Net Ecosystem Production Research Articles

Climate-Smart Drip Irrigation with Fertilizer Coupling Strategies to Improve Tomato Yield, Quality, Resources Use Efficiency and Mitigate Greenhouse Gases Emissions

Background: Integrated water and fertilizer management is important for promoting the sustainable development of agriculture. Climate-smart drip irrigation with fertilizer coupling strategies plays an important role to mitigate greenhouse gas emissions, ensuring food production, and alleviating water scarcity and excessive use of fertilizers. Methods: The greenhouse experiment consists of three drip irrigation treatments which include D1: drip irrigation (100 mm); D2: drip irrigation (200 mm); D3: drip irrigation (300 mm) under three different fertilizer management practices N1: nitrogen level (150 kg N ha−1); N2: nitrogen level (300 kg N ha−1); N3: nitrogen level (450 kg N ha−1). Results: The results showed that significantly improved soil moisture contents, quality and tomato yield, while reduced (38.6%) greenhouse gas intensity (GHGI) under the D3N3 treatment. The D2 and D3 drip irrigation treatments with 450 kg nitrogen ha−1 considerably improved NH4+-N contents, and NO3−-N contents at the fruit formation stage. The improve in net primary productivity (NPP), net ecosystem productivity (NEP), evapotranspiration (ET), and ecosystem crop water productivity (CWPeco) through D3N3 treatment is higher. The D3N3 treatment improved (28.2%) the net global warming potential (GWP), but reduced GHGI, due to improved (18.4%) tomato yield. The D3N3 treatment had significantly greater irrigation water productivity (IWP) (42.8%), total soluble sugar (TSS) (32.9%), vitamin C content (VC) (39.2%), soluble sugar content (SSC) (44.2%), lycopene content (41.3%) and nitrogen use efficiency (NUE) (52.4%), as compared to D1N1 treatment. Conclusions: Therefore, in greenhouse experiments, the D3N3 may be an effective water-saving and fertilizer management approach, which can improve WUE, tomato yield, and quality while reducing the effect of global warming.

An Assessment of the Carbon Budget of the Passively Restored Willow Forests Along the Miho River, Central South Korea

Climate change is rapidly progressing as the carbon budget balance is broken due to excessive energy and land use. This study was conducted to find and quantify new carbon sinks to implement the carbon neutrality policy prepared by the international community to solve these problems. To reach this goal, an allometric equation of the willow community, which dominates riparian vegetation, was developed and applied to calculate the net primary productivity of the willow community. Furthermore, after the amount of carbon emitted via soil respiration was quantified, the net ecosystem production was calculated by subtracting the amount of soil respiration from the net primary productivity. In comparisons of the results obtained via this process with those obtained from forest vegetation, the willow community, representative of riparian vegetation, showed a much higher carbon sequestration rate than forest vegetation. Considering these results comprehensively, the willow community could be a new and significant carbon absorption source. In this context, proper river restoration should be realized to contribute to carbon neutrality and secure various ecosystem service functions.

Predicting daily net ecosystem production in shallow lakes from dissolved oxygen saturation levels: a pan-European mesocosm experiment and modelling approach

Predicting daily net ecosystem production in shallow lakes from dissolved oxygen saturation levels: a pan-European mesocosm experiment and modelling approach

Linking Vegetation Phenology to Net Ecosystem Productivity: Climate Change Impacts in the Northern Hemisphere Using Satellite Data

