土壤水分变化对长白山主要树种蒙古栎幼树生长的影响

选择长白山红松阔叶林主要优势树种蒙古栎为研究对象，人工控制3种施水量研究蒙古栎幼树形态、生物量效应和光合生理特征对土壤含水量变化的响应．结果表明，不同土壤含水量变化显著影响蒙古栎叶片、枝、根的生物量及其分配格局和叶片光合气体交换特征．水分胁迫改变幼树树冠结构，抑制幼树树高、地径、叶片大小、地上和地下生物量；同时，蒙古栎幼树根冠生物量比随着土壤水分含量的减少显著提高；供水量减少对幼树净光合速率、CO2利用率和碳利用率等特征有显著的负向影响；而叶片气孔导度、蒸腾速率和水分利用率对不同土壤含水量反应较复杂，只在土壤含水量较低时，幼树气孔导度、蒸腾速率明显降低，叶片水分利用率升高，表现出蒙古栎树种是干旱可变植物，长期水分胁迫可提高树种的耐旱能力．

Effects of soil water regimes on the growth of Quercus mongolica seedlings in Changbai Mountains

This paper studied the response of the seedlings of Quercus mongolica,one of the dominant tree species in Changbai Mountains,to the artificially controlled three soil water gradients,including their morphology,biomass and photosynthetic characteristics.The results indicated that various water regimes significantly affected the biomass and its distribution pattern in the leaves,branches and roots,as well as the leaf gas exchange.Under soil water stress,the crown structure changed,and the tree height,groundline diameter,single leaf area,and aboveground and belowground biomass were inhibited.As soil water content decreased,the ratio of belowground and aboveground biomass dry weight significantly increased.Water stress had a negative effect on net photosynthetic rate,CO 2 use efficiency and carbon use efficiency.The responses of stomatal conductance,transpiration rate and water use efficiency to water stress were complicated.Only at low soil water content,the stomatal conductance and transpiration rate significantly decreased,while water use efficiency increased.It was demonstrated that Quercus mongolica was the tree species with variable resistance to drought,and the resistance could be improved by long-term soil water stress.