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Original Article

Effects of Soil and Topography Variables on Canopy Cover of Dorema ammoniacum D.Don. in Soltan Mohammad Rangeland, Sabzevar, Iran

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Abstract

Environmental factors have huge impact on yield and distribution of plant species. For this purpose, the response of Dorema ammoniacum (Apiaceae( canopy cover to some environmental factors was investigated in its natural habitat in south of Sabzevar, Iran in 2018-2020. Generalized Additive Model (GAM) was used to investigate the response of this species to soil and topography factors. The results showed that the edaphic and physiographic factors of the habitat had significant effects on the canopy size of D. ammoniacum. Environmental factors such as sand, litter, organic matter, lime, pH, N, P, K and altitude followed a monotonic increase model in response of canopy size. So, by increasing these factors, the canopy size of D. ammoniacum increased. In contrast, the response of canopy cover of this species to the gradient of clay, slope, EC, and SAR was a monotonic decrease model so that by increasing of these factors, the canopy percentage of D. ammoniacum was decreased. Results of the soil study showed that the plant is principally distributed on sandy loam and loamy sand soils. The reaction pattern of D. ammoniacum canopy cover in confronting with the gradient of silt, bare soil, and stone and gravel followed unimodal and the optimal level for them was 1%, 30% and 1%, respectively. Generally, investigation of D. ammoniacum canopy reaction to gradient of some environmental factors gave profitable data for characterizing the ecological demands of this plant. In other words, awareness of the impact of environmental factors on D. ammoniacum canopy cover can give range managers good information to recognize arable lands for cultivating this important species and recovering its destroyed habitats.

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