Effects of three patterns of elevated CO2 in single and multiple generations on photosynthesis and stomatal features in rice.

BACKGROUND AND AIMS: Effects of elevated CO2 (E) within a generation on photosynthesis and stomatal features have been well documented in crops; however, long-term responses to gradually elevated CO2 (Eg) and abruptly elevated CO2 (Ea) over multiple generations remain scarce. METHODS: Japonica rice plants grown in open-top chambers were tested in the first generation (F1) under Ea and in the fifth generation (F5) under Eg and Ea, as follows: Ea in F1: ambient CO2 (A) + 200 µmol mol-1; Eg in F5: an increase of A + 40 µmol mol-1 year-1 until A + 200 µmol mol-1 from 2016 to 2020; Ea in F5: A + 200 µmol mol-1 from 2016 to 2020. For multigenerational tests, the harvested seeds were grown continuously in the following year in the respective CO2 environments. KEY RESULTS: The responses to Ea in F1 were consistent with the previous consensus, such as the occurrence of photosynthetic acclimation, stimulation of photosynthesis, and downregulation of photosynthetic physiological parameters and stomatal area. In contrast, multigenerational exposure to both Eg and Ea did not induce photosynthetic acclimation, but stimulated greater photosynthesis and had little effect on the photosynthetic physiology and stomatal traits. This suggests that E retained intergenerational effects on photosynthesis and stomatal features and that there were no multigenerational differences in the effects of Eg and Ea. CONCLUSIONS: The present study demonstrated that projecting future changes induced by E based on the physiological responses of contemporary plants could be misleading. Thus, responses of plants to large and rapid environmental changes within a generation cannot predict the long-term response of plants to natural environmental changes over multiple generations, especially in annual herbs with short life cycles.

The determiner of photosynthetic acclimation induced by biochemical limitation under elevated CO2 in japonica rice.

Photosynthetic acclimation to prolonged elevated CO2 could be attributed to the two limited biochemical capacity, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylation and ribulose-1,5-bisphosphate (RuBP) regeneration, however, which one is the primary driver is unclear. To quantify photosynthetic acclimation induced by biochemical limitation, we investigated photosynthetic characteristics and leaf nitrogen allocation to photosynthetic apparatus (Rubisco, bioenergetics, and light-harvesting complex) in a japonica rice grown in open-top chambers at ambient CO2 and ambient CO2+200 µmol mol-1 (e [CO2]). Results showed that photosynthesis was stimulated under e [CO2], but concomitantly, photosynthetic acclimation obviously occurred across the whole growth stages. The content of leaf nitrogen allocation to Rubisco and biogenetics was reduced by e [CO2], while not in light-harvesting complex. Unlike the content, there was little effects of CO2 enrichment on the percentage of nitrogen allocation to photosynthetic components. Additionally, leaf nitrogen did not reallocate within photosynthetic apparatus until the imbalance of sink-source under e [CO2]. The contribution of biochemical limitations, including Rubisco carboxylation and RuBP regeneration, to photosynthetic acclimation averaged 36.2% and 63.8% over the growing seasons, respectively. This study suggests that acclimation of photosynthesis is mainly driven by RuBP regeneration limitation and highlights the importance of RuBP regeneration relative to Rubisco carboxylation in the future CO2 enrichment.

Carbon fluxes and soil carbon dynamics along a gradient of biogeomorphic succession in alpine wetlands of Tibetan Plateau.

Hydrological changes under climate warming drive the biogeomorphic succession of wetlands and may trigger substantial carbon loss from the carbon-rich ecosystems. Although many studies have explored the responses of wetland carbon emissions to short-term hydrological change, it remains poorly understood how the carbon cycle evolves with hydrology-driven wetland succession. Here, we used a space-for-time approach across hydrological gradients on the Tibetan Plateau to examine the dynamics of ecosystem carbon fluxes (carbon dioxide (CO2) and methane (CH4)) and soil organic carbon pools during alpine wetland succession. We found that the succession from mesic meadow to fen changed the seasonality of both CO2 and CH4 fluxes, which was related to the shift in plant community composition, enhanced regulation of soil hydrology and increasing contribution of spring-thaw emission. The paludification caused a switch from net uptake of gaseous carbon to net release on an annual timescale but produced a large accumulation of soil organic carbon. We attempted to attribute the paradox between evidence from the carbon fluxes and pools to the lateral carbon input and the systematic changes of historical climate, given that the wetlands are spatially low-lying with strong temporal climate-carbon cycle interactions. These findings demonstrate a systematic change in the carbon cycle with succession and suggest that biogeomorphic succession and lateral carbon flows are both important for understanding the long-term dynamics of wetland carbon footprints.

