花棒液流变化规律及其对环境因子的响应

在西北干旱沙区,采用茎流热平衡技术对花棒主茎、一级分枝和二级分枝液流进行研究.结果表明,在整个生长季内液流速率日变化曲线峰型表现各异,但在短时间段内其液流速率日变化有较强的规律性.主茎和一级分枝液流速率的曲线在生长季中期出现了剧烈动荡,在生长季末期到达最大值后同一数值维持较长时间;二级分枝的液流量在生长季初期出现了“昼低夜高”、生长季中期的液流量低于6、9月份液流量;主茎和一级分枝单日液流量的最大值出现在7月份,分别为5 781.6 g和3 180 g,二级分枝的最大值出现在9月份(480 g).日液流量大小依次为主茎>一级分枝>二级分枝,而液流通量在整个生长期内表现比较复杂.通过对同时观测的气象因子的分析,表明在整个生长季影响花棒液流速率的主导因子是土壤含水率,而在一个较短的时间段内,光照强度、气温和水汽压亏缺则是影响花棒液流速率的主导因子.

Sap-flow Pattern and its Responses of Hedysarum scoparium Fisch.et Mey.to Environmental Factors

The sap-flows of main stems and primary and secondary shoots of Hedysarum scoparium Fisch.et Mey.were examined by Stem heat balance(SHB),which showed that the rates of the sap flows daily varied without following a certain pattern during the whole growing season following a clear pattern during a short growing time.The sap flow rate of main stems and primary shoots appeared to sharply fluctuate in the middle growing season,and reached their peaks in the late growing season and maintained peaks at the same values for a longer time;The sap-flow flux of secondary shoots appeared "low in daytime and high in nighttime" and the sap-flow flux in the middle growing season was below those in June and September;the daily sap-flow fluxes of main stems and primary shoots peaked in July reaching 5 781.6 g and 3 180 g respectively,and that of secondary shoots peaked in September(reaching 480 g).The daily sap-flow flux increased in the order of main stem,primary shoot and secondary shoot,but the daily sap-flow fluxes appeared to vary in a complicated manner during the whole growing season.The analysis of the data about meteorological factors observed at the same time revealed that soil moisture is the dominating factor affecting the sap flow rate of H.scoparium during the whole growing season,but sunshine intensity,temperature and water vapor pressure deficit were the dominating factors affecting the sap flow rate of H.scoparium in a short period of time.