مجله جنگل ایران
سال چهارم شماره 1 (بهار 1391)

Tree felling is the most important component among tree harvesting which consists of cutting, limbing and bucking. This research was carried out in two compartments in Namkhaneh district of Kheyrud Forest. The Objective of this study were the time study of conventional and directional tree felling operation, estimation of productivity and costs of chainsaw for both conventional and directional methods, and development of regression model. Factors affecting on bucking time regression model were DBH of harvested tree and inter-tree distance for conventional method and DBH of harvested tree and direct of felling regarding to the lay directional felling. The hourly production of conventional tree felling with and without delay time was 46.4 and 65.6 m3/h, respectively. However, in directional felling method, the hourly productions with and without delay time were 44.4 m3/h and 59.1 m3/h, respectively. Productivity of chainsaw felling increased related to tree DBH as power for both conventional and directional felling method. The cost of felling was increased as simple exponential equation when DBH of harvested tree decreased for both conventional and directional felling method. Result indicates that the directional felling was more expensive than conventional felling.

In arid and semi-arid ecosystems, isolated trees have an important effect on soil properties and could determine the structure of the soil fauna communities and herbaceous species under the tree which could influence these types of ecosystems. The aim of this study was to find out the effect of tree canopy on the spatial distribution of soil nutrients (OC, N, P, K, Na and Li) with varied chemical characteristics. In this research, soil samples were taken under and around a pistachio (Pistacia atlantica Desf.var.Kurdica) tree in Sarvabad region, West of Iran. The samples were taken every 2 m and then at 50 cm intervals in a regular grid of 20 m × 20 m around the tree for analyzing the spatial properties using geostatistical techniques. Total nitrogen (N) content similarly to soil organic carbon (OC) was higher under the tree. Phosphorus (P) content also was higher under the tree canopy. Potassium (K) decreased with distance from the tree base. Sodium (Na) had a medium spatial distribution related to tree canopy, while Lithium (Li) showed a sparse spatial pattern and its distribution seems to be independent of the tree position. These results support the hypothesis that the presence of a tree affects differently the spatial distribution of the various nutrients depending on their chemical characteristics.

In order to study the tree growth and natural regeneration of loblolly pine in a 33-year-old plantation in Pylambra region (Guilan province), 1.5 ha of well stocked stand was selected. This study was done as randomized complete block design with three treatments as: T1, low density (15m2 basal area ha-1), T2, medium density (20m2 basal area ha-1) and T3, high density (25m2 basal area ha-1) with four replicates. Soil surface scarification was carried out at the first year. Diameter at breast height, total height of trees in each plot (1000m2), number and height of pine regenerations in subplot with an area about 10 m2 were measured. Results show that the height of Loblolly pine seedlings ranging from 10 to 150 cm were recorded in different treatments but in terms of the height growth, medium density treatment with 182 stem per ha showed better results and the difference with other treatments was statistically significant.

For some reasons, increasing poplar spacing in traditional poplar farming is not accepted by farmers. Scientific investigations has shown that for increasing wood quality, selection of optimum spacing, appropriate harvesting time, and cultivation of agricultural crops between tree rows, specially at early years would increase productivity and poplar cultivation area. Therefore, in this study populus nigra betulifolia seedlings were planted as randomized complete block design with three replicates and four mixed poplar and alfalfa treatments with tree spacing including 3X4, 3X6.66, 3X8, and 3X10 m also 2 control treatments namely sole (pure) alfalfa and pure trees (3X4m). Plot size was 1200 square meters. We investigated some important attributes during the years 1998-2008. Irrigation operation was done during the growing seasons. Ten distinctive growth attributes in conjunction with poplar and alfalfa were recorded on the treatments at different stages and suitable times during the study period. The data were analyzed using univariate and multivariate statistical methods. The study is aimed at evaluating the performance of poplar production intercrops with alfalfa. Results showed that the most amount of tree height growth belonged to mixed treatments including 3X4, 3X8 and 3X6.66 m with 159, 158 and 142 cm, respectively. Regarding the wood volume growth per hectare, the most amounts belonged to the same treatments with 18.4, 11.1 and 10.99 cubic meters, respectively. Also the most amount of dry weight production of alfalfa belonged to sole alfalfa, 3X10 and 3X8 m treatments with 7507, 4788 and 4265 kg per hectare, respectively. All of attribute amounts showing differences among treatments were significantly different at 5% level of probability. There was no significant difference among the spacing after 11 intercropping years for branch diameter and annual tree growth diameter. Meanwhile, for some attributes there were significant differences among years and interaction between treatments and years. As a final result, the suitable planting spacing of tree in Poplar/alfalfa intercropping system is 3X6.6 m according to the site conditions.