Metformin Hydrochloride Mucosal Nanoparticles-Based Enteric Capsule for Prolonged Intestinal Residence Time, Improved Bioavailability, and Hypoglycemic Effect.

Metformin hydrochloride enteric-coated capsule (MH-EC) is a commonly used clinical drug for the treatment of type 2 diabetes. In this study, we described a metformin hydrochloride mucosal nanoparticles enteric-coated capsule (MH-MNPs-EC) based on metformin hydrochloride chitosan mucosal nanoparticles (MH-CS MNPs) and its preparation method to improve the bioavailability and hypoglycemic effect duration of MH-EC. In intestinal adhesion study, the residue rates of free drugs and mucosal nanoparticles were 10.52% and 67.27%, respectively after cleaned with PBS buffer. MH-CS MNPs could significantly improve the efficacy of MH and promote the rehabilitation of diabetes rats. In vitro release test of MH-MNPs-EC showed continuous release over 12 h, while commercial MH-EC released completely within about 1 h in intestinal environment (pH 6.8). Pharmacokinetic study was performed in beagle dogs compared to the commercial MH-EC. The durations of blood MH concentration above 2 µg/mL were 9 h for MH-MNPs-EC versus 2 h for commercial MH-EC. The relative bioavailability of MH-MNPs-EC was determined as 185.28%, compared with commercial MH-EC. In conclusion, MH-CS MNPs have good intestinal adhesion and can significantly prolong the residence time of MH in the intestine. MH-MNPs-EC has better treatment effect compared with MH-EC, and it is expected to be a potential drug product for the treatment of diabetes because of its desired characteristics.

Effect of Sintering Temperature on Properties of Carbon Fiber-Reinforced Titanium Matrix Composites.

Carbon fiber-reinforced titanium matrix composites were prepared by powder metallurgy. Carbon fiber (CF) powder and titanium (Ti) powder are mixed, pressed, and then sintered at a high temperature of 1300-1500 °C. The morphology and conductivity of carbon fiber-reinforced titanium matrix (Ti-CF) composites were studied. When the temperature range of the Ti-CF composites was from 1300 to 1500 °C, the porosity and resistivity first decreased and then increased. When the sintering temperature was 1350 °C, the diffraction peak of the sample was the strongest, the porosity was the smallest (4.16%), and the resistivity was the smallest (2.7 MΩ·mm). CFs have a very good strengthening effect on titanium-based composite materials.

The role of China's terrestrial carbon sequestration 2010-2060 in offsetting energy-related CO2 emissions.

Energy consumption dominates annual CO2 emissions in China. It is essential to significantly reduce CO2 emissions from energy consumption to reach national carbon neutrality by 2060, while the role of terrestrial carbon sequestration in offsetting energy-related CO2 emissions cannot be underestimated. Natural climate solutions (NCS), including improvements in terrestrial carbon sequestration, represent readily deployable options to offset anthropogenic greenhouse gas emissions. However, the extent to which China's terrestrial carbon sequestration in the future, especially when target-oriented managements (TOMs) are implemented, can help to mitigate energy-related CO2 emissions is far from certain. By synthesizing available findings and using several parameter-sparse empirical models that have been calibrated and/or fitted against contemporary measurements, we assessed China's terrestrial carbon sequestration over 2010-2060 and its contribution to offsetting national energy-related CO2 emissions. We show that terrestrial C sequestration in China will increase from 0.375 ± 0.056 (mean ± standard deviation) Pg C yr-1 in the 2010s to 0.458 ± 0.100 Pg C yr-1 under RCP2.6 and 0.493 ± 0.108 Pg C yr-1 under the RCP4.5 scenario in the 2050s, when TOMs are implemented. The majority of carbon sequestration comes from forest, accounting for 67.8-71.4% of the total amount. China's terrestrial ecosystems can offset 12.2-15.0% and 13.4-17.8% of energy-related peak CO2 emissions in 2030 and 2060, respectively. The implementation of TOMs contributes 11.9% of the overall terrestrial carbon sequestration in the 2020s and 23.7% in the 2050s. The most likely strategy to maximize future NCS effectiveness is a full implementation of all applicable cost-effective NCS pathways in China. Our findings highlight the role of terrestrial carbon sequestration in offsetting energy-related CO2 emissions and put forward future needs in the context of carbon neutrality.

