放牧对鄂尔多斯高原油蒿草场生物量及植被-土壤碳密度的影响

以围封保护和自由放牧油蒿草场为研究对象,通过野外调查与室内分析,研究了围封和放牧条件下沙地草场生物量和植被-土壤碳密度。结果表明:(1)自由放牧使油蒿群落中植物种类增加,但降低了植物群落盖度。自由放牧不仅导致油蒿草场地上、地下总生物量降低,也使得油蒿地上、地下生物量占群落地上、地下总生物量的比例减小。生长季自由放牧样地凋落物生物量显著大于围封保护样地(P0.05);(2)围封保护样地植被碳密度大于自由放牧样地,土壤碳密度却小于自由放牧样地,但两个样地间差异不显著(P0.05);(3)油蒿草场90%以上的碳储存于土壤中,围封保护样地和自由放牧样地油蒿草场土壤碳密度占植被-土壤系统碳密度的91%、93%;(4)围封保护油蒿草场碳密度为2.29 kg/m2,自由放牧油蒿草场碳密度为2.68 kg/m2,两个样地间差异不显著,自由放牧对油蒿草场碳密度影响不大。

Effects of grazing on plant biomass and the carbon density of vegetation and soil in the Artemisia ordosica shrubland of the Ordos Plateau

Plant biomass and the carbon density of vegetation and soil in enclosed and grazed Artemisia ordosica shrubland of the Ordos Plateau were studied in the field and in the laboratory. The results revealed that the grazed plots supported plant communities with a higher the number of species yet lower vegetation coverage than did the enclosure plots. Grazing, moreover, reduced the overall above-and below-ground biomass of plant communities, as well as the proportion of above-and below-ground biomass consisting of A. ordosica. Nevertheless, during the growing season the grazed plots produced significantly more litter biomass than did the enclosure plots (P < 0.05). When protected by enclosures, however, the carbon density of the vegetation was higher, whereas that of the soil was lower, than that under grazing; although their seasonal averages did not differ significantly between the two plot treatments (P > 0.05). Ninety percent of carbon storage was in the soil in A. ordosica shrubland. The percentages of carbon density of soil accounting for the vegetation-soil system were 91% in enclosed plot and 93% in grazed plot, respectively. The carbon density of A. ordosica shrubland was 2.29 kg/m² in enclosed plot and 2.68 kg/m² in grazed plot. Grazing had little impact on carbon density of vegetation-soil in A. ordosica shrubland.