CO2浓度升高和氮肥管理对土壤线虫群落的影响

大气CO2浓度升高能够对农田生态系统产生一系列的影响。土壤线虫在农田生态系统腐屑食物网中占有重要的地位，能够对外界环境变化作出较迅速的响应。本文利用江苏省江都市小记镇的稻-麦轮作FACE系统研究平台，在2007-2008年小麦生长季，研究了大气CO2浓度升高和不同氮肥处理（高N和低N）对农田土壤线虫群落的影响。 研究结果表明：高氮肥施用情况下, CO2浓度升高显著降低了麦田土壤铵态氮和硝态氮含量。不同氮肥处理中CO2浓度升高条件下土壤可溶性碳的含量显著低于对照，而土壤总有机碳和微生物量碳含量高于对照。 大气CO2浓度升高条件下，麦田土壤线虫群落组成和多样性与对照相比表现出显著差异。CO2浓度升高显著增加了麦田土壤线虫总数、食细菌线虫、食真菌线虫和植物寄生线虫数量。在小麦拔节期和成熟期，低N和高N施用条件下，FACE处理中土壤线虫多样性指数（H’）、成熟度指数（MI和PPI）均低于对照处理，而结构指数（SI）高于对照处理。线虫生态指数的结果表明，大气CO2浓度升高条件下，土壤线虫群落多样性降低，土壤环境受到一定的干扰，食物网趋于结构化。

Elevated atmospheric CO2 can make effect on cropland ecosystems. Soil nematodes play important roles in the detritus food web, which can show responses to the environmental changes. Effect of elevated atmospheric CO2 on soil nematode communities in the wheat growth season of 2007 and 2008 was conducted at a rice-wheat rotational free-air CO2 enrichment (FACE) platform in Jiangdu municipality, Jiangsu province, two application rates of nitrogen (high HN and low LN) were adopted. Following the CO2 enrichment, the contents of DOC、NH4+-N and NO3--N showed a decreasing trend, especially DOC in the HN treatments; while the contents of TOC and Cmic showed an increasing trend in both HN and LN treatments. Following the CO2 enrichment, nematode community structure and diversity were significantly affected. The abundance of total nematodes, bacterivores, fungivores and plant-parasites increased in the FACE. At wheat jointing and ripening stages, values of shannon diverstity (H’), maturity index and plant-parasites maturity index (MI and PPI) were lower in the FACE than the Ambient, while that of structural index (SI) showed an opposite trends. The results in the nematode ecological indices indicated that the elevated CO2 decreased the nematode diversity, soil environment under elevated CO2 was disturbed and food web tended to be structured compared with the Ambient.