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Assessment of the vulnerability of alpine grasslands on the Qinghai-Tibetan Plateau.

ABSTRACT: Assessing ecosystem vulnerability to climate change is critical for sustainable and adaptive ecosystem management. Alpine grasslands on the Qinghai-Tibetan Plateau are considered to be vulnerable to climate change, yet the ecosystem tends to maintain stability by increasing resilience and decreasing sensitivity. To date, the spatial pattern of grassland vulnerability to climate change and the mechanisms that vegetation applies to mitigate the impacts of climate change on grasslands by altering relevant ecosystem characteristics, especially sensitivity and resilience, remain unknown. In this study, we first assessed the spatial pattern of grassland vulnerability to climate change by integrating exposure, sensitivity, and resilience simultaneously, and then identified its driving forces. The results show that grasslands with high vulnerability were mainly located on the edges of the plateau, whereas alpine grasslands in the hinterlands of the plateau showed a low vulnerability. This spatial pattern of alpine grassland vulnerability was controlled by climatic exposure, and grassland sensitivity and resilience to climate change might also exacerbate or alleviate the degree of vulnerability. Climate change had variable impacts on different grassland types. Desert steppes were more vulnerable to climate change than alpine meadows and alpine steppes because of the high variability in environmental factors and their low ability to recover from perturbations. Our findings also confirm that grazing intensity, a quantitative index of the most important human disturbance on alpine grasslands in this plateau, was significantly correlated with ecosystem vulnerability. Moderate grazing intensity was of benefit for increasing grassland resilience and then subsequently reducing grassland vulnerability. Thus, this study suggests that future assessments of ecosystem vulnerability should not ignore anthropogenic disturbances, which might benefit environmental protection and sustainable management of grasslands on the Qinghai-Tibetan Plateau.

SUBMITTER: Li M

PROVIDER: S-EPMC7007972 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Background and Aims:There is no knowledge of winter plant phenology and its controlling factors on the Qinghai-Tibetan Plateau (QTP). Thus, we conducted a 4 year winter phenology and growth dynamics study in the alpine meadow on the eastern QTP. Methods:From November 2013 to March 2017, the phenology of the 'winter-growth' and 'winter-green' species was recorded every 5 d. In November-February from 2014 to 2015, the above-ground biomass (AGB) in random plots was calculated to distinguish different growth patterns among winter growing species. The percentage of winter abundance relative to the summer population for forbs and the percentage of absolute coverage for grasses (W/S) were calculated to describe the importance of the winter population to the summer population. The soil moisture (SM) and soil temperature (ST) were used to explore the controlling factors on the AGB. Pearson's correlation analysis between winter phenology data and environmental variables, including air temperature (Tair), snow cover fraction (SCF), SM and ST, was used to investigate the factors affecting winter phenology during November-February from 2014 to 2017. Key Results:There were 107 species in total in the sites, including ten 'winter-growth' species and four 'winter-green' species. Among the 'winter-green' species, Festuca ovina and Deschampsia cespitosa were the dominant species in the sites. The 'winter-growth' species grew new leaves or ramets or transitioned to reproductive growth. Gentiana spathulifolia even flowered in winter. 'Winter-growth' made important contributions to the annual AGB, e.g. winter growth of G. spathulifolia accounted for 23.26 % of its annual AGB, while 14.74 % of the annual AGB of G. crassuloides was from winter growth. In addition, winter warming and snowfall reduction under global climate change on the eastern QTP may decrease the AGB increment of the 'winter-growth' and delay the green-up onset date of 'winter-green' species. Also, winter warming and snowfall reduction may advance the first flowering date of 'winter-growth' species. Conclusions:In contrast to previous views that plants on the QTP were generally considered to remain dormant in winter, our study revealed that alpine meadow plants had strong winter growth which suggested the importance of re-evaluating the dynamics of ecosystem function of alpine meadow, including its contribution to the global carbon balance. It was also shown that soil moisture availability is more important than warmer temperature in controlling the green-up onset of 'winter-green' species on the eastern QTP, which contrasts with the traditional view that warmer winters could advance green-up. As snowmelt is the only source of soil water in winter, the prediction of the green-up trend may be further complicated by snowfall variation in winter.

