مجله جنگل ایران
سال نهم شماره 2 (تابستان 1396)

Large ecosystems such as forests with large amounts of biomass play important roles in carbon sequestration, mitigation of CO2 emissions and human life. The present study aimed at estimating the amount of carbon storage in four land use systems (intact, protected, exploited and garden) in northern Zagros forests, western Azarbaijan province. Within each land use in the same unit, 30 sample plots were established and some quantitative characteristics, such as diameter of all trees with DBH > 10 cm were measured. Total height of largest DBH, tree closest to the center of the plot, diameter of crown along two perpendicular directions and the thickest closest tree in each plot were also measured. The litter samples were taken based on direct sampling in 0.5*0.5 m sample plots at the center and four corners of the plot. The results showed the total biomass in intact, protected, exploited and garden land uses were 450.12, 54.95, 12.85, and 5.38 tons per hectare, respectively. The amount of carbon stored in the land uses were 258.15, 35.52, 9.49 and 3.48 tons per hectare in in intact, protected, exploited and garden land uses, respectively. The results of Duncan test also showed there are significant differences in biomass and carbon storage among different land uses.

This study aims at observing the long-term trends of meteorological parameters and ET0in Caspian region, North of Iran. The long-term trends of meteorological data (1961-2008) were obtained from five synoptic meteorological stations, i.e. Gorgan, Qaem Shahr, Babolsar, Ramsar, and Anzali located throughout the Caspian region. In order to observe the trends of meteorological parameters, the region was primarily classified into five climatic zones based on De Martonne climate classification index (IA). The FAO Penman–Monteith combination equation was applied to calculate the ET0. The Caspian region was categorized in five climatic classifications as Mediterranean (Gorgan), semi-humid (Qaem­ Shahr), humid (Babolsar), very humid, type 1 (Ramsar), and very humid, type 2 (Anzali). Our results indicated that trends of air temperature were significant within the past half-decade so that it was increased (0.74ºC) during the two past decades. As well, wind speed showed significant increasing trends in all stations and increased 1.1 m.s-1 as average. The ET0 has been raised 0.4 mm.d-1 in Caspian region since 1988 and IA decreased from 39.5 to 36.8 showing the region is getting warmer and drier. Changes in meteorological parameters and ET0 will definitely affect the function of natural and artificial ecosystems. It is essential for managers to think of expected changes while planning for future development in Caspian region.

In order to study the beech scale and some of the effective environmental factors on beech scale density on eastern beech trees, after field inspection, 10 hectare of infected beech stands were specified in low-, mid- and high lands of Kheyrud forest. At each studied area, 12 scale infected beech stands were randomly determined and their characteristics were recorded in special papers. Effect of bark roughness and direction of trunk of beech trees and height from the ground on beech scale density and period of infestation in three studied areas were investigated by using non-parametric Kruskal-Wallis and Friedman tests. Completely rough barks having deep cracks were assigned highest density of beech scale by 5.5 average. Beech scale density at north and east sides of trunk was significantly more than south and west sides. Also, density of this scale at 2.5 m height of trunk was the greatest by 4.4 average. With increasing elevation from sea level, infected stands initially increased from 23.8 to 28.3 percent and then decreased to 15.4 percent. Beech scale density was most in high land by 30 percent high density and also beech trees infection length was highest in middle land and high land by 5.35 and 7.5 m, respectively diameter class 40-60 cm was recognized as the best diameter for colony formation of beech scale by 36 percentage infection frequency and 38 percentage high density.

Single tree selection method needs to an accurate estimation of logging damage to residual stand for ecological and sustainable forest management. In this research accuracy and required time for estimation of frequency of damaged trees due to logging operation were assessed through plot and line samplings in a harvest unit of 30 ha area in Asalem Nav forest, northern Iran. In both samplings with same sampling intensity (10% of total area in plot sampling and equal total line lengths in line sampling) five samples size (plot and line sample numbers) were applied with different grid dimensions of systematic sampling method. The results showed that the sample size had significant effect (P 0.618) with actual damage (100% inventory). Adequate grid dimensions were determined 100 m × 100 m with plot areas of each 0.1 ha for plot sampling and 77.5 m × 77.5 m with sample line lengths of each 60 m for line sampling. Required time for line samplings were about 90% lower than plot samplings. These results indicate the line sampling can be used for accurate and rapid estimation of frequency of damaged trees due to selection cutting and ground skidding.

Among ecological communities, insects are important bio-indicators of wildfire disturbance due to their sensitivity to environmental changes and habitat requirements. In this research, we studied the relationship between the temporal effect of wildfire and macro-fauna abundance and biodiversity in an oak forest located in Sardasht, West Azerbaijan. We compared three sites differing in fire history as well as three control sites. Fifteen samples (0.5× 0.5× 0.3 m) were selected for each above-mentioned treatment along transects in both burned and control plots. Totally, 210 insect specimens belonging to 18 orders and 27 families were collected. We applied analysis of variance and Duncan test for the analysis of normal continuous data and chi-square test for the analysis of discrete data or abundance. Results indicated that the occurrence of fire reduced the richness of macro-fauna in the burned areas compared to the control areas, but the temporal effect of fire on the macro-fauna resulted in increasing of the richness of the macro-fauna in years after fire occurrence. Both Coleoptera and Diplura were also present in all study area and wildfire had no effect on Diplura. But the temporal effect of fire on Coleoptera was evident and the abundance of this order was added by passing the time of the fire. Diptera and Ants (Hymenoptera) also, over time, had been returned to the burned areas and their frequency has been increased. So the return of insects to their habitat needs over a period of time about 1 to 2 years by improving the microclimatic environment and the regrowth of plants.

