Ali Asghar Vahedi 
, Asghar Fallah , Reza Akhavan , Nastaran Nazariani , Ezatoleh Khatibnia , Seyedeh Kosar Hamidi
, Asghar Fallah , Reza Akhavan , Nastaran Nazariani , Ezatoleh Khatibnia , Seyedeh Kosar Hamidi
NNatural Resources Research Department, Mazandaran Agriculture and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Sari, Iran
Abstract: (357 Views)
Extended Abstract
Introduction and Objective: In the Hyrcanian forests, the fine woody debris (FWDs) play a significant role in providing ecological services. However, their importance is often overlooked in management and executive sectors. Also, based on the sustainability indices of natural forests—considering changes in carbon stock and the value of wood products—these seemingly insignificant FWDs predicted to serve as valuable carbon reserves. Both science and economics recognize their significance. To make informed decisions about forestry operations, especially in post-respiration conditions (the rest law of the Hyrcanian forests), it is essential to accurately assess the accumulation and volume changes of these sinks across different parts of the forest. Optimum management techniques, particularly in forestry, can enhance ecological services. Therefore, our upcoming research aimed to analyze spatial statistics related to volume stock changes in FWDs within various sections of the Hyrcanian forests, with a focus on implementing optimal management strategies.
Materials and Methods: The study was conducted in Khairood-kenar forest using a cluster design at different altitude gradients ranging from 100-1800 meters above sea level. To create the cluster design, three circular samples with a radius of 7.32 meters were placed in the form of a triangle with an azimuth angle of 0, 120, and 240 degrees. The distance between each sample was 36.6 meters, and an additional sample of the same area was placed in the center of the design. Each cluster was randomly laid with three replications, resulting in a total of 12 samples across the altitude gradient from sea level. On each transact, the diameter of all dry wells whose central axis is intersected by the transact line was measured and recorded using calipers. Upon initial analysis, after checking for outliers, the volumetric observation variograms were fit using various models based on distance and spatial correlation of variance. Based on the spatial structure, the optimal model, with the highest coefficient of determination (R2) and the lowest residual sum of squares (RSS), was selected for implementing ordinary kriging interpolation method. Based on the model fitting of the models in different diameter classes, kriging and inverse distance weighting (IDW) methods were used for interpolation and estimation of response variables that were not measured at different distances. Subsequently, the cross-validation method was used to validate the existing estimates of the FWDs volume. The accuracy of the estimation and the accuracy of the performed zoning were evaluated based on the fit between the estimated variable values and the observation values, using coefficient of determination and root mean square error (RMSE) indices.
Results: We discovered that the total volume of FWDs within the researched forest amounts to 24.3 cubic meters per hectare. The volume stock of the first, second, and third diameter class of the FWDs in the study forest is 2.14, 6.01, and 16.23 cubic meter in per hectare in the study forest. The variogram modeling revealed that the spatial variations in the volume of FWDs across different diameter classes exhibit an average spatial structure. However, when considering the R2 and RSS values, the fit was not optimal. Interestingly, the kriging results were most accurate for the FWD first diameter class compared to other diameter classes. Despite this accuracy, the overall estimated precision remained poor, with an RMSE (Root Mean Square Error) of 6.32 and an R2 of 0.16. The result of the variography of the volume inventory of FWDs showed that their first diameter class is isotropic and the other diameter classes are anisotropic. Based on the fact that the kriging method was not effective for estimating the spatial distribution of the FWDs in second and third diameter classes, the IDW technique was used instead. The results obtained from the IDW technique for evaluating the spatial distribution of FWDs in the second and third diameter classes showed that there was no significant accuracy in the estimation. Therefore, it can be concluded from the results that the introduction of the volume of the FWDs in the forest floor under the altitude gradient is not recommended for the study area.
Conclusion: On the basis of the results, the volume stock of the FWDs for different diameter classes along the altitudinal gradients was independent from autocorrelation and spatial correlation. That means the FWDs volume stock variations in different altitudinal gradients of the study forest are influenced by the siliviculture, biological and ecological items with no obvious commonality in this regard. Since the accumulation of the FWDs volume in study forest is not considered as auto-correlated variation, this is expected that the classic tests such as parametric and non-parametric tests can be reliably applicable to examine the response variables among the stand types, and altitudinal gradient.
