Mitigating drought induced-mortality in the semiarid forests through runoff harvesting system; as a short-term adaptation measure

The effects of climate changes are generally expected to reduce the growth and survival of forests, particularly in semiarid regions. This study was conducted to demonstrate the effects of runoff harvesting technique on the reduction in forest tree dieback phenomenon in the Zagros forests, Iran. In order to evaluate this hypothesis, runoff was harvested through the crescent shapedtrench (CST) affecting soil moisture storage. The selected forest site is located in Kalehzard, Kermanshah, in Zagros region, western Iran. The experiment was a randomized complete block design with four treatment plots: trench with protection (T+PT), protection treatment (PT), trench without protection (T-PT), and control treatment (CT). Three years of comparative monitoring explored that dieback rate increased followed by the reduction in the average annual precipitation and worsening temperature conditions. Hence, T+PT treatment led into a significant reduction in dieback rate (37.7 tree ha-1) and re-growing of certain stands (including total 18.0 tree ha-1) compared to CT. Furthermore, our results demonstrated that T-PT contributed to lower level on dieback reduction (6 tree ha-1) revealing the importance of protection measure which is so effective for the built trench. As a result, micro-catchment could provide soil moisture for the enhancement of forest in semiarid regions, such as Zagros areas.