晋北盐碱化赖草草地群落特征对不同放牧强度的响应

Response of community characteristics to different grazing intensity on salinization Leymus secalinus grassland in the north region of Shanxi Province

在盐碱化赖草(Leymus secalinus)草地设置不放牧、轻度放牧、中度放牧、重度放牧和极度放牧5个放牧强度研究赖草草地群落特征的变化,以期为确定草地合理的载畜量和优化草地的利用方式及利用率奠定基础。研究表明,中度放牧强度时,主要优势种赖草和鹅绒委陵菜(Potentilla anserina)的盖度、频度都达到最大,而密度和高度的变化趋势不明显,艾蒿(Artemisia lavandulaefolia)、草地风毛菊(Saussurea amara)、蒲公英(Taraxaacum mongolium)的盖度达到最大;随着放牧强度的增大,草地主要优势物种的优势度有下降的趋势,个别耐牧且繁殖能力强的物种优势度逐渐增加;草地现存量随着放牧强度的增大逐渐减小,但在中度放牧时有增大的趋势。经过两轮放牧后,不同放牧强度下,植物群落的Shannon-Wiener多样性指数、Simpson优势度指数、E.pielou均匀性系数和Margalef物种丰富度指数差异显著(P<0.05);在中度放牧强度下,草地群落主要优势种的盖度、频度相对较大,具有较高的物种丰富度和优势度,但均匀度较低。

The five grazing levels （i. e. no grazing（CK）, grazing light（LG）, moderate grazing（MG）, heavy grazing（HG） and extreme grazing（EG）） was used to investigate the effect of grazing intensity on community characteristics of Leyrnus secalinus grassland for determining a reasonable grazing capacity, which further optimize the utilization patterns of grassland. This study showed that the cover and frequency of the dominant species L. secalinus and Potentilla ansrina were maximum in the MG, but the changes of density and height were not significant（P〉0. 05） ;the cover of Arternisia lavandulaefolia, Saussurea arnara and Tarazcacum mongolicum were maximum in the MG. As grazing intensity increased, the dominance of the main species had downward trend in this grassland and the dominance of individual species resistance to grazing and the ability to propagate species increased gradually; the grassland biomass increased with the decrease of grazing intensity, but had increasing trend in the MG. After two-time of grazing, The Margalef species richness index, Shannon-Wiener diversity index, Simpson dominance index and Pielou uniformity of grassland communities were significantly different （P〈0.05）. In MG, the species richness was maximum. The grassland community had high species richness and dominance, but the uniformity was low in the MG.