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Reservoir drawdown areas (DAs) can be both important nitrogen (N) sources to river networks and hot spots for N removal from freshwater ecosystems. The net effect of DAs on the N availability in reservoirs within a full hydrological cycle remains unclear. In this paper, the N dynamics in the DA of the Three Gorges Reservoir, Yangtze River, China, are investigated through a combination of discrete and continuous in situ observations and sampling over a span of 2 years, complemented by numerical modeling. We show that the DA is a net source of N to the water column, and that about 30% of the total annual N load released from the DA is mitigated by the sediment through denitrification and capture. The annual net load of the total N from the DA to the reservoir is ca. 0.59 kg per meter along the river, which is on the same order of magnitude as the input load from the density current of the Yangtze River to its tributaries, generally considered to be the primary driver of eutrophication in tributaries. N release in the DA mainly occurs during the drying period, whereas denitrification in the sediment mostly takes place during the flooding period when the oxido‐reducing potential is low. Our findings quantify and therefore clarify the N source/sink dynamics from the DA to the reservoir, offering a new perspective on the importance of DA nutrient loading in decision‐making related to integrated management of inundated lands to alleviate reservoir eutrophication by river damming. Plain Language Summary: Nitrogen (N) is an essential nutrient element, but it can be harmful to water quality in excess amounts. Drawdown areas (DAs) are regions at the edges of reservoirs that are alternately flooded and dried as water levels rise and fall. In some conditions, DAs can cause N pollution by adding N to the reservoirs, while in other conditions, DAs can alleviate pollution by removing N from the reservoir by turning it into a gas through the process of denitrification. The annual balance for these pollution‐driving versus pollution‐alleviating processes across the entire year remains unclear. Based on 2 years of continuous field observations and modeling of N cycling in the DA of the Three Gorges Reservoir, China, this paper finds that annually sediment denitrification and retention in the DA eliminates 30% of the N load released from the sediment itself. N release in the DA mainly occurs when reservoir water level falls as the weather warms up. Denitrification, which turns nitrate into a gas that can leave the reservoir and enter the atmosphere, in sediment under high water levels is the main mechanism that removes N from the DAs. We find that the amount of N released to the reservoir from the DAs is similar in size to the N load received from the upstream river, and thus needs to be considered in reservoir water quality management decisions. Key Points: The drawdown area (DA) is a net source of nitrogen (N) to the Three Gorges Reservoir water column within a full hydrological cycleAbout 30% of the total N load to the water column from the reservoir DA is mitigated by the sediment through denitrification and captureN release from the reservoir DA mainly occurs during the drying period, whereas N removal from the water column mainly occurs during flooding [ABSTRACT FROM AUTHOR]

The effectiveness of national policies for air pollution control has been demonstrated, but the relative effectiveness of short-term emission reduction measures in comparison with national policies has not. Here we show that short-term abatement measures during important international events substantially reduced PM2.5 concentrations, but air quality rebounded to pre-event levels after the measures ceased. Long-term adherence to strict emission reduction policies led to successful decreases of 54% in PM2.5 concentrations in Beijing, and 23% in atmospheric nitrogen deposition in China from 2012 to 2020. Incentivized by "blue skies" type campaigns, economic development and reactive nitrogen pollution are quickly decoupled, showing that a combination of inspiring but aggressive short-term measures and effective but durable long-term policies delivers sustainable air quality improvement. However, increased ammonia concentrations, transboundary pollutant flows, and the complexity to achieving reduction targets under climate change scenarios, underscore the need for the synergistic control of multiple pollutants and inter-regional action. In response to the rebound of air pollution during large events in China, the authors propose that a combination of ambitious short-term measures and enduring long-term pollution control policies is a sustainable solution for improving air quality. [ABSTRACT FROM AUTHOR]

Potential toxic elements (PTEs), including Pb, Cr, Cd, Ni, Cu, As, and Mo, are common pollutants in ion-adsorption rare earth mines (IAREEMs), and atmospheric deposition is an important method of PTE migration. However, the level of PTE atmospheric deposition in and around IAREEMs remains unknown. We established 25 stations at typical sites in the Ganzhou city of southeast China. An exposure assessment model was used to evaluate the health risks for adults and children. The results show that the concentration and fluxes of atmospheric deposition of PTEs follow the order of Pb > Cu > Cr > Ni > As > Mo > Cd, and most PTEs present no human health risk. However, due to the high toxicty of As, it poses both carcinogenic and non-carcinogenic risks to children as indicated by the analysis of an exposure assessment model of heavy rare earth minerals in Longnan county, Ganzhou city. The As concentration in atmospheric deposition ranged from 3.18 to 251.87 mg kg−1, and the As atmospheric fluxes in atmospheric deposition ranged from 0.11 to 39.4 mg m−2 y−1. This is because As-rich materials (e.g., arsenic-adsorbing clay zones and chernovite-(Y) (Y[AsO4])) are exposed in fully weathered layers, and the formed suspended particulate matter is transported into the atmosphere at Longnan county. Consequently, restoring vegetation to reduce particulate matter transport is an important method for controlling the spread of pollutants. These results provide significant insights into pollution characteristics and prevention in and around mining areas under the influence of atmospheric deposition. [ABSTRACT FROM AUTHOR]

Trace metals from natural and anthropogenic sources impact the atmospheric environment and enter the soil through dry and wet atmospheric deposition, ultimately affecting human health. In this study, we established an emission inventory of Pb, As, Cr, and Cd in East Asia (80° E–140° E, 15° N–50° N) for the year 2017, including dust and anthropogenic sources from both land and marine. We modified the Community Multiscale Air Quality (CMAQ) model to provide gridded data on concentrations, as well as dry and wet atmospheric deposition fluxes of metals, with a focus on mainland China. The emissions of Pb, As, Cr, and Cd in East Asia were 19,253, 3415, 3332, and 9379 tons, respectively, in 2017, with 55%, 69%, 25%, and 58% distributed in the fine mode. The spatial distribution of atmospheric concentrations and dry deposition of trace metals was similar to that of emissions, while the spatial distribution of precipitation-related wet deposition was further east and greater in the south than in the north. In mainland China, the average bulk-deposition fluxes of Pb, As, Cr, and Cd were 1036.5, 170.3, 465.9, and 185.0 μg·m−2·year−1, respectively. Our study provides gridded data on trace metals in mainland China, which can be used for assessing air quality, human exposure risks, and metal inputs to soils. [ABSTRACT FROM AUTHOR]

