Inferring the effects of sink strength on plant carbon balance processes from experimental measurements

Abstract

Abstract. The lack of correlation between photosynthesis and plant growth under sink-limited conditions is a long-standing puzzle in plant ecophysiology that currently severely compromises our models of vegetation responses to global change. To address this puzzle, we applied data assimilation to an experiment in which the sink strength of Eucalyptus tereticornis seedlings was manipulated by restricting root volume. Our goals were to infer which processes were affected by sink limitation and to attribute the overall reduction in growth observed in the experiment to the effects on various carbon (C) component processes. Our analysis was able to infer that, in addition to a reduction in photosynthetic rates, sink limitation reduced the rate of utilization of nonstructural carbohydrate (NSC), enhanced respiratory losses, modified C allocation and increased foliage turnover. Each of these effects was found to have a significant impact on final plant biomass accumulation. We also found that inclusion of an NSC storage pool was necessary to capture seedling growth over time, particularly for sink-limited seedlings. Our approach of applying data assimilation to infer C balance processes in a manipulative experiment enabled us to extract new information on the timing, magnitude and direction of the internal C fluxes from an existing dataset. We suggest that this approach could, if used more widely, be an invaluable tool to develop appropriate representations of sink-limited growth in terrestrial biosphere models.

The impact of a simple representation of non-structural carbohydrates on the simulated response of tropical forests to drought

“…However, the nature of this "tipping point" is uncertain, and without accurate representation of forest resilience, including the balance between hydraulic failure and carbon starvation, predictions of large-scale forest die-back will remain unreliable. Drought is predicted to increase in both frequency and severity across the tropical rainforest biome in response to climate change (Marengo et al, 2018;IPCC, 2014). Accurately simulating drought responses is therefore a priority for the global modelling community (Corlett, 2016;Fatichi et al, 2016), although many efforts to date have focused on simulating plant hydraulic properties and have largely ignored the development of a NSC pool in models.…”

Leaf Traits and Resource Use Efficiencies of 19 Woody Plant Species in a Plantation in Fangshan, Beijing, China

“…The maximum net photosynthetic rate of plants determines their potential photosynthetic capacity. The higher the P nmax value, the higher the carbon sequestration rate, which is beneficial for the accumulation of organic matter [45,46]. In this study, the highest P nmax was of Amorpha fruticosa (28.92 µmol•m 2 •s −1 ), whereas the lowest was of Yulania denudata (6.72 µmol•m 2 •s −1 ).…”