lower and the carbon utilization-functional groups′ structure of microorganisms significantly changed in plots with addition of N280 and P37 compared to that without fertilizer. Application with higher level of N fertilizer significantly reduced the abundance of total nematodes and its different trophic groups, while P fertilizer had no significant impacts on total number of soil nematodes. In contrast, P and lower level of N fertilizer increased the abundance of bacterivorus nematodes. Fertilization also significantly changed the total number and types of soil protozoa in Inner Mongolia steppe. For example, the total number of soil protozoa decreased after N fertilization, while it significantly increased after P fertilizer input. The largest amount of protozoa appeared when moderate amounts of N and P fertilizer were applied. In particular increasing P input increase the amoeba population. The different response of soil biota to different kinds of fertilizer and its quantity was due to the difference in soil physical and chemical properties and plant composition caused by the application of N and P fertilizer. In general, the activity and diversity of soil biota in Inner Mongolia steppe have negative feedbacks with N fertilization, while positive feedback with P fertilization.