جستجوی مقالات مرتبط با کلیدواژه « aspect » در نشریات گروه « جنگلداری »

Leaf area index (LAI) is one of the most important structural characteristics of forest ecosystems, which has a great impact on changes in energy, weather, atmospheric and gas functional models. This index provides managers and planners with a lot of information related to the amount of photosynthesis, evaporation and transpiration and fertility of different habitats. Physiographic factors also (elevation above sea level, aspect and slope) play an important role in the global LAI. In this research, the changes of the LAI in different classes of elevation, aspect and slope are compared and evaluated.

n this study, 230 square-shaped sample plots with an area of 1000 square meters were used to collect the ground information of the leaf surface index using a systematic sampling method with a sampling grid of 100 x 100 meters in five sites (Kordkoy, Shast Kalateh, Zarrin Gol, Sokhdari and Loveh). In the center of each plot, a leaf harvesting trap with dimensions of 60 x 60 cm was used to measure the LAI. First, height maps from elevation, aspect and slope were also prepared and their values were extracted. Then the LAI was compared and analyzed in different classes of elevation, aspect and slope using Duncan's and independent t tests.

The results of LAI showed that the elevation of LAI in Kordkoy vegetation was measured with 8.91 and the lowest level of LAI was measured with 5.10 in Zarrin Gol vegetation. The results of analysis of variance showed that there is a significant difference between the LAI in different classes of elevation above sea level in the entire study area. And with the increase in elevation above sea level to about 1300 meters, the LAI increases and after that, the LAI has little changes. The significant results of Duncan's test and independent t-test showed that there is no significant difference between the LAI of each site in different classes of elevation above sea level, aspect and slope, except for Kurdkoy site.

In general, in this study, the elevation compared to the slope and aspect was raised as a very important factor for investigating LAI. Investigating the effect of physiographic factors such as elevation above sea level, slope and aspect on the LAI and monitoring its changes in order to know the formulation of appropriate policies to reduce the effects of climate change and global warming and in sustainable management is of great importance.

One of the environmental problems of the Zagros forests, is the occurrence of oak decline phenomenon in Zagros Forest. The intensity of oak decline in the North Zagros is slower than in the Middle and South Zagros. The purpose of this study was to investigate the trends of oak decline in forests of Baneh city from 2019 to 2020.Four sites including Belveh and Gandman (southern aspect) and Saraki and Mirhesam (northern aspect) were selected and 100 trees were evaluated in each site. Oak decline status was recorded during two years of research in five classes: healthy trees, dieback in crwon, dieback up to 50%, dieback more than 50% and standing dead tree. Wilcoxon and Friedman (non-parametric tests) were used to compare the decline codes at each site for two consecutive years and to compare the decline codes at four sites per year (separately). The results showed that the greatest change of oak decline class was in Saraki site (with 0.27 change). At all four sites, the trees were shifting to oak decline classes in the second year of the research, and the change in oak decline classes at each site for two consecutive years (Wilcoxon test) was statistically significant. Besides, the change of dieback trees (dieback and dieback up to 50%) from 24% of trees in 2019 to 44% of trees in 2020 had changed. Most oak decline was observed on the southern aspect. Overall, it is suggested that human intervention be controlled.

The present study was conducted to determine the morphological indices indicating the diversity of Persian oak acorn in two forest sites on the northern and southern slopes of Ilam forests. In each site, 12 oak trees were selected and from each tree, 100 acorns were collected from the four main crown sides as a composite sample. Samples were transferred to the laboratory to measure the morphological traits of the fruit and its cup. The values of fruit length, fruit diameter, cup length and cup diameter were different among trees in each site. Also, the values of fruit length and fruit diameter were higher in the northern site than the southern site. Plasticity study showed that fruit length and fruit diameter traits have less plasticity. Moreover, the values of fruit length, fruit diameter, cup length and cup diameter were significantly different among tree groups with different degrees of crown dieback. Therefore, it was found that the acorns of Persian oak trees are significantly affected by the individual characteristics of trees, site conditions and the severity of crown dieback. Although variability among trees in terms of site differences and the degree of crown dieback can be due to plasticity, but individual and intra- population changes in fruit traits can be due to their genetic and in this regard, fruit length and fruit diameter traits are morphological indicators indicating the diversity of Persian oak acorn.
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Oak trees are hosts of diverse gall-inducing parasites, but the information about the leaf gall is poorly understood. This study aims to examine the weight of leaf galls on oak trees (Quercus brantii Lindl.) in different crown directions with different growth forms (high-forest and coppice) on different geographical slopes in healthy and dry stands of Kohgiluyeh and Boyer-Ahmad province, Iran. For this purpose, two sample plots with a one-ha area involving decline traces of trees (dry) and two sample plots without dieback (control) on the northern and southern slopes in forest sites of Boyer-Ahmad and Dena counties of Iran were selected by field survey. After recording the quantitative variables (DBH, mean diameter of sprout-clump, height and canopy cover), we collected 20 leaves from each direction of the crown of each tree sampled. In the laboratory, the galls were removed from the leaves and weighed. The results showed that there was no statistical significance between the different crown directions of the sample trees in both growth forms, although, in most sites, the northern direction of the trees had more galls. Leaf samples from the south decline site were found to have significantly more gall weight than samples from the other sites in both growth forms. Also, high-forest trees had significantly more leaf galls on their leaves than the coppice trees did. Monthly average temperature and altitude seem to be two determining factors in leaf gall development of the oak trees.