Over the past century, atmospheric inorganic nitrogen (IN) deposition to terrestrial ecosystems has significantly increased and caused various environmental issues. China has been one of the hotspot regions for IN deposition, yet limited data exist regarding IN deposition fluxes in China at the regional scale. In this study, based on NO2 and NH3 columns acquired by satellite sensors, coupled with atmospheric chemical transport model (CTM), mixed-effects model and site observations, we constructed regional-scale IN dry and wet deposition models respectively, and finally proposed a spatially explicit database of IN deposition fluxes in China. The database includes the dry, wet and total deposition fluxes in China during 2011–2020, and the data are presented in raster form with a resolution of 0.25° × 0.25°. Overall, the database is of great importance for monitoring and simulating the trends of IN deposition over a long time series in China. [ABSTRACT FROM AUTHOR]

The Ediacaran–Cambrian (E-C) transition (∼542–517 Ma) witnessed the rapid evolution of Cambrian animals, which was accompanied by carbon cycling anomalies and a significant increase in the concentration of oxygen in Earth's atmosphere. The mechanisms stimulating the evolution of complex eukaryotes, however, remain problematic, especially concerning the link between biological evolution and contemporaneous changes in the oceanic environment. In this study, integrated δ13Ccarb–δ13Corg–δ15N compositions were analysed from the YD-4 core samples to understand redox fluctuations and nitrogen cycling of the middle Yangtze Block across the E-C transition. Two negative δ13Ccarb excursions (N1 and N2) and a positive δ13Ccarb excursion (P1) are identified from the studied samples and are supposedly of primary origin. Constrained by of the U-Pb age, biolithology and pattern of isotopic variation, N1, P1 and N2 are comparable to the Basal Cambrian Carbon Isotope Excursion (BACE), Zhujiaqing Carbon Isotope Excursion (ZHUCE) and Shiyantou Carbon Isotope Excursion (SHICE). We interpreted the decreased δ15N values in this study as resulting from intensified atmospheric nitrogen fixation driven by enhanced denitrification associated with expanded marine anoxia, as well as partial ammonium assimilation, while increased δ15N values suggest weakened denitrification associated with an amplified oxic water mass. The temporal coincidence of N1 and N2, with two episodes of negative δ15N excursions, and of P1, with a positive δ15N excursion, suggests that variable oceanic redox conditions and nitrogen bioavailability may have influenced the evolution of the Cambrian eukaryote-dominated community. [ABSTRACT FROM AUTHOR]

Background and aims: Potassium (K), Calcium (Ca), and magnesium (Mg) are essential nutrients for plant and animal growth. The ratio of K/(Ca + Mg) in forage is considered as an indicator of grass tetany. While atmospheric nitrogen (N) deposition is declining or projected to decline in many countries, it remains unknown whether historical N inputs would have legacy effects on K, Ca, and Mg nutrition in soil and plants. Methods: After the cessation of 6-yr N addition with wide-ranging rates, we measured the concentrations of K, Ca, and Mg in soil and plants in a temperate steppe of northern China during three successive years from 2016 to 2018. Results: Soil K/(Ca + Mg) ratios were increased by historical N addition across the three years. Soil K/(Ca + Mg) ratios were higher than 0.08, indicating potential occurrence of grass tetany for ruminants. Plant mineral concentrations and K/(Ca + Mg) ratios at the plant community level showed no variation with increasing historical N addition rates in all the three years, except for the increasing K and Ca concentrations in 2017. All plant functional types showed strong stoichiometric homeostasis with respect to nutrient concentrations, which contributed to the stable forage K/(Ca + Mg) ratio under the N-induced increasing soil K/(Ca + Mg) ratio. Conclusion: Our results highlight the critical role of stoichiometric homeostasis in maintaining forage non-N mineral nutrition of natural grasslands under the background of soil nutritional alterations. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Paleoproterozoic Jingshan Group marble displays a pronounced positive δ13C V-PDB. • The positive excursion appears to have been a response to the Lomagundi-Jatuli event. • The carbon isotope anomaly appears most pronounced in shallow marine deposits. • BIF and graphite deposits formed coeval with increasing atmospheric oxygen levels. The North China Craton, one of the oldest continental blocks in the world, comprises Paleoproterozoic metamorphic sedimentary formations that record the effects of multiple major events in early Earth history, including the Great Oxidation Event (GOE) and its consequent Lomagundi-Jatuli carbon isotope event (LJE). The lack of focused research on the geological record of LJE-equivalent rocks of the Jiaodong Peninsula, Shandong Province, eastern China, has hindered our understanding of the Precambrian atmospheric oxygen evolution recorded by rocks of the North China Craton. This paper considers carbon and oxygen isotope and trace element geochemical data recovered from marble deposits of the Paleoproterozoic Jingshan Group (2.20–1.90 Ga) of the Jiaolai Basin. The investigated strata display a pronounced positive δ13C V-PDB excursion greater than 4.2 ‰. δ13C V-PDB and δ18O V-SMOW values range from −3.7 ‰ to 5.4 ‰ and 4.5 ‰ to 18.7 ‰, respectively. Positive co-variance of carbon and oxygen isotope values of the analyzed Jingshan Group samples is interpreted to reflect the effects of metamorphism and water–rock reactions. Marble deposits of the Jingshan Group experienced recrystallization, metamorphism, and silicification resulting in strong decarbonation. High amphibolite facies metamorphism may have reduced δ13C V-PDB by 3 ‰ to 5 ‰. Thus, estimated original sedimentary δ13C V-PDB values of as great as +8.4 ‰ suggest the existence of a strong positive anomaly that may reflect the global Lomagundi-Jatuli event. Rare earth and other trace element geochemical results of the present study suggest that banded iron formation (BIF) deposits associated with the Jingshan Group marble formed in a redox stratified ocean in the Jiaolai Basin dominated by ferruginous conditions. Moreover, our results suggest that positive carbon isotope anomaly associated with the LJE is largely constrained to sediment deposited in shallow and coastal marine environments. [ABSTRACT FROM AUTHOR]

