Conifers in cold environments synchronize maximum growth rate of tree‐ring formation with day length

Abstract

Summary• Intra-annual radial growth rates and durations in trees are reported to differ greatly in relation to species, site and environmental conditions. However, very similar dynamics of cambial activity and wood formation are observed in temperate and boreal zones.• Here, we compared weekly xylem cell production and variation in stem circumference in the main northern hemisphere conifer species (genera Picea , Pinus , Abies and Larix ) from 1996 to 2003. Dynamics of radial growth were modeled with a Gompertz function, defining the upper asymptote ( A ), x -axis placement ( β ) and rate of change ( κ ).• A strong linear relationship was found between the constants β and κ for both types of analysis. The slope of the linear regression, which corresponds to the time at which maximum growth rate occurred, appeared to converge towards the summer solstice.• The maximum growth rate occurred around the time of maximum day length, and not during the warmest period of the year as previously suggested. The achievements of photoperiod could act as a growth constraint or a limit after which the rate of tree-ring formation tends to decrease, thus allowing plants to safely complete secondary cell wall lignification before winter.

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

“…Soil drought, for instance, has been suggested to hasten the cessation of cambial activity (Dünisch and Bauch 1994;Gričar and Čufar 2008), though this result is not systematically observed (Gruber et al 2010). Day length, which likely modulates the rate of cambial division (Rossi et al 2006;Cuny et al 2012), may also act as a cue for the cessation of cambial activity, but this hypothesis remains to be tested. Finally, the ending of xylem differentiation, which marks the end of annual wood formation, occurs at similar temperatures to the prevailing temperatures during the onset of cambium cell division .…”

Comparing needle and shoot phenology with xylem development on three conifer species in Italy

“…Cambium is a sink of carbohydrates and cambial activity requires a continuous supply of energy, extracted from the storage tissues or produced by photosynthesis (Oribe et al, 2003). The conclusion of shoot and needle lengthening occurred in July, when cambium activity slowed down (Rossi et al, 2006c). Newly produced carbon obtained from photosynthesis could be available for the deposition of cellulose microfibrils and lignin in order to provide the developing latewood cells with thick secondary walls.…”

Relations entre climat et caractéristiques cellulaires dans la tige et les racines de l’épinette noire et du sapin baumier

“…Despite the significant differences between species and tree parts, only temperature appeared to be an important factor affecting cell features in earlywood. Cambium activity culminates during June and July (Rossi et al, 2006c), but temperatures can still be cold, even below 0 • C (data not shown). Low temperatures are known to affect cell division, but this study demonstrated their important influence on the processes of cell maturation, so affecting the size of cells and walls.…”