陕北黄土区生态修复过程中植物群落物种多样性变化

根据18块典型样地的植被调查数据，采用时空互代和对比分析法，从演替时间、生态修复模式和坡向3个方面研究了陕西省吴起县生态修复过程中植物群落物种多样性特征.结果表明：在25年自然演替序列中，退耕封育群落依次经历了猪毛菜、猪毛蒿、达乌里胡枝子、铁杆蒿和白羊草5种类型，建群种表现为1年生向多年生、低级向高级的演替趋势.其间，物种种类、Margalef指数、Simpson指数、Shannon-Wiener指数和Pielou指数均呈二次函数变化,说明黄土区退化生态系统在消除外界压力后，通过自然恢复可达到高级、稳定状态，但速度缓慢.地形条件和恢复年限一致时，4种主要修复模式形成的群落中，草本层的Margalef指数、Shannon-Wiener指数和Pielou指数表现为退耕封育＞退耕还草＞退耕还林＞荒山造林，Simpson指数则相反.与退耕封育模式相比，退耕还草和退耕还林模式在相同恢复期内形成的草本群落，虽然多样性指数较低，但更接近自然演替后期阶段，说明人工修复模式能加快演替进程.在相同恢复年限内，阴坡退耕封育群落的Margalef指数、Shannon-Wiener指数和Pielou指数明显大于阳坡，且群落类型更接近演替后期阶段，说明阳坡生态修复的本底条件更差，植被自然演替速率更缓慢.

Dynamics of plant community species diversity in the process of ecological rehabilitation in north Shaanxi loess area.

Based on the vegetation survey on 18 sampling plots in Wuqi County of Shaanxi Province, and by using the methods of substituting space series for time series and of contrastive analysis, the dynamics of plant community species diversity in the process of ecological rehabilitation in the County was analyzed from the aspects of succession time, rehabilitation mode, and slope direction. The results showed that in the 25 years natural succession series, the natural restoration community on previous cropland experienced the sequence of Salsola collina, Artemisia scoparia, Lespedeza davurica, Artemisia sacrorum, and Bothriochloa ischcemum, with the dominant species tended to be changed from annual to perennial and from low-class to high-class. The variations of species number, Margalef index, Simpson index, Shannon-Wiener index, and Pielou index in the succession process could all be described by a quadratic function y = at2 + bt + c, suggesting that after the outside pressure removed, the degraded ecosystem in loess area could naturally restore to an advanced and steady state, but the restoration rate would be very slow. With the same site factors and restoration periods, the Margalef index, Shannon-Wiener index and Pielou index of herb layer decreased in the order of naturally restoring on previous cropland (Ⅰ)＞converting cropland to grassland (Ⅱ)＞converting cropland to forestland (Ⅲ)＞afforestation on barren hills (Ⅳ), while Simpson index changed in adverse. Comparing with natural restoration, the community types of herb layer in Ⅱ and Ⅲ were at the more advanced stage of natural succession series though the species diversity index was lower, indicating that artificial planting would accelerate the succession process. In the same period of rehabilitation, the Margalef index, Shannon-Wiener index and Pielou index of natural restoration community were obviously higher on shady slope than on sunny slope, and the community type was at the more advanced stage of natural succession series, suggesting that the basic ecological rehabilitation condition on sunny slope was worse, and the succession rate was slower.