جستجوی مقالات مرتبط با کلیدواژه "روش های فاصله ای" در نشریات گروه "جنگلداری"

One of the basic parameters in forest management is the detailed knowledge of the trees’ growing stock for planning, which is operational by forest inventory. Excessive human interference and dependence on the forests have changed their natural structure. Although the circumstances of wood harvesting are not provided in these forests, their role is essential in soil and water conservation, the livelihood of local people, and environment improvement. Sampling methods must be accurate, inexpensive, and easily implementable in the wild. This study presents a new sampling method, called a branching transect, in the Iranian Zagros forests and similar forests. Features of the new method include proper accuracy, easy implementation in nature, simplicity of statistical calculations, and low cost. The number of trees per hectare (density) in a forest stand represents the existing situation, and its monitoring is very important to know the changes in forest stands. The use of distance sampling methods, especially in open forests, has grown in recent years due to the reduction of inventory costs and optimal accuracy. The research mainly aims to evaluate the efficiency of a proposed distance method (a branched sampling line) with easy implementation and good accuracy in a 100 × 100 m network and the GIS environment.

The studied area is located in the southwestern part of the Manshet and Qalarang protected area in Ilam County. First, 100% inventory was applied in a 90-hectare area of the studied forest, and then 10 and 20-m sampling lines with branches of up to a maximum of 20 m (90 sampling points) were used for this study. In this method, a transect is used that includes some sub-transects. The length of the main transect, sub-transect, the number of trees measured in each sub-transect, and the number of sub-branches in this method are changeable based on the homogeneity, heterogeneity, density, and structure of the forest and are determined according to the forest and expert opinions. In general, less numbers of sub-branches and trees can be considered when the forest is denser or more homogeneous. It is better to consider more sub-branches in dense forests, such as Zagros forests so that a wider area can be covered under inventory and an acceptable number of trees can be examined in transects. Due to the density and heterogeneity of the studied forest area, 20-meter transects with 2, 4, and 6 sub-branches were used in this study. To reach the study goal of the comparison among distance sampling methods, the results of these samplings should be compared to a real amount to have the final judgment on their benefits and weaknesses. Accordingly, the results were compared to 100% inventory in the study area. In 100% inventory, geographical features and the measured quantities for each tree were entered into the GIS environment. This research is the first to use the sampling method of a sample line with 2, 4, and 6 m lateral branches. To evaluate the methods, they compared with 100% inventory based on the accuracy rate and t-test.

The normality of data was tested through the chi-square test, and the unpaired Student`s t-test was used to compare the average numbers and canopy of trees in a hectare, resulting from real amount sampling (100% inventory). Based on the whole amount of trees in the area (12079( and the whole area of the canopy of trees (62.32 m2), the real average amount of trees per hectare and the real average value of the canopy area per hectare were calculated as 141 and 3704, respectively 12). The 6-branched two-tree sample line with 141 trees per hectare and the four-branched one-tree sample line method with a canopy of 3815 m2 per hectare showed the best results compared to the real mean. The analysis showed that most of the used sampling methods  (the branched sampling line with six different patterns 6b2t- 6b1t- 2b1t- 2b2t- 4b2t-4b1t) yielded acceptable results for the evaluation of open forests. However, the branched sampling line method in most networks showed a lower statistical error and was closer to the real value in terms of the mean number of trees per hectare.

Totally, the branched sampling line has an accuracy percentage within 10% to estimate the number of trees per hectare in most networks. In terms of the mean number of trees per hectare, this method was not significantly different from the actual value with a probability of 95% and was more accurate than the other distance methods tested in this research. Considering the low percentage of sampling errors, acceptable accuracy, and easy implementation in nature, the branched sampling line was evaluated as a more suitable method than the other approaches. Due to the novelty of the presented sampling method, there was no case for comparison, in other words, transect branching has not been applied in other areas that can be compared with the results of this study. Finally, the results of this review for the parameters of the number and area of canopy of trees per hectare and its comparison with the actual value and flexibility of this method (changeability of the number of branches, number of trees in each branch, and the length of the main and sub-transects) demonstrate that it is a proper sampling method in dense and even normal forests.

Spatial pattern is an important parameter in ecology of forest communities. Lebanon oak (Quercus libani Oliv.) as a native species covers 24% of northern Zagros forests. Quercus libani plays a significant role in ecological and social conditions of local people. Hence, the present study was conducted to investigate the spatial pattern of this oak species based on T-square sampling in Belake forests, northern Zagros. For this purpose, a 40-ha area was inventoried based on distance method. Systematic- random method with 25×25 m2 plots was used for inventory. A total of 43 random points with 100m distance were determined. Eberhardt, Hines, Hopkines, C index and Index of dispersion were used for dispersion pattern and the results were tested at 5% level. Eberhardt's index, Hines, Hopkines and Index of dispersion showed disperse pattern, while C index indicated clump pattern. But only Eberhardt's index result was significant. Our results can be applied as a useful tool in developing the management programs, afforestation and reforestation programs in order to protect the endangerd ecosystems.

