In forests, dead wood due to drought represents a opportunities for local biodiversityeither as food for the microbiota or to house a large number of plant and animal species such as insects, reptiles and even birds and mammals.
Loose fallen trees in the forest and in complete decomposition They are not very popular in society. We tend to think that they are a source of pests, that they indicate neglect or that they cause fires. However, the reality is more complex and surprising.
Research led by CREAF and the Autonomous University of Barcelona (UAB) has analyzed Scots pine forests in Catalonia, which have been affected by tree mortality for a decade, and shows that the dead wood produced is more varied and therefore also hosts greater biodiversity.
Specifically, stands affected by mortality have 83% more deadwood, with more fallen or standing dead trees, and 23% more different types of deadwood in various stages of decomposition. The most important point is the diversity of habitats they provide these trees, which are the food, the den or the shelter of many species of fauna and flora.
An example are woodpeckers, the oak tinderbird Phenillus robustus or the endangered beetle Rosalia alpina in beech forests. In addition, forests with dead wood also have a more complex structure and this offers greater diversity of microenvironments making the forest more resistant to new disturbances.
«If trees die due to drought, the dead wood they leave behind can become a lifeline for biodiversity. To study it better, in 2022 we visited twenty Scots pine forests that suffered from tree mortality due to drought about a decade ago.
What we discovered was really interesting: the nature began to fill these seemingly inert places with life. A calm and remarkable transformation that reminds us that, given enough time, nature can find its way to recovery,” said Faqrul Islam, CREAF researcher and first author of the study.
Local climate and biodiversity
Where can we find this valuable dead wood? The study, published in Forest Ecology and Management, suggests that the wetter places, such as the Pyrenees, are where more dead wood is concentrated and are more diverse. However, this situation is more volatile, as the Moisture makes them decompose faster. And this is a complicated situation: if they are not generated again at the same rate, the microhabitats generated will disappear.
On the other hand, decomposition is slower in cold or drier places, such as more Mediterranean locations, where, despite there being less dead wood, it is decomposing little by little and can provide its benefits for longer. So the fauna and flora that depend on it, and which often cannot live in other places, will also remain active longer.
Is the drought an opportunity or a disaster?
‘When we talk about it disturbances in ecosystems is usually a fundamentally anthropocentric view. We think about how this affects our economy or our well-being, or how the emotional connection we have with these ecosystems deteriorates. On the other hand, these ‘disasters’ for ecosystems are often part of their dynamics and represent an opportunity to create new habitats.
The problem arises when people increase the intensity or frequency of these disruptions,” explains Francisco Lloret, author of the article, researcher at CREAF and the UAB. This is demonstrated by this study, which analyzes the dead wood that emerged precisely as a result of the great drought of 2012 in Catalonia and highlights that “it has been an opportunity for many of the affected forests, because they new microhabitats emerged from dead wood that came into being.”
“This does not mean that the recurrence of periods of drought is clearly positive. Our results show that in some cases it can be interesting to save dead wood retain some weakened trees to promote this heterogeneity in the structure of the forest and its biodiversity, but taking into account that this process will have different speeds depending on the local climate,” adds Josep Maria Espelta, also a CREAF researcher and author of the article.
Dead wood due to drought seems not only a nuisance from a human point of view, but also a possible hazard due to the risk of fire. Instead, for nature, for which there is no non-recoverable wasteit is an opportunity for new life to blossom.