More timber from boreal forests under changing climate?

The effects of increases in temperature, precipitation and atmospheric CO2 concentration on timber yields from stands of Scots pine (Pinus sylvestris L.) in southern Finland (61 degrees N) are addressed. The assessment is based on simulations using a process-based model in which temperature, precipitation, and atmospheric CO2 are among the main drivers linking the dynamics of the tree stands directly and indirectly with the changing climate. These factors control photosynthesis, respiration, transpiration and the uptake of nitrogen and water, with consequent effects on the growth and development of tree stands. The timing of thinnings and the length of the rotation were related to the dynamics of the tree stand in compliance with the thinning rules applied in practical forestry. The simulations indicated that an increase in precipitation of 9 mm per decade alone did not affect timber yields. However, a temperature increase of 0.4 degrees C per decade, and the combination of temperature and precipitation increases would increase timber yields by 10% during one rotation. An elevation in the concentration of atmospheric CO2 by 33 mu mol mol(-1) per decade alone would increase removals of timber by 20%, and a combination of increases in temperature, precipitation and CO2 concentration would increase removals by 30%. A rise in precipitation did not have any effect on the length of the rotation, but the other combinations shortened the rotation; by 9 years in the case of elevating temperature, by 17 years in the case of elevating atmospheric CO2 concentration, and by 23 years in the case of the combined elevation of temperature, precipitation, and CO2 concentration due to more rapid tree growth and development. These changes can be expected to affect the supply of timber and also the profitability of forestry. (C) 1997 Elsevier Science B.V.