Iranian journal of Forest
Year:2009 | Volume:1 | Issue:2|Papers Count:12

According to forest ecosystem conditions in Hyrcanian forests, the fixed numbers can not be useful for determining forest roads right-of-way. Also, these numbers are frequently ignored by the executives and road constructors in order to preserve valuable trees and avoid cutting these trees on sensitive points such as cut slopes and fill slopes. In some cases that roads right-of-way is considered based on standard numbers, the vegetative characteristics of edge stands is determinant of real forest roads right-of-way. In this study the status of real right-of-way was evaluated based on earth working limit, vegetative characteristics of edge stands and different slope classes of hillside in Lat Talar forests. Results showed that the forest roads right-of-way increased with raising hillside gradient (P<0.05). The mean width of real right-of-way in type A (Fageto-carpinetum with 155 stem per hectare and crown cover 75 percent) and B (Fageto-carpinetum with 175 stem per hectare and crown cover 85 percent) were 15.10 and 14.21, respectively. The most overlapped area between real right-of-way and fill slope of roads was observed in slope classes 30-40 and 40-50 percent in both types and the lowest overlapped area were seen in slope classes 50-60 and 60-70 percent. Finally, the optimum right-of-way of forest roads was separately determined for cut and fill slope in steep slopes of Hyrcanian forests using chart models. This method decreases the rate of tree felling and increases the safety and permanency of forest roads.

In order to investigate the possibility of beech forest type (Fagetum) mapping using Landsat ETM+, its data from Chelir district (780 ha) in Khyrood forest, Caspian forests, Iran were analyzed. Geometric registration was applied using 14 ground control points based on digital topographic maps at 1:25000 scale. The RMS error obtained was less than half of an ETM+ pixel. In order to estimate the accuracy of the classified satellite images, a ground truth map covering 42% of the total area, was qualitatively prepared as strips after field inspection. Image classification was performed using original and synthetic bands (rationing, principal component analysis, tasseled cap transformation and fusion) for following four beech forest types: pure beech, dominant beech, mixed beech and non-beech types. Classification was performed using maximum likelihood, minimum distance to mean and KNN classifiers. The highest overall accuracy (35%) was obtained using KNN classifier. The main reason for low overall accuracy can be related to the kind of related classes and also spectral similarity between pure and dominant beech classes. Therefore, these two classes were merged and classification was done again. The highest overall accuracy, considering three classes increased the classification accuracy up to 51%. The results showed that the spectral data of ETM+ do not have a high potential for beech forest type mapping in heterogeneous and uneven-aged Hyrcanian forests, Because the type of considering classes in such a classification is based on one specie (here beech) whereas the abundance of spectral reflectance of other species is neglected.

The ruts on skid roads are the main factors causing water erosion in northern forests of Iran. In order to evaluate the reasons of this phenomenon, the skid roads in Pahneh Kola and Arzefon forests which are under management of Mazindaran wood and paper industry were selected, then 32 cross profiles were randomly chosen in 10 skid roads. The effects of factors such as stocking volume per hectare, understory vegetation, longitudinal slope, skid roads length, canopy, soil type, basin area of each profile and its slope were measured as soil changed. Results showed that there was no significant linear relationship between water erosion rate and profile distance from starting point, stocking volume and understory vegetation. But there was a significant positive correlation between rate of water erosion and basin area (p-value < 0.001), longitudinal slope of skid road and basin area (p-value < 0.01) and skid road length and tree density (p-value < 0.05). Also, the regions with open canopy, clay soil and litter cover in understory showed the greatest rate of water erosion.

Forest gaps size and created conditions within gaps are of great importance on biodiversity of understory vegetation. For this purpose and better understanding of biodiversity, different indices were used in highland forests of Lalis located in Nowshahr. Line transect method was used for sampling and plant abundances were also recorded. Forest gap areas were divided into four classes including 50 - 200, 200 - 400, 400 - 600 and > 600 m2 area. Pearson correlation was applied for indices and area classes. In total, 59 gaps were recorded and 24 species belonging to 15 families were identified in the studied area. Dryopteris affinis had the highest abundance in whole of the classes. The value of species diversity, richness and evenness indices showed highest correlation with increasing gap area with coefficient equal to 1.00.

