مجله جنگل ایران
سال یازدهم شماره 3 (پاییز 1398)

Forest machinery traffic on forests causes significant changes in increasing the bulk density, reducing porosity, ventilation and reducing water infiltration rate which resulted in an increasing surface runoff. According to the results of previous studies on the effect of mulch on reducing runoff in laboratory conditions, The aim of the present study was to determine and compare the amount of runoff produced in untreated skid trail, undisturbed forest (control area), and the skid trail plots covered by sawdust, under natural conditions in Namkhaneh District, Kheyrud Forest to find useful strategies to reduce the effects of forest utilization in order to maintain the function of forest water protection and reduce runoff. In this study, the runoff plots (6 m2) were triplicate established and runoff collected by pipes in the outlet plots were measured based on natural rainfall conditions. The results revealed that applying sawdust mulch to the skid trail decreased runoff compared to the untreated skid trail, and the runoff amount in undisturbed forest, untreated skid trail and sawdust mulch treatments were 0.40, 1.44 and 0.71 mm, respectively. The highest and the lowest amount of runoff were found for untreated skid trail and undisturbed forest treatments, respectively. Also, by application of sawdust mulch, the amount of runoff produced reduced by 48.4%, while the amount of runoff before the use of mulch in skid trail was 72.2% higher than the intact forest. Also, the runoff produced in skid trail control treatment was 51.1% higher compared to sawdust treatment.

The aim of this study was to evaluate the impacts of dust on the morpho-physiologial traits of Fraxinus rotundifolia Mill. seedling, a useful species in urban green space. In a greenhouse, a dust stress was applied using dust simulator with concentrations of 0, 750 and 1500 μg m-3. Experiment was conducted by a completely randomized design with 5 replicates (9 seedlings in each replicate) within 45 days with one-week interval.) . Dust deposition with 1500 µg m-3 concentration caused the appearance of symptoms of chlorosis and necrosis on leaves. This concentration decreased the amount of survival (29%), increment diameter (38%) and height (33%), average leaf area (19%), photosynthesis rate (45%), transpiration (60%), stomatal conductance (46%), mesophyll conductance (55%), spad index (23%), Fm (22%), Fv/Fm (22%), T1/2 (14%)increased intercellular CO2 concentration (22%), water use efficiency (40%), leaf temperature (2.34 oC) and Fo (30%).  For afforestation and tree planting initiatives in dust-polluted areas of urban and suburban regions of Iran,  F. rotundifolia seedling can be usefully used in areas where dust concentration is less than 750 μg m-3.

One of the most important factors for determining the volume of trees is selection of an appropriate form factor. This study determined the most appropriate form factor formula and modeling the actual form factor in the Caspian region of northern Iran, Guilan’s forests. Totally, 150 beech (Fagus orientalis) trees were measured. Three coefficients of natural, artificial, and Hohenadel were compared with the actual form factor using pair-wise comparison test. Several nonlinear equations including logistics, Chapman-Richard, and exponential functions were used for modeling the form factor of beech trees. These functions were evaluated in terms of coefficient of determination (R2), paired t test, and accuracy statistics of ME, Root Mean Square Error (RMSE), MEr and RMSEr. The result showed that there were significant differences between the actual form factor and   the each mentioned coefficients. None of the models presented high R2 values. Accuracy statistics showed that exponential and logistic models can be usefully applied for estimation of the actual form factor coefficient. Also the results of t-test showed that there was no significant difference between of actual and estimated means of form factor derived from the logistic model. Therefore, logistic model was selected as the best for the estimating form factor of beech trees in Guilan’s forests of the Caspian region.

