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Changes in climate have caused impacts on ecosystems on all continents scale, and climate change is also projected to be a stressor on most ecosystems even at the rate of low- to medium-range warming scenarios. Alpine ecosystem in the Qinghai-Tibetan Plateau is vulnerable to climate change. To quantify the climate change impacts on alpine ecosystems, we simulated the vegetation distribution and net primary production in the Qinghai-Tibetan Plateau for three future periods (2020s, 2050s and 2080s) using climate projection for RCPs (Representative Concentration Pathways) RCP4.5 and RCP8.5 scenarios. The modified Lund-Potsdam-Jena Dynamic Global Vegetation Model (LPJ model) was parameter and test to make it applicable to the Qinghai-Tibetan Plateau. Climate projections that were applied to LPJ model in the Qinghai-Tibetan Plateau showed trends toward warmer and wetter conditions. Results based on climate projections indicated changes from 1.3 °C to 4.2 °C in annual temperature and changes from 2% to 5% in annual precipitation. The main impacts on vegetation distribution was increase in the area of forests and shrubs, decrease in alpine meadows which mainly replaced by shrubs which dominated the eastern plateau, and expanding in alpine steppes to the northwest dominated the western and northern plateau. The NPP was projected to increase by 79% and 134% under the RCP4.5 and RCP8.5. The projected NPP generally increased about 200 g C·m − 2 ·yr − 1 in most parts of the plateau with a gradual increase from the eastern to the western region of the Qinghai-Tibetan Plateau at the end of this century. [ABSTRACT FROM AUTHOR]

Alpine ecosystems are known to be sensitive to climate change and human disturbances. However, the knowledge about the changes of their underground microbial communities is inadequate. We explored the diversity and structure of soil bacterial and fungal communities using Ilumina MiSeq sequencing in native alpine grasslands (i.e. the alpine meadow, alpine steppe) and cultivated grassland of the Qinghai-Tibetan Plateau (QTP) under three-year treatments of overgrazing, warming and enhanced rainfall. Enhanced rainfall rather than warming significantly reduced soil microbial diversity in native alpine grasslands. Variable warming significantly reduced it in the cultivated grassland. Over 20% and 40% variations of microbial diversity could be explained by soil nutrients and moisture in the alpine meadow and cultivated grassland, separately. Soil microbial communities could be clustered into different groups according to different treatments in the alpine meadow and cultivated grassland. For the alpine steppe, with the lowest soil nutrients and moistures, < 10% variations of microbial diversity was explained by soil properties; and the soil microbial communities among different treatments were similar. The soil microbial community in the cultivated grassland was varied from it in native grasslands. Over 50% variations of soil microbial communities among different treatments were explained by soil nutrients and moisture in each grassland type. Our results suggest that climate change and human activities strongly affected soil microbial communities by changing soil nutrients and moistures in alpine grassland ecosystems. [ABSTRACT FROM AUTHOR]

To evaluate long-term effect of biochar application on yield-scaled greenhouse gas emissions (YSGE) in a paddy rice cropping system, a 4-year field experiment by static chamber - gas chromatograph method was conducted in South China. Principal component analysis and terminal restriction fragment length polymorphism (T-RFLP) and real-time qPCR was used to unravel the microbial mechanisms of biochar addition. Six treatments were included: control (CK), application of 5 t ha − 1 biochar (BC1), application of 10 t ha − 1 biochar (BC2), application of 10 t ha − 1 biochar (BC3), rice straw return at 2400 kg ha − 1 (RS) and inoculated rice straw return at 2400 kg ha − 1 (RI). The results indicated that biochar amendment significantly decreased methane (CH 4 ) and gross greenhouse gas (GHG) emissions. This may primarily be ascribed to the stimulated biodiversity and abundance of methanotrophic microbes, increased soil pH and improved aeration by reducing bulk density after biochar incorporation. Compared with CK, RS and RI, 26.18%, 70.02%, 66.47% of CH 4 flux and 26.14%, 70.16%, 66.46% of gross GHG emissions were reduced by biochar (mean of three biochar treatments), respectively. Furthermore, biochar significantly increased harvest index of double rice production ( p < 0.05). In comparison with CK, RS and RI, 29.14%, 68.04%, 62.28% of YSGE was reduced by biochar, respectively, and the highest biochar addition rate (20 t ha − 1 ) contributed most to the mitigation of GHG emissions (36.24% decrease compared to CK) and improvement of rice yield (7.65% increase compared to CK). Results of our study suggested that long-term application of biochar should be the potential way to mitigate GHGs emissions and simultaneously improve rice productivity in the paddy rice system. [ABSTRACT FROM AUTHOR]

