scholarly journals Remote Sensing of Water Use Efficiency and Terrestrial Drought Recovery across the Contiguous United States

2019 ◽  
Vol 11 (6) ◽  
pp. 731 ◽  
Author(s):  
Behzad Ahmadi ◽  
Ali Ahmadalipour ◽  
Glenn Tootle ◽  
Hamid Moradkhani
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Land Surface ◽  
Terrestrial Ecosystems ◽  
Agricultural Drought ◽  
Carbon Gain ◽  
Drought Severity ◽  
Drought Recovery ◽  
Ecosystem Water Use Efficiency ◽  
Use Efficiency

Ecosystem water-use efficiency (WUE) is defined as the ratio of carbon gain (i.e., gross primary productivity; GPP) to water consumption (i.e., evapotranspiration; ET). WUE is markedly influential on carbon and water cycles, both of which are fundamental for ecosystem state, climate and the environment. Drought can affect WUE, subsequently disturbing the composition and functionality of terrestrial ecosystems. In this study, the impacts of drought on WUE and its components (i.e., GPP and ET) are assessed across the Contiguous US (CONUS) at fine spatial and temporal resolutions. Soil moisture simulations from land surface modeling are utilized to detect and characterize agricultural drought episodes and remotely sensed GPP and ET are retrieved from the moderate resolution imaging spectroradiometer (MODIS). GPP, as the biome vitality indicator against drought stress, is employed to investigate drought recovery and the ecosystems’ required time to revert to pre-drought condition. Results show that drought recovery duration indicates a positive correlation with drought severity and duration, meaning that a protracted drought recovery is more likely to happen following severe droughts with prolonged duration. WUE is found to almost always increase in response to severe (or worse) drought episodes. Additionally, ET anomalies are negatively correlated with drought severity and ET is expected to decrease during severe (or worse) drought episodes. Lastly, the changes of WUE are decomposed in relation to its components and the cross-relation among the variables is revealed and a consistent changing pattern is detected.

scholarly journals Responses of Water Use Efficiency to Drought in Southwest China

2020 ◽  
Vol 12 (1) ◽  
pp. 199 ◽  
Author(s):  
Jingxue Zhao ◽  
Tongren Xu ◽  
Jingfeng Xiao ◽  
Shaomin Liu ◽  
Kebiao Mao ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Southwest China ◽  
Vegetation Type ◽  
Terrestrial Ecosystems ◽  
Temporal Variations ◽  
Drought Severity ◽  
Enhancement Effect ◽  
Severe Drought ◽  
Use Efficiency

Water use efficiency (WUE) measures the tradeoff between carbon uptake and water consumption in terrestrial ecosystems. It remains unclear how the responses of WUE to drought vary with drought severity. We assessed the spatio-temporal variations of ecosystem WUE and its responses to drought for terrestrial ecosystems in Southwest China over the period 2000–2017. The annual WUE values varied with vegetation type in the region: Forests (3.25 gC kg−1H2O) > shrublands (2.00 gC kg−1H2O) > croplands (1.76 gC kg−1H2O) > grasslands (1.04 gC kg−1H2O). During the period 2000–2017, frequent droughts occurred in Southwest China, and overall, drought had an enhancement effect on WUE. However, the effects of drought on WUE varied with vegetation type and drought severity. Croplands were the most sensitive to drought, and slight water deficiency led to the decline of cropland WUE. Over grasslands, mild drought increased its WUE while moderate and severe drought reduced its WUE. For forests and shrublands, mild and moderate drought increased their WUE, and only severe drought reduce their WUE, indicating that these ecosystems had stronger resistance to drought. Assessing the patterns and trends of ecosystem WUE and its responses to drought are essential for understanding plant water use strategy and informing ecosystem water management.

scholarly journals Quantifying Soil Moisture Impacts on Water Use Efficiency in Terrestrial Ecosystems of China

2021 ◽  
Vol 13 (21) ◽  
pp. 4257
Author(s):  
Xingming Hao ◽  
Jingjing Zhang ◽  
Xue Fan ◽  
Haichao Hao ◽  
Yuanhang Li
Keyword(s):  
Soil Moisture ◽  
Water Use Efficiency ◽  
Water Use ◽  
Land Surface ◽  
Net Primary Production ◽  
Terrestrial Ecosystems ◽  
Sensitivity Coefficient ◽  
Analytical Framework ◽  
Average Value ◽  
Use Efficiency

Soil moisture (SM) significantly affects the exchange of land surface energy and the stability of terrestrial ecosystems. Although some conclusions have been drawn about the effects of SM on the ecosystem water use efficiency (WUE), the influence mechanism and the quantitative assessment framework of SM on WUE are still unclear. This study provides an analysis framework for the feedback relationship between SM and WUE based on the dependence of the evaporation fraction on SM and output datasets from remote sensing and the Global Land Data Assimilation System. The results show that the range of WUE of terrestrial ecosystems of China was0.02–19.26 g C/kg H2O in the growing season with an average value of 1.05 g C/kg H2O. They also show a downward trend in43.99% of the total area. In the evapotranspiration (ET) pathway, SM negatively affected WUE, and the sensitivity coefficient ranged from −18.49 to −0.04. In the net primary production (NPP) pathway, the sensitivity coefficient ranged from −68.66 to 43.19. Under the dual effects of the ET and NPP pathways, the influence of SM on WUE was negative in 84.62% of the area. Variation in SM led to significant WUE variability. Generally, the percentage change in WUE (ΔWUE) ranged from 0% to 190.86%, with an average value of 28.02%. The maximum ΔWUE ranged from 0% to 758.78%, with an average value of 109.29%. The WUE of forest ecosystems showed strong resistance to SM variation, whereas that of non-forest vegetation was more sensitive to SM variation. This analytical framework provides a new perspective on the feedback relationship between WUE and SM in terrestrial ecosystems.

