高寒草甸功能群组成及营养品质对不同放牧强度的响应

Responses of alpine meadow functional group composition and nutrient quality to grazing intensity

为了探究高寒草甸对牦牛长期放牧活动的响应,选择青藏高原高寒草甸为对象,调查不同放牧强度对高寒草甸植物群落生物量、功能群组成变化和牧草品质的影响,探讨植被功能群组成变化及牧草品质之间的互作关系。结果表明:1)禁牧处理下的植物群落生物量最高,但植物群落生物量在有放牧的样地随放牧强度的增加呈下降趋势;2)物种丰富度和多样性随放牧强度的增加基本呈单峰变化,中度放牧下群落多样性指数、物种丰富度和均匀度指数均高于轻牧和重牧;3)植物粗蛋白与粗灰分含量随放牧强度增加而上升;4)放牧强度增加,豆科、毛茛科和杂类草比例无显著变化(P>0.05),禾本科占比降低,禾本科与莎草科呈此消彼长的关系;5)功能群组成变化与牧草营养之间有显著相关关系,其中粗蛋白含量随禾本科比例下降而下降,但与豆科、毛茛科及菊科占比呈负相关关系,莎草科占比与中性洗涤纤维呈显著正相关关系。综上所述,不同放牧强度下植物群落特征及营养品质发生不同程度的变化,对比禁牧,轻度放牧对地上和地下生物量有最优的促进作用,中度放牧有助于群落物种多样性的增加。适度放牧可以保持草地植物群落稳定,促进草地生态系统可持续发展。

To explore the responses of alpine meadow to long-term grazing activities of yaks,the alpine meadow on the eastern margin of the Qinghai-Tibet Plateau was selected as the research object.The effects of different grazing intensities on plant community biomass,functional group composition changes and forage quality were investigated in alpine meadow,and the interaction between vegetation functional group composition changes and forage quality was discussed.The results showed that:1)The plant community biomass under grazing prohibition treatment was the highest,but the biomass of plant community decreased with the increase in grazing intensity.2)Species richness and diversity showed a single peak with the rise in grazing intensity.The community diversity index,species richness,and evenness index under moderate grazing were higher than those under light grazing and heavy grazing.3)Plant crude protein and crude ash content increased as grazing intensity increased.4)With the increase in grazing intensity,there was no significant change in the proportion of Leguminosae,Ranunculaceae,and Forbs,while the proportion of Gramineae decreased.The proportion of Gramineae and Cyperaceae varied in the opposite way.5)There was a significant correlation between the composition of functional groups and forage nutrition.The crude protein content decreased with the decrease in the proportion of Gramineae.However,it was negatively correlated with the proportion of Leguminosae,Ranunculaceae,and Asteraceae.In summary,plant community characteristics and nutritional quality have changed to different degrees under different grazing intensities.Compared with grazing prohibition,light grazing had the most effectively promoted aboveground and underground biomass.Moderate grazing was conducive to improving community species diversity,maintaining grassland plant community stability,and promoting sustainable development of grassland ecosystems.