We report the first dendrochronological assessment on the effects of the Epinotia subsequana (Lepi- doptera: Tortricidae) needleminer on Abies alba forests in the Aragon Pyrenees (northeastern Spain), near the southwestern distribution limit of A. alba. We built local residual ring-width chronologies, in fifteen A. alba stands, using dendrochronological techniques. We found a strong decrease in radial growth in the 20th century, during the 1996±98 period, only at the sites AS (Paco Asieso, 42°399 N, 00°179 W) and DI (Diazas, 42°389 N, 00°069 W). There were previous surveys of E. subsequana out- breaks and fir defoliation, in the studied sites area, in 1995±96. They showed that the radial-growth suppression was caused by E. subsequana. We compared radial growth in the non-defoliated stands with mean regional chronology. The greatest decline in radial growth was in 1996±97. Thus, there was a 1±2 year lag in radial growth suppression following the defoliation. The recovery of radial growth occurred in 1998±99.

Introduction

In the 1980s, a high mortality of silver fir (Abies alba Mill.) was observed in the central-western Spanish Pyrenees (Aragon-Navarra). This episode of fir decline has been related to an increased cli- mate variability and severe summer droughts (Ca- marero 2001). Some of the affected stands were lo- cally attacked by borer beetles of the Pityokteinesgenus (Coleoptera: Scolytidae) (Martin, Cobos 1986). In spite of controversial silvicultural treat- ments, such as the intense logging of affected trees, the decline has continued in some Pyrenees stands until now.