Dynamics of seasonal growth in a long-lived southern hemisphere conifer are linked to early season temperature

Standard correlation approaches in dendroclimatology provide limited scope to elucidate differences between years in timing of growth initiation and cessation. In the Southern Hemisphere (SH), with relatively few long-term climate reconstructions, a clearer understanding of signals contained in ring width variation is of particular importance. In this study, we monitored growth in detail at two sites (low and high altitude) in Lagarostrobos franklinii (Huon pine) for five growing seasons. In concert, local environmental data were recorded, and cambial samples taken on several occasions. Season duration in Huon pine at low altitude lasted about six months, generally starting in September/October and ending in April. At higher altitude, season duration did not exceed about four months and generally started during November, ending in March. The shortest season and smallest rings were linked to cooler conditions compared to other years. On the other hand, an earlier growth onset in the 2011 growing season was evidently brought on by unusually warm conditions in late winter. Growth onset was linked to a running mean temperature of about 8.5 °C and 6.5 °C at the lower and higher altitude sites, respectively. While effects of limiting water on growth cessation were not universally clear, our results suggest that limiting water (during hotter, drier summers) may reduce growth rates, and precipitate earlier growth cessation.