فصلنامه تحقیقات جنگل و صنوبر ایران
سال بیستم شماره 3 (پیاپی 49، پاییز 1391)

Various poplar varieties have different needs and requirements and different water supply and intervals can change their growth conditions, significantly. Due to limited water resources at most parts of Iran, irrigation interval is more important than irrigation volume in conventional and industrial poplar plantation systems. The aim of the study was to investigate the quantitative and qualitative growth characteristics of different poplar varieties at various irrigation regimes and identify the best irrigation interval. For this reason a trial was conducted in Karaj City of Iran under experimental design of split plots at three replicates. The main plots consisted of three irrigation intervals (4, 8 and 12 days) and the subplots consisted of nine poplar clones. The water supply at each irrigation interval was equal and there were nine seedlings at each subplot at 3 X 3 m. spacing. Irrigation regime for all treatments at first year of trial was similar. The irrigation treatments were supplied at the second year of the trial and an equal water supply was applied to all irrigation treatments, using flume model W.S.C. type3 at each water supply resource and measuring water dimension and time pass of each flume and application of standard curves. The measured poplar growth characteristics consisted of dbh, total height, stem height, crown diameter, stem volume, morphology and phenology. The results showed that there was only significant difference between the both 4 and 8 and the 12 day irrigation intervals in respect to growth parameters. Although there was not significant difference between the 4 and 8 day intervals in respect of growth parameters, but water consumption at the 4 day interval was 7500 m3 more than that of the 8 day interval. All the poplar clones had intensive growth reduction at the 12 day interval irrigation regime and it might be concluded that this irrigation interval is not appropriate for poplar wood production. The poplar clones of P. n. 62/154, P. e. 561/41 and P.e. vernirubensis had the best growth performance at the 4 and 8 day irrigation intervals.

This research was carried out to compare the chemical composition of throughfall (TF), i.e., lead (Pb) and cadmium (Cd) as well as electrical conductivity (EC) and acidity (pH) beneath Pinus eldarica and Cupressus arizonica plantations with open field rainfall in the Chitgar Forest Park. The open field rainfall and TF were collected by 10 and 60 manual cylindrical plastic collectors, respectively. ICP was used in order to measure the concentrations of Pb and Cd. Three rainfall events were measured for chemical analysis. Pb and Cd concentrations as well as EC of TF were significantly different among Pinus eldarica, Cupressus arizonica, and the open field rainfall (P. eldarica: 74.07 ppb, 13.25 ppb, and 298 mµ; C. arizonica: 49.98 ppb, 10.75 ppb, and 251 mµ; open field rainfall: 27.22 ppb, 8.55 ppb, and 90.5 mµ). pH showed a significant difference between Pinus eldarica and the open field rainfall. Concerning the efficiency of plantation canopy for cleaning Pb and Cd concentrations of the atmosphere, changes in the amount of chemical compositions will provide an insight into the multiple criteria of selecting species for plantation projects in polluted urban areas.

It is so important to know about biological and ecological characteristics of trees of a stand, in forest management. The first step to achieve this knowledge is to recognize the spatial pattern of trees. So it is necessary to apply suitable methods to have a reliable and quick estimation of the spatial distribution of trees. This research was aimed to compare the important and mostly applied distance- and density-based indices, utilized to estimate the spatial pattern of trees. For this purpose, a pure wild pistachio stand was full-callipered in Fars Wild Pistachio Research Forest, Iran. The true spatial pattern of the trees was determined by nearest neighbor method. The efficiency of each index was then evaluated by estimating the spatial distribution of the trees, utilizing the indices. The true spatial pattern of the wild pistachio trees in the studied stand was clumped. The results showed that only the two density-based indices of “dispersion” and “heterogeneity factor” could not detect the clumped pattern of wild pistachio trees among the investigated indices. The two distance-based indices of “Eberhardt” and “Hines” could estimate the clumped pattern of the wild pistachio trees among the applied indices as well. In general, the density-based indices performed much better than the distance-based indices in this research and this conclusion should be considered in the future studies on pure wild pistachio stands.