Sedimentary Nitrogen and Sulfur Reduction Functional-Couplings Interplay With the Microbial Community of Anthropogenic Shrimp Culture Pond Ecosystem.

Sediment nitrogen and sulfur cycles are essential biogeochemical processes that regulate the microbial communities of environmental ecosystems, which have closely linked to environment ecological health. However, their functional couplings in anthropogenic aquaculture sedimentary ecosystems remain poorly understood. Here, we explored the sediment functional genes in shrimp culture pond ecosystems (SCPEs) at different culture stages using the GeoChip gene array approach with 16S amplicon sequencing. Dissimilarity analysis showed that the compositions of both functional genes and bacterial communities differed at different phases of shrimp culture with the appearance of temporal distance decay (p < 0.05). During shrimp culture, the abundances of nitrite and sulfite reduction functional genes decreased (p < 0.05), while those of nitrate and sulfate reduction genes were enriched (p < 0.05) in sediments, implying the enrichment of nitrites and sulfites from microbial metabolism. Meanwhile, nitrogen and sulfur reduction genes were found to be linked with carbon degradation and phosphorous metabolism (p < 0.05). The influence pathways of nutrients were demonstrated by structural equation modeling through environmental factors and the bacterial community on the nitrogen and sulfur reduction functions, indicating that the bacterial community response to environmental factors was facilitated by nutrients, and led to the shifts of functional genes (p < 0.05). These results indicate that sediment nitrogen and sulfur reduction functions in SCPEs were coupled, which are interconnected with the SCPEs bacterial community. Our findings will be helpful for understanding biogeochemical cycles in anthropogenic aquaculture ecosystems and promoting sustainable management of sediment environments through the framework of an ecological perspective.

Terrestrial carbon sinks in China and around the world and their contribution to carbon neutrality.

Enhancing the terrestrial ecosystem carbon sink (referred to as terrestrial C sink) is an important way to slow down the continuous increase in atmospheric carbon dioxide (CO2) concentration and to achieve carbon neutrality target. To better understand the characteristics of terrestrial C sinks and their contribution to carbon neutrality, this review summarizes major progress in terrestrial C budget researches during the past decades, clarifies spatial patterns and drivers of terrestrial C sources and sinks in China and around the world, and examines the role of terrestrial C sinks in achieving carbon neutrality target. According to recent studies, the global terrestrial C sink has been increasing from a source of (-0.2±0.9) Pg C yr-1 (1 Pg=1015 g) in the 1960s to a sink of (1.9±1.1) Pg C yr-1 in the 2010s. By synthesizing the published data, we estimate terrestrial C sink of 0.20-0.25 Pg C yr-1 in China during the past decades, and predict it to be 0.15-0.52 Pg C yr-1 by 2060. The terrestrial C sinks are mainly located in the mid- and high latitudes of the Northern Hemisphere, while tropical regions act as a weak C sink or source. The C balance differs much among ecosystem types: forest is the major C sink; shrubland, wetland and farmland soil act as C sinks; and whether the grassland functions as C sink or source remains unclear. Desert might be a C sink, but the magnitude and the associated mechanisms are still controversial. Elevated atmospheric CO2 concentration, nitrogen deposition, climate change, and land cover change are the main drivers of terrestrial C sinks, while other factors such as fires and aerosols would also affect ecosystem C balance. The driving factors of terrestrial C sink differ among regions. Elevated CO2 concentration and climate change are major drivers of the C sinks in North America and Europe, while afforestation and ecological restoration are additionally important forcing factors of terrestrial C sinks in China. For future studies, we recommend the necessity for intensive and long term ecosystem C monitoring over broad geographic scale to improve terrestrial biosphere models for accurately evaluating terrestrial C budget and its dynamics under various climate change and policy scenarios.

Environmental Water and Sediment Microbial Communities Shape Intestine Microbiota for Host Health: The Central Dogma in an Anthropogenic Aquaculture Ecosystem.

