Fifty Years of Change in Forest Understory Composition. III. Ecological Attributes of Winners and Losers

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Since European settlement, the forests of the Great Lakes Region have undergone dramatic changes. Regular timber harvests and increased road densities have altered the frequency and extent of disturbance, and contributed to corresponding surges in populations of exotics and white-tailed deer. These changes have altered the composition of understory plant communities. Using a historic data set and our own surveys of 59 northern hardwood understories, we examined the relationship between temporal shifts in local and regional abundance and 3 ecological attributes: taxonomic group, photosynthetic guild, and dispersal mode. We predicted non-graminoid monocots would decline more than dicots and ferns, and early summer herbs would decline more than other photosynthetic guilds (because non-graminoid monocots and early summer herbs are more vulnerable to deer browse). We also predicted species with limited dispersal would decline more than widely-dispersed species. Using G-tests, we found no effect of taxonomic group or photosynthetic guild on temporal shifts in abundance; however, there was a marginally significant effect of dispersal mode (G = 12.33, df = 6, P = .055). While 22% of animal dispersed species increased locally and regionally, only 8% of wind dispersed and 9% of gravity/ ant dispersed species increased on both spatial scales. These results indicate that the dispersal mode of a species is an important predictor of its local and regional abundance.


Presented at the 86th Ecological Society of America Annual Meeting, Monona Terrace, Madison, WI.

Presentation Number 59: Conservation Ecology: Terrestrial Biodiversity.

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