京西山区人工林水分参数的研究（Ⅰ）

应用ＰＶ技术研究了京西山区油松、侧柏、白皮松、栓皮栎、元宝枫、刺槐及火炬树等７个树种人工林水分参数ψｗ￣（ｔｌＰ）（膨压为零时的渗透势）、ψｓ￣（ｓａｔ）（饱和含水量时的最大渗透势）及ψｗ（叶水势）的季节变化。研究表明：①在自然条件下，树木叶水势的季节变化主要决定于土壤水分状况的好坏，因而它是反映土壤水分季节变化规律及树木受旱程度的良好指标，②供试树种的水分参数ψｗ￣（ｔｌＰ）和ψｓ￣（ｓａｔ）都有其季节性变化规律，这种变化规律主要与树木的物候特点有关，而与土壤水分状况没有明显的关系，②在一个生长期内，树木展叶和嫩枝生长的春季和夏初，是树木耐旱能力最弱的时期，重点研究这一时期树木的耐旱特点具有十分重要的意义。④在维持膨压的能力方面树种之间的差异是十分明显的，其中针叶树种明显强于阔叶树种。依据ψｗ￣（ｔｌＰ）的年均值来比较树种耐旱能力的大小，其顺序由强至弱为侧柏、白皮松、油松、栓皮栎、元宝枫、火炬树、刺槐，这一结果与野外的实际观察相吻合，也与苗木耐旱性的研究结果基本一致。

A Study on Water Parameter of Plantation in the WesternMountain Area of Beijing, China (Ⅰ)

The water parameters ( and ) and water potential()in plantation of Pinus fabulaeformis, Platycladus orientalis, Pinus bungeana.Ouercus variabilis, Acer truncatum, Robinia pseudoacacia and Rhus typhinaare studied using Pressure-Volume technique in this paper. The results show,( 1 ) under the nature condition, the seasonal change of in tree speciesexamined is mainly determined by amount of soil water. Thus, is a soodindicator which reflects the regular pattern in the seasonal change of soilwater and the degree subjected to dry in tree species; (2)there is a seasonalchange of water parameters in all trees examined. This change is relativeto the phenological characteristics of species; (3) in a growth period,trees are of the weakest ability of drought tolerance in spring and earlysummer when young branches and leaves are growing; (4) a difference inmaintenance of turgor among the tree species examined is very clear,needle-leaved tree is stronger than broad-leaved tree amony them. Accordingto annual average value of ψw￣(tlP), the drought tolerance ability of the treesexamined is arranged from strong to weak as P. orientalis, P. bungeana.P. tabulaeformis, Q. varibilis, A. truncatum, R. typhina and R. pseudocacia.This arrangement correspondes to field reality, and also is identical withdrought tolerance of seedlings.