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One of the major uncertainties for carbon-climate feedback predictions is an inadequate understanding of the mechanisms governing variations in ecosystem productivity response to warming. Temperature and water availability are regarded as the primary controls over the direction and magnitude of warming effects, but some unexplained results signal that our understanding is incomplete. Using two complementary meta-analyses, we present evidence that soil nitrogen (N) availability drives the warming effects on ecosystem productivity more strongly than thermal and hydrological factors over a broad geographical scale. First, by synthesizing temperature manipulation experiments, a meta-regression model analysis showed that the warming effect on productivity is mainly driven by its effect on soil N availability. Sites with a higher warming-induced increase in N availability were characterized by stronger productivity enhancement and vice versa, suggesting that N is a limiting factor across sites. Second, a synthesis of full-factorial warming × N addition experiments demonstrated that N addition significantly weakened the positive warming effect, because the additional N induced by warming may not further benefit plant growth when N limitation is relieved, providing experimental evidence that N regulates the warming effect. Furthermore, we demonstrated that warming effects on soil N availability were modulated by changes in dissolved organic N and soil microbes. Overall, our findings enrich a new mechanistic understanding of the varying magnitudes of observed productivity response to warming, and the N scaling of warming effects may help to constrain climate projections.

Over-fertilization could lead to nitrogen (N) losses and environmental risks, and the appropriate nitrogen fertilizer could reduce the nitrous oxide (N2O) emission and increase the N utilization of...

Unparalleled inputs of anthropogenic nitrogen (N) and phosphorus (P) cause a strong N-P imbalance in terrestrial ecosystems. However, the effects of N-P imbalance on plant biomass production remains unclear. Given that tissue N:P ratio may serve as an indicator of plant N or P limitations, we compiled a dataset reporting aboveground biomass (AGB) and tissue N:P ratio simultaneously from worldwide N addition experiments and explored the relationship between the responses of AGB and tissue N:P ratio to N enrichment. The N-induced changes in AGB exhibited an asymptotic relationship (i.e., Michaelis-Menten function) with changes in tissue N:P ratio, indicating a progressive P limitation with increasing N. Our results further revealed that plant N and P status was related to the changes in soil inorganic N and P concentrations. Soil N increased while soil P remained unchanged with increasing N rate, thus resulting in an unbalanced soil N and P as N continues to increase. This study is the first to report the influences of human-induced N-P imbalance on plant biomass production at the global scale. The biomass-N:P ratio relationship needs to be considered for reliable predictions of the future global carbon dynamics under global change.

Understanding the key processes and mechanisms of photosynthetic and respiratory acclimation of maize (Zea mays L.) plants in response to experimental warming may further shed lights on the changes in the carbon exchange and Net Primary Production (NPP) of agricultural ecosystem in a warmer climate regime. In the current study, we examined the temperature responses and sensitivity of foliar photosynthesis and respiration for exploring the mechanisms of thermal acclimation associated with physiological and biochemical processes in the North China Plain (NCP) with a field manipulative warming experiment. We found that thermal acclimation of An as evidenced by the upward shift of An-T was determined by the maximum velocity of Rubisco carboxylation (Vcmax), the maximum rate of electron transport (Jmax), and the stomatal- regulated CO2 diffusion process (gs), while the balance between respiration and photosynthesis (Rd/Ag), and/or regeneration of RuBP and the Rubisco carboxylation (Jmax/Vcmax) barely affected the thermal acclimation of An. We also found that the temperature response and sensitivity of Rd was closely associated with the changes in foliar N concentration induced by warming. These results suggest that the leaf-level thermal acclimation of photosynthesis and respiration may mitigate or even offset the negative impacts on maize from future climate warming, which should be considered to improve the accuracy of process-based ecosystem models under future climate warming.

