| 1. |
- Yang, Danni, et al.
(författare)
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Drip irrigation improves spring wheat water productivity by reducing leaf area while increasing yield
- 2023
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Ingår i: European Journal of Agronomy. - : Elsevier BV. - 1161-0301. ; 143
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Tidskriftsartikel (refereegranskat)abstract
- To mitigate the climate change-induced water shortage and realize the sustainable development of agriculture, drip irrigation, a more efficient water-saving irrigation method, has been intensively implemented in most arid agricultural regions in the world. However, compared to traditional border irrigation, how drip irrigation affects the biophysical conditions in the cropland and how crops physiologically respond to changes in biophysical conditions in terms of water, heat and carbon exchange remain largely unknown. In view of the above situation, to reveal the mechanism of drip irrigation in improving spring wheat water productivity, paired field experiments based on drip irrigation and border irrigation were conducted to extensively monitor water and heat fluxes at a typical spring wheat field (Triticum aestivum L.) in Northwest China during 2017–2020. The results showed that drip irrigation improved yield by 10.3 % and crop water productivity (i.e., yield-to-evapotranspiration-ratio) by 15.6 %, but reduced LAI by 16.9 % in contrast with border irrigation. Under drip irrigation, the lateral development of spring wheat roots was promoted by higher soil temperature combined with frequent dry-wet alternation in the shallow soil layer (0–20 cm), which was the basis for efficient absorption of water and fertilizer, as well as efficient formation of photosynthate. Meanwhile, drip irrigation increased net radiation and decreased latent heat flux by inhibiting leaf growth, thereby increased sensible heat, causing a higher soil temperature (+1.10 ℃) and canopy temperature (+1.11 ℃). Further analysis proved that soil temperature was the key factor affecting yield formation. Based on the above conditions, the decrease in leaf distribution coefficient (−0.030) led to the decrease in evapotranspiration (−5.7 %) and the increase in ear distribution coefficient (+0.029). Therefore, drip irrigation emphasized the role of soil moisture in the soil-plant-atmosphere continuum, enhanced crop activity by increasing field temperature, especially soil temperature, and finally improved yield and water productivity via carbon reallocation. The study revealed the mechanism of drip irrigation for improving spring wheat yield, and would contribute to improving Earth system models in representing agricultural cropland ecosystems with drip irrigation and predicting the subsequent biophysical and biogeochemical feedbacks to climate change.
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| 2. |
- Zhang, Fan, et al.
(författare)
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Proliferative and Survival Effects of PUMA Promote Angiogenesis
- 2012
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Ingår i: Cell Reports. - : Elsevier (Cell Press). - 2211-1247. ; 2:5, s. 1272-1285
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Tidskriftsartikel (refereegranskat)abstract
- The p53 upregulated modulator of apoptosis (PUMA) is known as an essential apoptosis inducer. Here, we report the seemingly paradoxical finding that PUMA is a proangiogenic factor critically required for the proliferation and survival of vascular and microglia cells. Strikingly, Puma deficiency by genetic deletion or small hairpin RNA knockdown inhibited developmental and pathological angiogenesis and reduced microglia numbers in vivo, whereas Puma gene delivery increased angiogenesis and cell survival. Mechanistically, we revealed that PUMA plays a critical role in regulating autophagy by modulating Erk activation and intracellular calcium level. Our findings revealed an unexpected function of PUMA in promoting angiogenesis and warrant more careful investigations into the therapeutic potential of PUMA in treating cancer and degenerative diseases.
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| 3. |
- Chang, Kuang Yu, et al.
