جستجوی مقالات مرتبط با کلیدواژه "عوامل فیزیوگرافیک" در نشریات گروه "جنگلداری"

The main objective of this study was identifying Box trees (Buxus hyrcana Pojark.) communities and survey of their relationships to some physiographic attributes and plant biodiversity indices in Khybus Protected Area which is one of the best and most virgin Habitats of Box trees in Hyrcanian forest. The field data were obtained in 65 sample releves in a systematic- selective design (200 × 400 meter) by consideration Braun- Blanquet indicator stands concept. Physiographic attributes and plant biodiversity indices were also recorded in each releve. Vegetation data were analyzed using TWINSPAN. The data were classified into six plant communities. The results of ANOVA showed that these plant communities reflected underlying differences in altitude, northness, slope, richness and pielou evenness. Then Plant communities were ordinated using DCA from basis of diagnostic plant species percentage cover and the correspondence scores of the two first axes, which have explained the 25.5% of total variation changes in floristic data. The correlation between plant communities with environmental factors and plant biodiversity indices were determined by Pearson correlation coefficient. The DCA ordination showed that each plant community has its own range and are separately distributed. Also the first DCA axis was associated with the altitude, northness, richness, Shannon- wiener diversity and Pielou evenness among the communities, while the second one showed significant correlation with the slope gradient among the communities.

Different ecologic factors influence on forming, development and sustaining of the plant communities, among which physiographic variables are the most important ones. The aim of this study was to identify forest types and effect of physiographical factors such as sea level height, slope and aspect of the site on quantitative characteristics of forest types in 2nd district of Vaz Forest with area of 847.5 ha in Chamestan city (Mazandaran Province). The field data were collected in 256 plots. Inventory grid was designed by a random-systematic method with dimension of 150×200 meter and sample circle plots with radius of 17.84 meter. In each sample, some of quantitative tree factors e.g., diameter breast height and control trees height were recorded. In order to recognize the type, total surface average equal to trees basal area in sample plot and Two Way Indicator Species Analysis (TWINSPAN) were used. Forest stands were grouped into seven forest types. In order to compare forest types and the role of physiographical factors on their quantitative characteristics, ANOVA and Duncan tests and Spearman correlation coefficient were used. The results showed that forest types are not only different in floristic characteristics but also in physiographic characteristics of sites. Other results also showed that the 6th forest type has minimum mean of basal area, volume and height of the control trees. It was also found that there were significant differences between mean of basal area and mean of volume, mean of regeneration and vegetation cover and mean of control trees height with geographical directions and sea level height, slope percent of the site and sea level height, respectively. It is notified the category of the sea level height (1200-1600 m) was recognized as an optimal condition for Beech stands (Fagus orientalis Lipsky.).