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

The aim of present study is investigating the effect of physiographic factors on leaf area index (LAI), leaf mass per area (LMA) and canopy water content (CWC). 125 square plots with dimensions of 30 meters by 30 meters in cluster method model were sampled. Plot elevation was determined by using digital elevation model (DEM) map. Also 9 aspects were determined by using a compass device. Photographing the canopy and collecting leaves from the canopy were done to estimate the indices. The results showed that the elevation has a significant effect on all indices. The aspect has a significant effect on LAI and LMI indices. LAI and CWC indices decrease from low to high elevations and increase on the highest elevation. The LMA attribute also increases from low to high elevations and decreases in the highest elevation class again. The high LAI value observed in the north and northeast aspect and the lowest LAI observed in the south and southwest aspects. The CWC is higher in northern aspects and it is lower in the southern aspect. LMA is lower in the northern and northeastern aspects while it was higher in the western and south western aspects. Knowing the conditions of vegetation indicators status in different aspects and elevations, provides the possibility of prioritizing support and maintenance measures in different topographical conditions of the region.

Wildfires are one of the most important challenges of natural resources management causing a lot of damages to these natural ecosystems, annually. Although, reportedly almost all of the wildfires are human caused in the Zagros region, environmental factors play a key role in fire spreading and burned area.  Hence, the aim of this study was to determine the relationship between burned area and physiographic factors (slope, aspect and elevation) from 2001 to 2018 using Moderate Resolution Imaging Spectro-radiometer (MODIS) fire data.

MODIS burned area data were collected for the statistical period of 2001-2018 with the resolution of 500m include spatial and temporal information of fire incidents. Then the physiographic maps including slope (five classes), aspect (five classes) and elevation (six classes) maps of study area were prepared, using a 90m DEM. Kolmogorov–Smirnov test was used to check the normal distribution of the data. Since the data did not follow the normal distribution, non-parametric tests such as Kruskal–Wallis and Mann–Whitney U tests were used for comparing the statistical differences between the median of burned area in different classes of physiographic factors. Furthermore, the specific burned area (SBA) index were calculated by overlaying the layers of burned area, vegetation type (rangeland and forest) and physiographic factors to remove the effect of the surface area of physiographic classes.

The results showed that the larger burned area was observed in the larger physiographic classes. In other words, the surface area of physiographic classes is the most effective factor on burned area. However, the values of specific burned area (SBA) in each classes showed a different result. In both vegetation types, the value of specific burned area index was highest in the elevation class of 500-1000m and the eastern aspect. Furthermore, the value of SBA was highest in slope class of 15-30% and more than 80% in rangelands and forests, respectively. Since the value of SBA index is not dependent to the extent of relevant physiographic classes, it could be used to indicate the natural potential of each physiographic classes for fire spreading in different regions.

It was concluded that the specific burned area in comparison with burned area is a more appropriate index for investigating the effects of physiographic factors on fire spreading.

The forest structure and stand composition are controlled by several physiographic factors, because these factors play an important role in control the physical and chemical conditions of the environment, including access to light, soil moisture, and nutrients. In this study, the physiographic characteristics indices of the study area including landform index, terrain shape index and aspect slope index and the stand structural characteristics including density, basal area, canopy coverage, and the species important value index using the Detrended Correspondence Analysis and Redundancy Analysis studied in Arasbaran forests. The results showed that the highest altitude range (1600 to 1850 m a.s.l) had the highest amount of physiographic indices value. The Redundancy Analysis showed that the LI index had a positive correlation with the first axis and TSI and AS indices had a negative relationship with it. In addition, Caucasian oak was the most important species in terms of importance value index. Detrended Correspondence Analysis between species and sampling units showed that Caucasian oak had the smallest distance with sample units and followed by hornbeam. Correlation analysis of structural characteristics and physiographic factors showed that stand density had no significant relation with physiographic factors (p≤0.05), but the correlation of the canopy coverage area with the direction of slop in the first and second altitude ranges and basal area with the landform shape in the third altitude was significant (p≤0.05). This study showed that the trees structural distribution in the study area affected by the physiographic properties. Therefore, it suggested that the effect of other environmental factors to be investigated such as soil and climate on the forest structure.

