This study quantifies
actual evapotranspiration (ETa) for a period from June to September
2016 measured by two weighable gravitation lysimeters in a semi-arid grassland
in southwest Siberia. As part of a crop rotation system, the first lysimeter
was fallow but covered with ruderal vegetation. The second lysimeter is
permanently characterized by pristine steppe vegetation. In addition to ETa
measurements, the reference evapotranspiration (ET0) is computed by
a Penman-Monteith model. The estimates are related to the ETa records
and the model is evaluated with regard to its performance in a semi-arid
environment. The results indicated an ETa driven by energy but
limited by water. Within 115 days the total amounts of ETa ranged
from 205 mm to 374.1 mm, and daily values varied from 0.1 to 6.9 mm day-1.
The large differences are caused by the different vegetation cover of the
lysimeters. Due to the high and dense canopy of the pristine steppe vegetation,
the transpiration term was considerably
higher compared to the ruderal vegetation where soil evaporation took the major
part. The daily ETa records differed on average by -91.1% to the ET0
estimates. The statistical analyses yielded a low correlation between ETa
of the ruderal vegetation and ET0 but an acceptable model
performance for the pristine steppe. However, it was observed that ETa
occasionally exceeds ET0, particularly after precipitation. Due to
the high water availability and the subsequent rise of ETa, ET0
was underestimated, whereas it was overestimated during dry periods. Finally,
the quality of the Penman-Monteith model varied substantially with the water
supply at the study site.
Actual evapotranspiration Penman-Monteith FAO-56 semi-arid Siberia weighable gravitation lysimeter
Primary Language | English |
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Journal Section | Articles |
Authors | |
Publication Date | July 1, 2019 |
Published in Issue | Year 2019 Volume: 8 Issue: 3 |