青海大通退耕还林工程区主要造林树种生产潜力

The potential productivity of the main species used in the Datong reafforestation project on former farmland, Qinghai Province

通过对青海大通退耕还林工程区主要树种的气候生产潜力、现实生产潜力和实际生产力进行研究 ,揭示了该地区主要造林树种在实际存在的气候条件下可能达到的理论产量 ,当前技术经济管理水平条件下所能达到的最高产量 ,现行经营管理条件下所获得的实际产量 ;分析了目前林业的现实生产潜力、实际生产潜力分别与气候生产潜力之间的差距 ,预示了该地区林业的发展前景 ;从合理利用气候资源和充分发挥土地生产潜力角度 ,提出了退耕还林工程建设中优选的树种及其原则 ;指出了不同树种在经营管理水平上的差异及其解决建议。

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 cathayana Rehd., Picea purpurea, Hippophae rhamnoides L., Larix gmelini Rupr., Berberis thumbergii DC., Betula platyphylla Suk. and Picea crassifolia. On the other hand, new management tools should be introduced to care, first for needle-leaved, and then secondly the broad leaved trees, followed by, or planted along with, bushes, especially the species Picea purpurea, Larix gmelini Rupr., Populus cathayana Rehd. and Betula platyphylla Suk. The study offers meaningful and significant ways of implementing the reafforestation of former farmland in this area. The way we have sought appropriate indigenous species for replanting can be replicated elsewhere in China.