Abstract:
Forest canopy rainfall interception loss (I), canopy water storage (S), and the ratio of
mean evaporation to mean rainfall intensity ( E / R ) are important components of the
water balance in arid and semi-arid climate zones. The goal of this project was to quantify
I and S and to evaluate the Gash interception model for rainfall interception in a mature
semi-arid Pinus eldarica Medw afforestation planted in the Chitgar Forest Park near
Tehran city, Iran. Measurements of gross precipitation (PG) and throughfall (TF) were
recorded on an event basis from September 2009 to April 2010. For the measurement
period, PG totaled 164.8 mm and I totaled 61.2 mm. I was calculated as the difference
between PG and TF. On the event scale, the ratio of I:PG ranged between 0.195 and 1, and
averaged 0.614. There was a strong logarithmic correlation between I: PG and PG (R2
=
0.861; P value≤ 0.01). As the size of rainfall events increased, I:PG decreased. The mean
method estimated S to be 1.8 mm. The Gash model accurately estimated I to be within 1.1
mm of the total measured value. The results demonstrate that intercepted rainfall
represents a considerable portion of PG in P.eldarica afforested regions of the semi-arid
climate zone of Iran where soil moisture is a limiting factor for plant growth and
productivity.
Keywords: Afforestation, Canopy water storage, Iran, Mean method, Throughfall.
