جستجوی مقالات مرتبط با کلیدواژه « ecological amplitude » در نشریات گروه « آبخیزداری، بیابان، محیط زیست، مرتع »

The present study was conducted to study the response curves of Aeluropus lagopoides and Salsola turcomanica along some environmental gradient using HOF function in Inchehboroun rangelands in Golestan province. A randomized-systematic method was used to collect the species occurrence data in four hundred quadrates with size of 4m2, placed along a gradient from watering point. Soil samples were collected from 0-20 cm in all quadrates and their bulk density, soil moisture, pH, N, EC, P, organic carbon, sand, silt and clay content were measured. HOF model with binomial distribution function was used to explore response curves of the species to these soil variables. The data were analyzed by R ver.3.0.2 computer programmer. Results revealed that ecological amplitudes of A. lagopoides and S. turcomanic differ considerably. According to the results, the occurrence range and optimum condition for A. lagopoides were 320-1000m and 874m from watering point respectively. The occurrence range and optimum condition for S. turcomanica occurrence was 200-1000m and 845 m from watering point respectively. A. lagopoides and S. turcomanica response curves to watering point distance and pH gradient had increasing and decreasing monotonically trend respectively. The ecological optimums along the pH gradient were 7.5 and 7.7 for A. lagopoides and S. turcomanica respectively.

The present study was conducted in the rangeland of Glandrood watershed in the province of Mazandaran. The objective of this study was to compare between the ecological amplitude of Festuca ovina L.، and Poa bulbosa L.، using the function HOF along the gradient of the environmental variables. For this purpose 150 plots of 1m2 were established along the altitude gradient. The sampling method was randomized-systematic. In the area sampled، frequency of Festuca ovina and Poa bulbosa، altitude and slope were recorded. Soil samples were taken from 0-20 cm in each plot. In each sample، bulk density، pH، N، EC، organic matter، organic carbon، the percentage of sand، silt and clay were measured. In order to study the shape of response curve and the ecological optimum in relation to the mentioned variables، HOF function was used with binomial distribution function. The data were analyzed by R ver. 3. 0. 2 software. The two species Festuca ovina and Poa bulbosa، mainly showed different ecological amplitude along the gradient environmental variables. The results showed that the ecological amplitude and optimum alonge altitude gradient for Festuca ovina has been recorded 2244-3037m and 3037m respectively for Poa bulbosa 2335-3037m and 2636 m respectively. Also the response curve of Poa bulbosato the altitude has unimodal and symmetric but for Festuca ovina was monotonically increasing trend. The response curve ofPoa bulbosato pH is monotonically decreasing but for Festuca ovina was unimodals symmetric.

The present research was performed in Patom, Namkhaneh, Gorazbon, Chelir and Baharbon districts in Kheyrud forest. Due to existence of forest typology map and extension of study area, this study was confined to beech dominated forests. A stratified sampling method based on landform is used to locate 1000 m2 circular sample plots. The number of Fagus orientalis Lipsky trees ≥ 7.5 cm in DBH within each plot is recorded along with elevation, aspect and slope of the ground. Furthermore, at the center of plot, soil samples from A horizon are taken for analyzing soil texture. Gaussian response function was used. Instead of direct estimation of Gaussian parameters, it is customary to fit an equivalent polynomial model. This can be easily fitted as a generalized linear model (GLM) with a logarithmic link function. This function showed beech has 1347 and 464-2231 m a.s.l for its optimum and ecological amplitude, respectively. North-facing slopes (optimum 43 degree) are the most suitable slope for Fagus occurrences. Beech tree can distribute from gentle to steep slopes in the study area, but this species in 39% slope has the best performance. Using generalized linear model showed Fagus can tolerate slopes from 3 to 74%. In light of sand, clay and silt, Beech tree has 25%, 43% and 35 % for optimum and 4-46 %, 25-60% for clay and 15-55 % for silt for ecological amplitude, respectively.