Is the first flowering event and corresponding maturity phase in trees related to radial wood density changes?

Abstract

Key message: Although first flowering in trees causes clear changes in main stem morphological trends, we prove that it does not totally explain changes in wood density trends. Abstract: The phase change produced by a tree’s first flowering event (that marks the limit between juvenile and mature stage) causes changes in the morphological trends of the main stem. As has been documented in a number of tree species, the number of growth units per annual shoot, the annual shoot length, and the growth unit length are some of the variables that exhibit abrupt changes when first flowering occurs. Considering the strong impact of first flowering on tree morphology—and considering also trends that have been observed in wood density and related variables, we tested the relationship between the first flowering event and wood density trend changes in Pinus radiata D. Don at three different site conditions with differing climates. The relationship was studied using different criteria to select the proper variables and methodology. Some interesting relationships between first flowering and certain variables were found, particularly the variables earlywood density, latewood density accumulated, latewood proportion, and ring area. However, these relationships were not consistent among the three sites. Overall, there is not enough evidence to conclude that the first flowering causes or contributes to changes in wood density trends. Our findings suggest that studies should be conducted on the relationship between the architectural development of the crown and changes in internal wood characteristics. We corroborate the suggestion as reported by Burdon et al. (For Sci 50:399–415, 2004) of adopting the terms corewood and outerwood instead of juvenile and mature wood.