Positive feedbacks between fire and non-native grass invasion in temperate deciduous forests

Abstract

a b s t r a c tNon-native grass invasions have the potential to change natural and prescribed fire regimes by altering fuels, which in turn may promote further invasion. We examined if invasion by Microstegium vimineum, a non-native annual grass, resulted in a positive invasion-fire feedback in eastern deciduous forests managed with prescribed fire and how this response varied across the landscape. Using paired invaded and uninvaded plots embedded in forest stands subjected to prescribed fire, we quantified differences in fire intensity and fuel loads, and fire effects on M. vimineum seedbank emergence, performance and spread. Invaded sites had less leaf litter and fine woody fuels, and increased fire intensity. Although fire reduced emergence of M. vimineum from the soil seedbank, sites subjected to prescribed fire had greater M. vimineum biomass and higher recruitment than unburned sites. Soil moisture strongly modulated M. vimineum response to fire, such that fire facilitated M. vimineum invasion more in wetter than drier sites. These findings indicate that deciduous forests are vulnerable to positive invasion-fire feedbacks, although the positive effect of fire may be less pronounced where soil moisture is limiting. The interaction between soil moisture and fire effects can inform management decisions regarding where to combine prescribed burning with intensive invasive control measures such as torching, hand pulling, and herbicide application.

Direct and Indirect Interactions between Landscape Structure and Invasive or Overabundant Species

“…For example, regime-shifts can be initiated when invasive grasses affect fire frequency or intensity in ways that further promote invasion. Microstegium vimineum is a non-native annual grass capable of positive invasion-fire feedbacks in deciduous forests except in wet soils [90]. Changes to the fire regimes make the landscape even more vulnerable to and likely to be dominated by invaders [69,91].…”

Changing Fire Regimes in Tropical and Subtropical Australia

“…Conclusion cycle" (Setterfield et al 2010;van Klinken et al 2013;Wagner and Fraterrigo 2015) due to the increases in the abundance of fine fuels. With increases in fire frequency and intensity (D'Antonio and Vitousek 1992), a decrease in native tree and shrub cover and abundance can result, which will further facilitate more grass invasion, further increasing the risk of higher intensity and more frequent fires resulting in an ever increasing self-perpetuating fire cycle (Flory et al 2015).…”

“…All successful plant invaders will change the structure, composition and habitat quality of native plant communities (Rossiter et al 2002;Grice et al 2013;Wagner and Fraterrigo 2015). Weeds affect ecosystems they invade in a number of ways with often obvious dramatic changes.…”

“…This occurs when invasive plants influence fuel loads, fuel distribution, fuel continuity or the timing of fuel curing (drying of the fuels), with repercussions for the intensity, timing, frequency and sequence of fires (Black et al 2016). Invasive grass species can cause dramatic changes in fire regimes through a positive feedback cycle, called a "grass-fire cycle" (Pausas and Keeley 2014b;Wagner and Fraterrigo 2015). The grass-fire cycle occurs when alien grass invades an area and increases the abundance of fine fuels, which increases fire frequency and intensity (D'Antonio and Vitousek 1992).…”

“…trichoglume), which are becoming pests species (Lonsdale 1994;Driscoll et al 2014;Douglas et al 2016). Having the potential to cause dramatic changes in fire regimes through a positive feedback cycle, called a "grass-fire cycle" (Wagner and Fraterrigo 2015) by increasing the fine fuel loads of an area and increasing fire frequency and intensity (D'Antonio and Vitousek 1992;Rositter et al 2003;Moon and Adams 2016;Fill et al 2016;Svejcar et al 2017).…”