Caucasian alder is one of the fast growing and native species planted extensively over the last decades in the north of Iran. In this investigation quantitative and qualitative characteristics of Caucasian alder was studied in the 19-years old pure plantation with an area about 10 ha (row spacing: 2×2 m), in Siahkal region (Guilan province). In this research random-systematic sampling method was used. The area of each sample plot was 400 m2 (20×20 m). Diameter at breast height (DBH), tree total height (TTH), crown height (CH), stem quality (SQ) and crown vitality (CV) were measured for all trees. The results showed that average density of trees was 2105 stem per ha and viability was 84.5%. Arithmetical mean of DBH, TT and CH were 13.11 cm, 13.8 m and 5.3 m for Caucasian alder, respectively. The mean annual diameter and height increment of trees were 0.66 and 71.54 cm, respectively. The mean standing volume and mean annual volume increment were 251.49 and 13.23 m3 per ha, respectively. Also the results showed that, from the viewpoint of SQ, 34.6%, 45% and 20.4% of trees were first, second and third classes, respectively. In light of CV 61.3%, 22.5% and 16.2% of trees were first, second and third classes, respectively. In general our findings showed that the amount of annual growth of alder trees in comparison with similar plantation is low, because silvicultural practices, specially thinning operations were not carried out in the studied plantation.

Eldar pine introduction to Iran dates back to many centuries ago. It has been severely changed in morphology in Khaf region and two different forms emerged. This study aims at using anatomical traits to differentiate Conical and Ball-shaped pines which are two new mutant forms of Eldar pine. The results of anatomical comparison showed that Conical-shaped pine is distinguished from two other pines in some valuable taxonomical traits, such as cross sectional form of needle, number of stomata on ventral face per unit area, number and position of resin ducts. Also the difference in characteristics like cuticle thickness, stomatal interval space in row, number of stomata per needle unit area, needle perimeter and length imply increasing the adaptation potential to aridity in Conical-shaped pine spec. nova in comparison with Eldar and Ball-shaped pines.

Cupressus arizonica is one of the most important species in forest plantation in degraded ecosystems and urban and suburb areas of Iran due to low ecological demands and tolerance against winter drought and summer heat. This research was done to determine the best time of sowing and to study the effects of irrigation and weeding in growth and shoot/root length and the percentage of seedling vitality in Zaghe nursery, Khoramabad. It was performed as complete randomized block and factorial design with three treatments; sowing date (autumn and winter), irrigation periods (2 and 4 days) and weed mechanical control (7 and 14 days) and four replications for 15 vases in each replication. At the end of the first growing season, biomass, shoot/root length and vitality rate were measured. The results showed the effects of weed control on biomass were significant and sowing date and irrigation was not. The effects of sowing date and composition of treatments on shoot/root length were significant. The maximum amount of shoot/root length was seen at autumn date and composition of treatments (autumn date, 4-days irrigation and 14-days weed control). The effects of mentioned treatments on vitality rate were significant and its maximum was observed in autumn sowing, 2-days irrigation and 7-days weeding. It is suggested for decreasing the cost of seedlings production in nursery, weed control should be done in long time and autumn sowing can be replaced with winter sowing for better organization.

At forest ecosystems, gross rainfall (GR) is partitioned into throughfall (TF), stemflow (SF) and results in canopy interception loss (CIL). In the present research, CIL, which is considered a major component of the water balance, was measured at the midland of the central Caspian forests, Kheyrud forest research station of University of Tehran. Measurements were carried out in a sample plot of pure oriental beech (Fagus orientalis Lipsky) stand with an area of 5625 m2. GR was collected using three manual collectors in an open area approximately 160 m apart from the study plot. Thirty six TF manual gauges were randomly placed beneath the beech canopies and SF was collected from six beech trees with different diameters by means of the spiral type SF collection collars installed at diameter at breast height. GR, TF and SF were collected on an event basis using a graduated cylinder during the summer season of 2008. The amount of cumulative GR depth of 19 events was 206.8 mm allocated to TF, SF and CIL, 135.5, 4.2 and 67.1 mm, respectively. At the event scale, the mean values of TF, SF and CIL were accounted 64.7, 1.6 and 33.7% of GR, respectively. Regression analysis suggested a strong positive relationship between CIL and GR. There was also observed a fairly weak negative relationship between CIL/GR and GR. We concluded that CIL contributes a remarkable amount of incident rainfall in the pure oriental beech forest of the study site and therefore should be considered in assessment of water balance.