17:15 〜 18:30
[AHW20-P03] Vegetation response to soil moisture and groundwater in west-central Africa revealed by satellite observations
キーワード：GRACE、アフリカ、AMSR-E、衛星観測、葉面積指数
Vegetation is always exposed to environmental changes, and vegetation green-up is mainly affected by water in arid lands. Root systems primarily carry out water intake by terrestrial plants. Therefore, it is vital to grasp soil water for the investigation of vegetation responses to water. However, in-situ data are generally limited and spatially sparse. We investigated the relationship between water availability and vegetation growth in west-central Africa, which contains dry regions south of the Sahara Desert and wet regions in the Equatorial region. Used satellite observation data including Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) Soil Moisture Content (SMC), i.e., reflecting soil moisture in the near-surface layer, and Gravity Recovery and Climate Experiment (GRACE) Terrestrial Water Storage (TWS), i.e., reflecting terrestrial water change.
We performed multiple regression analysis using Leaf Area Index (LAI) as the response variable and considering SMC and TWS as explanatory variables. The relationship between the SMC and LAI is vital in the region covered by annual plants, utilizing only near-surface soil water because of the shallow rooting system. The region’s relationship covered by perennial plants is relatively weak, caused by a more in-depth rooting system. TWS contains soil water that cannot be used by plants because of too deep. Therefore, the relationship between LAI and TWS is weak.
We found that TWS decline during the primary dry season becomes more pronounced toward the equatorial region. Thus, we assessed the relationship between TWS fluctuation and LAI in the preceding dry season. We confirmed the strong negative relationship between LAI and the inclination of TWS change in areas that receive very little rainfall during the considered period, which may be caused by clarifying vegetation activities’ difference by a scant supply of water.
The above findings suggest that it can be possible to investigate the relationship between soil water and vegetation using microwave signatures in the regions covered by annual plants and those in the regions covered by perennial plants by focusing on TWS decline.Following this, it is necessary to consider the water availability and investigate the relationship in the equatorial region and other regions during the rainy season to grasp vegetation’s water stress due to the effects of cloud cover.
We performed multiple regression analysis using Leaf Area Index (LAI) as the response variable and considering SMC and TWS as explanatory variables. The relationship between the SMC and LAI is vital in the region covered by annual plants, utilizing only near-surface soil water because of the shallow rooting system. The region’s relationship covered by perennial plants is relatively weak, caused by a more in-depth rooting system. TWS contains soil water that cannot be used by plants because of too deep. Therefore, the relationship between LAI and TWS is weak.
We found that TWS decline during the primary dry season becomes more pronounced toward the equatorial region. Thus, we assessed the relationship between TWS fluctuation and LAI in the preceding dry season. We confirmed the strong negative relationship between LAI and the inclination of TWS change in areas that receive very little rainfall during the considered period, which may be caused by clarifying vegetation activities’ difference by a scant supply of water.
The above findings suggest that it can be possible to investigate the relationship between soil water and vegetation using microwave signatures in the regions covered by annual plants and those in the regions covered by perennial plants by focusing on TWS decline.Following this, it is necessary to consider the water availability and investigate the relationship in the equatorial region and other regions during the rainy season to grasp vegetation’s water stress due to the effects of cloud cover.