To determine the best absolute harvesting age (quantitative purpose) and maximum production per area of a 18- year-old stands of Paulownia fortunei plantation at Dr. Bahramnia Forest Management project, Three spacing treatments including 3x6, 5x8 and 6x10 m. were examined. Five typic trees with normal diameter class distribution were chosen from each spacing treatment, randomly. The selected trees were fell down and sample discs were made from the stems at 0.4, 1.3 m. and then at 2 m. intervals between 1.3 m. and top height. Diameter and height growth were measured, based on stem analysis method. Stand volume, mean and current annual volume growth at different age stages were calculated, based on calculating fom factor at various age stages. Overall, the absolute harvesting age (forester’s criteria) was determined. The results showed that the absolute harvesting ages at 3x6, 5x8 and 6x10 m. spacing treatments were 11, 11 and 13 years, respectively. In addition, the trees at 5x8 m. spacing treatment had the greatest individual mean annual volume growth, but in respect to trees density per hectar, the trees at 3x6 m. spacing treatment achieved the heighest mean annual wood production per hectar in comparison to the other spacing treatments, which was 525/98 m3/ha. Therefore, it could be concluded that if the aim of Paulownia plantation is quantitative wood production, the spacing of 3x6 m. will be the best, but if the purpose is agroforestry, the spacing of 6x10 m. will be better than the spacing of 5x8 m.

The aim of this research was to study the plant associations in Baharbon district of Kheyroud Forest (north of Iran) and their relationship to physiographical factors. Determination of plant associations and sub associations were done, using Braun - Blanquet School. For this purpose, 51 releves consisting of 100 m2 area, were located at different sites. The phytosociological data was analyzed by the Factorial Correspondences (AFC) and Classification Ascendant Hierarchique (CAH) methods, using the Anaphyto software. Nine associations consisting of Querco macrantherae-Carpinetum orientalis, Fraxino excelsioris-Aceretum velutini, Parrotio persicae-Quercetum castaneifoliae, Parrotio persicae-Carpinetum betuli, Pterocaryo fraxinifoliae-Alnetum subcordatae, Aceri velutini - Fagetum orientalis, Carpino betuli-Fagetum orientalis, Rusco hyrcani-Fagetum orientalis and Fagetum orientalis were distinguished in this forest. Then relationships between the associations and the landform features were investigated, applying the DCA method and CANOCO 4.5 software. The results showed that although there were significant relationships between the associations and the altitude and the geographical aspects; but there was not significant relationship with the slope gradient.

The aim of the study was to identify the quantitative characteristics of wild pistachio forests of Fars province of Iran and their natural regeneration. For this reason, the cluster sampling method was applied which consisted of a 20×20 km network with nine sample plots, each of 2000 m² area with crucified pattern. The results showed that the natural regeneration was weak and the number of seedlings was 5.2/ha, the average crown cover was 171.25 m²/plot and 855 m²/ha or 8.5% of total forests area. The average of plots per cluster was 7.4 and the average of crown cover per cluster was 1256.1 m². Proportion of wild pistachio trees was 7.7%, consisting of 58.3% male individuals. Most of the stands were located in mountainous areas with steep slopes covered with rock materials or shallow soils. Application of rain-fed farming, tree cutting and over grazing were the main causes of forest degradation. Forest protection and reforestation with native shrubs including wild almond species might have positive effects on rehabilitation and improvement of wild pistachio natural regeneration.

Quercus macranthera is a dominant tree species of high elevation parts of north forests of Iran (Caspian region). It is distributed at high elevation area of Semnan and Shahrood cities of Semnan province at two types: 1. Scattered between 1700 and 2000 m. a.s.l. and 2. dense as dominant species between 2000 and 2500 m. a.s.l. and often on north aspects. In onder to study the silvicultural characteristics and site demands of this species, 42 sample plots were laid out on different land forms and geographical aspects, which In 34 plots, soil properties, including texture (clay, sand and loam), organic carbon, lime and acidity were studied. The results showed that pH varied between 5.2 and 8.1 and soil texture was almost sandy clay loam in all land forms, with an exception of clay loam on ridges. soil texture on north and east aspects was sandy clay loam, whereas on south and west aspects was loamy. Organic carbon percentage at three humid aspects (north, east and west) was 1.57, 1.69 and 1.95 %, respectively, whreas at south aspect was 0.48 % and significantly different from the other three aspects (p< 0.05). The maximum and minimum percentage of lime was 20 and 0.9 at south and west aspects, respectively with significant difference (p<0.01). The absolute maximum total height and diameter belonged to oak trees at flat land and north aspect, respectively. The greatest height and volume belonged to oak trees at 2200 to 2500 m. a.s.l. The absolute maximum volume belonged to an indivual oak tree (19.81 m3) on north slope. The maximum regeneration of oak trees was found at east aspect. Most of the forest species had the highest natural regeneration on north slopes.

