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Questions: A paradoxical co‐existence challenges woodland and savanna restoration worldwide: How are shade‐intolerant, flammable herbaceous layers promoted while maintaining the shade‐casting, more fire‐sensitive woody regeneration that sustains overstorey structure? Where restoration success consisted of robust, diverse herbaceous layers and vigorous, well‐stocked Pinus echinata regeneration (hereafter, shortleaf‐bluestem response), we asked: are there targetable conditions of overstorey, understorey, topography, and proximity to mature Pinus echinata that simultaneously maximize desired woody and herbaceous understorey components? Do these conditions and dependent responses differ across canopy disturbance level and fire season? Location: Cumberland Plateau, Tennessee, USA (36°04′8.11″ N, 84°50′38.36″ W). Methods: We measured 12 shortleaf‐bluestem response and 17 explanatory condition variables at 345 plots spanning an experimental restoration gradient (canopy disturbance level and fire season combinations). We ordinated variation and identified response thresholds using a multivariate regression tree. Differences across tree groupings and splits associated response thresholds with specific explanatory conditions. Results: Pockets of substantial Pinus echinata regeneration (>3,000 stems/ha), C4 grass density (>40,000 ramets/ha), and herbaceous diversity (increase from 22 to 205 species) occurred 7–14 years after canopy disturbance and 3–8 fires. Such shortleaf‐bluestem response was maximized at 3 m2/ha residual tree basal area, 11% canopy closure, reduced midstorey density (5,000 small‐sapling stems/ha), and southwesterly aspects within 70 m of mature Pinus echinata. In contrast, shortleaf‐bluestem response was negligible at 11.3 m2/ha basal area and 68% canopy closure. Fire season, snag basal area, slope, and slope position effects were minimal. Conclusions: We identified specific conditions fostering the co‐existence of desired herbaceous and woody understorey components, addressing a major woodland and savanna restoration challenge and expanding on previous threshold concept applications by simultaneously considering multiple desired responses. Results can direct the restoration of imperiled shortleaf‐bluestem communities east of the Mississippi River, USA, where work has been scarce or ineffective, and similar approaches could inform fire‐dependent woodland and savanna restoration worldwide. [ABSTRACT FROM AUTHOR]

Thinning and burning can restore imperilled oak woodlands and savannas in the Southern Appalachian and Central Hardwood regions of the USA, but concomitant effects on fuels are less understood. We monitored (2008 to 2016) fuel load response to replicated combinations of thinning (none, 7, and 14 m2 ha−1 residual basal area) and seasonal fire (none, March, and October) at three sites. All treatments except burn-only increased total fuel loading. Thinning doubled (+16 Mg ha−1) 1000-h fuels relative to controls, and three fires in 6 years did not eliminate this difference. Increasing thinning intensity did not consistently enhance the combustion of larger fuels. October fires reduced 100- and 10-h fuels more than March fires. Burning alone reduced leaf litter and 1-h twigs by 30%. Burning after thinning doubled this reduction but increased herbaceous fuels 19-fold. Herbaceous fuels increased at a rate that suggests compensation for losses in woody fine fuels with continued burning. Where fuel reduction is a goal, restoration strategies could be more intentionally designed; however, oak woodlands and savannas are inherently more flammable than closed-canopy forests. Management decisions will ultimately involve weighing the risks associated with increased fuel loads against the benefits of restoring open oak communities. We monitored fuel loads during oak woodland and savanna restoration in the Mid-South. Large (≥2.54 cm in diameter) woody fuels increased with increasing thinning intensity, and subsequent burning often failed to reduce this addition. Burning and thinning resulted in a net reduction in smaller fuels: increases in herbaceous fuels did not offset decreases in twigs and leaf litter. [ABSTRACT FROM AUTHOR]