With global climate change, linking vegetation phenology with net ecosystem productivity (NEP) is crucial for assessing vegetation carbon storage capacity and predicting terrestrial ecosystem changes. However, there have been few studies investigating the relationship between vegetation phenology and NEP in the middle and high latitudes of the Northern Hemisphere. This study comprehensively analyzed vegetation phenological changes and their climate drivers using satellite data. It also investigated the spatial distribution and climate drivers of NEP and further analyzed the sensitivity of NEP to vegetation phenology. The results indicated that the average land surface phenology (LSP) was dominated by a monotonic trend in the study area. LSP derived from different satellite products and retrieval methods exhibited relatively consistent responses to climate. The average SOS and POS for different retrieval methods showed a higher negative correlation with nighttime temperatures compared to daytime temperatures. The average EOS exhibited a higher negative correlation with daytime temperatures than a positive correlation. The correlations between VPD and the average SOS, POS, and EOS showed that the proportion of negative correlations was higher than that of positive correlations. The average annual NEP ranged from 0 to 1000 gC·m−2. The cumulative trends of NEP were mainly monotonically increasing, accounting for 61.04%, followed by monotonically decreasing trends, which accounted for 17.95%. In high-latitude regions, the proportion of positive correlation between VPD and NEP was predominant, while the proportion of negative correlation was predominant in middle-latitude regions. The positive and negative correlations between soil moisture and NEP (48.08% vs. 51.92%) were basically consistent in the study area. The correlation between SOS and POS with NEP was predominantly negative. The correlation between EOS and NEP was overall characterized by a greater proportion of negative correlations than positive correlations. The correlation between LOS and NEP exhibited a positive relationship in most areas. The sensitivity of NEP to vegetation phenological parameters (SOS, POS, and EOS) was negative, while the sensitivity of NEP to LOS was positive (0.75 gC·m−2/d for EVI vs. 0.63 gC·m−2/d for LAI vs. 0.30 gC·m−2/d for SIF). This study provides new insights and a theoretical basis for exploring the relationship between vegetation phenology and NEP under global climate change.

Divergent responses of carbon fluxes to elevated temperature and precipitation: A meta-analysis in North Hemisphere grassland ecosystems

The manipulation experiments involving increased precipitation and elevated temperature have elucidated a series of responses to the carbon fluxes (gross ecosystem productivity (GEP), ecosystem respiration (ER), and net ecosystem productivity (NEP)) in grassland ecosystems. It is still unclear how the duration, magnitude or local climate conditions of these manipulation experiments can affect the response of GEP, ER, and NEP. Here, we conducted a meta-analysis using data from 50 published studies that manipulated precipitation or temperature, while measuring GEP, ER, and NEP in North Hemisphere grassland ecosystems. The results showed that increased precipitation significantly increased the GEP and ER of grassland ecosystems in the Northern Hemisphere, with an average increase of 9.8% and 12.5% respectively. In contrast to increased precipitation, warming did not have a significant effect on GEP and ER. Meantime, there was no significant response of the NEP to both elevated temperature and increased precipitation. Furthermore, we found that the responses of carbon fluxes in North Hemisphere grassland ecosystems were associated with the magnitude and duration of increased precipitation, as well as to local temperature and precipitation changes induced by increased precipitation and elevated temperature. GEP was positively correlated with the local temperature under warming and increased precipitation. These findings emphasize the divergent response of carbon fluxes to climate factors change such as temperature and precipitation in North Hemisphere grassland ecosystems, which helps us better protect grasslands and predict ecosystem functions in the future.

Response of bottom dissolved oxygen reduction to net ecosystem production observed by a wave-driven profiler in the Changjiang River Plume

Coastal hypoxia, exacerbated by the combined influence of eutrophication and global warming, presents a significant environmental challenge. However, the lag correlation between organic matter (OM) export from the upper layers and bottom dissolved oxygen (DOBOT) reduction still lack clear elucidation. This study investigated the coupling between net ecosystem production (NEP, representing the maximum OM export) and DOBOT in the Changjiang River plume (CRP), using a wave-driven profiler system. The high-resolution profiles revealed rhythmic fluctuations in water column NEP, with sediment-water exchange (−74.6%) and NEP (−4.0%) dominating DOBOT reduction. Notably, surface NEP impacts DOBOT with a lag time of 25.65 h, indicating an OM sinking speed of 1.32 mm s−1. NEP at a depth of 3.4 m exerted the most significant influence on DOBOT, explaining a 12% reduction. These findings elucidate the response mechanism of DOBOT reduction to upper OM export and provide insights for hypoxia prediction in coastal and estuarine areas.

