We are back on the million dollar question: how will our forests develop in this uncertain era of climate change? Yes, many study showed that changing climate might have strong impacts on the dynamics of temperate forests, but let’s not forget that management and other factors played (and will play) an important role for European forests. Among the different forest ecosystems in Europe, the mixed silver fir-beech Dinaric forests are one of the most fascinating to me. If you do not know much about them, read more what researchers from University of Ljubljana and ETH Zürich found.
Dinaric Mountain forests: very special woodlands
When we talk about the Dinaric region, we intent the western part of the Balkan peninsula. Here a long mountain range stretches from Slovenia down to Albania and Kosovo: the Dinaric Alps. Many people may not know them well, but with their 645-km length the Dinaric Alps are the fifth most extensively mountainous area of Europe. Although the tree species are basically the same as the one we find in the Alps, when I visited this region I was totally startled to see how the species are mixed very differently along elevation (see figure below). Coming from the Alpine region, I am very much used to see beech and other broadleaved species dominating mid-elevation belts. As we climb uphill, spruce become the master of the forest, sometimes mixed with silver fir where the conditions allow. Here the situation is quite different. Spruce is only a “guest” in these mountains, and it grows optimally only in cold depressions at high elevation. The real king of the mountain slopes is Silver fir, which dominates elevations between 800 and 1300 m a.s.l., followed by beech that forms pure subalpine forest up to the higher timberline. More up we only find dwarf mountain pine and some alpine bush. Many areas in this region remain wild, due to high altitudes, steep slopes, rocky terrains and sometimes lack of surface water. This helped in providing habitat to a many animal species, including large predators as brown bears, wolves and lynxes, which are slowly returning to the Alps, as the latest news confirm.
The Dinaric region and the vegetation belts along elevation in the Dinaric Mountains in Slovenia (source: Boncina, 2011)
A long history of forest management
Since centuries, uneven-aged forest management in these forests has a long tradition to promote timber production and nature conservation, which are the most important ecosystem services for local communities. The presence of conifers such as silver fir and Norway spruce in the Dinaric fir-beech forests has high importance. Not only because of their economic value, but also because mixed stands are likely to be more resistant to climate change-induced natural disturbances than monocultures. In addition, mixed forests provide higher habitat diversity, are more productive and generally promote higher levels of multiple ecosystem services than pure forest stands. Although the current amount of conifers in these forest reflects the past interventions (i.e., promotion of spruce and fir over beech), maintaining a good balance between conifers and broadleaves is vital for these ecosystems.
The regional climate change projections in the Dinaric Mountain area indicate an overall increase of mean temperature and a decrease of precipitation, the latter particularly pronounced during the summer months. These forecasted changes are expected to induce substantial shifts in species composition (e.g., increase proportions of beech and decrease of fir) and productivity in the Dinaric Mountains. In addition to that, increasing browsing pressure on fir’s regeneration seems to jeopardize its ability to play a key role in the future of these forests.
Changes in fir and spruce proportions in the study area in the period 1912–2110. For the period 1912–2004 data derived from archival data while for the period 2010-2110 simulation results under the current management strategy and the current climate are shown (weighted means with standard deviations). Source: Klopcic et al. (2017)
Forest dynamics projections
In a study led by Matija Klopcic from the University of Ljubljana in collaboration with the Bugmann’s lab at ETH Zürich, researchers conducted a simulation-based study to assess the combined impacts of forest management, climate change and browsing pressure on these forests. They particularly focused on silver fir, and evaluate potential management options to counteract the decline of this conifer in these forests. Additionally to a scenario of “no management”, the researchers used a process-based forest dynamic model to simulate current management strategies as well as combinations of alternative silvicultural practices with and without reduced browsing from large ungulates. Or course including different climate change scenarios as well. The study was part of the large European FP7 project ARANGE, which stimulated the need for a special issue “Mountain Forest Management un a Changing World” in the European Journal of Forest Research (available soon).
Silver fir may strongly decline in the future
Results were not very encouraging for silver fir. Simulations along the elevation gradient showed that fir may almost disappear in low-elevation stands and that climate change might intensify its decline. Beech seems to be a very stronger competitor under future climate conditions, also because its regeneration not as preferred as fir by ungulates. However, there are great differences across stands and elevations and the situation is not evenly bad for fir. Due to projected higher temperature at higher elevations, spruce and fir may even increase their proportions in the sub-alpine climatic belt and find there a good refuge.
Changes in fir proportion in relation to its base proportion in the stand volume in 2010 (relative change; left axis) and absolute changes in fir proportion in the stand volume (right axis) under different management strategies and climate change scenarios. Modified from Klopcic et al. (2017).
What can we do with management?
If we do not adapt management systems in the face of climate change, future forests may be quite different as we see them now. This certainly depends on what to we want from our forests in terms of goods and services. I believe that a change in species composition may not be necessarily bad in some areas, for example where spruce and other species have been strongly promoted in the past merely due to economic reasons. A beech-dominated or a thermophilous broadleaved forest may also be able to provide a wide array of ecosystem services, and I believe that we can certainly adapt to make use of the resources that such a forest could provide to human society.
However, in our special “Dinaric” case, strong efforts in both forest and wildlife management must be undertaken in the coming decades for maintaining species mixture. Browsing pressure should certainly be reduced, to allow silver fir to regenerate successfully and maintain its competitiveness against beech. The researchers pointed out that a general silvicultural system cannot be prescribed for all forest stands as there are strong differences between elevation belts. A more “freestyle” silviculture combining measures of different silvicultural systems would enable managers to cope with future uncertainties and to maintain key ecosystem services from these beautiful woodlands.
Klopčič M, Mina M, Bugmann H, Bončina A (2017) The prospects of silver fir (Abies alba Mill.) and Norway spruce (Picea abies (L.) Karst) in mixed mountain forests under various management strategies, climate change and high browsing pressure. European Journal of Forest Research:1-20
See also another paper on future forest dynamics in the Dinaric Mountains recently published:
Mina M, Bugmann H, Klopcic M, Cailleret M (2017) Accurate modeling of harvesting is key for projecting future forest dynamics: a case study in the Slovenian mountains. Regional Environmental Change 17:49-64
Main photo: Mixed fir-beech forests in the Sneznik forest area. Author of the photo: Matija Klopcic