China’s Greening Modulated the Reallocation of the Evapotranspiration Components during 2001–2020

Increasing numbers of observations and research studies have detected widespread vegetation greening across China since the 1980s. The dynamics of vegetation can influence the process of terrestrial evapotranspiration (ET) and its components (vegetation transpiration (Ec), soil evaporation (Es), and intercepted precipitation evaporation (Ei)). However, it is still not clear how the ET components responded to China’s greening. This work investigated the characteristics and dynamics of ET components for different climate zones and moisture regions and the dominant ecosystems over China using PML ET products during 2001–2020. The results showed that ET increased by 9%, Ec and Ec/ET increased by 18.7% and 4.4%, respectively, contributing to more than 90% of the ET increment across China. The increment in Ec generally increased from north to south with the most obvious change of Ec/ET having occurred in the temperate zone and semi-humid regions. Es increased in arid, semi-arid and plateau climate regions but decreased in the remaining climate zones. As a result, Es only decreased by 2.7% on average, while Es/ET decreased by 5.7%. Ei increased by 26.6% across China, while Ei/ET changed slightly due to the little contribution of Ei to ET. The agricultural ecosystem presented the most obvious change of Ec and Es among the dominant ecosystems, and the most obvious change of Ei occurred in the forest ecosystem. Vegetation greening altered biophysical factors that govern heat and vapor exchange in the soil-plant-atmosphere continuum, thus modulating the reallocation of ET components

China’s Greening Modulated the Reallocation of the Evapotranspiration Components during 2001–2020

Increasing numbers of observations and research studies have detected widespread vegetation greening across China since the 1980s. The dynamics of vegetation can influence the process of terrestrial evapotranspiration (ET) and its components (vegetation transpiration (Ec), soil evaporation (Es), and intercepted precipitation evaporation (Ei)). However, it is still not clear how the ET components responded to China’s greening. This work investigated the characteristics and dynamics of ET components for different climate zones and moisture regions and the dominant ecosystems over China using PML ET products during 2001–2020. The results showed that ET increased by 9%, Ec and Ec/ET increased by 18.7% and 4.4%, respectively, contributing to more than 90% of the ET increment across China. The increment in Ec generally increased from north to south with the most obvious change of Ec/ET having occurred in the temperate zone and semi-humid regions. Es increased in arid, semi-arid and plateau climate regions but decreased in the remaining climate zones. As a result, Es only decreased by 2.7% on average, while Es/ET decreased by 5.7%. Ei increased by 26.6% across China, while Ei/ET changed slightly due to the little contribution of Ei to ET. The agricultural ecosystem presented the most obvious change of Ec and Es among the dominant ecosystems, and the most obvious change of Ei occurred in the forest ecosystem. Vegetation greening altered biophysical factors that govern heat and vapor exchange in the soil-plant-atmosphere continuum, thus modulating the reallocation of ET components

Evapotranspiration Components Dynamic of Highland Barley Using PML ET Product in Tibet

Highland barley is the unique germplasm resource and dominant crop in Tibet with low-level precipitation and a severe shortage of available water resources. Understanding the characteristics and dynamics of evapotranspiration (ET) components (vegetation transpiration (Ec), soil evaporation (Es), and canopy interception evaporation (Ei)) of highland barley can help better optimize water management practices. The seasonal and interannual variations in ET components of highland barley were investigated using the PML-V2 ET product during 2001–2020. The results suggested that Es was the most important ET component and accounted for 77% of total ET for highland barley in Tibet. ET components varied obviously over the altitude, Es, and Es/ET ratio; a decreasing trend was observed with the increase in altitude from 3500 m to 3800 m and then this changed to an increasing trend until reaching the altitude of 4100 m, while Ec, Ei, and their ratios presented an opposite changing pattern to that of Es. Seasonal variation in daily ET components of highland barley displayed a parabolic pattern, peaked in August, while the temporal distributions differed considerably among different ET component ratios. The seasonal variations in ET components were correlated significantly with air temperature, relative humidity, and precipitation, while ET components ratios were more influenced by the environment, irrigation practice, and management rather than meteorological variables. Es and its ratio in highland barley decreased significantly during 2001–2020, while the Ec/ET ratio generally showed an opposite trend to the Es/ET ratio, and Ei and its ratio presented an insignificantly decreasing trend. The interannual variations in ET components were not correlated significantly with meteorological variables, while Ei was more influenced by meteorological variables, especially the precipitation characteristics

