Modelling carbon sources and sinks in terrestrial vegetation

Abstract

Contents Summary652I.Introduction652II.Discrepancy in predicting the effects of rising [CO2] on the terrestrial C sink655III.Carbon and nutrient storage in plants and its modelling656IV.Modelling the source and the sink: a plant perspective657V.Plant‐scale water and Carbon flux models660VI.Challenges for the future662Acknowledgements663Authors contributions663References663 Summary The increase in atmospheric CO2 in the future is one of the most certain projections in environmental sciences. Understanding whether vegetation carbon assimilation, growth, and changes in vegetation carbon stocks are affected by higher atmospheric CO2 and translating this understanding in mechanistic vegetation models is of utmost importance. This is highlighted by inconsistencies between global‐scale studies that attribute terrestrial carbon sinks to CO2 stimulation of gross and net primary production on the one hand, and forest inventories, tree‐scale studies, and plant physiological evidence showing a much less pronounced CO2 fertilization effect on the other hand. Here, we review how plant carbon sources and sinks are currently described in terrestrial biosphere models. We highlight an uneven representation of complexity between the modelling of photosynthesis and other processes, such as plant respiration, direct carbon sinks, and carbon allocation, largely driven by available observations. Despite a general lack of data on carbon sink dynamics to drive model improvements, ways forward toward a mechanistic representation of plant carbon sinks are discussed, leveraging on results obtained from plant‐scale models and on observations geared toward model developments.

Genotypic variation in source and sink traits affects the response of photosynthesis and growth to elevated atmospheric CO2

“…Feedback effects of sink limitation on photosynthesis may in part explain why inconsistencies are sometimes observed when simulating photosynthetic capacity (Fatichi, Pappas, Zscheischler, & Leuzinger, ; Lombardozzi et al, , ). In general, even crop models simulating photosynthesis mechanistically, for example, GECROS (Yin & van Laar, ; Yin & Struik, ) do not account for biochemical feedback inhibitions of photosynthesis, such as via TPU (Busch et al, ; Sharkey, ).…”

It is not just a ‘trade‐off’: indications for sink‐ and source‐limitation to vegetative and regenerative growth in an old‐growth beech forest

“…In this context, Sala et al (2011) and Piper & Fajardo (2011) questioned the hypothesis that the often observed size-or age-related decline of tree and stand growth is due to an increasing shortage of carbon. Accordingly, Fatichi et al (2018) suggested a better representation of sink-driven control mechanisms for plant growth in terrestrial biosphere models. Case studies on annual stem growth, weather conditions and net ecosystem carbon fluxes have provided strong evidence that stem growth is limited more directly by water deficits and temperature than by carbon assimilation (Mund et al, 2010;Delpierre et al, 2015;Lempereur et al, 2015).…”

Xylem–phloem hydraulic coupling explains multiple osmoregulatory responses to salt stress

“…The combined effects of salinization and projected CO 2 enrichment could furthermore affect plant water and carbon use strategies for now and the foreseeable future (Langley & Megonigal, 2010;Fatichi et al, 2016Fatichi et al, , 2019Wendelberger & Richards, 2017;Perri et al, 2018b). A prominent example comes from coastal ecosystems such as mangroves and tidal wetlands, where sea-level rise and saltwater intrusion already exert significant controls on species shifts and carbon balance at the ecosystem level (Alongi, 1998;Kirwan et al, 2010;Herbert et al, 2015;Wendelberger & Richards, 2017).…”