In order to investigate the effect of environmental factors, including slope gradient, aspect and elevation on regeneration of Juniperus excelsa subsp. polycarpus, some Juniper stands were selected at Hezar Masjed Mountains, north of Khorasan Razavi province, north-east of Iran. Maps of slope gradient, aspect, elevation and landform were used and combined together to develop homogenious polygons of land units. The sampling was made, using stratification method and three sample plots, each 1000 m2. The plots were then laid out on the land units. To study the physico-chemical properties, one soil sample was made from subsoil, at each plot. The soil data were analyzed, using the Principle Component Analysis (PCA). Some parameters, including number of Juniper seedlings and their total height, collar diameter, health and vitality status were measured. The results showed that the elevation has significant effect on number of the seedlings, collar diameter and total height of the seedlings and proportion of health classes. Slope gradient showed significant effect on number of the seedlings per plot. The geographic aspect showed significant relation only with the proportion of moderate healthy seedlings. The impact of land form on Juniper seedlings was not significant. The Principle Component Analysis (PCA) output showed that phosphorus, clay, silt, EC and CaCo3 are the most important factors influencing regeneration of Juniperus excelsa subsp. polycarpus.

The main purpose of the current study was to design less costly forest roads using cost zoning map. For this purpose, the most important effective factors on cost of forest road construction were weighted using the Analytical Hierarchy Process (AHP). Five factors, terrain slope, hydrology, geology formations, soil texture and road slope, were weighted using the AHP. The cost zoning map was developed after weighting the supposed factors and overlay their corresponding map in ESRI Arc GIS 9.3 environment. In Next step, two variants of forest road were planned to connect the start point to the end point, using a 1) Shortest Path (SP) algorithm and 2) a skill expert. The results showed that the length and the cost of the variant planned by SP algorithm were 55% and 65% lower than the path planned by the expert before designing in the field, respectively. The results of the study after designing both planned variants in the field, demonstrated that the length and the cost of the SP-based feasible path were 19% and 21% lower than the expert-based variants, respectively. This means the SP saved 916000000 Rials. The results showed that using the zoning map cost in combination with a shortest path algorithm can lead to a more favorite layout of the forest roads than traditional methods of planning.

Skidding machinery traffic can have a long-term detrimental impact on soil physical properties such as bulk density and strenght. Therefore, the trial was conducted to investigate the recovery status of soil physical properties, compacted during twenty-year period at Asalem Forest, north of Iran. For this purpose, three parcels of the first and the second districts of Nave Asalam Forest, were chosen. The treatments consisted of three periods after skidding (1, 10 and 20 years), two slope classes (>20% and <20%) and two traffic levels (high and low or control). In order to assess soil bulk density and soil strenght a sample plot of 12×5 m. was located at each treatment (totally 12 plots). At each plot, soil strength was measured directly by penetrometer and iitact cores werer sampled to measure bulk density in laboratory. The results showed that longitudinal slope gradient classes and traffic intensity levels were very important factors in soil recovery process in skid trails. Overall, it might be concluded that the most soil disturbances occured on gradient more than 20% and high traffic levels. The result also showed that 20 years after skidding, soil bulk density and soil strenght were under process of recovery, but have significant difference with the control treatment.

Considering the climate change and global warming topics, importance of tree biomass and its measurement is increasing. Direct biomass measurement, especially for root section, is very costly, time consuming and difficult to implement. Usually, in such cases biomass can be estimated, using allometric equation. The aim of this research was to establish equations for estimating carbon content at above and below ground and whole tree biomass for four species, including Mulberry (Morus alba), Black Locust (Robinia pseudoacacia), Eldar Pine (Pinus eldarica) and Arizona cypress (Cupressus arizonica) planted around Mobarakeh Steel complex. For this purpose, 15 trees for each species (totally 60 trees) with appropriate diameter and height distribution, selected randomly and fell down and cut to different segments. Then the different components were separated and total fresh weight was measured at the field. Also roots of 20 trees fully excavated and after fresh weight measurement, some samples for dry weight determination were taken. Dry weight and carbon content of each sample were measured at laboratory. Allometric relationships between independent variables and carbon storage of different components and whole tree were established by nonlinear regression analysis. Overall, 96 models were derived for the four species and only eight of them were not statistically significant. The results showed that for Pine and Cypress, DBH (Diameter at Breast Height) and for Mulberry diameter at 0.3 m established models with highest coefficient of determination at all cases. For Black Locust, there was not special variable which can establish model with high coefficient of determination in all cases. For estimating the whole above- and below ground carbon storage of different organs, tree height had the highest coefficient of determination. Generally, concerning the both above and below ground biomass, modeling allometric relationships resulted in higher coefficient of determination of modeling for coniferous rather than for broadleaved species.

