集水造林林分水分生产力研究

集水造林通过增加植树带汇流量改善了林地土壤水分环境 ,从而影响到林分物质生产水平。根据不同集水造林密度对林地土壤水分环境的改善程度与林分物质生产之间的关系 (水分生产力 ) ,以“双优”模式标准 ,可以确定出合理的集水造林密度。供试的 5年生和 1 0年生刺槐林 ,分别以小于 1 0 0 0株·hm-2 和不大于 840株·hm-2 为合理的集水造林密度 ,其林木水分生产力分别达到 6 71 4 4g·kg-1和 1 2 1 6 32g·kg-1,符合“丰产理想株型”模式标准 ;林分水分生产力分别达到 8 4 1 0 3kg·hm-2 ·mm-1和 2 1 6 6 46kg·hm-2 ·mm-1,实现了“最佳群体结构”模式标准。在发展“节水”型林业、提高水分利用效率中 ,这种以水分与林分物质生产的关系为理论依据 ,确定造林密度 ,在理论和实践上是可取的

STUDY ON THE WATER PRODUCTIVITY OF THE STANDS AFFORESTED BY WATER-HARVESTING

Afforestation by water-harvesting improves the soil water environment in forest owing to increase of runoff volume collected in the planting strip, so that the productivity of forests is influenced. According to the model of !the double best" and the relationship (the water productivity- WP ) between the present situation of water environment improved and the forest production in the different model of afforestation by water-harvesting (forest density), the rational density of afforestation by water-harvesting has been chosen. With the decrease of forest density, the water amount harvested in the planting strip is increased and the soil moisture in available zone of root system is improved, so that the function curve of tree's water productivity changes from linear to logarithmic upward. When the forest density are respectively 1,000 per hm 2 (in 5 years old ) and 840 per hm 2 (in 10 years old), the relation curve of tree's WP(WP-t) to transpiration is parabolic, which shows that at this moment water is not a limiting factor of production. Namely, the suitable density values of 5 years old and 10 years old black locust forest are respectively 1,000 per hm 2 and 840 per hm 2. Under the suitable density, the WP values of individual tree are respectively 6.7144 g5kg {-1} and 12.1632 g5kg {-1}, which accord with the standards of !the designed individual pattern with high-yield" model, and the WP values of forest are respectively 8.4103 kg5hm {-2}5mm {-1} and 21.6646 kg5hm {-2}5mm {-1}, which can be considered as !the optimum population structure" model. It can be applied in both theory and practice to choose the model of forest based on the relationship between water and forest production in the developing of water-saving forestry and in the improvment of water use efficiency.