The Mycorrhizae of Pioneer Species in Disturbed Ecosystems in Western Pennsylvania

Abstract

Study plots with ten types of disturbances were established in a Solidago-Aster community in western Pennsylvania. One year after disturbance, 93% of all species had vesicular-arbuscular mycorrhizae (VAM) and accounted for 92% of all plant cover. After 3 yr, 96% of the species had VAM and 96% canopy coverage. An adjacent 10-yr Solidago-Aster community had 100% VAM species. The VAM annuals, Ambrosia artemisiifolia and Setaria glauca, were major first year dominants while VAM perennials, Agropyron repens, Solidago canadensis, and Aster ericoides, dominated at 3 yr. The mean percent mycorrhizae of all dominants at 1 yr was 39% and 34% at 3 yr. Four disturbed sites had 100% VAM colonization after 1 yr and six sites after 3 yr. Severe physical disturbances (topsoil removed and topsoil-subsoil removed) resulted in complete colonization by VAM species and mean mycorrhizal infections of more than 75%. The plowed-disked-prometone and plowed-disked-vapam disturbances resulted in low levels of mycorrhizae after 3 yr. The plowed-disked-atrazine plot showed an initial severe decrease in percentage of mycorrhizae, but doubled its infection rate by 3 yr. Three non-mycorrhizal species (Chenopodium album, Rumex acetosella, and Polygonuspersicaria) were observed during the 3-yr period. C. album was the major dominant after 1 yr in the plowed-disked-fertilized site and R. acetosella a dominant in the plowed-disked-prometone plot.