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The present study examines the influence of ecological conditions and silvicultural practices on the health of silver fir (Abies alba Mill.) stands,
with special attention to the implications of Viscum album, Armillaria and Heterobasidion annosum. Health of individual trees was estimated by
measuring defoliation, chlorosis, needle retention, cone production, stork nest, epicormic sprouting and lichen cover. For stand health we measured
regeneration. We used a systematic sampling throughout the Spanish Pyrenees, and analyzed the data by means of mixed models. We observed
damage on 15% of the trees based on defoliation levels and on 10% of the trees based on chlorosis. Defoliation, chlorosis and cone production were
more frequent in dominant trees while epicormic sprouting was more concentrated in the dominated layer. Stork nest and lichen cover may be
linked to low growth in low quality sites. The incidence of V. album on trees was 13.9%, and positively related to defoliation and chlorosis. We did
not find a clear relationship between H. annosum or Armillaria and decline symptoms. Both pathogens appeared to be widespread in silver fir
forests. No regeneration difficulties were observed anywhere. At stand level silver fir does not seem to be a species in decline. Silver fir was
favoured during the last period of intensive cuttings, whilst Pinus sylvestris and Pinus uncinata nearly disappeared. At tree level, fir decline and
health problems are more localized and advanced on seed trees left after the last cuttings.
This research was partially funded by the project RTA01- 071-C3-1 of the Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria and by the Action S3 of the project SILVAPYR (I3A-1-57-E). |
