The potential productivity of the main species used in the Datong reafforestation project on former farmland, Qinghai Province
青海大通退耕还林工程区主要造林树种生产潜力

This paper assesses the productivity of the main plant species used in a reafforestation project in Datong County in Qinghai Province that restores trees to an area originally cleared to grow food crops for hungry poor people. As incomes rose, both the local people, and the nation as a whole, gradually realized that local and regional ecological security is a key to human well-being and the maintenance of civilization. This project is a part of the nationally promoted and locally supported program to plant more trees instead of cutting them down. Datong County is part of the administrative area of Xining City, the capital of Qinghai Province in western China. The annual precipitation of the area is around 450 mm and the altitude ranges from 2280 m to 4622 m. The site of the project is in one of the typical catchments where the total area observed is 376 hm~2 in which 217 hm~2 are forest and 160 hm~2 farmland. The basic topography of the site is formed of hillslopes separated by a seasonally-flowing river. The project aims to replant with indigenous species that have been shown to grow better than others in this area. Using the available, but incomplete statistics and official records, together with field counts and surveys by graduate students, we identified several common species of shrubs, needle-leaved tress and broad-leaved trees. From agricultural productivity theory, with certain modification employed in models, we calculated the productivity of the main plant species under different conditions. The first calculation examines the theoretical productivity of main species making full use of the present climatic resources. The second is the utmost possible productivity using currently available technology. The third is the real productivity under present managerial techniques. By analyzing climatically feasible, present and practical potential productivity of the main forest species in the area, clear goals for the locality were established. The gaps between climatic, present and practical potential forestland productivity were then examined to determine the prospects and opportunities for further productivity improvement, leading to suggestions on changes to afforestation techniques and management. In terms of using present climatic resources, the choice of suitable plant species is the key to success. With regard to present and practical potential forest species productivity, the local shrub Hippophae rhamnoides L. is better than Berberis thumbergii DC. IN needle-leaved trees, Larix gmelini Rupr. and Picea purpurea are better than Picea crassifolia. Among the broad leaved tree species, the Populus cathayana Rehd. is better than Betula platyphylla Suk.. The order of species choice for planting is therefore: Picea purpurea, Larix gmelini Rupr., Populus cathayana Rehd., Betula platyphylla Suk. and Hippophae rhamnoides L. However, when present managerial and technical conditions are considered, the suggested order of species is: Populus cathayan