No-Tillage Treatment with Total Green Manure Mulching Reduces Soil Respiration by Regulating Soil Water Content Affecting Heterotrophic Respiration

Green manure is widely applied in agricultural production due to its beneficial soil modification and fertilization effects. However, the mechanisms underlying the effects of green manure return methods on soil respiration (Rs) and its components remain unclear. This study aimed to investigate the effects of green manure return methods on Rs in maize fields by quantifying Rs levels. A field experiment was conducted from 2021 to 2023 in the inland river oasis irrigation area of Gansu, with five treatment conditions: tillage with a full quantity of green manure incorporated into the soil (TG), no tillage with a full quantity of green manure mulched on the soil surface (NTG), tillage with roots incorporated into the soil and above-ground green manure removed (T), no tillage with above-ground manure removed (NT), and conventional tillage and leisure (CT). The results showed that, compared with CT, the NTG treatment increased the maize grain yield while reducing the soil heterotrophic respiration rate (Rh) by 8.5–9.8% and Rs by 6.7–8.7%, but did not significantly affect the soil autotrophic respiration rate (Ra), and decreased the carbon emission efficiency (CEE) by 20.8–25.6%. The increase in the soil water content (SWC) significantly reduced Rh during all growth periods, which was the primary factor in the reduction of Rs. Additionally, the net ecosystem productivity carbon sequestration (NEP-C) of the farmland ecosystem was positive under this system, indicating that the soil acts as a carbon “sink”. Therefore, a no-tillage treatment with a full quantity of green manure mulched on the soil surface can be used as a reasonable green manure return method to reduce carbon emissions from farmland in arid oasis irrigation regions.

Multiple-Win Effects and Beneficial Implications from Analyzing Long-Term Variations of Carbon Exchange in a Subtropical Coniferous Plantation in China

To improve our understanding of the carbon balance, it is significant to study long-term variations of all components of carbon exchange and their driving factors. Gross primary production (GPP), respiration (Re), and net ecosystem productivity (NEP) from the hourly to the annual sums in a subtropical coniferous forest in China during 2003–2017 were calculated using empirical models developed previously in terms of PAR (photosynthetically active radiation), and meteorological parameters, GPP, Re, and NEP were calculated. The calculated GPP, Re, and NEP were in reasonable agreement with the observations, and their seasonal and interannual variations were well reproduced. The model-estimated annual sums of GPP and Re over 2003–2017 were larger than the observations of 11.38% and 5.52%, respectively, and the model-simulated NEP was lower by 34.99%. The GPP, Re, and NEP showed clear interannual variations, and both the calculated and the observed annual sums of GPPs increased on average by 1.04% and 0.93%, respectively, while the Re values increased by 4.57% and 1.06% between 2003 and 2017. The calculated and the observed annual sums of NEPs/NEEs (net ecosystem exchange) decreased/increased by 1.04%/0.93%, respectively, which exhibited an increase of the carbon sink at the experimental site. During the period 2003–2017, the annual averages of PAR and the air temperature decreased by 0.28% and 0.02%, respectively, while the annual average water vapor pressure increased by 0.87%. The increase in water vapor contributed to the increases of GPP, Re, and NEE in 2003–2017. Good linear and non-linear relationships were found between the monthly calculated GPP and the satellite solar-induced fluorescence (SIF) and then applied to compute GPP with relative biases of annual sums of GPP of 5.20% and 4.88%, respectively. Large amounts of CO2 were produced in a clean atmosphere, indicating a clean atmospheric environment will enhance CO2 storage in plants, i.e., clean atmosphere is beneficial to human health and carbon sink, as well as slowing down climate warming.

