Non-native plant associations with wildfire, tree removals, and deer in the eastern United States

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Wildfires, tree removals, and deer herbivory are potential pathways for spread of non-native plants. I modeled the number of recorded nonnative plant species by county compared to wildfire area, tree removals, and deer densities in the eastern United States and also eastern forests. Species richness of 1016 plant species in 780 primarily forested counties decreased with increased values of the three variables; models equally showed negative relationships. For model predictions, based on withheld samples of non-native species counts, percentage wildfire area alone had the greatest association (R2 value of 31%) for non-native species richness in eastern forests; non-native species richness decreased with wildfire area until stabilizing at >1% wildfire area to a neutral relationship. For 1581 species in 2431 counties in the eastern U.S., the three variables each had an overall negative relationship with non-native species richness (R2 value up to 14%), without a consensus by three regression types of most influential variables. These formal models suggest that wildfire, tree removals, and deer herbivory generally may be nominal pathways for non-native plant spread at landscape scales in the eastern United States.