مجله جنگل ایران
سال دوازدهم شماره 2 (تابستان 1399)

Evaluating the diversity and ecological value of habitat trees is an indicator for assessing biodiversity in forest ecosystems. This research was carried out to assess the ecological diversity and ecological value of microhabitats in the beech forests in the parcel 405 of Shir-Ghala, east of Guilan province. Three plots with an area 1-ha were selected, and in each plot, all live trees and standing deadwood to explore each microhabitat, and their characteristics included the diameter at breast height, tree height as well as the number and type of microhabitat trees were recorded. To analyze the status of microhabitat diversity, alpha, beta and gamma diversity indices, Margalef richness index, Shannon-Wiener, and Simpson diversity indices, and Pielou's evenness index was calculated. In total, microhabitats were identified on 87 habitat trees (equivalent to 24.2 microhabitats per 100 trees). The most and rarest form of microhabitat was woodpecker cavities and miocrosil, respectively. Trees with the holes comprised of woodpecker cavities, trunk cavities, main branch cavities, and buttress holes account for more than half of the total microhabitat (53%), and often located on live trees (68.6%) of oriental beech (77.3%). s found in the DBH class of 10-20 cm. In conclusion, it can be explained that the conservation and maintenance of habitat trees more than one meter in diameter is recommended to provide the microhabitat and preserve biodiversity in the forests.

Charcoal production and wood burning are some of the causes of increasing carbon concentration in the atmosphere. This activity by cutting trees reduces the density and volume of forest stands per hectare and leads to changing carbon sequestration in a forest stand. Given the importance of this issue and the challenges associated with increased atmospheric carbon, the role of soil and forest biomass in carbon sequestration is important. In order to investigate the effect of charcoal production on carbon sequestration, four kilns were selected in Bastam district of Al-shater city and five sample plots 10 × 10 m measuring at 20, 40, 60, 80 and 100 m intervals were established from four main directions of each kiln. In both control (outside of the charcoal area) and sample area, above- and under-ground biomass of trees, carbon sequestration, grass cover, and soil were measured. The results showed that the highest and lowest amounts of soil carbon sequestrations were in the 0-15 cm depth of control (2762.0221 ton /ha) and 60 m distance from the kilns (1663.601 ton/ha), respectively. Also, the highest amount of carbon sequestration was observed in the control area (3.515 ton/ha) and the lowest was in the distance of 20 meters from the kilns (2.116 ton/ha). Results of carbon sequestration of herbal vegetation and litters also showed that there was no significant difference between distances and the control area. Overall, the results of this study showed that the carbon sequestration of the soil and the tree increases with increasing the distance from the charcoal kilns. Therefore, it is necessary to control and manage the charcoal production process in the Zagros forest.

Considering the degradation of large areas of lowland forests and decreasing tree density, it is assumed that nutrient cycle controlling factors and habitat dynamics also show significant changes. Accordingly, the present study aimed to study the effects of different intensities of forest degradation and tree density on the dynamics of soil microbial activities and biochemical processes. Following field inspection, three forest areas with degradation intensities of high (deforested area; including 8 trees per hectare), moderate (disturbed forest; including 185 trees per hectare) and low (protected forest; including 321 trees per hectare) with hornbeam and iron trees as dominant species, in the plain region of Noshahr city were considered. A total of 15 soil samples from each area were transferred to the laboratory and physico-chemical characters, microbial activities (i.e. basal and induced respiration, microbial biomass of carbon, nitrogen, and phosphorous) and nitrogen mineralization dynamic (i.e. net rates of ammonification, nitrification and nitrogen mineralization) were measured. The results indicate that the protected forest has higher microbial activity, net ammonification (both summer and fall), and nitrification (in summer) rates, which are related to higher clay, humidity, and also fertility under these land cover. Whereas, disturbed forest and the deforested area generally have lower microbial activity and mineralization processes. The results of the present study indicate that forest degradation has negative effects on many microbial indices and biochemical activities related to soil nutrient cycles.

