comparison of the ecological amplitude of festuca ovina l., and poa bulbosa l.,to some environmental variables using the function hof (case study: rangeland of glandrood watershed)

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.