In this study, in order to investigate regeneration success and determine the best gap area, the quantitative characteristics of the regeneration groups were evaluated at different gap area classes. For this purpose, 15 regeneration gaps were selected at three area classes with five replications at each class, including: 50-150 (small), 150-300 (medium) and 300-600 m2 (large). Four square meter plots at two meter intervals were used to measure some quantitative characteristics of the regeneration groups by a simple systematic design on north-south (N-S) and east-west (E-W) transects. The data was analyzed, using the completely randomized statistical design and one way variance analysis and Duncan test methods. The Results showed that the total height and the height growth of the saplings were significantly higher in the large gaps in comparison to the small gaps. In addition, the frequency of seedlings and the density of sapling were the greatest in the medium sized gaps. For this reason seedling frequency of Carpinus betulus and Parrotia persica was found in the medium sized gaps. Overall, it can be concluded that in the selection cutting method, the medium sized gaps (150-300 m2) are the most suitable ones.

Wood resistance of forest species to fire has effective role in preventing forest fire development and expansion. Thus, the aim of this research was to study the tree species wood resistance to fire and to measure the time needed for complete wood burning, considering the wood’s moisture and bark. The trial was conducted under the Completely Randomized Experimental Design with six replicates, 10 forest species (Carpinus betulus, Alnus glutinosa, Parrotia persica, Fagus orientalis, Pterocarya fraxinifolia, Acer cappadocicum, Acer velutinum, Cupresus sempervirence var horizontalis, Quercus castaneifolia and Zelkova carpinifolia), two levels of wood moisture (dry and wet or natural moisture) and two barked and bark free treatments. The woods were burnt at 400°C and the time needed for complete burning was measured by a chronometer. The results showed that the resistance of wet woods to complete burning was 2.3 (Quercus castaenifolia) to 2.9 (Parrotia persica) times more than the dry woods. Carpinus betulus and Parrotia persica had the greatest and the lowest resistance to complete burning, respectively. Moreover, the resistance of Fagus orientalis, Acer cappadocicum, Acer velutinum and Zelkova carpinifolia to complete burning increased, respectively. Bark increased the resistance of some species to complete burning, for instance the time difference for complete burning of wet and dry woods of Fagus orientalis, Cupressus sempervirens var. horizontalis, Acer cappadocicum, Acer velutinum and Zelkova carpinifolia was 46, 82, 110, 116 and 169 seconds, respectively. Although Alnus glutinosa and Pterocarya fraxinifolia had high capacity to establish in sites with poor drainage, but they had a very low resistance to fire. Therefore, it is recommended to plant Fagus orientalis, Acer cappadocicum, Acer velutinum, Parrotia persica and Zelkova carpinifolia as an alive firebreak in areas with high fire risks (naturally and human related reasons), for instance near forest roads and tourism centers, for their capacity to prevent fire development and expansion

Regulation of seed moisture content is one of the important factors in maintaining and increasing seeds durability and quality which is made by different methods. For this reason, the trial was conducted to regulate moisture content and to determine the threshold drought resistance of wild cherry seeds, using the weight method and oven and desiccator. After calculating weight of the seed samples at the specified moisture content levels, the trend of moisture reduction in oven by temperature change and in desiccator by silica gel was investigated. The results showed that there was high correlation between the calculated moisture content by weight method and the actual one. Thus using this method for prospecting the process of desiccation in wild cherry seeds is appropriate. Also during the process of desiccation, the seed's average viability in desiccator was more than that in oven. Due to stability of the wild cherry seed's viability during the process of moisture reduction, particular threshold for drought tolerance was not defined. Therefore, certain critical moisture content for seeds of this species might not be determined.