Presenter: Faqrul Islam Chowdhury
Authors: Faqrul Islam Chowdhury (1,2,3), Francisco Lloret (1,2), Jordi Margalef-Marrase (4), Luciana Jaime (5), Teresa Sánchez-Mejía (1,2), Josep Maria Espelta (1,2),
(1) Universitat Autònoma de Barcelona, Bellaterra, Catalonia, Spain
(2) CREAF, Bellaterra, Cerdanyola del Valles, Catalonia E08193, Spain
(3) Institute of Forestry and Environmental Sciences, University of Chittagong, Bangladesh
(4) CIDE-CSIC, Moncada, Valencia, Spain
(5) Department of Agriculture and Forest Sciences and Engineering, Universitat de Lleida, Spain
Abstract
Drought-induced forest die-off is transforming Mediterranean ecosystems, potentially initiating complex successional trajectories and structural changes. We synthesize findings from three investigations into Scots pine (Pinus sylvestris) die-off events in NE Spain, analyzing the interplay between species composition (publication 1), regeneration (publication 2), and forest structure (publication 3).
We found that die-off triggers a shift in community composition. Vegetation transitioned from P. sylvestris-dominance to mixed forests enriched with drought-tolerant broadleaves (e.g., Quercus spp., Acer spp., etc.), particularly at the warmer, drier edges of the climate gradient. This transition benefits from the release of advanced regeneration stages into the canopy layer. Regarding the dominant species, P. sylvestris regeneration is strictly filtered by canopy structure and species position in the climatic niche. Defoliated habitats consistently fail to support recruitment regardless the climate, while open gaps facilitate seedling establishment in climatically optimal sites. Crucially, closed canopies serve as microclimatic refugia for saplings in marginal, stressful environments. Finally, we found that die-off acts as a catalyst for structural diversity, significantly increasing deadwood accumulation and decay classes, as well as the abundance of Tree-related Microhabitats (TreMs). However, these biodiversity legacies are climatically regulated; wetter sites experience faster decomposition, rendering these resources more transient compared to drier sites.
The studies suggest adaptive silviculture that maintains a mosaic of canopy structures to preserve closed-canopy refugia to protect P. sylvestris persistence while conserving advanced regeneration, which acts as the foundation for the transition toward mixed, resilient forests. Strategies should also promote to retain deadwood to sustain saproxylic biodiversity and structural heterogeneity.
Keywords: Pinus sylvestris, Drought-induced die-off, Species turnover, Deadwood and TreMs, Canopy refugia, Adaptive silviculture
