Understory biodiversity, proportion ground cover, and available soil nutrients as functions of time since major burn in a temperate hardwood forest

Abstract

Forest fires are major ecological disturbances that can drastically alter an ecosystem for many years (Gill et al. 1994). Through the process of secondary succession, a disturbed ecosystem is recolonized by species and can eventually reach its pre-burn levels of biodiversity (Moorhead 1996). While the return of biodiversity that accompanies secondary succession is well-documented (Moretti et al. 2006, Driscoll 2010, Granström 2001), the process by which understory species diversity and ground cover are restored over time, particularly in temperate hardwood forests, is less well-documented than in areas currently more prone to fires (Gill et al. 1994, Hanes 1971, Keeley 1981, Adler et al.1998). With ongoing climate change making naturally-occurring forest fires a more realized possibility in more northward regions (Handler et al. 2014), a better understanding of secondary succession in temperate hardwood forests may allow for more effective future ecological management of burned areas. This text utilizes data from controlled burn plots burned in 1911, 1936, 1980, and 2017 to provide a better understanding of this process; additional factors evaluated included impacts of light availability on understory ground cover and levels of soil nutrients based on time post-burn. No data showed any significant correlations between any of these parameters, except that the 2017 burn plot was found to vary significantly from the other burn plots in biodiversity, in terms of both species richness and evenness. This may be because the process of secondary succession tends to be complete by forty years after a burn (Moorhead 1996) and the three oldest burn plots sampled were close to or older than forty years post-burn. This timeline of succession, along with likely uneven burning of the plots, may help explain our lack of significant data. This reinforces the idea that the first forty years after a burn are the most important in terms of ecological management and restoration of understory biodiversity in burned areas. Furthermore, the lack of correlation between light availability and understory ground cover suggests that the restoration of canopy complexity is not necessarily an impediment to the recolonization of understory species, and that the two can coexist well in recovering temperate ecosystems.