Long-term alien marsh grass in China brings high carbon uptake capacity but cannot sustain high-temperature weather

Coastal wetlands, crucial in the global carbon cycle, face increasing challenges brought by extreme climate events, particularly high temperatures above plant tolerance thresholds. These conditions often exert great impact on plant, thereby potentially reducing overall ecosystem productivity. However, it has been observed that alien species, typically exhibiting higher productivity compared to native plant. Would plant invasion offset the loss of productivity caused by high-temperature events at ecosystem scale? In this study, we utilized data from 2020 to 2023 in China's Yangtze Estuary to investigate the responses of Spartina alterniflora (alien) and Phragmites australis (native) to high-temperature stress. Our results demonstrate that though the alien vegetation exhibits higher productivity before high temperature events, it experiences significant declines during high temperatures. In average, net ecosystem productivity (NEP) and gross primary productivity (GPP) of alien plant drops by 21.03% overall, with a notable 29.59% reduction during Neap tide. In contrast, native vegetation maintains a more stable productivity profile under the same conditions. Spring tide alleviate the negative impact of high temperatures on the alien vegetation, exhibiting a distinct environmental buffering effect. Photosynthetic photon flux density emerged as a crucial factor driving productivity, yet its effectiveness was moderated by aerodynamic conductance for heat transfer (Ga_h). Through the application of the Michaelis-Menten model, we confirmed that both species maintain similar maximum light utilization efficiencies, yet native vegetation demonstrates greater resilience to thermal stress. Additionally, we observed a 33.82% overestimation in productivity by the vegetation photosynthesis model (VPM) under high temperatures, emphasizing the need to refine how Ga_h impacts are integrated, particularly when comparing the resilience of native and alien species. We emphasize necessity of incorporating canopy structure factors into ecological models and underscore the importance of maintaining tidal dynamics for coastal wetland management.

Assessing and explaining rising global carbon sink capacity in karst ecosystems

Global karst vegetation is crucial for carbon sequestration and biodiversity conservation. However, research on the carbon sink capacity of vegetation and its potential driving mechanisms across different geographic types of global karst remains scant. This research delineates the trend characteristics and differences of net primary productivity (NPP), heterotrophic respiration (Rh), and net ecosystem productivity (NEP) across various bedrock and climatic zones within global karst landscapes. Extreme Gradient Boosting (XGBoost), Shapley Additive Explanations (SHAP), Neural Network fitting, and Partial Least Squares Structural Equation Modeling were utilized to investigate the nonlinear impacts and underlying mechanisms exerted by the explanatory variables on NPP, Rh, and NEP. The findings indicate that from 1981 to 2019, the rates of increase in NPP (2.02 gC·m⁻2 yr⁻1), Rh (1.47 gC·m⁻2 yr⁻1), and NEP (0.54 gC·m⁻2 yr⁻1) were marginally higher in global karst regions compared to non-karst areas. Additionally, when contrasted with various bedrock types, the differences in mean values and trends of these three indicators were more pronounced across different climatic zones of karst areas. XGBoost effectively captures the nonlinear relationship between NEP and its explanatory variables, while SHAP provides a detailed explanation of the contribution and interaction of these variables. The leaf area index (LAI) was the major contributor to NEP. Additionally, the nonlinear effects of individual critical drivers on NEP varied across different aridity gradients. The cascade effect of explanatory variables on NEP follows a pathway where geography affects climate, climate change subsequently alters vegetation characteristics, and these changes in vegetation directly drive NPP and Rh, ultimately leading to an indirect impact on NEP. This impact pathway exhibits minimal difference across different bedrock and climate types. This study enhances our comprehension of the role of vegetation carbon sinks and their underlying mechanisms across various bedrock and climate types in global karst regions.

