油蒿群落演替中的植物密度对土壤氮/磷比的响应

选择腾格里沙漠东缘内蒙古阿拉善左旗境内的油蒿+冷蒿群落为研究对象,在80 m×80 m样地400个4 m×4 m样方中,调查了油蒿和冷蒿的密度,测定了0～20 cm土层中的全氮和有效磷,分析了土壤氮/磷比与植物密度之间及其空间异质性之间的关系。结果表明,油蒿密度随土壤氮/磷比的增大而减小,冷蒿密度随土壤氮/磷比的增大而增大;油蒿密度的空间异质性随土壤氮/磷比的空间异质性的增大而减小,冷蒿密度空间异质性与土壤氮/磷比空间异质性无关。分析表明,植物密度的变化与土壤氮/磷比的变化密切相关,随着土壤氮/磷比的增大,油蒿逐渐退出,冷蒿逐渐侵入。因而,土壤氮/磷比的变化是干旱区油蒿群落演替的一个原因。

Response of plant densities to N/P ratio in soil under artemisia ordosica community in succession

A successional Artemisia ordosica and A. frigid community, located on the eastern edge of the Tengri Desert in Alashan Left Banner, Inner Mongolia, was selected as an object for study. Densities of the plants and total nitrogen (N) and available phosphorus (P) in 0~20cm soil layer were measured of the 400 quadrates (4m×4m) in the sampling plot (80m×80m) for analysis of relationship between N/P ratio in the soil and plant density thereupon and between the two in spatial heterogeneity. Results show that with increasing N/P ratio, the density of A. ordosica decreased, but the density of A. frigid increased; while with intensifying spatial heterogeneity of N/P ratio, the spatial heterogeneity of A. ordosica density weakened but the spatial heterogeneity of A. frigid density displayed no relationship, which suggests that the plant density is closely related to N/P ratio, and A. frigid is displacing A. ordosica as N/P ratio increases. Thus, change in N/P ratio in the soil is one of the causes of the succession of A. ordosica community in the arid zone.