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Modes of Crown Vetch Invasion and Persistence

Abstract Plant invasions have been hypothesized to proceed at the local scale (i.e., individual patch or stand) according to one of several distinct spatial patterns. However, few studies have attempted to reconstruct the patterns of perennial herbaceous plant invasions at local scales due to difficulty in determining the age of individuals. We used herb chronology to determine the ages of roots within several crown vetch patches in order to characterize the spatial age structure of these patches. Additionally, we examined both sexual and vegetative crown vetch reproduction, with regard to potential impacts on local spread and persistence, through seed bank sampling and greenhouse experiments. We found little distinct spatial age structuring in crown vetch patches, perhaps due to a lack of older roots caused by rapid ramet turnover within patches. We also found no support for the hypothesis, proposed by several land managers, that crown vetch builds up a large seed bank. However, we did find that even small fragments of crown vetch plants are capable of vegetative regeneration, which may be important in explaining this species' persistence in spite of control measures.