Distance sampling methods are a group of commonly-used methods in estimation of quantitative characteristics of forest, although each method and related estimators have different efficiencies due to different factors (such as environmental conditions, stand density, and distribution of trees). Therefore, it seems necessary to know how these methods operate in open forests regarding to their importance and their role in estimation of quantitative characteristics with low cost and time. The objective of this study was efficiency assessment of 12 important distance sampling methods to obtain biometric characteristics of wild pistachio trees (density and canopy closure) in Zagros open stands. This study investigated the distance methods in two single- and multi-distance groups. Moreover, it was aimed to select the appropriate estimator of each method and the efficiency of these methods were compared in the same conditions.
A wild pistachio stand with low density (19.44 trees ha -1) was selected in Bane Research Site, Firoozabad, Fars province, south western Iran. Using a 100 m × 100 m mesh, 46 sample points were located within the boundary. Six single-distance and six multi-distance sampling methods were applied to estimate the characteristics. Root mean squared error was applied to evaluate the precision and accuracy criterion and comparing the means using one-sample t-test were implemented to assess the accuracy of the results.
Using precision and accuracy criteria, the appropriate estimators were identified in nearest individual ( Cottam et al. ) , nearest neighbour ( Cottam and Curtis ) , and T - square ( Byth ) single - distance methods and point - centered quarter ( Cottam and Curtis ) multi-distance sampling method. To estimate density and canopy closure, nearest individual ( Cottam et al. ) and nearest neighbour ( Cottam and Curtis ) single - distance methods were the most efficient ones. Between multi - distance sampling methods, Byth and Ripley ( accuracy of 3.70 % and p In general , nearest individual and nearest neighbour single - distance methods were efficient enough to estimate the biometric characteristics of wild pistachio trees in the studied open stand precisely and accurately. The effect of sampling network and distribution of trees can be investigated in future studies.

One of the main components of forest stand structure is spatial pattern and positioning of trees next to each other. Stand’s spatial patterns are measured and mapped by measuring tree locations in the stand and entering each coordinates into analytical frameworks. The aim of this study was to compare K-Ripley and distance indices in order to determine spatial pattern of Quercus Brantii in Choghasabz forests of Ilam. Using systematic-random sampling with 100×100m dimensions, 53 samples were selected. K-Ripley index and Hopkins, Hinez, Eberhart and C distance indices were used to analyze the spatial pattern in the area. Results of K-Ripley index showed that spatial pattern of oak trees in the study area are random pattern. But the results of Hopkins, Hinez, Eberhart and C distance indices showed a clumped pattern for Quercus brantii in the study area.

Understanding the distribution of plant spatial pattern is useful for explaining the ecosystems stability, designing proper management plans, and preservative and reforestation operations. Considering the importance of the northern Zagros forests in terms of socio - economic, protection and reforestation, and given that most research which has been done on the spatial patterns in the Western forests of the country focused on the even-aged coppice forests, the woody species spatial pattern in Havare–Khol forests of Baneh city, governed by a combination of both even-age (on the tree) and uneven-aged forests (on the ground), was studied. In this research, using the randomized-systematic method and 200×300 m inventory network, sixty sampling points were measured by the nearest individual, T-square and compound methods. Data analyses were accomplished by the distance methods of Johnson and Zimmer, Eberhart, Hopkins, Hinez and C index, using of Ecological Methodology software. Results showed the clumped pattern for Johnson and Zimmer, Eberhart and Hinez, the clumped pattern towards the random patterns for C index, and the uniform pattern for Hopkins indices. The clumped tree spatial pattern in Havare-Khol forest was totally determined. The results generally illustrated that based on some indices, taking distance the tree spatial pattern in Havare-Khol forest from natural condition was mainly related to the major jobs of forest dwellers, animal husbandry, and their activities (pruning and cattle grazing etc.)

In order to have a better recognition of plant communities, studying the spatial pattern of them is necessary to understand many of the issues in forest ecology and management. This study was conducted in Bayangan in Kermanshah province, as a part of Zagros forests. Sampling methods including fixed area plots and distance methods, such as T-square and Compound sampling, were used to investigate the spatial pattern of Manna Oak trees (Quercus brantii Lindl.). A grid of 100 m×100 m was applied and then 50 sample plots were established. The grid intersections were applied as the center of sample plots and the beginning of distance sampling techniques. Dispersal indicators such as Green, Morisita, Standardized Morisita, Johnson and Zimmer, TF, TN, Hopkins and C were used to analyze the spatial pattern. All of the applied indicators showed a clumped pattern for Quercus brantii. Among the distance indicators, TF, TN and C, presented better results than the other indices.