Dynamic Changes Of Ecotone In Agro-forest Ecosystems Under The Influence Of Grain For Green Project

Land use and land cover change can be caused by Grain for Green Program. The understanding of impacts of the implementation of the Grain for Green Project on mountain agro-ecosystems and forest ecosystem, can provide a useful value for the sustainable use of land and the follow-up work of grain for Green Project.Two abandoned land in different years (2003and2009) in Weixi County, were selected in this study. In order to investigate the plant community structure, growth-type composition, species diversity and soil nutrient indicators of these two different abandoned land, for measuring the position and width of ecotone to explore ecological changes in ecological processes within the system in the level of landscape pattern. It has a very important practical significance to the landscape, the restoration of ecosystem and future trends driven by this project.The results are listed as following:(1) Herbaceous are the dominant species in2009abandoned land between2011to2013, Pine seedlings of scattered clouds appeared in abandoned land gradually. There is a three levels of the forest structure:tree, shrub and grass in the2003abandoned land, and shrubs replace herbaceous become the dominant species gradually with the age of farmland increased, the number of species decline herbs, and an increase in the proportion of tree species.(2) The farmland species composition and community structure of two plots tend more complex, species diversity index also increased between2011to2013. In the same year, the plot of farmland in2003each species diversity index are also higher than the abandoned plots in2009. It shows that in this area, natural recovery is an effective mode of vegetation recovery.(3)Along the abandoned land-Yunnan pine forest transect sequence, soil acidity of two abandoned plots are gradually increased between2011to2013. The change trend of soil pH shows that ecotone>abandoned land>Yunnan pine forest, the change trend of organic matter shows that ecotone> Yunnan pine forest>abandoned land in different age farmland plots.pH value of the overall trend in2013to be lower than in2011, organic matter content should be higher than in2011in the same piece of farmland plots, indicating that the ability to conserve soil nutrients stronger woodland, forest policy to promote the improvement of soil quality.(4) The width of ecotone increased7m based on the important value of species, and increased8m based on soil nutrients as a standard measurement abandoned land plots in2009between2011to2013. The width of ecotone increased15m based on the important value of species and soil nutrients as a standard measurement abandoned land plots in2009. Abandoned plots in2009presented ecotone narrow and steep peaks, indicating where the boundaries clear, with acute variant features, ecotone type of acute variant. Abandoned plots in2003presented ecotone gradually changes from steep gentle, pastoral zone of rapid change from the original type of flat-type transition type. It shows that ecotone change is a dynamic process, with the increase of farmland time, the pastoral zone width is increasing, two large heterogeneity adjacent plaque may eventually revert to a plaque and abandoned land could eventually become a succession of native species, mainly in Yunnan pine forest.