Forest income occupies a significant proportion of total household income for many dweller communities in Zagros forests. The aim of this study was to investigate the livelihood dependence on forest in the Homian-Zaron area of Kouhdasht city in central Zagros. The sample size according to Cochran's formula was estimated 215 households in 30 villages. The households in each village were selected through random sampling. The socio-economic data of household was collected through a questionnaire, oral interviews with people and direct observations in 2018. First, the impact of forest income on household economy was estimated and then the poverty line and poverty indices including headcount ratio, poverty gap, Foster- Greer-Thorbecke (FGT), Sen, Gini coefficient and level social welfare of households with and without forest income were calculated. Multiple regression was used to analyze the socio-economic factors influencing the economic dependence of households on forest. The result showed that households earn 34.91% of their total net income from forest. With the elimination of forest income, all poverty indices and Gini coefficient were increased and the level of household social welfare was decreased. The results of regression analysis indicated that household size and livestock value were positively and distance from forest, agricultural income and off-farm income were negatively significant and correlated with household economic dependence on forest. The research findings show that focusing on these factors can achieve a balance between improving livelihoods of poor rural and nomadic households and sustainable utilization of forest.

The earthwormis considered as one of the most important ecological indicators in assessing the soil quality of the soil ecosystems. The aim of this research was the investigation of forest land-use changes on the earthworm’s density and biomass related to the soil properties. For this purpose, 40 soil profile and earthworm samples were randomly taken from 0-25 cm in four different land-uses (Less-disturbed forest, disturbed forest, agricultural irrigated land (Medicago sativa) and orchard (Pyrus sp. and Malus sp.) in Baneh county forest's, Kurdistan province. The results showed that soil organic matter in different land uses decreased in all land uses compared to the less-disturbed (SOM=2.95 percent) forest. The disturbed forest dedicated the least amount of phosphorus and electrical conductivity than the other land uses. There were significant differences among other soil factors including nitrogen, C/N, potassium, pH, moisture, and gravel percent. In addition, the most and the least density of earthworms were belonged to the less-disturbed forest (204.8/m-3) and disturbed forest (44.8/m3), respectively. In general, the density of earthworms showed a positive significant correlation with their biomass as well as canopy percent and negative significant correlation with gravel and the soil rock percent. Increasing of earthworm’s biomass showed a positive significant correlation with the soil organic matter, nitrogen and moisture percent, and negative significant correlation with soil rock percent. As a conclusion, forest land-use changing and forest utilization have reduced the density of earthworms, which was decreased significantly in the disturbed forest and agricultural irrigated land compared to less-disturbed forest.

Among the various components of vegetation, root system plays an important role in stabilizing, soil reinforcement and preventing erosion. This study aimed to investigate the effect of oak decline phenomenon on root mechanical characteristics of Brant`s oak (Quercus brantii Lindl.) in Dinarkuh forests, Ilam province. Considering DBH distribution of the trees in the study site, five trees were randomly selected in small DBH (15 to 35 cm) and large DBH (35 to 55 cm) classes within three treatments of healthy, moderate decline, and severe decline. Root samples were collected from each tree by digging near the tree and then tensile test were performed in the laboratory. The results showed that the root diameter-force strength relation was positive power-law and the root diameter-tensile strength relationship was negative power-law. Results of the covariance analysis for tensile force and strength showed that there is no significant difference between tensile force and strength among treatments of small DBH class, while in large DBH class, root tensile force and strength of healthy trees were significantly higher than trees with severe decline. Based on the decline, tensile force of the trees in the treatment of severe decline compared to the healthy trees, so force decreased by 11.3% in the small DBH and 22.7% in the large DBH classes. Also, these values ​​for tensile strength showed a decrease of 13.4% and 19.7%, respectively. The findings of this study show how the effect of forest decline on the root tensile force and strength values ​​leads to a better knowledge of the controlling soil erosion in the Zagros ecosystems.

This research aimed at determining the economic planting interval, planting pattern, and rotation age for high-yield black poplar in the West Azerbaijan Province, Iran. For this purpose, a decision support system called the bio-economic model was employed. The model simulates the dynamics of stand’s bio-economic variables over time. The statistical population consists of poplar farmers and timber merchants in Orumiyeh and Naghadeh counties where black poplar plantations were highly concentrated. Biological data were collected using full calipering inventory (diameter) and systematic random sampling (height and wet wood density). The economic data (stumpage price and costs) were obtained through a field survey based on a semi-structured interview. Multiple regression analysis and OLS estimator were used to estimate the biological (e.g., growth and yield) and economic (e.g., planting cost) sub-models. By integrating sub-models within an Excel spreadsheet, a bio-economic model was constructed for black poplar plantations. Finally, land expectation value (Faustmann formula) was simulated over a wide range of planting intervals, planting patterns and rotation age. As a result, the economic planting interval/pattern and rotation age of average-fertility plantations appeared to be square, 2.5´2.5 meter and 12 years while the common standards are rectangular, 3´1 meter and 8 years, respectively. The results revealed that implementing economically optimal planting and harvest standards increase the per-hectare merchantable volume production, quadratic mean diameter and land expectation value by 56, 46 and 143 percent, respectively. Further research will be required to model and to optimize the growth response of poplar plantations to management activities (e.g., ploughing, fertilization, irrigation, vegetation control, and thinning).

