بومشناسی جنگلهای ایران (May 2024)
Comparison of Height Distribution Functions of Brant\'s Oak (Quercus Brantii Lindl) in Two Sites with Vegetative Forms Coppice with Standard and Standard with Coppice
Abstract
Extended Abstract Background: Sustainable management and fundamental planning of forest resources require efficient and high-quality information about the current and future states of forests. Investigating the current and future states of forest stands, describing the structure of the forest stand, and the response of the stand to tending operations are among the capabilities of statistical distributions in forest management. Frequency distribution modeling is the distribution of people in a population in different classes. Since natural phenomena include continuous and discrete types, their distribution will also be different and diverse. The use of statistical distributions in the forest has a long history, and some researchers have considered its history as long as two centuries. Zagros forests, as one of the most important vegetation areas of Iran, have a special importance from the socioeconomic and ecological points of view. The dominant species of these forests is the Iranian oak (Quercus brantii Lindl). According to geographical and environmental conditions, this species has various habitats in the vegetation zone of the middle Zagros. It is expected that this species has different probability distribution functions in different habitats. Therefore, the probability distribution functions of the characteristic height in habitats with different vegetative structures of Iranian oak in the forests of Khorramabad city were investigated in this research to select the best models in different habitats. This study also seeks to provide useful information on the authority of forest managers and planners to preserve and improve these valuable forests. Methods: To carry out this research, two areas with different structures, including coppice with standard (Sefidkoh area) and standard with coppice (Qala-Gol area) were determined in the forests of Khorram Abad city through numerous excursions in the forest. A forest stand with an area of approximately 3 ha was selected in each of these areas. This forest stand was chosen in such a way to represent the forests of the region. The subsoil was semi-deep and north direction in the Qala-Gol forest stand at an altitude of 1850 m above sea level and with an average slope of 20%. In the SefidKoh forest stand, the subsoil was semi-deep and located in the north direction at an altitude of 1900 m from sea level with an average slope of 30%. In each of these two selected forest stands, the height of all Iranian oak trees, with a height of > 1.5 m, was counted 100%. In total, the heights of 458 and 348 Iranian oak trees were measured in the two SefidKoh and Qala-Gol regions, respectively. A TruPulse 360 laser device was used to measure the height of trees. To investigate the distribution of height classes, the most widely used continuous probability distribution models in biological research were used due to the continuousness of the height variable, including two-parameter Weibull, two-parameter gamma, normal, log-normal, beta, and Johnson. The goodness of fit of the data was also examined using the Anderson-Darling test, which has a higher power than other tests. Easy Fit 5.6 software was used to analyze all data and draw graphs. Results: The statistical errors were 4.45% and 2.82% in the Sefidkoh and Qala-Gol regions, respectively. The average height of trees was 6.76 m in the Sefidkoh region (between 1.8 and 18 m) compared to that of 7.54 m (between 1.53 and 14.04 m) measured in the Qala-Gol area. The values of skewness and Kurtosis were positive in the two forest areas, with higher values in the Sefidkouh region than in the Qala-Gol area, indicating the concentration of data in lower-height classes in the Sefidkouh region. The results of Anderson-Darling's goodness of fit test in the Sefidkoh area (coppice with standard) showed that the most suitable probability distribution functions (with a 5% error level) for modeling the distribution of trees in height classes were Johnson sb and beta, respectively. In the Qala-Gol region (standard with coppice), the most appropriate distribution functions were identified as beta and normal, respectively. Conclusion: The results of this research show that the forest has an uneven-aged structure in the areas where the oak forest has a coppice with standard form, according to the form of distribution (decreasing distribution). In contrast, the forest has moved toward a single-stemmed and even-aged forest in areas where the forest form is standard with coppice. This is mainly caused by the destruction through grazing, the cutting of branches for livestock and fuel consumption, and the indiscriminate use of byproducts that have occurred in this region. In the Sefidkoh region, the effects of destruction and less human intervention were observed at the regional level in field observations. According to the shape of the distributions obtained in the two sites, the vegetative forms of the trees affected the distribution functions of their heights, which can provide useful information for managers, planners, and researchers to maintain and control these valuable forests.
