Post-Fire Dynamics and Spatial Heterogeneity of Woody Debris Associated with Pinus halepensis in an Oak—Pine Mediterranean Ecosystem

• Published in: Écoscience (Sainte-Foy) 2012, Vol.19 (4), p.356-363
• Main Authors: Fournier, Thomas P, Brossier Benoît, Gauthier Olivier, Carcaillet Christopher
• Format: Article
• Language: English
• Subjects: Aleppo pine; biomass; chronosequence; chronosequences; drought; ecosystems; fire; Mediterranean forest; mortality; Pinus halepensis; plant communities; population dynamics; Quercus ilex; spatial variation; trees; wildfires; woodlands; woody debris
• ISSN: 1195-6860; 2376-7626

Wildland fire is the most important disturbance in Mediterranean ecosystems characterized by endemic yearly drought. Fires act on both the diversity and structure of plant communities. Because Aleppo pine (Pinus halepensis) is closely associated with wildfire, the dynamics of its population could regulate the load of woody debris (WD) during early decades before succession to oak-dominated vegetation (Quercus ilex, Q. pubescens). Here, we examine the effect of time since the last fire that affected the vegetation community on the load of WD. Pine dynamics should influence the structure of the WD, both fine and coarse. The sampling design is based on Mediterranean woodlands with different times since the last disturbance, enabling establishment of a proxy for a 130-y chronosequence. The density and biomass dynamics of Aleppo pine and WD were measured and the decay status of coarse WD assessed. The fire-date for each stand was determined on the basis of the structure of the pine population. The accumulation of WD load describes a U-shaped pattern. The high load of WD during the first 3 decades results from post-fire mortality and natural thinning of young trees; 100 y after fire, the WD load is the result of senescence of large, old Aleppo pines. These high loads of WD are concomitant with greater variation in the amount of WD and thus increased spatial heterogeneity within the ecosystem.