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Recently, the Qinghai–Tibetan Plateau has experienced significant warming. Climate warming is expected to have profound effects on plant community productivity and composition, which can drive ecosystem structure and function. To explore effects of warming on plant community productivity and composition, we conducted a warming experiment using open top chambers (OTCs) from 2012 to 2014 in alpine meadow and alpine steppe habitat on the central Qinghai–Tibetan Plateau. We measured aboveground net primary productivity (ANPP), community composition and species diversity under ambient and two levels of artificially warmed conditions across three years. Our results showed that warming significantly stimulated plant growth in the alpine meadow, but reduced growth on the alpine steppe. The increase of ANPP in alpine meadow was a result of an increase of plant height under warming. Warming-induced drought conditions were primarily responsible for the observed decrease of ANPP in an alpine steppe. Plant community composition and species diversity were not influenced by warming in alpine meadow. Alternatively, in alpine steppe, cover of graminoids and forbs significantly declined while legumes substantially increased under warming, subsequently resulting in rapid species losses. Changes in soil moisture were responsible for observed changes in graminoids and legumes in the alpine steppe. Overall, experimental results demonstrated that warming had a positive impact on plant community structure and function in alpine meadow and had a negative impact on these characteristics in an alpine steppe. This work highlights the important role of soil moisture for regulating plant productivity and community composition response to warming in the alpine steppe. In particular, the deep-rooted, drought resistant plants may increase in a warmer future in the central Qinghai–Tibetan Plateau. These changes may reduce habitat quality for the local community of grazers because many of the species that increased are also unpalatable to grazers. [ABSTRACT FROM AUTHOR]

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]

Abstract: The semi-arid loess hilly–gully region in China has an extremely vulnerable ecological environment. Inappropriate land use — crop farming, overgrazing, and plantation forestry - has worsened soil erosion, intensified water shortage, and hence impeded the ecological conservation and agricultural development of the entire region in the past. Optimizing land use and vegetation cover and spatial pattern is conducive to achieving both ecological and economic goals in terms of controlling soil erosion, using water resources rationally and raising agricultural productivity. Changchuan Watershed, a typical small catchment in the semi-arid loess hilly region, was selected as the case study area to analyze the impacts of land use and land cover structure and associated spatial pattern on soil erosion and water consumption in the Watershed, through field investigation and model simulation. Land use structure was optimized by multi-objective programming, using remote sensing (RS) and geographical information system (GIS) techniques, analytic hierarchical programming (AHP) and expert consultancy. The digitized optimum spatial pattern embodying rationally-proportioned land use structure was obtained through GIS-aided redistribution of land use types. The optimized land use structure re-apportioned woodlands, shrublands, grasslands, and croplands at 3.7%, 38.6%, 49.4%, and 6.3% of the land area respectively, compared to the current land use structure of 2.4%, 38.6%, 24.0%, and 12.6%, respectively, in the Changchuan Watershed. In the optimized land use spatial pattern, croplands are mainly located in the riverside plain and check-dammed valleys and grasslands are widely distributed in the lower reaches of the basin, while shrublands are appropriately established in the middle and upper reaches of the river. A comparative analysis shows that the optimized land use structure, with well-designed spatial pattern is able to reduce soil erosion, enhance the utilization of water resources and raise agricultural productivity. [Copyright &y& Elsevier]

[Display omitted] Structural information of grassland changes on the Tibetan Plateau is essential for understanding alterations in critical ecosystem functioning and their underlying drivers that may reflect environmental changes. However, such information at the regional scale is still lacking due to methodological limitations. Beyond remote sensing indicators only recognizing vegetation productivity, we utilized multivariate data fusion and deep learning to characterize formation-based plant community structure in alpine grasslands at the regional scale of the Tibetan Plateau for the first time and compared it with the earlier version of Vegetation Map of China for historical changes. Over the past 40 years, we revealed that (1) the proportion of alpine meadows in alpine grasslands increased from 50% to 69%, well-reflecting the warming and wetting trend; (2) dominances of Kobresia pygmaea and Stipa purpurea formations in alpine meadows and steppes were strengthened to 76% and 92%, respectively; (3) the climate factor mainly drove the distribution of Stipa purpurea formation, but not the recent distribution of Kobresia pygmaea formation that was likely shaped by human activities. Therefore, the underlying mechanisms of grassland changes over the past 40 years were considered to be formation dependent. Overall, the first exploration for structural information of plant community changes in this study not only provides a new perspective to understand drivers of grassland changes and their spatial heterogeneity at the regional scale of the Tibetan Plateau, but also innovates large-scale vegetation study paradigm. [ABSTRACT FROM AUTHOR]

