An interview with Āris Jansons, the “Silava” Latvian State Forest Research Institute
Forest scientists are both discussing climate issues and trying to identify potential benefits. How do the forest and trees feel in a changing climate?
Climate change or variability affects the tree species we know to a greater or lesser extent, and we must certainly try to understand what we can gain from these changes and how they could be usefully applied. Latvia as a country has agreed to and joined various climate-related conventions on reducing CO2 emissions and absorbing CO2, but the scale of Latvia (neither in terms of area nor population) is not large enough for us to have a significant impact. It must also be understood that the climate will continue to change for the next 100–200 years, even if everyone on Earth were to suddenly switch to 0% CO2 emissions! Why is that? Large processes in nature have just as much inertia – if we have “warmed up” something a little, it will take a couple of hundred years for this “something” to cool down again – in our case, we are talking about the world’s oceans – until the system returns to its original state! Therefore, the foundation of foundations must be laid on adaptation to the situation. This is not talked about much; the media discusses carbon sequestration, but information on adaptation appears little or not at all. Why? There are international obligations that have been assigned a financial value. And in relation to these obligations, we can be “scolded” and we will have to pay for it, or we can be praised and we will gain, which is why these matters have been brought to the forefront.
Essentially, adaptation needs to be at the forefront – how to make use of and adapt to the situation! In this case, one must adapt to what is happening, regardless of our actions and will.
Speaking of the forest… The forest does not “need” us to adapt things for it or in relation to it! The forest adapts itself! For example, if we look at the distribution range of the Scots pine: it is practically the whole of Eurasia (with minor exceptions)! A few pine trees can even be found in Spain and Turkey, in a typical Mediterranean climate. Within a species, there will always be individuals or genotypes that will survive and endure atypical conditions! What is adaptable is the interaction system between humans and the forest – forestry. If we wish to continue obtaining wood, which is and will remain an important renewable resource, we – foresters – must adapt! In the event of drastic changes, many trees may die because they will not be suitable for the new conditions. Some survivors, however, will “produce” many, many descendants, thus ensuring the continuation of the species, adapting in this way!
Natural selection!
Yes! In this case, we are interested in the largest (the maximum possible) portion of trees we have grown and cared for surviving!
In European Union discussions on adaptation, we – Northern Europe (Scandinavia and the Baltic states) – are still the “odd ones out”. In our region, the forest is still a serious object of economic activity. This is seen less in Central Europe, and even less so in Western Europe. By this, I do not mean that there is no economic activity in the forests of Central and Western Europe; it exists, but to a much lesser extent than here! The discussion in Europe as a whole is less focused on economic interests, and this tendency – not to talk about management – will likely strengthen. Forecasts show that a large part of Europe, starting from the Mediterranean region, may over time become unsuitable for forestry for a simple reason – it will be too hot and too dry! I assume that some trees will grow in these regions; according to the FAO (Food and Agriculture Organization of the United Nations) “lenient” definition, they will qualify as forest, but not as forest in our understanding and in the understanding of economic activity!
If we plan to continue using wood as a resource, it must “grow and originate” somewhere. Our region is and will be suitable for this! We are in a favourable situation. Of course, this does not mean that we should forget about adapting, but – I assume – the situation might even become better for us!
What are the factors we have identified that we should definitely count on in the future? What must we try to adapt to?
Drought in summer – that is the first one! Of course, it will not affect forest stands to the point of them starting to wither and die out, but it can certainly affect wood increment. We conclude this after gathering data from increment reconstructions in the region from Finland to Germany. If we talk about silviculture and forestry, increment is essential! What can we do? Could genotypes (trees) from places where drought is already more pronounced be suitable for us? We are researching this in both field and controlled conditions! Perhaps we can cross-breed the “more resilient” ones with our trees… This is being done! We are continuing work on developing methods to better evaluate which of our own genetic diversity (for example, more than 2,000 plus trees have been selected throughout Latvia for the Norway spruce, which form the seed and production base, and there are about 1,500 for the Scots pine) are more resistant to drought. This should be taken into account before we choose what to propagate! This is an important direction in which we are working!
