Abstract
Although deforestation affects hydrological and climatic variables over tropical regions, its actual contributions to changes in evapotranspiration (ET) over subarctic China remain unknown. To establish a quantitative relationship between deforestation and terrestrial ET variations, we estimated ET using a semi-empirical Penman (SEMI-PM) algorithm driven by meteorological and satellite data at both local and regional scales. The results indicate that the estimated ET can be used to analyse the observed inter-annual variations. There is a statistically significant positive relationship between local-scale forest cover changes (∆F) and annual ET variations (∆ET) of the following form: ∆ET = 0.0377∆F – 2.11 (R2 = 0.43, p < 0.05). This relationship may be due to deforestation-induced increases in surface albedo and a reduction in the fractional vegetation cover (FVC). However, the El Niño/Southern Oscillation (ENSO), rather than deforestation, dominates the multi-decadal ET variability due to regional-scale wind speed changes, but the exact effects of deforestation and ENSO on ET are challenging to quantify.
Highlights
Evapotranspiration (ET) is the flux of water transferred from the land surface to the atmosphere and is an important bio-geophysical parameter for determining variations in the global energy, hydrological and carbon cycles [1,2,3,4,5,6,7]
The ground-based ET measurements from both the LSH and CBS flux tower sites are used to validate the estimated ET based on the semi-empirical Penman (SEMI-PM) algorithm driven by daily gridded meteorological datasets for subarctic China
The annual ET is higher during La Niña events and lower during El Niño conditions. These results suggest that regional oscillations captured by the MEI can affect the annual ET via climate variability, which indicates that climate variability is the main reason for the increase in ET, while deforestation plays a secondary role in regional-scale annual ET variations in subarctic China
Summary
Evapotranspiration (ET) is the flux of water transferred from the land surface to the atmosphere and is an important bio-geophysical parameter for determining variations in the global energy, hydrological and carbon cycles [1,2,3,4,5,6,7]. ET is primarily controlled by atmospheric evaporative demand, available energy, and vegetation and soil moisture supplies [8,9,10,11,12]. With the increase in global temperatures, atmospheric evaporative demand has been increasing in many regions of the world over the past several decades, which should result in increased ET [13,14]. The trend in ET may not be positive in some regions because land-use changes caused by anthropogenic activities are hypothesized to affect the available energy and moisture demands by altering biophysical processes that regulate. Previous work has shown that tropical deforestation in the Indochina Peninsula is a main cause of decreasing precipitation in September [22]
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