نوع مقاله : علمی - پژوهشی
نویسندگان
1 دانشیار پژوهش، مؤسسه تحقیقات جنگلها و مراتع کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران، ایران
2 استاد یار پژوهش، بخش تحقیقات جنگل ها ومراتع ، مرکز تحقیقات آموزش وترویج کشاورزی ومنابع طبیعی استان آذربایجان غربی، سازمان تحقیقات
3 کارشناس ارشد پژوهش، مؤسسه تحقیقات جنگلها و مراتع کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران، ایران
4 استادیار پژوهش، بخش تحقیقات جنگل ها و مراتع، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان آذربایجان غربی، سازمان تحقیقات،
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Background and objectives: In Iran, due to recent conservation policies and the need for industrial wood and import restrictions, attention has increased to development of poplar wood farming. In this view, the development of tools for the precise management of poplar plantations has become essential. Volume tables, as one of these key tools, enable economic planning and optimization of exploitation. For the development of these tables, the use of non-destructive sampling that allow estimating volume without damaging the trees is of a great importance. In the situation that West Azerbaijan province is the third province in the country in terms of poplar farming area, the lack of accurate volume models has created a serious gap in the decision-making process, exploitation forecasting, and quantitative evaluation of wood farming. Therefore, conducting this research with the aim of development of volume tables for black poplar, (Populus nigra L.) in the west Azerbaijan province of Iran using non-destructive methods is a direct response to a specific research gap and a clear necessity to improve the scientific, economic, and ecological management of wood farming in this region. This study can also provide the necessary scientific tools to optimize exploitation, reduces costs, and enhances environmental sustainability. Furthermore, its results can be used as a basis for regional and national policies in the field of wood farming, help reduction dependence to foreign resources and enhance self-sufficiency in timber production.
Materials and Methods: The west Azerbaijan province, located in the northwest of Iran, is considered as one of the prominent areas for wood farming with poplar species in Iran due to its suitable climatic and soil characteristics. In this study, firstly, the major poplar stands in the west Azerbaijan province were identified through field surveys. Then, a total of 57 trees were selected from five different poplar stands planted with P. nigra in the cities of Shahindej, Urmia, and Khoy. In order to select sample trees for developing volume tables, a stratified random sampling method was used, based on diameter classes, and diameter classes were considered from 10 to 30 cm. In each diameter class, five trees from five different stands were randomly selected and their diameter at breast height (DBH) and total height were measured. Furthermore, the diameters at different heights of the selected trees' stem (beginning and end of each two-meter sections) up to a diameter of at least five cm were recorded with a Leica D810 laser device. The actual volume of each two-meter sections of each polar tree were calculated using the Smalian's formula, and by summing them, the actual volume of the entire stem of each selected poplar tree was calculated. To evaluate the accuracy of the Leica D810 device in measuring stem diameters at various heights, a set of 13 poplar trees, which were previously scheduled for felling, were used. The diameters of these trees at different stem heights before and after felling were measured using a Leica device and Caliper, respectively, and compared using a paired Student’s t-test. To develop volume tables, data on diameter, height, and stem volume of sample trees were analyzed using nonlinear regression models. For this purpose, seven single-entry models (based on DBH alone) and nine double-entry models (based on both DBH and total height) were fitted to the data of diameter with actual stem volume as well as diameter and height with actual stem volume of trees, respectively. Then, model performance was evaluated using AIC (Akaike Information Criterion), RMSE (Root Mean Square Error), MAE (Mean Absolute Error), NSE (Nash-Sutcliffe Efficiency), and WI (Willmott Index of Agreement) to select the best model.
Results: Based on the results, the average DBH of 57 selected trees, total height, and actual volume of the stem were 19.9 cm, 17.9 m and 0.29 m3, respectively. The results of the paired t-test showed that no significant difference (P>0.05) between the Leica and caliper in diameter measurements; in other words, the two devices performed equally for measuring diameter. Results of ranking the models to select the most accurate model to develop the volume tables for P. nigra using the five criteria showed that among the one-factor models, the Hohenadl-Krenn model and among the two-factor models, the Takata model were the best models, which were used to develop single-and double-entry volume tables, respectively.
Conclusion: This study showed the used non-destructive sampling is an efficient tool for accurately collecting the necessary data for volume estimation by preserving the health of trees and preventing unnecessary cutting. This approach, while reducing costs and time for surveying, allows for continuous monitoring and optimal management of poplar plantations. Given that west Azerbaijan province has a high potential for poplar farming, access to accurate volume tables is very crucial for management and economic planning. Finally, it can be said that this study, by providing accurate volume tables and emphasizing on non-destructive sampling, has taken an important step towards sustainable management of poplar plantations in this province. It is hoped that the results of this study would be a basis for informed and strategic decisions in the field of wood farming development in this province and help achieve the goals of sustainable development of natural resources.
کلیدواژهها [English]
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