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Title: MORE THAN A CENTURY OF CHANGE IN THE AMES, IOWA FLORA (1859-2000)

Author
item NORRIS, WILLIAM - W NEW MEXICO UNIVERSITY
item Widrlechner, Mark
item LEWIS, DEBORAH - ISU
item THOMPSON, JIMMIE - RETIRED
item POPE, RICHARD - ISU

Submitted to: Iowa Academy of Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: We compared two comprehensive plant lists compiled in Ames, Iowa to document changes in the local flora over time. Our historic list was based on two published floras from 1871 and 1890 and on 1450 herbarium voucher specimens of plants collected in Ames between 1859 and 1899. We compiled our modern list during recent field work (1990-2000) in the city of Ames and its surroundings. Our goals for this study were to determine 1) long-term changes in composition (i.e., the proportion of native species), 2) long-term changes in the abundance of individual plant species, and 3) the extent of gains and losses of native and non- native species. We found that the proportion of native species declined over time from 83.5 to 71.2%. Native plants were significantly more likely to decrease in abundance and a less likely to increase in abundance than were non-native plants. In addition, historically uncommon plants (regardless of origin) were more likely to be lost from the flora then were plants that were historically more abundant. Of the 277 plant species that were added to the flora of Ames after 1899, 160 of them are non-native, including 11 aggressive, invasive species: garlic mustard, Japanese barberry, crownvetch, leafy spurge, Amur honeysuckle, purple loosestrife, Osage orange, white mulberry, European buckthorn, multiflora rose, and Siberian elm. This information should be useful to land managers, field botanists, and all those who wish to protect and restore the natural vegetation of Ames and nearby areas. We suggest that more intensive field work is needed to inventory the flora of other parts of Iowa. Such inventories are quite valuable for analyzing the human impact on Iowa's plant life.

Technical Abstract: We compared two floras compiled in Ames, Iowa: an historic flora based on two published floras (1871, 1890) and on 1450 herbarium voucher specimens of plants collected in Ames between 1859 and 1899, and a current flora compiled by us during recent field work (1990-2000). Our goals were to determine 1) long-term changes in composition (i.e., the proportion of native species) over time, 2) long-term changes in the abundance of individual plant species over time, and 3) the extent of gains and losses of native and non-native species. We found that the proportion of native species declined over time from 83.5 to 71.2%. Native taxa had a greater tendency to decrease in abundance and a lesser tendency to increase in abundance than did non-native taxa (p<.001). Furthermore, historically uncommon plant taxa (regardless of origin) were more prone to extirpation from the flora then were more abundant taxa (p<.001). Of the 277 plant species that likely entered the Ames flora after 1899, 160 of them are non-native, including 11 aggressive, invasive species: garlic mustard (Alliaria petiolata), Japanese barberry (Berberis thunbergii), crownvetch (Coronilla varia), leafy spurge (Euphorbia esula), Amur honeysuckle (Lonicera maackii), purple loosestrife (Lythrum salicaria), Osage orange (Maclura pomifera), white mulberry (Morus alba), European buckthorn (Rhamnus cathartica), multiflora rose (Rosa multiflora), and Siberian elm (Ulmus pumila). We argue that more floristic inventory work is needed to facilitate continued analysis of human impact on the flora of Iowa.