三江源区高寒坡地退化植物群落多样性和地上生物量沿海拔梯度的变化特征

Variation characteristics of plant community diversity and above-ground biomass in alpine degraded slopes along altitude gradients in the headwaters region of three-river on Tibetan plateau

山地生态系统退化对生物多样性和地上生物量,以及相互关系在海拔高度梯度上的格局影响,是认识全球变化和人类干扰引起自然生态系统变化的重要内容。以青藏高原三江源区高寒坡地退化草甸和灌丛为研究对象,探讨退化草甸、灌丛群落物种多样性与地上生物量关系及其沿海拔梯度的变化规律。结果表明:(1)坡地退化的上坡位植被盖度显著大于下坡位(P<0.05)。坡地退化高寒草甸和高寒灌丛,植物物种多样性沿海拔梯度变化规律一致,均呈现“单峰”分布格局。坡地退化高寒草甸Shannon-wiener指数和Simpson指数二次回归方程解释度达到80%和70%以上(P<0.05)。(2)坡地退化高寒草甸和高寒灌丛的地上生物量与海拔梯度的变化规律一致,即随海拔升高高寒坡地地上生物量呈先增加后降低的变化趋势。海拔梯度对退化高寒山地地上生物量的解释度达到85%以上(P<0.05)。(3)物种多样性和地上生物量的关系在两个坡地上表现出一致的规律,呈线性增加的变化趋势。高寒草甸坡地回归方程解释度达到70%,高寒灌丛坡地达到60%(P<0.05)。坡地退化高寒灌丛植物群落多样性和地上生物量高于高寒草甸植物群落。高寒坡地退化草甸和灌丛植物群落物种多样性以及其与地上生物量之间的关系沿海拔梯度的变化规律一致,海拔梯度造成的环境差异对植物群落物种多样性和地上生物量影响仍较大。该研究对认识三江源区退化山地形成生态学机制,及提出有效的生态恢复措施具有重要参考价值。

The impact of alpine ecosystem degradation to biodiversity and aboveground biomass and the two interaction patterns along with the gradient of elevation are critical for understanding the changes in natural ecosystems that induced by global climate change and human disturbance.This research focused on the degraded meadow and shrub of hillside in the headwaters region of three-river on Tibetan plateau and aimed to investigate their relationship between plant species diversity and above-ground biomass along an elevation gradient.We observed that:(1)the vegetation coverage on the upslope of degraded sloping alpine meadows and alpine shrubs was significantly greater than that on the downslope(P<0.05).Both degraded slopes of alpine meadows and alpine shrubs exhibited a unimodal pattern of plant species diversity over elevation gradients.Furthermore,the interpretation rate of the quadratic regression equations of the Shannon-wiener index and the Simpson index against elevation gradients on alpine meadow slopes achieved more than 80%and 70%,respectively(P<0.05).(2)The above-ground biomass of degraded sloping alpine meadows and alpine shrubs was consistent with the altitude gradient,that is,the above-ground biomass of alpine meadows and alpine shrubs increased initially then declined with the increase of altitude.Interpretation rate of the quadratic regression equation indicated that the altitude gradient could accounted for more than 85%of the above-ground biomass in degraded alpine meadows and alpine shrubs(P<0.05).(3)The association between plant species diversity and above-ground biomass exhibited a similar pattern on both alpine meadows and alpine shrubs slopes,which proved to be a linear increasing trend.The interpretation rate of the regression between plant species diversity and above-ground biomass reached more than 70%on alpine meadow slopes and more than 60%on alpine shrub slopes(P<0.05).Also,the alpine shrubs on degraded slope land had higher plant community diversity and above-ground biomass than alpine meadow plant communities.The species diversity of plants in degraded alpine,alpine meadows,and alpine shrub slopes,as well as their relation with above-ground biomass,was consistent with the pattern of changes along elevation gradients in degraded alpine mountains.These findings suggest that environmental variations induced by altitude gradients continue to have a stronger influence on plant community species diversity and above-ground biomass.This study has important reference value for understanding the formation ecological mechanism of degraded alpine meadow and shrub of hillside in the headwaters region of three-river on Tibetan plateau and putting forward effective ecological restoration measures.