• The inheritance of deforestation in the past and the increase in aridity of the last decades limit the incorporation of new holm oaks in forests of the Spanish Mediterranean.
• These results are based on an international study published in the journal PLOS ONE in which researchers from the Desertification Research Center (CIDE, CSIC-UV-GVA)
A study published yesterday in the digital edition of the journal PLOS ONE by an international research group involving scientists from the Desertification Research Center (CIDE), a joint center of the Consejo Superior de Investigaciones Científicas (CSIC), the Universitat de València and the Generalitat Valenciana, the US Forest Service Pacific Northwest Research Station, the Universidad de Alcalá and the Universidad de Zaragoza, shows the negative effects of aridity and deforestation in the past on the regeneration of holm oak (Quercus ilex) in holm oak forests of the eastern Iberian Peninsula.
The study has been carried out in the Iberian System, where two large-scale processes that may have important repercussions on the regeneration of its forests concur. On the one hand, the footprint of deforestation from previous periods for pasture, firewood and charcoal in areas that have been subject to human exploitation for the last 3,000 years. On the other hand, an increase in aridity due to rising temperatures and decreasing precipitation, both consequences of climate change.
The research team has compared holm oak groves in semi-arid areas, where the annual precipitation level is 400-450 millimeters per year, with others in areas where it rains 600-650 millimeters per year, called 'sub-humid'. In the last decade analyzed (2006-2015), less than a tenth of new plants are recorded than in the previous decades at both precipitation levels. This means that, in semi-arid oak forests, the number of new individuals is not sufficient for the oak forest to survive in the future.
“Aridity negatively influences both the establishment and survival of holm oak seedlings, which require protection against dryness and predators, and the decrease in the number of individuals and species of trees and shrubs that protect them from these problems,” explains Patricio García-Fayos, the researcher responsible for this study and current director of the CIDE.
According to the research team, aridity has accelerated especially with the increase in average temperature, one of the main consequences of climate change. However, deforestation has practically stopped in recent decades because rural depopulation has significantly reduced the intensity of associated activities such as the extraction of firewood, charcoal and livestock.
Restrictions on the incorporation of new plants seriously jeopardize the regeneration and, therefore, the survival of these forests. “As demonstrated in this work, it is important to know the processes that influence the dynamics of incorporation of new plants during the regeneration of holm oak forests, with a view to proper forest management and sustainable maintenance of our forests, especially in the current climatic context,” concludes Esther Bochet, CIDE researcher and co-director of the project.
Thus, the holm oak forests of the Iberian System that at the end of the 20th century received an average annual rainfall of 450 millimeters or less are currently in a situation of 'no return' in their capacity for spontaneous regeneration. This means that those species that depend on the holm oak for food or to complete their life cycle will also be negatively affected.
Reference:
Patricio García-Fayos, Vicente J. Monleon, Tíscar Espigares, José M. Nicolau and Esther Bochet. (2020) Increasing aridity threatens the sexual regeneration of Quercus ilex (holm oak) in Mediterranean ecosystems. PLOS ONE.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0239755
CIDE Communication
