The Characteristics Of Community Succession And Interaction With The Soil Environment In Abandoned Croplands

As a key component of ecosystem, vegetation plays an important role in ecologicalenvironmental adjustment. Research and practices have shown that although vegetationrestoration can promote degenerated ecosystem in different degree, there seems somephenomena in Loess Plateau, for instance, planted grasses and woods died and some of thembecame small old trees after years. The reason is that the characters of vegetation and soil andtheir interactions have not been thoroughly comprehended. So the study of the interactionbetween recovering succession vegetation and environmental (especially sois) variables ofabandoned lands in loess hilly region is meaningful to implementation of grain for green policyand improvement of ecology.A spatial series representing the temporal sequence is studied in this paper: investigatingand analysing the character of plant communities and soil variables of different abandonedtimes and different restoration measures. The main results are as follows:1. The steps of vegetation succession in abandoned fields are as follows: Artemisiacapillaris dominated community-Seed dominated community-Setaria viridis dominatedcommunity-Stipa bungeana dominated community-Artemisia sacrorum dominatedcommunity-Artemisia giraldii dominated community. With the succession, diversity index ofSimpson and eveness index of Pielou are according with an“S”curve, the former is relativelybigger at the early and later succession stages, diversity index of Shannon-wiener and richnessindex of Margalef are according with the law of logarithm. The distribution pattern ofabundance varied from geometric series to lg-normal distribution, community coverageincreased gradually.2. Soil moisture content in different soil depth shows rising trend in successive plantcommunity, but the variance decreases; in different communities, the water content of ZizaniaArtemisia community is highest, Stipa bungeana community is lowest, others are between than them. On the other hand, the water content is lower in sunny slop than in shady slope, halfshady slope (half sunny slope) at the middle, the water content of heavy gradient is lower thanlight gradient, elevation of high water content is lower than the low elevation.3. The nutriment content of surface soil in0-20cm depth, such as organic matter, total N,available N and available K content increase with the increasing of restoration time, thechanges of soil pH are on the contrary, and the increases of total P, available P and available Kcontent are not significant. The organic matter content shows a highly significant correlationwith total N and available N contents, the same relationship is shown between pH and organicmatter, total N and available N content. Others are not significant.4. Canonical correspondence analysis on species in abandoned croplands and soil factorsshows that soil water content, and soil organic matter, total N, total P, available P significantlyaffect the vegetation variation in the hilly-gullied Loess Plateau. In compare, organic matter,total N and pH have remarkable influence on species. The effects of total P, available P,available K and terrain factors on vegetation variation are similar. In addition, average soilaqueous content in0-100cm depth, vegetation coverage and succession time are closely relatedto vegetation variation and soil properties.In a word, soil nutrient increases and pH decreases, In other words, soil fertility improveswith vegetation recovery succession in Abandoned Lands in Hilly and Gully Regions on theLoess Plateau. Soil water, soil organic matter, total N and available N are important factors ofdistribution and characteristics of plant community. Generally speaking, both soil water contentand soil fertility, especially P element are low. Considering the dry weather and the loess parentcontaining, natural restoration is a principal measure on abandoned croplands in hilly-gulliedLoess Plateau. Artificial shrub and aboreal can be cultivated according to local soilenvironment so as to accelerate vegetation restoration, but the reasonable density has to becontrolled.