Zagros forests have the greatest impact on soil and water protection in western Iran. Despite this, a significant part of these forests, especially in Ilam province, have suffered a lot due to the phenomenon of oak decline. The first and most fundamental thing a person must know when combating this issue is the distribution of these areas in forests. Therefore, using the parameters affecting the decline in the forests of Ilam province and based on fuzzy logic, a map of susceptible to oak decline areas was prepared. In this study, the parameters of temperature and precipitation, slope, aspect, altitude, distance from farmlands, roads and forest density were selected as effective parameters and fuzzy gamma overlap method was used. The results showed that more than 77% of the oak forests in the province are highly and extremely susceptible to the decline. This confirms the need for rapid action to plan and protect these forests. In addition, the fuzzy method is proposed, which is considered as a fast and efficient method in preparing such maps for other areas.
Deadwood is one of the main structural features of forest ecosystems and plays an important role in the nutrient cycle, in maintaining production and environmental heterogeneity, and acts as an indicator for assessing the biodiversity of forest ecosystems. This research was conducted with the aim of evaluating the quantitative and qualitative characteristics of deadwood according to the influence of forest accessibility indicators in a comparison between natural and recreational forests. The studied area was divided into three accessibility classes based on the slope gradient range, the slope direction towards the nearest road, the road type, and distance from the road. These classes were: Easy-recreational forest (RE-F), Medium-natural forest 1 (NA-F1), and Difficult-natural forest 2 (NA-F2). In each accessibility class, three transects (750 × 50 m) were established, and three deadwood groups (snag, log, and stump) were recorded along the transects and their volume was calculated. The results of the analysis of variance show that accessibility has a significant effect on the presence of deadwood. The number and volume of snags, logs and dead stumps per hectare was higher in NA-F2 than in NA-F1 and RE-F. In each of the investigated classes, logs and stumps had the highest and the lowest number and volume of deadwood per hectare, respectively. The snag longevity index (= log volume/snag volume) decreased with accessibility. NA F2 showed the greatest value, while REF and NA F1 were not significantly different from each other. The results show that decay classes DC2 in NA-F2 and DC3 in NA-F1 and RE-F had the highest percentage of decay frequency. Finally, the forest accessibility indicators have a significant effect on the quantity, quality and distribution of different groups of deadwood in the forest. This is related to the collection of deadwood by local people who remove deadwood with different levels of intensity.
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