Responses of ecosystem water use efficiency to drought in the Lancang–Mekong River Basin

Abstract

The ecosystem water use efficiency (WUE), a crucial indicator of how climate change will affect terrestrial ecosystems, depicts the coupling of the carbon gain and water loss in terrestrial ecosystems. In this study, the spatiotemporal variations in the WUE and its responses to drought in the Lancang–Mekong River Basin (LMRB) from 1982 to 2018 were investigated using the gross primary productivity (GPP) and evapotranspiration (ET) data acquired from the Global Land Surface Satellite (GLASS) products. The analyses revealed that: (1) the mean yearly WUE for the LMRB was 1.63 g C kg−1 H2O, with comparatively higher values in forests and warm temperate climatic types. The interaction of temperature and leaf area index was the main factor affecting the spatial distribution of WUE. The yearly WUE for the entire region exhibited a decreasing trend with a rate of −0.0009 g C kg −1 H2O·yr−1, and the spatially significantly decreasing area accounted for 41.67% of the total area. (2) The annual WUE was positively correlated with drought in the humid regions, accounting for 66.55% of the total area, while a negative relationship mainly occurred in the high-altitude cold region. (3) The ecosystem WUE lagged behind the drought by 3 months in most regions. The lag effect was more apparent in the grassland-dominated upstream region and the cropland-dominated Mekong Delta. (4) The resilience analysis revealed that the ecosystems in forests and temperate climate types were strongly resistant to drought, while the grassland and high-altitude regions with a dry and cold climate had relatively poor resilience. The results of this study shed light on how the WUE responds to drought across diverse land use types, climate types, and elevation gradients, uncovering fresh insights into the potential mechanisms behind the impact of drought on water and carbon cycles within ecosystems.

Teleconnections of Atmospheric Circulations to Meteorological Drought in the Lancang-Mekong River Basin

“…The findings revealed that meteorological drought events occurred frequently in the basin in recent years, particularly during the periods of 2004-2005, 2009-2010, 2012-2013, and 2015-2016, with long durations and severe drought conditions. These results are consistent with the historical natural disaster records of the LMRB in the international disaster database (https://public.emdat.be/data/ accessed on 1 October 2023) and with the results of previous studies [27,29]. In addition, by comparing the frequency and spatial distribution characteristics of meteorological drought events in the rainy season and dry season, and interannually in the LMRB, it was observed that even during the rainy season, meteorological drought events still occurred in the basin.…”

“…However, in recent years, the LMRB has been experiencing a worrisome escalation in both the frequency and severity of drought events, primarily attributed to the pervasive influence of global climate change. This distressing trend has resulted in far-reaching consequences for various sectors, including domestic water consumption, agricultural irrigation, ecological balance, and navigational activities across the countries encompassing the basin [28,29]. Thus, this study aimed to analyze the meteorological drought characteristics in the LMRB and identify the impact and correlation of atmospheric circulations on the meteorological drought in the basin.…”

Spatial and temporal variations of vegetation water use efficiency and its response to climate change and human activities in the West Liao River Plain, China

“…But the use of remote sensing data, especially that from the same sensor inevitably introduces some potential uncertainties such as data self-correlated problem. Besides MODIS data, more and more remote sensing data products were used in WUE calculated such as GLASS data (Luo et al, 2023), Sentinel-2 data (Elfarkh et al, 2023) and PML-V2 product (He S. Y. et al, 2022;Ji et al, 2023). Different data sources may result in differences in evaluation results due to differences in resolution and model.…”