Forest conversion – the future according to the spruce

Forests perform many important tasks. In times of global warming, however, in addition to their function as an economic factor, they are increasingly reduced to save carbon. In climate protection goals and the European Green Deal, they are already firmly planned to compensate for greenhouse gas emissions from other sectors.

From 2018, the forest has not been struggling since the bad heat and drought years at the latest than since the 1980s, as large areas in northern, Central and Eastern Europe fell victim to the “acid rain”. “We see that the forests are still badly damaged. Even if individual years are somewhat wetter, like the last year, then this ensures relaxation, but trees are durable organisms, and the damage adds up, «says the head of the Wald- and Ecosystem resilience working group at the Potsdam Institute for Climate Impact Research (PIK), Christopher Reyer. According to the 2023 forest state survey, there are crown conversion in 40 percent of the trees, only 20 percent of all trees are considered healthy. The worst hit the spruces, which, as a flat root, suffered particularly from the extreme dryness and then fell victim to wind throw and bark beetles.

The last forest inventory, which was released last autumn, shows that the local forests have given up more carbon since 2018 – on the one hand because around a sixth of the spruce stock has since died, on the other hand because the trees store less carbon in their wood due to the dryness.

Successful permanent forests

In order to make the forest more resistant, the EU forest strategy 2030 supports a more natural management. The Working Group on Natural Waldwirtschaft (Anw) achieved great success, whose federal association celebrated its 75th anniversary this week in Schwäbisch Hall. »We have now evaluated satellite images from some parts of Germany. Five to ten years after our principles managed forests appear there as the green islands in the middle of their environment limited in its vitality. Resistance and resilience (resistance and adaptability, editor’s note) towards dry periods and heat are recognizable better, «reports the Federal Chairman, Hans von der Goltz.

Central to the good performance of so -called permanent forests are their mixed age structure and the mixture of native tree species. Because trees get along with the challenges of climate change: Even if individual types die in the course of one or more heat summer, the forest is preserved in its substance.

Unlike in the classic age group forest, in which all trees are planted and felled at the same time, trees of different ages grow in the permanent forest. This layer protects him from wind, and the moisture is better preserved. The top temperatures are up to five degrees below that of an age group forest. »Young trees that arise from nature rejuvenation also have the chance to immediately adapt to the changed water and temperature extremes with their genes. Therefore, they seem to be better dealing with climate change than their parents, «says Von der Goltz. If this is not enough, sowing of local tree species from regions would be used in which the trees have been used to dryness and heat for centuries, such as Bulgaria or Romania.

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In the worst case, there is the possibility to plant up to 20 percent new tree species such as tree hazel, fluff oak or cedar between the native ones. »However, the mixture alone does not save the forest. With a more natural, sensitive forest management, we no longer only have to take a look at the stability of the entire ecosystem forest with the integration of ecological elements, but with the integration of ecological elements such as dead wood, «said Von der Goltz.

Question many unexplained questions

The problem is also known in forestry: “In teaching, forest conversion has been a topic in teaching since the 1980s,” reports a topic, “reports Christian Ammer, owner of the chair for forestry and forest ecology of the moderate zones of the Georg August University Göttingen. “We noticed when we continue with the softwood, we had a problem. With climate change, research then gained a completely different dynamic. ”So the combination of species is favorable, which have a particularly high water requirement of different deep roots and at different times.

Many questions are still unclear: How much drought does a tree species can withstand? Or how do we find trees that create the balancing act to be able to handle frost these days and at the same time to cope with the prevailing climate conditions in 50 to 70 years? This uncertainty is also a topic in teaching itself. “We tell the students that forest conversion will determine their entire professional career,” says Ammer.

The Federal Environment Agency (UBA) also propagates in its publication “Netto-Null in 2045, expansion of the sinks by climate silence forests and durable wooden products”, “Little diversified and non-location-based (pure) stocks from needle wood in species and structural location-friendly leaf mixed forests”. The authors lean on the permanent forest concept: the forests should differ, for example, in the age, crown height and shape of the crown and shape of light and shadow. In contrast, experts from the UBA look at tree species from other places in the world with skepticism. The ecological compatibility for the water and nutrient balance as well as the nature conservation safety of foreign species must first be ensured.

“Such a permanent forest does not arise with a flap.”

Christian breastfeeding

Professor of for forestry and forest ecology

»In order for sustainable forest conversion to succeed, it is also about necessary changes in wood demand and wood use. In the end, a social negotiation process on the multifunctional forestry, reliable political framework as well as willingness and courage on the part of the relevant actors, «explains Judith Voß-Stamping, research assistant at the UBA in the specialist group strategies and scenarios on climate protection and energy.

In fact, the forest owners of Germany encounter the new challenges very differently. “The state forestry administrations do a lot to advance forest conversion,” assures the forest building expert Ammer.

In the private forest, the structures are more heterogeneous: there are small forest owners but also large businesses. While some acted in the sense of the administrations, others keep their previous management in the hope that it will not be that bad. Financial incentives for a conversion have recently been offering funding programs in all federal states. This will probably increase the natural management. The clearing industry, as it has been practiced over the centuries, is only allowed in many federal states with a special permit.

Get out of the niche

The idea of ​​the permanent forests is already around 100 years old. According to the Göttingen Professor of Forestry, she has gained a lot of popularity in recent years and has thus stepped out of the niche. “But such a permanent forest does not arise with a flap. It takes a few decades before a single -layer forest creates a vertically structured, «he says.

But there are many shades between clear cutting and permanent forest in the strict sense. For example, individual trees are carefully removed in the screen stroke to open the crown roof. This falls through the gap, and younger trees have a chance to grow towards the light.

It becomes difficult when large spruce stocks are completely died by heat, storm and bark beetle and a new forest is to be built up. The young trees are then exposed to the blazing sun. Some new planting dries up, especially in low -rain years. “There are more opportunities to avoid water stress if you rejuvenate under existing trees,” says PIK researcher Reyer. Especially when pioneer tree species are settled there, such as Birch, Espe (also called Aspe or trembling poplar) or birdberry, smaller trees can be used in their protection.

A great danger for all efforts to create a permanent forest through nature rejuvenation and intermediate planting is the high game population. »Up to 63 percent of the rare mixed tree species of too many deer are currently being eaten. The hunt therefore bears a great shared responsibility for the successful forest conversion, ”warns of the Goltz, especially if individual young trees are not fenced.

But even if the forest conversion succeeds, Ammer and Reyer think it is essential not to expect too much from the future forests in terms of carbon storage. »The ambitions are very high. Other sectors such as traffic and buildings do not achieve their goals and it is also not clear how the goals should be achieved. Politicians still expect that the forest is a depression and that we can calculate that. But that turns out to be very risky, «says Reyer.