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

The Ferula spp. is one of the most important genus of rangeland plants in the northeastern region of Iran and plays an important role in soil conservation and livelihood of rangeland stockholder. However, improper exploitation and destruction of the plant's habitats are among the factors threatening this natural capital. This study was conducted to identify potential habitats of this genus in the two provinces of Khorasan Razavi and North Khorasan, which can be a step to facilitate and develop replanting and rehabilitation operations of this genus. Spatial data of the presence of this genus with a pixel size of 1100*1100 m were used as actual suitable sites for its growth and layers of environmental information such as climate, soil, geology and physiography were used as predictor variables. First, in Biomapper software version 4, the correlation of prediction variables was examined and important independent variables were selected. The potential habitat map extracted from distribution model mapped using Maxent 3.3 software. The results showed that the model used had good accuracy and reached the AUC of 0.94. In terms of importance. Investigating the input variables to the model using the Jackknife test showed that the variables of the slope, Geology, Soilland, habitat altitude (dem) and the annual average temperature (Bio1) have most important roles in the potential habitat of Ferula spp. In the study area the results of this study can be used to identify the ecological needs of species under study and development and revitalization of its habitats.

Lack of studies in forest Watersheds due to the hydrometric stations absence always causes many problems for managers. The Naplarrood watershed, which has a permanent flow throughout the year and includes many villages downstream, can be the basis for the development of the region in the future with principled and scientific planning. In this research, it is tried to extract some of its important features by geometric analysis of Naplarrood Watershed. Therefore, in this study, 12 effective physiographic factors were used in the field of flood current origin. These factors include river channel bed slope, roundness coefficient, compaction coefficient, Horton coefficient, elongation coefficient, equivalent rectangle length, equivalent rectangle width, slope percentage, slope aspect, branch ratio, drainage density and time of concentration. Then, in order to determine the source of flood flow, all effective factors were rated and weighed based on the used data. Then, flood flow was prioritized using single parameter sensitivity analysis method, as the effective factors in the source. According to the results of sensitivity analysis, three factors of river slope bed, slope percentage and drainage density with weights of 7.42, 6.72 and 6.64 were identified as three important factors in the source of flood flow. Among the effective factors, three factors of drainage density, equivalent rectangle width and branching ratio had a higher optimal weight than the initial weight assigned to them, which shows the importance of these three factors in the origin of flood flow in forest basins.

Rhamnus pallasii is one of the most important and valuable species in Khalkhal forest area. This study aimed to determine the relationship between vegetation properties of Rhamnus pallasii with soil and physiographic factors using PCA analysis in this forest reserve. In so doing, from 1030 to 2250 m.a.s.l, 48 sample plots of square shape with an area of 400 m2, in three land forms (ridge, valley and slope) in four aspects (north, south, east and west) were selectively determined and quantitative characteristics of Rhamnus pallasii such as total height, collar diameter, crown diameter, shoot and regeneration were measured. In addition, in each sample plot, a mixture soil samples were collected from 0 to 30 cm and some of its physical and chemical properties were measured in the laboratory. In order to study the relationship between Rhamnus pallasii distribution and soil characteristics, a survey was done by principal component analysis. The results showed that the distribution range of Buckthorn varies from 1030 to 2250 m.a.s.l. In general, hillsides and valley forms with south -facing hillsides are suitable sites for this species. The highest mean of height (1.74 m), collar diameter (5.65 cm) and crown diameter (1.75 m) on slope land form and number of regeneration in sample plots (7.4) were observed on valley land form. Results from PCA analysis revealed that in the altitude range of 1030 to 2250 m.a.s.l, the soil texture, especially sand% and silt%, OC% and N% were more suitable conditions for the presence and growth of this species in valley and slope forms in the southern aspects area provided. The results of this study can be used to describe ecosystem sustainability as well as conservation and reforestations such as planting with this species and modifying the structure of deforested forests in the studied areas.

