مجله پژوهش و توسعه جنگل
سال هفتم شماره 2 (تابستان 1400)

It is necessary to find solutions for soil recovery of skid trail. Water-bar construction is one of the ‎best management practices to improve the compaction and prevent the erosion of skid trail soil. ‎Recovery of soil physical properties 11 years after water-bar construction on skid trail was ‎investigated on 40 square meter sample plots in two slope (0-10% and 10-20%) and three traffic ‎classes (Low, Medium, High) in the forests of Nav district in the west of Guilan province. The ‎studied variables included soil bulk density, total porosity, penetration resistance and rutting depth. ‎Soil bulk density, penetration, and rutting depth were measured by steel cylinder, pocket ‎penetrometer, and a 5-m leveling rod. The parameters in each treatment were studied in three ‎replications. The effect of slope and traffic variation on soil physical properties was performed on 72 ‎sample plots. The results showed that the effect of slope, traffic and their interaction were ‎significant on soil bulk density, total porosity, penetration resistance, and depth of rutting. The ‎value of soil bulk density, total porosity, and penetration resistance in LSLT (Low Slope-Low ‎Traffic) class was recovered, and there was no significant difference between this class and the ‎control area. The results of the study showed a positive effect of water-bar construction on the ‎recovery of soil properties in skid trail with low slope and low traffic.

This research was conducted to study the effect of implementation forest protected plan on quantitative and qualitative characteristics, extension of Loranthus europaeus and regeneration in Salas-babajani’s Forest stands. For this purpose, in the protected and unprotected region, 40 hectares area with similar physiography and floristic condition in a range of 1250 to 1550 meters above sea level, were selected. 40 circular sample plots with 1200 m2 area in a 100*100-meter inventory grid was established in each of them. In each sample plot, the general specification of the location of the sample plot such as slope, altitude, aspect, species type, quantitative characteristics of tree (diameter at breast height, small and large diameter of the crown) measured. Independent t-test and chi-square test were used to compare quantitative and qualitative data, respectively. According to the results of this study, Quercus brantii and Crataegus sp. had the highest and lowest percentage of mixing in the forest stands of the study area, respectively. The mean of crown diameter, the percentage of healthy trees, average sprout number and the average number of Loranthus europaeus in the polluted trees in protected area were higher than unprotected area. The results of this research indicated that the forest conservation-based management has positive effect on quantitative and qualitative characteristics in protected forests and emphasized the necessity of conservation, regeneration and development of these forests.

Forestry projects often result in inconsistent environmental impacts and consequences, including wood exploitation and livestock grazing. The aim of study is to evaluate the effect of wood harvesting and livestock on the degradation of Kheyrud Forest in Nowshahr city using the optimized forest degradation model in four scenarios of current situation, without wood harvesting, without livestock, and without wood harvesting and livestock. Homogeneous environmental units were prepared using ecological resources. A set of human activities and the intensity of the impacts in homogeneous environmental units were obtained. After predicting the coefficients of model in the scenarios, the statistical comparisons of the outputs and the significance of changes were evaluated. Due to the abnormality of the data, Kruskal-Wallis test was performed for statistical comparison of coefficients of degradation in four scenarios. Considering the results, there is a significant difference between the coefficients of degradation in different scenarios. The average coefficients of degradation in the current situation, without wood harvesting, without livestock, and without wood harvesting and livestock scenarios are 1.49, 0.72, 0.9 and 0.3 respectively. According to the results, livestock and wood exploitation are the most important factor influencing forest degradation. The model, which has been used in this research, has a high capability in predicting and comparing different scenarios and management policies as a decision support system in the forest; and using this model we can evaluate forest plan impacts before and after the implementation of project.

