Rainfall components distribution in needle-leaved and broadleaved plantations in a semiarid climate zone (Case study: Shahid-Beheshti Forest Park in Broujerd)

The aim of this research was to measure rainfall components (throughfall, interception, and stemflow) in needle-leaved (Pinus brutia, Cupressus arizonica) and broadleaved (Fraxinus rotundifolia and Platanus orientalis) plantations located in Broujerd Forest Park. The total amount of gross rainfall was measured using three rainfall collectors fixed on an open area neighboring to the chosen trees. In order to measure throughfall, five trees of each species were selected and four collectors were fixed underneath each tree. The amount of interception was calculated based on the difference between throughfall and gross rainfall. In a time-span of six months running from November 2012 to May 2013, 24 rainfall events with total amount of 131.8 mm was measured. The amount of interception was measured as follow: Pinus brutia 46.1%, Cupressus arizonica 50.7%, Fraxinus rotundifolia 49.6% and Platanus orientalis 38.1% of total gross rainfall. Strong positive correlations were observed between total rainfall and throughfall for each kind of species. It was found that throughfall in hardwoods species was more than conifer species and the amount of throughfall in aforesaid masses increased as total rainfall increased. The amount of stemflow for all species was less than one percent of total precipitation. Regarding to importance of rainfall regime in this area, interception and throughfall of each species should be considered with priority of broadleaved in plantation and hydrological modeling process in forest ecosystem.