The increasing rate of net carbon uptake in Eurasia has been declining since the early 2000s

The analysis of terrestrial ecosystem carbon dynamics, based on scarce carbon flux observations or carbon flux products simulated by reanalysis meteorological data, has great uncertainties. A more accurate understanding of carbon dynamics in Eurasia was achieved by using a carbon flux dataset (CFD) from meteorological stations with quasi-observational characteristics. The growth of net carbon uptake of ecosystems over Eurasia has been decreasing since the early 2000s. The net ecosystem productivity (NEP) increased significantly with the growth rate of 8.7 × 10−3 g C m−2d−1 yr−1 in spring, summer, and autumn (SSA) during 2003–2011 (p < 0.05), which was correlated with the enhanced vegetation index (EVI) and land surface water index (LSWI). This growth was mostly in dry subhumid and humid regions. However, the change in Eurasian NEP was not significant after 2011. Additionally, about 79 % of the stations in Eurasia were in net carbon uptake in SSA, and net carbon emission stations were mainly located in southwestern Eurasia. The intensity of net carbon uptake was highest in the forest, with a mean carbon uptake of 1.73 ± 0.76 g C m−2d−1 in SSA during 2003–2018, and almost all stations demonstrated carbon uptake. During 2011–2018, the number of stations experiencing reduced NEP exceeded those with increased NEP, and this ratio was higher compared to 2003–2011, mainly due to the decrease in EVI and LSWI. The rate of NEP decline at stations with reduced NEP was 5.2 × 10−3 g C m−2d−1 yr−1 faster during 2011–2018 than in the previous period (p < 0.01). Most of the decreases in NEP during 2011–2018 occurred in cropland, grassland and urban land. The spatio-temporal dynamic analysis of Eurasian NEP could provide references for effective carbon management.

Wildfire Emissions Offset More Permafrost Ecosystem Carbon Sink in the 21st Century

AbstractPermafrost ecosystems in high‐latitudes stock a large amount of carbon and are vulnerable to wildfires under climate warming. However, major knowledge gap remains in the effects of direct carbon loss from increasing wildfire biomass burning on permafrost ecosystem carbon sink. In this study, we used observation‐derived data sets and Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations to investigate how carbon emissions from wildfire biomass burning offset permafrost ecosystem carbon sink under climate warming in the 21st century. We show that the fraction of permafrost ecosystem carbon sink offset by wildfire emissions was 14%–25% during the past two decades. The fraction is projected to be 28%–45% at the end of this century under different warming scenarios. The weakening carbon sink is caused by greater increase in wildfire emissions than net ecosystem production in permafrost regions under climate warming. The increased fraction of ecosystem carbon sink offset by wildfire carbon loss is especially pronounced in continuous permafrost region during the past two decades. Although uncertainties exist in simulations of wildfire emissions and ecosystem carbon budget, results from different models still show that wildfire emissions offset more permafrost ecosystem carbon sink in the 21st century. These findings highlight that carbon sink capacity of permafrost ecosystems is increasingly threatened by wildfires under the warming climate.

Modeling the Effects of Increased Hurricane Frequency on the Tropical Forest Carbon Cycle

AbstractModels project that climate change is increasing the frequency of severe storm events such as hurricanes. Hurricanes are an important driver of ecosystem structure and function in tropical coastal and island regions and thus impact tropical forest carbon (C) cycling. We used the DayCent model to explore the effects of increased hurricane frequency on humid tropical forest C stocks and fluxes at decadal and centennial timescales. The model was parameterized with empirical data from the Luquillo Experimental Forest (LEF), Puerto Rico. The DayCent model replicated the well-documented cyclical pattern of forest biomass fluctuations in hurricane-impacted forests such as the LEF. At the historical hurricane frequency (60 years), the dynamic steady state mean forest biomass was 80.9 ± 0.8 Mg C/ha during the 500-year study period. Increasing hurricane frequency to 30 and 10 years did not significantly affect net primary productivity but resulted in a significant decrease in mean forest biomass to 61.1 ± 0.6 and 33.2 ± 0.2 Mg C/ha, respectively (p &lt; 0.001). Hurricane events at all intervals had a positive effect on soil C stocks, although the magnitude and rate of change of soil C varied with hurricane frequency. However, the gain in soil C stocks was insufficient to offset the larger losses from aboveground biomass C over the time period. Heterotrophic respiration increased with hurricane frequency by 1.6 to 4.8%. Overall, we found that an increasing frequency of tropical hurricanes led to a decrease in net ecosystem production by − 0.2 ± 0.08 Mg C/ha/y to − 0.4 ± 0.04 Mg C/ha/y for 30–10-year hurricane intervals, respectively, significantly increasing the C source strength of this forest. These results demonstrate how changes in hurricane frequency can have major implications for the tropical forest C cycle and limit the potential for this ecosystem to serve as a net C sink.