scholarly journals Effects of Climate Factors and Human Activities on the Ecosystem Water Use Efficiency throughout Northern China

2019 ◽  
Vol 11 (23) ◽  
pp. 2766 ◽  
Author(s):  
Xiaozheng Du ◽  
Xiang Zhao ◽  
Tao Zhou ◽  
Bo Jiang ◽  
Peipei Xu ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Human Activities ◽  
Large Scale ◽  
Terrestrial Ecosystems ◽  
Northern China ◽  
Climate Factors ◽  
Ecosystem Water Use Efficiency ◽  
Use Efficiency ◽  
The Impact

Global climate changes have increased the imbalance of water resources, especially in northern China, which comprises typical arid and semiarid regions. Large-scale afforestation has been implemented over the past three decades in northern China. The ecosystem water use efficiency (WUE) connects the carbon cycle and water cycle of the terrestrial ecosystems and is defined as the ratio of the gross primary productivity (GPP) to the evapotranspiration. However, there are still an insufficient number of studies on the impact of the afforestation on the WUE. In this study, we applied the random forest (RF) model to explore the impacts of climate and nonclimate factors on the WUE in northern China. The results showed that in areas with high precipitation, the forests had the highest WUE, while in the arid areas, the croplands had the highest WUE. Of the total area, 44.34% showed a significant increase, and 5.89% showed a significant decrease in the WUE from 1982–2015 in northern China. The main driving factors for the changes in the WUE were climate factors, including the precipitation, temperature and solar radiation, which contributed to approximately 84% of the WUE trends, while human activities, such as afforestation, contributed to approximately 16% of the WUE trends. Overall, although the climate had a larger impact on the WUE dynamics than the human activities, our results suggested that the impacts of the afforestation programs on forest carbon and water cycles should be considered in the context of climate change.

scholarly journals Assessing the Response of Ecosystem Water Use Efficiency to Drought During and after Drought Events across Central Asia

Sensors ◽  
2020 ◽  
Vol 20 (3) ◽  
pp. 581 ◽  
Author(s):  
Jie Zou ◽  
Jianli Ding ◽  
Martin Welp ◽  
Shuai Huang ◽  
Bohua Liu
Keyword(s):  
Water Use Efficiency ◽  
Central Asia ◽  
Water Use ◽  
Severe Drought ◽  
Vegetation Types ◽  
Drought Period ◽  
Legacy Effect ◽  
Ecosystem Water Use Efficiency ◽  
Use Efficiency ◽  
The Mean

The frequency and intensity of drought are expected to increase worldwide in the future. However, it is still unclear how ecosystems respond to drought. Ecosystem water use efficiency (WUE) is an essential ecological index used to measure the global carbon–water cycles, and is defined as the carbon absorbed per unit of water lost by the ecosystem. In this study, we applied gross primary productivity (GPP), evapotranspiration (ET), land surface temperature (LST), and normalized difference vegetation index (NDVI) data to calculate the WUE and drought index (temperature vegetation dryness index (TVDI)), all of which were retrieved from moderate resolution imaging spectroradiometer (MODIS) data. We compared the mean WUE across different vegetation types, drought classifications, and countries. The temporal and spatial changes in WUE and drought were analyzed. The correlation between drought and WUE was calculated and compared across different vegetation types, and the differences in WUE between drought and post-drought periods were compared. The results showed that (1) ecosystems with a low (high) productivity had a high (low) WUE, and the mean ecosystem WUE of Central Asia showed vast differences across various drought levels, countries, and vegetation types. (2) The WUE in Central Asia exhibited an increasing trend from 2000 to 2014, and Central Asia experienced both drought (from 2000 to 2010) and post-drought (from 2011 to 2014) periods. (3) The WUE showed a negative correlation with drought during the drought period, and an obvious drought legacy effect was found, in which severe drought affected the ecosystem WUE over the following two years, while a positive correlation between WUE and drought was found in the post-drought period. (4) A significant increase in ecosystem WUE was found after drought, which revealed that arid ecosystems exhibit high resilience to drought stress. Our results can provide a specific reference for understanding how ecosystems will respond to climate change.

Environmental and canopy stomatal control on ecosystem water use efficiency in a riparian poplar plantation

2020 ◽  
Vol 287 ◽  
pp. 107953 ◽  
Author(s):  
Hang Xu ◽  
Zhiqiang Zhang ◽  
Jingfeng Xiao ◽  
Jiquan Chen ◽  
Mengxun Zhu ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Poplar Plantation ◽  
Stomatal Control ◽  
Ecosystem Water Use Efficiency ◽  
Use Efficiency
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