فهرست مطالب aliasghar vahedi

In the Hyrcanian forests, fine woody debris (FWDs) plays a significant role in providing ecological services. However, their importance is often overlooked in the management and executive sectors. Based on the sustainability indices of natural forests—considering changes in carbon stock and the value of wood products—these seemingly insignificant FWDs are 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 aims 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.

The study was conducted in Khairood-kenar forest using a cluster design at different altitude gradients ranging from 100-1800 m above sea level. To create the cluster design, three circular samples with a radius of 7.32 m were placed in the form of a triangle with azimuth angles of 0, 120, and 240 degrees. The distance between each sample was 36.6 m, 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 was intersected by the transact line, was measured and recorded using calipers. After examining outliers upon the initial analysis, the volumetric observation variograms were fit using various models based on the distance and spatial correlation of variance. Based on the spatial structure, an optimal model, with the highest coefficient of determination (R2) and the lowest residual sum of squares (RSS), was selected for implementing the ordinary Kriging interpolation method. Based on the fitting of the models in different diameter classes, Kriging, and inverse distance weighting (IDW) methods were used for the 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 FWD volume. The accuracy of both the estimation and the performed zoning was evaluated based on the fit between the estimated variable values and the observation values using R2and root mean square error (RMSE) indices.

The total volume of FWDs within the researched forest amounted to 24.3 m3/ha. The volume stocks of the first, second, and third diameter classes of the FWDs were 2.14, 6.01, and 16.23 m3/ha in the study forest. The variogram modeling revealed that the spatial variations in the volume of FWDs across different diameter classes exhibited an average spatial structure. However, the fit was not optimal when considering the R2 and RSS values. Interestingly, the kriging results were most accurate for the FWD first diameter class compared to the other diameter classes. Despite this accuracy, the overall estimated precision remained poor, with an RMSE 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 was isotropic and the other diameter classes were anisotropic. Since the kriging method was not effective for estimating the spatial distribution of the FWDs in the 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 revealed no significant accuracy in the estimation. Therefore, it can be concluded from the results that the introduction of the volume of FWDs in the forest floor under the altitude gradient is not recommended for the study area.

Based on the results, the volume stock of FWDs for different diameter classes along the altitudinal gradients was independent of autocorrelation and spatial correlation. This means that the FWD volume stock variations in different altitudinal gradients of the study forest are influenced by silviculture, biological, and ecological items with no obvious commonality in this regard. Since the accumulation of the FWD volume in the studied forest is not considered auto-correlated variation, it 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 gradients.

Plant Species Richness (PSR) plays an important role in forest ecosystem functions and services. Despite the fact that Fine Woody Debris (FWD) occupy a large volume of the temperate forest ecosystem in the north of Iran, they have received less attention than Coarse Woody Debries (CWD). FWD is a component of natural forests, in addition to increasing the productivity of forest trees, helping to trees regeneration, maintaining and increasing soil moisture and nutrients, and long-term carbon storage, contribute the enhanced function of newly developing microhabitats with an important function in plant understory richness. Therefore, not paying attention to FWD leads to wrong estimation of the total volume of woody debries and its key role on the performance of forest ecosystems. Therefore, it was considered for current study that Boosted Regression Tree (BRT) machine learning technique used to model the PSR in unmanaged forest stands. For this aim, Oak - hornbeam stand in Loveh forest in the east of Golestan province, Iran was selected for sampling.

For this purpose, 30 sample plots 400 m2 (20 m × 20 m) were set in the study area, and the type and percentage of plant cover was recorded based on the Braun-Blanquet index. In the following, the number of plant species recorded in each sample plot was the basis for calculating species richness. In order to measure the volume of FWD, the alignment of the sides of the sample plot of 400 square meters was used as the basis of calculation. Therefore, in line with the sides of each sample plot and in the form of a linear transect with a total length of 80 meters (equal to the perimeter of each sample plot), FWD intersected with the transect were identified. The names of tree species of each of the FWD is specified, and according to the cross diameter with the transect, the FWD were placed in one of three diameter classes: 1 to 2.5 cm, 2.5 to 4.5 cm, and 4.5 to 7.5 cm. To measure the percentage of soil moisture and organic matter, the soil was taken from the center of each sample to a depth of 15 cm. Soil moisture percentage was obtained by using the difference between wet and dry weight of soil and also the amount of soil organic matter by Walkley-Black method in the laboratory. The gmb package in R programming language was used to fit the boosted regression tree model. This model is one of the methods that helps to improve the performance of a single model by using the combination of multiple models. Therefore, in this method, the combination of two algorithms "regression tree and classification" and "boosting" is used. It should be noted that in this research, in order to reach the optimal number of trees, the number of 1000 was used as the starting point. In this study, the amount of species richness in each plot as the response variable, and the variables of slope percentage, slope aspect, altitude, soil moisture percentage, soil organic matter percentage, average of total volume of fwd, average volume of fwd in decay class 1, average volume of fwd in decay class 2 and the type of fwd were considered as predictor variables.