Temperature response and sensitivity of photosynthesis and respiration are critical for projection of changes in the carbon exchange and net primary production of terrestrial ecosystems under global warming. Understanding the mechanisms and processes of photosynthetic and respiratory acclimation in response to warming may shed further lights on the change of crop yield in agricultural ecosystems in a warmer climate regime. We examined the temperature responses and sensitivity of net photosynthetic rate (An) and dark respiration (Rd) for exploring the mechanisms of thermal acclimation associated with physiological and biochemical processes affecting maize yield in the North China Plain with a field manipulative warming experiment. We found that warming substantially enhanced the carbon gain of maize plants through facilitating CO2 diffusion from ambient air to chloroplasts by altering stomatal structure and spatial distribution pattern, and benefitting CO2 assimilation efficiency with smaller vascular bundles and bigger chloroplasts. Moreover, we also found that acclimation of An to temperature (T), evidenced by the upward shift of An–T, was determined by the maximum velocity of Rubisco carboxylation (Vcmax), the maximum rate of electron transport (Jmax), and the stomatal-regulated CO2 diffusion process, whereas the balance between respiration and gross photosynthetic rate (Rd/Ag), and/or regeneration of RuBP and the Rubisco carboxylation (Jmax/Vcmax) made little contribution to the thermal acclimation of An in maize plants. In addition, temperature response and sensitivity of Rd was closely associated with the changes in foliar N concentration induced by warming. As a result, experimental warming barely affected the yield and biomass of maize plants. These results suggest that the impacts of future climate warming on maize production may be mitigated or even offset by the leaf-level thermal acclimation of photosynthesis and respiration. Our findings may have important implications for improving the accuracy of process-based ecosystem models and advancing the understanding on the interactions between ecosystem functions and climate warming.

High-profile nutrient accumulation has caused low nutrient use efficiency and environmental pollution. A total of 140 points in farmers’ wheat fields were investigated and sampled under a typical winter wheat and summer maize rotation system in the Huang-huai-hai Plain of China (HPC). The average wheat yield in the high-yield field is more than 10% relative to the mid-low-yield areas based on historical data. The results showed in the high-yield wheat field the effective spike number was the main yield component, followed by 1000-grain weight. Uptake contents and ratios of N, P2O5 and K2O in the whole wheat plant were also examined. Along the soil depth, organic matter (OM), alkali-hydrolyzable N (AN), available P (AP) and available K (AK) concentration gradually decreased. Soil critical values of AN, AP and AK in the 0–20 cm depth needed to achieve the maximum grain yield were 85.9, 17.7 and 114.2 mg kg−1 calculated by the significant linear-plus-plateau model between wheat grain yield and soil n...

Understanding the key processes and potential mechanisms of crops in response to elevated atmospheric CO2 concentration and drought may further shed lights on the impacts of climate change on the global agriculture ecosystems. This study examined the effects of elevated atmospheric CO2 concentration on the growth of winter wheat under different soil water conditions (full irrigation, mild water stress, moderate water stress, and severe water stress) with growth chambers where the CO2 concentration was controlled at 400 and 800 µmol mol−1, respectively. We found a very strong CO2 fertilization effect on the growth of winter wheat under full irrigation condition, whereas this CO2 fertilization effect declined and eventually vanished with soil water stress, as evidenced by the decreased plant biomass and leaf photosynthesis of winter wheat independent of CO2 concentration. This adverse impact of water stress on the CO2 fertilization effect for plant growth may attribute to the changes in morphological characteristics of individual stoma and spatial distribution pattern of stomata as well as the non-structural carbohydrates of winter wheat. These results suggested that water stress may lower the CO2 fertilization effect on plant growth through altering stomatal traits, leaf photochemical processes, and biochemical compositions of winter wheat. Therefore, many current climate models based on earlier “double-CO2” experiment may overestimate the CO2 fertilization effect on crops, and meanwhile underestimate the impacts of climate change on global agriculture production when the elevated atmospheric CO2 concentration confounded with drought stress under future climate change.