• The relative abundance of soil rare biosphere was stable under climate changes. • The specific soil microbial taxa strongly related to soil rare biosphere. • The rare biosphere strongly explained variations of soil available nitrogen. Ecological roles of "rare biosphere" (RB) were rarely discussed in alpine grassland ecosystems. We explored the roles of RB and specific taxa of soil bacteria and fungi in regulating soil nutrients and aboveground biomass of an alpine meadow and alpine steppe under warming and enhanced rainfall scenarios on the Qinghai-Tibetan plateau. In the context of alpine meadow and alpine steppe, the relative abundance of bacterial RB was ∼40% in the bacterial community, and it was <10% for fungal RB in the fungal community. The relative abundance of the RB of soil bacteria and fungi were not changed by warming or enhanced rainfall. All specific bacterial taxa and over 90% specific fungal taxa belonged to the RB. The RB, including the most specific taxa, explained many more variations in the contents of soil NO 3 -N and NH 4 -N than the high abundant microbial species under warming and enhanced rainfall conditions. The aboveground biomass of the alpine meadow and steppe were strongly affected by the contents of soil NO 3 -N, available phosphorus and total nitrogen under the condition of warming and enhanced rainfall. Our findings suggest that the robust soil microbial RB plays an important role in regulating the content of soil available nitrogen, which could profoundly affect aboveground plant biomass of alpine grassland ecosystems under climate change conditions. [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]

The plateau pika ( Ochotona curzoniae ) is considered a keystone species on the Qinghai–Tibetan Plateau (QTP). Under a moderate burrow density condition, we investigated plant community and soil properties surrounding pika's burrows in comparison to the control sites (without pika's burrows) in an alpine meadow ecosystem. The results demonstrated that plant biomass, especially aboveground biomass around pika's burrow, was improved. The contents of available soil nutrients around the pika's burrow were improved as well. The highest aboveground biomass and highest contents of NH 4 -N, available phosphorus and available potassium was detected at the back of the burrow. The compositions of plant community were not changed significantly around the pika burrow, excluding at the front of the burrow. Our findings revealed that the activities of plateau pika can improve the production of alpine meadow and increase the soil fertility at individual burrow level when the burrow density was not out of control. [ABSTRACT FROM AUTHOR]

Warming and increased precipitation can affect soil respiration (SR) and plant community variation in grassland ecosystems. Dominant species have important impacts on maintaining grassland landscapes and ecosystem stability, promoting nutrient cycling, and carbon sequestration. However, the mechanisms by which warming and increased precipitation regulate SR through the replacement of dominant plant species remain largely unknown. Here, we conducted an 8-year (2011–2018) manipulative field experiment comprising warming and precipitation addition, as well as a pot experiment simulating different proportions of dominant species (Leymus chinensis and Stipa krylovii), to examine the changes in SR in a temperate steppe in Inner Mongolia, China. Our results indicate that increased precipitation significantly increased SR by 48.9 %, while warming had no significant effect on SR. Warming, increased precipitation, and their interaction did not affect the temperature sensitivity of SR. Warming and increased precipitation were found to increase the biomass of L. chinensis (a rhizomatous grass) and decrease the biomass of S. krylovii (a bunchgrass). SR was significantly positively correlated with community biomass and microbial biomass. Although the proportion of dominant species was not directly significantly correlated with SR, the proportion of dominant species can affect SR by regulating community biomass and subsequently affecting microbial biomass. The pot experiment also showed that community biomass is a key factor affecting SR. This study emphasizes the regulatory role of soil moisture and community biomass in SR. When evaluating the impacts of climate change scenarios on soil respiration and ecosystems, the potential effects of changes in the dominant species should be considered, especially in arid and semiarid regions. • Warming had no significant effect on soil respiration in temperate steppe. • Soil moisture and community biomass are key factors regulating soil respiration in temperate steppe. • Increasing precipitation has a cumulative effect on soil respiration over years. [ABSTRACT FROM AUTHOR]

