Does the Lack of Reference Ecosystems Limit Our Science? A Case Study in Nonnnative Invasive Plants as Forest Fuels

Abstract

Abstract In forest experiments the problem of inadequate controls often arises. True controls might not be required in case studies, comparisons along an environmental gradient, or comparisons of multiple treated and untreated areas. In a recent characterization of fuels in invaded and uninvaded forest conditions for four forest types at 12 locations in Maine, Maryland, Massachusetts, New Jersey, New York, Vermont, and Virginia, high-quality reference stands usually were not available as true controls. We called the uninvaded areas “comparison areas,” and applied a modified planar sampling technique to quantify live and dead fuels. No overarching pattern emerged; fuels in fire-adapted pitch pine differed from the three other forest types in that stands invaded by black locust had fewer 1- and 10-hour fuels, but more forbs cover and higher basal area. Invasive shrubs increased fuel height and density across most forest types. Invasive grasses in forests present an underrecognized hazard fuel if drought ensues. The comparison stand study design enabled uncovering of significant differences between invaded and uninvaded stands, especially in hardwoods and mixed woods, and fuels in softwoods were less affected by invasive plants.