Nitrogen (N) deposition-induced N input in alpine meadow soils may affect the soil exchange of methane (CH 4) with the atmosphere. The quantities and spatiotemporal variation in CH 4 uptake remain largely unknown for this ecosystem on a global scale. Previous studies regarding CH 4 flux have mainly focused on the growing season in alpine meadows. Thus, the impact of N deposition on the non-growing season uptake of CH 4 is unknown. In this study, we investigated the effects of N deposition on CH 4 uptake during both the growing and non-growing seasons in an alpine meadow on the central Qinghai-Tibet Plateau (QTP). The CH 4 fluxes were measured using static chambers and gas chromatography in four N deposition treatment areas (Control; N7, 7 kg N ha−1 yr−1; N20, 20 kg N ha−1 yr−1; N40, 40 kg N ha−1 yr−1) from May 2015 to August 2018. Our results showed that alpine meadow soils acted as CH 4 sinks throughout the year. N deposition significantly decreased CH 4 uptake fluxes (P < 0.05) and the annual mean CH 4 uptake fluxes declined at N deposition levels of 7, 20, and 40 kg N ha−1 yr−1 by 12.3%, 14.4%, and 20.5%, respectively, compared with that of the control. Annual CH 4 uptake was significantly correlated with total annual precipitation, mean annual air temperature, and N deposition rate. Annual cumulative CH 4 uptake in the four treatments across 3 years was 75.1 mg C m−2, where approximately 40% of the total annual CH 4 uptake occurred during the non-growing season. Our results showed that CH 4 uptake in the non-growing season cannot be ignored when estimating annual uptake of CH 4 because of the large CH 4 uptake during the non-growing season in the alpine meadow on the QTP under N deposition conditions. Contribution of different seasons to the annual cumulative CH 4 uptake in an alpine meadow on the Qinghai-Tibet Plateau. N7, N20, and N40 represent 7, 20, and 40 kg N ha−1 yr−1 nitrogen deposition, respectively. GSC = growing seasonal cumulative CH 4 uptake, NGSC = non-growing seasonal cumulative CH 4 uptake, AC = annual cumulative CH 4 uptake. Unlabelled Image • We investigated effects of N deposition on CH4 uptake in an alpine meadow on QTP. • N deposition significantly decreased CH4 uptake. • CH4 uptake in non-growing season accounted for about 40% of annual CH4 uptake. • CH 4 uptake was regulated by precipitation, air temperature and N deposition rate. [ABSTRACT FROM AUTHOR]

River networks in subtropical agricultural hilly region become an inconvenient greenhouse gas (GHG, methane and nitrous oxide) source because of the influence of human activities, which has caused large uncertainties for refinement of national GHG inventories and their global budget. Based on field monitoring experiments at high temporal resolution, we employed regression tree and importance analysis to identify quantitatively factors that influence the diffusive flux of GHGs to provide a scientific basis for reducing GHG emissions and controlling regional carbon and nitrogen losses. The results indicate that significant spatiotemporal variation of methane (CH 4) nitrous oxide (N 2 O) diffusion occurs in all the four reaches (W1, W2, W3 and W4) of Tuojia river networks. Among them, W1 contributed lowest CH 4 (22.55 μg C m−2 h−1) and N 2 O (5.00 μg N m−2 h−1) diffusive flux than the other three (P < 0.05), while W4 offered highest CH 4 (166.15 μg C m−2 h−1) and N 2 O (30.47 μg N m−2 h−1) diffusive flux but with no statistically significant difference between W2 and W3 due to homogeneous extraneous nutrition loading into the two reaches. W4 also contributed largest cumulative flux of CH 4 (14.55 kg C ha−1 yr−1) and N 2 O (2.69 kg N ha−1 yr−1) in Tuojia River networks (P < 0.05). Furthermore, the regression tree and importance analysis indicate that, in the anaerobic environment, dissolved oxygen saturation controlled the production and diffusion for both CH 4 and N 2 O. The findings of this investigation highlighted that decision support tools provide an effective pathway to enhance the GHG mitigation technology research in agroecosystems and simultaneously shed light on the global campaign on refinement of national GHG inventories as well as regional nutrient management. Unlabelled Image • Higher reach of Tuojia River contributes more GHG diffusive flux. • There is significant impact of farming and living activities on behavior of GHGs transfer. • RTA revealed saturation of dissolved oxygen as most influential factor of GHG diffusion. [ABSTRACT FROM AUTHOR]

Climate change and anthropogenic activities have resulted in increased atmospheric methane (CH 4) concentration. Increased nitrogen deposition and precipitation accompanies climate warming and can change soil carbon and nitrogen dynamics and microbial processes and alter CH 4 fluxes. To quantify the sink of the vast alpine meadows of the Tibetan Plateau and to examine how precipitation addition (P), warming (W), and nitrogen addition (N) affect CH 4 fluxes in alpine meadows, we conducted continuous 3-growing season experiments in an alpine meadow using the static chamber and gas chromatograph method. Soil CH 4 samples were collected during the early, peak, and late stages of the growing season from 2015 to 2017. Our results suggested that neither P, W, nor N had an interaction effect on soil CH 4 uptake. P significantly increased and decreased the copies number of particulate methane monooxygenase alpha subunit (pmoA) and methyl-coenzyme M reductase alpha subunit (mcrA), respectively. However, P significantly decreased CH 4 uptake, particularly under the combined treatment of P and N. Compared with the control, CH 4 uptake decreased under P, N, PW, and PN by 50.64%, 6.24%, 39.37%, and 75.06%, respectively, whereas under W and WN CH 4 uptake increased by 16.19% and 7.56%, respectively. Soil CH 4 uptake was positively correlated with soil temperature and pmoA and negatively correlated with soil moisture and NH 4 +-N content. CH 4 uptake was significantly affected by the sampling period. CH 4 uptake was significantly lower rates during peak growing season compared with those during the early and late stages of the growing season. Our results suggest that, (1) CH 4 fluxes of alpine grassland ecosystems are more sensitive to P than W or N, and (2) precipitation controls CH 4 flux response to increasing nitrogen deposition in alpine meadows on the Tibetan Plateau. Therefore, future research should focus on the response and feedback of CH 4 uptake to changes in precipitation. Unlabelled Image • Neither nitrogen addition nor warming significantly affected CH 4 uptake in the alpine meadows. • Increased precipitation significantly decreased CH 4 uptake, particularly under the combined treatment of P and N. • CH 4 uptake in the alpine meadows was most significantly affected by changes in precipitation. [ABSTRACT FROM AUTHOR]