植被的降雨分配作用对理解生态系统的水文功能具有重要的意义。该文对四川岷江上游岷江冷杉(Abies faxoniana)针叶林和川滇高山栎(Quercus aquifolioides)灌丛两种生态系统的降雨分配及降雨截留的影响因素进行了研究，探讨了植被分配降雨及截留降雨的影响机制和影响因素。文中采用定位观测的方法研究降雨分配。针叶林中冠层降雨截留占33.33%，树干茎流占0.07%，穿透雨占66.60%；而灌丛的冠层截留降雨为24.95%，穿透雨为75.05%；针叶林地被物的蓄留水能力(1.746 mm)要大于灌丛地被物的持水能力(0.941 mm)；针叶林土壤的容积含水率(39.66%)也要高于灌丛土壤的容积含水率(38.19%)；两种生态系统中的穿透雨率与降雨量的关系均可用逻辑斯谛方程较好地模拟。文中还选取了降雨量、降雨强度、降雨持续时间、两次降雨的间隔时间和次降雨期间的气温等5种因子分析影响两种生态系统降雨截留的主要因素。根据截留降雨与上述5种因子的偏相关分析结果：针叶林冠层的降雨截留主要受降雨量、降雨持续时间和间隔时间的影响；灌丛的降雨截留主要受降雨量、气温与降雨持续时间的影响。文中从当地的降雨特征与两种生态系统微气候差异的角度分析了两种生态系统降雨分配及降雨截留影响因素差异的原因。
Background and Aims Ecosystems in western Sichuan Province are diverse, and their hydrological functions are important to the ecological stability of the upper drainages of the Yangtse River. It is important to study rainfall redistribution by vegetation in this area to understand the hydrological functions of ecosystems. We studied Abies faxonianaconifer forest and Quercus aquifolioides shrubland in the Dengsheng subalpine dark coniferous forests positioning research station in the upper catchments of Minjiang River, Sichuan. Our objectives were to: 1) determine the magnitude of canopy layer interception, stem flow and water holding capability of ground litter and soil and 2) analyze factors that influence rainfall interception.
Methods We studied rainfall redistribution in the ecosystems from July to September, 2001 and June to August, 2002. We measured total rainfall with one standard and two automatic rain gages, throughfall with eight randomly placed barrel gages (30 cm diameter and 40 cm height) in the forest ecosystem and four in the shrub ecosystem, stem flow of trees in the forest ecosystem but not in the shrub ecosystem, and microclimate in both ecosystems and on open ground outside of the forest. Pearson correlation and partial correlation methods were used to analyze five factors influencing rainfall interception: rainfall volume, rainfall intensi ty, duration of single rainfall events, time interval between consecutive rainfa ll events and average air temperature during individual rainfall events.
Key Results In the forest ecosystem, canopy rainfall interception accou nted for 33.33% of the total rainfall, stem flow 0.07% and throughfall 66.60%. For the shrubland ecosystem, rainfall interception accounted for 24.95% and throughfall 75.05%. Water holding capability was larger for conifer forest ground litter including lichens (1.746 mm) than for shrubland ground litter (0.941 mm). Bulk moist ure content was larger for conifer forest (39.66%) than shrubland (38.19%). The relationship between throughfall percentage and rainfall could be modeled with a logistic equation.
Conclusions Interception in the conifer forest was mainly affected by rainfall volume, duration of rainfall and time interval time between consecutive rainfall events. For the shrubland, interception was mainly affected by rainfall volume, duration of rainfall and temperature. Differences between rainfall redistribution and factors affecting rainfall interception are analyzed and discussed in relation to local rainfall characteristics and microclimate differences between the two ecosystems.