(författare)
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Observational constraints reduce model spread but not uncertainty in global wetland methane emission estimates
- 2023
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Ingår i: Global Change Biology. - 1354-1013. ; 29:15, s. 4298-4312
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Tidskriftsartikel (refereegranskat)abstract
- The recent rise in atmospheric methane (CH4) concentrations accelerates climate change and offsets mitigation efforts. Although wetlands are the largest natural CH4 source, estimates of global wetland CH4 emissions vary widely among approaches taken by bottom-up (BU) process-based biogeochemical models and top-down (TD) atmospheric inversion methods. Here, we integrate in situ measurements, multi-model ensembles, and a machine learning upscaling product into the International Land Model Benchmarking system to examine the relationship between wetland CH4 emission estimates and model performance. We find that using better-performing models identified by observational constraints reduces the spread of wetland CH4 emission estimates by 62% and 39% for BU- and TD-based approaches, respectively. However, global BU and TD CH4 emission estimate discrepancies increased by about 15% (from 31 to 36 TgCH4 year−1) when the top 20% models were used, although we consider this result moderately uncertain given the unevenly distributed global observations. Our analyses demonstrate that model performance ranking is subject to benchmark selection due to large inter-site variability, highlighting the importance of expanding coverage of benchmark sites to diverse environmental conditions. We encourage future development of wetland CH4 models to move beyond static benchmarking and focus on evaluating site-specific and ecosystem-specific variabilities inferred from observations.
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| 4. |
- Gao, Hongkai, et al.
(författare)
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Assessing glacier retreat and its impact on water resources in a headwater of Yangtze River based on CMIP6 projections
- 2021
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 765
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Tidskriftsartikel (refereegranskat)abstract
- Glacier retreat caused by global warming alters the hydrological regime and poses far-reaching challenges to water resources and nature conservation of the headwater of Yangtze River, and its vast downstream regions with dense population. However, there is still lack of a robust modeling framework of the “climate-glacier-streamflow” in this water tower region, to project the future changes of glacier mass balance, glacier geometry, and the consequent impacts on runoff. Moreover, it is imperative to use the state-of-the-art sixth phase Coupled Model Intercomparison Project (CMIP6) to assess glacio-hydrology variations in future. In this study, we coupled a glacio-hydrological model (FLEXG) with a glacier retreat method (Δh-parameterization) to simulate glacio-hydrological processes in the Dongkemadi Glacier (over 5155 m.a.s.l), which has the longest continuous glacio-hydrology observation on the headwater of Yangtze River. The FLEXG-Δh model was forced with in-situ observed meteorological data, radar ice thickness, remote sensing topography and land cover data, and validated by measured runoff. The results showed that the model was capable to simulate hydrological processes in this glacierized basin, with Kling-Gupta efficiency (IKGE) of daily runoff simulation 0.88 in calibration and 0.70 in validation. Then, forcing by the bias-corrected meteorological forcing from the eight latest CMIP6 Earth system models under two climate scenarios (RCP2.6 and RCP8.5), we assessed the impact of future climate change on glacier response and its hydrological effects. The results showed that, to the end of simulation in 2100, the volume of the Dongkemadi Glacier would continuously retreat. For the RCP2.6 and RCP8.5 scenarios, the glacier volume will decrease by 8.7 × 108 m3 (74%) and 10.8 × 108 m3 (92%) respectively in 2100. The glacier runoff will increase and reach to peak water around 2060 to 2085, after this tipping point water resources will likely decrease.
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| 5. |
- Li, Cheng, et al.
(författare)
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Introducing water factors improves simulations of maize stomatal conductance models under plastic film mulching in arid and semi-arid irrigation areas
- 2023
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 617
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Tidskriftsartikel (refereegranskat)abstract
- Plastic film mulching (PFM) in the cropland may alter biophysical conditions for crop growth, which may not be accounted for in existing stomatal conductance models. This can affect the accuracy of carbon–nitrogen-water cycle simulations for the soil-crop systems and hamper our understanding of internal mechanisms that control plant leaf stomatal conductance (gsw). To evaluate the simulations of PFM effects on gsw, the three models (i.e., Ball-Woodrow-Berry (BWB), Ball-Berry-Leuning (BBL), and unified stomatal optimization (USO) models) were used. The two model modification factors were leaf-air temperature difference (ΔT) and a water response function (f(θ)). A two-year maize (Zea mays L.) field experiment was conducted under different PFM (black, transparent, and no-mulch). The performance of the BWB model was poor under varying water status in the arid irrigation area. As for the BBL and USO models, the coefficient of determination and modified efficiency coefficient of the modified models increased 5.8%–90.6% and 6.5%–145.4%, respectively, compared with the initial models. The root mean square error and relative error of the modified models decreased 3.5%–67.9% and 4.8%–65.6%, respectively. The ΔT and f(θ) factors effectively improved the BBL and USO models, but the f(θ)-modified models performed better than ΔT-modified models under PFM. Overall, our results suggest that the maize land implemented with plastic film mulching has altered biophysical conditions, leading to significant changes in crop photosynthesis, leaf-air temperature difference and top-soil water conditions. Accurate estimates of stomatal conductance require the model to consider water response functions and leaf-air temperature difference, particularly in environmental conditions associated with different extents of water deficit or drought.
