Spatial heterogeneity of vegetation under different grazing intensities in a Stipa breviflora desert steppe
Aims Our objectives were to determine whether exponential function law is suitable to fit different levels of plant spatial heterogeneity in Stipa breviflora desert steppe,and to elucidate the patterns of species and community spatial heterogeneity under different grazing intensities,for better understanding the influence of grazing on plant community diversity,productivity and stability.Methods An experiment with randomized complete block design was conducted at the study site with four treatments and three replications for each treatment.The treatments consisted of light grazing,moderate grazing,heavy grazing and no grazing,respectively.Samples were taken from 50 cm × 50 cm quadrates (L quadrate) at every 0.5 m along three 50 m line transects,and totally 100 quadrates were measured.Each L quadrate was equally separated into four 25 cm × 25 cm smaller quadrates (S quadrate).All species appeared in the S quadrates were recorded at the peak growth period.The exponential function law was used to fit the data in different grazing treatments.Important findings Results showed that the species studied had good concordance with exponential function law under different grazing intensities.With increases in grazing intensity,based on the species occurrence frequency,plant community gradually shifted from a mixture of Stipa breviflora,Cleistogenes songorica,Artemisia frigida,Salsola collina to mixed Stipa breviflora and Cleistogenes songorica.The spatial heterogeneity was species-specific in different grazing treatments.With increasing grazing intensity,the plant species with increased spatial heterogeneity gradually reduced from Cleistogenes songorica,Arternisia frigida,Stipa breviflora,Convolvulus ammannii,Salsola collina,Allium mongolicum,Leymus chinesis,Chenopodium aristatum,and Haplophyllum dauricum to only Cleistogenes songorica and Stipa breviflora.The number of species with greater spatial heterogeneity than community spatial heterogeneity deceased from the control to the heavy grazing treatment.
desert steppegrazing intensitypower function lawspatial heterogeneity
NETL
NSTL
万方数据
维普
