Ecological value of retaining pyrophytic oaks in longleaf pine ecosystems

Abstract

Species intolerant to fire, defined as lacking adaptations needed to establish dominance in a frequently burned landscape, are found within fire‐prone ecosystems globally. Such species are frequently targeted for reduction or eradication to further conservation or restoration of biological diversity because the dominant paradigm in restoration of fire‐dependent communities is to reduce the dominance or eliminate fire‐intolerant invaders. To explore this paradigm, we examined the role of oaks (Quercus spp.) within fire‐dependent upland and sandhill longleaf pine (Pinus palustris) ecosystems of the southeastern United States. These pine‐oak ecosystems have among the highest levels of biodiversity in the temperate zone. This diversity is inextricably linked to a frequent fire regime and includes many species readily top‐killed by fire, particularly oaks, which were common in the early settlement landscape. In examining the diversity of oak species found within longleaf pine ecosystems, we identify a group of pyrophytic oaks and show that these oaks are critical components of sandhill and other longleaf pine ecosystems, and their occurrence should be considered as part of conservation and restoration goals. Providing a better understanding of the ecological role of such species will benefit conservation management and strategic planning in fire‐prone southeastern ecosystems and more broadly where fire is used as a management tool. © 2014 The Wildlife Society.

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

“…Absolute bark thickness and bark:wood ratio of Quercus marilandica, a short-statured oak commonly associated with fire-prone longleaf pine sites across the southeastern US (Peet and Allard 1993, Varner et al 2003a, Hiers et al 2014, exceeded the other four co-occurring tree species in almost all cases (Fig. 1).…”

“…1). Q. marilandica has previously been characterized by strong negative bark allometry (i.e., early allocation of resources to bark; Jackson et al 1999), highly flammable litter (Varner et al 2015), and slow sprout height growth (as reflected in its comparatively shortstature; Hoffmann et al 2003), which together illustrate its adaptation to more frequent fires and classification as a pyrophyte (Hiers et al 2014). Overall, these results are consistent with its widely reported occurrence and dominance across many fire-prone ecosystems in the eastern US (Abrams 1992, Hiers et al 2014.…”

“…The importance of hardwoods in pyrophytic longleaf pine ecosystems is a subject of ongoing debate (Kane et al 2008, Hiers et al 2014. Removal of hardwoods via herbicide, mechanical harvest and mastication, or high intensity fire is often a primary goal of southeastern US pine restoration efforts (Provencher et al 2001, Outcalt andBrockway 2010).…”

“…Longleaf pine savannas are characterized by frequent (fire return intervals , 10 years), low-intensity fire regimes (Platt 1999, Stambaugh et al 2011, the interruption of which results in the invasion of fire-sensitive (mesophytic) species that alter stand structure, composition, and ecological processes (Heyward 1939, Gilliam and Platt 1999, Varner et al 2005, Kane et al 2008. We hypothesized that species adapted to the endemic frequent fire regimes (the so-called ''pyrophytes''; Hiers et al 2014) would accrue thicker bark, a higher bark:wood ratio, greater bark taper, and likely have shorter stature owing to these growth trade-offs. Conversely, invading species (the ''mesophytes'') would have thinner bark, a lower bark:wood ratio, lower taper (i.e., the same relative allocation to bark along the bole), and, in light of these diminished investments in protection, be capable of taller stature.…”

Classifying forest inventory data into species-based forest community types at broad extents: exploring tradeoffs among supervised and unsupervised approaches

“…For example, in many temperate forest communities in the eastern United States (U.S.), recent decreases in the abundance of oak species have been associated with impacts on biodiversity, wildlife habitat, and water quantity (Fralish 2004;Nowacki and Abrams 2008;Hanberry 2013;Hiers et al 2014;Caldwell et al 2016). Because changes in tree species composition can affect forest functions in these ways, characterizing species composition of existing forest communities is important for understanding the functions of those communities (Tierney et al 2009; Thompson et al 2013).…”