To reach this conclusion, they have analyzed data from about 10.500 permanent plots with more than 236.000 trees collected during three National Forest Inventory (NIF). These censuses collect information for approximately 30 years and range from temperate forests in the northern Iberian Peninsula to semi-arid forests in the southeastern peninsula. In this work they have studied the temporal trends in the structure and demographics of Iberian forests since the 80s and analyzed how the effect of the factors underlying the demographic changes over time.
According to these statistics, since the decade of the 1980s, Iberian forests tend to be denser, more homogeneous and formed by larger individuals. In addition, there is a trend toward a decline in regeneration and growth along with an increase in mortality. The observed temporal trends in forest structure and demography were driven mainly by the interactive effects of climate and competition. However, these effects were not stable over time, observing changes in magnitude and even in the direction of the effects.
'What we see is that the effects of climate change are amplified in Iberian forests, which explains the demographic trends observed. In addition, these effects are not stable or continuous over time. The increased sensitivity of Iberian forests is largely due to increased competition as a result of changes in recent decades, such as agricultural abandonment and traditional forest management along with the increase of reforestation policies', says Julen Astigarraga, lead author of the study, who belongs to the Research Group on Forest Ecology and Restoration of the UAH Department of Life Sciences.
Despite these findings, the study suggests that these negative effects of climate change on the demography of our forests could be improved through changes in forest structure (e.g., reducing competition), this has important implications for forest management and adaptation of iberian forests to climate change.
Together with Julen, signed the article Miguel A. Zavala (Research Group on Forest Ecology and Restoration, Department of Life Sciences, and Franklin Institute), Verónica Cruz Alonso (Research Group on Forest Ecology and Restoration, UAHs Department of Life Sciences, and Center for Ecological Research and Forest Applications (CREAF) Cerdanyola de Vallès), Paloma Ruiz Benito (Research Group on Ecology and Forest Restoration. Department of Life Sciences. Universidad de Alcalá, and Research Group on Environmental Remote Sensing, Department of Geology, Geography and Environment, Universidad de Alcalá), Antonio Gazol (Pirenaic Institute of Ecology (IPE-CSIC), Zaragoza), Sergio M. Vicente Serrano (Pirenaic Institute of Ecology (IPE-CSIC), Zaragoza) and Enrique Andivia (Department of Biodiversity, Ecology and Evolution. Universidad Complutense de Madrid).
This study has been funded through a project carried out with the BBVA Foundation's Leonardo Grant to Cultural Researchers and Creators 2018, and by the MICINN DARE Project (RTI2018-096884-B-C32). The research group thanks THE MAP (Ministry of Agriculture, Fisheries and Food) for its access to the National Forest Inventory data.