Dynamics of the Evaporation of Intercepted Precipitation during the Last Two Decades over China

The evaporation of intercepted precipitation (Ei) is an important component of evapotranspiration. Investigating the spatial and temporal variations of Ei and its driving factors can improve our understanding of water and energy balance in the context of China’s greening. This study investigated the spatial and temporal variation of Ei across China during 2001−2020 using PML ET product with a temporal resolution of 8 days and a spatial resolution of 500 m. The results showed that Ei generally decreased from southeast to northwest, which was contributed by the coupled effect of precipitation and vegetation coverage variation across China. Generally, Ei showed an increasing trend over the last two decades with an average changing rate of 0.45 mm/year. The changing rate varied greatly among different regions, with the most obvious change occurring in tropical and humid regions. Precipitation was the most important climatic factor driving the interannual change of Ei over the past two decades, with an average contribution rate of 30.18~37.59%. Relative humidity was the second most important climatic factor following precipitation. Temperature showed contracting contribution in different thermal regions. The contribution rates of NDVI and LAI followed a similar spatial pattern. Both the contribution rates of NDVI and LAI generally increased along the moisture gradient from east to west and generally increased from south to north

Dynamics of the Evaporation of Intercepted Precipitation during the Last Two Decades over China

The evaporation of intercepted precipitation (Ei) is an important component of evapotranspiration. Investigating the spatial and temporal variations of Ei and its driving factors can improve our understanding of water and energy balance in the context of China’s greening. This study investigated the spatial and temporal variation of Ei across China during 2001−2020 using PML ET product with a temporal resolution of 8 days and a spatial resolution of 500 m. The results showed that Ei generally decreased from southeast to northwest, which was contributed by the coupled effect of precipitation and vegetation coverage variation across China. Generally, Ei showed an increasing trend over the last two decades with an average changing rate of 0.45 mm/year. The changing rate varied greatly among different regions, with the most obvious change occurring in tropical and humid regions. Precipitation was the most important climatic factor driving the interannual change of Ei over the past two decades, with an average contribution rate of 30.18~37.59%. Relative humidity was the second most important climatic factor following precipitation. Temperature showed contracting contribution in different thermal regions. The contribution rates of NDVI and LAI followed a similar spatial pattern. Both the contribution rates of NDVI and LAI generally increased along the moisture gradient from east to west and generally increased from south to north

Evapotranspiration Components Dynamic of Highland Barley Using PML ET Product in Tibet

Highland barley is the unique germplasm resource and dominant crop in Tibet with low-level precipitation and a severe shortage of available water resources. Understanding the characteristics and dynamics of evapotranspiration (ET) components (vegetation transpiration (Ec), soil evaporation (Es), and canopy interception evaporation (Ei)) of highland barley can help better optimize water management practices. The seasonal and interannual variations in ET components of highland barley were investigated using the PML-V2 ET product during 2001–2020. The results suggested that Es was the most important ET component and accounted for 77% of total ET for highland barley in Tibet. ET components varied obviously over the altitude, Es, and Es/ET ratio; a decreasing trend was observed with the increase in altitude from 3500 m to 3800 m and then this changed to an increasing trend until reaching the altitude of 4100 m, while Ec, Ei, and their ratios presented an opposite changing pattern to that of Es. Seasonal variation in daily ET components of highland barley displayed a parabolic pattern, peaked in August, while the temporal distributions differed considerably among different ET component ratios. The seasonal variations in ET components were correlated significantly with air temperature, relative humidity, and precipitation, while ET components ratios were more influenced by the environment, irrigation practice, and management rather than meteorological variables. Es and its ratio in highland barley decreased significantly during 2001–2020, while the Ec/ET ratio generally showed an opposite trend to the Es/ET ratio, and Ei and its ratio presented an insignificantly decreasing trend. The interannual variations in ET components were not correlated significantly with meteorological variables, while Ei was more influenced by meteorological variables, especially the precipitation characteristics

Dynamics of Mid-Channel Bar during Different Impoundment Periods of the Three Gorges Reservoir Area in China

