UAB: Thin leaves and strong roots gain ground in response to climate change

A recent study published in the Journal of Ecology, led by the UAB and CREAF, analyses 25 years of evolution of 445,000 trees in the Iberian Peninsula and confirms that the combination of climate change and rural abandonment is changing the distribution of certain species that are reaching their hot or cold limit.

The study, led by Josep Padullés, researcher at the Department of Animal Biology, Plant Biology and Ecology of the UAB and CREAF, explores how the combination of rural abandonment and climate change has affected the trees where they are at the limit of the heat and dryness and the cold and humidity they can withstand.

According to the results, which have taken into account almost seventy species, there is more forest density throughout the Peninsula due to the agricultural and silvicultural abandonment of recent decades, allowing forests to recover, but with a new distribution of species due to the impact of climate change.

In general, the data suggest that species that share traits such as strong roots or leaves that are easy to produce are the ones that are expanding the most. For example, in areas that are increasingly hotter and drier, Aleppo pines (Pinus halepensis) and cork oaks (Quercus suber) are gaining ground because they are more tolerant of higher temperatures and dryness. In contrast, those associated with riparian forests are decreasing, such as the common alder (Alnus glutinosa), which was already close to its limit and with the rise in temperature can no longer live in those areas. In colder and wetter regions, some species such as beech (Fagus sylvatica) and broadleaf oak (Quercus petraea) are expanding, while conifers such as maritime pine (Pinus pinaster) have declined, among other reasons, because colder ecosystems are becoming warmer and trees that previously could not survive because it was too cold, can now do so. Another reason could be that there is much less logging than before.

“Each species of tree, like any animal, can live in a certain temperature and dryness gradient and, if this threshold is exceeded above or below, it can no longer grow in those conditions. To get an idea, in the south of Catalonia we will not find beech trees because it is too dry, nor in the higher areas of the Pyrenees where it is too cold. With the increase in temperature these conditions may change and our research provides new data on how this may affect the distribution of trees,” explains Josep Padullés, lead author of the article.

Among other things, these results help to understand how the forests of the future could change and, therefore, to better manage the territory. For example, areas that are becoming increasingly arid could lose the biodiversity of animals and vegetation associated with more humid environments, such as riparian ecosystems, or increase the risk of fires if the species that “reconquer” these areas are more flammable, such as Aleppo pines.

Better adapted roots and leaves

The research also identified characteristics that make some trees adapt better than others to more arid or humid environments. In the case of dry conditions, species that have larger and thicker roots in relation to the total size of the tree stand out, since they can access deeper layers of the soil to get water and, therefore, survive when there is lack of water. “