In this study, with respect to the importance of fires in Zagros vegetation zone, temporal and spatial data of fire incidence, from 2002 to 2018, in natural areas of Kermanshah province was extracted using MODIS active fire data. Then the frequency of fire incidence was analyzed with respect to physiography of the study area including slope, aspect direction and altitude classes. According to the results, the highest and the lowest frequency of forest fire incidence were observed in slopes of 15-30% and > 80%, respectively. In rangelands, the highest and lowest frequency was observed in slopes of 0-15% and > 80%, respectively. In the forest area, the highest frequency of fire incidence was observed in the altitudes of 1500 – 1000 m and 1500 - 2000 m and the lowest frequency was observed in the altitudes of 500 – 115 m and >2500 m. In the rangelands, the highest frequency of fire incidence was observed in the altitudes of 1500 – 1000 m and 1500 - 2000 m and the lowest frequency was observed in the altitude of over 2500 m. It was also observed that the frequency of fire incidence in the northern and southern aspect directions was remarkably higher than the eastern and western directions. The results of this study emphasize that in addition to the type of physiography of the region, the frequency of fire incidents is significantly dependent on the surface area of each form of physiography, which can be very important in fire management planning.

Knowledge of the decay trend of dead trees and site factors affecting their functions, plays an important role in the development of conservation management plans in forestry projects. This research was conducted in Asalem beech forests in northern Iran to assess the impact of physiographic features of the site on the process of dead trees decay. A total of 90 sample cuts of dead beech stumps were randomly selected and studied. For each sample, species, diameter and decay classes were recorded. The effect of aspect Slope Index (ASI), Terrain Shape Index (TSI) and Landform Index (LI) on the physical properties of dead wood (density, weight, moisture content) and biochemical components of wood (lignin, cellulose and hemicellulose) on the process of decay were investigated. The mean decay rate of dead beech stumps calculated 0.061 and the mean of beech was 0.32 that varied between 0.05 and 0.62 grams per cubic meters. The results revealed decay process requires about 46 years and the four classes decay showed significant difference in terms of wood density, lignin and cellulose. Meanwhile, the LI was the most important physiographic factors influencing the decay rate of dead trees. The lignin content of the deadwoods was significantly influenced by the form of land. Accordingly, it can be concluded that maintenance certain volume of dead tree in the forest stand structure need to taking account into the dynamics of dead trees, as well as the effects of geomorphological characteristics of site, especially land form conditions

Understanding of biodiversity status can be applied as a guide to better ecosystem management. The ecosystem ecological sustainability is ensured by high species diversity and better conservation. Therefore, the purpose of this research is to identify the species diversity of trees and shrubs in the Guijeh-bel region of Ahar and to determine species diversity using related indicators, as well as the relationship between biodiversity and physiographic factors. Sampling was done in 48 circular sample plots, each 314m2, by a random-systematic method within a 150×200m network. In each sample plot, a list of all of tree and shrub species with abundant-overcome values was recorded based on the Brown Blanche scale. The results showed that there were 13 woody species. Smilax excelsa L. and Rhamnus sp. had the highest (39%) and the lowest (0.04%) presence in the sample plots, respectively. The number of stems varied from 10 to 110 stems of different species in the sample plots. Two index species of Arasbaran region, Acer campestre L. and Viburnum lantana L., were observed in this area. Viburnum lantana and Acer campestre were often found on the western and the eastern aspects, respectively. The main effects of slope on the Taxa, Simpson, Shannon-Weiner and Margaleff indicators were not significant. The main effect of aspect was significant on the taxa index at 1% level and on other indicators at 5% level. The average of all indicators of diversity in the western aspect was higher than those of other aspects. The results of clustering of vegetation composition confirmed the results of the comparison of the site diversity indices. According to the results of the coefficient of variation, the taxa and Margalaf indices had the highest coefficient of variation. Therefore, in other studies, as well as assessment of the effects of management and monitoring of vegetation changes, it is recommended to use the indicators. Based on the results of this study, the high values of slope steepness and biodiversity, provides the protection of the area.

