The status of dead standing trees in Zagros forest (Case study: Bioreh Forests in Ilam Province)

To determine the amount of dead standing trees in Zagros forest, a forest area (96 ha) of Bioreh catchment in Malekshahi city in Ilam province was selected. A hundred percent or complete inventory in study area was conducted. The results showed that near to 70% of all trees were sprout-origin and about 30% were seed-origin. While Quercus brantii var persica (92.8 %) and Cerategus sp (5.5%) had the highest abundance, Amygdalus sp., had the lowest amount of abundance compared to other species in the study area. The results also showed that the total percentage of standing deadwood was 11.15% which West and South facing aspects had the highest and East and North facing aspects had the lowest ratios of standing deadwoods. Amygdalus sp., Acer cinerascense and Quercus persica species had the most ratios of standing dead trees while Cerateagus sp., and Pistacia atlantica species had the lowest ratios of standing deadwoods. With increasing in diameter classes, the standing dead trees were increasing in the study area so that the ratio of deadwood in the diameter classes 4 and 6 was less than 10 % while in the diameter classes 84, 88, 92 and 112 the ratio of deadwoods was about 35, 100, 37, and 75% respectively. Furthermore, the percentage of standing deadwoods among seed-origin trees was more than sprout- origin trees. Base on the results, the regional drought and precipitation deficit in the last years was the most important factor in causing standing deadwoods.