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| 6. |
- Li, Cheng, et al.
(författare)
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Response of plastic film mulched maize to soil and atmospheric water stresses in an arid irrigation area
- 2024
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Ingår i: European Journal of Agronomy. - 1161-0301. ; 154
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Tidskriftsartikel (refereegranskat)abstract
- Water stress can severely decrease crop productivity by restricting photosynthesis, while the use of plastic film mulching can mitigate these water stress effects. However, the intricacies of photosynthetic and stomatal responses to soil water stress under plastic film mulching, particularly when combined with atmospheric water stress, have not been well studied, especially in arid irrigation areas. Limited research has investigated photosynthetic chlorophyll fluorescence parameters, stomatal responses, grain filling process and crop productivity to soil and atmospheric water stress under plastic film mulching. Our study addresses this knowledge gap through a comprehensive field experiment in an arid irrigation area involving maize (Zea mays L.). Well-watered and water deficit conditions with and without plastic film mulching treatments, alone or combined with atmospheric water stress (different vapor pressure deficits) were conducted. Our findings revealed that soil water stress significantly increased stomatal limitations (by 6.4–12.4 %) and may cause non-stomatal limitations. Plastic film mulching significantly improved plant photosynthetic performance (increased net photosynthesis rate by 12.2–39.8 %), chlorophyll fluorescence parameters, and stomatal regulation. Under mulched conditions, soil water stress primarily affected photosynthetic performance through stomatal limitations. Moreover, plastic film mulching significantly improved grain filling process (increased grain-filling rate by 6.3–78.5 %) and productivity (increased grain yield by 12.1–45.8 %) in spring maize subjected to soil water stress. Atmospheric water stress, alone or combined with soil water stress, influenced plant photosynthetic performance, decreasing the net photosynthesis rate and stomatal conductance. Mulching enhanced photosynthetic performance under atmospheric water stress. Overall, the positive effect of mulching on spring maize photosynthetic performance and productivity under soil and atmospheric water stresses holds promise for alleviating water resource shortages and addressing global climate warming issues in arid irrigation areas.
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| 7. |
- Li, Cheng, et al.
(författare)
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Ridge planting with transparent plastic mulching improves maize productivity by regulating the distribution and utilization of soil water, heat, and canopy radiation in arid irrigation area
- 2023
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Ingår i: Agricultural Water Management. - : Elsevier BV. - 0378-3774. ; 280
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Tidskriftsartikel (refereegranskat)abstract
- Ridge-furrow mulching system is widely used for improving soil hydrothermal conditions and crop productivity in semiarid and arid rainfed areas. The response of crop productivity to resource capture and utilization is crucial for agricultural field management and sustainable development. However, few have simultaneously investigated the coupling effect of plastic film mulching (PM) types and planting patterns on root and shoot growth, photosynthesis, yield, resource capture and utilization as well as their potential links in the same experiment, especially in arid irrigation areas, limiting our understanding of PM and ridge planting application. This study conducted a two-year field experiment with four treatments: 1) flat planting with transparent plastic film mulch (FT); 2) flat planting with black plastic film mulch (FB); 3) ridge–furrow planting with transparent plastic film mulch (RT); 4) ridge–furrow planting with black plastic film mulch (RB). The results showed that RT significantly increased soil water storage and root growth at the silking and grain-filling stages in both years by enhancing soil thermal time with 151.9–176.2 °C d and the intercepted photosynthetic active radiation with 22.2–57.4 MJ m–2. In addition, RT had a significantly higher net photosynthetic rate than FT and FB at the 12-leaf and silking stages, enhancing the transportation of stem and leaf to grain. The logistic equation using growing degree days as the independent variable characterized the dynamic features of maize growth under different PM types (transparent or black) coupled with ridge–furrow planting. RT accelerated dry matter accumulation by enhancing the maximum growth rate and extending the rapid growth period, resulting in 12.9–15.2 % more dry matter accumulation and 10.0–16.7 % higher grain yields than FB. Furthermore, RT significantly increased resource use efficiencies by 10.1–17.3 % for water, 3.0–5.5 % for thermal, and 4.0–9.1 % for radiation compared with FB. Ridge planting had the highest contributor rates, with >40 % for yield and resource capture. This study suggests that RT maintains high maize productivity and resource use efficiencies in arid irrigation areas with limited water resources by regulating soil water, heat, and canopy radiation distribution and utilization.