Based on the results, the initial model fitted in the number of trees 7700 showed the highest accuracy. However, due to the lack of influence of some variables in the model, the variables of slope, slope aspect, altitude, the type of fwd and the average volume of fwd in decay class 1, these variables were excluded from the model based on the deviation changes. And the model was refitted in the optimal number of trees of 7800. Based on the final model of the BRT, the highest amount of species richness was recorded with the increase of soil organic matter to > 2.15% and in a soil moisture percentage >30%. Furthermore, a high amount of FWD from the first diameter class and with the decay class 2 (rotten) led to an increase in plant richness in the studied area. In the present study, the adjusted R squared > 0.99 with the Root Mean Square Error (RMSE) < 0.039 shows the high accuracy of the BRT model.

Although fwd comprise a large part of woody debries in the forests of the north of Iran, no specific place has been considered for it in any of the statistical protocols. This matter has led to the fact that there is no specific estimate of the volume of fwd and its role on the forest ecosystem is neglected. Therefore, this study was conducted with the aim of modeling the effect of this important component on the richness of plant species in a broadleaf stand in Loveh forests of Golestan province. The findings of the research showed that by creating favorable habitat conditions, the fwd increase the abundance of plant species and maintaining this component is important in increasing the organic matter of the forest soil. The high rate of decomposition in fwd compared to cwd causes that while maintaining and increasing the soil moisture, the organic materials in the wood are available to the soil layer in a short period of time. In recent years, some experts in the field of natural resources have emphasized the collection of fwd and their use in cellulose industries. A large part of these opinions has also found a scientific basis in the shadow of the minimization of the volume and role of the fwd and the lack of sufficient information about this very important component. If the findings of this research clearly show that the collection and removal of fwd will have a negative impact on soil moisture and organic matter and thus on the richness of plant species. Conducting similar and additional studies by including soil nutritional variables as well as other plant indicators can significantly help in confirming or rejecting this result

Due to ecological and biological importance of fine woody debris (FWDs) in forest ecosystems, it is essential to be clarified influencing factors on the FWDs volume stock through appropriate model. One of the models can be decisively efficient for optimal management and control of the FWDs volume stock is the ordinal logistic model. It is expected that the FWDs have a significant contribution in the Hyrcanian forests where different types of plant communities and trees are widely distributed across altitude gradients. Thus, the aim of this research is to use rank logistic analysis to examine the impact of various factors on the volume accumulation of the FWDs in relation to the altitude gradient of the Khairudkanar research forest.

The current study was conducted in the Kheiroud forest using the cluster sample plots implemented along the altitude (100- 1800 m). A total of 12 samples were arranged in an altitude gradient from sea level. These samples consisted of three circular plots, each with a radius of 7.32 meters. The circular plots were positioned in the form of a triangle, with azimuth angles of 0, 120, and 240 degrees. Additionally, another sample with the same area was placed at the center of this design. The distance between each of the circular plots in the cluster was 36.6 meters. In this study, the placement of sample plots was conducted randomly within the specified altitude range, with an interval of 150 meters. A total of 36 clusters were established, comprising 144 samples, within the research forest. These samples were categorized into three diameter classes for the FWDs: 1-2.5 cm, 2.5-4.5 cm, and 4.5-7.5 cm. To measure the diameter of these small dry trees, a linear transect was executed from the center of each circular sample plot. The transect had a fixed azimuth of 150 degrees. Specifically: The diameter layer within the range of 1-2.5 cm was measured at a distance of 4.27-1.6 meters, and For other diameter layers, the measurements were taken at distances ranging from 7.32 to 7 meters. Ultimately, a total of 4.27 meters were harvested during this investigation. During the evaluation process, a transect line was used to measure the FWDs diameter whose central axis was obstructed by the line. Additionally, the type of species, the decay or lack of decay of the FWDs were also recorded. However, the length of these FWDs was not measured in the field due to the evaluation method used. In the analysis, we employed Spearman’s test and calculated Spearman’s correlation coefficient. Additionally, we utilized Chi-square statistics and the dimensions of the consensus table to evaluate the significance of correlation intensity between variables. To model this relationship, we included all uncorrelated variables as input variables, irrespective of any co-linear relationships among the factor variables. Nominal and rank variables were introduced as factors with fixed effects, while quantitative variables served as side variables during the implementation of rank logistic analysis. To validate each model, we assessed various variables using the model fit index. Additionally, we considered the pseudo-explanation coefficients. The significance of the model and its calculation coefficients was examined using the Wald statistic. Furthermore, we evaluated the model’s accuracy in relation to estimated values and observations using Pearson and standard deviation tests.

