Confirmed decline of spruce growth in southern Sweden

“Our results confirm observations of declining spruce growth from inventory data, indicating that spruce is responding to changing climatic conditions in Sweden,” says Maksym Matsala from the Southern Swedish Forest Research Centre at SLU.

New growth models

In a scientific article, the researchers describe how they developed new, simpler formulas for calculating growth in spruce, pine, and birch. The new functions, which perform as well as the classic ones, were used to identify trends in forest growth.

Matsala and his colleagues found no major changes in growth patterns for pine and birch. Pine stands dominate the northern half of Sweden, where climate projections do not indicate more drought‑prone conditions before the end of the century.

Decline for spruce

But for spruce, the development is worse. Data from the National Forest Inventory show a decline in recent years, and this decreasing trend is confirmed by the new model calculations. The new results are consistent with other studies in Scandinavia showing more favourable conditions in northern Sweden, where the climate is colder, and poorer conditions for spruce in areas that have become warmer.

“Under Swedish conditions, our models already show a negative effect of rising temperatures on diameter growth in spruce, which is the opposite for pine and birch,” says Maksym Matsala.

Read the paper: New individual tree models of basal area increment confirm decline of Norway spruce growth in Southern Sweden