Environmental Correlates with Germinable Weed Seedbanks on Organic Farms across Northern New England

The northern New England region includes the states of Vermont, New Hampshire, and Maine and encompasses a large degree of climate and edaphic variation across a relatively small spatial area, making it ideal for studying climate change impacts on agricultural weed communities. We sampled weed seedbanks and measured soil physical and chemical characteristics on 77 organic farms across the region and analyzed the relationships between weed community parameters and select geographic, climatic, and edaphic variables using multivariate procedures. Temperature-related variables (latitude, longitude, mean maximum and minimum temperature) were the strongest and most consistent correlates with weed seedbank composition. Edaphic variables were, for the most part, relatively weaker and inconsistent correlates with weed seedbanks. Our analyses also indicate that a number of agriculturally important weed species are associated with specific U.S. Department of Agriculture plant hardiness zones, implying that future changes in climate factors that result in geographic shifts in these zones will likely be accompanied by changes in the composition of weed communities and therefore new management challenges for farmers.