The research findings indicated that the average volume of the FWDs per hectare in the studied forest was 2.14, 6.01, and 16.23 cubic meters for the first, second, and third diameter classes, respectively. The results of logistic analyses based on the log-likelihood test (X2= 0.06; P > 0.05) and pseudo-R2 (Pesudo-R2 = 0.001) showed that the altitude gradient has no significant effect on the volume accumulations of the FWDs in different diameter classes. According to the Cramer's V and Spearman correlation tests, the results demonstrated that altitude gradient significantly correlated with the stand types, aspect, species and decay of the FWDs in the study forest. Moreover, the results obtained using Kramer's correlation coefficient to eliminate the effects of collinearity between input variables indicated that there is no significant relationship between the aspects and the species, and decay classes. Also, there were no significant correlations between the stand type and decay, and the FWDs species. Taking into account the non-collinearity and variance inflation factor (VIF), the final results of modeling showed that the FWDs species and decay have only significant effects on variations of the first diameter class of FWDs volume stock (Pesudo-R2= 0.24; P < 0.05; X2= 22.61).

On the basis of the Wald test, effects of the FWDs species were similarly significant, and the FWDs decay was inversely significant in association with the FWDs first diameter class response (P < 0.01). It appears that the amount of volume accumulation of the FWDs in thicker diameters was not affected by the factors that were introduced. This implies that many unforeseen events, such as natural disturbances of varying scales and intensity, as well as the inherent nature of forestry - including developmental stages - may be the foremost factors that significantly impact the volume inventory of the FWDs in the thicker diameters.

One of the concerns for the executive organizations to introduce an alternative plan of rest of the Hyrcanian forests is to make decision regarding the exit of coarse woody debris (CWD) volume from the Hyrcanian forests. The research was carried out in the permanent plot with 400 m2 based on the protocols of the comprehensive research plan enacted by Agricultural research Education and Extension organization in Iran. Within each plot beneath the CWDs over than height of 1.5 m and dimensions of 7.5 cm, the organic accumulations resulted from the decay trend were sampled. Besides, the soils mineral layer up to 10 cm depth were sampled after removing the organic accumulations, and were transported to the laboratory. The results of PCA (Principal Component Analysis) showed that beneath the CWDs including higher organic accumulations, amount of the organic carbon and the nutrients were lower in the substrate soil mineral layer. Furthermore, the results of Spearman test indicated that amounts of organic carbon and nutrients in the organic and substrate mineral layers were independent of each other (P > 0.05), and amounts of the organic carbon with Nitrogen were significantly correlated (P < 0.01). Also, the results of two-way PERMANOVA test indicated that interactions of form, species and decay of the CWDs in the study sites were not significantly effective on the organic carbon under the CWDs.

