Abstract
Soil water use efficiency (SWUE) was proposed as an effective proxy of ecosystem water use efficiency (WUE), which reflects the coupling of the carbon–water cycle and function of terrestrial ecosystems. The changes of ecosystem SWUE at the regional scale and their relationships with the environmental and biotic factors are yet to be adequately understood. Here, we aim to estimate SWUE over northeast China using time-series Moderate Resolution Imaging Spectroradiometer (MODIS) gross primary productivity data and European Space Agency climate change initiative (ESA CCI) soil moisture product during 2007–2015. The spatio-temporal variations in SWUE and their linkages to multiple factors, especially the phenological metrics, were investigated using trend and correlation analysis. The results showed that the spatial heterogeneity of ecosystem SWUE in northeast China was obvious. SWUE distribution varied among vegetation types, soil types, and elevation. Forests might produce higher photosynthetic productivity by utilizing unit soil moisture. The seasonal variations of SWUE were consistent with the vegetation growth cycle. Changes in normalized difference vegetation index (NDVI), land surface temperature, and precipitation exerted positive effects on SWUE variations. The earlier start (SOS) and later end (EOS) of the growing season would contribute to the increase in SWUE. Our results help complement the knowledge of SWUE variations and their driving forces.
Highlights
Soil moisture (SM) is usually expressed as a percentage of soil water content in dry soil weight.As one of the main driving forces of the water, energy, and carbon cycles in land surface and atmosphere [1], soil moisture plays an important role in promoting photosynthesis and ecosystem dynamics [2]
The gross primary productivity (GPP) values of vegetation in Changbai Mountain and the Greater and Lesser Khingan Mountains were relatively high with the maximum value of 1343.26 gC/m2
Soil moisture-based water use efficiency may promote the understanding of soil water use in various ecosystems and ecological functions
Summary
Soil moisture (SM) is usually expressed as a percentage of soil water content in dry soil weight. As one of the main driving forces of the water, energy, and carbon cycles in land surface and atmosphere [1], soil moisture plays an important role in promoting photosynthesis and ecosystem dynamics [2]. To evapotranspiration (ET) of plants for the same period [3]. WUE is an indicator of the adjustment of vegetation photosynthesis to water loss [4], and quantitatively characterizing WUE can help us understand the interaction between the carbon and the water cycles of terrestrial ecosystems [5]. Soil moisture is affected by evapotranspiration, runoff, groundwater, etc. In arid grassland and shrubland, strong linear relationships were found between evapotranspiration and soil moisture [7]
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