Humus systems are the largest part of organic carbon stock and play an important role in forest ecological processes. Elevation by influencing on the biological and non-biological properties of the forest ecosystem is an important factor for assessing the changes in the trees and distribution of humus systems. In this study, the morphological and chemical characteristics of humus forms in three altitudinal levels (500, 1000, and 1500 m.a.s.l.) and three transects which were 1000 meters apart were investigated. In each transect, 3 plots with 400 m2 area were sampled, and in each plot 5 profiles of humus (in total of 135 profiles) were examined in the central Hyrcanian forest. Humus and samples were taken and transferred to the laboratory for chemical analysis. The results showed that the presence of Iron wood (Scientific name??) and ash (Scientific name??) trees mull humus forms and soil nitrogen stock decreased by elevation increasing. Hornbeam (Scientific name??) and maple (Scientific name??) trees, organic layers' nitrogen, mesomull and leptoamphi humus forms demonstrated strong correlation with the 1000 m elevation. The number of beech trees, carbon in soil and organic layers, organic layers' thickness and humus Amphi forms showed a strong relationship with each other as well as with elevation increasing.  The effect of elevation on the composition of the trees coverage is accompanied by the variability in morphology and chemical characteristics of humus forms, so that by identifying tree species in every altitude, we can recognize the quantitative and qualitative properties of humus and soil.

This study aimed to evaluate the structural characteristics of Quercus macranthera forests in the Arasbaran region, Hatam Mashe Si, Meshgin-Shahr. To achieve this, all trees and shrubs were full calipered in three one-hectare plots. Additionally, the structural characteristics were measured using the nearest neighbor’s method. To measure intensity of trees, several indices like nearest neighbor distance index (density of trees), uniform angle index and Clark and Evans index (variety of location), Mingling index and Shannon-Wiener index (tree diversity in diameter classes), diameter and height differentiation indices (dimensional differences of trees), and complex structural diversity index (tree diversity) were used. The results showed that Q. macranthera represented a relatively homogeneous structure in its main site, and the mean of distance to the neighbors was 2.59 m. The results of uniform angle and Clark and Evans indices showed that the spatial pattern of trees was regular. Mingling and Shannon-Wiener indices showed a low tendency of Q. macranthera to mix with other tree species so that the majority of trees were Q. macranthera. The height and diameter differentiation indices illustrated that the dimensions of the trees had a slight difference. According to complex structural diversity index, tree diversity was at the medium level. It can be concluded that the Q. macranthera communities have a homogeneous structure in a study region with a low mixture and single canopy layer. The information can provide the opportunity to monitor future changes in Q. macranthera communities in this region. To promote ecosystem stability, it is suggested to create heterogeneity of stand structure and support other tree species in this area.

Importance of Juniper trees for forest rehabilitation programs was resulted in direct, seed sowing of Juniperus excelsa as a safe method to expand juniper forest areas and rehabilitation of deteriorated forests. This study was done to determine the effect of canopy and its geographic orientation on seed germination as well as survival of seedlings in the Sirachal research station. Collected seeds from Sirachal habitat were sowed in four main geographic orientations under canopy’s edge and 1.5 meter out of canopy as completely randomized blocks in split plots. Data analysis showed that canopy (P<0.05) and its geographic orientation (P<0.01) had significant effects on seed germination. In addition, the effect of geographic orientation of canopy on seedling survival was significant (P<0.01).. The interaction of canopy and its geographic orientation on germination of seeds and survival of seedlings was not significant. The highest seed germination percentage was observed for seeds sowed under the canopy’s edge and in the north direction.  The highest percentage of seedling survival was observed in the south followed by the north and east directions of the canopy. Despite the higher germination and survival percentages under the canopy’s edge, it is suggested to sow seeds out of trees canopy and in the north direction as seedlings have no chance to survive under the maternal trees canopy for longer periods.

Hyrcanian forests, which are located mainly on the northern slopes of Alborz are very important in terms of their specific features. Consequently, studying the evolution of these forest communities and their vegetative status can help planners and managers in tending forest stands. Growth and product models, which describe the dynamics of the forest, are widely employed in forest management to predict future products and to study management options. This study was conducted in Jojadeh section of Farim forest in northern Iran. Individual tree growth models including individual tree diameter growth, individual tree height growth, individual tree survival growth and individual tree regeneration growth were investigated in this study using 313 permanent sample plots (0.1 ha) in two 10-year periods. Competition in the stand was investigated by basal area and basal area large in the stand. Results showed that in the diameter model, the increase in diameter up to 90 cm was dependent on the diameter at breast height i.e. the diameter growth increased with the tree diameter; however, it decreased after attainment of 90 cm diameter. Oak and Maple trees had the highest diameter growth. In the height model, species type had no effect on the height model. In the survival model, the survival probability of alder species were lower than other species. In addition, the regeneration decreased with the basal area of stand in the regeneration model. in the present study, we have attempted to present models that estimate and measure theexact diametergrowth, regenerationand survival without regard to age