Grazing exerts a significant influence on greenhouse gases (GHGs) fluxes within temperate grasslands. While previous studies have explored the impact of varying grazing intensities on GHGs fluxes in meadow steppe, typical steppe, and desert steppe, there remains a knowledge gap regarding how grazing intensities affect GHGs fluxes across different grassland types and seasonal variations. In this study, we conducted a meta-analysis of Inner Mongolia grasslands involving 38 published reports and aggregating 143, 160, and 118 records for the CO 2 , CH 4 , and N 2 O, respectively. Our results demonstrated that grazing reduced annual mean CO 2 emission, CH 4 uptake, and N 2 O emission by 15.29%, 10.56%, and 24.73%, respectively (P < 0.05). Specifically, during the freeze-thaw period, grazing induced a decrease of 28.06% and 58.41% in CH 4 uptake and N 2 O emissions, respectively, compared to ungrazed treatments (P < 0.05). Further dissecting the impact, we found that grazing reduced CO 2 emissions in desert steppe, typical steppe, and meadow steppe by 20.28%, 15.54%, and 11.79%, respectively. In addition, grazing decreased CH 4 uptake in typical steppe by 15.14% and decreased N 2 O emission in typical steppe, meadow steppe, and sown pasture by 20.25%, 24.18%, 52.91%, respectively. Crucially, the alteration in plant biomass due to grazing-induced changes underlying drivers that govern the responses of GHGs fluxes. These results furnish compelling evidence that grazing, particularly in non-growing season, holds the potential to mitigate grassland GHGs fluxes in temperate grasslands. Our results can deepen the understanding of the grazing effects on GHGs and offer valuable insights for refining grazing management strategies in pastoral regions. [ABSTRACT FROM AUTHOR]

• Warming and water addition increase L. chinensis biomass and reduce S. krylovii. • Community biomass is remained unchanged under warming and water addition. • Warming increases L. chinensis biomass by affecting SA and GA. • S. krylovii steppe may be replaced by L. chinensis in warmer and wetter future. Dominant species play a crucial role in regulating plant community structure and productivity. Climate change affects community productivity by changing plant traits and resource use efficiency. However, the response of the productivity of a dominant species to warming and precipitation addition and the related effects on community biomass production in semi-arid grasslands remain unclear. We conducted a ten-year warming and precipitation addition study of a semi-arid steppe in Inner Mongolia, China. We examined the responses of community composition, biomass production, and trait and resource use efficiency of two dominant species, Leymus chinensis (rhizome grass) and Stipa krylovii. The results show that warming and precipitation increased the biomass of L. chinensis and decreased the biomass of S. krylovii. Community biomass production was unchanged under warming and precipitation from the contrasting changes in the two dominant species. Warming significantly increased the leaf area (LA) of L. chinensis and S. krylovii compared to that in ambient conditions, while it decreased the specific leaf area (SLA) and δ13C of S. krylovii. Increases in temperature stimulated biomass production of L. chinensis by affecting salicylic acid (SA) and GA (gibberellin), and they increased its competitive ability compared with that of S. krylovii. Our results highlight the different responses of L. chinensis and S. krylovii to environmental changes, which stabilised community productivity under warming and precipitation. Our study provides evidence that S. krylovii may be replaced by L. chinensis in steppe climates in the warmer and wetter future. [ABSTRACT FROM AUTHOR]

Atmospheric concentrations of nitrous oxide (N 2 O) have increased over the last 150 years due to human activities. Soils are important source of N 2 O where its production is largely regulated by biological processes. Nitrogen (N) deposition can alter the processes of autotrophic nitrification and denitrification, thus affecting the rate and direction of the soil N 2 O exchange with the atmosphere. It is obvious that atmospheric N deposition has influenced a dry alpine meadow in the Qinghai–Tibetan Plateau (QTP). Therefore, we investigated the effects of N deposition on the annual N 2 O emissions in an alpine meadow of the QTP. The N 2 O flux was measured for 2 years using static chambers and gas chromatography methods at four treatments (N0, background level; N7, add 7 kg N ha −1  yr −1 ; N20, add 20 kg N ha −1  yr −1 ; N40, add 40 kg N ha −1  yr −1 ). We found that high N deposition increased the N 2 O flux, not only in the growing season but also in winter and the spring thaw period. The average annual N 2 O fluxes at N0 and N40 plots were 3.1 and 6.1 μg m −2  h −1 , respectively. Compared with N0, the average annual N 2 O fluxes increased at N7, N20, and N40 plots by 13.7%, 47.6%, and 98.7%, respectively, the N 2 O fluxes in N40 plots increased by 113.6%, 41.6%, and 78.7% during the growing season, winter and spring thaw period, respectively. The emission of N 2 O during the growing season, winter and spring thaw period accounted for 63.2%, 29.9% and 6.9% of annual total emission of N 2 O, respectively. The N 2 O flux correlated significantly with air temperature, soil temperature, soil water content, total nitrogen, total organic carbon, and soil NH 4 + –N content in the alpine meadow. [ABSTRACT FROM AUTHOR]