This study aimed to determine the efficiency of numerical and parametrical indices to evaluate biodiversity of soil and litter mesofauna in different physiographic positions. Sampling was conducted in three height classes above sea level (low land, middele land and high land) and two aspects (north and south). Also, in each altitude class, three different slope classes (less than 25%, 50-25% and more than 50%) were determined. Three transects of about 100 m were established in each of the slope classes. Three sample points were located along each transect. Around the center of each sample point, a litter layer and a soil sample to a depth of 10 cm speratly were taken. In the laboratory, soil and litter samples were placed inside a Berlese funnel to bring out arthropods mesofauna. The results showed that soil mesufauna Shannon–Wiener's diversity, Pielou's evenness and Margalef's richness indices, were significantly affected by aspect, elevation, sampling depth and their interactions. Along the northern aspect and in the litter layer, the highest Shannon–Wiener's diversity index was observed in middle land and slpoe

The certainty of forest resources evaluation regarding to emission of atmospheric carbon dioxide could be increased by estimating the organic carbon pool of forest floor. This research aims at exploring the relationship between plant diversity in the different stories pertaining to forest physical characteristics, and variation of carbon sinks of forest floor. The current research was done in control compartment located in the third district of Glandroud forests. The sample plots with 400 m2 area were sytemetically established in the study area which were separated by a distance of 100 m from each other. Four 1 m2 and 50 × 50 cm2 plots were marked at the center and corners of the sampling plot to measure and collect the herbal plants and litter, respectively. 80 g of each herbal and litter sample was separated after weighing in the field and the all samples were oven-dried at 65ºC for 48 hours. Carbon content of each sample was measured and calculated by placing each sample in the heat oven. The results showed that the tree diversity indices are independent of physiographic changes in the studied forest. However, abundance and dominance of herbal coverage were significantly different at altitude and aspect classification, respectively. Among all the studied carbon sinks, carbon sequestration of litter was significantly different at slope classification. The final result indicated that there was no significant correlation between plant biodiversity and amount of carbon sink in grass coverage. In other hand, the significant correlation was found between carbon stock of litter and indices of Shannon, richness, and importance value of tree storey.

Few studies have shown the effect of topographic gradient on the distribution of trees and coarse woody debris (CWD), particularly old growth beech stands. Several studies emphasized relationship between physiographical characteristics of sites and live trees distribution. Valipour et al (2013) studied the effect of physiographic characteristics of sites on dimensional properties of tress. They found that physiographic factors significantly effect on the dimension of trees, the most important factors influencing are the slope. Also Alavi et al (2008) revealed that physiographic factors impact on spatial distribution of elder. Research in the low land forests of Noushar region showed slope and altitude positively effect on diversity indices. The main goals of this research is (1) Evaluation the effect of geomorphic characteristics of sites on living tree distribution and (2) extent and distribution of dead trees
The study was conducted within the Gorazbon section of the Kheyrud Experimental Forest in northern Iran which is owned and managed by the University of Tehran for education, research, and conservation. The site selection was done according to the management history. Selected sites was undisturbed and logging operation don’t was done by now. To characterize coarse woody debris within stands, 50×50 meter gird grid of sampling points established to randomized plot selection and thirty-five 0.1 ha circular plots were established within a natural beech stand using a systematic random sampling technique in order to equally sample across a wide variety of topographical factors. In each plot, we measured percent slope, aspect and land form. Meanwhile the number of dead trees and species and quality was recorded. Therefore, we investigated the influence of topographical factors including slope aspect, slope degree, and landform index (LI) on the distribution of dominant tree species and CWD in undisturbed mixed forests in northern Iran.
F.orientalis had the highest mean density, volume, relative density, relative volume, and RIV of all live and dead trees. Results showed that tree density and basal area were not significantly correlated with any of the measured parameters, except basal area was negatively correlated with LI. Redundancy analysis (RDA) of the tree layer revealed a significant relationship between the measured environmental variables and species distributions on the first canonical axis and all four canonical axes. CWD volume showed significant negative correlation with percent canopy cover and was highly correlated with terrain shape index. Density of CWD in decay class IV was significantly correlated with aspect slope and percent of canopy cover.
Analyses of CWD distributions in relation to both living vegetation and topographic gradients showed a highly complex interplay of factors dictating the distribution of CWD across the forest stands.