The purpose of this study was to investigate the effect of grazing intensity and type of livestock and environmental factors on vegetation composition and diversity in five areas with different livestock types (cattle, Markhoz goat, Mo goat, and sheep) and different grazing intensities (five treatments) at the forests of Armardeh. In total, 34 sample plots (100 m^2) for vegetation cover sampling were taken. Differences between regions in terms of species diversity were analyzed using analysis of variance and the effect of livestock grazing on vegetation composition using Redundancy Analysis (RDA). Result indicates that, control and the region with four livestock types have highest and lowest diversity respectievely. Canopy cover (percent), elevation, Quercues branti- Q. infectoria type, and stocking rate where the most important environmental factors are driving vegetation composition. Livestock type and grazing intensity with some environmental variables shape affect significantly the vegetation composition, in a way that with increasing grazing intensity and livestock type, annual and invasive plants appear in highest presence and with decreasing of those, forbs, shrubs, and geophyte plants are widely spread in the vegetation composition.

In recent years, with an alarming degradation rate of Caspian forests, afforestation can be considered as a suitable solution to restore the degraded areas. Different species especially Oak (Quercus castaneifolia C. A. M) and Alder (Alnus subcordata C. A. M) were planted in vast areas. Elements quantitative relations (stoichiometry) has an important roll in organic matter decomposition by changing these elements availablity in soil and is a main index to better undrestanding of microbial and OM conditions in soil as well. The aim of this study was to determine the effect of tree species in deferent ages on quantitative relations in these afforestations. This research was carried out in 15-, 20-, and 25-years old stands of Mazandaran wood and paper company afforestations and 30 soil and litter samples were collected from 10 cm depth of soils in each stand using systematic random method. Based on the results, the highest amount of quantitative relations of soil C/N (18.33), C/N microbial biomass (15.88), carbon to particle organic nitrogen ratio (10.36) and carbon to dissolved organic nitrogen ratio (3.00) were seen in older oak afforestations which had significant differences with alder afforestations. Also, oak stands in higher ages amend quantitative relations of soil carbon and nitrogen in future years of the afforestations, these findings provide a scientific theory for use in the evaluation of soil nutrients in afforested areas.

This study aimed to evaluate of unsurfaced forest road distresses on the existing curves. Numbers of 30 selective plots on the center of curves were measured. A paired sample plot beside of each curve was measured. In each plot, seven indices of unsurfaced road distress including improper cross section, inadequate roadside drainage, corrugation, dust, potholes, ruts and loose aggregate of soil were measured. Paired samples t-test and Wilcoxon test were used to analysis of data. Result showed that there were improper cross section and dust distresses factors in all plots on the curves, while 3.3 % of paired plots had none of these distresses. Also, distress intensity causing by improper cross section and inadequate roadside drainage factors were more in the curves than to paired plots and significant difference between the curves and paired plots was observed. The results of corrugation indicated that 70 and 66.7 % of sampled plots in the curves points and side plots lacked this type of distress, respectively. Results showed that the depth and area of potholes and ruts, and loose of soil aggregate in the curves points were greater than the paired plots but there was no significant difference between the curves and paired plots. Results of this study shows importance of regular maintenance activities and application of evaluation indices at the network level of pavement.

To investigate the relationship between some physical and chemical properties of soil and tree ecophysiological properties on dieback of Oak trees, 30 square sample plots with 2500 m2 area, in a random systematic grid (200×200) were selected. The percentage of dieback were measured in each sample plot and soil and leaves of trees were sampled. Some soil properties such as texture, electrical conductivity, acidity, bulk density, porosity, Carbon and organic matter and concentrations of Ca, Mg, N, P, K, Na were measured. Also, Peroxidase, Catalase and Ascorbate peroxidase enzymes, MDA, Proline, Chlorophyll a, b, total Chlorophyll, Carotenoid pigment and concentrations of Ca, Na, K, Mg, P and N in leaves were measured. Comparison of variable means showed that there is just significant difference in leaf nitrogen between different dieback classes. In general, the results of this study showed that the soil properties in our study area were not significantly affect on oak decline. On the other hand, the physiological capabilities of trees solely, cannot be the cause of their different dieback.