Patterns and controls of leaf litter nitrogen and phosphorus of broad-leaved tree species across and within the tropics and the extra-tropics

Leaf litter nitrogen (N) and phosphorus (P), as the final products reflecting the foliar nutrient status after resorption, strongly influence forest production and nutrient cycling. However, our nuanced understanding of their general patterns and controls is still lacking, and whether differential regulatory mechanisms exist between climatic zones remains largely incomplete, which introduces substantial uncertainty in the comprehension of net ecosystem productivity and nutrient cycling. Here, we aimed to evaluate patterns of leaf litter N and P concentrations of broad-leaved tree species, and further quantify their controls from climatic, soil physical, soil chemical, and green foliar nutrient factors across and within the tropics and extra-tropics by updating a global dataset comprising 1171 records from 159 studies. We found that tropical tree species exhibited higher leaf litter N concentrations but lower leaf litter P concentrations than extra-tropical tree species. In contrast to previous findings, the effects of climatic and edaphic variables on leaf litter N and P concentrations are more pronounced in the tropics than in the extra-tropics. Different from past bivariate analyses of climate-nutrient relationships for leaf litter, climate exerted more indirect effects on leaf litter N and P concentrations through soil texture, hydrology, nutrient availability, and green foliar nutrients. We also observed direct effects of green foliar N and P concentrations on leaf litter N and P concentrations enhanced from tropical to extra-tropical zones. Overall, this study refines our understanding of differential controls over leaf litter N and P concentrations across climatic zones and highlights the crucial yet often overlooked role of soil physical and chemical properties. These insights further underscore the urgent need to integrate multiple climatic, edaphic, and green foliar nutrient variables into geographically explicit biogeochemical models to improve our understanding of leaf litter-driven forest nutrient cycling in response to future environmental changes for different climatic zones.

Temporal dynamics of stream algae under the combined impacts of climate and land‐use stressors

Abstract Ecosystems are increasingly challenged by the multiple facets of climate change, coupled with intensifying land‐use pressures. These co‐occurring stressors can interact in complex ways, but we lack an empirical understanding of the impact of higher‐order interactions on temporal patterns. Using 128 flow‐through circular stream mesocosms, we investigated the individual and combined effects of two climatic stressors (CO2 enrichment, flow variability) and two land‐use‐related stressors (siltation, light—as lack of shading) on algal communities and net ecosystem productivity (NPP) in a full‐factorial design. The sediment pulses coincided with high flow to mimic erosion events, whereas CO2 and light disturbances were applied continuously, as they would in nature. Sediment emerged as a key stressor for algal biomass. Land‐use stressors had more pervasive individual effects, whereas climate‐change‐related stressors were more important in up to three‐way interactions with other stressors. However, CO2 was a key driver of NPP, followed by sediment and light, whereas flow variability was only important in interactions with other stressors. The effects of sediment and flow on algal biomass depended strongly on their temporal patterns. The combined effect of an increasing number of stressors on algal biomass appeared to reach saturation with three active stressors, with no apparent additional effect caused by the fourth stressor. Synthesis. Sediment emerged as a key stressor in streams. Despite the mounting evidence and the multitude of available mitigation strategies, this problem persists worldwide. The complex interactions uncovered in our study illustrate context‐dependency that can be masked in two‐factor experiments. Our findings also highlighted that temporal patterns of individual and co‐occurring stressors can determine the ecological outcome.

Spatial variations of annual net ecosystem productivity and its trend over Chinese terrestrial ecosystems based on spatial downscaling.

