Shifting Contribution of Climatic Constraints on Evapotranspiration in the Boreal Forest

Abstract

The global evapotranspiration (ET) shows an increasing trend with global warming in recent decades, while ET variation in different regions is still uncertain. Boreal forest ecosystem, as one of the most sensitive regions to climate change, are still poorly understood due to the sparse observation and the changing of ET in the boreal forest has been covered up for lower values compared to lower-latitude regions. Based on the PT-JPL model, we estimated the ET in the boreal forest during 1982-2015. The annual ET showed an increasing trend (0.5073 mm year -1 ). 76% of the boreal forest area is increasing which mainly occurred in Central Canada, Alaska, Central Siberia and Northern Europe, while 24% is decreasing, which occurred in the southern Siberia, Northern Mongolia and Northern Canada. The quantification of basic climatic factors shows that atmospheric demand is the main factor with an increasing trend which is accordance with the increasing temperature; ii) annual precipitation is increasing providing increasing water supply for boreal forest. Factorial experiments were also conducted and showed that the climatic constraints that contribute mainly to ET have gradually shifted from net radiation to moisture restriction in the boreal forest. The moisture control tendency indicated that ET in the boreal forest was gradually controlled by humidity rather than energy, suggesting a limited water supply and an intensifying water cycle in the boreal forest. Plain Language SummaryEvapotranspiration (ET) is the process which water returns to the atmosphere from the surface through evaporation and plant transpiration. The ET process absorbs energy and requires continuous water and energy supply and is affected by climate change and in turn generates feedback to the climate. The study of ET changes is of great significance to understand the future climate change and the dryness tendency. The global ET is found to be increasing in recent decades, but the variation in spatial is still poor understood. Thus, this study examinates the ET trend in boreal forests, one of the most sensitive regions to climate change. The results shows that the ET in boreal forest is increasing during 1982-2015, which is caused by the increasing atmospheric demand and precipitation according to the basic climatic control quantification.Experiments on environmental control factors show that the moisture has become the controlling factor that control ET. This may be related to the increased demand for atmospheric water caused by climate warming. Although regional precipitation also shows an increasing trend, this trend is Accepted ArticleThis article is protected by copyright. All rights reserved. lower than the increase of ET, indicating that climate change may cause water constraint on ET in the future, which will lead to regional drought.

Effect of Permafrost Thawing on Discharge of the Kolyma River, Northeastern Siberia

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Balancing Water Yield and Water Use Efficiency Between Planted and Natural Forests: A Global Analysis

“…Warming temperature could lead to an increase in evapotranspiration in forests, thus reducing the water yield (Wang et al. 2021). The negative trends of water yield coefficient with DBH and density shown in this study were consistent with previous studies, which showed an increase in water yield after harvest and thinning (Harr 1983) or a decrease in water yield after reforestation (Webb and Kathuria 2012).…”

Large Divergence of Projected High Latitude Vegetation Composition and Productivity Due To Functional Trait Uncertainty

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