The second serious factor is wind, which we talked about a lot at the Forest Science Day in Kalsnava in November! Even without wind conditions changing (how often we observe storms and what the wind speeds are in gusts), there will be more damage in the forest! Why? As we are already noticing, there will be more strong winds during the period of the year when the soil is not frozen. If a storm “happens” during a period when the forest soil is, for example, wet, trees are less stable and “perish” faster. What can we do? It is impossible to prevent damage completely, but it can be reduced! We must manage the forest in such a way that trees increase in diameter faster (become thick faster!). This approach has two advantages – a tree’s stability depends on its diameter, and if a tree grows in diameter faster, it is more stable. Secondly, if a tree with a larger increment reaches the target diameter faster, we can manage the forest in shorter time intervals. The probability of wind damage is directly dependent on the tree’s height. Up to a height of 10 m, the probability is close to 0; with every additional metre, it increases! The shorter the time interval from a 10 m high stand to reaching the target diameter and obtaining usable wood, the lower the probability that the stand will be affected by wind. Managing with the aim of increasing diameter means planting fewer trees per hectare.
A tree can adapt to wind quite successfully. We can observe this in forest stands near the sea… It is known that wind speed in gusts near the sea is the highest, and it decreases inland. If we look at wind damage – in the immediate coastal strip, in the first few hundred metres – there is none!
Yes, indeed! There is no storm damage, even though wind speeds are highest in these coastal areas! The trees have adapted! If one can put it this way: the tree understands what threatens it and directs its available resources towards reducing the threat. If we “give the stand more wind” – that is, by planting with larger distances between trees, a smaller number of trees per hectare, the wind will move through the stand more. The trees will be swayed in any case. The situation can be described as follows – it will not be so important for the tree to grow in height because “neighbours will not interfere”, but the winds will shake it quite strongly! Therefore: the tree will direct energy and nutrients to the root collar, to the stump, to the roots! So it does not blow over! This is a simplified way to describe adaptation to wind.
During the talks in Kalsnava, I heard mention of maple and linden stands in Latvia. We could see beech trees. What is the situation with broadleaved trees in Latvia? Are they becoming relevant?
There are tree species worth thinking about, but they will not replace birch! For example, linden and maple are quite useful for crafts. But there are certainly reasons why we have historically grown and used birch so extensively, rather than maple! For example, maple is very tasty to deer and stags. Linden is good for specific niche products, but it is unlikely we will grow it on large areas. The reasons are mainly related to the properties of the wood of the respective species.
However, we are, of course, setting up experiments. For example, regarding tending. Linden and maple stands are tended at different densities; we are evaluating what the increments are, how much damage from ungulates there is, etc.
Speaking of beech, can one truly obtain good seeds in just 20 years, as was mentioned at the Forest Science Day?
Two things should be discussed here. One – if we are talking about a number of 10–100,000 seedlings, seeds can be obtained from those trees that are already growing here. In the next seed harvest year, we can obtain not exactly ideal, but good enough seed material. This has also been considered, so we are planning to thin several stands in the forests of the Forest Research Station in the coming years, leaving only the highest quality, best trees, and then it will remain to wait for the next seed harvest, which, for the beech, similar to the spruce, is irregular. This year there were seeds! Last year we collected a small bag under 15 trees; this year there was a full car – sacks of seeds and the driver too! When the next harvest year will be, we shall see!
Second – seed production in commercial volumes. That will take time – maybe 15–20 years, hardly less. Currently, in the existing stands in Latvia, plus trees have been selected, just like for spruce and pine. Now one must collect scions, graft them, set up a seed orchard, and all of that must grow! All of this will take longer than many things in forestry. That is why it is so essential to plan long-term and adapt: both the forest and human thinking!
(Photographs taken at the Forest Science Day in Kalsnava, 7 November 2019, were used)