TY - JOUR
T1 - Annual variations of T/ET in a semi-arid region
T2 - Implications of plant water use strategies
AU - Yuan, Ruiqiang
AU - Chang, Liling
AU - Niu, Guoyue
N1 - Funding Information:
This research project was funded by the NASA MAP Program (80NSSC17K0352), NOAA OAR’s OWAQ (NA18OAR4590397), and the China scholarship council (201708140009). We thank the anonymous reviewers for their valuable comments on our draft paper. We thank Dr. Russell L. Scott for his support with flux tower data processing. We thank Dr. Sha Zhou for her support with the quantile regression in R.
Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2021/12
Y1 - 2021/12
N2 - Understanding the annual variation in the transpiration to evapotranspiration ratio (T/ET) remains a challenge and is essential for a thorough understanding of plant responses to the changing environment. We obtained the annual dynamics of T/ET in a semi-arid area of the southwestern United States based on the medians of monthly T/ET derived from two ET partitioning methods. The variation in monthly T/ET was analysed, and plant water use strategies were discussed based on the water use efficiency evaluated by the transpiration (WUE_T). The results show that physiological changes in plants are vital in the annual dynamics of T/ET. Switches in plant physiological status (growth and dormancy) at the start and end of growing seasons induce two dramatic changes in T/ET. Consequently, there is an annual bimodal dynamic of monthly T/ET, with a maximum of 0.84 in October and a minimum of 0.14 in December. Physiological/biochemical variations of plants indicated by solar-induced chlorophyll fluorescence (SIF) are linearly related to T/ET in growing seasons at a monthly scale (T/ET = 3.40 × SIF + 0.36, R2 = 0.987). Generally, a stable high monthly T/ET occurs under sufficient energy and water conditions and a highly variable monthly T/ET occurs under energy and water deficient conditions. In semi-arid regions, plants can flexibly adjust WUE_T following different water use strategies to survive or gain as much gross primary productivity (GPP) to compete. Saving water by greatly elevating WUE_T is the main strategy by which plants survive the non-growing season when WUE_T is linearly related to SIF (WUE_T = -114.93 × SIF + 3.25, R2 = 0.970). However, GPP and not WUE_T, becomes the goal of plants in growing seasons when they employ a stable and moderate WUE_T (around 2.1 gC kg−1 H2O) despite the abundant energy and precipitation. There are obvious reductions in WUE_T during the transition periods of the plants’ ‘growth-dormancy’ cycle. Our study highlights the importance of studying annual T/ET variations and water-use efficiency dynamics to better understand water use strategies in plants.
AB - Understanding the annual variation in the transpiration to evapotranspiration ratio (T/ET) remains a challenge and is essential for a thorough understanding of plant responses to the changing environment. We obtained the annual dynamics of T/ET in a semi-arid area of the southwestern United States based on the medians of monthly T/ET derived from two ET partitioning methods. The variation in monthly T/ET was analysed, and plant water use strategies were discussed based on the water use efficiency evaluated by the transpiration (WUE_T). The results show that physiological changes in plants are vital in the annual dynamics of T/ET. Switches in plant physiological status (growth and dormancy) at the start and end of growing seasons induce two dramatic changes in T/ET. Consequently, there is an annual bimodal dynamic of monthly T/ET, with a maximum of 0.84 in October and a minimum of 0.14 in December. Physiological/biochemical variations of plants indicated by solar-induced chlorophyll fluorescence (SIF) are linearly related to T/ET in growing seasons at a monthly scale (T/ET = 3.40 × SIF + 0.36, R2 = 0.987). Generally, a stable high monthly T/ET occurs under sufficient energy and water conditions and a highly variable monthly T/ET occurs under energy and water deficient conditions. In semi-arid regions, plants can flexibly adjust WUE_T following different water use strategies to survive or gain as much gross primary productivity (GPP) to compete. Saving water by greatly elevating WUE_T is the main strategy by which plants survive the non-growing season when WUE_T is linearly related to SIF (WUE_T = -114.93 × SIF + 3.25, R2 = 0.970). However, GPP and not WUE_T, becomes the goal of plants in growing seasons when they employ a stable and moderate WUE_T (around 2.1 gC kg−1 H2O) despite the abundant energy and precipitation. There are obvious reductions in WUE_T during the transition periods of the plants’ ‘growth-dormancy’ cycle. Our study highlights the importance of studying annual T/ET variations and water-use efficiency dynamics to better understand water use strategies in plants.
KW - Adaption
KW - Changing environment
KW - Leaf scale WUE
KW - Plant
KW - Transpiration
KW - Water use strategies
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U2 - 10.1016/j.jhydrol.2021.126884
DO - 10.1016/j.jhydrol.2021.126884
M3 - Article
AN - SCOPUS:85118758100
SN - 0022-1694
VL - 603
JO - Journal of Hydrology
JF - Journal of Hydrology
M1 - 126884
ER -