Differential Post-Fire Recovery of Tree and Shrub Growth and Water-Use Efficiency in a Mediterranean Coastal Dune System

Assessing post-fire recovery is essential to forecast how ecosystems will respond to future warmer conditions and higher fire severity. Such assessments must consider site conditions and the post-fire recovery of trees and shrubs. We used tree-ring data and intrinsic water-use efficiency (WUEi) to quantify the post-fire responses of a tree (Pinus pinea) and a shrub (Juniperus phoenicea) in Mediterranean coastal dunes located in the Donana protected area, SW Spain. We compared pines and junipers growing in an inter-dune slack with those growing in a nearby dune ridge. We quantified crown damage and bark char in pines impacted by a wildfire. Pines with lower crown damage after the fire showed a higher growth rate one year later. Growth decreased afterwards in the case of fast-growing pines from the slack site, whereas slow-growing dune pines showed increasing growth rates one to three years after the fire. The fire did not change the pines' WUEi, whereas the junipers located in dunes presented the highest WUEi values. Severe crown damage (damage > 60%) impairs long-term growth recovery in P. pinea. Open and heterogeneous landscapes can reduce the wildfire risk in the study Mediterranean area, where slack vs. dune and tree vs. shrub differences should be considered in post-fire management plans.

Automated summary

Assessing post-fire recovery is crucial for predicting the response of ecosystems to future warmer conditions and higher fire severity. This study used tree-ring data and intrinsic water-use efficiency (WUEi) to examine the post-fire responses of Pinus pinea and Juniperus phoenicea in Mediterranean coastal dunes. The results showed that pines with lower crown damage had higher growth rates one year after the fire, while fast-growing pines from the slack site experienced decreased growth rates. Slow-growing dune pines, on the other hand, exhibited increasing growth rates one to three years after the fire. The fire did not affect the pines' WUEi values, but the junipers in the dunes had the highest WUEi values. Severe crown damage impaired the long-term growth recovery of P. pinea. The findings suggest that open and heterogeneous landscapes can reduce the wildfire risk in Mediterranean areas, and post-fire management plans should consider differences between slack and dune areas as well as between trees and shrubs.