The effects of prescribed burning and canopy openness on establishment of two non-native plant species in a deciduous forest, southeast Ohio, USA

Abstract

Fire has often been shown to promote invasion by non-native plant species, but few studies have examined the process in temperate-zone deciduous forests. To examine the potential of prescribed fire to facilitate invasions in the Central Hardwoods ecosystem, we experimentally burned small plots and simulated aspects of fire at a forested site in southeastern Ohio, USA. Treatments included high and low burn intensity, lime addition, and litter removal to test hypotheses of population limitation by fire intensity, fire-caused nutrient release, and removal of leaf litter, respectively. Treatments were arranged in a randomized block design in two landscape positions (dry upland, moist lowland) and two canopy conditions (gap, no gap). The experimental sites were not significantly different from randomly chosen forest sites in any of 12 environmental variables. Seeds of two problematic non-native species ( Microstegium vimineum and Rosa multiflora) were sown into plots following treatment to test the possibility of seed limitation. We recorded germination and height growth at three dates 1, 4, and 14 months following burning. Germination was promoted by litter removal and high- and low-intensity fire treatments in M. vimineum, and by high-intensity fire in R. multiflora. Seedling growth of both species was greatest following high-intensity fire under canopy gaps. Germination in the second year showed treatment effects similar to the first year indicating persistence of fire effects. Both species showed stronger recruitment in valleys and in canopy gaps, reflecting an interaction of fire and landscape position. We infer that prescribed burning and canopy-opening management practices have the potential to facilitate invasion of the study area by creating conditions promoting establishment and growth of at least two non-native species. The absence of these species in previous studies appears to be due to a lack of propagules rather than the unsuitability of forest sites for germination or growth.