Mediterranean pine needle loss analyzed for more efficient forest management
A study combines climate, field and remote sensing data to identify growth patterns associated with defoliation processes and mortality in artificial pine forests
Reforested areas in the Baza (Granada) and Los Filabres (Almería) mountain ranges have experienced severe die-offs in recent years, with extensive woodland loss. Needle or leaf loss (defoliation) is one of the best indicators of tree health, particularly in pine forests under stress. When trees lose their needles, or leaves, their photosynthetic capacity deteriorates significantly, reducing growth and often leading to mortality.
Identifying the causes of defoliation processes is crucial to adopting the appropriate forestry measures to retard these forests' decline. A study by the ERSAF group at the University of Cordoba, carried out by María Ángeles Varo Martínez and Rafael María Navarro Cerrillo, has focused on analyzing time series of LiDAR (Teleported Aerial Laser) data from the National Aerial Orthophotography Plan (National Geographic Institute) to evaluate the defoliation processes in the Baza-Filabres complex, an area much affected by droughts. The LiDAR data collected over the last 10 years, supplemented by field observations and climate data, have made it possible to verify the relationship between defoliation and early growth loss, allowing us to accurately map tree deterioration processes.
Furthermore, these data, and their mapping, allow us to study the drivers of these processes, which are related to tree density (competition) and climatic factors, mainly temperature. In fact, looking at the temperature anomalies in the period studied, the team found that the existence of a summer with abnormally high temperatures subsequently led to an increase in defoliation.
The results obtained ― both the growth mapping and the identification of early drivers of defoliation ― make it possible to plan forestry to mitigate or attenuate this damage. As Varo Martínez explained: “these pine forests originate from plantations introduced between the 1950s and 1980s, which, in many cases, have not been subject to silvicultural interventions, which increases the risk of fires, as well as mortality linked to climatic factors (such as severe droughts) or biotic ones (such as pests and diseases). Poorly managed pine forests are denser, which means a greater likelihood of defoliation processes occurring.”
The research team argues that forest management policies should focus on regulating tree density through thinning programs based on defoliation and mortality risk, while promoting structural and species diversity in reforested pine forests. “It would be advisable to implement silvicultural treatments that open up the canopy to promote balanced growth of the forest stand, optimizing the growth of remaining trees and encouraging more diverse vertical and horizontal structure,” explained Martínez.
The key: a laser from an airplane
The study's most innovative aspect is its use of time series from LiDAR data. These aerial LiDAR systems, deployed nationally through the PNOA-IGN, offer nationwide coverage and enable researchers to generate high-precision 3D maps of forest structure and measure vegetation characteristics such as height, canopy coverage, and growth changes, thereby providing valuable insights into forest decline processes.
Reference
María Ángeles Varo-Martínez, Rafael M Navarro-Cerrillo, “Understanding defoliation of Pinus plantations in the Mediterranean mountains using tree segmentation and ALS time series,” Journal of Environmental Management, Volume 395, 2025, 127837, ISSN 0301-4797, https://doi.org/10.1016/j.jenvman.2025.127837.
Journal
Journal of Environmental Management
Article Title
Understanding defoliation of Pinus plantations in the Mediterranean mountains using tree segmentation and ALS time series
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