Land use by Indigenous people (Native Americans) and climate are primary factors affecting the dynamics of oak (Quercus) forests and woodlands in the eastern United States. Prior to Euro-American settlement, much of the eastern deciduous forest was dominated by oak species. The role of periodic surface burning, agriculture, and other forms of land management by Indigenous peoples is frequently noted by cultural anthropologists and historical ecologists. However, these points are often debated by paleoecologists and climate scientists. Here we present a literature review, synthesis, and data summary to investigate the role of altered land use, season of burning, and climate change in relation to pre– and post–Euro-American changes in forest composition. Human-based ignitions, as reflected by dormant-season fires, prevailed over the oak- and pine-dominated forests, with intermediate fire frequency during Indigenous periods. From the 18th century on, Euro-American populations rapidly expanded, impacting much of the eastern United States through extensive timber harvesting, land clearing, and severe fires. Starting in the 20th century, a variety of ecological influences, including agricultural land abandonment, chestnut blight, fire suppression, mesophication, and urbanization, resulted in dramatic vegetation changes in eastern landscapes. These trends have culminated in recruitment failures of most oak species on all but the most xeric sites and an increase in mid- to late-successional mesic hardwoods, most notably red maple (Acer rubrum), a species with very low density in our analysis of the witness tree record. We conclude that prescribed burning, agriculture, and other land uses by Indigenous peoples created a mosaicked landscape of expansive oak savannas, woodlands, and forests. A warming world over the past century should have promoted warm-adapted, fire-tolerant, xerophytic genera such as oak, hickory (Carya), and pine (Pinus) and grassland communities but instead have promoted the invasion by cool-adapted, fire-sensitive, mesophytic trees due to the absence of burning, much to the detriment of major vegetation biomes. Understanding that eastern oak and other pyrogenic ecosystems represent an Indigenous landscape strengthens our ability to best manage vegetation against the expansion of less desirable species and restore historic fire cycles through prescribed burning.

Thinning and prescribed fire are often used to promote oak recruitment into the canopy; however, little is known about the longevity of resprouting oak seedlings and how age affects growth response to these treatments. We investigated this by excavating 180 chinkapin oak seedlings (Quercus muehlenbergii) from an eastern Kansas upland hardwood forest study area divided into different combinations of burning and thinning treatments: control, burn only, burn and thin to 7 m²/ha, burn and thin to 14 m²/ha, thin to 7 m²/ha, and thin to 14 m²/ha. In each treatment, approximately three years post-treatment, we aged the seedlings at the root collar (“root age”) and the base of the current aboveground shoot using tissue staining and microscopy techniques. Annual shoot growth rate was calculated for each individual based on the age of the shoot and its total height. We compared these shoot growth rates in height across treatments and investigated this relationship as a function of plant age using the root age. The oldest root age was 48 yr, and 20% of the roots were ≥ 18 yr. Mean root age of advance reproduction was 11.8 years, while mean age of associated aboveground stems was 4.1 yr, with the oldest age structure belonging to treatments without any burn with the control being the oldest. The majority (90%) of the mismatch between root and shoot age was associated with burn treatments. Root age had a strong positive correlation with shoot growth rate in the burn + thinning treatments and also the untreated control, suggesting that age becomes an influence on growth when resprouting under adequate light conditions but also when individuals experience low competition. Further determination of root age structures, such as along gradients of site productivity, would likely aid in further understanding regeneration dynamics and management for sustaining oaks.

The Tension Zone (TZ) is a prominent Midwestern ecotone where the flora of two major forest types (Northern Mixed Forests and Southern Broadleaf Forests) commingle, striking diagonally across the states of Wisconsin and Minnesota. Here, we evaluated the TZ's original placement as demarcated by previous scholars relative to the synecological and autecological characteristics of witness trees from US Public Land Survey records. Witness trees were categorized by temperature and fire relations, point data analyzed in GIS, and spatial outputs compared with the original TZ. Our temperature-based line, representing temperature relations of witness trees, generally corresponded with the original TZ. However, in the lee of firebreaks, isolated pockets of cool/cold mesophytic genera occurred south of the TZ, indicating that other environmental factors were involved in TZ expression. A pyrogenic-based line, created by classifying witness trees by fire relations, had two major northward departures from the original TZ where cold-adapted yet pyrophilic northern pines occurred on sandy glacial deposits. Fire was found to play a contributing role, being pervasive south of the TZ, whereas edaphically restricted to dry, sandy landscapes to the north. Climate change and fire suppression will exert future “tension” on the line, forcing uncertain movement across the landscape from these two divergent forces, with projected higher future temperatures pushing the TZ northward and fire suppression and accompanying mesophication (comprised of primarily cool/cold–based trees) pulling the TZ southward. An endpoint to the temperate-based Midwestern TZ was identified in northwest Minnesota, converting over to a Boreal-Prairie TZ northward.