Due to the rapid development of industrialization and a substantial economy, China has become one of the global hotspots of nitrogen (N) and sulfur (S) deposition following Europe and the USA. Here, we developed a dataset with full coverage of N and S deposition from 2005 to 2020, with multiple statistical models that combine ground-level observations, chemistry transport simulations, satellite-derived vertical columns, and meteorological and geographic variables. Based on the newly developed random forest method, the multi-year averages of dry deposition of oxidized nitrogen (OXN), reduced nitrogen (RDN), and S in China were estimated at 10.4, 14.4, and 16.7 kg N/S ha -1 yr -1 , and the analogous numbers for total deposition were respectively 15.2, 20.2, and 25.9 kg N/S ha -1 yr -1 when wet deposition estimated previously with a generalized additive model (GAM) was included. The dry to wet deposition ratio (Rdry/wet) of N stabilized in earlier years and then gradually increased especially for RDN, while that of S declined for over 10 years and then slightly increased. The RDN to OXN deposition ratio (RRDN/OXN) was estimated to be larger than 1 for the whole research period and clearly larger than that of the USA and Europe, with a continuous decline from 2005 to 2011 and a more prominent rebound afterwards. Compared with the USA and Europe, a more prominent lagging response of OXN and S deposition to precursor emission abatement was found in China. The OXN dry deposition presented a descending gradient from east to west, while the S dry deposition a descending gradient from north to south. After 2012, the OXN and S deposition in eastern China declined faster than the west, attributable to stricter emission controls. Positive correlation was found between regional deposition and emissions, while smaller deposition to emission ratios (D/E) existed in developed eastern China, attributed to more intensive human activities and thereby anthropogenic emissions. [ABSTRACT FROM AUTHOR]

The soil microbiome is an important component of wetland ecosystems and plays a pivotal role in nutrient cycling and climate regulation. Nitrogen (N) addition influences the soil's microbial diversity, composition, and function by affecting the soil's nutrient status. The change in soil bacterial diversity and composition in temperate wetland ecosystems in response to high ammonium nitrogen additions remains unclear. In this study, we used high-throughput sequencing technology to study the changes of soil bacterial diversity and community structure with increasing ammonium concentrations [CK (control, 0 kg ha−1 a−1), LN (low nitrogen addition, 40 kg ha−1 a−1), and HN (high nitrogen addition, 80 kg ha−1 a−1)] at a field experimental site in the Sanjiang Plain wetland, China. Our results showed that except for soil organic carbon (SOC), other soil physicochemical parameters, i.e., soil moisture content (SMC), dissolved organic nitrogen (DON), total nitrogen (TN), pH, ammonium nitrogen (NH4+), and dissolved organic carbon (DOC), changed significantly among three ammonium nitrogen addition concentrations (p < 0.05). Compared to CK, LN did not change soil bacterial α-diversity (p > 0.05), and HN only decreased the Shannon (p < 0.05) and did not change the Chao (p > 0.05) indices of soil bacterial community. Ammonium nitrogen addition did not significantly affect the soil's bacterial community structure based on non-metric multidimensional scaling (NMDS) and PERMANOVA (ADONIS) analyses. Acidobacteriota (24.96–31.11%), Proteobacteria (16.82–26.78%), Chloroflexi (10.34–18.09%), Verrucomicrobiota (5.23–11.56%), and Actinobacteriota (5.63–8.75%) were the most abundant bacterial phyla in the soils. Nitrogen addition changed the complexity and stability of the bacterial network. SMC, NO3−, and pH were the main drivers of the bacterial community structure. These findings indicate that enhanced atmospheric nitrogen addition may have an impact on bacterial communities in soil, and this study will allow us to better understand the response of the soil microbiome in wetland ecosystems in the framework of increasing nitrogen deposition. [ABSTRACT FROM AUTHOR]

Due to the intense release of reactive nitrogen (Nr) from anthropogenic activity, the source layout of atmospheric nitrogen aerosol has changed. To comprehensively clarify the level, sources, and environmental fate of NH 4+ and NO 3- , their concentrations and stable isotopes (δ15 N) in fine particulate matter (PM 2.5) were measured in a subtropical megacity of South China. The inorganic nitrogen (NH 4+ and NO 3-) was an essential part of atmospheric nitrogen aerosol, and the N-NH 4+ and N-NO 3- contributed 45.8 % and 23.2 % to total nitrogen (TN), respectively. The source contributions of NH 4+ and NO 3- were estimated by δ15 N, suggesting that the dominant sources were from anthropogenic combustion activities, including coal combustion, biomass burning, and vehicles, contributing 63.2 % and 88.3 % to NH 4+ and NO 3- , respectively. In particular, biomass burning was the predominant source of NH 4+ (27.9 %), whereas coal combustion was the dominant source of NO 3- (40.4 %). This study emphasized the substantial impacts of human activities on inorganic Nr. With the rapid development of industry and transportation, nitrogen emissions will be even higher. The promotion of clean energy and efficient use of biomass would help to reduce nitrogen emissions and alleviate air pollution. [ABSTRACT FROM AUTHOR]

Introduction: Atmospheric nitrogen (N) deposition has often been considered as a driver of exotic plant invasions. However, most related studies focused on the effects of soil N levels, and few on those of N forms, and few related studies were conducted in the fields. Methods: In this study, we grew Solanum rostratum, a notorious invader in arid/semi-arid and barren habitats, and two coexisting native plants Leymus chinensis and Agropyron cristatum in mono- and mixed cultures in the fields in Baicheng, northeast China, and investigated the effects of N levels and forms on the invasiveness of S. rostratum. Results: Compared with the two native plants, S. rostratumhad higher aboveground and total biomass in both mono- and mixed monocultures under all N treatments, and higher competitive ability under almost all N treatments. N addition enhanced the growth and competitive advantage of the invader under most conditions, and facilitated invasion successof S. rostratum. The growth and competitive ability of the invader were higher under low nitrate relative to low ammonium treatment. The advantages of the invader were associated with its higher total leaf area and lower root to shoot ratio compared with the two native plants. The invader also had a higher light-saturated photosynthetic rate than the two native plants in mixed culture (not significant under high nitrate condition), but not in monoculture. Discussion: Our results indicated that N (especially nitrate) deposition may also promote invasion of exotic plants in arid/semi-arid and barren habitats, and the effects of N forms and interspecific competition need to be taken into consideration when studying the effects of N deposition on invasion of exotic plants. [ABSTRACT FROM AUTHOR]

Dramatic increases in global atmospheric N deposition have had adverse effects on inland water ecosystems. China is one of the three hot spots of N deposition in the world. In order to fully understand the impact of N deposition on inland waters in China and formulate a reasonable water pollution treatment plan, we need to clearly quantify the N deposition flux in inland water. Therefore, using the LMDZ-OR-INCA model combined with inland water area data, we obtained the dataset of inland water N deposition in China from the 1990s to the 2010s, which lays a foundation for further understanding the spatial-temporal pattern of inland water N deposition and its impact mechanisms. At the same time, we publicly share this dataset and provide online access and download services at https://ecodb.scidb.cn/detail?dataSetId=892431070195089408. [ABSTRACT FROM AUTHOR]

