| 1. |
- Lu, Mengge, et al.
(författare)
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Projections of thermal growing season indices over China under global warming of 1.5 °C and 2.0 °C
- 2021
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 781
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Tidskriftsartikel (refereegranskat)abstract
- Global warming may prolong and intensify the thermal growing season of vegetation. It is not yet clear how the Paris Agreement's long-term temperature goals will affect the thermal growing season of vegetation, particularly crops, in China. Based on the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) datasets and the Global Gridded Crop Model Intercomparison (GGCMI) phase 1 dataset, we have investigated changes in spatiotemporal patterns of four thermal growing season indices (Growing Degree Days, GDD; Length of Growing Season, GSL; the Start of Growing Season, GSS; the End of Growing Season, GSE) over China under global warming scenarios of 1.5 °C and 2.0 °C with four representative concentration pathway (RCP) scenarios. Our results indicate that during the periods which achieve the global warming of 1.5 °C and 2.0 °C, only 3.82% and 29.15% of the total areas in China have higher warming levels beyond the global warming targets. For warmer RCP scenarios (except RCP2.6), there was a rising trend for GSE, GDD and GSL and a decreasing trend for GSS in China. Many crop regions in China have also shown an advance of GSS, an extension of GSL and an earlier end of GSE under the global warming of 1.5 °C and 2.0 °C, suggesting that crop planting and harvesting dates need to be adjusted accordingly in order to capture appropriate timing for crop maturity and to achieve a maximum yield.
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| 2. |
- Sun, Huaiwei, et al.
(författare)
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Drivers of the water use efficiency changes in China during 1982–2015
- 2021
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 799
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the drivers of water use efficiency (WUE), a key metric of water resources management, and its changes over eight regions across China from 1982 to 2015 based on gross primary production (GPP) and actual evapotranspiration (AET) datasets. The order of seasonal change of WUE from large to small is autumn, summer, spring and winter. The drivers include seven variables, air temperature, specific humidity, precipitation, short-wave radiation, Normalized Difference Vegetation Index (NDVI), soil moisture and CO2. Our analysis suggests that the sensitivity of annual average NDVI to WUE changes was high nationwide, but there were some differences in seasonal scales. The annual average contribution of air temperature and CO2 affecting WUE change was relatively high in China's largest area (SW, SE, E, NP). Other influencing factors were only relatively high in the local area. Seasonally, NDVI is the driving factor with the highest contribution rate in summer and autumn for NC and NW region. The seasonal contribution rates of driving factors in other regions are significantly different. For the study period (1982–2015), the shrubland ecosystem had the highest annual WUE followed by forest and cropland. The WUE of the farmland ecosystem was higher than that of the grassland ecosystem in most areas.
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| 3. |
- Sun, Huaiwei, et al.
(författare)
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Revisiting the role of transpiration in the variation of ecosystem water use efficiency in China
- 2023
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Ingår i: Agricultural and Forest Meteorology. - : Elsevier BV. - 0168-1923. ; 332
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Tidskriftsartikel (refereegranskat)abstract
- Efforts to develop effective climate strategies necessitate a better understanding of the relationship between terrestrial water and carbon cycles. Water use efficiency (WUE) has been often used to characterize this relationship, while the role of transpiration (T) in the variation of ecosystem WUE has been less investigated. Here, we partitioned WUEET (the ratio of gross primary productivity (GPP) to evapotranspiration (ET)) into a two-component process, i.e., the ratio of gross primary productivity to plant transpiration, GPP/T, that is WUET, and the ratio of plant transpiration to evapotranspiration, T/ET. Based on two GPP datasets (i.e., GPP based on the light use efficiency model or the vegetation index- NIRv) and the GLEAM ET dataset, this study investigated the role of T in the variation of WUE in the ecosystem level and how the role is affected by drought. We found that drought can lead to the change of ET partitioning, thus affecting the variability of WUE. The variability of WUEET was dominated by WUET. In general, the proportion of T increased gradually from humid to arid areas. To adapt to drought conditions, vegetation in arid areas tend to have a high stress resistance by increasing their WUE. We further found that WUET has stronger seasonal stability than WUEET. GPP dominated WUEET variability in humid/sub humid areas, while ET and GPP jointly dominated WUEET variability in semi-arid/arid areas. GPP dataset based on light use efficiency (LUE) could better reflect the impact of drought on vegetation. This study contributes to a better understanding of the change mechanism of ecosystem WUE and emphasizes the critical role of physiological process components in water-carbon cycling.
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| 4. |
- Sun, Huaiwei, et al.
(författare)
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The altered drivers of evapotranspiration trends around the recent warming hiatus in China
- 2022
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Ingår i: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 42:16, s. 8405-8422
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on the trends and the causes of variation in actual evapotranspiration (AET) around the warming hiatus over China by a comprehensive analysis applying various temporal–spatial methods. It is observed that the annual AET showed a different trend around 2000 for China as a whole. By employing segmented regression analysis for detecting warming hiatus points, high temporal inconsistency can be found in eight climatic regions of China. The impacts of meteorological variables on AET were further identified by affecting the intensity and relative change of meteorological factors. AET was highly correlated (p <.01) with solar radiation in the southeast (R = 0.80) and air specific humidity in the northwest areas (R = 0.83). AET changes presented the highest sensitivity to specific humidity in Northwest before 2006 and in north central China after 2003, with sensitivity coefficients of 1.48 and 1.74, respectively. Three variables, including air specific humidity (with an average contribution rate of ~17% in the northwest), short-wave radiation and air temperature, can be the main factors that lead to the changes in AET. The specific meteorological factors varied from region to region: the changes in AET can be ascribed to the increased wind and short-wave radiation in north central China and east China, the decreased air temperature in Tibetan Plateau, the increased specific humidity in southeast China during warming hiatus, and so on. After the warming hiatus occurred, the dominant factor of AET trends changed from air specific humidity to short-wave radiation and other factors. Generally, air specific humidity and air temperature have played leading roles in AET trends during the past 30 years.
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