Project description:BACKGROUND: GeoChip 3.0, a microbial functional gene array, containing ~28,000 oligonucleotide probes and targeting ~57,000 sequences from 292 functional gene families, provided a powerful tool for researching microbial community structure in natural environments. The alpine meadow is a dominant plant community in the Qinghai-Tibetan plateau, hence it is important to profile the unique geographical flora and assess the response of the microbial communities to environmental variables. In this study, Geochip 3.0 was employed to understand the microbial functional gene diversity and structure, and metabolic potential and the major environmental factors in shaping microbial communities structure of alpine meadow soil in Qinghai-Tibetan Plateau. RESULTS: A total of 6143 microbial functional genes involved in carbon degradation, carbon fixation, methane oxidation and production, nitrogen cycling, phosphorus utilization, sulphur cycling, organic remediation, metal resistance, energy process and other category were detected in six soil samples and high diversity was observed. Interestingly, most of the detected genes associated with carbon degradation were derived from cultivated organisms. To identify major environmental factors in shaping microbial communities, Mantel test and CCA Statistical analyses were performed. The results indicated that altitude, C/N, pH and soil organic carbon were significantly (P < 0.05) correlated with the microbial functional structure and a total of 80.97% of the variation was significantly explained by altitude, C/N and pH. The C/N contributed 38.2% to microbial functional gene variation, which is in accordance with the hierarchical clustering of overall microbial functional genes. CONCLUSIONS: High overall functional genes and phylogenetic diversity of the alpine meadow soil microbial communities existed in the Qinghai-Tibetan Plateau. Most of the genes involved in carbon degradation were derived from characterized microbial groups. Microbial composition and structures variation were significantly impacted by local environmental conditions, and soil C/N is the most important factor to impact the microbial structure in alpine meadow in Qinghai-Tibetan plateau.

Project description:Alpine meadow ecosystems are susceptible to climate changes. Still, climate impact on cuticular wax in alpine meadow plants is poorly understood. Assessing the variations of cuticular wax in alpine meadow plants across different latitudes might be useful for predicting how they may respond to climate change. We studied nine alpine meadows in a climate gradient in the east side of Qinghai-Tibetan Plateau, with mean annual temperature ranging from -7.7 to 3.2°C. In total, 42 plant species were analyzed for cuticular wax, averaged 16 plant species in each meadow. Only four plant species could be observed in all sampling meadows, including Kobresia humilis,Potentilla nivea,Anaphalis lacteal, and Leontopodium nanum. The amounts of wax compositions and total cuticular wax in the four plant species varied among sampling meadows, but no significant correlation could be observed between them and temperature, precipitation, and aridity index based on plant species level. To analyze the variations of cuticular wax on community level, we averaged the amounts of n-alkanes, aliphatic acids, primary alcohols, and total cuticular wax across all investigated plant species in each sampling site. The mean annual temperature, mean temperature in July, and aridity index were significantly correlated with the averaged amounts of wax compositions and total cuticular wax. The average chain length of n-alkanes in both plant and soil linearly increased with increased temperature, whereas reduced with increased aridity index. No significant correlation could be observed between mean annual precipitation and mean precipitation from June to August and the cuticular wax amounts and average chain length. Our results suggest that the survival of some alpine plants in specific environments might be depended on their abilities in adjusting wax deposition on plant leaves, and the alpine meadow plants as a whole respond to climate change, benefiting the stability of alpine meadow ecosystem.

Project description:BACKGROUND:Tibetan sheep (TS) and Gansu Alpine Finewool sheep (GS) are both important plateau sheep raised and fed on the harsh Qinghai-Tibetan Plateau, China. Rumen methanogen and protozoal communities of plateau sheep are affected by their hosts and living environments, and play important roles in ruminant nutrition and greenhouse gas production. However, the characteristics, differences, and associations of these communities remain largely uncharacterized. RESULTS:The rumen methanogen and protozoal communities of plateau sheep were investigated by 16S/18S rRNA gene clone libraries. The predominant methanogen order in both sheep species was Methanobacteriales followed by Methanomassiliicoccales, which is consistent with those seen in global ruminants. However, the most dominant species was Methanobrevibacter millerae rather than Methanobrevibacter gottschalkii seen in most ruminants. Compared with GS and other ruminants, TS have more exclusive operational taxonomic units and a lower proportion (64.5%) of Methanobrevibacter. The protozoa were divided into Entodiniomorphida and Vestibuliferida, including nine genera and 15 species. The proportion of holotrich protozoa was much lower (1.1%) in TS than ordinary sheep. The most predominant genus was Entodinium (70.0%) in TS and Enoploplastron (48.8%) in GS, while the most common species was Entodinium furca monolobum (43.9%) and Enoploplastron triloricatum (45.0%) in TS and GS, respectively; Entodinium longinucleatum (22.8%) was only observed in TS. LIBSHUFF analysis indicated that the methanogen communities of TS were significantly different from those of GS, but no significant differences were found in protozoal communities. CONCLUSION:Plateau sheep have coevolved with unique rumen methanogen and protozoal communities to adapt to harsh plateau environments. Moreover, the host appears to have a greater influence on rumen methanogen communities than on rumen protozoal communities. The observed associations of methanogens and protozoa, together with the findings of previous studies on methane emissions from ruminant livestock, revealed that the lower proportion of Methanobrevibacter and holotrich protozoa may be responsible for the lower methane emission of TS. These findings facilitate our understanding of the rumen microbial ecosystem in plateau sheep, and could help the development of new strategies to manipulate rumen microbes to improve productivity and reduce the emission of greenhouse gases.

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Assessment of the vulnerability of alpine grasslands on the Qinghai-Tibetan Plateau.

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