Submitted to: Iowa Academy of Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2001
Publication Date: N/A
Interpretive Summary: Americans cultivate many introduced woody plants as important sources of food and forest products and to beautify urban and rural landscapes. A few of these non-native trees, shrubs, and vines have become serious pests, invading native plant communities or becoming range and agricultural weeds. Many are not yet serious pests, but have escaped cultivation and may be sources of future outbreaks. Other potentially invasive woody plants are not (or are only rarely) grown, and we often know little about their adaptation or reproductive biology. Thus we should assess the risks caused by the cultivation of non-native plants and the introduction of new ones. There are methods to help predict the invasiveness of woody plants in North America, based on an analysis of their biology and known records of invasions worldwide. But they were developed to work across the entire continent, so they don't account for differences in local adaptation that trees and shrubs naturally evolve. My study reviews the use of climatic comparisons to predict woody plant adaptation. The native ranges of 28 non-native, woody plants invasive in Iowa are mapped and compared to parts of the world with environments resembling Iowa's growing conditions, based on January mean temperature, moisture balance, and latitude, three factors limiting plant survival in the north central U.S. Regions with the highest concentrations of the 28 plants studied are found in southeastern Europe and northeastern China, which also have growing conditions similar to Iowa's. This information will be valuable for conservation biologists, land managers, and the nursery industry as we work to improve methods to evaluate the invasive threats of non-native woody plants in Iowa and nearby states.
Technical Abstract: Americans cultivate many introduced woody plants as sources of food and forest products, as well as for urban horticulture, amenity and wildlife plantings, and windbreaks. A few of these species have become serious pests, disrupting native plant communities or functioning as range and agricultural weeds. Many are not yet serious pests, but have escaped cultivation and serve as sources of future outbreaks. Other potentially invasive woody plants are found among species that are not or are only rarely cultivated, for which we often know little about their adaptation and reproductive biology. Methods have been developed to evaluate the invasive potential of woody plants in North America, by using analyses of life history, biosystematics, phytogeography, and records of invasions world wide. But these methods were developed to make predictions on a continental scale, so they do not account for local adaptations that woody plants have evolved. This study reviews the use of environmental analogs in predicting woody plant performance. The native ranges of 28 non-native, woody taxa invasive in Iowa are then mapped and compared with the occurrence of environmental analogs to Iowa growing conditions, based on January mean temperature, moisture balance, and latitude, three factors limiting woody plant survival in the north central US. Regions with the highest number of native taxa among the 28 taxa are found in southeastern Europe and northeastern China. These regions overlap with the locations of climates analogous to Iowa growing conditions. This information should be valuable for conducting a geographic risk analysis to refine existing methods for evaluating the invasive potential of non-native woody plants in Iowa and nearby areas.