The distribution and severity of beech bark disease in the Catskill Mountains, N.Y.

Abstract

Abstract:The distribution and severity of beech bark disease (BBD) in the Catskill Mountains of southeastern New York state, U.S.A., were measured between 1997 and 2000. Forest composition was measured using wedge prism surveys and fixed-area plot counts of canopy species. BBD severity on individual trees was ranked from 1 (no disease) to 5 (dead) based on bark health and canopy loss. These data were analyzed at multiple spatial scales to determine possible controls of disease distribution and severity. BBD was present on almost all Fagus grandifolia Ehrh. (American beech) individuals encountered >10 cm diameter at breast height, but was most severe in larger diameter classes. Mortality due to BBD also increased with diameter class. A strong positive relationship was found between BBD severity and relative beech basal area at the tract (hundreds of hectares) and 100-m elevation band spatial scales, but not found at smaller scales. Successful long-range dispersal of the disease may therefore be dependent upon host density, while local conditions may control BBD severity within individual stands. The current status of BBD in the Catskills suggests these forests are entering the aftermath phase of the disease's progression and that BBD has become an endemic component of these forests.Résumé : La distribution et la sévérité de la maladie corticale du hêtre dans les monts Catskills du sud-est de l'État de New York aux États-Unis ont été mesurées entre 1997 et 2000. La composition de la forêt a été évaluée par un inventaire au prisme et le décompte des espèces dominantes dans des placettes à aire fixe. La sévérité de la maladie a été classée de 1 (sain) à 5 (mort) sur chaque arbre en se basant sur l'état de santé de l'écorce et la perte de cime. Ces données ont été analysées à plusieurs échelles spatiales pour déterminer les facteurs potentiels qui régissent la distribution et la sévérité de la maladie. La maladie était présente sur presque tous les hêtres à grandes feuilles (Fagus grandifolia Ehrh.) présents de plus de 10 cm au diamétre à hauteur de poitrine mais elle était plus sévère dans les plus fortes classes de diamètre. La mortalité due à la maladie augmentait aussi avec la classe de diamètre. Une relation positive étroite a été observée entre la sévérité de la maladie et la surface terrière relative des hêtres à l'échelle spatiale de la parcelle (centaines d'hectares) et de la bande de 100 m d'altitude mais pas à de plus petites échelles. La dispersion de la maladie sur de longues distances est par conséquent possiblement dépendante de la densité de l'hôte tandis que les conditions locales contrôlent vraisemblablement la sévérité de la maladie dans chaque peuplement. La situation pré-sente de la maladie dans les Catskills indiquent que ces forêts entrent dans la phase finale de la progression de la maladie et que celle-ci est devenue une composante endémique de ces forêts.[Traduit par la Rédaction] Griffin et al. 1760

A rapid upward shift of a forest ecotone during 40 years of warming in the Green Mountains of Vermont

“…3) loss of American beech (Fagus grandifolia) basal area at 732 m is attributable to the invasion of the beech scale (beech bark disease) in the late 1960s, which has killed 80-90% of mature beech trees (27). The highest-elevation American beech (i.e., 792 m) increased in abundance probably because of the limited susceptibility of young trees at low densities to beech bark disease (27,28). Declines of American beech in the lower portions of the ecotone were largely offset by large increases in sugar maple (Acer saccharum) basal area of 60% (6.8 m 2 ha Ϫ1 ) and 115% (2.6 m 2 ha Ϫ1 ) at 732 and 792 m.…”

Subcontinental impacts of an invasive tree disease on forest structure and dynamics

“…2d; results for other common species were qualitatively similar), presumably because the density of small beech has increased so dramatically with BBD. Based on other research, it is clear that in given stands and regions species composition has changed as a possible consequence of BBD (Griffin et al 2003), but at a landscape scale, it appears that beech is predominantly replacing itself. Thus, BBD is altering North American hardwood forests to a condition where trees are of generally smaller stature (because BBD kills mature beech trees) but with no decline in the space occupied by beech.…”

Tree species of concern in New Brunswick, Canada. I. Current status and threats

“…Surveys in Nova Scotia and Prince Edward Island indicate a frequency of disease-free trees of about 2%, perhaps reflecting intensive exploitation of private woodlots, with removal of many of the undiseased trees. Griffin et al (2003) reported a much lower percentage (0.02%) in the Catskill Mountains of New York State, where the occurrence of the disease is more recent.…”

“…It has been detected as far south as West Virginia and west to Ohio. The "killing front" of the disease generally results in high mortality among mature trees (Griffin et al 2003). Seed production is reduced in diseased trees, but root suckers are often abundant, creating an "aftermath forest" characterized by small, heavily damaged trees of clonal and seed origin that may live for decades, before succumbing to the endemic insect-disease complex (Houston 1975).…”