Species richness of urban forest patches and implications for urban landscape diversity

The vascular plant species richness of upland urban forest patches in St. Paul and Minneapolis, Minnesota, was found to be positively related to their size. There was no significant relationship between species richness and the distance of these patches to other patches. Mowing and trampling reduced species richness of patches, whereas planting increased richness. Landscape richness can be maintained at a relatively high level by leaving even small unmown forested patches within a more disturbed matrix. However, maximizing landscape diversity would require leaving large forest stands unmown. It is suggested that cultivation be deliberately used as a mechanism for increasing native species richness in urban forests.