The impact of rainwater harvesting on improving the condition of Iranian Oak declined trees (Case study: Chavar forests of Ilam province)

Severe drought stress restricts the growth of plant species such as oak trees and at the onset of weakness, invasion of pests and diseases and ultimately death is inevitable. The use of rainfall storage techniques provides the water needed for plant growth in the soil. This study aimed to examine the possibility of using two small water catchment (Linear terrace and Crescent pond), to cope with the critical conditions of oak forests, located in Chavar section of Ilam province; comparing to the control (without storage) in a randomized complete block design. Before running the storage systems, trees characteristics, as well as soil and moisture content were measured and during the 4-year period, monthly soil moisture and health status of the trees were recorded. Experimental results showed that soil moisture decreased in proportion to the amount of rainfall in the low season, so that in hot months, the moisture loss crisis reaches even more than one meter deep. Comparison of mean soil moisture changes showed significant effect of rain storage methods on soil moisture content by 21% in linear banquet method and 39% in crescent banquet method. Evaluation of the degree of vitality and health of the trees showed that there was a significant difference between the treatment of rainfed storage and the control treatment at 95% confidence level, indicating the positive effect of the rainfed storage on the health of the trees. Therefore, the use of water catchment systems to store the precipitation is recommended to increase soil moisture and improve the health and vitality of the declined trees.