جستجوی مقالات مرتبط با کلیدواژه "تنک کردن" در نشریات گروه "جغرافیا"

Under rapid climate change, desertification, and land degradation, a critical management issue in forests of northern Iran is how to increase forest resilience to wildfires. For decades, forest managers have been employing silvicultural treatments to restore the Hyrcanian forest stand's structure, composition, and diversity, but there is no scientific evidence to support that these treatments reduce the wildfire risk in the area. In this study, based on the wildfire behavior modeling approach using FlamMap MTT, we evaluated spatial relationships between silvicultural fuel reduction treatment (e.g., thinning) and surface and crown burn probabilities in the 6 and 7 Malekroud districts of Siahkal forest. We first analyzed fuel characteristics after the development of silvicultural treatments in the period 2007-2017 in the study area to evaluate low thinning and heavy thinning as restoration tools for similar fuel conditions. Furthermore, we conducted analyses of variance to determine the influence of the silvicultural thinning treatment on surface and canopy burn probabilities. Modeling results at the landscape scale confirm the important role of thinning in the mitigation of crown burn probability (almost 11%) in the study area. However, the effect of thinning on the surface burn probability was not statistically significant (P> 0.05). Comparing the two types of thinning in terms of intensity, heavy thinning had a greater effect on changing the surface and crown (i.e., 10% increase and 39% decrease, respectively, in conifer plantation) burn probability than the low thinning. The modeling approach in the study offers new insights to improve the spatial mapping of wildfire likelihood, include variables sensitive to thinning operation in the models, and provide useful information to prevent extreme wildfire behavior through effective silvicultural treatments.

Silvicultural treatments have been applied in the last decades to broadleaf and conifer plantations to increase resilience by enhancing structural and age-class diversity in northern Iran. The treatments included mechanical thinning manipulations, not followed by surface fuel reduction treatments like prescribed burning. The goal of this study was analyzing  the impact of stand-level silvicultural thinning on landscape-scale wildfire behavior. FlamMap minimum travel time (MTT) fire modeling system was used to simulate the impacts of thinning on fire growth and behavior based on spatial and temporal patterns of historical fire ignitions and associated weather and fuel moisture conditions within a forest landscape. Simulations were done by setting two different fuel moisture scenarios: 1) fuel moisture is fixed as the stands thinned, and 2) fuel moisture is reduced with the same degree of thinning. The results showed that thinning alone can be somewhat effective at mitigating the wildfires; as the landscape proportion with low burn probabilities (BP), conditional flame lengths (CFL), and fire sizes (FS) increases. This trend was not the same at higher values of these parameters. Although fine fuel moisture in thinned stands was lower than in unthinned stands, the fuel moisture difference resulting from stand thinning did not substantially influence fire behavior at the landscape level. The findings of this study can be used for better fire and fuel management and other land-use objectives in fire-prone areas.