The dynamics of the mid-channel bars (MCBs) in the Three Gorges Reservoir (TGR) were substantially impacted by the large water-level changes due to the impoundments of the TGR. However, it is still not clear how the morphology of the MCBs changed under the influence of water level and hydrological regime changes induced by the impoundments and operation of the TGR. In this work, the MCBs in the TGR were retrieved using Landsat remote sensing images from 1989 to 2019, and the spatio-temporal variations in the number, area, morphology and location of the MCBs during different impoundment periods were investigated. The results showed that the number and area of MCBs changed dramatically with water-level changes, and the changes were dominated by MCBs with an area less than 0.03 km2 and larger than 1 km2. The area of MCBs decreased progressively with the rising water level, and the number generally showed a decreasing trend, with the minimum number occurring at the third stage when the water level reached 139 m, resulting in the maximum average area at this period. The ratio of length to width of the MCBs generally decreased with the changes in hydrological and sediment regimes, leading to a shape adjustment from narrow–long to relatively short–round with the rising of the water level. The water impoundments of the TGR led to the migration of the dominant area from the upper section to the middle section of the TGR and resulted in a more even distribution of MCBs in the TGR. The results improve our understanding of the mechanisms of the development of MCBs in the TGR under the influence of water impoundment coupled with the annually cyclic hydrological regime and longer periods of inundation and exposure

A higher river sinuosity increased riparian soil structural stability on the downstream of a dammed river.

From PubMed via Jisc Publications RouterHistory: received 2021-05-20, revised 2021-08-20, accepted 2021-08-20Publication status: aheadofprintHydropower dam constructions and operations have dramatically changed the original hydrological regime of natural rivers. Because of significantly slashed and suspended sediments blocked by damming, discharged "clear" water was found to play a strong undercutting effect on the riverbank and to exacerbate riparian soil erosion on the downstream near dams. Yet, it is still an unsettled issue whether the instability of riparian soil structure would be simply correlated negatively with the distance to a dam. In this study, soils along the downstream riparian zone of a huge dam on the River Yangtze, China, were sampled to examine the distance effect on the riparian soil structural stability. Water-stable aggregates were fractionated by the wet-sieving method. Mean weight diameter (MWD) and geometric mean diameter (GMD) were used to indicate riparian soil stability. Further, the fractal dimension (D) and soil erodibility parameter (K) were used to represent the likelihood of riparian erosion. Our results revealed that riparian soil structural stability demonstrated a high spatial heterogeneity along the River Yangtze, and was less affected by the spatial distance to the dam. Rather, the soil stability was primarily influenced by a river shape index (sinuosity) and local edaphic properties. The river sinuosity index demonstrated a positive relationship with soil structural stability. Additionally, soil organic matter was found as a major edaphic factor in stabilizing soil structure. The results indicated that river sinuosity plays a crucial role in stabilizing soil by accumulating soil organic matters. Our findings implied that the potential negative impact of damming effect on soil stability may be attenuated by maintaining a higher sinuosity of the river. Against the risk of riparian soil erosion along the dammed river, the configuration of river morphology shall be considered as one of the potential managements in offsetting the negative impacts of damming. [Abstract copyright: Copyright © 2021. Published by Elsevier B.V.

Biochanin A Reduces Inflammatory Injury and Neuronal Apoptosis following Subarachnoid Hemorrhage via Suppression of the TLRs/TIRAP/MyD88/NF-κB Pathway

Inflammatory injury and neuronal apoptosis participate in the period of early brain injury (EBI) after subarachnoid hemorrhage (SAH). Suppression of inflammation has recently been shown to reduce neuronal death and neurobehavioral dysfunction post SAH. Biochanin A (BCA), a natural bioactive isoflavonoid, has been confirmed to emerge the anti-inflammatory pharmacological function. This original study was aimed at evaluating and identifying the neuroprotective role of BCA and the underlying molecular mechanism in an experimental Sprague-Dawley rat SAH model. Neurobehavioral function was evaluated via the modified water maze test and modified Garcia neurologic score system. Thus, we confirmed that BCA markedly decreased the activated level of TLRs/TIRAP/MyD88/NF-κB pathway and the production of cytokines. BCA also significantly ameliorated neuronal apoptosis which correlated with the improvement of neurobehavioral dysfunction post SAH. These results indicated that BCA may provide neuroprotection against EBI through the inhibition of inflammatory injury and neuronal apoptosis partially via the TLRs/TIRAP/MyD88/NF-κB signal pathway