From increasing evidence has emerged a tight link among the environment, intestine microbiota, and host health status; moreover, the microbial interaction in different habitats is crucial for ecosystems. However, how the environmental microbial community assembly governs the intestinal microbiota and microbial communities of multiple habitats contribute to the metacommunity remain elusive. Here, we designed two delicate experiments from temporal and spatial scales in a shrimp culture pond ecosystem (SCPE). Of the SCPE metacommunity, the microbial diversity was mainly contributed to by the diversity of-ß IntraHabitats and ß InterHabitats , and water and sediment communities had a large contribution to the shrimp intestine community as shown by SourceTracker and Sloan neutral community model analyses. Also, phylogenetic bin-based null model results show that microbial assembly of three habitats in the SCPE appeared to be largely driven by stochastic processes. These results enrich our understanding of the environment-intestinal microbiota-host health closely linked relationship, making it possible to be the central dogma for an anthropogenic aquaculture ecosystem. Our findings enhance the mechanistic understanding of microbial assembly in the SCPE for further analyzing metacommunities, which has important implications for microbial ecology and animal health.

Distinct bacterial communities in the environmental water, sediment and intestine between two crayfish-plant coculture ecosystems.

Microorganisms are an important part of productivity, water quality, and biogeochemical cycles in an aquaculture ecosystems and play a key role in determining the growth and fitness of aquaculture animals. Coculture ecosystems are widely applied with great significance in agricultural production worldwide. The crayfish-rice coculture ecosystem (CRCE) and crayfish-waterweed coculture ecosystem (CWCE) are two high-profile artificial ecosystems for crayfish culture. However, the bacterial communities of the environmental water, sediment, and intestine in the CRCE and CWCE remain elusive. In this study, we investigated the diversity, composition, and function of bacterial communities in water, sediment, and intestine samples from the CRCE to CWCE. The physicochemical factors of water [such as ORP (oxidation-reduction potential), TC (total carbon), TOC (total oxygen carbon), and NO3--N] and sediment [such as TC, TOC, TN (total nitrogen), and TP (total phosphate)] were significantly different in the CRCE and CWCE. The abundances of Proteobacteria, Actinobacteria, Verrucomicrobia, Cyanobacteria, Chlorobi, Chloroflexi, and Firmicutes were significantly different in the water bacterial communities of the CRCE and CWCE. The abundance of Vibrio in the crayfish intestine was higher in the CRCE than in the CWCE. The most abundant phyla in the CRCE and CWCE sediment were Proteobacteria and Bacteroidetes. The abundances of genes involved in transporters and ABC transporters were different in water of CRCE and CWCE. The abundances of genes involved in oxidative phosphorylation were significantly higher in the crayfish intestine of the CRCE than in that of the CWCE. Furthermore, the functional genes associated with carbon metabolism were significantly more abundant in the sediment of the CRCE than in that of the CWCE. Spearman correlation analysis and redundancy analysis (RDA) showed that the bacterial communities of the water and sediment in the CRCE and CWCE were correlated with environmental factors (pH, total carbon (TC), total oxygen carbon (TOC), total nitrogen (TN), and total phosphorus (TP)). Our findings showed that the composition, diversity and function of the bacterial communities were distinct in the environmental water, sediment, and intestine of the CRCE and CWCE crayfish coculture ecosystems due to their different ecological patterns. These results can help guide healthy farming practices and deepen the understanding of bacterial communities in crayfish-plant coculture ecosystems from the perspective of bacterial ecology. KEY POINTS: • The composition of bacterial communities in the environmental water, sediment, and intestine of the CRCE and CWCE were distinct. ̉• The abundances of genes involved in transporters and ABC transporters were different in the water of the CRCE and CWCE. • The bacterial communities of the water and sediment in the CRCE and CWCE were correlated with some environmental factors.

Intestine Bacterial Community Composition of Shrimp Varies Under Low- and High-Salinity Culture Conditions.

Intestine microbiota is tightly associated with host health status. Increasing studies have focused on assessing how host intestine microbiota is affected by biotic factors but ignored abiotic factors. Here, we aimed to understand the effects of salinity on shrimp intestine microbiota, by comparing the differences of intestine bacterial signatures of shrimp under low-salinity (LS) and high-salinity (HS) culture conditions. Our results found that intestine core bacterial taxa of shrimp under LS and HS culture conditions were different and that under HS contained more opportunistic pathogen species. Notably, compared with LS culture conditions, opportunistic pathogens (e.g., Vibrio species) were enriched in shrimp intestine under HS. Network analysis revealed that shrimp under HS culture conditions exhibited less connected and lower competitive intestine bacterial interspecies interactions compared with LS. In addition, under HS culture conditions, several opportunistic pathogens were identified as keystone species of intestine bacterial network in shrimp. Furthermore, the ecological drift process played a more important role in the intestine bacterial assembly of shrimp under HS culture conditions than that under LS. These above traits regarding the intestine microbiota of shrimp under HS culture conditions might lead to host at a higher risk of disease. Collectively, this work aids our understanding of the effects of salinity on shrimp intestine microbiota and helps for shrimp culture.