In order to determine the suitable conditions of temperature and effect of desiccation on seed viability during storage, seeds were collected from Aliabad Katool site in Golestan forests. After determining the primary characteristics, Preservation of Prunus avium seed samples has been conducted under two varied temperature conditions (4 and 25°C) and two moisture contents (11.5 and 5 percent) in tightly closed containers. After storage, the moisture content and viability of seeds was tested by staining with 0.1 percent solution of Tetrazolium in every three month periods. The results showed that desiccation had no significant effect on seed viability after 3 months of preservation at 4°C. But at 25°C desiccation had significant effect on seeds viability and at this temperature, viability of seeds stored with 11.5 percent moisture content was decreased. In total, following one-year storage, either seeds which their moisture content were reduced and the control seeds (with primary moisture content), under 4° C status indicated near 90 percent viability. From the results of this investigation it can be deduced that the better storage conditions for low-moisture content seeds of Prunus avium (< 11.5%) is maintainance at refrigerator with temperature of 4° C.

Biomass estimation of forest trees is one of the most important factors in forest management. The main objective of this study was to establish allometric equation for estimating crown, trunk and total tree dry weight. Sampling of tree parts was done using transect with 4 Km length and 15 meter width in Khojir National Park located at east of Tehran and 30 trees were felled down randomly with different diameter at breast height classes. Diameter at breast height, crown diameter and trees height were measured and dry weight of different parts of trees were determined. Allometric power and exponential regression models were derived. The equations were compared with each other based on the different modeling parameters. The highest significant correlation was found between crown diameters and dry weight (R2=0.93). The best equations were obtained by means of a power regression model.

This reserach was conducted to investigate the Scotch pine (Pinus sylvestris L.) adaptation in midland areas of Ladjim forests (Sari-Iran). The study was carried out as randomized completely block design with four treatments (based on different provenances of Pinus sylvestris) and three replicates during 1990 to 2005. Four provenances of Pinus sylvestris L. were collected fromUkraine,Turkey, Spine andFrance. In each plot 100-two year old seedling were planted in 2m×2m spacing. After 15 years, the results showed that the Turkish and Spanish Provenance had the lighest and lowest survial in the study area, 81.68% and 60.33%, respectively. Analysis of quantitative data indicated that the Ukrainian provenance (mean DBH and total height equal to 12.43 cm and l7.72 m, respectively) had the best growth. Also the results of plantation quality based on health, vitality, crown and trunk quality showed that the Ukrainian provenance with 78% alive trees is in excellent and good quality and had the best ranking among the other provenances in Ladjim forests. Ukrainian and French Provenances are recommended for plantation of destructed areas having similar ecological conditions in North of Iran where planting the native deciduous species plantation is not possible.

Natural processes and human activities continually change forest landscapes. Regeneration patches are one of the factors changing the forest landscapes. Knowledge of spatial patterns and structural analysis of patches are essential in sustainable forest management. For this purpose, the current study was done in Gorazbon district, kheyrud Forests. All regeneration patches were located in the study area and landscape analysis in combination with the environmental gradient analysis was applied using Fragstats software. The results of this study showed that the distribution patterns of patches in different compartments are randomly clumped. Highest and lowest patch percentage was observed in compartment 315 and 321, respectively. This study showed that the largest patch size was 0.9001 hectare in compartment 310 and the minimum and maximum distances between patches varied from 40 to 139.5 m. Compartments 307, 308, 311, 318, 319, 322, 325 and 326 had the highest diversity indices and suitable spatial pattern of patches. This result confirms the fact that the in management of natural stands, distribution patterns of patches in stands level is to be regular, but among the stands and different compartments they can follow random pattern. Because of with achieving such a model, appropriate spatial structure can be created in the stands.