The climate is determinative of the soil and flora and fauna of a region and in wide scale causes variation in ecosystem and the species combination. In this study, distribution of Juniperus excelsa were studied on the current and future climate condition(2050, 2070) under two climate change scenarios of Rcp2.6 and RCP8.5 with the GCM dataof HadGEM2-ES by using of MaxEnt model. 22 variables of climate and topography in 160 sites were employed . The resultsshowed that in addition to height above sea level, precipitation in coldest season and annual mean temperature are the next important variables on Juniperus excelsa distribution. Also the results show that if the current trend of climate change continues, habitat area of species under the scenario of RCP2.6 till 2070, increases in middle habitat class (82.4%), in good and very good habitat classes, 31.3, 67.3 percent, respectively, and will be reduced and under the scenario of RCP8.5, faces with too much decreasing the area (in middle, good and very good habitat classes, 76.5, 98 and 100 percent, respectively). According to the results , the models like MaxEnt, with acceptable accuracy have enough performance in evaluation of species distribution and can be used for strategies of conservation by the experts.

In this study a pre-stratification was applied to estimate quantitative attributes of oak forests by cluster sampling method in Bayangan district, Kermanshah province. Firstly stratification was conducted according to NDVI on landsat-8 images and four strata were determined. Sample size was computed according to allowable error and samples were allocated to three strata with regard to their heterogeneity. Totally 34 five-plot clusters include 170 samples with 90×90 meter dimensions were measured in 30000 ha area of study area. Crown diameter and diameter at breast height (DBH) were measured and finally density, crown cover and basal area per unit area were computed. Results of stratified sampling showed 149.5 tree, 1367.6 m2.ha-1 (13.67 percent) and 3.21 m2.ha-1 for density, crown cover and basal area respectively. While this measures for cluster sampling without stratification were 221.8, 2013.5 and 4.77 respectively. This was due to high acreage (weight) but low density and crown cover in the first strata with huge effect on forest mean. Error percent was 1.74, 2.65 and 3.14 for pre-stratification status and 9.11, 9.14 and 9.33 for cluster sampling without stratification. It can be said that pre-stratification can decrease sample size from 66 to 80 percent. We conclude that with regards to heterogeneity of Zagros forests in type, density and crown cover, pre-stratification can improve precision of cluster sampling and is recommended for general inventories.

The tending operations are essential for the quantitative and qualitative improvement of forests and thinning as the most important step has a significant role in increasing the growth of trees. In this research, the even-aged alder(Alnus subcordata) and Persianmaple (Acer velutinum) stands located in Chendella district in the north of Zirab city in Mazandaran province were investigated to compare the effect of thinning on diameter growth. Three executive rotations were done in these plantations. Close to each plantation, one stand which has received no thinning treatment was selected as the control to compare the effect of thinning treatments on tree characteristics. The D.B.H and other growth parameters of 318 trees were measured. In this investigation 2 or 3 individual trees in each 5cm diameter class (totally 45 trees) were randomly selected to obtain the disk at 20 cm, 130 cm and full length heights for measuring the diameter growth rates. Medium diameter and total height of the tree were measured to calculate the diameter growth of the trees. The Student t-test with SPSS software was used to compare the quantitative characteristics of each of the forest plantations and the control. The results of this study showed that the average DBH and average diameter growth of both species in the thinned stands were higher than the control stand. Also, the mean DBH and average diameter growth in the treated and control stands of alder were more than the treated and control stands of Persian maple. However, the slenderness index of Persian maple trees in both treated and control stands was greater than that of the treated and control alder stands.The results of this study showed that the positive effects of thinning operations on the silvicultural characteristics of alder stands were much more than maple.

This study aims to estimate the economic benefit of the environmental improvements in the Hara forests of Qeshm using choice experiment method. Improvement in the environmental status were defined within the framework of three related attributes and the respondents were asked about their willingness to pay for conserving and improving the mangrove forests in this area. The obtained data were analyzed using conditional logit model. Results showed that about 78 percent of respondents are willing to pay for environmental improvement alternatives. The attribute of bird species number in the Hara forests provides the highest probability for the visitors to pay for an improvement level (89790 IRR per household per trip). Additionally, females, older and married respondents as well as those with higher educational level are more likely to participate in environmental conservation programs. Our valuation results can help to increase public awareness about the multiple values of mangrove forests and contribute to better-informed public decisions. It also allows policy-makers to prioritize conservation programs and projects with limited and tight budgets.

Forest resources play an important role in welfare and poverty reduction in rural and nomadic areas, since forest dwellers have less income and development than other people, and this affects their use of forest resources and leads to resource degradation. From the past, the Zagros dwellers have used wood and non-wood products, and these products have played a major role in their economy. In this study, an attempt has been made to determine the economic dependencies on forests in the forests of Sardasht, Lordegan city in central Zagros. The approach used in this study was a quantitative description and analysis using semi-structured interviews. First, the impact of forest income on household economy was investigated, and then the poverty line and poverty indicators including headcount, poverty gap, Foster, Greer and Thorbecke, Amartya Sen and the Gini coefficient were calculated and evaluated. The results showed that the people of the region have nine livelihood strategies, where the income from labor is first, and the forest with an annual income of 27 million Rials per household has the second share of the economy with 18.07%. The poverty frequency was 76 percent which has reached 88% by eliminating the forest income, and 12% of households have been moved below the poverty line, causing an increase of 1.54 times of the poverty depth. Foster, Greer and Thorbecke coefficient was estimated 0.15 that after removing the forest income, it was 0.23. In addition, removing forest income will increase 11% in unequal distribution of incomes. It is necessary to determine the correct strategies to reduce the forest dependence by replacing the appropriate action and, as a result, reduce the amount of forest degradation.