Dissimilarity of microbial diversity of pond water, shrimp intestine and sediment in Aquamimicry system.

The Pacific white shrimp, with the largest production in shrimp industry, has suffered from multiple severe viral and bacterial diseases, which calls for a more reliable and environmentally friendly system to promote shrimp culture. The "Aquamimicry system", mimicking the nature of aquatic ecosystems for the well-being of aquatic animals, has effectively increased shrimp production and been adapted in many countries. However, the microbial communities in the shrimp intestine and surrounding environment that act as an essential component in Aquamimicry remain largely unknown. In this study, the microbial composition and diversity alteration in shrimp intestine, surrounding water and sediment at different culture stages were investigated by high throughput sequencing of 16S rRNA gene, obtaining 13,562 operational taxonomic units (OTUs). Results showed that the microbial communities in shrimp intestine and surrounding environment were significantly distinct from each other, and 23 distinguished taxa for each habitat were further characterized. The microbial communities differed significantly at different culture stages, confirmed by a great number of OTUs dramatically altered during the culture period. A small part of these altered OTUs were shared between shrimp intestine and surrounding environment, suggesting that the microbial alteration of intestine was not consistent with that of water and sediment. Regarding the high production of Aquamimicry farm used as a case in this study, the dissimilarity between intestinal and surrounding microbiota might be considered as a potential indicator for healthy status of shrimp farming, which provided hints on the appropriate culture practices to improve shrimp production.

Visualized analysis and evaluation of simultaneous controlled release of metformin hydrochloride and gliclazide from sandwiched osmotic pump capsule.

The aim of this study was to develop the Metformin Hydrochloride and Gliclazide (MH-GZ) sandwiched osmotic pump capsule which could overcome the problems associated with short half-life and burst release. The system could deliver drugs with different solubility simultaneously at zero-order rate, in which MH-GZ were filled in both sides of the push layer respectively. The single factor and orthogonal test were employed to obtain the optimized formulation with the evaluation index of similarity factor (ƒ2). R language was used to visualized analyze the main influence factors of drug release and their correlations. Pharmacokinetic study was performed in beagle dogs compared to the marketed conventional product, which showed decreased Cmax, prolonged Tmax, and improved bioavailability, independent of pH and agitational speed but related to osmotic pressure differences across the semi permeable membrane. The designed sandwiched osmotic pump capsule proposed a promising substitute for the marketed product for the treatment of type 2 diabetes.

Microecological Koch's postulates reveal that intestinal microbiota dysbiosis contributes to shrimp white feces syndrome.

BACKGROUND: Recently, increasing evidence supports that some complex diseases are not attributed to a given pathogen, but dysbiosis in the host intestinal microbiota (IM). The full intestinal ecosystem alterations, rather than a single pathogen, are associated with white feces syndrome (WFS), a globally severe non-infectious shrimp disease, while no experimental evidence to explore the causality. Herein, we conducted comprehensive metagenomic and metabolomic analysis, and intestinal microbiota transplantation (IMT) to investigate the causal relationship between IM dysbiosis and WFS. RESULTS: Compared to the Control shrimp, we found dramatically decreased microbial richness and diversity in WFS shrimp. Ten genera, such as Vibrio, Candidatus Bacilloplasma, Photobacterium, and Aeromonas, were overrepresented in WFS, whereas 11 genera, including Shewanella, Chitinibacter, and Rhodobacter were enriched in control. The divergent changes in these populations might contribute the observation that a decline of pathways conferring lipoic acid metabolism and mineral absorption in WFS. Meanwhile, some sorts of metabolites, especially lipids and organic acids, were found to be related to the IM alteration in WFS. Integrated with multiomics and IMT, we demonstrated that significant alterations in the community composition, functional potentials, and metabolites of IM were closely linked to shrimp WFS. The distinguished metabolites which were attributed to the IM dysbiosis were validated by feed-supplementary challenge. Both homogenous selection and heterogeneous selection process were less pronounced in WFS microbial community assembly. Notably, IMT shrimp from WFS donors eventually developed WFS clinical signs, while the dysbiotic IM can be recharacterized in recipient shrimp. CONCLUSIONS: Collectively, our findings offer solid evidence of the causality between IM dysbiosis and shrimp WFS, which exemplify the 'microecological Koch's postulates' (an intestinal microbiota dysbiosis, a disease) in disease etiology, and inspire our cogitation on etiology from an ecological perspective. Video abstract.

