中文摘要：

【目的】具有重要的木材生产与生态功能的兴安落叶松分布于我国夏季干旱强度和频度明显偏高区域,研究兴安落叶松自然干旱过程中水分指标特征,以期阐明该种水分应对策略。【方法】以自然生长的兴安落叶松为研究对象,在2012年5—9月生长季,于帽儿山森林生态系统定位研究站兴安落叶松人工林内进行了减雨100%、减雨50%和对照试验,测定不同减雨条件下兴安落叶松枝条水势、针叶气孔导度、相对含水量,分析压力-容积曲线水分参数。【结果】测定期间兴安落叶松枝条中午水势由低到高依次为减雨100%、减雨50%、对照。减雨100%、减雨50%和对照兴安落叶松枝条中午水势季节变幅依次为0.81,0.68和0.54 MPa,前两者与对照样木中午水势之差最高值分别为0.49和0.37 MPa。3个处理样木枝条清晨与中午水势之差保持基本稳定,均约为0.71MPa。减雨100%和减雨50%样木针叶气孔导度较对照下降84%和79%,水分利用效率较对照升高140%和58%。减雨100%和减雨50%样木枝条相对含水量相似,平均较对照低7%。不同处理样木压力-容积曲线主要水分参数保持相对稳定。【结论】短期干旱处理后,兴安落叶松能够通过降低气孔开度,提高水分利用效率,自身进行一定程度的渗透调节,保持相对稳定的清晨中午水势梯度和相对含水量。在等水/非等水行为连续体中,兴安落叶松具有近等水行为特征。

英文摘要：

【Objective 】 Larix gmelinii plays a vital role in economic development and ecological environment construction in China,however it distributes in the region where summer drought intensity and drought frequency are high.Thus,it is necessary to clarify the water management strategy. 【Method】A rainfall exclusion experiment including three water regime treatments（ 100% rainfall exclusion- 100% RE,50% rainfall exclusion- 50% RE,and control- CK,i. e.,ambient rainfall） was conducted in Dahurian larch plantations from May to September 2012 to monitor the water relations of trees including water potential,stomatal conductance,relative water content,and pressure-volume water parameters in a natural environment at Maoershan Forest Research Station,Northeast Forestry University. 【Result】The midday water potential was lowest for the 100% RE treatment,followed by the 50% RE treatment,and the highest for the CK during the experiment period in which the decreasing precipitation directly led to a substantial reduction of soil moisture. The seasonal variation amplitude of midday water potential for 100% RE,50% RE,and CK was 0. 81,0. 68,and 0. 54 MPa,respectively. The greatest difference in midday water potential between 100% RE,50% RE and CK was0. 49,and 0. 37 MPa,however the differences between predawn water potential and midday water potential for the three treatments were all similar,averaging about 0. 71 MPa. The highest percentages of decrease in stomatal conductance for100% RE and 50% RE were 84% and 79%,and the highest percentages of increase in water use efficiency（ WUE） for100% RE and 50% RE sample were 140% and 58% compared with the control. Moreover,the relative water content（ RWC） of twigs for 100% RE and 50% RE was similar,and was 7% lower than that of the control. In addition,the main water parameters derived from pressure volume curves for the three treatments were similar,suggesting that the parameters were relatively stable in response to the decrease of soil water content. 【Conclusion ?