Iranian journal of Forest
Year:2015 | Volume:7 | Issue:1|Papers Count:12

The study aims to estimate the canopy storage capacity (S) and the ratio of mean evaporation rate from the wet canopy to the mean rainfall intensity (`E/`R), and the free throughfall coefficient (p) of Pinus eldarica (44 years-old-age) afforestation using three regression-based methods (Minimum, Gash and Morton and Mean methods) in the Chitgar Forest Park, near Tehran, with a semiarid climate zone. To measure gross rainfall (GR), 10 rain gauges were fixed in an open space nearby to the stand and throuhgfall (TF) was measured during a year using the 50 rain gauges randomly placed underneath the canopy cover. Rainfall interception (I) was computed as the difference between GR and TF. Fifty rain storms were recorded with a cumulative depth of 262.5 mm. The TF and (TF: GR) % were recorded 69.5% and 53.2% of the rainfall event on the cumulative-based, and event-based (each GR), respectively. Positive logarithmic correlations were observed between (TF: GR) % and GR during the study period (TF: GR = 16.598 1n GR + 35.494; R2 = 0.630). For dry (from May to November) and wet periods these values corresponded to 0.988 and 0966 by positive linear correlations. The mean value of S, `E/`R, and p were estimated 1.23 mm, 0.10, and 0.19, respectively. Since measurements of the amount of GR and I are expensive and time-consuming in semiarid and arid regions, and attended measurements in the field are currently carried out, thereto, regression models for estimating I and its components, e.g., S, p, and `E/`R coefficients can successfully been applied.

Site productivity is a key indicator of forest ecosystem; therefore it is an important criterion for forest manager for estimating the yield, annual exploitation and growth, and choosing the most suitable tree species for sites as well. In this study site form index which is the most reliable criterion for evaluating site productivity of mixed and uneven stands was used. A random-systematic sampling method was used to locate 43 0.1 ha circular sample plots in beech dominated forests. The height and diameter of Fagus orientalis Lipsky trees with DBH³7.5 cm within each plot was recorded along with elevation, azimuth and slope of the ground. Also, at the center of plot, soil samples from first layer (0-10 cm) were taken for analyzing several soil variables. Evaluation of site productivity by using generalized additive models in GRASP package in R 2.9.2 software showed that 53% of variability in oriental beech productivity could be justified using environmental variables. Bulk density, altitude, percent of slope, percent of silt, carbon to nitrogen ratio and saturation are among the significant variables affecting the site form. By using relative importance criterion, the alone contribution showed altitude had the dominant role, but the overall contribution of the slope percent was the highest in relation to other variables. Using AIC, RMSE, R squared and adjusted R squared showed GAM performs better than GLM.

Proper and efficient management of forests requires adequate knowledge of environmental factors and their impact on vegetation. This study aimed to develop a model of the spatial distribution pattern of Cercis griffithii based on physiographic factors (slope, aspect, altitude, and distance from river and determine the most important factors influencing the distribution of physiographic love tree and prepare the spatial distribution map of this species. Therefore, the slope, altitude, and aspect maps and also waterways map in GIS environment using digital topographic maps of the study area were prepared by the scale 1/25000. To examine the effects of environmental variables and model the distribution map of the species, logistic regression was used. The results showed that altitude and the distance from waterways had significant relationship with the distribution of Cercis griffithii. Modeling was performed based on two variables that were significantly associated with the distribution of this species and coefficients obtained from the logistic regression analysis. Nagelkerke R squared and ROC of the model were 0.556 and 0.871, respectively, which demonstrate the proper accuracy and credibility of the logistic model in species distribution modeling.

This paper intended to introduce the pioneer and medicinal sea-buckthorn shrubs for the first time. The effects of different treatments on seed germination seeds of these species were studied in the laboratory. Seeds of Qazvin origin were placed in Petri dishes in germinator after anti-infection and pretreatments. Seed treatments including 1) control, 2) temperature, 3) ice water; 4) hot water 5) lime juice 6) gibberellins were sown in a completely randomized design with four 25 seed replicates. At the end of the experiment, indices of germination percentage, mean shoot length, mean root length, coefficient allometry, shoot number, root number, mean day germination, energy of germination, rate of germination and seed vigor index were calculated. Average germination percentage of treatments for control, cold, ice water, hot water, lime juice and gibberellins were 33, 12, 41, 4, 9 and 32, respectively. The result of ANOVA showed that highest percentage of germination percentage, shoot number, root number and seed vigor index were observed in water ice treatment. The highest value of mean shoot length, mean root length, rate of germination and least value of mean day germination were observed by gibberellins treatment. Allometry coefficient in cold treatment showed the highest value and the highest germination energy was seen in control treatment. Lowest traits occurred mostly in the hot water treatment except mean day germination. Further research suggests for Hippophae rhamnoides L. due to drought tolerance, nitrogen fixation effect and its unique pharmacological properties.

The first sign of any stress in trees usually appears in the status and morphology of the crown. Therefore, the cause of disease symptoms or oak decline in Zagros forests could also be checked by the status of the crown. For this purpose, 223 oak tree (in four levels of healthy, low, moderate and severe declines) in Meleh Siah forest, Ilam province were randomly selected in 12 0.25 ha square plots in three random transects. Total height, crown dimensions such as two vertical crown diameters, crown height, crown density and crown dry branches, general health status, and level of contamination to pests and diseases of trees in each plot were recorded. Crown area (canopy), crown ratio (live crown length to tree height) and crown volume were also calculated. For data analysis, one way ANOVA and Duncan's test were applied by using SPSS software. The results showed that about 57% of the oak trees in the region have low to severe declines. Analysis of the data suggests that the relationship between the decline and the crown ratio is not significant. However, the parameters of the crown area, crown density, crown length and crown volume is significant at 99%, so that large crowns have shown more damage. Crown density index showed the highest correlation with the degree of decline, so that closed canopy has shown fewer declines. Thus sparseness of oak trees canopy could be considered as a good indicator for the risk of tree decline.