Urban vegetation monitoring can play a vital role in sustainable city management because of their diverse environmental, social, cultural, and economic functions. In this study, the vegetation trend was assessed using the Normalized Vegetation Difference Index (NDVI) obtained from the Landsat 5 and 8 at a maximum vegetation greenness time by applying a parametric approach (i.e. Ordinary Least Square Linear Regression) and a non-parametric approach (i.e. Theil-Sen and Mann-Kendall) over Tehran city during 2008 - 2019. The MOD13Q1 NDVI product was used as a complementary data due to the lack of appropriate Landsat data for 2011 and 2012. The data collected from four synoptic meteorological stations located in Tehran were used to extract the mean temperature and the total precipitation parameters. The relationship between NDVI variations and climatic characteristics, i.e. the mean temperature and total precipitation of one month before and one year before the maximum NDVI values were analyzed. The NDVI trend analysis showed a slight increase in Tehran vegetation cconditions during 12 years, however, the result of the Mann-Kendall test was not statistically significant (α = 0.05). Trend analysis for 22 individual districts showed a significant negative trend for five districts, and the remaining districts showed a non-significant trend. The NDVI was negatively correlated with temperature, and there was a positive correlation between NDVI and precipitation. The NDVI variations showed a more similar trend to the climate data of one month before NDVI data-set than one year.

This study was carried out to analyze the performance of natural resources cooperatives in Paveh County, Iran. Cochran’s formula was used for determining the population sample size among members of active cooperatives in the study area. Data was collected using a fully structured questionnaire whose validity confirmed by both faculty members of university and cooperative organization experts. Cronbach’s alpha coefficient estimated through a pilot study was used for measuring the reliability level of questionnaires. Correlation analysis and stepwise multiple linear regression were used to analyze the data. Pairwise comparisons indicated that social, economic and environmental factors were respectively the most important criteria contributing to cooperative successful performance. According to results, all independent variables displayed significant positive correlation with success of cooperative, so that factors transparency of organizational duties and belief in teamwork were maximum and minimum correlated factors from cooperatives members’ viewpoint. Regression analysis revealed that some factors were significantly influenced the performance of cooperatives. Five independent variables were entered into performance model of cooperatives which transparency of organizational duties with a standardized beta coefficient of 0.305 was the most important variable influenced cooperative performance. Relative success index indicated that performance rate of all cooperatives was lower than 50% (minimum 33.8 and maximum 44.6%). The results of this study can be used to identify the strengths and weaknesses and planning actions needed to rebuild and reactivate the cooperatives.

Oak decline has occurred along the Zagros forest from 10 year ago. In the current study, situation of tree decline of Brant`s oak (Quercus brantii Lindl.( of Kohmareh Sorkhi, Fars was assessed. The two affected stands by dieback in north and south aspects were identified and then two plots with variable areas were set so that 100 individual trees can be found in each plot. Moreover, two unaffected stands in the same geographical aspects were found and the same plots set as controls. Then, tree dieback severity was classified into four groups including fully health trees, sign of dieback just in upper parts of branch, dieback into the crown but less than 50% and finally dieback into the crown but more than 50%. All the oak trees within the sample plots were classified according to the four groups. Also, some tree characteristics such as origin (seed or root), coppice number, DBH, height and leaf area and dry biomass were recorded for all the trees. Also, we measured soil moisture content in all the plots. According to the results, around 11% of the trees in each affected plot belonged to the severe tree dieback group. Most of the moderate and severe dried trees were occurred in medium classes of diameter and height and their distribution follow a bell-shaped. Furthermore, soil moisture content in control plots were higher than dieback plots. Mean of leaf area and biomass of control plots were greater than those affected plots by tree dieback. Totally, there was no any significant difference in tree dieback rate between north and south aspects but it seems that moisture level is one of the key factors in tree dieback prevalence.