Effects of fire frequency and season on resprouting of woody plants in southeastern US pine-grassland communities

Abstract

Past studies suggest that rates of woody plant resprouting following a "topkilling" disturbance relate to timing of disturbance because of temporal patterns of below-ground carbohydrate storage. Accordingly, we hypothesized that fire-return interval (1 or 2 years) and season of burn (late dormant or early growing season) would influence the change in resprout growth rate from one fire-free interval to the next (Δ growth rate) for broadleaf woody plants in a pine-grassland in Georgia, USA. Resprout growth rate during one fire-free interval strongly predicted growth rate during the following fire-free interval, presumably reflecting root biomass. Length of fire-free interval did not have a significant effect on mean Δ growth rate. Plants burned in the late dormant season (February-March) had a greater positive Δ growth rate than those burned in the early growing season (April-June), consistent with the presumption that root carbohydrates are depleted and thus limiting during spring growth. Plants with resprout growth rates above a certain level had zero or negative Δ growth rates, indicating an equilibrium of maximum resprout size under a given fire-return interval. This equilibrium, as well as relatively reduced resprout growth rate following growing season fires, provide insight into how historic lightning-initiated fires in the early growing season limited woody plant dominance and maintained the herb-dominated structure of pine-grassland communities. Results also indicate tradeoffs between applying prescribed fire at 1- versus 2-year intervals and in the dormant versus growing seasons with the goal of limiting woody vegetation.

Factors affecting broadleaf woody vegetation in upland pine forests managed for longleaf pine restoration

“…Our results are similar to other studies citing a 1-3 year fire return interval as being necessary for limiting woody plant abundance (Waldrop et al, 1992;Glitzenstein et al, 2012). That frequent fire did not completely eliminate woody vegetation was not unexpected, as many woody species within longleaf pine ecosystems are capable of post-fire resprouting and often quickly regain their pre-fire stature (Boyer, 1990;Loudermilk et al, 2011;Grady and Hoffmann, 2012;Hiers et al, 2014;Robertson and Hmielowski, 2014). While many individual hardwoods can effectively get caught in a ''fire trap,'' repeatedly resprouting after being topkilled, some may eventually escape into the midstory and canopy owing to various factors such as canopy disturbance (e.g.…”

“…The likelihood of topkilling woody stems is contingent on characteristics of the fire regime, with high fire frequency and high fire intensity often offering the greatest woody plant control (Boyer, 1990;Robbins and Myers, 1992;Waldrop et al, 1992;Streng et al, 1993;Glitzenstein et al, 1995Glitzenstein et al, , 2012Brockway and Lewis, 1997;Robertson and Hmielowski, 2014). Fire behavior and resultant effects on woody plant communities can be both complex and variable, however, based on weather conditions at the time of burning and factors such as soils and topography.…”

“…On productive sites that favor rapid woody species growth, the temporal window for topkilling woody stems is shorter, requiring more frequent burning to prevent stems from developing into fire resistant sizes (Robertson and Hmielowski, 2014). While broadleaf woody vegetation is expected to be present on most sites in the longleaf pine range, species composition and woody vegetation abundance varies with edaphic conditions and site productivity, generally indexed by soil texture (Gilliam et al, 1993;Jacqmain et al, 1999;Rodgers and Provencher, 1999;Kirkman et al, 2004).…”

Fire environment effects on particulate matter emission factors in southeastern U.S. pine-grasslands

“…Dormant season burns are predicted to have lower EF PM2.5 and are often easier to accomplish because of the higher proportion of dead fuel and predictable weather patterns within the region. However, growing season burns are advantageous for reducing woody shrub vegetation (Robertson and Hmielowski, 2014), releasing grasses and forbs (Glitzenstein et al, 2003), and mimicking the historic pattern of lightning ignitions and associated native grass reproduction (Platt et al, 1991), which could possibly reduce PM 2.5 emissions over time.…”

Contrasting sapling bark allocation of five southeastern USA hardwood tree species in a fire prone ecosystem

“…Vigorous and rapid resprouting capitalizes on already established root structures and carbohydrate stores in order to produce an increased rate of growth and survival and is often associated with shorter fire return intervals (Keeley and Zedler 1978, Malanson 1985, Bowen and Pate 1993, Bellingham and Sparrow 2000, Bond and Midgley 2003. Species differ widely in their capacity for post-fire resprouting (Tappeiner et al 1984, Keyser and Zarnoch 2014, Robertson and Hmielowski 2014. Species that recover above-ground biomass more rapidly can better take advantage of newly available space and resources while simultaneously usurping growing space from competitors (Pausas and Keeley 2014).…”