Dataset Information

Temperature-mediated responses of carbon fluxes to precipitation variabilities in an alpine meadow ecosystem on the Tibetan Plateau.

ABSTRACT: Effects of climate warming and changing precipitation on ecosystem carbon fluxes have been intensively studied. However, how they co-regulate carbon fluxes is still elusive for some understudied ecosystems. To fill the gap, we examined net ecosystem productivity (NEP), gross ecosystem productivity (GEP,) and ecosystem respiration (ER) responses to multilevel of temperature increments (control, warming 1, warming 2, warming 3, warming 4) in three contrasting hydrological growing seasons in a typical semiarid alpine meadow. We found that carbon fluxes responded to precipitation variations more strongly in low-level warming treatments than in high-level ones. The distinct responses were attributable to different soil water conditions and community composition under low-level and high-level warming during the three growing seasons. In addition, carbon fluxes were much more sensitive to decreased than to increased precipitation in low-level warming treatments, but not in high-level ones. At a regional scale, this negative asymmetry was further corroborated. This study reveals that future precipitation changes, particularly decreased precipitation would induce significant change in carbon fluxes, and the effect magnitude is regulated by climate warming size.

SUBMITTER: Chen N

PROVIDER: S-EPMC6706212 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature

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Temperature-mediated responses of carbon fluxes to precipitation variabilities in an alpine meadow ecosystem on the Tibetan Plateau.

Chen Ning N Zhang Yangjian Y Zhu Juntao J Zu Jiaxing J Huang Ke K Li Junxiang J Liu Yaojie Y Cong Nan N Tang Ze Z Wang Li L Zhu Yixuan Y

Ecology and evolution 20190723 16

Effects of climate warming and changing precipitation on ecosystem carbon fluxes have been intensively studied. However, how they co-regulate carbon fluxes is still elusive for some understudied ecosystems. To fill the gap, we examined net ecosystem productivity (NEP), gross ecosystem productivity (GEP,) and ecosystem respiration (ER) responses to multilevel of temperature increments (control, warming 1, warming 2, warming 3, warming 4) in three contrasting hydrological growing seasons in a typi ...[more]

PMID: 31462999

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Project description:Alpine meadow plays vital roles in regional animal husbandry and the ecological environment. However, different grassland managements affect the structure and function of the alpine meadow. In this study, we selected three typical grassland managements including free grazing, enclosure, and artificial grass planting and conducted a field survey to study the effects of grassland managements on carbon fluxes in an alpine meadow. The carbon fluxes were observed by static chamber and environmental factors including vegetation and soil characteristics were measured simultaneously. Our results show that the alpine meadow was a CO2 and CH4 sink, and grassland managements had a significant effect on all CO2 fluxes, including gross ecosystem production (GEP, P< 0.001), net ecosystem production (NEP, P< 0.001) and ecosystem respiration (ER, P< 0.001) but had no significant effect on CH4 fluxes (P > 0.05). The ranking of GEP under the different grassland managements was enclosure > free grazing > artificial grass planting. Furthermore, NEP and ER at enclosure plots were significantly higher than those of the free grazing and artificial grass planting plots. In addition, different grassland managements also affected the vegetation and soil characteristics of the alpine meadow. The aboveground biomass of artificial grass planting was significantly higher than that of the free grazing and enclosure plots. The vegetation coverage under three different grassland managements was ranked in the order of enclosure > artificial grass planting > free grazing and significant differences were observed among them. Moreover, significant differences in the number of species (P< 0.01) and the Margalef richness index (P< 0.05) were detected under three different grassland managements. Further analysis of the relationship between environmental factors and carbon fluxes revealed that GEP and NEP of the alpine meadow were positively correlated with vegetation coverage, the number of species, and the Margalef richness index. Therefore, grassland restoration should be configured with multiple species, which could improve carbon sink capacity while considering the functions of grassland restoration and production.

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:BackgroundThe degradation of alpine meadows has induced substantial losses of soil organic carbon (SOC) on the Tibetan Plateau. A commonly-used method for rehabilitating degraded alpine meadows in this region is establishing cultivated grasslands through sowing seed mixtures, but its impact on the biochemical stability of SOC has remained inadequately explored.MethodsIn this study, a total of 20 composited 0-20 cm soil samples were collected from a heavily degraded alpine meadow (DM) and three adjacent cultivated grasslands established for 3 years (CG3), 12 years (CG12), and 17 years (CG17) on the eastern Tibetan Plateau, and the SOC pool was separated into labile C pool I (LOC I), labile C pool II (LOC II), and recalcitrant C pool (ROC) in order to investigate changes in contents of SOC fractions that have different biochemical stabilities after the establishment of cultivated grassland.ResultsAlthough the establishment of cultivated grasslands led to increases in soil total organic C content, the increase was only significant in samples with 17 years of cultivation. We found that the contents of the three SOC fractions were higher at CG3 and CG12 compared with those in the DM, and the differences were only significant for soil LOC II. By comparison, 17 years of cultivation led to significant increases in all of the SOC fraction contents. The results implied that different cultivation years had distinct impacts on SOC fractions in cultivated grasslands, and longer cultivation years contributed to accumulated soil ROC. The recalcitrance index of SOC in the DM was higher than that at CG3 and CG12, but lower than that at CG17. This was possibly due to the generally low litter quality of cultivated grasslands, which led to a slow release of complex compounds to soils. Moreover, it was observed that soil C:N ratio was a potential indicator of SOC biochemical stability because of their close correlation.ConclusionsOur findings suggest that the long-term establishment of cultivated grasslands on DM is a promising solution to recovering both the quantity and stability of SOC on the Tibetan Plateau.

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.

Dataset Information

Temperature-mediated responses of carbon fluxes to precipitation variabilities in an alpine meadow ecosystem on the Tibetan Plateau.

Publications

Temperature-mediated responses of carbon fluxes to precipitation variabilities in an alpine meadow ecosystem on the Tibetan Plateau.

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