Ecophysiological modeling of photosynthesis and carbon allocation to the tree stem in the boreal forest

Abstract

Abstract. A better understanding of the coupling between photosynthesis and carbon allocation in the boreal forest, together with its associated environmental factors and mechanistic rules, is crucial to accurately predict boreal forest carbon stocks and fluxes, which are significant components of the global carbon budget. Here, we adapted the MAIDEN ecophysiological forest model to consider important processes for boreal tree species, such as nonlinear acclimation of photosynthesis to temperature changes, canopy development as a function of previous-year climate variables influencing bud formation and the temperature dependence of carbon partition in summer. We tested these modifications in the eastern Canadian taiga using black spruce (Picea mariana (Mill.) B.S.P.) gross primary production and ring width data. MAIDEN explains 90 % of the observed daily gross primary production variability, 73 % of the annual ring width variability and 20-30 % of its high-frequency component (i.e., when decadal trends are removed). The positive effect on stem growth due to climate warming over the last several decades is well captured by the model. In addition, we illustrate how we improve the model with each introduced model adaptation and compare the model results with those of linear response functions. Our results demonstrate that MAIDEN simulates robust relationships with the most important climate variables (those detected by classical response-function analysis) and is a powerful tool for understanding how environmental factors interact with black spruce ecophysiology to influence present-day and future boreal forest carbon fluxes.

Modelling tree ring cellulose <i>δ</i><sup>18</sup>O variations in two temperature-sensitive tree species from North and South America

“…In contrast, because precipitation is more abundant in summer (June to September) in northeastern Canada (Naulier et al, 2014), high summer temperatures should be always beneficial to tree growth if enough soil water is available. Therefore, in agreement with GPP-derived eddy covariance data from the Fluxnet network (see Gennaretti et al, 2017a), a better fit between observations and simulations is observed when using a unimodal rather than a bimodal GPP distribution. Monitoring of tree physiology, environmental conditions and wood cell formation will provide a more detailed representation of the complex biological and ecological processes operating in Patagonia, allowing us to run the MAIDENiso model with better constraints.…”

“…It explicitly allocates carbohydrates to different carbon pools (leaves, stem, storage and roots) on a daily basis using phenological stage-dependent rules (see Gennaretti et al, 2017a, for details on the construction of the main MAIDEN model).…”

“…For the northeastern Canadian sites, the GPP simulated by MAIDENiso was optimized using observations from an eddy covariance station (see Gennaretti et al, 2017a). Unfortunately, such observations were not available for N. pumilio, and therefore the parameterization obtained for the GPP of P. mariana was also used for the western Argentinian sites but constraining the simulations with phenological observations extracted from the literature.…”

“…A set of 50 plausible blocks of parameters (posterior values) was selected according to the method described in Gennaretti et al (2017a) using Markov chain Monte Carlo (MCMC) sampling (Table 1). The following prior plausible ranges were considered: Table 1).…”

Spatially Explicit Modeling of Coupled Water and Carbon Processes Using a Distributed Ecohydrological Model in the Upper Heihe Watershed, China

“…Currently, there are many ecophysiological modeling researches published at multiple spatio-temporal resolutions and spans, including point scales [8,9], mesoscales [10,11] and global scales [12] at yearly [13] or minute time-steps [1], while few of them completely considered the soil water processes and the non-linear relationship between it and vegetation ecophysiological processes. Due to the limited understanding of water-carbon interactions, many researches (regardless of modeling or measurement) often regard them as an isolated process [2].…”