Drought is one of the major climatic disasters intimidating winter wheat production in the Huang-Huai-Hai (3H) Plain of China. The yield damage caused by drought tends to increase in the future, indicated by a pronounced uprising of drought events under RCP 8.5 scenario in terms of its affecting magnitude and area. This paper presents a modeling approach by using crop model DSSAT and hydrological indices to assess the vulnerability of winter wheat to future potential drought, based on an integrated assessment of exposure, sensitivity and adaptive capacity. Our results demonstrate that Beijing, Tianjin, Hebei and Shandong are more exposed and sensitive to potential drought than other regions in 3H. Traditional irrigation has the greater benefits in northern 3H Plain than southern regions, but is still insufficient to impede the yield loss due to potential drought. Under RCP 8.5 emission scenario and the period of 2010–2050, the worst drought effect is projected to occur around 2030. More than half of 3H plain are subject to high drought vulnerability. With increasing drought risks, we suggest immediate and appropriate adaptation actions to be taken before 2030s, especially in Shandong and Hebei, the most vulnerable provinces of 3H plain.

Nitrogen (N) is one of the macronutrients required for plant growth, and reasonable application of N fertilizers can increase crop yields and improve their quality. However, excessive application of N fertilizers will decrease N use efficiency and also lead to increases in N2O emissions from agricultural soils and many other environmental issues. Research on the effects of different N fertilizer management practices on wheat yields and N2O emissions will assist the selection of effective N management measures which enable achieving high wheat yields while reducing N2O emissions. To investigate the effects of different N management practices on wheat yields and soil N2O emissions, we conducted field trials with 5 treatments of no N fertilizer (CK), farmers common N rate (AN), optimal N rate (ON), 20% reduction in optimal rate+dicyandiamide (ON80%+DCD), 20% reduction in optimal rate+nano-carbon (ON80%+NC). The static closed chamber gas chromatography method was used to monitor N2O emissions during the wheat growing season. The results showed that there were obvious seasonal characteristics of N2O emissions under each treatment and N2O emissions were mainly concentrated in the sowing-greening stage, accounting for 54.6–68.2% of the overall emissions. Compared with AN, N2O emissions were decreased by 23.1, 45.4 and 33.7%, respectively, under ON, ON80%+DCD and ON80%+NC, and emission factors were declined by 22.2, 66.7 and 33.3%, respectively. Wheat yield was increased significantly under ON80%+DCD and ON80%+NC by 12.3 and 11.9%, respectively, relative to AN while there was no significant change in yield in the ON treatment. Compared with ON, overall N2O emissions were decreased by 29.1 and 13.9% while wheat yields improved by 18.3 and 17.9% under ON80%+DCD and ON80%+NC, respectively. We therefore recommend that ON80%+DCD and ON80%+NC be referred as effective N management practices increasing yields while mitigating emissions.

A field experiment was conducted to explore the effects of elevated atmospheric carbon dioxide (CO2) (550 ± 17 μmol mol−1) on nitrous oxide (N2O) emissions and nitrogen (N) dynamics in a winter-wheat (Triticum aestivum L.) cropping system at the free-air CO2 enrichment (FACE) experimental facility in northern China. Compared to ambient CO2 (415 ± 16 μmol mol−1) condition, elevated CO2 increased N2O emissions by 21–36 % in the winter-wheat field. Under elevated CO2, soil total N at both 0–10 and 10–20 cm depths decreased at the ripening stage (RS) and the NH4 +-N content also decreased at the RS and the grain filling stage (GFS), while soil NO3 −-N content increased at the booting stage (BS) and RS. Elevated CO2 increased N concentrations in stem at the GFS, and leaf sheath and glumes at the RS, but decreased N concentration in spike at the GFS. Elevated CO2 increased N accumulations in leaf and stem at the GFS and in kernel, leaf sheath and glumes at the RS. The analysis shows that more N2O would be emitted from this system under the increasing atmospheric CO2 concentration with the same N fertilizer application rates. Since our results indicate that elevated CO2 could enhance plant N uptake and N2O emissions, more N is likely to be required by winter-wheat cropping systems to maintain current plant and soil N status.

