Several models of the effects of silviculture, radial growth, and tree age on wood density have been developed, but they have rarely considered the roles of diverse seed origins and climate. We developed a model to test the effects of radial growth, tree age, climate, and seed-source origins on wood density in 21 diverse populations of jack pine in a common garden in Petawawa, Ontario, Canada over the last 24 years using a linear mixed-effects model. Although we found significant differences in wood density among diverse seed origins, there were no differences between seed origins having the same ring age and ring width, indicating an indirect effect on wood density of seed-source origin via radial growth. High variation in wood density among trees within the same population and between populations indicated high genetic control of wood density. The climate effect was significant on wood density in all populations, but smaller when radial growth was controlled. Climate effect did not differ significantly among populations. Precipitation in July negatively affected latewood density, whereas precipitation in May in the current year and September of the previous year negatively affected earlywood density. We concluded that a single model of jack pine wood density and radial growth could be used, either controlling for climate effects or not, as the relationship between wood density and radial growth is preserved among the diverse populations, and the climate effect controlling for radial growth in the model was only slight.

Abstract:

Effect of interannual climate variations on radial growth was compared among jack pine (Pinus banksiana Lamb.) of diverse geographical origins in a 41-year-old common-garden experiment in Petawawa, Ontario. Provenance experiments established from seeds transferred from different parts of a species range (from the northern United States to northern Canada) to the same environment might be considered as a simulation model of climate change and a shift of climate zones. The following questions are addressed: Did the response of growth to interannual climate variations differ among the provenances transferred within the experimental site? What climatic factors affect interannual growth variations of jack pine provenances? Tree-ring chronologies for 16 populations were developed for the period 1970–2004. The best climate predictors of radial growth were precipitation of June and March of the current year and precipitation of December of the previous year. Although, climatic factors affecting growth were similar between the provenances, absolute radial growth was proportional to the growth potential of the provenances. We conclude that variability due to seeds origins is not a significant source of variation for dendroclimatic studies of jack pine. Increased frequency of summer droughts might result in a growth decrease of jack pine © 2008 NRC Canada.

Résumé

Nous avons étudié les relations entre le climat et la croissance radiale annuelle de provenance de pin gris (Pinus banksiana Lamb.) établis depuis 41 ans dans un jardin commun à Petawawa en Ontario. Des tests de descendance établis dans des conditions similaires à partir de graines provenant de différentes parties de l’aire de distribution de l’espèce (depuis le Nord des Etats-unis jusqu’au nord du Canada) simulent des changements climatiques et des transitions entre différentes zones bioclimatiques. Nous avons tentés de répondre aux questions suivantes : Est-ce que la relation entre la croissance radiale interannuelle et le climat varie en fonction des provenances? Quelles sont les facteurs climatiques qui contrôlent la croissance radiale des différentes provenances. Des chronologies de la croissance radiale couvrant la période 1970–2004 ont été développées pour 16 provenances. Les facteurs climatiques les plus corrélés avec la croissance radiale sont les précipitations pour juin et mars de l’année en cours et les précipitations de décembre pour l’année précédente. Bien que les facteurs climatiques contrôlant la croissance sont les mêmes pour toutes les provenances, la croissance absolue variait en fonction du potentiel de croissance de chaque provenance. Nous concluons que la variabilité due à la provenance des graines ne constitue pas une source importante de variation dans la réponse dendroclimatique chez le pin gris. Une augmentation de la fréquence des sécheresses durant la période estivale pourrait entraîner une diminution de la croissance du pin gris © 2008 NRC Canada.

The effects of seed transfer and climate change on the width and basal area of tree rings were studied in 21 provenances of jack pine (Pinus banksiana Lamb.) grown in a common-garden plantation in Petawawa, Ontario, Canada. Seed-source origin significantly influenced both mean tree-ring width and mean annual basal area increment over a 25-year growth period (1975–1999). Temperature and precipitation transfer functions were developed to predict width and basal area of tree rings of the jack pine populations. The best predictors of growth were the transfer distances mean annual maximum daily temperature and annual precipitation between the plantation site and the seed origins. Radial growth of the jack pine populations was mainly related to temperature at seed origin and, to a lesser degree, to precipitation at seed origin. Extension of the transfer functions to three sets of independent data revealed significant correlations between estimated and predicted mean radial growth characteristics. Seed sources of jack pine originating from warmer and drier climates than that of the plantation site in Petawawa had slightly higher mean ring widths and basal areas than the local populations. The application of different climate change scenarios derived from general circulation models the developed transfer functions indicated that radial growth of jack pine may decline only if significant climate changes occur, which might happen before the mid 21st century. Both a higher radial growth of southern seed sources and a potential negative effect of a significant temperature increase and precipitation decrease in future suggest restricting the northward transfer of southern seed sources to less than 18 latitude. However, provenance specific differences in survivorship, frost- and disease-resistance, and cone serotiny should also be taken into consideration.© 2007 Elsevier B.V. All rights reserved.