Search

In the context of global climate change, atmospheric nitrogen deposition is increasing, and precipitation patterns are becoming more variable. This study examines the impact of these changes on nitrogen (N) allocation mechanisms in semi-arid region tree species using one-year-old Mongolian pine (Pinus sylvestris var. mongolica) seedlings. The seedlings were planted in soil collected from the Daqinggou Sandy Ecological Experiment Station (42°54′ N, 122°25′ E). Three moisture treatments were applied (WC (normal moisture, approximately 65% ± 2.5% of the field capacity), WI (30% increased moisture), and WD (30% decreased moisture)), as well as three nitrogen treatments (NC (no nitrogen), NL (5 g·m−2·y−1 nitrogen), and NH (10 g·m−2·y−1 nitrogen)). The seedlings were sprayed with a 15N-labeled CH4N2O solution (46% N, 15N abundance 10.14%) in a pot trial, with samples taken in August and October to measure N content and 15N abundance in the seedling organs and the soil. Parameters such as Ndff (%) (the percentage of nitrogen derived from fertilizer), nitrogen content of organs, 15N absorption in organs, and 15N distribution ratio were calculated. The results showed that 15N allocation in seedlings followed the trend leaves > stems > roots. Under moisture treatments, 15N allocation ratios in leaves, stems, and roots were 63.63–71.42%, 14.89–24.14%, and 12.23–14.88% under low nitrogen, and 62.63–77.83%, 13.35–22.90%, and 7.31–19.18% under high nitrogen. Significant correlations were found in 15N abundance among the seedling organs, with coefficients ranging from 0.97 to 1.00. The main effects of moisture and nitrogen, as well as their interaction, significantly impacted 15N abundance in the seedling organs. Changes in moisture levels affected the nitrogen absorption capacity of Mongolian pine. Increased moisture significantly enhanced 15N absorption in all organs, leading to 62.63–71.42% of 15N being allocated to the leaves, maintaining an appropriate proportion with the roots and stems. Nitrogen deposition altered the nitrogen allocation strategy among different organs of Mongolian pine. Under conditions of reduced moisture and low nitrogen, a greater proportion of nitrogen was captured by the roots and stems, with an allocation increase of approximately 4.98–5.77% compared to the control group, thereby mitigating the adverse effects of water deficiency. In conditions of reduced moisture and high nitrogen, the leaves, being active organs, accumulated more limiting elements, with an increase in nitrogen allocation of 2.03–8.07% compared to the control group. To achieve an optimal allocation strategy, moderate nitrogen deposition combined with increased moisture enhanced nitrogen uptake in Mongolian pine seedlings. This study provides scientific evidence for ecological restoration, wind erosion control, and agricultural and forestry management in semi-arid regions under the context of global climate change.

The reaction wheel bicycle robot is a kind of unmanned mobile robot with great potential. However, the control of such bicycle robots on a curved pavement under inaccurate model parameters, model uncertainties and disturbances is challenging due to the lateral instability and underactuated characteristic. Applying conventional control methods to this problem often results in brittle and inaccurate controllers. In this paper, an online serial-parallel combination reinforcement learning with conventional control methods is designed to achieve the path tracking and banlancing control for a reaction wheel bicycle robot on curved pavements. The parallel part of the controller refers to compensating the equilibrium point and the serial part of the controller refers to adjusting the parameters of a sliding mode controller that tracks the target roll equilibrium point. The comparison between the proposed controller and several existing controllers in experimental test built in Matlab Simscape illustrates stronger robustness and better control performances.

