SPAC中油松栓皮栎混交林水分特征与气体交换

20 0 1年 4— 10月 ,通过林内标准地观测的方式 ,对北京西山地区一块 3 1年生的油松栓皮栎混交林的水势 (用压力室测定 )日变化、净光合速率和蒸腾速率 (用Licor 640 0测定 )日变化过程进行测定 .结果表明 ,在土壤 植物 大气连续体 (SPAC)系统中 ,生长季内水势的波动幅度按从大到小的顺序是大气 >植物 >土壤 ,其中大气水势的绝对值要比植物和土壤水势高 1～ 3个数量级 .土壤、植物和大气水势的日变化规律类似 ,并表现出明显的季节差异 .在生长季不同标准日内 ,油松和栓皮栎的净光合速率和蒸腾变化规律差异较大 .通常 ,栓皮栎的净光合速率和蒸腾速率明显高于油松 ,但在水分胁迫时 ,二者的差异会减小 .在生长季中的绝大部分时段 ,树木由于环境因子特别是土壤水分的限制作用不能达到其潜在的光合和蒸腾能力

Water characteristics and gas exchange of Pinus tabulaeformis and Quercus variabilis mixed stand

From April to October of 2001, a 31_year_old Pinus tabulaefo rmis and Quercus variabilis mixed stand is measured on t he change of water potential (measured by pressure chamber), net photosynthetic rate and transpiration rate (measured by Licor 6400) in a day in western mountai nous area of Beijing. The results show that the order of water potential ch ange range in growing season is: atmosphere > plant > soil, and the water potential of atmosphere is 1～3 orders of magnitude more than that of plant and soil. The change patterns of the water potential of soil, pla nt and atmosphere in a day are similar, and it is obviously different in differe nt seasons. In different standard days of growing season, the change patterns of n et photosynthetic rate and transpiration rate of Pinus tabulaeformis and Quercus variabilis are markedly different. In general, th e net photosynthetic rate and transpiration rate of Quercus variabilis are distinctly higher than those of Pinus tabulaeformis. Under the condit ion of water stress, the difference of the net photos ynthetic rate and transpiration rate between Pinus tabulaeformis and Quercus variabilis decreases. In most time of growing sea son, the production ability of trees’ photosynthesis and transpiration cannot reach their potential because of the restriction of environmental factors, espec ially that of the soil water.