Windthrow of trees is a common ecological phenomenon in the forests of Hyrcanian region. The forest stands of 22 in series of 12 of Haraz Forest plan is one of the stands with high percent of wind-thrown trees. The purpose of this study is to investigate the role of physico-chemical properties of soil, topographic factors, characteristics (slope and direction) of Parcel 22 and compare it with adjacent areas in order to find environmental variables effective in increasing Windthrow rate.

In the study area, completely randomly, 15 sample plots (10 Are) were measured in the center of the Windthrow trees. For the investigation of this problem, in an area of 88 hectares, about 400 wind-thrown trees were 100% surveyed and their quantitative and qualitative characteristics were recorded. Furthermore, the characteristics of windthrown trees in different physiographic conditions (i.e., different slopes and aspects) and soil characteristics (i.e., bulk density, texture, EC, carbon: nitrogen ratio and soil total nitrogen) of this stand and near stand (without wind-throw) were investigated.

According to results, most of the damage belong to trees that was uprooted trees and wind throw trees in flat lands were more than steep lands. Most precent of wind throw trees were in slope 0 and 5 % and 67% uprooted trees were in this section. The most uprooted trees were belonging to Parrotia persica (44%) while, the lowest uprooted trees were recorded for Acer velutinum and Alnus saubcordata species (<5%). The results of independent t-test showed that soil moisture content in the soil of windthrow trees was significantly (95 %) higher than the control area. Also, Carex acutiformi species includes 4.47% of herbaceous species in the wind throw area, while it was not seen in the control area.

Finally, the results of this study showed that the construction of dams upstream has changed the soil moisture content and increased the sensitivity of species such as Parrotia persica to wind. Meanwhile, the resistance of forest species in the face of stable soil moisture changes and the occurrence of strong winds has been different, so that moisture-loving species such as Acer velutinum and Alnus saubcordata (due to moisture-friendly and insensitive to increase soil moisture) with lower rainfall intensity Showed.

This research aimed at studying the seedling emergence and survival rate of Pistacia atlantica, Acer monspessulanum and Amygdalus orientalis by direct seeding in Dalab forests of Ilam with two aspects and five seeding positions (nurse type). For this purpose, six sites were selected in the north- and south-facing slopes with the same altitude. In each site, one transect was established perpendicular to the slope, and the seeding positions including “tree”, “shrub”, ‘bush”, “rock” and bare spaces, by observing three replicates were determined. At each seeding position, 12 holes were dug and the seeds of the mentioned species were planted. The number of seedlings during the spring and summer of 2018 and 2019 years was counted. According to the results, the number of seedling of P. atlantica decreased in the second year compared to the first year and in summer compared to spring. The highest percentage of holes with seedlings of P. atlantica was found in northern aspect and under tree crown and next to the rock. The highest percentage of holes with A. monspessulanum seedlings was under tree crowns and shrubs. A. orientalis did not react to any of the examined factors. The most and least share of the seedling emergence were belonged to P. atlantica and A. monspessulanum, repectively. It was concluded that the rate of seedling emergence changes under the effects of aspects and seeding positions, so to increase the emergence rate of seedlings, it is better to sow in the field in more suitable seeding position in any aspect.