Climate drives global soil carbon sequestration and crop yield changes under conservation agriculture.

Conservation agriculture has been shown to have multiple benefits for soils, crop yield and the environment, and consequently, no-till, the central practice of conservation agriculture, has rapidly expanded. However, studies show that the potential for carbon (C) sequestration in no-till farming sometimes is not realized, let alone the ability to maintain or improve crop yield. Here we present a global analysis of no-till-induced changes of soil C and crop yield based on 260 and 1,970 paired studies; respectively. We show that, relative to local conventional tillage, arid regions can benefit the most from conservation agriculture by achieving a win-win outcome of enhanced C sequestration and increased crop yield. However, more humid regions are more likely to increase SOC only, while some colder regions have yield losses and soil C loss as likely as soil C gains. In addition to site-specific characteristics and management, a careful assessment of the regional climate is needed to determine the potential benefits of adopting conservation agriculture.

[Effect of different levels of elevated CO2 concentration on leaf chlorophyll fluorescence cha-racteristics of Japonica rice]. / 不同CO2æµ“åº¦å‡é«˜æ°´å¹³å¯¹ç²³ç¨»å¶ç‰‡è§å ‰ç‰¹æ€§çš„å½±å“.

To examine the effects of elevated CO2 concentrations on chlorophyll fluorescence of rice leaf, a field experiment was conducted with automatic control system of CO2 concentration in open top-chambers (OTCs). There were three treatments, including atmospheric CO2 concentration (CK), CK+80 µmol·mol-1 CO2 (T1), and CK+200 µmol·mol-1 CO2 (T2). The fast chlorophyll fluorescence induction dynamic curves of flag leaves were measured using the plant efficiency analyzer at the main growth stages of rice. The results showed that T1 treatment significantly increased quantum yield for electron transfer (φEo), maximum photochemical efficiency (Fv/Fm), and performance index (PIABS), but decreased quantum yield for energy dissipation (φDo) at the flowe-ring, milk grain, ripening, and full ripeness stages. The values of φEo, Fv/Fm, and PIABS were increased by 7.3%-23.3%, 3.1%-7.1%, and 46.2%-93.0%, respectively. The φDo values were decreased by 10.3%-20.5%. T2 treatment significantly decreased φEo, Fv/Fm, PIABS by 68.7%, 41.4%, and 93.4%, respectively, but increased φDo by 78.4% at the jointing stage. T2 treatment significantly increased φEo, Fv/Fm, PIABS by 11.6%-19.8%, 4.8%-6.8%, and 53.0%-72.6%, respectively, and decreased φDo by 7.7%-19.4% at the flowering, milk grain, and ripening stages. Our results suggested that elevated CO2 concentration (80, 200 µmol·mol-1) would promote photosynthetic electron transport of PS2 in flag leaves of rice.

Prediction of CH4 emissions from potential natural wetlands on the Tibetan Plateau during the 21st century.

The alpine wetlands on the Tibetan Plateau (TP) are ecosystems vulnerable to global climate change. It has been recognized that future climate change may have a significant impact on methane (CH4) emissions from the plateau, while less attention has been paid to predicting temporal and spatial variations in CH4 emissions from TP natural wetlands. In this study, we used an integrated model framework based on the CH4MODwetland, TOPMODEL and TEM models to predict CH4 emissions from potential natural wetlands on the TP under IPCC AR5 scenarios from 2006 to 2100. The model estimates suggest that the mean area-weighted CH4 fluxes will increase from 4.45 ±â€¯0.42 g m-2 yr-1 in 2006 to 4.79 ±â€¯0.72, 5.99 ±â€¯0.85 and 11.53 ±â€¯1.33 g m-2 yr-1 under 3 Representative Concentration Pathway scenarios (RCP 2.6, RCP 4.5 and RCP 8.5 scenarios), respectively, by 2100. The dominant drivers stimulating CH4 emissions are air temperature, precipitation and net primary productivity (NPP). Spatially, CH4 fluxes and emissions showed a decreasing trend from south to north and from east to west. In response to climate change, a total of 0.42 ±â€¯0.06, 0.54 ±â€¯0.09 and 1.01 ±â€¯0.12 Tg yr-1 of CH4 emissions will be emitted from the TP's potential natural wetlands by the end of this century under the RCP 2.6, RCP 4.5 and RCP 8.5 scenarios, respectively.

