青藏高原植被结构变化反映环境变迁

草地植被结构对于其生产和生态功能至关重要,但大尺度信息严重匮乏.本研究结合多源遥感数据和深度学习,在区域尺度上厘清了青藏高原高寒草地基于群系的植物群落结构空间格局,并比较了其历史变化.过去40年,高寒草甸在高寒草地中的比例从50%上升到69%,反映了变暖变湿的环境变化.此外,高寒草甸和高寒草原中高山嵩草草甸和紫花针茅草原的优势度分别增强到76%和92%.其中,气候因子驱动了紫花针茅草原近些年的分布;高山嵩草草甸近些年的分布则并非完全由气候驱动,人类活动可能起重要作用.本研究首次探索了区域尺度植被结构特征与历史变化,为认识青藏高原草地变化的驱动力及其空间异质性提供了新视角.

Using balance of seasonal herbage supply and demand to inform sustainable grassland management on the Qinghai–Tibetan Plateau

To mitigate the impacts of grassland degradation on the Qinghai–Tibetan Plateau(QTP), in recent decades China has been implementing large-scale conservation programs and has invested about 42 billion CNY(7 billion USD). However, these programs are faced with major challenges involving trade-offs between ecological function, livestock production and income of pastoralists.Scientific assessments, as well as technical and policy issues, have not fully captured the complex ecological,social and economic dynamics of the challenges facing grassland management on the QTP. Pastoral livestock production on the QTP is characterized by imbalance in both quality and quantity between livestock seasonal nutrient requirements and herbage production, which forces pastoralists to keep larger numbers of livestock for longer periods, leading to overgrazing. To solve these problems, an integrated crop-livestock system is promoted to improve the efficiency of livestock production and conserve natural grassland as well for a sustainable system for the QTP.

The plateau pika has multiple benefits for alpine grassland ecosystem in Qinghai–Tibet Plateau

The plateau pika(Ochotona curzoniae)has been engaged in pest control for many years based on the logic that the plateau pika is responsible for alpine grassland degradation and competes with livestock for forage resources.However,the plateau pika is an important species which has multiple benefits in Qinghai-Tibetan Plateau,as it(i)makes burrows that are the primary homes for lizards and a variety of small birds;(ii)creates microhabitat disturbance that promotes the increase of plant species richness;(iii)serves as the principal prey for almost all of the plateau predator species;and(iv)contributes positively to the dynamic equilibriumof alpine ecosystems.

Using functional trait diversity to infer community assembly mechanisms:an exclosure experiment as an example

Aims The Qinghai-Tibetan Plateau has a mean altitude exceeding 4000 m and covers about 2.5 million km2.More than 60%of this area is alpine grassland.Exclosures have been widely used in this region to study the sustainable use of grassland resources.We used patterns of functional trait diversity to infer the effects of exclosures on com-munity assembly in alpine meadows.Methods We studied functional diversity using five traits under grazing and three enclosed(exclosure)plots(3,8,and 18 years old)in an alpine meadow on the Qinghai-Tibetan Plateau.We quantified the strength of the community assembly processes by comparing the observed functional trait diversity with a null model that assumes random community assembly.Important findings We found evidence for deterministic assembly processes for plant communities in exclosures.The changes in CWM of the five traits from grazing land to 18-year exclosure indicated that environmen-tal filtering occurred due to the exclosures.Multivariate functional diversity(MFDis and MPDses),and functional diversity of individual traits,including that of leaf area,leaf weight and aboveground bio-mass(FDis of leaf area,leaf weight,and aboveground biomass),increased gradually from grazing land to the 18-year exclosure,and the values of the 18-year exclosure were significantly greater than null expectation.This can be interpreted to indicate that exclosures resulted in greater competitive interaction between species.These results suggest that the effect of exclosures on community assembly is more deterministic than stochastic in this meadow.

Correction

The manuscript has been republished with updated references of previous experimental studies.These references have been added in order to further reflect the confirmation and scientificity of the results.References have been added as follows.