Evapotranspiration and Its Partitioning in Alpine Meadow of Three-River Source Region on the Qinghai-Tibetan Plateau

Lifeng Zhang,Yanhong Tang,Qi Li,Dongdong Chen,Song Gu,Xiang Zhang,Liang Zhao,Zhiguang Chen

doi:10.3390/w13152061

Abstract

The Qinghai-Tibetan Plateau (QTP) is generally considered to be the water source region for its surrounding lowlands. However, there have only been a few studies that have focused on quantifying alpine meadow evapotranspiration (ET) and its partitioning, which are important components of water balance. This paper used the Shuttleworth–Wallace (S–W) model to quantify soil evaporation (E) and plant transpiration (T) in a degraded alpine meadow (34°24′ N, 100°24′ E, 3963 m a.s.l) located at the QTP from September 2006 to December 2008. The results showed that the annual ET estimated by the S–W model (ETSW) was 511.5 mm (2007) and 499.8 mm (2008), while E estimated by the model (ESW) was 306.0 mm and 281.7 mm for 2007 and 2008, respectively, which was 49% and 29% higher than plant transpiration (TSW). Model analysis showed that ET, E, and T were mainly dominated by net radiation (Rn), while leaf area index (LAI) and soil water content at a 5 cm depth (SWC5cm) were the most important factors influencing ET partitioning. The study results suggest that meadow degradation may increase water loss through increasing E, and reduce the water conservation capability of the alpine meadow ecosystem.

Highlights

Hydrological processes of terrestrial ecosystems play an important role in interactions between the different spheres of the Earth, which mainly includes precipitation, evapotranspiration (ET), surface runoff, and drainage
The study was conducted in a degraded meadow (34◦24 N, 100◦24 E, 3963 m a.s.l) in Guoluo Prefecture in Qinghai Province, China, which is located at the Three-River Source Region (TRSR) of the Qinghai-Tibetan Plateau (QTP)
The leaf area index (LAI) in both years started to increase from May and reached its annual maximum in July, decreased rapidly because plants began to senesce in September (Figure 1)

Summary

Introduction

Hydrological processes of terrestrial ecosystems play an important role in interactions between the different spheres of the Earth (hydrosphere, biosphere, atmosphere, and geosphere), which mainly includes precipitation, evapotranspiration (ET), surface runoff, and drainage. ET plays a major role in regional and global climate change [3] because it links closely to the latent heat energy, carbon, and water cycles in terrestrial ecosystems. ET is the combination of transpiration from vegetation (T) and evaporation from the soil surface (E), where ET partitioning is a subject of ongoing research due to the complexity of surface energy balance processes and measurements [5,6,7], and is very important in predicting the responses of ecosystem water balance to climate and vegetation coverage changes [8]. The S–W model has been widely applied to study terrestrial ecosystem ET, E, and T [14,15,16] because of its simple and accurate consideration of hydrological processes [17]

Objectives

Methods

Results

Discussion

Conclusion