This study was carried out to study the habitat characteristics of Persian juniper trees due to the topographical factors and site exposure in Spiro forest habitat, located at Damghan County. Inventory done by systematic method (Net dimensions: 300×400m). Trees number and diameter at breast height in 10 R area sample plots were taken. Then, the topographic factors effects on some of the growth variables of Persian juniper stands such as basal area and number per hectare were evaluated using stepwise regression model. The results showed that three indices of aspect, site exposure and topographic wetness had a positive and significant correlation with the number of hectares of trees. Also, elevation from the sea level, site exposure and roughness had a positive and significant correlation with trees basal area variable per hectare. According to the results, the most correlation between cypress quantitative characteristics, including number per hectare and its basal area, was obtained by topographic factor of site exposure.

Recognition of humidity changes is important because of its relevance to hydrological, ecological and physiographic characteristics of the area. Therefore, soil moisture content in four main directions and three depths of 50, 70 and 110 cm of soil for two years from March 2013 to September 2012 in the forest area of Meleh-Siah Ilam was measured and analyzed in a randomized complete block design with soft SAS was implemented. The results showed that soil moisture and soil depth and direction were affected by moisture storage in the south and north directions with 21.9 and 19.7 and in the eastern and western slopes 19 and 15.5 mm. Also, the average monthly moisture content in the three depths of 70, 110 and 50 was 18.4, 17.4 and 7.5 mm respectively. The average monthly soil moisture storage at three depths 50, 70 and 110 are 18.4, 17.4 and 7.5 mm, respectively. In other words, the effect of soil depth and geographic orientation on the soil moisture is effective but not noticeable in dry years and in dry months. Also, the results showed that the monthly dryness rate (from wet to dry period) in the wet year is more than dry year and increases with increasing depth of soil. Based on soil texture analysis, the optimum moisture content for plant growth was between 15% and 30%, and based on this, the maximum drought stress on vegetation and especially oak species was in August and September, which coincided with the peak of vegetative growth And the reproductive stage of the oak tree species.

The purpose of the study was to investigate the effects of some physiographic factors on competition index (CI) and fine root biomass (FRB) in coppice Persian oak trees (Quercus brantii Var. Persica), and also to determine the correlation between these factors and some characteristics of oak trees in forest of Ghalegol-Lorestan. Randomized blocks sampling method was used to determine the target trees in the site by circular sample plots (n=40). In addition to measuring the DBH of trees and their distance from neighbor trees for determining CI, fine root sampling was done at depth of 0-30 cm and at distance 1m, also in north and south sides of the target trees. The independent t-test showed that the aspect had a significant effect on CI, so that it was more in north-facing than the southern directions (p<0.001). Analysis of variance indicated that slope and altitude influenced the CI of oak trees and also the highest CI was observed at altitude of 2000-1900 m a.s.l (p<0.05). There was a significant correlation between CI and crown diameter of trees (p<0.01). The Pearson correlation revealed that there was no significant correlation between FRB and CI among trees (p>0.05). The independent t-test showed that aspect had a significant effect on FRB (p<0.001). Analysis of variance indicated that slope had no effect on FRB (p<0.05), but elevation showed a significant difference in this regard (p<0.01). Considering the effect of topographic factors on the CI and FRB of Persian oak trees, it can be stated that in silvicultural operations, more attention should be paid to the topography of site and the trees characteristics.

The purpose of this research was to investigate the role of hillshade values, in comparison with terrain aspect, in the canopy changes and evaluation of ecological capability in vegetation domain of Zagros forests. In conducting the research, digital elevation model (DEM) was prepared and soil map was extracted from that. Due to the direct relationship of forest canopy with the site ecological capability, the raster map of hillshade was multiplied by forest canopy; and canopy area was calculated at different values of the hillshade map. Also, the map of the main slop aspects extracted by the DEM map and that was multiplied to the map of forest canopy. Then canopy area was calculated for different aspect; and that was presented as a histogram. Thereupon, the histogram and quadratic model equation of relationship between forest canopy percent and hillshade regime was prepared, in the entire study area. The histogram and the model, show that reducing the intensity of sunlight (Rising Shadow), strong influence on the increase in canopy. Also, the quadratic regression model (R2 = 0.58) and linear regression model (R2 = 0.56) of the correlation, with 17 repetitions, obtained in the form of a square block network. Because of the easiness and the low cost of hillshade mapping, and also, its superiority over the terrain aspect map; we recommend that hillshade maps be used as one of the key factors for of land ecological capability, in the Zagros forest and other arid and semi-arid forests.

