Optimal soil water content and temperature sensitivity differ among heterotrophic and autotrophic respiration from oasis agroecosystems
2022
Zhang, Yang | Zhu, Gaofeng | Yin, Li | Ma, Lei | Xu, Cong | Chen, Huiling | Ma, Ding | Su, Yonghong | Zhu, Yongtai | He, Liyang | Han, Le
Soil respiration (Rₛ), which consists of heterotrophic respiration (Rₕ) by soil decomposers and autotrophic respiration (Rₐ) by roots, plays a critical role in the climate–carbon cycle feedback. However, the magnitudes, patterns and drivers of Rₛ and its components remain unclear in agroecosystems in arid regions. In this study, we conducted a two-year program of continuous measurement of Rₛ, Rₕ, Rₐ, soil water content (SWC₅), and soil temperature (Tₛ₅) at a 5-cm depth in an irrigated vineyard in Northwest China. The results showed that the mean annual Rₛ was 688.03 ± 8.59 g C m⁻² yr⁻¹ (mean ± standard deviation), of which 67.9 ± 0.5 % was dependent on Rₕ and 32.1 ± 0.5 % was dependent on Rₐ. In addition, the contribution of Rₛ during the non-growing season (NGS) to the annual values was 19.9 ± 2.3 %. We found that Rₕ and Rₐ responded asynchronously to SWC₅ and Tₛ₅. During the growing season (GS), the optimal SWC₅ (20.0 %) and temperature sensitivity (Q₁₀ = 1.93 ± 1.38) for Rₐ were higher than that for Rₕ (19.0 % and 0.97 ± 0.76). They were affected by the plant growth stages to a certain extent. During the NGS, the Q₁₀ for Rₕ (1.52 ± 0.95) was higher than that for Rₐ (1.51 ± 1.27). These results underscore the importance of including the NGS emissions for reliably quantifying annual Rₛ and its components from arid agroecosystems. Meanwhile, Rₕ and Rₐ should be considered separately in Earth system models. The different optimal soil water content and temperature sensitivity for Rₕ and Rₐ should be used when predicting the effects of climate change.
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