The aim of this study was to investigate the changes in the amount of dead wood carbon storage of Quercus brantii Lindl in relation to physiographic factors in Qalajeh forest of Kermanshah province. For this purpose, an area of ​​Qalajeh forest with an altitude range of 1400-2100 meters above sea level was selected, and the area was divided into seven elevation classes with a difference of 100 meters. Then, at the level of each elevation class, one-hectare sample plots with three replications were implemented to estimate the amount of standing and fallen dead wood carbon storage. In each sample plot, while specifying the slope and direction, in addition to quantitative measurements in line with the research goal in relation to standing dead wood, the sample line in parallel and at a suitable distance from each other to check and measure the fallen dead wood whose diameter was greater than or equal to 2 cm for Necessary measurements were implemented. The results of Pearson correlation test showed that there is a significant negative correlation between the amount of standing and fallen dead wood carbon storage with the altitude factor. Also, the results of analysis of variance showed that the changes in dead wood carbon storage of Quercus brantii Lindl in different physiographic units did not have a significant difference, which shows that the changes in dead wood carbon storage of Quercus brantii Lindl trees in the study area are independent of the Physiographic factors effects.

The aim of this study was to investigate the trend of changes in basic density and green moisture content of hornbeam trees in the vertical and radial direction of trunk wood. Therefore, a complete disk was prepared from 10 fallen trees in 20-40, 40-60 and 60-80 diameter classes and different decay degrees (grades 1, 2 and 3). The disks were prepared at intervals of 5, 35 and 65% of the vertical sections of the trunk. Then, the sample pieces with a fixed volume of 2× 2× 2 cm3 were fragmented at a ratio of 10, 50 and 90% of the radial sections of the disks and were obtained their basic density and green moisture content. The results showed that the green moisture content and trunk basic density of hornbeam trees in different diameter classes with the degree of decay had a significant difference with a probability of 99% (P <0.001). The highest mean basic density values were observed in the distance of 5% in the vertical direction and 90% in the radial direction of the trunk wood with 0.59 and 0.60 g / cm3, respectively. The highest mean values of green moisture content were observed in 90% in the radial direction of 0.65 and the distance of 5% in the vertical direction of 0.66. Of course, green moisture content in vertical sections showed a significant difference with changing the degree of decay (P> 0.05), but no significant difference was observed in radial sections. The results of correlation showed that basic density has the highest significance correlation with diameter equal to the breast and the lowest significance correlation with the coefficient of moisture.

This study aimed to analyze spatial patterns and associations of the studied trees in the developmental stages for achieving required information to prevent undermining stability of Nour Forest Park, to implement close-to-nature silvicultural prescription and to simulate distributions of aforementioned species in non-protective situations. Product of volume and specific wood density were used for estimating biomass of Caspian poplar trees in the forest. Mathematical parameters were used instead of absolute variables of wood density for estimating bole mass and crown mass of each tree. After distinguishing the developmental stage in the studied forest, three plots with one hectare area of 100 × 100 m dimension were outlined and the trees were coordinated by using measurement or trigonometric relations. Spatial analysis resulted from univariate O-ring application showed that the distribution was aggregated in the initial and optimal stages in the specified distances. In the decay stage, as well as being aggregated and random distribution, regular pattern of Caspian poplar trees was observed in the distance of 36 and 40 meter. Furthermore, the results of bivariate O-ring indicated that there was an intra-species positive attraction between medium class of biomass (medium size) and small class of biomass (small size) in a similar distance (8 m) in both initial and decay stages. As such, the intra-species attraction in the optimal stage was in attraction format in definite distances, and associations in the other distances were independent. The results showed that the association of aboveground biomass between large size and small size of trees in the developmental stages, implying that the density of small size trees is not under effects of intra-species competition resulting from the large sizes of trees in the developmental stages.

Today¡ poplar plantation is considered an important forestry practice for preservation of carbon pools and a major source for bioenergy and cellulose. Providing different allometric equations¡ this research presents a model that may improve the biomass estimation of P. deltoides in Talookola Nursery in Sari. A number of 25 cuttings with 25 cm length were planted in 2011 within 1*1 m plots with identical site condition in three-replication experiment. Saplings numbered 4¡ 12 and 18 were randomly selected in three diameter classes (0-1¡ 1.1-2¡ 2.1-3 cm)¡ respectively. The weight/wet weight ratios were measured after roots and stems were oven-dried at 85 ºC for 48 hours. Collar diameter and sapling height were chosen as variables for modeling allometric equations. The results showed that the logarithmic model related to above-ground biomass including collar diameter (D) and logarithmic models including product of diameter square and height (DBH2 × H) associated with below- and total ground biomass had the highest accuracy with the best goodness of fit data. Moreover¡ multivariate empirical models which did not have multicollinearity (VIF