Xylem formation can be modeled statistically as a function of primary growth and cambium activity

Abstract

SummaryPrimary (budburst, foliage and shoot) growth and secondary (cambium and xylem) growth of plants play a vital role in sequestering atmospheric carbon. However, their potential relationships have never been mathematically quantified and the underlying physiological mechanisms are unclear. We monitored primary and secondary growth in Picea mariana and Abies balsamea on a weekly basis from 2010 to 2013 at four sites over an altitudinal gradient (25-900 m) in the eastern Canadian boreal forest.We determined the timings of onset and termination through the fitted functions and their first derivative. We quantified the potential relationships between primary growth and secondary growth using the mixed-effects model.We found that xylem formation of boreal conifers can be modeled as a function of cambium activity, bud phenology, and shoot and needle growth, as well as species-and site-specific factors.Our model reveals that there may be an optimal mechanism to simultaneously allocate the photosynthetic products and stored nonstructural carbon to growth of different organs at different times in the growing season. This mathematical link can bridge phenological modeling, forest ecosystem productivity and carbon cycle modeling, which will certainly contribute to an improved prediction of ecosystem productivity and carbon equilibrium.

New perspective on spring vegetation phenology and global climate change based on Tibetan Plateau tree-ring data

“…Similar synchronism between primary and secondary meristems was identified by direct observations across spruce ecotypes growing in an ordinary garden (29), and this was confirmed on a wider geographical scale by comparing remote sensing chronologies with intraannual data of xylem formation (30). The physiological explanation of the phenological synchronicity between primary and secondary growth remains an issue that is only partially resolved (28).…”

“…The significant correlation found between remote sensing-derived SOS and our modeling results highlighted that their connection is not casual but robust, although grasses and herbs have more-shallow root systems than trees and therefore might respond differently (27). A 4-y experiment monitoring the growth of spruce and fir on a weekly basis detected synchronism of primary growth (bud and leaf) and secondary (cambium) growth after budburst over the growing season in boreal conifers in eastern Canada (28). Similar synchronism between primary and secondary meristems was identified by direct observations across spruce ecotypes growing in an ordinary garden (29), and this was confirmed on a wider geographical scale by comparing remote sensing chronologies with intraannual data of xylem formation (30).…”

Temperate and boreal forest tree phenology: from organ-scale processes to terrestrial ecosystem models

“…In certain ring-porous species (deciduous oaks), the onset of cambial division is the first step of spring resumption (Gričar 2010;González-González et al 2013), whereas in others (e.g., Fraxinus excelsior), overwintering vessels start to enlarge before budburst (SassKlaassen et al 2011) and cambial division is resumed after budburst (Frankenstein et al 2005). In conifers, the resumption of cambium activity generally occurs before budburst (Rossi et al 2009;Gruber et al 2010;Cuny et al 2012;Michelot et al 2012;Huang et al 2014).…”

Modelling intra- and inter-annual growth dynamics of Scots pine in the whole-tree carbon balance framework

“…There may, however, not be such a direct relationship between the onset of shoot growth and growth of other organs (Steinaker et al 2010, Delpierre et al 2016a. Huang et al (2014) were able to model secondary growth onset with observations of cambium activity, bud/shoot phenology and needle growth, which is a step forward in combining the growth of different organs. However, this also reinforces the statement about the complexity of the whole tree modelling.…”

“…Under current conditions growth of most of the tree organs does not occur throughout the entire growing season (e.g. Hari et al 1970, Huang et al 2014. The mechanisms by which the lengthened period of favourable environmental conditions can or cannot be utilized is therefore of great significance to the carbon balance of the boreal forests.…”