The combined impacts of modified nitrogen (N) fertilizers and water saving irrigation (WSI) on greenhouse gas (GHG) emissions and grain yield of rice paddies have not previously been documented. GHG emissions from rice paddies under modified N fertilizers and WSI deserve attention because water and N are being used extensively to attain higher grain yield. A field experiment was conducted to evaluate the influence of modified N fertilizers and WSI on methane (CH 4 ) and nitrous oxide (N 2 O) emissions and grain yield in rice paddies. Four treatments were applied: urea with conventional irrigation (U + CI), urea with shallow water depth with alternate wetting-drying water saving irrigation (U + SWD), polymer-coated controlled release urea with SWD (CRU + SWD), and nitrapyrin-urea composition plus hydroquinone with SWD (NU + HQ + SWD). Compared to U + CI, CH 4 emissions significantly decreased by 26% and 31%, and N 2 O emissions increased by 52% and 42% under U + SWD in the early and late rice growing seasons respectively (p < 0.05). Although SWD increased N 2 O emissions, total GHG emissions (T GHG ) reduced by 20% and 25% in the two rice seasons under U + SWD, and GHG emission intensity (GHGI) decreased by 24% on average. Modified N fertilizer applications also affected grain yield and GHG emissions under SWD. Compared with U + SWD, CRU + SWD and NU + HQ + SWD reduced CH 4 , N 2 O emissions and T GHG by 28–49%, 12–44% and 26–45%, respectively, while grain yield increased by 6–35%. Reduction in CH 4 emissions occurred because, compared to urea, CRU and NU + HQ can inhibit CH 4 production and transport by controlling development of invalid tillers, while their nitrogen release patterns were more favorable for CH 4 consumption. In summary, modified N fertilizers in combination with SWD are a win-win strategy to improve grain production while reducing GHG emissions in the rice cropping system. [ABSTRACT FROM AUTHOR]

Scaling up of farming operations by land use rights transfers has been a growing trend in China in recent years. However, little is known about the implications of this trend for greenhouse gas (GHG) emissions and soil organic carbon (SOC) stock changes. Using farm survey data from Shandong Province, a typical grain production region in China, we used a life cycle assessment (LCA) method to evaluate the impact of different farm scales on input use efficiency, grain production, SOC stock changes and GHG emissions. Large-scale farming operations (LSFO) enhanced input use efficiency by reducing fertilizer and pesticide consumption rates and energy use for irrigation. Compared with small household farming operations (SHFO), LSFO attained higher grain yield in wheat-maize and wheat-rice cropping systems. Compared with small farms, carbon footprints per unit area of large-scale farms were lower for wheat (17%) and maize (28%) in the wheat-maize cropping system and for wheat (14%) and rice (8%) in the wheat-rice cropping system. Moreover, LSFO reduced GHG emissions (7–21%) and enhanced SOC stocks (6–9%), compared with SHFO. This study highlights that in China, land use rights transfers to promote large-scale farming can help achieve cleaner grain production with less negative impact on the environment. [ABSTRACT FROM AUTHOR]

Microorganisms are the basis for sustaining ecosystem function and are extremely sensitive to global warming and altered precipitation. Nevertheless, the seasonal pattern of the microbial response to a coupled effect of warming and increased precipitation is largely unknown. We set up a six-year manipulative experiment to verify changes in microbial response to warming (approximately 2 °C), increased precipitation (20 %), and their interactive effect in a semiarid steppe in Inner Mongolia. We detected changes in microbial species richness, diversity, community structure, and microbial interactions during different periods of the growing season. The results suggest that warming and increased precipitation had a stronger impact on the microbial community in the early growing season than in the mid- and late growing seasons. In the early growing season, warming significantly decreased bacterial diversity, while increased precipitation did not significantly affect the microbial community. The interactive effect of increased precipitation and warming significantly increased bacterial richness but decreased fungal richness and amplified the dissimilarities among bacterial and fungal communities. Compared to the early growing season, less microbial taxa significantly responded to warming and increased precipitation in the mid- and late growing seasons. Warming weakened species interactions, as evidenced by fewer nodes and links and lower complexity and robustness in the network. Increased precipitation strengthened species interactions and eased the warming-induced negative effect under the interactive effect. Our findings emphasize that more attention should be given to the changes in the microbial community in the early growing season of grassland in Inner Mongolia under future climate change scenarios. • Climate change impacts were more obvious in the early growing season. • The interactive effect increased bacterial richness but reduced fungal richness. • Fewer taxa respond to climate change in the mid and late growing seasons. • Species interactions weakened by warming but enhanced by precipitation addition. [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]