Given the interdependence of climate change (CLC) and urban expansion (URE) on ecosystem productivity in China and India, hybrid physics-based models were fitted in this study to evaluate the effects of these variables on photosynthetically active radiation (PAR). This was accomplished by interpolating the most recent five general circulation models (GCMs) from coupled model intercomparison project phase 6 (CMIP6) into the CMIP6 multi-ensemble model. The potential of PAR is projected to increase by 0.001 to 2.077% in China and by 0.002 to 6.737% in India, on a seasonal and annual basis, if the warming is kept at 1.5 °C from now until the end of this century. The effects of CLC and URE on the changes in PAR in China and India were investigated, and URE had a greater impact than CLC when compared to effective contributions, with 49.47% for China and 28.41% for India in the entire case scenario. In contrast, CLC and PAR residual factor (PRF) have a greater impact in India than in China, with effects of 13.79% and 57.79% compared to 0.89% and 49.64%, respectively. Preferences for exotic, high-productivity plant species, irrigation, CO2 fertilization, and nitrogen deposition are suggested as measures for replenishing PAR in both countries. [ABSTRACT FROM AUTHOR]

Forest canopies are the functional interface between ecosystem and the atmospheric nitrogen (N) deposition. However, the sources of spatio‐temporal variability and intra‐event variation of N deposition via throughfall (TF) remain ambiguous. Here, we analysed TF samples for concentrations and fluxes of ammonium (NH4+) and nitrate (NO3−) using an array of 20 fixed‐position collectors on an event and within event basis throughout the 2019 growing season in a Chinese pine plantation, Northern China. Results showed that the volume weighted mean concentrations of NH4+ and NO3− in TF were significantly higher than those in bulk precipitation (BP) during the study period. A canopy budget model indicated that canopy uptake was more dominant than dry deposition for NH4+, while the reverse was true for NO3−. This caused a comparable TF NH4+ flux but an enhanced TF NO3− fluxes compared to BP. The intra‐event trend and magnitude of TF NH4+ and NO3− concentrations were influenced by the antecedent dry period and rainfall intensity, and indicated that biological nitrification may occur in the canopies. In addition, due to the larger of canopy NH4+ uptake that counteracted the amplifying effect of dry deposition, the spatial variability of TF NH4+ concentration was significantly lower than that of TF NO3− concentration, and exhibited more temporal persistence. No relationship was found between the spatial distribution of TF NH4+ concentration and the TF amount, the distance to the nearest trunk, nor the canopy cover, whereas the TF NO3− concentration was significantly related to the TF amount and the canopy cover. These findings can enhance our understanding of N processes within canopies, and have important implications for evaluating the impacts of N deposition in forest ecosystems. [ABSTRACT FROM AUTHOR]

Abundant emissions have made China as one of the hotpots of atmospheric reactive nitrogen (Nr) deposition over the world. Here we conducted multi‐year simulation and explored the trend and interannual variations (IAVs) of China's Nr deposition for different forms (wet and dry) and species (oxidized and reduced nitrogen, OXN and RDN) during 2008–2017. Sensitivity analysis scenarios were applied to evaluate the roles of anthropogenic emissions and meteorological conditions on the changing deposition. The annual mean Nr deposition was simulated at 15.7 ± 0.9 kg N ha−1 yr−1 for China. Attributed mainly to the changing OXN, the trend in Nr deposition over the 10‐year period showed an inverted "V" pattern, reflecting the benefit of nation actions on NOX emissions controls. The standard deviation ellipse analysis suggested a clear interannual shift of spatial distribution of Nr deposition to the southwest during 2013–2017. Based on the mean absolute deviation (MAD) and absolute percent departure from the mean obtained in different simulation scenarios, the IAVs of Nr deposition were found to be driven mainly by the changing meteorological conditions, and the correlation coefficient between MADs of Nr deposition and precipitation reached 0.47. Relative to meteorological factor, the changing emissions could explain 61%–83% of 10‐year trend of Nr deposition for the concerned regions, thus were identified as the main driver of the trend. The changing meteorological conditions played a more important role on shaping the IAVs of Nr deposition, with the relative contributions estimated at 60% for the concerned regions. Plain Language Summary: Due to abundant anthropogenic emissions, China has been a hotspot of deposition of atmospheric reactive nitrogen (Nr), which exerts multiple ecological and environmental damages. During the past decade, China has been implementing aggressive actions of air pollution controls, leading to large changes in Nr emissions and thereby deposition. The evolution of Nr deposition as well as its major influencing factors is of great concern for both scientific community and policy makers. We conducted numeric simulation and geographic analysis, to explore the spatiotemporal change of Nr deposition and to separate the contributions of anthropogenic (emissions) and natural (meteorological conditions) to the change for 2008–2017. We found a clear growth of Nr deposition till 2012 followed by a decline afterward for the whole country, and unequal changes in different regions resulted in a shift to southwest for the spatial distribution of Nr deposition since 2012. The changing emissions were identified as the major contributor to the trend of Nr deposition, while meteorological conditions played a more important role on its interannual variation. The outcomes improve the understanding of driving forces of the changing Nr deposition in China, and reveal the effectiveness of national pollution controls on it. Key Points: Trend of annual Nr deposition during 2008–2017 showed an inverted "V" pattern, owing to the nation actions of NOX emission controlsThe spatial heterogeneity of the Nr deposition in China has been weakened, with the deposition gravity shifting to the southwestEmission change dominated the 10‐year trend of Nr deposition while meteorology played a more important role on its interannual variations [ABSTRACT FROM AUTHOR]

Purpose: The soil microbial community is an important bioactive component of terrestrial ecosystems. Its structural and functional diversity directly affects carbon and nitrogen processes. This study aimed to investigate the variations in the diversity and composition of soil bacterial communities in a wetland with different nitrogen deposition conditions. Methods: A long-term simulated nitrogen deposition experiment was conducted in the Ecological Locating Research Station of the Institute of Nature and Ecology of Heilongjiang Academy of Sciences. Three different treatments were evaluated, including low nitrogen (LK; 40 kg N·hm-2·a-1), high nitrogen (HN; 80 kg N·hm-2·a-1), and control (CK; 0 kg N·hm-2·a-1). Bacterial 16S rDNA was then sequenced and analyzed using the next-generation sequencing technology. Result: Higher levels of N deposition resulted in an α-diversity increase followed by a decrease, with significant reductions in the HN treatment. Simulated nitrogen deposition resulted in changes in the structure and abundance of bacterial communities in wetland soils. The dominant phyla in all three plots were Proteobacteria and Acidobacteria. Compared with CK, the relative abundance of Chloroflexi increased significantly under the HN treatment (P < 0.05), whereas the relative abundance of Firmicutes and Bacteroidetes decreased significantly (P < 0.05). Nitrogen input changed the composition and relative abundance of the bacterial community, which was possibly due to N-induced soil acidification. Conclusion: This study thus provides a theoretical basis for predicting the effects of atmospheric nitrogen deposition on soil microorganisms, as well as changes in the wetland ecosystem in Sanjiang Plain. [ABSTRACT FROM AUTHOR]