There had been no study about the effect of the plantations’ age on the properties of forest soils and soil carbon sequestration. Therefore, the aim of this study was to investigate the effect of an alder plantation’s age on some soil properties and carbon sequestration. Three alder plantation stands (25, 30, and 35 years old) located in Parcels No. 6 and 7 in Shastkolateh forest were selected. In order to investigate the quantitative characteristics of trees, the diameter and height of all trees were recorded using the full inventory method. In each stand, 20 × 20 m sample plots were considered using a systematic random method with a 50 × 50 m grid. A soil sample was then taken at the depth of 0-15 cm in each plot using the core method. The result showed that the 35-year-old stand had the highest soil moisture (45.49%±2.44) and the lowest bulk density (1.36 g/cm2±0.02). The highest pH (7.59 ±0.01) and the lowest EC (0.71±0.02 dS/m) were observed in the 35-year-old stand. The highest and lowest percentages of total soil nitrogen as well as carbon sequestration were observed in the 35- and 25- year- old stands, respectively. The results of component analysis showed that the 35-year-old stand was different from the other two stands; hence, it can be stated that alder plantation stands will have a high capacity for carbon sequestration at this age.

Despite the efforts made in the formation of non-governmental organizations and their role in the protection and sustainability of natural resources, non-governmental organizations have not yet been able to gain a proper position. The aim of this study was to identify the strengths, weaknesses, opportunities and threats facing NGOs in environmental and sustainable forest management. The study population included experts and members of 12 natural resources and environment non-governmental organizations in Golestan province, 120 of whom were selected as the sample. The data collection tool was a researcher-made questionnaire in which the questions were designed based on the opinions of experts and members of non-governmental organizations obtained during 60 interviews. SWOT method was used to analyze the data. The results showed that the weight of strengths is more than the weight of weaknesses and the weight of threats is more than the weight of opportunities faced by NGOs. Based on the results of analyzing internal and external factors, the best strategy for NGOs is an offensive strategy that emphasizes the use of existing strengths and opportunities to expand the activities of NGOs.

Soil in forest ecosystems is a giant source for storage of atmospheric carbon that would increase its contribution against climate warming under proper management. In the current research, soil and litter contribution in carbon sequestration were compared between a 50 years old enclosure (less degraded) and un- enclosure (degraded) wild pear stands. Besides, some soil characteristics including soil moisture, bulk density, organic carbon, total nitrogen, phosphorus, and soil microbial respiration were studied. In each stand, 5 soil samples and 10 litter samples were collected from each plot and the characteristics were compared with T-student independent analysis. The results clearly indicated that soil carbon storage and carbon storage in coarse litter due to greater tree covers in enclosure field were two times higher than un- enclos6ure. Meanwhile, carbon storage in fine litter was same in the both stands. Phousphurus content and total nitrogen in soil of enclosure field were 6 and 2 times higher than un- inclosure, respectively. Moisture content Not only was higher in less degraded field (36%) in comparison with degraded one (21%) but also soil microbial respiration in less degraded field was higher around 31% when compared with degraded field. Finally, it can be proposed that enclosure management not only can improve soil carbon storage more than two times but also can increase soil fertility. This finding highlights the importance of enclosure management in Zagros region for maintaining of soil functions.

This study was performed in six plantations including Pinus eldarica and Cupressus arizonica (pure coniferous), Robinia pseudoacacia and Fraxinus sp. (pure broadleaved) along with R. pseudoacacia-Fraxinus and R. pseudoacacia-C. arizonica (mixed) in Lavizan Forest Park. Soil carbon stock was measured and the relationship between some physico-chemical properties of soil with organic carbon was examined. Soil acidity, texture, bulk density, particle density and percentage organic carbon were measured in 60 soil samples collected from 0-10 cm and 10-30 cm depths under the plantations. According to the results, the maximum and minimum soil carbon stocks in both depths were seen in Pinus eldarica and Fraxinus types, respectively. In all plantations under consideration, carbon storage was greater at lower, i.e. 10-30 cm, soil depth. In both studied soil depths, the highest carbon storage in pure coniferous and hardwood types was respectively observed in P. eldarica and R. pseudoacacia plantations and among mixed types in R. pseudoacacia-C. arizonica type. Also, stepwise regression showed that of physic-chemical soil properties, pH, bulk density and clay and of  quantitative characteristics of trees, DBH, hight and crown diameter were the most important factors affecting soil organic carbon in the study area.