• Alpine meadow had higher CUE and lower WUE than cultivated grassland under warming. • Warming decreased biomass of cultivated grassland in the later of the experiment. • Warming increased ET, did not affect GEP, and decreased WUE in alpine meadow. • Warming decreased NEE, did not alter ER, and decrease CUE in cultivated grassland. Carbon and water use efficiency (CUE and WUE) are crucial indicators of grassland ecosystem responses to climate change. Grass planting is one of the dominant methods of grassland restoration and agricultural production. However, how warming and reclamation impact grassland CUE and WUE remain unclear. Here we examined how warming affected carbon and water processes in natural alpine meadow and cultivated grassland, including gross ecosystem production (GEP), net ecosystem CO 2 exchange (NEE), evapotranspiration (ET), CUE and WUE. We deployed a seven-year warming experiment using open top chambers in alpine meadow and cultivated grassland on the Tibetan Plateau. Our results showed that the alpine meadow had a higher CUE and a lower WUE compared to the cultivated grassland under warming. Warming increased biomass production of the cultivated grassland in the beginning of the experiment but decreased it later in the experiment. Warming increased ET, did not affect GEP, and finally decreased WUE in the natural alpine meadow. In the cultivated grassland, warming decreased NEE, did not alter ER, and resulted the decrease in CUE. Our results highlight that reclamation decreases CUE and warming decreased WUE of alpine meadow. Although grass planting can increase biomass, the negative impacts of warming on carbon and water processes of cultivated grassland should be considered when reclaiming alpine meadow under warmer future. [ABSTRACT FROM AUTHOR]

Practical nitrogen fertilizers are required that simultaneously increase yield and reduce greenhouse gas (GHG) emissions from rice ( Oryza sativa L.) paddies. A field experiment was conducted to measure methane (CH 4 ) and nitrous oxide (N 2 O) fluxes in situ during two double rice-winter fallow rotations (2012–2014) under five different nitrogen fertilizer treatments: traditional urea (CK), polymer-coated controlled release urea (CRU), urea with N-Sever nitrapyrin (NU), urea with 3,4-dimethylpyrazole phosphate (DMPP), and urea with effective microorganisms (EM). The results revealed that GHG emissions ranged between 77.2 and 178.2 kg CH 4 ha −1 and 4.18 and 10.11 kg N 2 O ha −1 averagely over the whole rotation, and significant differences ( P < 0.05) among treatments and seasons were found. N 2 O emissions accounted for 26.6–36.9% of total GWP, and significant N 2 O emissions were observed during the winter fallow period, ranging from 3.1 to 3.88 kg N 2 O ha −1 . Compared to the GWP (7.66 and 8.85 Mg CO 2 ha −1 ) and GHGI (0.52 and 0.63 Mg CO 2 Mg −1 grain) from CK in 2012 and 2013 rotation, respectively, CRU achieved the highest reduction (48.5% for GWP and 55.4% for GHGI) in 2012, NU achieved the highest reduction (37.6% for GWP and 43.1% for GHGI) in 2013, and other treatments also realized different levels of decrease. Thus, controlled release urea, nitrification inhibitor or effective microorganisms might be effective fertilization options for low-carbon rice production with high yield. [ABSTRACT FROM AUTHOR]

Highlights: [•] The cost-effectiveness of water-saving irrigation based climate change mitigation was researched. [•] The cost-effectiveness of water-saving irrigation based climate change adaptation was researched. [•] The mitigation and adaptation potential in the coming decade was researched. [•] Development proposal of water-saving irrigation was made according to cost-effectiveness analysis. [ABSTRACT FROM AUTHOR]

Abstract: Although sensitivity analysis (SA) was conducted on the DeNitrification–DeComposition (DNDC) model, a global SA over a long period of time is lacking. We used a method of Bayesian analysis of computer code outputs (BACCO) with the Gaussian emulation machine for sensitivity analysis software (GEM-SA) to conduct a long-term SA of DNDC for predicting the annual change of soil organic carbon (dSOC), nitrous oxide emission (N2O) and grain yield of spring wheat. Twenty seven non-weather input parameters with wide ranges were selected for SA using weather data recorded from Three Hills, Alberta over 86 years (1921–2006). The SA had two steps: 1) a preliminary BACCO GEM-SA was conducted to identify a more accurate emulator sampling method and to screen out parameters with insignificant influence on model outcomes; and 2) final BACCO GEM-SA was conducted with optimal input design set for emulator training runs varying only the significant input parameters. Results indicated that the Maximin Latin Hypercube sampling method outperformed the LP-τ method with higher emulator accuracy. Most of the 27 input parameters contributed little to the three outputs by the first step BACCO GEM-SA. In the second step of BACCO GEM-SA there were only three (in the case of dSOC) and six (in the cases of N2O and yield) input parameters whose influence contributed to more than 10% of the total output variances by their total effects. Among the selected parameters, initial soil organic carbon and clay content are very important and were important in determining results for all three outputs. Sensitivities of some parameters, such as clay content and urea fertilizer amount changed dramatically over the years. This indicates that a single year SA may overestimate or underestimate a long-term parameter effect on the model prediction. The two-step procedure with the BACCO GEM-SA method improved the accuracy of SA and provided important information for model validation and parameterization. [Copyright &y& Elsevier]