Establishing herbaceous groundcover is essential for oak woodland and savanna restoration. In the Appalachian region, woody vegetation in the understory can persist through many fires and interfere with achieving this goal. Herbicide applications could reduce such vegetation and interact with canopy-disturbance and fire to accelerate restoration. In stands thinned to woodland (16 m 2 ha −1 , 75% canopy closure) or savanna (5 m 2 ha −1 , 24% canopy closure) conditions and burned biennially in the fall (October) or spring (March), we economically applied triclopyr (Garlon® 3A) to understory woody plants using foliar and cut-surface techniques in the fall between fires. From 2011 to 2013, only minor differences in vegetation were observed between areas managed with canopy-disturbance and fire (CF) and areas where herbicides were also used (CFH). Small-sapling (≥1.4 m tall, <7.6 cm DBH) density in CF was 2,566 stems ha −1 greater than CFH in 2012. This difference was (1) the only woody control CFH attained beyond CF, (2) only lasted a single growing-season because it was mostly fire-sensitive species top-killed by subsequent fire, and (3) only led to increased herbaceous groundcover in savannas burned in the fall. This included the greatest reported increase in herbaceous groundcover (graminoid +18.2%, forb +8.0%) to be associated with herbicide applications under partial oak canopies in the Appalachian region. Expanding herbicide target constraints, completely removing undesirable seed-sources, increasing triclopyr concentration, exploring tank-mixes, and alternative application timing ( e.g. , prior to canopy disturbance) could improve effectiveness; however, fire suppression throughout the Appalachian region has increased the dominance of fire-sensitive woody species. Our results demonstrate how such composition can reduce the utility of herbicides relative to fire during oak woodland and savanna restoration. [ABSTRACT FROM AUTHOR]

The removal of fire’s influence on plant community succession has resulted in the near disappearance of oak ( Quercus spp.) woodlands and savannas from the Appalachian region. Negative trends in associated plant and wildlife species could be reversed if these communities are restored, but management has been limited by inadequate canopy disturbance, resprouting of woody plants, and a lack of empirical research. To address these issues, we evaluated herbaceous and woody vegetation response (2008–2012) on the Cumberland Plateau in Tennessee to 5 replicated treatments involving canopy reduction (14 m 2 ha −1 [woodland] or 7 m 2 ha −1 [savanna] residual basal area) and fire-season (mid-March [spring] or early October [fall]) combinations and unmanaged controls. All categories of woody vegetation except large-saplings (⩾1.4 m tall and ⩾7.6 but <12.7 cm diameter at breast height [DBH]), increased in density as canopy disturbance increased. Fire temporarily reduced small-sapling (⩾1.4 m tall and <7.6 cm DBH) density, but resprouting resulted in densities equal to or exceeding pre-fire levels. Herbaceous richness increased from 22 to 167 species following canopy disturbance and fire (2008–2012). Native cool-season grasses dominated herbaceous response in treated sites. Herbaceous groundcover, richness, and diversity increased as canopy disturbance increased, and the rate of increase accelerated once basal area was reduced below 15 m 2 ha −1 or 30% canopy closure. Following fire, canopy disturbance remained influential as indicated by greater herbaceous response in savannas than woodlands. Graminoid and forb groundcover, herbaceous richness, and herbaceous diversity were 24X, 11X, 9X, and 8X greater, respectively, in treatments than controls by 2012. Invasive species were rare and increased minimally with increasing disturbance. Our results demonstrate the utility of canopy disturbance in conjunction with fire for restoring oak woodlands and savannas from closed-canopy forest conditions. Basal area reduction to 15 and 7 m 2 ha −1 respectively approximated woodland and savanna canopy conditions, and increased herbaceous-layer development. The less intense October fire had similar effects on vegetation as the more intense March fire, but greater differences could become apparent following repeated burning. Long-term research documenting the response of vegetation to repeated fire is needed to promote successful oak woodland and savanna restoration throughout the Appalachian region. [ABSTRACT FROM AUTHOR]