Knowledge on silvicultural characteristics of forest stands is prior to any forest management practice. The objectives of this study were to determine the forest types and to explore some quantitative and qualitative characteristics of Arasbaran forest protected area along an altitudinal gradient. Therefore, circular plots of 400 m2 at 50-meter elevation intervals were established along five altitudinal transects, 100 meters apart, from the lowest (1100 m a.s.l) to the highest (1725 m a.s.l) forest limit. In each plot, the physiographic conditions including slope gradient, altitude and geographic coordinates were determined. Woody species were identified and the diameter at breast height (dbh) of all trees above 7.5 cm dbh, as well as origin, health status, number of stems and tree leaning were measured. In addition, the regeneration frequency of each individual tree taller than 1.30 m in three diameter classes (0-2.5, 2.5-5 and 5-7.5 cm dbh) and shorter than 1.3 m in three height classes (0-10, 10-50 and 50-130 cm) were examined within 100 m2 regeneration plots. Four forest types including Carpinus betulus - Quercus petraea (1100-1400 m a.s.l), C. betulus - Q. petraea - Acer campestre- Fraxinus excelsior (1400-1500 m a.s.l), C. betulus - Q. petraea - A. campestre (1500-1650 m a.s.l) and C. betulus - Q. macranthera (1650-1725 m a.s.l) were distinguished along the altitudinal gradient. The highest number of stems per ha (mature and regeneration stands) and average basal area were observed in C. betulus - Q. macranthera type, whereas the highest average dbh was recorded in C. betulus - Q. petraea forest type. Finally, seed regeneration was most common in C. betulus - Q. petraea - A. campestre forest type.

Associations between plant coverage and environmental parameters help to understand the natural habitats, as well as the effective functions on growth and establishment of plant species. The Marsdenia erecta (L.) R. Br. ex DC.is one of shrub species which occurs in forests of Chaharmahal and Bakhtiari province, about which almost no report on ecological characteristics and regional distribution has been published so far. In this study, growth regions of Marsdenia erecta were initially identified following site visits and preliminary checks, based on which two habitats of Chahartagh and Dorak Anari were selected. Field sampling was accomplished by means of 35 circular plots of 1000 m2 each. In each plot, quantitative characteristics of species, including number of standing trees, average crown diameter and height were measured. In addition, a mixture soil samples were collected from the surface soil horizon, which were then analyzed in terms of chemical and physical properties such as electrical conductivity, organic carbon, lime, phosphorus, potassium, nitrogen, sand, silt and clay contents. The properties were statistically analyses on species level. Furthermore, the relationship between Marsdenia erecta distribution and soil characteristics was surveyed by principal component analysis. The results showed maximum diameter, height and canopy of Marsdenia erecta across Dorak Anari test site, whereas Chahartagh test site revealed the highest density. Quantitative results also revealed a significant difference between the measured heights of Marsdenia erecta individuals across the two test sites. However, no significant difference was observed by comparing the mean values of soil variables (acidity, organic carbon, lime, phosphorus, potassium, nitrogen, sand, silt and clay). Based upon the applied principal component analysis, soil texture was the most influential factor on distribution of Marsdenia erecta in Dorak Anari, whereas chemical variables of soil such as organic carbon, phosphorus, potassium and nitrogen were the major determinants in Chahartaghtest site.

In order to survey some phenological phenomena of Kair with climate and physiography properties, this study was carried out in the south-east of Iran from 2008 to 2011. In the first step, distribution of species was recognized in Hormozgan and Balochestan provinces and then 13 habitats were chosen. These habitats were visited in 2-3 week intervals annually. Three trees were marked in each site and were monitored during four seasons and its phenological stages (time of bud break, flowering, fruiting, ripening, fruit, and leaf shedding) and other characteristics were recorded. Climatic data were gathered and phenological stages were analyzed. The results of phenological and meteorological data indicated that the growth patterns of Capparis decidua may alter with fluctuations of drought, annual temperature and precipitation. The phonological stages are repeated two or three times every year. Kair phonological stages are long, Flowering starts during March and continues up to October. It flowers in three seasons: March–April (spring), June-July (summer) and September-October (Autumn). Flowers become fruits within 70 to 90 days and simultaneously, both flower and fruit appear on new shoots. In the northern and western habitats, phonological stages are limited and only occur once or twice a year. But in all conditions, amount of growth degree days (GDD) required for ripening seed is the same and equal to 931ْ C.