China's green development has advanced national strategic requirements for excessive nitrogen application, greenhouse gas emission reduction, and efficient production in food systems. However, large challenges still exist in achieving these goals. In this study, a comprehensive meta-analysis and random forest identification were conducted to integrate nitrogen fertilization based nitrous oxide (N 2 O) emission data from field experiments in the dry farming system of China (DFSC), and to analyze the dependency of N 2 O emissions and crop yield on nitrogen inputs. We then quantified the potential reasonable nitrogen dose in the DFSC that would simultaneously reduce N 2 O emissions and favor China's green development. The results showed an absolute impact of nitrogen input on N 2 O emissions, and a significant nonlinear response between N 2 O emissions and nitrogen dose in the DFSC. However, the crop yield exhibited a different pattern: yields of cereal and cash crops in response to nitrogen input were modeled by a quadratic polynomial, especially at extremely high nitrogen rates (>300 kg N ha−1 for cereals and >600 kg N ha−1 for cash crops). The yield enhancing effect tended to be flat or even decrease. We propose to achieve a reasonable nitrogen dose by reducing the 1/3 nitrogen surplus in the DFSC, according to the various soil-climatic conditions. For cereal, cash, vegetable, tea and orchard crops, the values should be 98.72 – 133.46, 67.66 – 107.4, 258.53 – 470.57, 159.61–296.09 and 269.08–383.48 kg N ha−1, respectively. The findings of our investigation indicate that implementation of a reasonable nitrogen dosage will not give rise to a large yield decrease and will better contribute to meeting the requirements of N 2 O mitigation and a national green development strategy. • Nonlinear response of N 2 O emissions to N input exist in DFSC. • Crop yield in DFSC exhibited Quadratic polynomial correspondence to N application. • Reducing N 2 O emissions by abatement N use favors both food security and green development in China. [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]

• The effect of grazing regime on functional genes were different at distinct grazing period. • Grazing regime affected the temporal variation of soil microbial functional genes. • Grazing rather than exclosure promote C fixation and decomposition and N cycling. • There existed trade-offs between plant and soil nutrients along the grazing time. • Continuous grazing promoted CH 4 metabolism. Microbial functional genes can reflect the nutrient cycle activities in soil, because they encode various enzymes involved in the material cycle. Therefore, the gene abundance variation can reveal the impact of interference on the material cycle of grassland. To study the cycle of carbon (C), nitrogen (N) and phosphorus (P) between plant and soil in grassland under different grazing regimes, we investigated the soil microbial functional genes related to C, N, and P cycling by high-throughput quantitative PCR and 16S rRNA-based Illumina sequencing analysis under grazing exclusion (GE), rotational grazing (RG), and continuous grazing (CG) in alpine meadow of the Qinghai-Tibetan Plateau, where climate is characterized by little rain and low temperature, and grassland is very sensitive to grazing. The results showed at the early grazing period, C fixtion (rbcL , korA , and frdA) and lignin degradation (abfA , xylA , exg , lig , exoPG , chiA , and glx) processes were slower under GE; CH 4 metabolism (mcrA) was faster under CG; RG and CG improved the denitrification process (narG); RG slowed down organic-P mineralization (phoD). At the late grazing period, C fixation (accA and frdA) and degradation (mnp , apu , and amyA) processes were slower under GE; CH 4 metabolism (pmoA and mxa) was faster under CG; RG and CG improved the ammonia-oxidizing (amoA2), nitrification (hao), and denitrification (nirS3 and nirK1) processes. The majority of the genes involved in C, N, and P cycling decreased, the C, N and P content in plant leaf decreased, while that of soil increased from early to late grazing period. No matter grazing or not, there were negative relationships between genes and soil nutrients, and positive relationships between genes and plant nutrients, implying a trade-off between plant nutrients and soil nutrients along the grazing time. The genes responsible for regulating C and N cycling were increased under grazing, implying that reasonable grazing is beneficial to the nutrients cycling of grassland. [ABSTRACT FROM AUTHOR]