Background and purposeThe best method for selecting patients with acute vertebrobasilar artery occlusion (VBAO) who would benefit from endovascular treatment (EVT) is still the key question. This study aimed to assess the efficacy of magnetic resonance imaging (MRI) for selecting patients with acute VBAO for EVT.Materials and methodsA total of 14 patients with suspected acute VBAO on MR angiography (MRA) in the EVT database (from April 2016 to August 2019) were enrolled. Acute Stroke Prognosis Early Computed Tomography Score (ASPECTS) and pons–midbrain index were assessed on diffusion-weighted imaging (DWI). EVT included a stent retriever and a rescue treatment (angioplasty and/or stenting). The proportion of successful reperfusion and favorable functional outcomes (modified Rankin Scale ≤ 3) at 90 days was documented.ResultsA total of 11 patients were included in the final analysis. The median DWI-ASPECTS and pons–midbrain index were 7 and 2, respectively. Underlying stenosis was detected in 10 of 11 (90.9%) patients. Balloon angioplasty and/or stenting were used as rescue therapy for five patients and two patients, respectively. A total of nine patients (81.8%) achieved successful reperfusion (mTICI, 2b, or 3). The 90-day mRS score of 0–3 was achieved in six (54.5%) patients. The mortality rate within 90 days was 18.2% (two of 11 patients).ConclusionDWI plus MRA could help select the patients with acute VBAO for EVT by assessing ASPECTS and the pons–midbrain index. Patients could achieve good reperfusion and favorable functional outcomes.

Global climate change presents a significant threat to food security. Analyzing the effects of elevated ozone (O3) concentration on photosynthetic fluorescence characteristics and yield addresses the damage of climate change on crops, which would serve food security. With open-top chambers (OTCs) and Tiefeng-29 soybeans, we investigated the responses of chlorophyll concentration, fluorescence characteristics, net photosynthetic rate (Pn) and yield components to different O3 concentrations, which included CK (ambient concentration approximately 45 nL·L−1, T1 (80 ± 10) nL·L−1 and T2 (120 ± 10) nL·L−1 O3. The parent soybeans (S1) were planted in the current year, and O3 fumigation commenced 20 days after seedling emergence. Aeration was stopped at maturity, and the offspring soybeans (S2) were retained after harvest for further experiments. In the following year, S1 and S2 soybeans were planted, and O3 fumigation began 20 days after seedling emergence. The results show that leaf chlorophyll a (chla) and chlorophyll b (chlb) significantly decreased with longer O3 fumigation time both in parents and offspring, causing damage to the light-trapping ability while the offspring suffered an earlier decrease. The elevated O3 damaged the electron transfer process by significantly reducing the original and actual photochemical efficiencies of PSII both in parents and offspring. The electron transfer rate (ETR) of the parents and offspring decreased, while the difference between them was not significant after O3 treatment. The non-photochemical quenching coefficient (NPQ) showed an increasing trend along time but showed no significant difference between parents and offspring. An elevated concentration of O3 significantly reduced Pn, while the differences in Pn between the parents and the offspring were not significant. Elevated O3 resulted in reduced yields in both parent and offspring soybeans. Although it was found that the offspring soybeans exhibited higher yields than the parents, their reduction in yield was more significant. Therefore, elevated O3 concentration reduced soybean yield through damaging photosynthetic process and electron transfer capacity by impairing energy conversion and material accumulation capacity. The offspring had relatively higher light energy conversion efficiency than the parents, resulting in a higher yield than the parents under all treatments.

A deep understanding of the responses of photosynthesis to air temperature (Ta) is essential for accurately assessing carbon budgets. Photosynthetic light response (PLR) parameters, including apparent quantum yield (α), maximum photosynthesis rate (Pmax) and daytime ecosystem respiration (Rd), are widely used to describe and quantify photosynthesis at the ecosystem scale. However, an understanding of the specific responses of PLR parameters to temperature in different seasons is still lacking. Therefore, this study aimed to address this issue based on 17-year continuous eddy covariance measurements (2003–2019) in a subtropical coniferous plantation. The responses of PLR parameters to air temperature (Ta) were obtained by classifying the observed net ecosystem exchange (NEE) and the corresponding photosynthetically active radiation (PAR) according to Ta with a class width of 2 °C. The general regulations showed that α, Rd and Pmax first increased with Ta until the optimal Ta and then decreased. The optimal Ta for α, Rd and Pmax were 28, 30 and 32 °C, and the inflection points were consistent with the soil water content (SWC) at depths of 5, 20, and 50 cm, respectively. For the specific seasonal responses, the optimal Ta for α and Rd was highest in summer, with a value as high as 30 °C, and the optimal Ta was highest in autumn, with a value of 32 °C. Interestingly, although the temperature environments were similar in spring and autumn, the optimal Ta for α was 2 °C higher in spring than in autumn, but the optimal Ta for Pmax was 6 °C higher in autumn than in spring. Some special response patterns were also found according to delicate studies on a seasonal scale, which were found to be related to SWCs at different depths. These findings reflected the inner function changes of the ecosystem and the potential effects of SWC, which should be given special attention when the PLR parameters are used in models to predict the carbon budgets in the future.

