Quantifying throughfall, stemflow, and rainfall interception in a Fagus orientalis forest and a Picea abies plantation in Siahkal, Gilan.
Rainfall partitioning into throughfall, stemflow, and interception is an important component of the water cycle in tree's ecosystems in forest ecohydrological research. The aim of this research was to compute the throughfall, stemflow, and interception of a natural stand (Fagus orientalis) and exotic plantation (Picea abies) in Siahkal forest (Gilan province). In order to measure the gross rainfall and throughfall, 10 and 50 manual rain-gauges were used, respectively, and stemflow was measured using average of nine individual trees equaled to the stemflow amount of trees. The cumulative percentage of throughfall, stemflow, and interception of F. orientalis stand were 78.2, 10.1, and 11.7%, respectively. For P. abies stand, the corresponding values were 72.1, 4.6, and 23.3%. Paired T-test suggested that rational stemflow (%) of F. orientalis was significantly greater than P. abies (P<0.01; t=3.59). Mean rational interception (I%) of the P. abies were significantly greater than observed for the F. orientalis (P<0.01, t=9.37). The relationship between gross rainfall and throughfall, stemflow, and interception were observed as positive, and Pearson correlation was significant (P<0.01). Since planting a new species caused changes in the quantity of input water (sum of the throughfall and stemflow) to the forest floor, hence rainfall partitioning should be considered for forest management and selection of appropriate species.