Presence and dynamics of ambrosia beetles and other xylophagous insects in a Mediterranean cork oak forest following fire

Abstract

Abstract Cork oak ecosystems, which are biodiversity hotspots and have great socio-economic importance in the western Mediterranean Basin, have been experiencing serious decline in the last decades attributed to different causes, including wildfires. Besides direct mortality, the surviving burned trees become more vulnerable following fire and may be attacked by wood boring insects (Coleoptera), which may further affect tree vigor and give rise to massive dispersing offspring affecting surrounding areas. In the first spring after a wildfire that occurred in July 2013 in a cork oak stand in central Portugal, we set up different types of insect traps (interception, emergence and aggregation pheromone traps), and monitored them for up to 16 months. Fire occurrence had a great impact on cork oak trees attractiveness to xylophagous insects, which increased significantly with increasing fire severity. Living unburned trees located close to the fire edge were clearly avoided, while burned trees with no regeneration were the most attractive. Four species of ambrosia beetles, represented nearly 90% of all xylophagous insects captured in interception and emergence traps, namely Platypus cylindrus (Platypodinae), Xyleborus monographus, Xyleborinus saxeseni and Xyleborus dryographus (Scolytinae). Therefore, the presence of ambrosia beetles in recently burned forests should be carefully assessed, and their control should focus on preventing colonization and the spread of infestation. Forest management should primarily focus on increasing tree vigor, and on reducing the factors that may increase burn severity if a fire occurs. In the first years after a wildfire, it is advisable to avoid any activities that are likely to increase stress of burned and neighbouring unburned trees, such as cork extraction, branch pruning and soil ploughing. Additionally, post-fire logging and removal of dead trees before the next spring (when first emergences start to occur), and the use of pheromone traps, are other possible measures to reduce the number of beetles in these situations.