Annual evapotranspiration (AET), the total water vapor loss to the atmosphere during a year, is a vital process of global water cycles and energy cycles. Revealing the differences in AET values and spatial variations between forests and grasslands would benefit for understanding AET spatial variations, which serves as a basis for regional water management. Based on published eddy covariance measurements in China, we collected AET values from 29 forests and 46 grasslands, and analyzed the differences in AET values and spatial variations between forests and grasslands in China. The results showed that forests had a significant higher AET (645.98 ± 232.73 kgH2O m-2 yr-1) than grasslands (359.31 ± 156.02 kgH2O m-2 yr-1), while the difference in AET values between forests and grasslands was not significant after controlling mean annual precipitation (MAP) relating factors. The effects of latitude and mean annual air temperature (MAT) on AET spatial variations differed between forests and grassland, while AET of forests and grasslands both exhibited increasing trends with similar rates along the increasing MAP, aridity index (AI), soil water content (SW), and leaf area index. The comprehensive effects of multiple factors on AET spatial variations differed between forests and grasslands, while MAP both played a dominating role. The effects of other factors were achieved through their close correlations with MAP. Therefore, forests and grasslands under similar climate had comparable AET values. AET responses to MAP were comparable between ecosystem types. Our findings provided a data basis for understanding AET spatial variation over terrestrial ecosystems of China or globally.

Background and PurposeDiagnosing cervical artery dissection (CAD) is still a challenge based on the current radiographic criteria. This study aimed to assess the value of three-dimensional high-resolution magnetic resonance imaging (3D HRMRI) in the detection of the signs of CAD and its diagnosis.Materials and MethodsPatients with CAD from January 2016 to January 2021 were recruited from our 3D HRMRI database. The signs of dissection (intramural hematomas, intimal flap, double lumen), length and location of the dissection, thickness of the intramural hematoma, intraluminal thrombus, and percentage of dilation of the outer contour of the dissection on 3D HRMRI were assessed.ResultsFourteen patients with 16 CADs, including 12 carotid CADs and 4 vertebral CADs, were finally diagnosed in this study. On 3D HRMRI, intramural hematomas were detected in 13/16 (81.3%) lesions with high sensitivity (100%) and high specificity (100%). Intimal flaps were found in 9/16 (56.3%) lesions with moderate sensitivity (64.3%) and high specificity (88.9%). Double lumen signs were observed in 4/16 (25.0%) lesions with high sensitivity (80.0%) and high specificity (100%). In addition, concomitant intraluminal thrombus were detected in 4/16 (25.0%) lesions with high sensitivity (80.0%) and high specificity (100%). The mean length of dissection was (25.1 ± 13.7) mm. The mean thickness of the intramural hematoma was (4.3 ± 2.3) mm. The mean percentage of dilation for the outer contour of the dissection was (151.3 ± 28.6)%.ConclusionThe 3D HRMRI enables detection of the dissecting signs, such as intramural hematoma, intimal flap, double lumen, and intraluminal thrombus with high sensitivity and specificity, suggesting a useful, and non-invasive tool for definitively diagnosing CAD.