Increasing atmospheric nitrogen (N) deposition has a profound impact on the ecosystem functions and processes. Fine root decomposition is an important pathway for the reentry of nutrients into the soil. However, the effect of N addition on root decomposition and its potential mechanism is not well understood with respect to root branch orders. In this study, we conducted a 30-month decomposition experiment of fine roots under different concentrations of N addition treatments (0, 30, 60, and 90 kg N ha-1 year-1, respectively) in a typical Pinus massoniana plantation in the Three Gorges Reservoir Area of China. In the early stage of decomposition (0-18 months), N addition at all concentrations promoted the decomposition of fine roots, and the average decomposition rates of order 1-2, order 3-4, order 5-6 fine roots were increased by 13.54%, 6.15% and 7.96% respectively. In the late stage of decomposition (18-30 months), high N addition inhibited the decomposition of fine root, and the average decomposition rates of order 1-2, order 3-4, order 5-6 fine roots were decreased by 58.35%, 35.43% and 47.56% respectively. At the same time, N addition promoted the release of lignin, carbon (C), N, and phosphorus (P) in the early-stage, whereas high N addition inhibited the release of lignin, C, N, and the activities of lignin-degrading enzyme (peroxidase and polyphenol oxidase) in the late-stage. The decomposition constant (k) was significantly correlated with the initial chemical quality of the fine roots and lignin-degrading enzyme activities. The higher-order (order 3-4 and order 5-6) fine roots decomposed faster than lower-order (order 1-2) fine roots due to higher initial cellulose, starch, sugar, C concentrations and higher C/N, C/P, lignin/N ratios and lower N, P concentrations. In addition, low N (30 kg N ha-1 year-1) treatments decreased soil organic matter content, whereas high N (90 kg N ha-1 year-1) treatment had the opposite effect. All the N treatments reduced soil pH and total P content, indicating that increased N deposition may led to soil acidification. Our findings indicated that the effect of N addition on decomposition varied with the decomposition stages. The decomposition difference between the lowerorder and higher-order fine roots were controlled strongly by the initial chemical quality of the fine roots. This study provides new insights into understanding and predicting possible changes in plant root decomposition and soil properties in the future atmospheric N deposition increase scenarios. [ABSTRACT FROM AUTHOR]

Atmospheric wet deposition has attracted much attention because of its removal function of aerosol particles and impact on ecosystem. It is a complex multi‐component process due to various pollutants emission sources and reaction processes. However, traditional studies mainly focused on single components, ignoring the internal relationships and the comprehensive deposition level; this has hindered the comprehensive understanding and the assessment of ecological effects of deposition. Here, based on the monitoring of wet deposition across 52 stations during 2013–2018 in China, we used two novel multidimensional methods to investigate multi‐component atmospheric wet deposition: network analysis and comprehensive index. Network analysis is a new method that can help better explore the overall relationship between multiple components. We found that due to the improvement of human development level and the diversification of energy sources, the air pollutants sources became more diversified, which reduced the relationship between different deposition components and made the multi‐component deposition network looser. Comprehensive index is a method to realize the fusion of multiple parameters, which can explore the comprehensive effect of multi‐component atmospheric deposition on ecosystems. The high deposition comprehensive index occurred in the central and south China, and mainly influenced by human activities (energy consumption, fertilization, and vehicle ownership) and precipitation, which means that ecosystems in these regions are exposed to greater impacts by wet deposition. The findings provide new insights into understanding multi‐component atmospheric deposition and its comprehensive ecological effects. Plain Language Summary: Atmospheric wet deposition can not only remove aerosol particles, but also is an important way to input elements into the ecosystem. Systematic understanding of it can help us formulate effective environmental strategies and evaluate its ecological effects. It is complex, multi‐component process involving multiple emission sources and atmospheric reactions. However, studies have traditionally only examined single components of this process, and as such may have missed relationships and inter‐effects. In this study, based on monitoring of wet deposition across 52 stations in China, we analyzed the fluxes and spatial variations of 16 components and explored their internal relationships network (DRNs), while developing a comprehensive index (DCIs) using novel multi‐dimensional method. We found that the DRNs and DCIs both showed different spatial variation. The former were mainly affected by the energy structure and the level of human development, while the latter were affected by climate factors and the intensity of human activity. Our findings provide a new perspective for understanding multi‐component atmospheric deposition, and potential suggestions for evaluating its comprehensive ecological effects. Key Points: Multi‐component wet deposition was first quantified by multidimensional approachDiversified energy structures weakened deposition relationship networkHuman activity and climate influenced deposition comprehensive index [ABSTRACT FROM AUTHOR]

Foliar stable nitrogen (N) isotopes (δ15N) generally reflect N availability to plants and have been used to infer about changes thereof. However, previous studies of temporal trends in foliar δ15N have ignored the influence of confounding factors, leading to uncertainties on its indication to N availability. In this study, we measured foliar δ15N of 1811 herbarium specimens from 12 plant species collected in southern China forests from 1920 to 2010. We explored how changes in atmospheric CO2, N deposition and global warming have affected foliar δ15N and N concentrations ([N]) and identified whether N availability decreased in southern China. Across all species, foliar δ15N significantly decreased by 0.82‰ over the study period. However, foliar [N] did not decrease significantly, implying N homeostasis in forest trees in the region. The spatiotemporal patterns of foliar δ15N were explained by mean annual temperature (MAT), atmospheric CO2 (PCO2), atmospheric N deposition, and foliar [N]. The spatiotemporal trends of foliar [N] were explained by MAT, temperature seasonality, PCO2, and N deposition. N deposition within the rates from 5.3 to 12.6 kg N ha−1 year−1 substantially contributed to the temporal decline in foliar δ15N. The decline in foliar δ15N was not accompanied by changes in foliar [N] and therefore does not necessarily reflect a decline in N availability. This is important to understand changes in N availability, which is essential to validate and parameterize biogeochemical cycles of N. [ABSTRACT FROM AUTHOR]

