جستجوی مقالات مرتبط با کلیدواژه "نزدیک ترین همسایه" در نشریات گروه "محیط زیست"

The first step in proper management of forests is having enough information about growth, development and how the forest stands structure are influenced by environmental factors. Considering the importance of forest stands in the north country and environmental values of the study area, structure of the existing species in Dashtenaz forest protected area in Mazandaran province has been investigated using the nearest neighbor indices. To investigate the structure of the study area, 56 hectare of the forest stands were statistically analyzed, and Clark and Evanes, Uniform angles, Shannon-Wiener, Mingling, DBH dominance and DBH differentiation indices were used to investigate the structure. The results showed that the mean Clark and Evans and uniform angles indices were 0.70 and 0.55 respectively, indicating a distribution between random and cluster patterns. Mean indices of Shannon-Weiner and Mingling were 0.40 and 0.06 respectively. Knowing that the study area is mostly composed of oak, the Mingling index value was calculated to be low​​. The mean DBH dominance index was calculated as 0.50, indicating the dominance of DBH of Quercus Castaneifolia and recessivity ofUlmus Glabra. Zelkova Carpinifolia was medium in terms of DBH dimension. Also average DBH differentiation index was calculated as 0.32, representing a medium difference between the trees next to each other in terms of DBH dimension. The indices used in this study can be used to describe the structure and ecological property of different species of trees.

Considering the importance of forest structure and interaction among different tree species, this study conducted aimed to determine and compare spatial pattern, heterogeneity, and dimensions of Hawthorn and Maple trees with other neighbor trees. For determining Hawthorn and Maple trees structure, 30 individual of each trees were identified and studied. Based on the results, uniform angle index for Hawthorn and Maple trees were 0/744, and 0/733 respectively, which would propose a clumped pattern for these two species. Computed mingling index values for Hawthorn and Maple were 0/877 and 0/955 respectively that show a high tree species mixture. Also, the average of crown canopy differentiation and crown canopy dimension were 0/582 and 0/322 respectively, for Hawthorn tee and it was 0/42 and 0/656 respectively for Maple tree. Based on mean values, these results show that Hawthorn had high level of differentiation but was inferior in comparing to its neighbors; whereas Maple has intermediate differentiation and is dominant to the other neighbors. The average distance to nearest neighbors for Hawthorn and Maple were calculated 7/374 and 6/278 respectively. The results of an absolute discrepancy algorithm (AD) showed a high differentiation of Hawthorn and Maple mixture in comparing to the other indices. It is concluded that maple is superior to hawthorn in dimension and because of low frequency of these two species, they hold high values of mingling indices.