Annual net ecosystem productivity (NEP), the amount of net carbon sequestration during a year, serves as the basis of terrestrial carbon sink. Quantifying the spatial variations of NEP and its trend would enhance our understandings on the response and adaption of ecosystems to environmental change, which also serves for the regional carbon management targeting at carbon neutrality. Based on process-based model and data-driven model simulating NEP, we selected the optimal simulating NEP mostly representing NEP spatial variations with multiple site eddy covariance measurements to develop the spatial downscaling method and generate high resolution NEP data of China, which was used to examine the spatial variations of NEP and its trend and driving factors during 2000-2017. Compared with process-based model results, data-driven model simulating NEP could mostly represent the spatial variation of site measurements. The random forest regression based on climate, soil, and biological data combining with the simple scaling could successfully downscale NEP to a high spatial resolution. From 2000 to 2017, the total amount of NEP in China was (1.30±0.03) Pg C·a-1, showing a decreasing-increasing pattern with the inflection point in 2009. Chinese NEP decreased from southeast to northwest, showing a descending latitudinal distribution and an ascending longitudinal distribution, with the combined effects of climate and biotic factors. NEP trend decreased from east towards west, which was only accompanied with a slightly ascending longitudinal distribution, while photosynthetically active radiation and soil organic carbon content dominated the spatial variations of NEP trend. Therefore, the spatial patterns of generated NEP obviously differed from those of NEP trend, suggesting the obvious difference between the responses and adaptions of ecosystems to environmental changes.

Exploring the Influencing Factors of Net Ecosystem Productivity (NEP) Based on Random Forest and SHAP

As global climate change intensifies, Net Ecosystem Productivity (NEP) serves as a crucial indicator for measuring the carbon absorption and release of ecosystems, playing a vital role in understanding the carbon cycle and shaping climate policy. The Northwestern region of China, characterized as a typical inland arid and semi-arid area, is particularly sensitive to global changes. Understanding the environmental drivers of NEP in this region is critical for both regional ecological protection and global environmental management. This study utilized environmental data from five provinces in Northwestern China, applying the Random Forest (RF) model and SHapley Additive exPlanation (SHAP) method to analyze the primary environmental factors influencing NEP. The research integrated climatic data (including temperature, precipitation, wind speed, and solar radiation), soil characteristics such as pH, organic carbon content, and soil texture, topographic attributes elevation and slope, and a Human Footprint. The RF model identified significant environmental factors impacting NEP, and SHAP values were used to explain the specific contributions of these factors. Furthermore, multiple linear regression analysis revealed interactions among environmental factors. The results indicate that solar radiation (Srad), precipitation, topsoil reference bulk density (T_REF_BULK), temperature, and the topsoil clay fraction (T_CLAY) significantly influence NEP. Notably, interactions between aspect and T_CLAY, aspect and T_REF_BULK, as well as the human footprint (HFP) and Srad, also show significant impacts on NEP. This study confirms that solar radiation, precipitation, soil characteristics, and human activities are the primary environmental drivers of NEP in the Northwest region of China, with solar radiation playing the most critical promotional role. The findings not only provide a scientific basis for the management of ecosystems in Northwestern China but also offer references for formulating global climate change mitigation strategies and estimating the global carbon budget. Future research should further explore the specific mechanisms and interactions of these drivers across different ecosystems to more comprehensively understand and predict the trends in NEP changes.

Substantial nitrogen abatement accompanying decarbonization suppresses terrestrial carbon sinks in China

China faces challenges in reaching its carbon neutrality goal by the year 2060 to meet the Paris Agreement and improving air quality simultaneously. Dramatic nitrogen emission reductions will be brought by this ambitious target, yet their impact on the natural ecosystem is not clear. Here, by combining two atmospheric chemistry models and two process-based terrestrial ecosystem models constrained using nationwide measurements, we show that atmospheric nitrogen deposition in China’s terrestrial land will decrease by 44–57% following two emission control scenarios including one aiming at carbon neutrality. They consequently result in a pronounced shrinkage in terrestrial net ecosystem production, by 11–20% depending on models and emission scenarios. Our results indicate that the nitrogen emission reductions accompanying decarbonization would undermine natural carbon sinks and in turn set back progress toward carbon neutrality. This unintended impact calls for great concern about the trade-offs between nitrogen management and carbon neutrality.