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Nitrous oxide (N2O) is an influential greenhouse gas (GHG) and an unregulated ozone‐depleting substance. The extent to which N2O emissions from natural forest soils have been enhanced by high atmospheric nitrogen (N) deposition in China during past decades is unclear; however, assessing land‐related N2O emissions for 2060 national "carbon neutrality" goal is urgent. In this study, we proposed a "gray box" conceptual model and deduced a linear relationship between soil N2O emissions and N deposition on a large scale. On this basis, we created a "process‐augmented data‐driven" approach using which we combined experimental N addition data from 38 Chinese forests with N deposition observation data to estimate regional soil N2O emissions. We found that the N2O emission budget of eastern China forest soils averaged 0.24 ± 0.07 TgN yr−1 from 1996 to 2015; of this, ∼36% (0.087 TgN yr−1) was directly induced by N deposition. Soil N2O emission rates (RN2O) fluctuated slightly after 2006, and the RN2Os of different ecoregions were significantly different (p < 0.001). Soil factors and N‐deposition‐related factors dominated the spatial variation of RN2O. Our findings provide country‐specific and ecoregion‐specific emission factors for national GHG inventories in China. Our approach bridges the gap between site‐level experiments and demand for regional N2O emissions, and is applicable for estimating N2O emissions in other countries/regions. Meanwhile, more N addition experiments are needed to comprehensively understand N cycling processes and extend the predictive capability of the approach. Plain Language Summary: Nitrous oxide (N2O) is a greenhouse gas that is around 300 times more powerful than carbon dioxide. As many countries and regions are aiming to achieve zero net carbon emission ("carbon neutrality") by the mid‐21st century, we need to evaluate the emissions of nitrous oxide to build an accurate picture of the current situation. However, it is difficult to estimate the emission of N2O from natural soils because the spatial variation is high. Inspired by the linkage between elemental nitrogen (N) that enters an ecosystem and N that leaves the ecosystem, we proposed a conceptual model and deduced a linear relationship between N deposition and soil N2O emissions. On the basis, we used experimental N addition data from various sites to quantify the linear relationship. Then, the N2O emission and its variation was estimated with dynamic N deposition data. In eastern China forests where the N deposition rate is exceptionally high, around 0.24 million tons of N2O‐N was emitted annually from 1996 to 2015, around 36% of which was directly induced by N deposition. From another perspective, soil N2O emissions in this region are expected to decline owing to pollution control practices and decreasing N deposition. Key Points: Eastern China forest soils emitted 0.24 TgN2O‐N yr−1 from 1996 to 2015N deposition directly induced ∼36% of emitted N2O from eastern China forest soilsDirect contribution of N deposition to soil N2O emissions increased from tropical to boreal forests [ABSTRACT FROM AUTHOR]

Acid forest soils in South China experience a chronically elevated input of atmospheric nitrogen (N), turning them into hot spots for gaseous N emissions. Soil moisture is known to be a major controller for the partitioning of gaseous N loss to nitric (NO) and nitrous oxide (N2O), which may be of particular relevance in the monsoonal climate of South China. To study this partitioning in more detail, we determined gas phase kinetics of NO and N2O release during laboratory dry-out of acidic surface soils from the headwater catchment TieShanPing (TSP), situated close to Chongqing, SW China. Soils were sampled from two hydrologically distinct environments, a well-drained hill slope (HS), and a periodically flooded groundwater discharge zone (GDZ). Production and consumption of NO were studied in an automated flow-through system purged with NO-free or NO-spiked air. Production rates peaked at 21% and 18% water filled pore space (WFPS) in HS and GDZ soils, respectively, suggesting nitrification as the dominant process of NO formation in both landscape units. In HS soils, maximum production and consumption occurred at the same WFPS, whereas GDZ soils displayed maximum NO consumption at higher WFPS than maximum production, suggesting that denitrification is an important NO sink in GDZ soils. Net N2O release was largest at 100% WFPS and declined steadily during drying. Integrated over the entire range of soil moisture, potential NO-N loss outweighed potential N2O-N loss, suggesting that N-saturated, acid forest soil is an important NO source. [ABSTRACT FROM AUTHOR]

Upland forest soil is an important CH4 sink that plays a key role in climate change mitigation. China features large areas of various types of forest, but spatiotemporal variation in CH4 flux has not yet been clarified. Here, we analyzed variation in CH4 flux and the effects of environmental variables on the CH4 flux of forest in China using in situ observational data. Upland forest soil absorbed CH4 at a rate of 0.24 ± 0.02 g m−2 yr−1. The CH4 uptake rate (0.46 ± 0.10 g m−2 yr−1) of warm temperate deciduous broad-leaved forest was the highest. Soil alkali-hydrolyzable nitrogen was the only factor significantly correlated with CH4 uptake variation among vegetation zones. A break point in CH4 uptake over the study period (from 1997 to 2020) was detected in 2015. CH4 uptake slightly decreased until 2015 and increased after 2015. The mean CH4 uptake of the period after 2015 (0.44 ± 0.07 g m−2 yr−1) was significantly higher than that before 2015 (0.20 ± 0.02 g m−2 yr−1). Atmospheric nitrogen deposition was negatively related to interannual CH4 uptake. Our findings suggest that the CH4 uptake of upland forest soil will continue to increase over the next few decades as China accelerates efforts to achieve its carbon neutrality goal, and this would result in continuous decreases in nitrogen deposition through various pathways. [ABSTRACT FROM AUTHOR]

Relationships between oceanic emissions and air chemistry are intricate and still not fully understood. For regional air chemistry, a better understanding of marine halogen emission on the hydroxyl (OH) radical is crucial. The OH radical is a key species in atmospheric chemistry because it can oxidize almost all trace species in the atmosphere. In the marine atmosphere, OH levels could be significantly affected by the halogen species emitted from the ocean. However, due to the complicated interactions of halogens with OH through different pathways, it is not well understood how halogens influence OH and even what the sign of the net effect is. Therefore, in this study, we aim to quantify the impact of marine-emitted halogens (including Cl, Br, and I) through different pathways on OH in the high OH season by using the WRF-CMAQ model with process analysis and state-of-the-art halogen chemistry in East Asia and near the western Pacific. Results show a very complicated response of the OH production rate (P OH) to marine halogen emissions. The monthly P OH is generally decreased over the ocean by up to a maximum of about 10 %–15 % in the Philippine Sea, but it is increased in many nearshore areas by up to about 7 %–9 % in the Bohai Sea. In the coastal areas of southern China, the monthly P OH could also decrease 3 %–5 %, but hourly values can decrease over 30 % in the daytime. Analysis of the individual reactions using the integrated reaction rate shows that the net change in P OH is controlled by the competition of three main pathways (OH from O 3 photolysis, OH from HO 2 conversion, and OH from HO X , X=Cl , Br, I) through different halogen species. Sea spray aerosol (SSA) and inorganic iodine gases are the major species influencing the strengths of these three pathways and therefore have the most significant impacts on P OH. Both of these two types of species decrease P OH through physical processes, while generally increasing P OH through chemical processes. In the ocean atmosphere, inorganic iodine gases determine the basic pattern of Δ P OH through complicated iodine chemistry, which generally positively influences P OH near O 3 sources while negatively influencing it when O 3 experiences longer transport over the ocean. Over the continent, SSA is the controlling species, and the SSA extinction effect leads to the negative Δ P OH in southern China. Our results show that marine-emitted halogen species have notable impacts over the ocean and potential impacts on coastal atmospheric oxidation by species (SSA, inorganic iodine, and halocarbons), processes (chemistry, radiation, and deposition), and main pathways. The notable impacts of the marine-emitted halogen species on the atmospheric oxidation capacity have further implications for the lifetime of long-lived species such as CH 4 in the long term and the quantity of air pollutants such as O 3 in the episodic events in East Asia and in other circumstances (e.g., different domains, regions, and emission rates). [ABSTRACT FROM AUTHOR]

