Assessing the impact of prescribed burning on the growth of European pines

• We model tree growth response to prescribed burning in European pines.
• Short-term postfire growth was reduced in P. halepensis and P. sylvestris.
• Short-term postfire growth was unaffected in P. nigra salzmannii and P. nigra nigra.
• Mid-term postfire growth enhanced in P. halepensis and P. nigra salzmannii.
• These trends varied when crown status and fire severity were factored in.

Prescribed burning to reduce surface fuel loads could help preserve pine stands by increasing forest fire-resistance, but its effects on tree growth, especially growth of European pines, are poorly understood. Characterizing the short and mid-term effects of prescribed burning on Pinus growth could provide valuable input to inform fire and forest manager decision-making. Here we use dendrochronology and mixed modelling to investigate whether prescribed burning has differential effects on the mid-term growth of dominant and suppressed Pinus trees under different levels of fire severity via an approach comparing observed post-burning growth against inferred tree growth without burning. Results showed reduced growth of Pinushalepensis and suppressed Pinussylvestris at year of prescribed burning. Mid-term post-burning growths were good for dominant P. halepensis and Pinus nigra salzmannii trees subjected to higher fire severities, whereas suppressed P. nigra nigra, P. sylvestris and P. halepensis grew less than expected without burning. Although prescribed burning tended towards negatively affect the mid-term growth of P. sylvestris and P. nigra nigra, trees with higher pre-burn growth rates showed better post-burn recovery. The effect of fire severity on growth was positive for P. nigra salzmannii but negative for P. nigra nigra. These findings show that as time since burning elapses, growth recovery may depend on fire-tolerance of the pine species, degree of fire severity, tree characteristics and tree performance prior to prescribed burn. Understanding and balancing these factors in Pinus forests should help better plan prescribed burning, both in terms of desired fire intensity and required burning intervals, without altering tree vitality.