Are there growth trends of the Swiss tree species over the past 5 years?

We are currently analyzing the drivers of wood growth of Swiss forest trees over the past five years (preliminary results).

Figure 1 Growth trends of the main tree species in Switzerland. Radial growth: radial increment per year; Cross section area growth: annual increment of the trees’ cross section area; Relative growth: Annual increment divided by the stem radius (preliminary results).

Wood growth is the result of determining factors at the time of growing but also a response to environmental conditions in the past (carry-over effects). Carry-over effects include conditions of hours, days or even years ago. It includes e.g., the determination of buds in autumn of the past year but also the life-span of different organs of a tree like the sapwood, the leaves or the carbon storage pool.

No general growth trend was found (Fig. 1). However, there appear decreasing trends for some species over the past four years (2012-2015). Generally, the standard deviation from the respective means is large and there appear different patterns for different species.