Spatio-temporal change of tea plantation since 2000 and model-based prediction in the Tianmuhu Reservoir watershed

Abstract

Land use /cover change(LUCC) is closely related to regional sustainable development.It is an important issue in LUCC investigations to analyze the relationship between land use change and its influencing variables on spatial scale,to reveal the change in land use and its spatio-temporal distribution characteristics by developing a simulation model,and to support the future decisionmaking.This study took the Tianmuhu Reservoir watershed,the land use of which has been changed rapidly with the dominant cash crop of tea plantation in upstream of the Lake Taihu basin,as the study area.Interpretation of the high-resolution remote sensing imagery provided the data of tea plantation and other land uses since 2000.Topography and soil data were obtained from the 1∶50000 scale national standard relief map and soil sampling with laboratory analysis,respectively.Analyses of the spatial distribution and area change of existing and newly-exploited tea plantation since 2000 revealed that the tea plantation area was in a rapidly increasing trend.The tea plantation area expanded 5 times in the past 11 years and half of those increased in the last 3 years.There was a big difference in the spatial distribution of tea plantation among sub-regions,because of their different natural backgrounds,geographical factors and suitability conditions for tea plantation.The results of Cramer V chi-square test showed that elevation,slope,reservoirs,rivers,villages,roads and the scale of tea garden were the most significant factors for the spatial distribution of tea plantation.The MLP neural network model for the prediction of tea planation was developed through iterations based on the seven significant influencing factors.It was validated using the area of existing tea plantation,the performance of which reached to 84%.Application of the model in predicting the future spatial distribution of tea plantation under current,2000,and the compromised tea-exploitation mode displayed that the area of tea plantation in 2020 will account for 1 /4 of the watershed area if it is exploited following the current pace.None of the three scenarios could change the growing trend of tea plantation.Therefore,it is urgent to push the local government to take corresponding strategies and measures to control the increasing area of tea planation and adjust its spatial distributions