Effects of anthracnose on dogwood mortality and forest composition of the Cumberland Plateau (U.S.A.).

Throughout the eastern deciduous forest, flowering dogwood (Cornus florida) continues to decline due to the introduction of the fungus Discula destructiva, the cause of dogwood anthracnose. We compared the responses of dogwood populations to the anthracnose in both the mixed mesophytic forest of the Cumberland Plateau coves and the oak-hickory forest of the plateau uplands. We surveyed dogwood populations in four randomly located 0.1-ha plots in each forest site, and we surveyed community composition in eight randomly located 0.05-ha plots in each study forest. This study is the first to document dogwood mortality due to anthrac-nose within the geophysiological province of the Cumberland Plateau. Factors affecting the rate of anthrac-nose spread (evaporative potential, soil moisture, and light levels) differed between the coves and uplands, but trends in the data suggest that dogwood may be eliminated from each of the forests we studied. Moreover, changes in plant community composition since introduction of the fungus show an increase in two bird-dispersed species—blackgum ( Nyssa sylvatica ) and spicebush ( Lindera benzoin )—concurrent with declining dogwood populations. Decomposition of dogwood litter plays an important role in calcium cycling in these forests, and, on the poorly buffered soils of the Cumberland Plateau, calcium retention could lead to a decline in passerine birds, that depend on calcium for their shells, through loss of invertebrate food sources. As the dogwood anthracnose epidemic continues and the largest size classes of dogwood disappear, additional changes in species composition and community dynamics are likely to occur in these forests. Efectos de Antracnosa en la Mortalidad de Cornus florida y la Composicion del Bosque de la Meseta Cumberland (USA) Cornus florida continua deteriorandose en los bosques deciduos del este de los Estados Unidos a causa de la introduccion de un hongo destructivo: Discula destructiva. Este estudio compara las respuestas de las poblaciones de Cornus florida al hongo en los bosques mesofilos mezclados de los canones de la Meseta y en los bosques de encino hickory en las tierras altas de la meseta. Este estudio representa la primera documentacion del deterioro de Cornus florida dentro de la provincia geofisiologica de la Meseta de Cumberland. Ademas, utilizando una serie de datos del bosque mesofilo mezclado, este estudio ilustra los cambios en la composicion del bosque desde la introduccion del hongo. Los factores que afectan la tasa de crecimiento del hongo (potencial evaporativo, humedad del suelo y nivel de luz) son distintos entre los canones y las tierras altas, sin embargo, la tendencia en los datos sugiere que Cornus florida podria ser eliminado de los bosques estudiados. Un analisis de cambios en la composicion de la comunidad desde la introduccion del hongo demuestra un aumento de dos especies diseminados por aves ( Nyssa sylvatica y Lindera benzoin ), al mismo tiempo que decrecen las poblaciones de Cornus florida. Se anticipan cambios en el reciclaje de nutrientes relacionados a perdidas de Cornus florida en la Meseta.