Belowground plant traits play important roles in plant diversity loss driven by atmospheric nitrogen (N) deposition. However, the way N enrichment shapes plant microhabitats by patterning belowground traits and finally determines aboveground responses is poorly understood. Here, we investigated the rhizosheath trait of 74 plant species in seven N‐addition simulation experiments across multiple grassland ecosystems in China. We found that rhizosheath formation differed among plant functional groups and contributed to changes in plant community composition induced by N enrichment. Compared with forb species, grass and sedge species exhibited distinct rhizosheaths; moreover, grasses and sedges expanded their rhizosheaths with increasing N‐addition rate which allowed them to colonize belowground habitats. Grasses also shaped a different microenvironment around their roots compared with forbs by affecting the physicochemical, biological, and stress‐avoiding properties of their rhizosphere soil. Rhizosheaths act as a "biofilm‐like shield" by the accumulation of protective compounds, carboxylic anions and polysaccharides, determined by both plants and microorganisms. This enhanced the tolerance of grasses and sedges to stresses induced by N enrichment. Conversely, forbs lacked the protective rhizosheaths which renders their roots sensitive to stresses induced by N enrichment, thus contributing to their disappearance under N‐enriched conditions. This study uncovers the processes by which belowground facilitation and trait matching affect aboveground responses under conditions of N enrichment, which advances our mechanistic understanding of the contribution of competitive exclusion and environmental tolerance to plant diversity loss caused by N deposition. [ABSTRACT FROM AUTHOR]

Nitrate aerosol plays an increasingly important role in wintertime haze pollution in China. Despite intensive research on wintertime nitrate chemistry in recent years, quantitative constraints on the formation mechanisms of nitrate aerosol in the Yangtze River Delta (YRD), one of the most developed and densely populated regions in eastern China, remain inadequate. In this study, we identify the major nitrate formation pathways and their key controlling factors during the winter haze pollution period in the eastern YRD using 2-year (2018–2019) field observations and detailed observation-constrained model simulations. We find that the high atmospheric oxidation capacity, coupled with high aerosol liquid water content (ALWC), made both the heterogeneous hydrolysis of dinitrogen pentoxide (N 2 O 5) and the gas-phase OH oxidation of nitrogen dioxide (NO 2) important pathways for wintertime nitrate formation in this region, with contribution percentages of 69 % and 29 % in urban areas and 63 % and 35 % in suburban areas during the haze pollution episodes, respectively. We further find that the gas-to-particle partitioning of nitric acid (HNO 3) was very efficient so that the rate-determining step in the overall formation process of nitrate aerosol was the oxidation of NO x to HNO 3 through both heterogeneous and gas-phase processes. The atmospheric oxidation capacity (i.e., the availability of O 3 and OH radicals) was the key factor controlling the production rate of HNO 3 from both processes. During the COVID-19 lockdown (January–February 2020), the enhanced atmospheric oxidation capacity greatly promoted the oxidation of NO x to nitrate and hence weakened the response of nitrate aerosol to the emission reductions in urban areas. Our study sheds light on the detailed formation mechanisms of wintertime nitrate aerosol in the eastern YRD and highlights the demand for the synergetic regulation of atmospheric oxidation capacity and NO x emissions to mitigate wintertime nitrate and haze pollution in eastern China. [ABSTRACT FROM AUTHOR]

In this study, a total of 26 surface sediments samples are collected from the Liao River estuary wetland, China. The concentration, potential ecological risk, and source apportionment of potentially toxic metals including Sr, Zn, Cr, Ni, Pb, Cu, and As in different seasons are analyzed. The average concentrations of potentially toxic metals are below the first class of Chinese marine sediment quality standard. There is no significant difference in the concentrations of potentially toxic metals in the sediments collected in June and November. The concentrations of potentially toxic metals in the periphery of the nature reserve are higher than those in the core area of the nature reserve. The average enrichment factors of As, Pb, Cu, Ni, Zn, and Cr are about 1, classified as minimal enrichment. The average enrichment factor of Sr is >2, which corresponds to moderate enrichment. The individual (Er) and total potential ecological risks (RI) of potentially toxic metals are low. The positive matrix factorization model suggested that the potentially toxic metals in surface sediments in June are dominantly from atmospheric deposition, industrial discharges, natural sources, and traffic emission. However, the traffic emission source is replaced by agricultural production and metal smelting activities in November. [ABSTRACT FROM AUTHOR]

Aims Atmospheric nitrogen (N) deposition influences tree hydraulic architecture and thus the growth and survival; but the responses of leaf hydraulic traits remain uncertain, and may vary with species or plant functional types. Methods We used the 16-year N addition experiment (10 g N m−2 year−1) on Fraxinus mandshurica (ash, broadleaf angiosperm) and Larix gmelinii (larch, conifer gymnosperm) plantations in northeastern China and examined the effect of N addition on their leaf hydraulics. We measured the leaf pressure–volume traits by the bench drying method and quantified the maximum leaf hydraulic conductance (K leaf_max) and resistance to embolism (P 50leaf) by the timed rehydration method. Important Findings Larch had higher K leaf_max and stronger drought tolerance (i.e. lower relative water content at turgor loss point (RWCtlp) and modulus of elasticity (ε), and more negative P 50leaf) than ash. N addition increased the leaf osmotic potential at turgor loss (π tlp) and full turgor (π 0), and leaf capacitance (C leaf_mass) for ash but not for larch, indicating that ash is more sensitive to N addition. N addition consistently increased K leaf_max and P 50leaf values for both species. π tlp and π 0 were positively while C leaf_mass was negatively correlated with leaf density (LD) for ash. K leaf_max was positively but P 50leaf was negatively related with LD for larch. There were negative relationships between K leaf_max and P 50leaf for both species. Overall, our findings suggest that long-term N addition decreases the leaf drought tolerance for these two important tree species, which improve the understanding of the tree hydraulic performance under N deposition. [ABSTRACT FROM AUTHOR]

