Woody biomass production lags stem-girth increase by over one month in coniferous forests

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

“…8a-b). These results are in line with those of Cuny et al (2015), who showed that woody biomass production is low in the first part of the growing season for most coniferous tree species because production follows the seasonal course of temperature (highest peak in summer). The simulated accumulation of carbon to the stem ended each year when the photoperiod became shorter than approximately 13.41 h ( Fig.…”

“…This approach was necessary because data from field plots were not available from all study sites. A recent study showed that the maximum rate of ring width increase during the growing season precedes the maximum rate of increase in wood biomass and that these processes could exhibit differential sensitivities to local environmental conditions (Cuny et al, 2015). However, Cuny et al (2015) also highlighted that wood biomass production follows the seasonal course of temperature in coniferous forests, and this is what we observed once MAIDEN was optimized.…”

“…2b-c), which suggests that the relationship between GPP and wood production is complex and nonlinear (Rocha et al, 2006). Significant simulation improvements were obtained, introducing important processes for temperature-sensitive boreal forests into the model, such as (i) the acclimation of photosynthesis to temperature over several days (see Gea-Izquierdo et al, 2010;Mäkelä et al, 2004), (ii) the influence of previous-year climatic conditions affecting bud formation on the potential amount of carbon allocated to the canopy each year (see Salminen and Jalkanen, 2005) and (iii) the positive relationship between temperature and the carbon allocated to the stem in summer (see Cuny et al, 2015). Although we used black spruce data from the northern Quebec taiga to test and optimize the model, the new model modifications have the potential to work within other boreal regions and tree species.…”

“…The rest of CT i is allocated to the canopy or the roots, with a prescribed 1.65 root-to-canopy mass ratio for black spruce (Czapowskyj et al, 1985;Jenkins et al, 2003). During the "growth and accumulation phase in summer" (phase 4), CT i comes from only photosynthesis and is allocated either to stem growth or to storage as a function of climate forcing.…”

“…However, despite recent progress, few models have been able to simultaneously simulate the meteorological control on daily photosynthetic production and the meteorological and phenological controls on daily carbon allocation for temperature-limited boreal forest ecosystems. Such models should be able to simulate the following observed phenomena: (i) the delayed response of photosynthesis to temperature (Gea-Izquierdo et al, 2010;Mäkelä et al, 2004), (ii) the influence of preceding season conditions on current-year canopy development (Salminen and Jalkanen, 2005) and (iii) a strong positive relationship between wood biomass production and temperature (Cuny et al, 2015).…”