A synthesis of soil carbon and nitrogen recovery after wetland restoration and creation in the United States.

Wetland restoration and creation efforts have been widely attempted as a way to compensate for wetland losses and to recover wetland functions; however, to date, there has been no comprehensive evaluation of the efficacy of soil carbon (C) and nitrogen (N) content recovery at a regional scale. This meta-analysis synthesizes 48 articles to identify the general patterns of soil C and N change after wetland restoration and creation in the United States. Our results indicate that, after 11-20 years, soil C and N in restored and created wetlands are still significantly lower by 51.7% and 50.3%, respectively, than those in natural wetlands. The soil C and N in restored wetlands recovered faster than in created wetlands. Furthermore, the soil C in restored organic flat and created depressional wetlands recovered more rapidly than in restored and created hydrologically open wetlands (riverine and tidal), respectively. Mean annual temperature and soil texture were recognized as two crucial abiotic factors affecting soil C and N recovery. Linear regression analysis revealed a positive relationship between the restoration and creation effect sizes on soil C and N, indicating that wetlands may alleviate N limitations intrinsically during C recovery processes.

Molecular mechanisms of water table lowering and nitrogen deposition in affecting greenhouse gas emissions from a Tibetan alpine wetland.

Rapid climate change and intensified human activities have resulted in water table lowering (WTL) and enhanced nitrogen (N) deposition in Tibetan alpine wetlands. These changes may alter the magnitude and direction of greenhouse gas (GHG) emissions, affecting the climate impact of these fragile ecosystems. We conducted a mesocosm experiment combined with a metagenomics approach (GeoChip 5.0) to elucidate the effects of WTL (-20 cm relative to control) and N deposition (30 kg N ha-1  yr-1 ) on carbon dioxide (CO2 ), methane (CH4 ) and nitrous oxide (N2 O) fluxes as well as the underlying mechanisms. Our results showed that WTL reduced CH4 emissions by 57.4% averaged over three growing seasons compared with no-WTL plots, but had no significant effect on net CO2 uptake or N2 O flux. N deposition increased net CO2 uptake by 25.2% in comparison with no-N deposition plots and turned the mesocosms from N2 O sinks to N2 O sources, but had little influence on CH4 emissions. The interactions between WTL and N deposition were not detected in all GHG emissions. As a result, WTL and N deposition both reduced the global warming potential (GWP) of growing season GHG budgets on a 100-year time horizon, but via different mechanisms. WTL reduced GWP from 337.3 to -480.1 g CO2 -eq m-2 mostly because of decreased CH4 emissions, while N deposition reduced GWP from 21.0 to -163.8 g CO2 -eq m-2 , mainly owing to increased net CO2 uptake. GeoChip analysis revealed that decreased CH4 production potential, rather than increased CH4 oxidation potential, may lead to the reduction in net CH4 emissions, and decreased nitrification potential and increased denitrification potential affected N2 O fluxes under WTL conditions. Our study highlights the importance of microbial mechanisms in regulating ecosystem-scale GHG responses to environmental changes.

A comparison of methane emission measurements using Eddy Covariance and manual and automated chamber-based techniques in Tibetan Plateau alpine wetland.

Comparing of different CH4 flux measurement techniques allows for the independent evaluation of the performance and reliability of those techniques. We compared three approaches, the traditional discrete Manual Static Chamber (MSC), Continuous Automated Chamber (CAC) and Eddy Covariance (EC) methods of measuring the CH4 fluxes in an alpine wetland. We found a good agreement among the three methods in the seasonal CH4 flux patterns, but the diurnal patterns from both the CAC and EC methods differed. While the diurnal CH4 flux variation from the CAC method was positively correlated with the soil temperature, the diurnal variation from the EC method was closely correlated with the solar radiation and net CO2 fluxes during the daytime but was correlated with the soil temperature at nighttime. The MSC method showed 25.3% and 7.6% greater CH4 fluxes than the CAC and EC methods when measured between 09:00 h and 12:00 h, respectively.