Evapotranspiration (ET) is a vital part of the global water cycle and is closely related to carbon sequestration. Analysing ET dynamics and their drivers would benefit for improving our understanding of the global water and carbon cycles. Using an eddy covariance (EC) approach, we analysed ET dynamics and their drivers in a temperate mixed forest over northeast China from 2016 to 2017. The results showed that 43.55% of our eddy covariance data passed the quality control. In addition, the energy balance ratio was 0.62, indicating that measurements were reliable. The measured ET showed clear single peak patterns with seasonal and diurnal variations. The daily ET ranged from 0 to 7.75 mm d−1 and the hourly ET ranged from 0 to 0.28 mm h−1. The ranges of hourly ET floated from 0 to 0.05 mm h−1 at non-growing season (November to April) while ranged from 0 to 0.28 mm h−1 at active growing season (May to October). The diurnal ET dynamics during the non-growing season were driven by air temperature (Ta), but were governed by global radiation (Rg) during the active growing season. Leaf area index (LAI) comprehensively reflected the variations of Ta and Rg, and was found to be the primary factor shaping the seasonal dynamics of ET. The annual ET rates were 501.91 ± 5.30 mm year−1 and 554.60 ± 11.24 mm year−1 for 2016 and 2017, respectively. Therefore, energy supply, represented by Ta and Rg, governed ET dynamics in our temperate mixed forest, while variables representing the energy supply affecting ET dynamics differed among seasons and time scales. ET dynamics indicated that a temperate mixed forest is important to the global water cycle. Our results improved our understanding of ET dynamics in the studied region.

Abstract Breast cancer (BC) is one of the most dangerous malignant diseases in females. However, the reliable serum biomarkers of BC still need to be explored. Chemerin levels have been found to be associated with different types of cancer. This study aimed to evaluate the role of serum chemerin as a biomarker of BC diagnosis, as well as the correlation between serum chemerin levels and clinicopathological features. The serum from 248 BC patients, 30 breast benign tumor patients, and 103 healthy controls were collected and serum chemerin levels were determined with enzyme-linked immunosorbent assay. We found that serum levels of chemerin in BC patients were higher than those in healthy control individuals (p

The single-track two-wheeled (STTW) robot has the advantages of small size and flexibility, and it is suitable for traveling in narrow terrains of mountains and jungles. In this article, a reinforcement learning control method for STTW robots is proposed for driving fast in narrow terrain with limited visibility and line-of-sight occlusions. The proposed control scheme integrates path planning, trajectory tracking, and balancing control in a single framework. Based on this method, the state, action, and reward function are defined for narrow terrain passing tasks. At the same time, we design the actor network and the critic network structures and use the twin delayed deep deterministic policy gradient (TD3) to train these neural networks to construct a controller. Next, a simulation platform is formulated to test the performances of the proposed control method. The simulation results show that the obtained controller allows the STTW robot to effectively pass the training terrain, as well as the four test terrains. In addition, this article conducts a simulation comparison to prove the advantages of the integrated framework over traditional methods and the effectiveness of the reward function.

Abstract An increasing number of studies have indicated that red blood cell distribution width (RDW) may be a novel biomarker for the diagnosis and prognosis of various malignancies. However, to date, data on the association of RDW with non-small cell lung cancer (NSCLC) are unclear. Our present study aimed to explore the value of RDW in NSCLC patients. A total of 338 NSCLC patients, 109 small cell lung cancer (SCLC) patients, and 302 healthy participants were retrospectively analyzed between January 2016 and December 2018. In the present study, we found that RDW was significantly increased in NSCLC patients. Receiver-operating characteristic (ROC) analysis showed that the area under the ROC curve (AUC) of RDW was 0.753 in discriminating NSCLC patients from healthy participants, the optimal cut-off value of RDW was 12.95, and the specificity and sensitivity were 76.33% and 76.16%, respectively. Further analysis found that RDW can enhance the diagnostic performance of Cyfra21-1 and NSE in discriminating NSCLC patients from healthy participants or SCLC patients. Among NSCLC patients, RDW was significantly correlated with TNM stage, T stage, N stage, M stage, and Cyfra21-1, indicating that RDW may be helpful for predicting the prognosis of NSCLC patients. Our findings suggest that RDW can be used as an auxiliary marker for the diagnosis and prognosis of NSCLC.

