Reversing Mesophication Effects on Understory Woody Vegetation in Mid-Southern Oak Forests

Abstract

Mesophication has reduced fuel-bed flammability in the Mid-Southern US, limiting the effectiveness of fire alone in promoting disturbance-adapted woody species. We applied combinations of thinning (none, 7, and 14 m 2 ha -1 residual basal area) and seasonal fire (none, October, and March) at three sites and monitored understory woody response from 2008 to 2016. In combination, thinning and burning had strong negative effects on some mesophytic species (Pinus strobus, Ostrya virginiana, and Fagus grandifolia) and positively affected many shade-intolerant and fire-tolerant species formerly suppressed under closed canopies. Such compositional shifts were greatest at our most xeric site, and were related to treatment effects on overstory and midstory density. Seedling density of Quercus spp. nearly doubled (+2,256 stems ha -1 ) from pre-to postmanagement. Sapling response was less dramatic; however, indicator and ordination analyses often associated mesophytic and disturbance-dependent saplings with unmanaged and managed treatments, respectively. Fire-season effects were subtle, but more species and greater understory densities were associated with March relative to October burning. Although some mesophytic species (Acer rubrum and Liriodendron tulipifera) responded positively to thinning and resprouted aggressively after fire, our results demonstrate how thinning and burning can initiate the reversal of mesophication's effects on understory woody vegetation.

Revealing historical fire regimes of the Cumberland Plateau, USA, through remnant fire-scarred shortleaf pines (Pinus echinata Mill.)

“…woodlands at Arnold Air Force Base, Tennessee (AAFB; Stambaugh et al 2016) and, to the south, two records of historically very frequent fire exist from montane longleaf pine (Pinus palustris Mill.) in the Appalachian Mountains at Choccolocco Mountain (CHO) and Brymer Mountain (BRY) (Stambaugh et al 2017) for sustainable management (regeneration, growth, and disturbance histories; Hutchinson et al 2019), and measured responses to specific silvicultural and fire treatments (Harley et al 2018;Vander Yacht et al 2018). Currently, only one historical record documenting growth and fire history in a remnant shortleaf pine stand exists at the northern edge of the Cumberland Plateau (Hutchinson et al 2019).…”

Thresholds in woody and herbaceous component co‐existence inform the restoration of a fire‐dependent community

“…Clabo and Clatterbuck () noted similar but variable patterns in fire residence times across seasons. Fire season effects were not obvious in this study, but potential advantages of growing‐season fire in reducing hardwood competition (Vander Yacht et al, , ) without negatively affecting the herbaceous layers of shortleaf‐bluestem communities (Sparks, Masters, Engle, Palmer, & Bukenhofer, ) deserves greater research attention.…”

“…Thresholds are more useful when they more comprehensively capture restoration goals. In temperate climates, woodlands and savannas are often restored from degraded remnants that lack herbaceous layers (Vander Yacht et al, ) and fire‐tolerant woody regeneration capable of sustaining overstorey structure (Vander Yacht et al, ). Simultaneously promoting woody and herbaceous components is challenging given strong competitive and inhibitory effects between the two functional groups (Dohn et al, ; Mayer & Khalyani, ; Scholes & Archer, ).…”

How Much Does Fire Behavior of Leaf Litter Beds Change within Two Months?

“…Fire behavior also changed within a short time frame (e.g., the mean RoS of P. halepensis) in treatment "60" was only 34.9% of the value obtained in treatment "0", calculation based on Table S3). Even though these effects cannot be attributed solely to fuel bed compaction, seasonal differences in the BD of leaf litter layer (L-layer) (e.g., [41]) and fire behavior were also measured in forest stands (e.g., [56,57]).…”