Rainfall interception by a Fraxinus rotundifolia stand in a semi arid climate zone of Iran

Interception loss (I) plays an important role in forest stand, but not well quantified in Iran. I and throughfall (TF) were measured over a four month period by a Fraxinus rotundifolia afforestation in the Chitgar Forest Park, near Tehran, Iran. Mean annual air temperature and precipitation are 17.1˚C and 269 mm, respectively. The gross rainfall (GR) was measured by the mean of ten rain-gauges placed in an open area neighboring to the stand. Thirty rain-gauges were installed beneath the canopy cover to average into TF. I was calculated as the difference between GR and TF. Cumulative GR for 22 rainfall events was 91.5 mm. Cumulative I during the measurement period for F.rotundifolia were 16.1% corresponding to the mean net rainfall loss of 14.7 mm. F.rotundifolia in leaf (LP), and leafless periods (LLP) intercepted 21.1%, and 8.8% of GR, respectively. On the event-based (each GR), average I:GR in F.rotundifolia within LP, and LLP periods were 24.6%, and 9.7%, respectively. Negative logarithmic correlations were observed for LP (r2=0.62), and LLP periods (r2=0.19). Our results confirmed the importance of tree canopies as source controls capable of treating by reducing the runoff component within hydrological cycle. Rainfall interception should be considered when selecting species for afforestation projects in a semi arid climate zone as it can be noteworthy.

Afforestation, Fraxinus rotundifolia, Rainfall interception, Semi arid climate.