Abstract Background Direct evidence of intimal flaps, double lumen and intramural haematomas (IMH) is difficult to detect on conventional angiography in most intracranial vertebrobasilar dissecting aneurysms (VBDAs). Our purpose was to assess the value of three-dimensional high-resolution magnetic resonance vessel wall imaging (3D HRMR VWI) for identifying VBDAs. Methods Between August 2013 and January 2016, consecutive patients with suspicious VBDAs were prospectively enrolled to undergo catheter angiography and VWI (pre- and post-contrast). The lesion was diagnosed as definite VBDA when presenting direct signs of dissection; as possible when only presenting indirect signs; and as segmental ectasia when there was local dilation and wall thickness similar to adjacent normal artery’s without mural thrombosis. Results Twenty-one patients with 27 lesions suspicious for VBDAs were finally included. Based on findings of VWI and catheter angiography, definite VBDA was diagnosed in 25 and 7 lesions (92.6%, vs 25.9%, p

Understanding the responses of canopy conductance (gc) to environmental factors would help ecologists to obtain further insight into the carbon and water exchange processes and forecast future changes in ecosystems under global climate change. Therefore, we investigated the seasonal and interannual variations in the gc based on 12 years of flux data that were observed by an eddy covariance system in a subtropical coniferous forest. Furthermore, by teasing out the dominant factors step by step, the specific gc responses to environmental factors were clarified, and the divergent responses in contrasting climatic years were determined. The multiyear mean gc was 3.46 ± 0.36 mm·s−1, and the gc peaked in April and declined to a minimum in October in most years. The vapor pressure deficit (VPD) was the most important factor that inhibited the gc, and the gc decreased sharply when the VPDs were greater than 1.8 kPa. Without high VPD stress, the gc increased linearly with air temperature (Ta) when the Ta was below 27 °C, after which it decreased. When the high VPD and Ta stresses were excluded, the gc increased with the net radiation (Rn) following a logistic growth model. The gc increased logarithmically with the soil water content at 5 cm depth (SWC5). The effects of the soil water content at 50 cm depth (SWC50) emerged under water stress or temperature stress conditions, which indicated that the forest utilized deep soil water to defend against environmental stress. Additionally, divergent responses of the gc to environmental factors in different climatic years were found. The results of this study provide detailed information on the gc variations and their specific responses to the environmental factors, which would improve the understanding of gc and help accurately estimate gc.

Summary: In transition metal-catalyzed asymmetric synthesis, enantioselectivity strongly depends on the structures of chiral ligands, so the development of new chiral ligands is crucial. Here, an efficient and highly enantioselective palladium-catalyzed intramolecular hydroarylation has been developed, and a new kind of N-heterocycles, 1H-pyrazolo[5,1-a]isoindol-2(8H)-ones containing a quaternary stereocenter, was prepared in high yields and excellent enantiomeric excess values. The reaction was effectively catalyzed by palladium-diphosphine complexes with numerous functional group tolerance, in which the newly developed axially chiral cyclic diphosphine ligands played key roles in the reactivity and enantioselectivity of the substrates. We believe that the cyclic diphosphine ligands with adjustable dihedral angles will find wide application in asymmetric synthesis. : Chemistry; Catalysis; Organic Chemistry; Stereochemistry Subject Areas: Chemistry, Catalysis, Organic Chemistry, Stereochemistry

Abstract Background Two-dimensional high-resolution MRI (2D HRMRI) faces many technical challenges for fully assessing morphologic characteristics of inherent tortuous basilar arteries. Our aim was to investigate remodeling mechanisms and plaque distribution in symptomatic patients with basilar artery stenosis on three-dimensional (3D) HRMRI. Methods Forty-six consecutive patients with symptomatic basilar artery atherosclerotic stenosis on MRA (70–99%) were enrolled. The remodeling index (RI) was the ratio of vessel area at the maximal-lumen-narrowing (MLN) site to reference vessel area. RI ≥ 1.05 was defined as positive remodeling (PR), RI ≤ 0.95 as negative remodeling (NR), and 0.95 < RI < 1.05 as intermediate remodeling (IR). The remodeling patterns were divided into two groups (PR and non-PR [NR and IR]). The cross-sectional and longitudinal distribution of BA plaques were evaluated. Results Two patients were excluded because of poor-quality images. Images of 44 patients were available for measurements. PR was found in 23 (52.3%) patients, and non-PR in 21 (47.7%) patients. At the MLN sites, vessel area, wall area, plaque size and percentage of plaque burden of PR group were significantly greater than non-PR group (p < .001). Most plaques (90.9%) of the 44 patients were located at the dorsal, left and right walls. For the longitudinal distribution of plaque, 8 (18.2%) and 36 (81.8%) plaques were located in BA proximal and distal to AICA, respectively. Most plaques (68.2%) were eccentrically distributed. Conclusions 3D HRMRI with postprocessing multiple planar reconstruction is able to evaluate the remodeling pattern and plaque distribution of basilar artery atherosclerotic stenosis, which might be used to guide intracranial intervention.