Variation in nitrogen (N) acquisition ability is known to exist among maize genotypes. Field experiments were conducted and the N-efficient maize inbred line 478 and the N-inefficient line Wu312 were employed to illustrate whether the amount of N taken up in maize plants with different N acquisition ability was determined by the shoot growth potential or by the root size. To meet the accelerated growth of the shoot from the jointing stage to the grain-filling stage, the net N gain in whole plants of both genotypes increased dramatically and accounted for 77% and 74% of the total N increment in 478 and Wu312, respectively. Similarly, the 4th to 8th nodal root whorls were initiated predominantly between 35 and 76 d after sowing, which accounted for about 90% of the total root length on 93 d after sowing. The whole plant N content of the N-efficient 478 was significantly higher than that of the N-inefficient Wu312. 478 had also longer root length, including axial and lateral roots, of the embryonic roots and each whorl of shoot-borne roots, and greater root length density (RLD) than Wu312. In spite of the smaller root size, Wu312 had higher shoot N concentration than 478 during the whole growth period, implying that N was not limited for shoot growth in Wu312. It was concluded that maize root growth, especially initiation and development of the shoot-borne roots, as well as the amount of N taken up were coordinated with shoot growth and demand for nutrients. Although a large root system and high RLD in the soil profile were beneficial for efficient N acquisition, amount of N taken up by the two maize genotypes in the presence of sufficient N supply was determined by the shoot growth potential, and not by the root size.

Increasing P-use efficiency within the plant is one of the acclimations to P-limiting conditions. In this work, we studied the effects of P withdrawal during flag-leaf expansion on sink-source relationships and P-use efficiency in two detillered wheat cultivars (Triticum aestivum L., CA9325 and JM2) under controlled conditions. The study period was divided into two phases of one month each. In the first period after withdrawing P from the medium, the rates of dry weight gain were unaffected compared with the control plant. However, the net dry matter deposition in the ear, and P remobilization within the plant were accelerated in both cultivars. In control plants and in the first period, P transported in the xylem came mainly from the roots’ current uptake in both cultivars; in the second period, however, phloem retranslocation of P from the shoot and cycling through the root contributed 86% in CA9325 and 95% in JM2 to the xylem-transported P. In the P-deficient plants of both cultivars, almost all of the P transported in the xylem was remobilized, exported from vegetative organs and recycled through the phloem. Over the entire duration of the experiment, the net dry matter deposition and P allocation to grains were not synchronous, indicating independent regulatory processes. Although withdrawing P from the medium markedly reduced the net dry weight gain of whole plants in both cultivars, the final dry weight of the grains was hardly influenced. The percentage of grain dry weight to whole plant dry weight increased from 42.5% in control plants to 44.7% in P-deficient plants in CA9325, and from 41.0% to 45.0% in JM2, and that of P increased from 24.8% to 87.7% and from 25.5% to 84.3%, respectively. The results showed that withdrawing P from the medium during flag-leaf expansion did not influence grain growth and its final P content. The possible mechanisms to regulate P redistribution and reutilization in plants are discussed.

Objective: To investigate the effects of Tiaojining granule TJNG) combined with corticosterone (CS) in treating infantile primary nephrotic syndrome (IPNS).Methods: Sixty inpatients with IPNS were divided into two groups, 30 cases as the treated group treated by TJNG combined with CS, and the other 30 cases as the control group treated by CS alone for 8 weeks. The changes of urinary protein, serum albumin, blood cholesterol, platelet and blood pressure before and after treatment were observed.Results: The total effective rate of the treated group was significantly higher than that of the control group (P