Journal of Rangeland

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  This study aimed to evaluate the response of Festuca ovina to some environmental variables using HOF function in Galandrood watershed rangelands located in Mazandaran province. A randomized-systematic sampling was used to establish 150 quadrates of 1m² along an elevation gradient. Frequency of Festuca ovina, elevation from sea level, slope and aspect were recorded in the all quadrates. Soil samples were taken from 0-20 cm in each quadrates and bulk density, pH, N, EC, organic matter, organic carbon, sand, silt and clay percentages were measured. HOF function with binomial distribution was used to provide the response curves and identify ecological optimum point of F. ovina to the measured environmental variables. The data were analysed using R ver.3.0.2 program. The results showed a monotonically increasing trend for F. ovina frequency to elevation. The optimum frequency and elevation range of the species were 3037 and 2244 – 3037 meters from sea level, respectively. The behavior of F. ovina to EC, organic carbon, sand and slope was a monotonically increasing trend, but its frequency was decreased where the soil clay content was increased. It implies that F. ovina does not prefer heavy soil texture. F. ovina frequeny had a symmetric unimodal response to the soil pH.

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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.

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The objective of this study was to investigate the response of Bromus tomentellus species to some environmental variable using HOF function in Galandrood watershed rangeands - Mazandaran province. Randomized-systematic approach was used to collect environmental data such as elevation, slope, aspect and the frequency of B. tomentellus in 153 quadrates of 1m² was measured. Soil samples were collected from 0-20 cm in each quadrate and their pH, N, EC, organic carbon, sand, silt and clay percentages were measured. HOF with binomial distribution function was used to produce response curve of the species against environmental variables, and identify the ecological optimum of the species. The data was analysed by R_ver.3.0.2 computer porgramme. The results showed that B. tomentellus occurs in the areas with elevation range of 2125 to 2975m. According to the respose curve of the species, B. tomentellus frequency had monotonically decreasing trends to clay, silt, aspect and pH, but its frequency against organic carbon, sand and N had monotonically increasing trend. Although the species frequency had an increasing threshold behavior against elevation and slope, it had decreasing threshold behavior to precipitation and temperature variables. Elevation was identified as the most important variable affecting B. tomentellus occurrence in the study area as it affects most ecological parameters.
 

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This study aimed to compare the ecological amplitudes of Trifolium repens and Phlomis cancellata using HOF function along some environmental gradients in rangelands of Glandrood watershed – Mazandaran province.  A randomized-systematic approach was used to collect frequency of Trifolium repens and Phlomis cancellata in 153 plots of 1m² along the elevation gradient. Soil samples were collected from 0-20 cm in each plot and their pH, N, EC, organic matter, organic carbon and soil texture were measured. HOF function was used with binomial distribution function to provide response curves of the species and identify their optimum ecological condition. The data were analyzed using R ver.3.0.2 software. The results indicated that the two species had different ecological amplitude. Trifolium repens occurs in elevation range of 2125-2975 m and its optimum elevation was 2125 m. Phlomis cancellata appeared from 2184 to 2975 m but its optimum elevation was 2246 m. The response curve of Phlomis cancellata to the elevation was unimodal and asymmetric but it had monotonically decreasing trend for Trifolium repens.