The present study was performed to identify diversity indices of herb layer functional groups and its relation to physiographical factors in central Zagros forest, Lorestan. For this purpose, sampling of herbaceous plants was conducted randomly in plots of 2×2 m (n=50) in site. All plants were classified to functional groups including forbs, graminoids and legumes, also Raunkiaerchr('39')s life-forms. Diversity values (Richness, Shanon-weawerchr('39')s diversity and Hillchr('39')s evenness indices) were measured in each plot. Totally, 103 plant species were identified which belong to 27 families and 82 genera. Results indicated that aspect influenced the forbs as well diversity indices of graminoids and legumes, but slope and altitude had no effect on diversity indices. In research site, aspect had important impact on plant distribution and diversity of plant functional groups. Generally, it can be stated that ecological and managemental factors including landuse changes and grazing intensity in Zagros region influenced the plant species composition.

This study aimed to evaluate floristic list, life forms and chorology of plant species of Shalam protected area, which is in western Iran. This region characterized by various physiographic conditions and oak (Quercus brantii L.) as the dominant tree species. Plant species were collected by field survey in May and June 2016. The species were identified and their chorology, growth form and life form were determined using taxonomy resources. The results showed that flora of this region includes 129 plant species, belonging to 34 families and 101 genera. The Poaceae (20 species), Papilionaceae (18 species), Asteraceae (15 species) and Lamiaceae (12 species) were the most frequently encountered families. The number of species was more in the south than in the north-facing slope in different elevation classes. According to Raunkiaer’s classification of life forms, therophytes and hemicryptophytes were the dominant life forms in the study area. In addition, annunal and perennial forbs dominated the growth forms of both facing aspects. In geographical distribution point of view, Irano-turanian and Irano-turanian- Mediterranean in all physiographic conditions had the highest geographical distribution.

To investigate the relationship between slope، aspect and elevation and quantitative characteristics of plant species، totally 125 sampling plots were selected in a block systematic design. In each sampling، plot presence، number، height، diameter at breast height (for trees) or root collar (for shrubs) and crown diameters were measured and recorded. Also، we recorded vegetation type according to the portion of species in the plot. Correlation analysis was conducted according to the scale of variables using Pierson، Spearman، Phi and Cramer and Eta coefficients. Results found that elevation is the most important factor affecting presence and density and also type in the study area. Altogether، Atlas Pistach (P. atlantica F. & M) and Wild Almond (A. scoparia Spach.) in low elevations and Maple (A. cinerascens L.)، Marsh-arrow-grass (A. lycioedes Spach.) and mountain almond (A. elaefnifolia Spach.) in higher elevations had better conditions. Slope had a negative correlation with presence of Wild Almond and Send Cherry (Ephedra spp)، and positive correlation with the presence of other species. Also، Wild Pistach trees present in southern aspects showed more basal area and volume in these aspects. Results of this research can be used in the detection of suitable points for development of plant species. Regression analysis showed that frequency of almond and Send Cherry and average height of almond and wild Pistach were predictable according to elevation and slope. Of course، coefficient of determination was low in all cases.

Regarding high economic and conservative values of Zagros forests, and livelihood dependency of local people these recourses, determination of sites with higher conservation index can help us to maintain biodiversity of these forests more efficiently. Therefore, 49 plots with 450 m2 in area accompanied by 1, 10 and 45 m2 subplots were taken as systematic random design in research forests of Yasouj University. The number of species in each plot and subplot was recorded. The conservation values for different physiographic regions of forest were calculated using integrative parameters such as the number of species per plot, number of rare species per plot, number of tree species per plot, Jaccards similarity coefficient and slope of species-log(area). Comparing the conservation index in different physiographic sites revealed that the areas located in the north, hills and lower altitudes can be considered for in situ conservation due to higher number of trees, rare species and total plant species, species-log (area) slope and lower amount of Jaccard similarity coefficient. But, vegetative sites located in lower slopes and south, because of lower conservation index, can be used for other multipurpose forestry activities. Using this index for different forest areas can be potentially conducted for better conservation and management of Zagros forests.