Forest reserves are protected areas and the analysis of relationships between vegetation and environmental factors in these areas is ecologically considered as an important issue. To investigate the role of altitude and edaphically characteristics in Tang Khoshk forest reserve in Semirom Esfahan، thirty 0. 2 ha circular plots were randomly established. Four circular subplots were also laid out within each main plot and the competition between shrubs was measured by Schütz competition index. Slope، aspect and elevation were recorded within each plot. For each subplot، soil samples from two depths (0-30 and 30-80 cm) were taken. Soil properties including total nitrogen، organic carbon، organic matter، available potassium and phosphorus، pH and electrical conductivity were measured. Factor Analysis (FA) was used to analyze the data. The results indicated that، nitrogen، carbon and organic matter of both depths are the most important factors affecting the competition followed by slope، elevation and potassium content of the first depth. Generally، it could be concluded that soil factors are of higher importance among all physiographical and edaphically characteristics influencing competition between Amygdalus orientalis species in Tang Khoshk forest reserve.

Habitat needs and requirement of important species in terms of distribution is necessary for natural resources management. Amygdalus scoparia is one of the important forest species in Markazi province for food, industries and environmental protection in different climatic conditions. The effect of physiographic factors such as land form, aspect, altitude, slope and some physical and chemical soil properties on qualitative and quantitative characteristics as height, crown diameter, canopy cover, tree density, regeneration and vitality percent was studied and then the data were analyzed using SPSS and PC-ORD (PCA method). The results of this study showed: 1- maximum height and crown diameter was observed in northern and eastern aspects. 2- The maximum canopy cover and regeneration was seen in northern aspect, valleys and in altitudes 1000-1500 meters. 3- The maximum tree number was observed in southern aspect, amplitude and valley land forms, in altitudes of 1000-1500 and 1500-2000 meters and in slops of 0-20 and 20-35%. 4- The maximum vitality percent was observed in northern and southern aspects, slope and valley land forms, in altitudes of 1000-1500 meter and in slops of 0-20%. The factors of height, crown diameter, canopy cover, tree number, regeneration and vitality were scattered in the positive direction of first axis by Principal Component Analysis (PCA) that had the highest correlation with sand.

This study attempted to investigate leaf area index in Quercus macranthera coppice stand. A forest of 278 hectares located at the northeast of Khalkhal was selected as the study region. The leaf area index was determined by direct method and by collecting all the leaves from the 60 coppice sprouts and measuring the mean leaf area and crown cover area of each coppice group. To determine the soil properties and its relation to the leaf area index, samples from the depth of 0 - 10 and 10 - 30 cm was selected. Physical (percent of clay, silt and sand) and chemical (amount of nitrogen, phosphorus, potassium, organic carbon and pH) properties of soil samples were determined in the laboratory. As a result, the leaf area index of oak species was 3.33 and the average dry weight of leaf was estimated to be 1864 kg/ha. No statically significant relations were observed between the phisiographical conditions and crown canopy density to the leaf area index. Considering the characteristics of the stand and soil, the aboveground biomass, diameter at breast height, tree height and the soil nitrogen showed the maximal correlation with the leaf area index.

Sprout is one of the most important regeneration mechanisms in degraded oak forests. The main goal of this research was study of effects of different physiographical conditions on oak sprout-clumps structure. For this purpose a section of Baba-Kooseh Olia forest in Kermanshah province with an area of 430 ha was selected. Then 84 square sample plots with an area of 1600 m2 by systematic - random network and random starting point were established in the mentioned region. Some important quantitative parameters were measured in plots including maximum height, crown area, basal area and number of sprouts in oak sprout-clumps. 5 altitude classes, 3 slope classes, 4 aspect classes and 3 land form classes were considered too. Result showed that the main woody species was Quercus brantii and average number of sprouts in oak sprout clumps was 5.9. Results of analysis of variances (ANOVA) showed that there was a significant difference between oak sprout-clumps structure relation to altitude and slope changes. There was also a significant difference in sprout number with aspect. The maximum number of sprouts was observed in elevation range of 1600-1700 m.a.s.l., in slope percent range of 0-12%, eastern aspect and in valley land form.