This study was carried out to explore the relationship between environmental factors and presence of three important oak species (Q. brantii, Q. libani, Q. infectoria) in northern Zagros forests.Following the site selection, vertical distributions were determined based on the minimum and maximum ranges species presence. A number of 54 circular sample plots, each 500 m2 were established based on various landforms and aspect. Following this, habitat characteristics including altitude, land form, slop direction, slope% and forest type were recorded. Finally a soil profile was prepared for routine physio-chemical soil analysis. The data was analyzed by means of exploratory method, analysis of variance, canonical correspondence analysis and descriptive statistics. Results revealed limitations of Q. libani concerning altitude range and aspect. The species occurs on acidic soils with low level of EC and CaCo3 and favors from heavy and semi-heavy soils. Furthermore, Q. brantii occurs on heavy halomorphic to alkaline soils with high level of CaCo3 and covers the maximum range of altitude in all aspects. It seems that soil acidity is not a limitation factor for Q. infectoria which favors from light soils and steeper northern slops.

During the last decade, oak decline has caused critical health issues within the Zagros forests in west Iran, which is currently approaching a threatening level with effects on stand structure and stability. Identifying the influential factors on the spread of this phenomenon can thus help forest planners and administrating units to control the crisis. This study aimed to assess different aspects influencing deterioration of oak trees with respect to stands environmental characteristics in the southern part of Zagros forests. For this purpose, 12 declined stand dominated by Brant`s oak (Quercus brantii) at different conditions in both the North and South aspects as well as two altitudes and three replications were chosen within Meleh-Siah forest site in Ilam province. A transect line was randomly assigned to each of the stands, along each or which three square plots (2500 square meter) were laid. Within the plots, all individual trees were inventoried. By using a randomized complete block and factorial design, methods were used to compare the mean values of the inventoried parameters. Although the results showed no significant difference between diameter, height, crown length and basal area of the stands along gradients of aspect and altitude, significant effect of aspect on decline rate in seed based trees as well as altitude on coppice trees were observed. The degree of decline in south aspect was greater than in north aspect. In addition, lower elevations showed larger effects than higher elevations. The interaction between two factors was also significant on the decline rate.

Continues occurrence of fire in northern forests of Iran during past years, necessitates conducting research, in order to predict future fire occurrence in these forests. For this reason a 1:25000 topographical map of Zarrin Abad Forests of Neka Township of Mazandaran province of I.R. Iran. was geo-referenced in GIS, firstly. Then digital model of elevation (DEM) with 30-meter pixel size was obtained from the geo-referenced map and slope, aspect and elevation maps were developed from the DEM. The vegetation cover density and residential areas (villages) maps were obtained from Nekachoob Corporation Company and digitized in GIS. All roads in the study area were routed using GPS and their map was developed. Then 200 and 500 meter buffers were considered on the maps, around the roads and the villages. All of the digital layers were classified according to Dong model. The fire potential map with five classes was developed by overlaying all of the maps, in GIS environment and allocating weight to each factor (map), regarding the Dong model. The past forest fires map was developed, using actual forest data and applying ground sampling with GPS. Then this map was overlaid on the forest fire potential map. Results showed that about 40 percent of the past forest fire areas are located on sites with very high or high fire risk which indicates the medium validity of the used model. Thus, Dong model was modified and weight of the layers was changed, based on their importance at the studied area and finally a new model was developed. A new fire potential map was generated, based on the modified model and was overlaid on the past forest fires map. Results showed that about 80 percent of the past forest fire areas are located on sites with very high or high fire risk which indicates a high validity of the used model for the studied area. It seems that the model might be applied for other forest sites at Caspian region of Iran, based on spatial locations of their watershed basins.

To investigate the physiographic factors and related soil physico - chemical and biological characteristics, 268.7 ha of Noushahr khanikan forests were studied on May 2012. 60 soil samples were taken from 0 - 10, 10 - 20 and 20 - 30 cm depths with systematically random method. The physiographic factors including slope, aspect and altitude recorded in soil sampling location. Soil acidity, bulk density, saturation moisture, organic carbon, total nitrogen, soil texture and biomass of earthworms were measured in the laboratory. The earthworms were collected simultaneously with the soil sampling by hand sorting and classified to epigeic, anecic and endogeic ecological groups. Site slope were divided to four classes (0 - 20, 20 - 40, 40 - 60 and 60 - 80%) and altitude divided to three classes (100 -150, 150 - 200 and 200 - 260m). Analysis of variance is indicating acidity, bulk density, saturation moisture and soil texture had significant differences among aspects and slope classes. Nitrogen and carbon to nitrogen ratio values showed significant differences among aspect and slope classes, respectively. Altitude classes showed no difference in viewpoint of physico - chemical properties. Epigeics number and biomass had significant statistical differences among aspect and slope classes. Epigeics found in soil superficial layer (0 - 10 cm). The most activity of anecic and endogeic groups was visible in more beneath depths (10 - 20 and 20 - 30 cm).