Introduction and Objective: In the Hyrcanian forests, the fine woody debris (FWDs) play a significant role in providing ecological services. However, their importance is often overlooked in management and executive sectors. Also, based on the sustainability indices of natural forests—considering changes in carbon stock and the value of wood products—these seemingly insignificant FWDs predicted to serve as valuable carbon reserves. Both science and economics recognize their significance. To make informed decisions about forestry operations, especially in post-respiration conditions (the rest law of the Hyrcanian forests), it is essential to accurately assess the accumulation and volume changes of these sinks across different parts of the forest. Optimum management techniques, particularly in forestry, can enhance ecological services. Therefore, our upcoming research aimed to analyze spatial statistics related to volume stock changes in FWDs within various sections of the Hyrcanian forests, with a focus on implementing optimal management strategies.
Materials and Methods: The study was conducted in Khairood-kenar forest using a cluster design at different altitude gradients ranging from 100-1800 meters above sea level. To create the cluster design, three circular samples with a radius of 7.32 meters were placed in the form of a triangle with an azimuth angle of 0, 120, and 240 degrees. The distance between each sample was 36.6 meters, and an additional sample of the same area was placed in the center of the design. Each cluster was randomly laid with three replications, resulting in a total of 12 samples across the altitude gradient from sea level. On each transact, the diameter of all dry wells whose central axis is intersected by the transact line was measured and recorded using calipers. Upon initial analysis, after checking for outliers, the volumetric observation variograms were fit using various models based on distance and spatial correlation of variance. Based on the spatial structure, the optimal model, with the highest coefficient of determination (R2) and the lowest residual sum of squares (RSS), was selected for implementing ordinary kriging interpolation method. Based on the model fitting of the models in different diameter classes, kriging and inverse distance weighting (IDW) methods were used for interpolation and estimation of response variables that were not measured at different distances. Subsequently, the cross-validation method was used to validate the existing estimates of the FWDs volume. The accuracy of the estimation and the accuracy of the performed zoning were evaluated based on the fit between the estimated variable values and the observation values, using coefficient of determination and root mean square error (RMSE) indices.
Results: We discovered that the total volume of FWDs within the researched forest amounts to 24.3 cubic meters per hectare. The volume stock of the first, second, and third diameter class of the FWDs in the study forest is 2.14, 6.01, and 16.23 cubic meter in per hectare in the study forest. The variogram modeling revealed that the spatial variations in the volume of FWDs across different diameter classes exhibit an average spatial structure. However, when considering the R2 and RSS values, the fit was not optimal. Interestingly, the kriging results were most accurate for the FWD first diameter class compared to other diameter classes. Despite this accuracy, the overall estimated precision remained poor, with an RMSE (Root Mean Square Error) of 6.32 and an R2 of 0.16. The result of the variography of the volume inventory of FWDs showed that their first diameter class is isotropic and the other diameter classes are anisotropic. Based on the fact that the kriging method was not effective for estimating the spatial distribution of the FWDs in second and third diameter classes, the IDW technique was used instead. The results obtained from the IDW technique for evaluating the spatial distribution of FWDs in the second and third diameter classes showed that there was no significant accuracy in the estimation. Therefore, it can be concluded from the results that the introduction of the volume of the FWDs in the forest floor under the altitude gradient is not recommended for the study area.
Conclusion: On the basis of the results, the volume stock of the FWDs for different diameter classes along the altitudinal gradients was independent from autocorrelation and spatial correlation. That means the FWDs volume stock variations in different altitudinal gradients of the study forest are influenced by the siliviculture, biological and ecological items with no obvious commonality in this regard. Since the accumulation of the FWDs volume in study forest is not considered as auto-correlated variation, this is expected that the classic tests such as parametric and non-parametric tests can be reliably applicable to examine the response variables among the stand types, and altitudinal gradient.
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