With a pace of about twice the observed rate of global warming, the temperature on the Qinghai-Tibetan Plateau (Earth's third pole') has increased by 0.2 degrees C per decade over the past 50years, which results in significant permafrost thawing and glacier retreat. Our review suggested that warming enhanced net primary production and soil respiration, decreased methane (CH4) emissions from wetlands and increased CH4 consumption of meadows, but might increase CH4 emissions from lakes. Warming-induced permafrost thawing and glaciers melting would also result in substantial emission of old carbon dioxide (CO2) and CH4. Nitrous oxide (N2O) emission was not stimulated by warming itself, but might be slightly enhanced by wetting. However, there are many uncertainties in such biogeochemical cycles under climate change. Human activities (e.g. grazing, land cover changes) further modified the biogeochemical cycles and amplified such uncertainties on the plateau. If the projected warming and wetting continues, the future biogeochemical cycles will be more complicated. So facing research in this field is an ongoing challenge of integrating field observations with process-based ecosystem models to predict the impacts of future climate change and human activities at various temporal and spatial scales. To reduce the uncertainties and to improve the precision of the predictions of the impacts of climate change and human activities on biogeochemical cycles, efforts should focus on conducting more field observation studies, integrating data within improved models, and developing new knowledge about coupling among carbon, nitrogen, and phosphorus biogeochemical cycles as well as about the role of microbes in these cycles.

The impacts of climate change and human activities on biogeochemical cycles on the Qinghai-Tibetan Plateau

Climate-smart agriculture: sourcebook.

There is a great resurgence of interest all over the world in the development of ‘small’ hydropower systems (SHS). The surge is essentially propelled by the belief that SHS, which include mini, micro, and picahydel systems, are a source of clean energy with little or no adverse impacts on the environment. This paper presents an overview of SHS and then examines in detail whether the prevalent belief in the great environment-friendliness of SHS is really justified. It is brought out that widespread use of SHS is likely to cause, per kilowatt of power generated, no less significantly adverse environmental impacts than large hydropower systems and some other conventional sources of energy. While supporting the ongoing global efforts to maximize the use of SHS, the authors advocate much greater circumspection than is being exercised at present vis-a-vis SHS. The authors believe that if the likely pitfalls are foreseen before SHS are put to widespread use, and remedial measures taken accordingly, it may save the world from considerable disillusionment and environmental damage.

Small hydro and the environmental implications of its extensive utilization

Sources of methane (CH4) become highly variable for countries undergoing a heightened period of development due to both human activity and climate change. An urgent need therefore exists to budget key sources of CH4, such as wetlands (rice paddies and natural wetlands) and lakes (including reservoirs and ponds), which are sensitive to these changes. For this study, references in relation to CH4 emissions from rice paddies, natural wetlands, and lakes in China were first reviewed and then reestimated based on the review itself. Total emissions from the three CH4 sources were 11.25 Tg CH4 yr � 1 (ranging from 7.98 to 15.16 Tg CH4 yr � 1 ). Among the emissions, 8.11 Tg CH4 yr � 1 (ranging from 5.20 to 11.36 Tg CH4 yr � 1 ) derived from rice paddies, 2.69 Tg CH4 yr � 1 (ranging from 2.46 to 3.20 Tg CH4 yr � 1 ) from natural wetlands, and 0.46 Tg CH4 yr � 1 (ranging from 0.33 to 0.59 Tg CH4 yr � 1 ) from lakes (including reservoirs and ponds). Plentiful water and warm conditions, as well as its large rice paddy area make rice paddies in southeastern China the greatest overall source of CH4, accounting for approximately 55% of total paddy emissions. Natural wetland estimates were slightly higher than the other estimates owing to the higher CH4 emissions recorded within Qinghai-Tibetan Plateau peatlands. Total CH4 emissions from lakes were estimated for the first time by this study, with three quarters from the littoral zone and one quarter from lake surfaces. Rice paddies, natural wetlands, and lakes are not constant sources of CH4, but decreasing ones influenced by anthropogenic activity and climate change. A new progress-based model used in conjunction with more observations through model-data fusion approach could help obtain better estimates and insights with regard to CH4 emissions deriving from wetlands and lakes in China.

Methane emissions from rice paddies natural wetlands, lakes in China: synthesis new estimate

Zoige wetland of Tibetan plateau is characterized by being located at a low latitude (33 degrees 56'N, 102 degrees 52'E) region and under the annual temperature around 1 degrees C. Previous studies indicated that Zoige wetland was one of the CH(4) emission centres in Qinghai-Tibetan plateau; in this study, the methanogen community in this low-latitude wetland was analysed based on the homology of 16S rRNA and mcrA genes retrieved from the soil. The results indicated that members of Methanosarcinales and Methanomicrobiales constituted the majority of methanogens, and a novel uncultured methanogen cluster, Zoige cluster I (ZC-I) affiliated to Methanosarcinales, could be dominant. Using quantitative polymerase chain reaction (qPCR) assay, ZC-I methanogens were estimated to be 10(7) cells per gram of soil, accounting for about 30% of the total Archeae. By combining culturable enrichment with qPCR assay, the quantity of ZC-I methanogens in the methanogenic enrichment with acetate, H2/CO(2), methanol or trimethylamine was determined to increase to 10(8) cells ml(-1), but not with formate, which indicated that ZC-I methanogens could use the four methanogenic substrates. The growth rates at 30 degrees C and 15 degrees C were not pronounced different, implying ZC-I to be the cold-adaptive methanogens. The broad substrate spectrum identified the ZC-I methanogens to be a member of Methanosarcinaceae, and could represent a novel sub-branch specifically inhabited in cold ecosystems. Fluorescence in situ hybridization (FISH) images also visualized ZC-I methanogens the sarcina-like aggregate of the spherical cells. The prevalence and flexibility in substrate utilization and growth temperature suggested ZC-I methanogens to be an important player in the methanogenesis of Zoige wetland.

http://www.im.ac.cn/UserFiles/File/2008/200808/Environmental%20Microbiology-1850-dongxz.pdf

Methanogen community in Zoige wetland of Tibetan plateau and phenotypic characterization of a dominant uncultured methanogen cluster ZC-I.

