Tree productivity and water production potential in Returning Farmland to Forest Project in Datong County, Qinghai Province

To make clear the development direction of the Returning Farmland to Forest Project in Datong County, Qinghai Province, from 2002 to 2003,based on the investigation of sample plots and stem analysis of remained plantation communities in the areas of returning farmland to forest in the 1980's in this region,the authors studied tree productivity and moisture potential productivity of five types of plantations on the land of returning farmland to forest,including Populus cathayana and shrub mixed forest,Betula platyphylla and Picea asperata mixed forest,Larix principis-rupprechtii pure forest,Picea purpurea pure forest and Betula platyphylla pure forest.The results show that:in sub-humid region of Loess Plateau,plant climate potential productivity is about 8 462 kg/(hm²·a),the productivity index of P. cathayana and shrub mixed forest,B. platyphylla pure forest,P. purpurea pure forest and B. platyphylla and P. asperata mixed forest with the density of 2 100-3 333 per hm² can serve as a potential productivity standard of actual biomass of established arbor forests under the local conditions.The actual potential water productive efficiency of P. purpurea pure forest and B. platyphylla pure forest are 17.22 and 22.14 kg/(hm2·mm·a) respectively,and that of P. cathayana and shrub mixed forest and B. platyphylla and P. asperata mixed forest are 21.14 and 19.09 kg/(hm2·mm·a).These types of forestation models are the development direction of the Returning Farmland to Forest Project.