放牧干扰下高寒草甸物种和生活型丰富度与地上及地下生物量的关系

明晰放牧干扰下高寒草甸植物丰富度与生物量的相关关系,为草地植物不同生长时期生物量的预测提供依据。设置6个放牧强度样地,连续3a放牧,2014年进行3个季节(6月、8月、10月)的植物丰富度和地上、地下生物量调查,对比分析放牧干扰下物种和生活型丰富度(生活型的种类)分别与地上、地下生物量的相关关系。结果表明:(1)物种和生活型丰富度与地上生物量均受放牧强度的显著影响,物种丰富度仅在8月与放牧强度显著负相关,生活型丰富度在10月随放牧强度单峰变化,地上生物量在不同季节均与放牧强度显著负相关,而地下生物量与放牧强度无关。(2)物种丰富度与地上和地下生物量均受季节的显著影响,物种丰富度和地上生物量仅在低强度放牧区随季节呈单峰变化,地下生物量在中等强度放牧区随季节呈单峰变化;生活型丰富度与季节无关。(3)放牧干扰前物种和生活型丰富度与地上和地下生物量均显著正相关。3a放牧后仅在8月,物种丰富度只与地上生物量显著正相关,生活型丰富度与地上和地下生物量均显著正相关。(4)对于不同放牧强度,物种丰富度仅在低强度放牧区与地上生物量显著正相关,而生活型丰富度在所有放牧强度区均与地上生物量显著正相关。综上所述,放牧干扰扰乱了高寒草甸丰富度与生物量之间的关系,尤其影响了物种丰富度与地下生物量之间的相关关系。生活型丰富度与地上生物量之间的显著关系不受放牧强度干扰,使生活型丰富度在预测生物量方面表现出优势。

Study on the relationships between plant species richness, lifeform richness, and above-and belowground biomass under grazing disturbance in an alpine meadow

Understanding the interrelationships between plant richness and biomass under grazing disturbance is of importance for predicting biomass during different plant growth periods. In this study, we conducted a controlled grazing trail with six grazing intensities in an alpine meadow in the eastern Qilian Mountain from 2012 to 2014. We investigated species richness, lifeform richness, and aboveground and belowground biomass in three grazing seasons (June, August, and October). We analyzed the relationships between plant species richness, lifeform richness, and aboveground and belowground biomass under different grazing intensities. The following results were obtained:(1) Species richness and lifeform richness as well as aboveground biomass were significantly affected by grazing intensity. Species richness was only negatively correlated with grazing intensity in August, whereas lifeform richness showed a single-peak trend in October with grazing intensity. The aboveground biomass was significantly negatively correlated with grazing intensity in different seasons; however, the belowground biomass was not related to grazing intensity. (2) The species richness and aboveground and belowground biomass were significantly affected by the different seasons. The species richness and aboveground biomass showed only a single peak change in the low grazing intensity plot with seasonal changes, and the belowground biomass showed a single peak change in the medium grazing plot with seasonal changes. There was no relationship between lifeform richness and grazing season. (3) There was a significant positive correlation between species and lifeform richness and aboveground and belowground biomass before grazing disturbance. After 3 years of grazing, species richness was positively correlated only with aboveground biomass in August, and lifeform richness was positively correlated with aboveground and belowground biomass in August. (4) Among the different grazing intensity plots, the species richness was significantly positively correlated with aboveground biomass only in the low grazing intensity plot, whereas lifeform richness was positively correlated with aboveground biomass in all grazing intensity plots. In conclusion, grazing disturbed the relationship between plant richness and biomass in alpine meadows, particularly between species richness and belowground biomass. The significant relationship between lifeform richness and aboveground biomass was not affected by grazing intensity. Consequently, lifeform richness showed superiority in determining the biomass in an alpine meadow.