Monitoring mortality in a semiarid forest under the influence of prolonged drought in Zagros region

Abstract

Climate change and exacerbation of drought stress during recent decade cause forest mortality phenomenon and threatening existence of forests worldwide. This study was conducted to assess the forest decline trend and associated factors through remote sensing technique and field measurements during 6 years (2012–2017) in Zagros forest in the Kalehzard, Kermanshah, Iran. Precise coordinates of dead trees were recorded annually, and points were checked with satellite images. Results indicated that reductions in winter precipitation by about 37 mm and long-term frost days by about 10 days, and adversely increased air temperature by 0.14 °C corresponded with 20% reduction in tree density. Dead tree rate over study period on northern and southern slopes was 18.8% and 31.1%, respectively, with a significant higher rate being detected in southern slope (P < 0.05). Highest and lowest decline rates were 8.8% in 2014 and 1.1% in 2017. Then, decline in two dominant northern and southern slopes was about 19% and 31%, respectively, which was significantly higher in southern slope. It was concluded that drought stress caused physiological weakness in plants promoting pest and disease damages and eventual emergence of a forest decline phenomenon, the severity of which is associated with both factors and human activities.