Background: China has been increasingly subject to significant acid rain, which has negative impacts on forest ecosystems. Recently, the concentrations of NO3− in acid rain have increased in conjunction with the rapid rise of nitrogen deposition, which makes it difficult to precisely quantify the impacts of acid rain on forest ecosystems. Methods: For this study, mesocosm experiments employed a random block design, comprised of ten treatments involving 120 discrete plots (0.6 m × 2.0 m). The decomposition of fine roots and dynamics of nutrient loss were evaluated under the stress of three acid rain analogues (e.g., sulfuric (SO42−/NO3− 5:1), nitric (1:5), and mixed (1:1)). Furthermore, the influences of soil properties (e.g., soil pH, soil total carbon, nitrogen, C/N ratio, available phosphorus, available potassium, and enzyme activity) on the decomposition of fine roots were analyzed. Results: The soil pH and decomposition rate of fine root litter decreased when exposed to simulated acid rain with lower pH levels and higher NO3− concentrations. The activities of soil enzymes were significantly reduced when subjected to acid rain with higher acidity. The activities of soil urease were more sensitive to the effects of the SO42−/NO3− (S/N) ratio of acid rain than other soil enzyme activities over four decomposition time periods. Furthermore, the acid rain pH significantly influenced the total carbon (TC) of fine roots during decomposition. However, the S/N ratio of acid rain had significant impacts on the total nitrogen (TN). In addition, the pH and S/N ratio of the acid rain had greater impacts on the metal elements (K, Ca, and Al) of fine roots than did TC, TN, and total phosphorus. Structural equation modeling results revealed that the acid rain pH had a stronger indirect impact (0.757) on the decomposition rate of fine roots (via altered soil pH and enzyme activities) than direct effects. However, the indirect effects of the acid rain S/N ratio (0.265) on the fine root decomposition rate through changes in soil urease activities and the content of litter elements were lower than the pH of acid rain. Conclusions: Our results suggested that the acid rain S/N ratio exacerbates the inhibitory effects of acid rain pH on the decomposition of fine root litter. [ABSTRACT FROM AUTHOR]

Anthropogenic nitrogen (N) emissions and deposition have been increasing over past decades. However, spatiotemporal variations of N deposition levels and major sources remain unclear in many regions, which hinders making strategies of emission mitigation and evaluating effects of elevated N deposition. By investigating moss N contents and δ15N values in southwestern (SW) China in 1954–1964, 1970–1994, and 2005–2015, we reconstructed fluxes and source contributions of atmospheric ammonium (NH4+) and nitrate (NO3‐) deposition and evaluated their historical changes. For urban and non‐urban sites, averaged moss N contents did not differ between 1954–1964 and 1970–1994 (1.2%–1.3%) but increased distinctly in 2005–2015 (1.6%–2.3%), and averaged moss δ15N values decreased from +0.4‰ to +3.3‰ in 1954–1964 to −1.9‰ to −0.7‰ in 1974–1990, and to −4.8‰ to −3.6‰ in 2005–2015. Based on quantitative estimations, N deposition levels from the 1950s to the 2000s did not change in the earlier 20 years but were elevated substantially in the later 30 years. Moreover, the elevation of NH4+ deposition (by 12.2 kg‐N/ha/year at urban sites and 4.6 kg‐N/ha/year at non‐urban sties) was higher than that of NO3‐ deposition (by 6.0 and 2.9 kg‐N/ha/year, respectively) in the later 30 years. This caused a shifted dominance from NO3‐ to NH4+ in N deposition. Based on isotope source apportionments, contributions of combustion‐related NH3 sources (vehicle exhausts, coal combustion, and biomass burning) to the elevation of NH4+ deposition were two times higher than volatilization NH3 sources (wastes and fertilizers) in the later 30 years. Meanwhile, non‐fossil fuel NOx sources (biomass burning, microbial N cycles) contributed generally more than fossil fuel NOx sources (vehicle exhausts and coal combustion) to the elevation of NO3‐ deposition. These results revealed significant contributions of combustion‐related NH3 and non‐fossil fuel NOx emissions to the historical elevation of N deposition in SW China, which is useful for emission mitigation and ecological effect evaluation of atmospheric N loading. [ABSTRACT FROM AUTHOR]

Litter decomposition is a vital link between material circulation and energy flow in forest ecosystems and is intensely affected by global change factors, such as increased nitrogen (N) deposition and altered precipitation regimes. As essential nutrients, calcium (Ca), magnesium (Mg), and manganese (Mn) play crucial roles in plant energy metabolism, photosynthesis, and membrane transport of plants, and the major source of these nutrients is litter decomposition. However, the dynamics of Ca, Mg, and Mn during decomposition have been largely ignored. Thus, to better understand Ca, Mg, and Mn dynamics during leaf litter decomposition in the scenario of increasing N deposition and decreasing precipitation, we carried out a two-year field litterbag experiment in a natural evergreen broad-leaved forest in the central area of the rainy area of Western China. Two levels of N deposition (ambient N deposition and 150 kg·N·ha−1·y−1) and precipitation reduction (no throughfall reduction and 10% throughfall reduction) were set, i.e., control (Ctr: without nitrogen deposition or throughfall reduction), N deposition (N, 150 kg·N·ha−1·y−1), throughfall reduction (T, 10% throughfall reduction), and N deposition and throughfall reduction (NT, 150 kg·N·ha−1·y−1 and 10% throughfall reduction). We found that leaf litter Ca concentration increased in the early decomposition stage and then decreased, while Mg and Mn concentrations generally decreased during the whole period of decomposition. The amount of Ca showed an accumulation pattern, while Mg and Mn generally showed a release pattern. N deposition and throughfall reduction affected the Ca, Mg, and Mn dynamics, varying with different decomposition stages; i.e., N deposition significantly affected the concentration and amount of Ca, regardless of the decomposition stages, while throughfall reduction significantly affected the Ca concentration in the whole and early decomposition stages. N deposition significantly affected the concentration and amount of Mg in the whole and early decomposition stages, while throughfall reduction had no significant effects. Throughfall reduction significantly affected the concentration and amount of Mn in the whole and late decomposition stages, while N deposition had no significant effects. Ca concentration generally showed a significant positive linear relationship with mass loss in the early decomposition stage; Mg concentration showed a significant positive linear relationship with mass loss in the Ctr and N treatments in the early and late decomposition stages; Mn generally showed a significant negative linear relationship with mass loss, regardless of the decomposition stage. Overall, the results suggest that Ca accumulation is more likely affected by N deposition, while Mg and Mn releases are more likely affected by N deposition combined with throughfall reduction, particularly in the early decomposition stage. [ABSTRACT FROM AUTHOR]