[Display omitted] • Edge, thinning, and site-quality effects shape regeneration in red pine plantations. • Canopy openness often greater in red pine plantations than adjacent hardwoods. • Thinning and increasing distance from hardwood edge decreased regeneration density. • Red pine plantation interiors favor oaks and black cherry over undesirable species. • More intentional plantation management may further promote desirable regeneration. Red pine plantations may promote more desirable hardwood regeneration than hardwood stands because of differences in: 1) the composition and quantity of tree seeds available, and 2) abiotic and biotic properties of growth and establishment environments. However, information on how distance from hardwood edges, thinning of overstory pine, and site quality shapes hardwood regeneration properties in red pine plantations is scarce. Such information would aid in understanding and managing red pine plantation effects on hardwood regeneration processes and guide spatial and temporal rotations of such effects across landscapes. To elucidate relationships, we monitored hardwood seedlings and canopy openness across transitions from hardwood edges to red pine plantation interiors at 40 sites spanning a site quality gradient in northwestern-lower Michigan. Hardwood seedling density: 1) declined substantially from edges to interiors at all but low-quality sites before stabilizing 30-m into plantations, 2) was reduced, or not affected, by thinning despite positive effects on seedling light environments, and 3) was greater at intermediate than high- and low- quality sites. From edges to interiors, species composition shifted towards Acer rubrum , Quercus species, and Prunus serotina and away from Acer saccharum , Fagus grandifolia , Fraxinus americana , and Ostrya virginiana. Species increasing in relative abundance and/or density from edges to interiors were generally more drought-tolerant, shade-intolerant, large-seeded, and animal-dispersed than decreasing species. Shifts towards less shade-tolerant species from edges to interiors were consistent with increases in canopy openness and were most pronounced where changes in light were greatest (i.e. , thinned plantations on high-quality sites). Changes in hardwood seedling density and composition were likely driven by differences across species in dispersal traits, seed characteristics, and relative adaptation to interior conditions (likely hotter, drier, and nutrient poor). To promote commercially valuable hardwoods, increase mast for wildlife, or improve climatic resiliency, the most suitable targets for conversion to hardwoods may be plantations with significant interiors (i.e. , area > 30-m from hardwood edges) on higher quality sites adjacent to desirable seed sources (e.g. , Quercus rubra , Prunus serotina , Acer saccharum). More desirable hardwood regeneration may result from reevaluating thinning timings and intensities originally designed to maximize red pine production. Our results also indicate that intentional management of surrounding hardwood forest composition (i.e. , seed sources), within plantation retention of hardwood islands (e.g. , mature oak stems), and greater control of Acer rubrum competition may further increase the desirability of hardwood regeneration in red pine plantations. [ABSTRACT FROM AUTHOR]

Across the Southeastern U.S., including the Cumberland Plateau of Tennessee, prescribed fire and overstory thinning are being used to restore areas of closed-canopy hardwood forest to open woodland and savanna. We used acoustic recording of bat echolocation call sequences to examine bat activity (relative use of an area for foraging) in hardwood forest stands subject to 4 prescribed fire and residual basal area treatments (spring prescribed fire with woodland [SpW] and savanna [SpS] residual basal areas, and fall prescribed fire with woodland [FaW] and savanna [FaS]) basal areas, as well as untreated controls, during summer of 2013 and 2014. When possible, we classified recorded echolocation call sequences to species using automated identification software (Sonobat™ 3.1.4, SonoBat™ Inc., Arcata, California). To minimize errors in species classification of recorded bat passes, we combined similar species in groups based on call characteristics prior to conducting analyses. Total bat activity ( P ⩽ 0.001), as well as LABO/NYHU (eastern red bat [ Lasiurus borealis ] and evening bat [ Nycticeius humeralis ]; P = 0.001), EPFU/LANO (big brown bat [ Eptesicus fuscus ] and silver-haired bat [ Lasionycteris noctivagans ]; P ⩽ 0.001), PESU (tricolored bat [ Perimyotis subflavus ]; P = 0.001), and LACI (hoary bat [ Lasiurus cinereus ]; P = 0.005) activity was generally higher in SpS and FaS stands, where overstory basal area was lower, than in control, SpW, and FaW stands, where overstory basal area was higher ( P ⩽ 0.001). Our results suggest these treatments reduce clutter (physical obstructions to flight and foraging including foliage, branches, and stems), leading to improved foraging conditions for bats, particularly larger bodied species with lower call frequencies that are adapted to fly and forage in open conditions. We found no evidence nocturnal flying insect prey abundance or biomass influenced activity of bats in treatment stands, indicating clutter is more important than prey availability in determining habitat use by bats in this system. Our study provides support for continued use of prescribed fire and overstory thinning to restore hardwood forest to woodland and savanna and as a strategy to maintain and enhance habitat for forest bats in the Southeastern U.S. [ABSTRACT FROM AUTHOR]