Our understanding on how soil organic carbon (SOC) storage, crop yield, and yield stability are influenced by climate is limited. To critically examine this, the impact of long-term (≥10 years) application of nutrient management practices on SOC storage, crop productivity, and yield stability were evaluated under different climatic conditions in China using a meta-analysis approach. The cropping area of China was divided into four distinct groups based on local climatic conditions (warm dry, DW; warm moist, WM; cool dry, CD; cool moist, CM). Results indicated that the impact of nutrient management practices on SOC storage, crop yield, and yield stability varies under different climatic zone in China. The use of unbalanced mineral fertilizer (UMF), and balanced mineral fertilizer (BMF) led to a loss in SOC storage by 6%, and 11% under CM climatic zone and gains in DW, WM, and CD climates. Organic fertilizers (OF), combined unbalanced mineral and organic fertilizers (UMOF), and combined balanced mineral and organic fertilizers (BMOF) were able to sustain and enhance SOC storage under all climatic conditions. However, the largest increase in SOC storage across all climates was seen for BMOF. Further, corresponding values of crop productivity and yield stability were also highest for BMOF among all the nutrient management treatments. A linear-plateau model indicated that maximal yield responsive SOC stock (C opt) levels ranged from 33.43 to 45.51 Mg C ha−1 for rice (Oryza sativa), maize (Zea mays), and wheat (Triticum aestivum) production. To enhance and sustain SOC storage, and crop productivity of croplands under different climates, BMOF appears to be the most appropriate nutrient management strategy. Our findings demonstrate that it is essential to optimize nutrient management strategies according to the local climate to protect soil from SOC losses, and for achieving sustainable crop production. • The impact of nutrient managements on SOC storage, crop yield, and yield stability varies under different climatic zones. • Unbalanced mineral, and balanced mineral fertilizer led to a loss in SOC storage by 6%, and 11% under cool moist climate. • Combined balanced mineral with organic inputs is crucial for maximal SOC storage and crop yields under different climates. • Maximal yield responsive SOC stock levels ranged from 33.43 to 45.51 Mg C ha−1 for rice, maize, and wheat production. [ABSTRACT FROM AUTHOR]

• Three isotopic methodologies were used to quantify the biogenic CH 4 production pathway. • AM processes predominant the CH 4 production in the agricultural river network. • Long-term measurements provide the new understanding of atmospheric CH 4. Methane (CH 4) emitted from river networks provides a globally significant, yet poorly constrained barrier for the refinement of national greenhouse gas (GHG) inventories and the global CH 4 budget. This study employed three isotopic methodologies, i.e., a simple mixing model, apparent fractionation factor, and dual isotopes (δ13C−CH 4 and δD−CH 4) to identify the biogenic CH 4 production pathway (BMPP) in a typical agricultural river network in subtropical China. The results indicated that the contribution of acetoclastic methanogenesis (AM) to BMPP in the Tuojia River network (TRN) ranged from 85 to 99%, with the first reach (S1) supporting the most biogenic CH 4 production. Furthermore, the α C value ranged from 1.00 to 1.039 and increased spatially over the four reaches (S1 to S4), while the α D value varied from 1.393 to 1.394, with S1 having the lowest value. The dual isotopes of δ13C and δD reflected a mixed BMPP. Clearly, the isotopic composition of CH 4 corroborated the predominance of AM in the BMPP in the TRN. Additionally, there was a remarkable spatiotemporal variation in δ13C−CH 4 and δD−CH 4 , as well as α C and α D. In combination with the correlation between the two paired isotopic signatures (antipathetic and positive, p < 0.05, respectively), this suggested a change in the BMPP in the TRN. The findings of our study implied that there was great impact of agricultural production and residential activities on environmental behavior of stable isotopes. Consequently, we recommend that multiple isotopic measures, based on long-term in situ isotopologue monitoring, should be applied when the uncertainties of CH 4 emissions from river networks are addressed. [ABSTRACT FROM AUTHOR]

• Responses of green up to warming were different among years. • Water addition did not advance community phenology except in a dry and warm year. • Warming increased annual variability of plant green up and flowering. • Flowering of K. pygmaea advanced under warming plus water addition in all three years. • Soil moisture plays a critical role in determining phenological response to warming. Temperature and precipitation are primary regulators of plant phenology. However, our knowledge of how these factors might interact to affect plant phenology is incomplete. The Qinghai-Tibetan Plateau, a cold and high region, has experienced no consistent changes in spring phenology, despite a significant warming trend. We conducted a manipulative experiment of warming and precipitation addition in an alpine meadow on the Qinghai-Tibetan Plateau in 2015 (cold and wet), 2016 (warm and dry) and 2017 (mild and very wet). We found that warming increased annual variability of plant spring phenology. Warming delayed green up of all monitored species in 2016, advanced green up of early flowering species in 2015, and did not alter green up in 2017. For example, green up of the shallow rooted Kobresia pygmaea advanced 8 (± 2) days in 2015 and was delayed by 23 (± 3) days in a dry year (2016) under warming compared with control. Early spring precipitation addition can offset the delaying effects of warming in a dry year on the Qinghai-Tibetan Plateau. Under warming plus precipitation addition, community average green up advanced compared to control plots in 2015 and 2016, and community average flowering advanced for all three years. In 2016, flowering of K. pygmaea (an early flowering species) advanced under warming plus precipitation addition compared to control while flowering of other species did not change. Our results highlight that annual variation of soil moisture condition plays a critical role in determining the magnitude and direction of spring phenology response to warming. We provide insights in how plant spring phenology might change in a warmer future in the presence or absence of precipitation increase. [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]

