Seasonal and interannual variations in ecosystem respiration in relation to temperature, moisture, and productivity in a temperate semi-arid shrubland

Xin Jia; Yu Mu; Tianshan Zha; Ben Wang; Shugao Qin; Yun Tian

doi:10.1016/j.scitotenv.2019.136210

Seasonal and interannual variations in ecosystem respiration in relation to temperature, moisture, and productivity in a temperate semi-arid shrubland

Sci Total Environ. 2020 Mar 20:709:136210. doi: 10.1016/j.scitotenv.2019.136210. Epub 2019 Dec 20.

Authors

Xin Jia¹, Yu Mu¹, Tianshan Zha², Ben Wang³, Shugao Qin¹, Yun Tian⁴

Affiliations

¹ Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China; Research Center for Forestry Ecological Engineering, Ministry of Education, Beijing Forestry University, Beijing 100083, China.
² Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China; Research Center for Forestry Ecological Engineering, Ministry of Education, Beijing Forestry University, Beijing 100083, China. Electronic address: tianshanzha@bjfu.edu.cn.
³ College of Horticulture and Forestry Sciences/Hubei Engineering Technology Research Center for Forestry Information, Huazhong Agricultural University, Wuhan 430070, China.
⁴ Research Center for Forestry Ecological Engineering, Ministry of Education, Beijing Forestry University, Beijing 100083, China.

PMID: 31905552
DOI: 10.1016/j.scitotenv.2019.136210

Abstract

Understanding the temporal dynamics and influencing factors of ecosystem respiration (Reco) in semi-arid shrublands is critical for predicting how their carbon balance may respond to climate change. Using the eddy-covariance technique, we quantified the net ecosystem CO₂ exchange (NEE) in a semi-arid shrubland of northern China from July 2011 to December 2016, and partitioned NEE into Reco and gross primary productivity (GPP). Annual Reco varied from 300 g C m^-² yr^-¹ in 2014 to 426 g C m^-² yr^-¹ in 2012, and GPP ranged from 277 g C m^-² yr^-¹ in 2014 to 503 g C m^-² yr^-¹ in 2012. The relationship between half-hourly nighttime Reco and air temperature (T_a) was well-described by the Lloyd & Taylor model. Indicators of the seasonal temperature sensitivity (E₀ and Q₁₀) of Reco increased with both the annual integral and seasonal amplitude of GPP. However, when averaged into 1 °C T_a bins, nighttime Reco increased with T_a up to an optimal temperature of ~20 °C, above which it decreased with increasing T_a. Periods of low soil moisture in spring and summer markedly depressed Reco, contributing to its seasonal and interannual variations. In addition, low soil moisture had little effect on nighttime Reco when T_a was below 15 °C, but substantially reduced nighttime Reco when T_a was above 15 °C. Ecosystem respiration increased linearly with GPP at both seasonal and interannual scales, with the slope being 0.50 and 0.55, respectively. Our results have important implications for predicting Reco under climate change, considering continuous warming and increases in the frequency and intensity of extreme events (e.g., heat waves, droughts). Moreover, our results suggest that process-based carbon models should adequately represent the effects of substrate supply (e.g., by GPP) on Reco and its temperature sensitivity.

Keywords: CO(2) flux; Carbon balance; Dryland; Gross ecosystem productivity; Soil water content; Temperature sensitivity.