Dynamics of carbon and water vapor fluxes in three typical ecosystems of Heihe River Basin, Northwestern China

Zhiyong Ding; Yuyang Wang; Jinzhi Ding; Zhiguo Ren; Jie Liao

doi:10.1016/j.scitotenv.2024.172611

Dynamics of carbon and water vapor fluxes in three typical ecosystems of Heihe River Basin, Northwestern China

Sci Total Environ. 2024 Jun 15:929:172611. doi: 10.1016/j.scitotenv.2024.172611. Epub 2024 Apr 19.

Authors

Zhiyong Ding¹, Yuyang Wang², Jinzhi Ding³, Zhiguo Ren⁴, Jie Liao⁵

Affiliations

¹ State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059, China.
² College of Grassland Science and Technology, China Agricultural University, Beijing 100193, China; Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China. Electronic address: yuyangwang@pku.edu.cn.
³ State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China. Electronic address: jzding@itpcas.ac.cn.
⁴ Heihe Remote Sensing Experimental Research Station, Key Laboratory of Remote Sensing of Gansu Province, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Science, Lanzhou 730000, China.
⁵ Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands, Northwest Institute of Eco-environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.

PMID: 38642764
DOI: 10.1016/j.scitotenv.2024.172611

Abstract

Understanding the dynamics of carbon and water vapor fluxes in arid inland river basin ecosystems is essential for predicting and assessing the regional carbon-water budget amid climate change. However, studies aiming to unravel the mechanisms driving the variations and coupling process of regional carbon-water budget in a changing environment in arid regions are limited. Here, we used the eddy covariance technique to analyze the relationship between CO₂ and H₂O fluxes in three typical ecosystems across the upper, middle, and lower reaches of an arid inland river basin in Northwestern China. Our results showed that all ecosystems acted as carbon sinks, with the alpine swamp meadow, cropland, and desert shrubland sequestrating -300.2 ± 0.01, -644.8 ± 2.9, and - 203.7 ± 22.5 g C m^-2 yr^-1, respectively. Air temperature (T_a) primarily controlled daily gross primary productivity (GPP) and net ecosystem CO₂ exchange (NEE) in the irrigated cropland during the growing season, while soil temperature (T_s) and vapor pressure deficit (VPD) regulated these parameters in the alpine swamp meadow and desert shrubland. Additionally, T_a and net radiation (R_n) controlled daily evapotranspiration (ET) in cropland, while T_s and R_n regulated ET at other sites. Consequently, carbon and water vapor fluxes of all three ecosystems tended to be energy-limited during the growing season. The differential responses of carbon and water vapor fluxes in the upper, middle, and lower reaches of these ecosystems to biophysical factors determined their distinct coupling and variations in water use efficiency. Notably, the desert shrub ecosystem in the lower reach of the basin maintained a stable balance between carbon gain and water loss, indicating adaptation to aridity. This study provides valuable insights into the underlying mechanisms behind the changes in carbon and water vapor fluxes and water-use efficiency in arid river basin ecosystems.

Keywords: Arid region; Coupling; Evapotranspiration (ET); Net ecosystem CO(2) exchange (NEE); Water use efficiency.