Relatively little information concerning energy derived from biomass and potential influenced variables causes uncertainty in models for energy policy and environmental conservation. About half of the world's populations, who often live in developing countries, are depending on solid sources of energy such as biomass and coal. Given Iran’s rich reserves of fossil fuels, it is not expected using solid fuels such as firewood. However, due to the deficiency in distribution system, rural poverty and subsistence economy, wood burning is common more or less. The demand for wood as a source of household energy comes from everyday decisions which Influenced by the household budget, relative time spending, prices of other energy sources, as well as social and cultural factors. The aim of this paper is to estimate the demand of hardwood as fuel in rural area of Caspian forest, northern Iran. Almost Ideal Demand System (AIDS) model and data from household budget survey (1991-2010) has been used to estimate the demand of firewood. Prices of fuelwood, kerosene, gasoline, and natural gas have been derived and separately considered in the model. The results showd that price elasticity of demand is negative in all commodities. Kerosene and gasoline are substitute and gas is complementary goods for fuelwood. Also price index of food, house, and gasoline were elastic, their price elasticity were -1.22, -1.03, and -1.36, respectively. According to the results, firewood own price elasticity was -0.29 and Income elasticity was 1.34.

To evaluate the morphological effects of pollarding on Lebanon oak (Quercus libani Oliv.) leaves, we selected 35 trees in untouched stands and stands which have trees with one, two and three years after pollarding. Trees selected from three diameter classes in which 24 mature leaves collected randomly from the middle of the crown on each cardinal points (840 leaves in total). Data was analyzed using simple nested experimental design. Results showed that, oak trees produce larger (21.704 cm2), and heavier leaves (0.251 gr) one year after pollarding in comparison with untouched trees. Trees in smaller diameter classes and on northern cardinal point, produce larger and heavier leaves with larger specific leaf area, which shows the ability of younger Lebanon oak trees and northern cardinal aspects to produce more fodder. These results can help us to interpret the pollarding consequences on oak trees in northern Zagros.

The aim of this study was to investigate the effects of understory cultivation on the quantitative and qualitative characteristics of Quercus brantii Lind1 and oak decline. For this purpose the Barm plain (east of Kazeroon city) where there is trees susceptible to drying, were selected. Then three conventional land use (land use with understory cultivation, land use without understory cultivation, land use with protected) were selected using topographic maps and field survey. For each land use, 30 rectangular sample plots (0.2 ha) were selected and the quantitative and qualitative characteristics of trees were recorded. In order to better analysis, the decline of trees were classified to four classes (less than 25%, 25% to 50%, 50% to 75% and more than 75%) based on the percentage of decline. Data analysis showed that the most of dried trees was coppice type and most of decline was found in crown area as well as land use along with understory cultivation. Also the maximum number of dried trees observed in classes of more than 75% along with understory cultivation. While the dried trees were recorded 25% in land use with protected and without understory cultivation. Results of this research confirm that the understory cultivation has an important role in complete decline of trees and damage caused by secondary factors such as pests and diseases is more in the land use along with understory cultivation.

The use of ground-based skidding is well accepted practice for the extraction of timber from the forest, but this has tended to cause the greatest environmental problems. We test the hypothesis that, over time, there was a statistically significant difference among the progressive decay and wound healing or closure in the residual trees of different species. The present study aims to address the following items: proportion of the remaining trees, how extensive is the spread of wound decay in individual stems by wound size and wound age. Long-term impact evaluation on residual damaged trees was carried out in the Tavir forest management plan in Aliabad-e-Katoul. Variation in wound infection frequency could be attributed to several factors, such as differences in size and age of wounds, position of wound on a tree. The results showed that there was a significant relationship between the species type and amount of healing. By increasing the diameter of the tree species, the ratio of healing decreased. By increasing the height of wound from the stump, wound-healing rate increased. The results showed that the deep wounds of the trunk will be healed later than superficial wounds. Regardless of the type species, by increasing the size of the wound, the wound healing significantly (in a logarithmic relationship) was reduced. The results showed that there was not a statistically significant relationship between scar closure and wound age. Damage to the residual stand might be reduced by proper planning and training the logging crews.

The diameter at breast height of tree is one of the important characteristics in forest measurements. Diameter structure of forest stands can be determined based on diameter distribution. The distribution of diameter classes is the most important structural characteristics of forest stands. The aim of this study was to evaluate the DBH probability distribution of Quercus persica trees in Dalab open forests of Ilam province. For this purpose, 37 transects with fixed length (50 m) were measured and trees distribution in diameter classes for 209 trees were fitted. The probability distribution functions including: Beta, Gamma, Normal and Log-normal were fitted to the DBH distribution of oak trees. The maximum likelihood estimator was used to evaluate the distribution functions parameters. Expected probability and probability derived from functions were compared using Kolmogorov-Smirnov and Chi-square tests. Results of fitting tests and P-P plots showed that Beta and Normal distributions were the best probability for diameter distribution modeling in Dalab open forests of Ilam province.