نوع مقاله : مقاله کامل علمی پژوهشی
نویسندگان
1 دانش آموخته کارشناسی ارشد مدیریت جنگل، دانشکده علوم جنگل، دانشگاه علوم کشاورزی و منابع طبیعی گرگان، گرگان، ایران.
2 دانشیار گروه جنگلداری، دانشکده علوم جنگل، دانشگاه علوم کشاورزی و منابع طبیعی گرگان، گرگان، ایران
3 دانشیار، گروه آمار، دانشکده علوم، دانشگاه گلستان، گرگان، ایران.
4 دانشجوی دکتری مدیریت جنگل، دانشکده علوم جنگل، دانشگاه علوم کشاورزی و منابع طبیعی گرگان، گرگان، ایران.
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Abstract:
Background and Objectives:
An accurate estimate of trees height is essential for evaluation of the forest stands volume and above-ground biomass. Also, nonlinear mixed-effects models using random effects with accounting variation between plots, in addition to maintaining the diameter-height relationship, improve the accuracy of the models, and these mixed effects models account for intergroup variation and intragroup variation. Therefore, this study aimed to develop a Height-Diameter relationship Oak (Quercus Castanefolia C.A.M) using nonlinear models and nonlinear mixed-effect models in uneven-aged broad-leaved stands in Golestan province (Shast-kalateh, Jafar-abad and Loveh forestry plan).
Materials and Methods: We applied a systematic sampling method to collect field data within a 150×200 m network (71 circular plots), and in each plot, tree species, height and diameter at breast height (DBH) of all trees were measured. In the first stage, we used 20 non-linear diameter-height models to select candidate models, then refitted in the second stage using mixed-effect model using dominant height, mean quadratic DBH, Basal area, BAL, stand volume and tree density.
Results: The results of fitting non-linear models for Oak showed that RMSE and R2 are ranged 3-4 meters and 0.4-0.62, respectively. By adding dominant height, mean quadratic DBH, Basal area, BAL, stand volume, and tree density as random effects in the nonlinear mixed-effect method, R2 improved by about 10 to 16%, and the RMSE improved about 0.2- 1 m. By adding
Conclusion: The results showed that using the nonlinear mixed-effect method in comparison with nonlinear regression models improved the accuracy of estimating the height, especially in uneven-aged broadleaved stands. These models can show variability height in stands. Therefore, this approach can be a suitable alternative to estimate tree height, despite few studies conducted in this field. Also, additional research on the use of nonlinear mixed-effect models for all important species of the Hyrcanian forests and other vegetation regions of Iran is necessary. Also, accurate information can be used in forest sustainable management and conservation programs. These models can be used in forest planning.
The results showed that using the nonlinear mixed-effect method in comparison with nonlinear regression models improved the accuracy of estimating the height, especially in uneven-aged broadleaved stands. These models can show variability height in stands. Therefore, this approach can be a suitable alternative to estimate tree height, despite few studies conducted in this field. Also, additional research on the use of nonlinear mixed-effect models for all important species of the Hyrcanian forests and other vegetation regions of Iran is necessary. Also, accurate information can be used in forest sustainable management and conservation programs. These models can be used in forest planning.
کلیدواژه‌ها [English]
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