We used historical and contemporary survey data to assess the dynamics in two old-growth forests at Savage Mountain, Maryland, versus secondary forests from the surrounding landscape of the northern Allegheny Mountain Plateau (AMP). This is the first published compilation of witness trees from western Maryland. The old-growth forests on Savage Mountain, Maryland, are presently dominated by mixed oak (Quercus spp. L.; 42%), red maple (Acer rubrum L.), and black birch (Betula lenta L.). Witness trees (1620–1825) from Savage Mountain were dominated by mixed oak (55%), hickory (Carya spp.; 18%), and chestnut (Castanea dentata (Marsh.) Borkh.; 10%), and lacked red maple and black birch. The witness trees of the AMP in Pennsylvania were dominated by mixed oak (41%), pine (Pinus spp. L.; 12%), maple (11%), chestnut (10%), and hickory (6%). Currently the AMP is dominated by mixed oak (25%), red maple (25%), and black cherry (Prunus serotina Ehrh.; 11%). The old-growth stands on Savage Mountain are similar to its witness trees in regard to oak species and have greater oak dominance than the AMP secondary forests. This suggests that old-growth retains more oak compared with cut-over forests. However, old-growth on Savage Mountain has a higher density of red maple and black birch when compared to the AMP. Our research illustrates differences in forest dynamics and oak dominance between old-growth and second-growth forests that have important implications for the sustainability of native forests.

We reconstructed historical fire regime characteristics at the Bridgestone Nature Reserve at Chestnut Mountain using tree-ring dated fire scars on live and dead shortleaf pine (Pinus echinata Mill.) trees. Fire-scar records described the historical fire frequency and seasonality from the mid-18th century to present. Overall, we found historical fires occurred relatively frequently, predominantly in the dormant season, and were likely low-severity events. Mean fire intervals (MFIs) were slightly longer in the pre-Euro-American period (1744–1834; MFI = 9.6 yrs) versus the post-Euro-American period (1834–1935; MFI = 5.6 yrs). No fires were recorded after 1940, which in combination with past logging and land uses, is likely a major contributor to the ongoing decline of shortleaf pine and pyrophytic oak species observed here. Surprisingly, the majority of fire event years after 1834 were also recorded at Savage Gulf State Natural Area (52 km to the south), raising questions about potential historical fire sizes, patterns, and driving factors across the Cumberland Plateau landscape. In a landscape where fire-scarred remnants are present but relatively scarce and rapidly disappearing, these data are important for evidencing historical fire regimes and developing a more comprehensive regional network of fire history sites that could reveal valuable historical ecological information for the Cumberland Plateau.

Oaks (Quercus spp.) are foundational species in forests and woodlands in the eastern USA. An oak regeneration bottleneck has occurred throughout its range in recent decades, and refining silvicultural treatments to localized conditions has become a focus in addressing this problem. This study was developed to determine species regeneration dynamics among oak and oak competitors on productive sites in response to silvicultural treatments in oak-dominated southern Appalachian mountain forests. The treatments were: an oak shelterwood treatment (25–30% basal area [BA]) reduction through midstory removal with herbicides); a prescribed fire treatment (two, late-dormant season prescribed fires occurring over a 9-yr period); a shelterwood and burn treatment (one, late-dormant season prescribed fire 3–5 yr following 30–40% BA removal); and an unmanaged control. To determine treatment impacts on the regeneration layer, changes in relative and absolute importance values and stems ha-¹ (germinants up to stems ≤ 4.9 cm diameter at breast height [DBH]) were calculated at the species group and individual species level 0 and 9 yr postinitial treatment. The greatest relative increases in importance values were 1,401% and 2,995% for the red oak group and yellow-poplar (Liriodendron tulipifera), respectively, in the shelterwood and burn (SWB). Changes in all species groups were predominantly influenced by the smallest size-class (< 0.6 m tall), with the exception of northern red oak (Q. rubra) and yellow-poplar in the SWB. The SWB significantly reduced importance values of all shade-tolerant species groups and was the only treatment to decrease red maple (Acer rubrum) importance value and density over the study duration. The prescribed fire (RXF) treatment increased the red oak group importance value, while simultaneously decreasing yellow-poplar's importance value and increasing red maple's importance value. Changes in the red oak group in the SWB and the RXF were driven by northern red oak. Treatments did not significantly change the importance value of the white oak group. The SWB was the only treatment to significantly decrease overstory BA. The RXF and SWB treatments improved the competitive status of only some oak species, but modifications to these treatments might result in better control of yellow-poplar and red maple competition, further improving oak's competitive status. Although the SWB resulted in modest recruitment of northern red oak saplings, all treatments appear in need of additional follow-up vegetation control to further improve the competitiveness and recruitment of oak into large size-classes.