Diversity makes for more resilient forests!

Faced with climate change and the growing demand for forests that benefit society, research on the creation of innovative forest stands is progressing well at UCLouvain. On the agenda: forest resilience to drought, improved CO2 capture, the effects on health of “forest bathing” – humanity is reconnecting with the forest ...

Read also: Forest management: a necessity!

As we know, one of the keys to limiting the impact of future climate change is the resilience of our forests. However, they are still often based on stands where all the trees are of the same species and age; these even-aged monocultures are particularly fragile. “The difficulty is the unpredictable nature of the future climate,” explains Quentin Ponette, a professor and researcher at UCLouvain’s Earth and Life Institute. “We don’t know the extent of future disturbances. The best thing to do is to rely on more diversified forests to cope with these hazards. In the next 50 years, many things can change – the climate but also the procession and dynamics of bio-aggressors.” Following the recurrent droughts of recent years, for example, a beetle called the typographer has been severely attacking the common spruce in the Walloon Region, as in many other regions of Europe, causing considerable economic and ecological damage. “The renewal of affected stands offers an opportunity to establish forests that are more resistant to change. Mixed forests, composed of a variety of species, are more resilient because they take advantage of the sensitivities and strengths of the different species present.”

A wider range of benefits

Diversifying forests would also broaden the range of benefits they offer to society, beyond wood production: CO2 capture, pollution reduction, biodiversity, a place for well-being and recreation. The mixture of species within our forests offers a multitude of advantages in meeting current societal challenges. “But there’s no standard recipe,” Prof. Ponette says. “The ideal mix of species doesn’t exist, it all depends on the environment and local conditions. So it’s important to study and understand how to optimise forests according to the specific context of each forest. This is the core of our research, based on the analysis of existing forest stands and the use of predictive models.”

Recently, Prof. Ponette’s team published two studies on the impact of species mixing on drought sensitivity (Jacobs et al. 2021) and on soil carbon storage (Osei et al. 2021).

Both studies are based on long-established stands, carefully selected to limit confounding factors. “In our study on drought sensitivity, for example, we showed that the beech-oak mixture had a beneficial effect on the growth of beech, but that this sustained growth made it more vulnerable during droughts,” Prof. Ponette explains. “In our study on carbon storage, we found that Scots pine is associated with greater soil carbon storage than the species mixtures assessed, but we know that single-species forests are more fragile to environmental disturbances. It would therefore be a mistake to consider only the absolute performance, which is lower with the species mixture in this case.” In addition to identifying the optimal combinations of species to associate, it’s essential to develop technical itineraries that take into account management imperatives, particularly in terms of complexity and cost. “This more operational approach is really important if we want to encourage the large-scale establishment of mixed stands, rather than continuing along the path of monoculture.”

Forests: good for your health!

The Dr. Forest project, to which Prof. Ponette contributes, is looking into the benefits of the diversity of tree species for human health. After similar events in Vienna and Leipzig, “Forest bathing” was organised in late September in Louvain-la-Neuve’s Lauzelle Wood to evaluate the effect forest bathing – depending on the tree species present – can have on mental health. Forest bathing is a practice that originated in Japan and is becoming increasingly popular in Europe. Apart from the well-being aspect of (re)connecting with nature, studies show that forest bathing has a physiological effect on the human body. Some scientists believe that the volatile and odorous molecules produced by trees can have a beneficial effect on heart problems, stress and the immune system.
Thus forests are at the heart of meeting current and future challenges, in terms of both climate change and human health. Researchers from UCLouvain and all over the world are working on the design of innovative management methods to meet these challenges. Knowledge sharing, interdisciplinarity and collaboration between scientists and with stakeholders in the field will be key to achieving sustainable solutions. In this context, Belgian researchers and field actors will have the opportunity to exchange regularly with the Canadian specialist in forest ecology, Christian Messier, within the framework of his Francqui Chair, whose inaugural lecture will take place on 12 October at KU Leuven.

Learn more about Christian Messier, Université de Québec à Montréal

Forest management: a necessity!

Why continue to cut down trees at a time when we want to protect our forests? Quentin Ponette, a specialist in forestry and forest ecology, sheds light on the need to continue felling trees in the context of forest management in order to meet current and future societal challenges.

While climate change is indeed a major issue, stopping all tree felling is not an appropriate measure. If forests are to continue to play their role as carbon sinks on the scale of our beautiful planet, we must first ensure that they are best adapted to current and future changes, and therefore ensure their renewal with diversified and complementary species, which requires opening forest canopies. Moreover, the forest ecosystem is not disconnected from the wood industry: carbon is certainly stored in the forest, trees and soil, but also in products resulting from wood processing; the use of wood also makes it possible to reduce CO2 emissions through a substitution effect, as wood replaces other materials that are more energy-intensive and/or more difficult to recycle.

We are also firmly convinced of the interest of truly multifunctional management, that is, management capable of combining a diversity of functions and services in a relatively limited space such as Lauzelle Wood. It is in this context that management can demonstrate its truly innovative character, and that this university woodland can serve as an inspiring model forest – the opposite of methods that have been applied indiscriminately since time immemorial.

Thus, in addition to the production of wood, of which felling trees is the tip of the iceberg, the management practised in Lauzelle Wood contributes greatly to increasing biodiversity by acting on numerous levers such as opening up certain environments, setting up an integral reserve, maintaining dead trees in their individual state or in the form of ageing islands, maintaining trees with high biological value, developing forest edges, fighting certain invasive species, managing the wetland floor which is home to beavers, and promoting diversified species and structures. It also ensures that this important aspect coexists with the reception of the public – the number of visitors is structurally increasing with the growing urbanisation of Walloon Brabant. This implies, in particular, a traffic plan that reserves quiet zones, securing paths in order to reduce the probability of accidents, and increasing public awareness/education regarding nature – in particular school-age children.

Finally, it is also obvious that managing the wood is involves explicitly integrating its context. If the wood plays an essential role in the ecological network of the territory, its environment is – a contrario – at the origin of numerous and diverse pressures: water discharges, pollutants, dissemination of horticultural species, etc. Which it is advisable to manage not only by planning, but by a dialogue upstream with the many actors concerned. 

 

Published on October 11, 2021