放牧对川西北高寒草甸植物物种丰富度和生物量的影响

摘要

This study aimed to elucidate the effects of yak (Bos grunniens) grazing intensity on aboveground biomass and identify the optimum grazing intensity of alpine meadow in northwest Sichuan area.Three grazing intensities were considered, namely light grazing (0.71 yak·ha-1), moderate grazing (1.19 yak·ha-1), and heavy grazing (1.60 yak·ha-1), which were selected based on the food intake of the yaks and the average annual biomass of the meadow.The grazing experiment lasted for 3 years.The species richness of the plants and the aboveground biomass were determined.The results showed that the species richness tended to decrease as the grazing intensity increased.In the third year of grazing, the annual aboveground biomass of the meadow under moderate grazing was the highest, followed by that of the meadow under light grazing, and that of the meadow under heavy grazing was the lowest.In the third year, compared with the first year, there was a decrease in the proportion of forbs and an increase in that of grass among the annual biomass in the meadows under light and moderate grazing.In contrast, there was no change in the proportion of forbs and a decrease in that of grass in the meadow under heavy grazing.Meanwhile, the proportion of sedge increased in all meadows irrespective of the grazing intensity.In conclusion, moderate grazing (1.19 yak·ha-1) is best due to its beneficial effects on yield and the growth of grass and sedge.%为确定川西北地区高寒草甸的最佳放牧强度,根据牦牛的采食量和草地地上生物量,设置了轻度(0.71头·hm-2)、中度(1.19头·hm-2)、重度(1.60头·hm-2) 3个放牧强度处理,进行连续3年的放牧,测定其对草地植物物种丰富度、地上生物量的影响.结果表明,随着放牧强度的增加,植物物种丰富度呈下降趋势;放牧第3年,中度放牧草地年度地上生物量最高,显著高于其它两处理(P<0.05),轻度放牧次之,重度放牧最低;和放牧第1年相比,轻度放牧和中度放牧草地地上生物量中杂类草生物量比例显著减少(P<0.05),禾草生物量比例显著增加(P<0.05),而重度放牧草地杂类草生物量比例未变,禾草生物量比例显著下降(P<0.05),但3个放牧处理中莎草占地上生物量的比例均显著增加(P<0.05).因此,川西北地区高寒草甸的最佳放牧强度为1.19头·hm-2,这利于草地高产和优良牧草禾草及莎草的生长.