Environmental drivers of local and temporal variations in the community of oak-associated borers (Coleoptera: Buprestidae)

Forest health is being challenged worldwide due to changing disturbance regimes. These changes could promote the abundance and diversity of secondary forest pests, like the Agrilinae (Coleoptera: Buprestidae) borers, which are frequently involved in oak decline in Europe. We assessed the contribution of environmental factors to local abundance and temporal dynamics of oak-dwelling borers in France. We set up green multi-funnel traps in oak stands exhibiting a gradient of decline across six forests in 2021 and monitored the traps for six consecutive years in one forest. The community of borers was homogeneous among the forests and included several Mediterranean species. Increasing severity of decline at the plot and stand scales enhanced the abundance and species richness of the borers and influenced the composition of their community. Tree density, longitude and spring temperature also influenced the abundance of several species and of the community. Our multi-year survey indicated that inter-annual fluctuations in decline level weakly correlated with those of borer species. Most of the species experienced a major crash in 2017, suggesting that extreme climate events such as a warm early spring followed by a late frost can decimate borer populations. This may explain why borer damage has recently been relatively limited in France.