In this research, the application of Artificial Neural Network or MLP method in the process Assignment of relevé-groups/ plant communities allocation was evaluated using Buxus hyrcana forests database. For this purpose, firstly, the ecological and sociological groups of B. hyrcana were determined using TWINSPAN and Braun-Blanquet method, respectively. The results of both numerical and expert based classification dendrogram of the B. hyrcana communities, which included seven levels of classification as primary groups/plant communities, were introduced to MLP. Then, with assignments in three sets of training (70%), test (15%) and validation (15%), the MLP classification was performed on each level of the two dendrogram. The results showed that by increasing the level of classification, the degree of adaptation of the MLP result to primary results of TWINSPAN (99% to 60%) and Braun-Blanquet (98% to 68%) from the cutoff level of 1 to 7. Results of sensitivity and kappa cross tab coefficients, except in 7 cut level, imply that the quality of MLP groups based on TWINSPAN primary ecological group is upper than primary Braun-Blanquet groups.Appropriate adaptation of the MLP results in Buxus hyrcana plant communities classification with the TWINSPAN and Braun-Blanquet ecological/syntaxa groups at the fifth cut level of both dendrograms indicate that application of MLP aim at a reliable results in plant community classification. So our result reiterate that MLP could be introduced as a suitable method in the assignment of releves to plant communities.

The inadequate production of existing poplar cultivations can be due to unfavorable planting, maintenance and harvesting operations. In order to clarify the defects in the above operations, in the 30 stands of poplar trees, the diameter, height, wood volume and wood volume growth per hectare and year were measured and calculated. Then some information including primary planting spacing, existing tree number per hectare, etc. were determined by field survey. In path analysis, the causal and noncausal relationships between the independent variables and the volume growth were determined and demonstrated the direct effects of each component on growth, along with their indirect effects on the growth. Results showed, the area of the stands varied from 0.3 to 4 hectares. In more than 60 percent of the stands, the planting spacing was less than 2 by 2 meters. In most of the stands the percentage of survival was less than 50%. Only 10% of the stands had more than 25 m3 wood per year and per hectare. Principle component analysis showed that decreasing the planting distance had the most important effect in reducing the annual growth. Irrigation intensity showed the highest positive correlation with annual growth. Also, initial density showed the highest negative correlation with diameter and height. In path analysis, initial density showed the most direct negative effect on annual growth. Irrigation intensity has the highest positive indirect effect on annual growth. According to the results, the main defects of poplar farming are low spacing and more irrigation intervals, respectively.

Zagros forests with an area over six million hectares are important for economic, social and environmental aspects. More than one million hectare of Zagros forests has been declined. This research was carried out by selecting six sites at different altitudes and slopes. At each site, 30 oak (Quercus brantii) trees were selected. Sampling was done at any point on a certain level with an area of 20 hectares.  It was achieved in June and October and 20 elemental parameters were measured. In order to investigate the relationship between ionomics and oak decline, oak stands were classified into healthy, endangered, and damaged bases. The results of univariate analysis of variance based on three factors of season, region, and crown health index showed a significant difference in the number of elements such as N, P, C, K, C / P, C / K, Fe, Ca, Mg, Na, Cu, Mn, Zn, Si in spring and autumn (P <0.05). Also, there was a significant difference among six sites examined for the amount of C, C / P, Ca, Mg, Cu, Mn, and Ni. In terms of health index, a significant difference was observed amongst N, P, C / P, K / P, N / K, C / N. The results of the principle component analysis indicate that the traits with the greatest effect on the explanation of the first component can be used as decline factors. The present study provided a precise estimate of the ionome characteristics of Iranian oak, in order to provide a suitable step for enhancing the ability of oak species to cope with environmental problems.