To understand the seasonality of methane flux from alpine wetlands in Zoige Plateau, 30 plots were set to measure the methane emissions in the growing and nongrowing seasons in three environmental types: dry hummock (DH), Carex muliensis (CM), and Eleocharis valleculosa (EV) sites. There were clearly seasonal patterns of methane flux in different environmental types in the growing and nongrowing seasons. Mean methane emission rate was 14.45 mg CH4 m(-2) h(-1) (0.17 to 86.78 mg CH4 m(-2) h(-1)) in the growing season, and 0.556 mg CH4 m(-2) h(-1) (0.002 to 6.722 mg CH4 m(-2) h(-1)) in the nongrowing season. In the growing season, the main maximum values of methane flux were found in July and August, except for a peak value in September in CM sites. In the nongrowing season, the similar seasonal variation pattern was shared among all the three sites, in which the methane emissions increased from February to April. In the growing season, the determining factors were surface temperatures (r(2) = 0.55, P < 0.05), standing water depths (r(2) = 0.32, P < 0.01) and plant community heights (r(2) = 0.61, P < 0.01), while in the nongrowing season, ice thickness (r(2) = 0.27, P < 0.05; in CM and EV sites) was found most related to flux. In our understanding, the seasonality of methane emissions in our study areas was temperature- and-plant-growth-dependent, and the water table position was also very important to shape the temperature- and-plant-growth-dependent seasonal variation of flux with its vigorous variations in alpine wetland ecosystems. Different environmental types within the wetland also influenced the seasonal pattern of methane flux. For an accurate estimate of the global methane source strength of alpine wetlands, the pronounced seasonal or even temporal variability in methane emission from alpine wetlands should be taken into consideration.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2006JD008072

Determinants influencing seasonal variations of methane emissions from alpine wetlands in Zoige Plateau and their implications

High methane emissions from a littoral zone on the Qinghai-Tibetan Plateau

Alpine wetland is a source for CH(4), but little is known about methane emission from such wetland, especially about its diurnal pattern. In this study we tried to probe the diurnal variation in methane emission from alpine wetland vegetation. The average methane emission rate was 9.6 +/- 3.4 mg CH(4) m (-aEuro parts per thousand 2) h (-aEuro parts per thousand 1). There was an apparent diurnal variation pattern in methane emission with one minor peak at 06:00 and a major one at 15:00. The sunrise peak was consistent with a two-way transport mechanism for plants (convective at daytime and diffusive at night-time). CH(4) emission was found significantly correlated with redox potentials. The afternoon peak could not be explained by diurnal variation in soil temperature, but could be attributable to changes in CH(4) oxidation and production driven by plant gas transport mechanism. The results have important implications for sampling and scaling strategies for estimating methane emission from alpine wetlands.

Diurnal variation of methane emissions from an alpine wetland on the eastern edge of Qinghai-Tibetan Plateau.

Alpine wetland is a source for methane (CH(4)), an important greenhouse gas, but little is known about how this habitat influences the emission. To understand this wetland habitats were selected at the altitude of 3430 m a.s.l. (in National Wetland Nature Reserve of Zoige, Quingle - Tibetan Plateau) and the methane flux was measured with static chambers in three different sites, including hollows with Carex muliensis Hand - Mazz. and Eleocharis valleculosa Ohwi f. setosa (Ohwi) Kitagawa., grass hummocks composed of Kobresia tibetica Maxim, Cremanthodium pleurocaule R. D. Good, Potentilla bifurca L. and Pedicularis sp. We have found that in alpine wetland these habitats significantly affect CH, emissions in the onset (April, 2006) and peak (August, 2005) stages of growing season. Hollows covered with Carex muliensis and Eleocharis valleculosa had higher values of emission than grass hummocks built by several grass species. Slight difference of CH(4) emission was found between two kinds of hollows with Carex muliensis and Eleocharis valleculosa. These results were consistent with the change of water table, which was found best correlated with CH(4) emissions (r(2) = 0.43, P <0.01) in the peak stage of growing season. Directly measured shoot biomass and plant heights were best related to CH(4) emissions (r(2) = 0.59, P <0.01). However, in the onset stage of growing season, variation of CH(4) emission may not be simply ascribed to changes in water table and vegetation structure.

Shouping Yao

Papers

Determinants influencing seasonal variations of methane emissions from alpine wetlands in Zoige Plateau and their implications

High methane emissions from a littoral zone on the Qinghai-Tibetan Plateau

Diurnal variation of methane emissions from an alpine wetland on the eastern edge of Qinghai-Tibetan Plateau.

The effect of habitat on methane emission from an alpine wetland.