In order to identify the diversity of tree species in relation to physiographic factors (elevation، aspect and slope)، the Kandelat Forest Park with an area of 614. 85 hectare was surveyed، where is located southeast of Rasht city. For this reason، maps of slope، aspect، elevation and dominant vegetation types were provided، using GIS technology. As a result، 18 homogeneous units were obtained by layering the mentioned maps. In each homogeneous unit، five sample plots، and totally 90 plots were randomly located. The trees at each plot were found and their diameter at breast height (dbh) was measured. Overall، 17 tree species belonging to 16 genera and 12 families were identified. Result revealed that aspect had significant effect on diversity and evenness of the tree species. Species diversity and evenness on south aspect were significantly more than the other aspects. In addition، elevation had significant effect on diversity and species diversity and richness were greater at high elevations. There was not significant effect of slope aspect on tree''s species diversity، richness and evenness.

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.

Wild pistachio species, Pistacia atlantica and P. khinjuk, are xerophyte species in Irano-Toranian region, which are scattered in an area about 3200000 ha in four main open forest types of Fars province including: 1) Acer monpessulanum-Pistacia atlantica, 2) Amygdales spp.-Pistacia spp., 3) Pistacia spp. and 4) Quercus brantii-Pistacia atlantica. Regarding the distribution area, elevation, slope and aspect characteristics of wild pistachio, different maps were produced in 1:250000 scale using GIS. The distribution map of wild pistachio was integrated with the other mentioned maps. Analyze of variance and F- test showed that, 57% of habitats of wild pistachio species are mostly distributed between 1000 and 2000 m.a.s.l, 25.5% between 15% and 30% slope gradient and 66% of habitats in southern and northern aspects.

Phenological characteristics of Pistacia atlantica Desf subsp. Mutica (F. & M.) Rech were investigated at two different sites of Khalkhal Forests (Mazrae and Kandiragh) at two altitudes (1450 and 1650 m.a.s.l) and one aspect (south), during the years of 2001 to 2003. For this study, 30 trees at each site were selected and registered. The study started at March (beginning of the growing season) and ended at full leaf fall of each year. Every 7-10 days, the phenological characteristics were measured as date of budding, date of leaf formation, flowering, fruiting, fruit ripening and leaf fall. Statistical analaysis was done by compound analysis of variance method. Results showed that date of budding is between 3rd and 4th week of April, flowering between 4th week of April and 1st week of May, fruit set between 2nd and 3rd week of May, fruit ripening between 4th week of October and 1st week of November and leaf fall between 1st and 2nd week of December. The statistical analysis showed that there were significant differences beween the phenological characteristics and two altitudes. There was significant negative correlations between average rainfall and date of budding and flowering.

In order to study the effective factors influencing distribution of wild pistachio species in Zanjan province, the first step was to inquire and review all the related documents and information. The next step was to make excursion in the natural habitat of the species located in the study area. Finally, the distribution of the species was overlayed on topographic maps. The total area of this species estimated to be 23208 ha. Considering the main factors including: elevation, aspect and geological formation; working units were specified and 40x40 m sampling plots were located on the units to determine different forest types. Three forest types were distinguished, including: pistachio-juniperus (5002 ha), pure pistachia (3401 ha) and degradaded open pistachio (14805 ha). The last one was the vastest forest type which demonstrates the degradaded extent of this forest type. Most of trees at the forest types were coppice and only few seed originated seedlings were found. The highest distribution (44%) was found on 45 percent and higher slops. About 65 percent of the forests located on northwest and southwest aspects. The lowest distribution was found on the main aspects (north, south, west and east). Approximatly, the most distribution was found in cold semi-arid climate (61.74%) and the lowest distribution (0.16%) was seen in the cold-humid climate. Most of the forests were located on volcanic, shaill and sandstone geological formations (45.94%).