• Elevated [CO 2 ] and temperature jointly stimulated leaf A net before heading. • Air warming accelerated photosynthetic down-regulation under CO 2 enrichment after heading. • G s acclimated to warming and CO 2 enrichment in parallel with A net under no stress conditions. • Earlier leaf senescence, larger sink capacity or lower rice sterility might cause photosynthetic acclimation. • Co-elevation of [CO 2 ] and temperature increased dry matter productivity in Chinese double rice cultivation. Changes in atmospheric CO 2 concentration ([CO 2 ]) and temperature have impacts on leaf photosynthesis (A net) and stomatal conductance (G s) of rice, which strongly affect dry matter productivity. Understanding of the acclimation responses of A net and G s under elevated [CO 2 ] and/or temperature is limited. A field experiment of double rice (early rice-late rice rotation) was conducted using open-top chambers from 2013 to 2016 in Hubei Province, Central China, with two levels of [CO 2 ] (ambient, ambient + 60 μmol mol−1) and two levels of temperature (ambient, ambient + 2°C). Averaging across the four-year experiment, elevated [CO 2 ] and elevated temperature increased A net by 2.4 %–9.4 % and 2.4 %–10.7 %, respectively at pre-heading stages. A positive interaction was observed between elevated [CO 2 ] and temperature in early rice which further increased A net , while the interaction was not additive in late rice. Elevated [CO 2 ] caused lower G s and partly offset the stimulation of elevated temperature on G s at tillering and jointing. At post-heading stages, photosynthetic acclimation to elevated [CO 2 ] was observed as the stimulation of A net was not continued. Elevated temperature decreased A net by 1.7 %–16.6 % and further accelerated photosynthetic down-regulation by elevated [CO 2 ]. Warming reduced G s at milking and maturity in early rice because of high ambient temperature, which resulted in stomatal limitation to photosynthesis, but its effects on G s in late rice were positive because the ambient temperature was low. Generally, G s acclimated to warming and CO 2 enrichment in parallel with A net when there were no environmental constraints. Earlier leaf senescence, decreased leaf SPAD, lower seed-setting rate or larger sink capacity caused by elevated [CO 2 ] and/or temperature might directly or indirectly explain the down-regulation on photosynthesis after heading. Our results show that warming alters the acclimation of leaf photosynthesis and stomatal conductance to CO 2 enrichment and the combined effects differ between growth stages, and indicate that co-elevation of [CO 2 ] and temperature may increase dry matter productivity in the Chinese double rice cropping system. [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]

• Responses to warming differed between early rice and late rice. • Warming benefited yield formation before heading. • Benefits of CO 2 enrichment could eliminate the negative effects of warming on yield. • Yield may not decrease under future climate change in Chinese double rice system. Elevated atmospheric CO 2 concentration ([CO 2 ]) and temperature can strongly affect rice (Oryza sativa L.) production. However, the impact of warming is variable depending on ambient temperature and cropping system. Little is known about the effect of elevated temperature and its interaction with elevated [CO 2 ] in the Chinese double rice cropping system. To study this issue, field experiments were conducted using open-top chambers (OTC) with varying [CO 2 ] (ambient, ambient+60 μmol mol−1) and varying temperature (ambient, ambient+2 °C) for 4 rotations of double rice from 2013 to 2016. Elevated [CO 2 ] significantly increased grain yield in both early rice and late rice. This could be attributed to greater aboveground biomass, higher panicle number (m-2), spikelet number (per panicle) and 1000-grain weight. Elevated temperature decreased yield in early rice (except for 2016) due to decreases in % filled grains and 1000-grain weight. Elevated temperature increased yield in late rice due to increases in aboveground biomass, number of panicles and spikelets, although % filled grains decreased. We found that warming had positive effects on tiller development and dry matter accumulation during the pre-heading period both in early and late rice, which contributed to yield formation. When elevated temperature and [CO 2 ] were combined, yield changed by −1.9–23.7% in early rice compared with ambient condition as warming partly offset the benefits of CO 2 enrichment, while yield increased by 14.3–18.8% in late rice due to a synergy between warming and CO 2 enrichment. The benefits of CO 2 enrichment for fertile spikelets (m-2) and aboveground biomass could reduce or eliminate the negative impacts of warming. However, there were no significant interactions between elevated temperature and [CO 2 ] in most rice seasons. Our findings indicate that warming by 2 °C is not detrimental to yield formation under CO 2 enrichment, and suggest that grain yield may not decrease under future climate change in the Chinese double rice cropping system. [ABSTRACT FROM AUTHOR]