Divergent metabolism estimates from dissolved oxygen and inorganic carbon: Implications for river carbon cycling

AbstractRivers efficiently collect, process, and transport terrestrial‐derived carbon. River ecosystem metabolism is the primary mechanism for processing carbon. Diel cycles of dissolved oxygen (DO) have been used for decades to infer river ecosystem metabolic rates, which are routinely used to predict metabolism of carbon dioxide (CO2) with uncertainties of the assumed stoichiometry ranging by a factor of 4. Dissolved inorganic carbon (DIC) has been less used to directly infer metabolism because it is more difficult to quantify, involves the complexity of inorganic carbon speciation, and as shown in this study, likely requires a two‐station approach. Here, we developed DIC metabolism models using single‐ and two‐station approaches. We compared metabolism estimates based on simultaneous DO and DIC monitoring in the Upper Clark Fork River (USA), which also allowed us to estimate ecosystem‐level photosynthetic and respiratory quotients (PQE and RQE). We observed that metabolism estimates from DIC varied more between single‐ and two‐station approaches than estimates from DO. Due to carbonate buffering, CO2 is slower to equilibrate with the atmosphere compared to DO, likely incorporating a longer distance of upstream heterogeneity. Reach‐averaged PQE ranged from 1.5 to 2.0, while RQE ranged from 0.8 to 1.5. Gross primary production from DO was larger than that from DIC, as was net ecosystem production by . The river was autotrophic based on DO but heterotrophic based on DIC, complicating our understanding of how metabolism regulated CO2 production. We suggest future studies simultaneously model metabolism from DO and DIC to understand carbon processing in rivers.

Selection of Suitable Organic Amendments to Balance Agricultural Economic Benefits and Carbon Sequestration.

Long-term excessive use of fertilizers and intensive cultivation not only decreases soil organic carbon (SOC) and productivity, but also increases greenhouse gas emissions, which is detrimental to sustainable agricultural development. The purpose of this paper is to identify organic amendments suitable for winter wheat growth in the North China Plain by studying the effects of organic amendments on the economic benefits, carbon emissions, and carbon sequestration for winter wheat fields and to provide a theoretical basis for the wide application of organic amendments in agricultural fields. The two nitrogen rates were N0 (0 kg ha-1) and N240 (240 kg ha-1), and the four organic amendments were straw, manure, mushroom residue (M R), and biochar. The results showed that, compared to N0, N240 significantly increased the yield by 244.1-318.4% and the organic carbon storage by 16.7-30.5%, respectively, but increased the carbon emissions by 29.3-45.5%. In addition, soil carbon stocks increased with all three types of organic amendments compared to the straw amendment, with the biochar treatment being the largest, increasing carbon storage by 13.3-33.6%. In terms of yield and economic benefits, compared to the straw amendment, the manure and biochar amendments increased winter wheat yields by 0.0-1.5% and 4.0-13.3%, respectively, and M R slightly decreased wheat yield; only the economic benefit of the M R amendment was greater than that of the straw amendment, with an increase in economic benefit of 1.3% and 8.2% in the 2021-2022 and 2022-2023 seasons, respectively. Furthermore, according to the net ecosystem productivity (NEP), N0 was the source of CO2, while N240 was a sink of CO2. The TOPSIS results showed that N240 with a mushroom residue amendment could be recommended for increasing soil carbon stocks and economic benefits for winter wheat in the NCP and similar regions. Low-cost M R can increase farmer motivation and improve soil organic carbon, making a big step forward in the spread of organic materials on farmland.