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| 8. |
- Mu, Cuicui, et al.
(författare)
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Ecosystem CO2 Exchange and Its Economic Implications in Northern Permafrost Regions in the 21st Century
- 2023
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Ingår i: Global Biogeochemical Cycles. - 0886-6236. ; 37:11
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Tidskriftsartikel (refereegranskat)abstract
- Climate warming increases carbon assimilation by plant growth and also accelerates permafrost CO2 emissions; however, the overall ecosystem CO2 balance in permafrost regions and its economic impacts remain largely unknown. Here we synthesize in situ measurements of net ecosystem CO2 exchange to assess current and future carbon budgets across the northern permafrost regions using the random forest model and calculate their economic implications under the Shared Socio-economic Pathways (SSPs) based on the PAGE-ICE model. We estimate a contemporary CO2 emission of 1,539 Tg C during the nongrowing season and CO2 uptake of 2,330 Tg C during the growing season, respectively. Air temperature and precipitation exert the most control over the net ecosystem exchange in the nongrowing season, while leaf area index plays a more important role in the growing season. This region will probably shift to a carbon source after 2,057 under SSP5-8.5, with a net emission of 17 Pg C during 2057–2100. The net economic benefits of CO2 budget will be $4.5, $5.0, and $2.9 trillion under SSP1-2.6, SSP2-4.5, and SSP5-8.5, respectively. Our results imply that a high-emission pathway will greatly reduce the economic benefit of carbon assimilation in northern permafrost regions.
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| 9. |
- Saunois, Marielle, et al.
(författare)
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The Global Methane Budget 2000–2017
- 2020
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Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3516 .- 1866-3508. ; 12:3, s. 1561-1623
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Tidskriftsartikel (refereegranskat)abstract
- Understanding and quantifying the global methane (CH4) budget is important for assessing realistic pathways to mitigate climate change. Atmospheric emissions and concentrations of CH4 continue to increase, making CH4 the second most important human-influenced greenhouse gas in terms of climate forcing, after carbon dioxide (CO2). The relative importance of CH4 compared to CO2 depends on its shorter atmospheric lifetime, stronger warming potential, and variations in atmospheric growth rate over the past decade, the causes of which are still debated. Two major challenges in reducing uncertainties in the atmospheric growth rate arise from the variety of geographically overlapping CH4 sources and from the destruction of CH4 by short-lived hydroxyl radicals (OH). To address these challenges, we have established a consortium of multidisciplinary scientists under the umbrella of the Global Carbon Project to synthesize and stimulate new research aimed at improving and regularly updating the global methane budget. Following Saunois et al. (2016), we present here the second version of the living review paper dedicated to the decadal methane budget, integrating results of top-down studies (atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up estimates (including process-based models for estimating land surface emissions and atmospheric chemistry, inventories of anthropogenic emissions, and data-driven extrapolations).For the 2008–2017 decade, global methane emissions are estimated by atmospheric inversions (a top-down approach) to be 576 Tg CH4 yr−1 (range 550–594, corresponding to the minimum and maximum estimates of the model ensemble). Of this total, 359 Tg CH4 yr−1 or ∼ 60 % is attributed to anthropogenic sources, that is emissions caused by direct human activity (i.e. anthropogenic emissions; range 336–376 Tg CH4 yr−1 or 50 %–65 %). The mean annual total emission for the new decade (2008–2017) is 29 Tg CH4 yr−1 larger than our estimate for the previous decade (2000–2009), and 24 Tg CH4 yr−1 larger than the one reported in the previous budget for 2003–2012 (Saunois et al., 2016). Since 2012, global CH4 emissions have been tracking the warmest scenarios assessed by the Intergovernmental Panel on Climate Change. Bottom-up methods suggest almost 30 % larger global emissions (737 Tg CH4 yr−1, range 594–881) than top-down inversion