Climate control of wood formation : illustrated for Scots Pine at its northern distribution limit

The growth of trees is a spectacular and exposed process based on a highly interlinked complex of hidden and cryptic metabolic and signaling pathways not yet fully understood. In this chapter, we focus on a sequence of studies on Scots pine as an example tree species during the past 10 years in the north of Finland. We particularly compare annual height growth and annual growth in girth in the long term. Moreover, we give attention to the chronological coherence between the growth in height and girth during a growing season. Finally, we go down on the cellular level and screen various variables of the water conducting cells for their suitability as climatic proxies. Girth growth is promoted by a warm current summer and height growth by a warm preceding summer. Within a growing season, growth in height and girth culminates in the second half of June, clearly before the warmest period of the year in the second half of July. On the cellular level, it is concluded that diameter and wall thickness of earlywood tracheids are independent from one another and from tree-ring width and in consequence contain different climatic signals. These encouraging findings provide a strong rationale for further studies.