Global warming has a known impact on ecosystems but there is a lack of understanding about its impact on ecosystem processes. Net ecosystem productivity (NEP) and its components play a key part in the global carbon cycle. Analysing the impact of global warming on NEP will improve our understanding of how warming affects ecosystems. In our study, conducted in 2018, five warming treatments were manipulated (0 W, 500 W, 1000 W, 1500 W, and 3000 W) using three repetitions of far infrared open warming over a paddy field in Northeast China. NEP and its two related components, gross primary productivity (GPP) and ecosystem respiration (ER), were measured using the static chamber-infrared gas analyser method to explore the effects of different warming magnitudes on NEP. Results showed that measurement dates, warming treatments, and their interactions significantly affected NEP, ER, and GPP. Warming significantly increased NEP and its components but they showed a non-linear response to different warming magnitudes. The maximum increases in NEP and its components occurred at 1500 W warming. NEP is closely related to its components and the non-linear response of NEP may have primarily resulted from that of GPP. Gradient warming non-linearly increased GPP in the paddy field studied in Northeast China, resulting in the non-linear response of NEP. This study provides a basis for predicting the responses of carbon cycles in future climate events.

Abstract Background Human papillomavirus (HPV) infection is the main etiological factor for the development of cervical cancer. Here we assessed the prevalence and distribution of HPV genotypes in Fujian population. Methods A total of 8678 women aging from 17 to 84 years olds were recruited from the Fujian Medical University Union Hospital in Fujian Province. Every woman had a face-to-face interview. Cervical samples were collected from each participant and HPV screening was conducted using microarray hybridization. Results Our study showed that the HPV prevalence in Fujian province was 38.3%. Among the positive individuals, 70.6% were detected for single HPV infection, 29.4% for multiple HPV infections. Further analysis showed that the prevalence of HPV infection significantly increased from 2009 to 2015. The four most common high risk human papillomavirus (HR-HPV) genotypes were HPV16 (8.5%), HPV52 (7.9%), HPV58 (6.2%), HPV 53 (3.5%), collectively accounting for 60.5% of all detected HPV infection. Age subgroup analysis showed two peaks for the frequencies of overall and multiple HPV infections, one for the group of women under 25 years old, and the other for the group over 55 years old. Conclusions HPV infection is becoming serious in Fujian province, which indicates the imperative to implement a HPV vaccination and screening program for this region.

Spatiotemporal patterns of evapotranspiration (ET) and its controlling factors are important for ecosystem services and water resources management in the Chinese Loess Plateau (CLP). In this study, we assessed the spatial patterns of ET and then investigated the interannual variability of ET and its relationships with climate variability and vegetation coverage changes at the timescales of annual, active growing season, as well as different seasons across the entire CLP from 2000 to 2014. A MODIS-derived ET dataset, ground-based datasets of precipitation and atmospheric evaporative demand (AED), and a remote-sensing dataset of Normalized Difference Vegetation Index (NDVI) were comprehensively analyzed. Results showed that mean annual ET varied distinctly among different vegetation zones, generally higher in the more humid southeastern parts of the CLP. Summer ET and ET over active growing season significantly increased for more than 40% of the entire CLP area, and winter ET significantly decreased over ~70% of the entire CLP region, while annual ET, spring ET, and autumn ET remained quite stable during 2000–2014. Per-pixel interannual variability of ET was mainly positively correlated with that of precipitation and NDVI except for winter, but negatively correlated with AED trends. Our study also demonstrated that ET variation trends were exactly consistent for the entire CLP region, the areas mainly implemented with the Grain for Green (GFG) project, and other CLP areas not implemented with the GFG project during 2000–2014. Our findings suggest that the spatiotemporal patterns of CLP ET were mainly water-limited, and climate variability played an essential role in shaping the interannual variability of ET in the CLP. This study will improve our understanding on the ET variations over water-limited areas under climate and vegetation coverage changes.