methods. Indeed, bottom-up estimates for natural sources such as natural wetlands, other inland water systems, and geological sources are higher than top-down estimates. The atmospheric constraints on the top-down budget suggest that at least some of these bottom-up emissions are overestimated. The latitudinal distribution of atmospheric observation-based emissions indicates a predominance of tropical emissions (∼ 65 % of the global budget, < 30∘ N) compared to mid-latitudes (∼ 30 %, 30–60∘ N) and high northern latitudes (∼ 4 %, 60–90∘ N). The most important source of uncertainty in the methane budget is attributable to natural emissions, especially those from wetlands and other inland waters.Some of our global source estimates are smaller than those in previously published budgets (Saunois et al., 2016; Kirschke et al., 2013). In particular wetland emissions are about 35 Tg CH4 yr−1 lower due to improved partition wetlands and other inland waters. Emissions from geological sources and wild animals are also found to be smaller by 7 Tg CH4 yr−1 by 8 Tg CH4 yr−1, respectively. However, the overall discrepancy between bottom-up and top-down estimates has been reduced by only 5 % compared to Saunois et al. (2016), due to a higher estimate of emissions from inland waters, highlighting the need for more detailed research on emissions factors. Priorities for improving the methane budget include (i) a global, high-resolution map of water-saturated soils and inundated areas emitting methane based on a robust classification of different types of emitting habitats; (ii) further development of process-based models for inland-water emissions; (iii) intensification of methane observations at local scales (e.g., FLUXNET-CH4 measurements) and urban-scale monitoring to constrain bottom-up land surface models, and at regional scales (surface networks and satellites) to constrain atmospheric inversions; (iv) improvements of transport models and the representation of photochemical sinks in top-down inversions; and (v) development of a 3D variational inversion system using isotopic and/or co-emitted species such as ethane to improve source partitioning.The data presented here can be downloaded from https://doi.org/10.18160/GCP-CH4-2019 (Saunois et al., 2020) and from the Global Carbon Project.
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| 10. |
- Xia, Jianyang, et al.
(författare)
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Terrestrial ecosystem model performance in simulating productivity and its vulnerability to climate change in the northern permafrost region
- 2017
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Ingår i: Journal of Geophysical Research - Biogeosciences. - 2169-8953. ; 122:2, s. 430-446
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Tidskriftsartikel (refereegranskat)abstract
- Realistic projection of future climate-carbon (C) cycle feedbacks requires better understanding and an improved representation of the C cycle in permafrost regions in the current generation of Earth system models. Here we evaluated 10 terrestrial ecosystem models for their estimates of net primary productivity (NPP) and responses to historical climate change in permafrost regions in the Northern Hemisphere. In comparison with the satellite estimate from the Moderate Resolution Imaging Spectroradiometer (MODIS; 246±6gCm-2yr-1), most models produced higher NPP (309±12gCm-2yr-1) over the permafrost region during 2000-2009. By comparing the simulated gross primary productivity (GPP) with a flux tower-based database, we found that although mean GPP among the models was only overestimated by 10% over 1982-2009, there was a twofold discrepancy among models (380 to 800gCm-2yr-1), which mainly resulted from differences in simulated maximum monthly GPP (GPPmax). Most models overestimated C use efficiency (CUE) as compared to observations at both regional and site levels. Further analysis shows that model variability of GPP and CUE are nonlinearly correlated to variability in specific leaf area and the maximum rate of carboxylation by the enzyme Rubisco at 25°C (Vcmax_25), respectively. The models also varied in their sensitivities of NPP, GPP, and CUE to historical changes in climate and atmospheric CO2 concentration. These results indicate that model predictive ability of the C cycle in permafrost regions can be improved by better representation of the processes controlling CUE and GPPmax as well as their sensitivity to climate change.
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