Coupling between the terrestrial carbon and water cycles—a review

TLDR

The terrestrial carbon and water cycles are strongly coupled, and rising atmospheric CO₂ modifies climate, hydrology, stomatal regulation, biomass, photosynthesis, and transpiration, thereby altering soil moisture and plant CO₂ uptake. This paper reviews the main mechanisms behind the coupling of the terrestrial water and carbon cycles, focusing on the role of dryness and the impact of rising CO₂. The review examines how atmospheric dryness and terrestrial water availability influence carbon uptake and how rising CO₂ alters the water cycle. These coupled changes have profound implications for predictions of the carbon and water cycles.

Abstract

Abstract The terrestrial carbon and water cycles are strongly coupled. As atmospheric carbon dioxide concentration increases, climate and the coupled hydrologic cycle are modified, thus altering the terrestrial water cycle and the availability of soil moisture necessary for plants’ carbon dioxide uptake. Concomitantly, rising surface carbon dioxide concentrations also modify stomatal (small pores at the leaf surface) regulation as well as biomass, thus altering ecosystem photosynthesis and transpiration rates. Those coupled changes have profound implications for the predictions of the carbon and water cycles. This paper reviews the main mechanisms behind the coupling of the terrestrial water and carbon cycles. We especially focus on the key role of dryness (atmospheric dryness and terrestrial water availability) on carbon uptake, as well as the predicted impact of rising carbon dioxide on the water cycle. Challenges related to this coupling and the necessity to constrain it based on observations are finally discussed.