Climate, vegetation, and soil characteristics play important roles in regulating the spatial variation in carbon dioxide fluxes, but their relative influence is still uncertain. In this study, we compiled data from 241 eddy covariance flux sites in the Northern Hemisphere and used Classification and Regression Trees and Redundancy Analysis to assess how climate, vegetation, and soil affect the spatial variations in three carbon dioxide fluxes (annual gross primary production (AGPP), annual ecosystem respiration (ARE), and annual net ecosystem production (ANEP)). Our results showed that the spatial variations in AGPP, ARE, and ANEP were significantly related to the climate and vegetation factors (correlation coefficients, R = 0.22 to 0.69, P < 0.01) while they were not related to the soil factors (R = -0.11 to 0.14, P > 0.05) in the Northern Hemisphere. The climate and vegetation together explained 60% and 58% of the spatial variations in AGPP and ARE, respectively. Climate factors (mean annual temperature and precipitation) could account for 45-47% of the spatial variations in AGPP and ARE, but the climate constraint on the vegetation index explained approximately 75%. Our findings suggest that climate factors affect the spatial variations in AGPP and ARE mainly by regulating vegetation properties, while soil factors exert a minor effect. To more accurately assess global carbon balance and predict ecosystem responses to climate change, these discrepant roles of climate, vegetation, and soil are required to be fully considered in the future land surface models. Moreover, our results showed that climate and vegetation factors failed to capture the spatial variation in ANEP and suggest that to reveal the underlying mechanism for variation in ANEP, taking into account the effects of other factors (such as climate change and disturbances) is necessary.

The modeling and partitioning of regional evapotranspiration (ET) are key issues in global hydrological and ecological research. We incorporated a stomatal conductance model and a light-use efficiency-based gross primary productivity (GPP) model into the Shuttleworth–Wallace model to develop a simplified carbon-water coupling model, SWH, for estimating ET using meteorological and remote sensing data. To enable regional application of the SWH model, we optimized key parameters with measurements from global eddy covariance (EC) tower sites. In addition, we estimated soil water content with the principle of the bucket system. The model prediction of ET agreed well with the estimates obtained with the EC measurements, with an average R2 of 0.77 and a root mean square error of 0.72 mm·day−1. The model performance was generally better for woody ecosystems than herbaceous ecosystems. Finally, the spatial patterns of ET and relevant model outputs (i.e., GPP, water-use efficiency and the ratio of soil water evaporation to ET) in China with the model simulations were assessed.

Evapotranspiration (ET) is an important component of the water cycle in terrestrial ecosystems. Understanding the ways in which ET changes with meteorological factors is central to a better understanding of ecological and hydrological processes. In this study, we used eddy covariance measurements of ET from a typical alpine shrubland meadow ecosystem in China to investigate the hysteresis response of ET to environmental variables including air temperature (Ta), vapor pressure deficit (VPD) and net radiation (Rn) at a diel timescale. Meanwhile, the simulated ET by Priestly-Taylor equation was used to interpret the measured ET under well-watered conditions. Pronounced hysteresis was observed in both Ta and VPD response curves of ET. At a similar Ta and VPD, ET was always significantly depressed in the afternoon compared with the morning. But the hysteresis response of ET to Rn was not evident. Similar hysteresis patterns were also observed in the Ta/VPD response curves of simulated ET. The magnitudes of the measured and simulated hysteresis loops showed similar seasonal variation, with relatively smaller values occurring from May to September, which agreed well with the lifetime of plants and the period of rainy season at this site. About 62% and 23% of changes in the strength of measured ET-Ta and ET-VPD loops could be explained by the changes in the strength of simulated loops, respectively. Thus, the time lag between Rn and Ta/VPD is the most important factor generating and modulating the ET-Ta/VPD hysteresis, but plants and water status also contribute to the hysteresis response of ET. Our research confirmed the different hysteresis in the responses of ET to meteorological factors and proved the vital role of Rn in driving the diel course of ET.