1- , Faculty of Natural Resources, Guilan University
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Extended Abstract
Introduction and Objectives:Renewable natural resources such as forests have played an important role in human life since the past. The principled and sustainable use of forests requires technical planning. Fundamental and technical planning requires data collection and analysis and obtaining useful quantitative and qualitative information. One of the methods of data collection in forest populations is 100% statistics. The implementation of 100% statistics in large forest areas is rarely implemented due to technical and economic reasons, and in most cases it is used to compare different sampling methods. In the preparation of plans and researches of northern forests, sampling methods with a fixed area are mostly used. Today, different forest sampling methods have been designed and presented, each of which has its own advantages and merits. The use of these methods requires checking and determining the most suitable ones in terms of ease of implementation, time and accuracy. On the other hand, today the industrial forests in the north of the country have become heterogeneous stands due to exploitation in the past. For this type of forests, using the stratification method combined with sampling methods will be useful and effective. In order to plan to increase efficiency, speed of operation and reduce costs, it is necessary to examine and use different sampling methods with fixed and variable areas, including multi-tree sampling. This study is aimed at the effect of forest classification and its combined effect with fixed area sampling method and PRODAN six tree variable area sampling method and comparing the accuracy of estimators.
Materials and Methods:This study was selected in the Safaroud forests of Mazandaran with an area of 176 hectares. The selected areas were measured and recorded using the statistical method of 100% of all the trees in the area (counting limit, diameter equal to chest more than seven and a half centimeters). In order to avoid mistakes and make it easier to perform 100% statistics, the studied area was divided into square pieces with dimensions of 50x50 meters and 704 plotes were placed in the field. Then the trees in each of these parts were measured separately. Prodan's six-tree method was carried out in two stages. The first stage was measured in an unclassified area of 176 hectares with a grid size of 100x100 meters. The second stage of the forest area under investigation using the method of "Neyman" stratification into three stratum in terms of volume inventory including less than 200 cubic meters, between 200-250 cubic meters and more than 250 cubic meters per hectare and based on Prodan's six-tree method was performed using new grid dimensions for each stratum. In this study, the effect of segmentation on accuracy and time was investigated using the criterion (E%2×T). For this purpose, the time required to unload the sample plotes for the necessary measurements inside the sample plot and the time required to travel the distance between the adjacent sample plotes were also calculated and recorded using a stopwatch. The effect of segmentation on accuracy and time was investigated using the criterion (E%2×T).
Results:The results of the comparison of the statistical test between the average of the variables calculated with the statistical methods of 100% (true mean) and six-tree sampling (Prodan) in the first stage without stratification and in the second stage with the implementation of the "Neyman" stratification method It showed that there is a significant difference at the level of 0.05%. The results of this study in terms of accuracy and cost index (E%2×T) show that the error and statistical error of the measurement characteristics in Stand forest with six-tree sampling method with stratification compared to the sample method. Removal without grafting is less. And this amount was calculated for the number of trees per hectare as 8811.81 and 5677.52 respectively that with the stratification of the forest and the implementation of Prodan's six-tree sampling, the estimated average of the examined characteristics is 35.56% closer to the real average And the error rate is less than the statistical standard. The percentage of error reduction in sampling after seeding was calculated as 4.42% for number per hectare and 11.91% for breast cross-sectional area and 18.48% for volume per hectare.
Conclusion: From the results of this study, it can be concluded that it is possible to estimate the characteristics of the number, basal area and volume per hectare of forest based on the classification and implementation of six-tree sampling methods (Prodan), with a relatively variable area. It is more accurate for planning heterogeneous forests in the north of the country.
Introduction and Objectives:Renewable natural resources such as forests have played an important role in human life since the past. The principled and sustainable use of forests requires technical planning. Fundamental and technical planning requires data collection and analysis and obtaining useful quantitative and qualitative information. One of the methods of data collection in forest populations is 100% statistics. The implementation of 100% statistics in large forest areas is rarely implemented due to technical and economic reasons, and in most cases it is used to compare different sampling methods. In the preparation of plans and researches of northern forests, sampling methods with a fixed area are mostly used. Today, different forest sampling methods have been designed and presented, each of which has its own advantages and merits. The use of these methods requires checking and determining the most suitable ones in terms of ease of implementation, time and accuracy. On the other hand, today the industrial forests in the north of the country have become heterogeneous stands due to exploitation in the past. For this type of forests, using the stratification method combined with sampling methods will be useful and effective. In order to plan to increase efficiency, speed of operation and reduce costs, it is necessary to examine and use different sampling methods with fixed and variable areas, including multi-tree sampling. This study is aimed at the effect of forest classification and its combined effect with fixed area sampling method and PRODAN six tree variable area sampling method and comparing the accuracy of estimators.
Materials and Methods:This study was selected in the Safaroud forests of Mazandaran with an area of 176 hectares. The selected areas were measured and recorded using the statistical method of 100% of all the trees in the area (counting limit, diameter equal to chest more than seven and a half centimeters). In order to avoid mistakes and make it easier to perform 100% statistics, the studied area was divided into square pieces with dimensions of 50x50 meters and 704 plotes were placed in the field. Then the trees in each of these parts were measured separately. Prodan's six-tree method was carried out in two stages. The first stage was measured in an unclassified area of 176 hectares with a grid size of 100x100 meters. The second stage of the forest area under investigation using the method of "Neyman" stratification into three stratum in terms of volume inventory including less than 200 cubic meters, between 200-250 cubic meters and more than 250 cubic meters per hectare and based on Prodan's six-tree method was performed using new grid dimensions for each stratum. In this study, the effect of segmentation on accuracy and time was investigated using the criterion (E%2×T). For this purpose, the time required to unload the sample plotes for the necessary measurements inside the sample plot and the time required to travel the distance between the adjacent sample plotes were also calculated and recorded using a stopwatch. The effect of segmentation on accuracy and time was investigated using the criterion (E%2×T).
Results:The results of the comparison of the statistical test between the average of the variables calculated with the statistical methods of 100% (true mean) and six-tree sampling (Prodan) in the first stage without stratification and in the second stage with the implementation of the "Neyman" stratification method It showed that there is a significant difference at the level of 0.05%. The results of this study in terms of accuracy and cost index (E%2×T) show that the error and statistical error of the measurement characteristics in Stand forest with six-tree sampling method with stratification compared to the sample method. Removal without grafting is less. And this amount was calculated for the number of trees per hectare as 8811.81 and 5677.52 respectively that with the stratification of the forest and the implementation of Prodan's six-tree sampling, the estimated average of the examined characteristics is 35.56% closer to the real average And the error rate is less than the statistical standard. The percentage of error reduction in sampling after seeding was calculated as 4.42% for number per hectare and 11.91% for breast cross-sectional area and 18.48% for volume per hectare.
Conclusion: From the results of this study, it can be concluded that it is possible to estimate the characteristics of the number, basal area and volume per hectare of forest based on the classification and implementation of six-tree sampling methods (Prodan), with a relatively variable area. It is more accurate for planning heterogeneous forests in the north of the country.
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