黄土丘陵区不同退耕年限草地群落特征及其土壤水分养分效应

Relationships between community characteristics and soil nutrients and moisture in abandoned hill country grassland

采用空间代替时间以及对比分析的方法,根据黄土丘陵区8个退耕年限序列（1~35年）的退耕地的采样数据进行分析,研究在植被恢复过程中,随着退耕年限变化,植被更新与土壤水分养分之间的互动效应。结果表明,1）黄土丘陵区在退耕35年期间,随着退耕年限的增加,总物种数呈减少-增加-减少-增加的趋势。Margalef指数、Shannon-Wiener指数变化趋势为先增加-减小-增大,而Pielou均匀度指数相反。2）群落地上地下生物量随退耕年限增大而增大,呈显著正相关关系（P〈0.05）。3）随着退耕年限增加,土壤养分（除速效K外）含量先减少后增加,而土壤速效K含量呈一直下降趋势,土壤水分含量在20~50cm、50~80cm、80~100cm处先增加后减少,在0~20cm处相反。4）植被特征指数（除Pielou外）与有机质、全N、全P呈显著正相关,而与土壤养分速效K呈正相关,关系不显著。Pielou指数与土壤养分呈正相关关系,但不显著。

Using comparative analysis and substituting temporal serial with spatial serial data, we analyzed data collected from abandoned farmland with eight different vegetation restoration periods （1-35 years）. The interaction between vegetation regeneration, soil moisture and soil nutrients as the vegetation restoration period changed was also investigated. Results; 1） During 35 years of natural restoration the number of species present fluctuated, initially decreasing, increasing and decreasing again. The Margalef richness index and Shannon-Wiener index firstly increased, then decreased, and then increased again. However, the Pielou evenness index showed the opposite trend. 2） With increasing restoration period, aboveground biomass and underground biomass were both significantly positively correlated with restoration duration. 3） As restoration duration increased, soil moisture and soil fertility （except available phosphorus） in different soil layers initially declined and then increased. Available phosphorus decreased. Soil moisture of 20-50 cm, 50-80 cm, 80-100 cm initially declined and then increased; the opposite pattern was observed in the 20cm soil layer. 4） During the restoration process, indices of vegetation traits （except the Pielou index） were significantly positive correlated with soil nutrient content including soil organic matter, nitrogen and phosphorus.