Explore the vast range of titles available.

Shifting disturbance regimes can have cascading effects on many ecosystems processes. This is particularly true when the scale of the disturbance no longer matches the regeneration strategy of the dominant vegetation. In the yellow pine and mixed conifer forests of California, over a century of fire exclusion and the warming climate are increasing the incidence and extent of stand-replacing wildfire; such changes in severity patterns are altering regeneration dynamics by dramatically increasing the distance from live tree seed sources. This has raised concerns about limitations to natural reforestation and the potential for conversion to non-forested vegetation types, which in turn has implications for shifts in many ecological processes and ecosystem services. We used a California region-wide data set with 1,848 plots across 24 wildfires in yellow pine and mixed conifer forests to build a spatially explicit habitat suitability model for forecasting postfire forest regeneration. To model the effect of seed availability, the critical initial biological filter for regeneration, we used a novel approach to predicting spatial patterns of seed availability by estimating annual seed production from existing basal area and burn severity maps. The probability of observing any conifer seedling in a 60-m² area (the field plot scale) was highly dependent on 30-yr average annual precipitation, burn severity, and seed availability. We then used this model to predict regeneration probabilities across the entire extent of a “new” fire (the 2014 King Fire), which highlights the spatial variability inherent in postfire regeneration patterns. Such forecasts of postfire regeneration patterns are of importance to land managers and conservationists interested in maintaining forest cover on the landscape. Our tool can also help anticipate shifts in ecosystem properties, supporting researchers interested in investigating questions surrounding alternative stable states, and the interaction of altered disturbance regimes and the changing climate.

PurposeWildfire spatial patterns drive ecological processes including vegetation succession and wildlife community dynamics. Such patterns may be changing due to fire suppression policies and climate change, making characterization of trends in post-fire mosaics important for understanding and managing fire-prone ecosystems.MethodsFor wildfires in California’s yellow pine and mixed-conifer forests, spatial pattern trends of two components of the post-fire severity matrix were assessed for 1984–2015: (1) unchanged or very low-severity and (2) high-severity, which represent remnant forest and stand-replacing fire, respectively. Trends were evaluated for metrics of total and proportional burned area, shape complexity, aggregation, and core area. Additionally, comparisons were made between management units where fire suppression is commonly practiced and those with a history of managing wildfire for ecological/resource benefits.ResultsUnchanged or very low-severity area per fire decreased proportionally through time, and became increasingly fragmented. High-severity area and core area increased on average across most of California, with the high-severity component also becoming simpler in shape in the Sierra Nevada. Compared to suppression units, managed wildfire units lack an increase in high-severity area, have less aggregated post-fire mosaics, and more high-severity spatial complexity.ConclusionsDocumented changes in severity patterns have cascading ecological effects including increased vegetation type conversion risk, habitat availability shifts, and remnant forest fragmentation. These changes likely benefit early-seral-associated species at the expense of mature closed-canopy forest-associated species. Managed wildfire appears to moderate some effects of fire suppression, and may help buy time for ecosystems and managers to respond to a changing climate.

The Yellow-bellied Sapsucker (Sphyrapicus varius) is a migratory woodpecker that forages for sap by drilling holes in live trees and other woody plants. Its nonbreeding range in the USA includes the diverse forests of the southern Appalachian Mountains, where the use of sap trees by sapsuckers has not been previously documented. We investigated sap tree selection by nonbreeding sapsuckers in forested areas of western North Carolina by comparing characteristics of 160 pairs of drilled and nearby (within 10 m) undrilled trees of similar stature. Results showed sapsuckers used 18 out of 24 tree species across eight study sites. We used Ivlev’s electivity index to determine whether sapsuckers exhibited taxonomic preferences based on the proportional use of tree taxa relative to their availability. Results showed neutral use of tuliptree (Liriodendron tulipifera) and maples (Acer spp.); a slight preference for eastern hemlock (Tsuga canadensis), shortleaf pine (Pinus echinata), and several deciduous hardwoods; and varying degrees of avoidance to white pine (Pinus strobus), American beech (Fagus grandifolia), and a few other taxa. Across all sites, trees drilled by sapsuckers (mean ± SD = 55.2 ± 20.2 cm) were significantly larger in diameter than undrilled trees (44.8 ± 16.6 cm), but neither crown loss nor tree type (evergreen conifer or hardwood) had a significant effect on overall tree selection. The generalist feeding strategy of nonbreeding Yellow-bellied Sapsuckers in the diverse forests of this region may buffer them from forest threats and the decline of particular tree species in the landscape.

Abstract Projections are that the area of planted stands of southern pines will exceed 50 million ac (20 million hectares) by 2060; most will be managed primarily for timber and fiber production using rotations less than three decades in length. This has been a tremendous silvicultural success. However, weighing against that success is the associated decline of native fire-adapted ecosystems dominated by longleaf pine (Pinus palustris L.) and shortleaf pine (Pinus echinata Mill.), and the flora and fauna adapted to open woodland habitats. Three elements of silvicultural practice will be needed to recover these ecosystems. First, on sites where longleaf pine or shortleaf pine no longer exist but to which they are adapted, planting will be a primary tool to re-establish those species. Second, the reintroduction of fire in stands and landscapes through prescribed burning will also be important, but will be difficult to integrate into operational management. Third, there are silvicultural opportunities in natural stands with a minor component of either longleaf pine or shortleaf pine by using reproduction cutting or thinning, prescribed burning, and release treatments to bring those species back to dominance. Efforts are under way, especially on National Forest lands, to recover longleaf and shortleaf pine ecosystems.

Increasingly detailed records of long‐term fire regime characteristics are needed to test ecological concepts and inform natural resource management and policymaking. We reconstructed and analyzed twelve 350+ yr‐long fire scar records developed from 2612 tree‐ring dated fire scars on 432 living and dead pine (Pinus pungens, Pinus rigida, Pinus resinosa, Pinus echinata) trees from across central Pennsylvania. We used multiple spatial and time series analysis methods to quantify fire regime characteristics (frequency, seasonality, percentages of trees scarred, extent) and fire–climate–human associations. Prior to the 20th‐century fire suppression, fire regimes at the majority of sites consisted of frequent, low‐to‐moderate severity, dormant season fires. Fires were often regionally synchronous when preceded by significantly dry years. Using documentary archives, we provide the first description of a “wave of fire”—an anthropogenic signal in fire frequency that progressively moved across the region. This “wave of fire” reflects a changing progression of anthropogenic fire regimes from Native American occupation and depopulation, to Euro‐American settlement, to industrialization and declining fire use up to the 20th century era of fire suppression. The wave of fire provides a new perspective on historical and modern fire regime dynamics and identifies socio‐ecological impacts since North American colonization. Because the anthropogenic wave of fire exists at sites across North America, we emphasize the need for a broader determination of its geographic prevalence and variability as such determinations could influence historical ecology interpretations and perspectives on past and future roles of humans in managing ecosystems with fire.

Data from recent assessments indicate that the annual area of wildfires burning at high severity (where most trees are killed) has increased since 1984 across much of the southwestern United States. Increasing areas of high-severity fire can occur when greater area is burned at constant proportion of high-severity fire, or when the proportion of high-severity fire within fire perimeters increases, or some combination of both. For the Sierra Nevada Forest Plan Amendment (SNFPA) area, which includes forestlands in eastern California and western Nevada, Miller et al. ( 2009a ) concluded that the proportion of area burning at high severity in mixed-conifer forests had risen over the 1984 to 2004 period. However, no statistical assessment was made of the temporal trend in high-severity fire area because the analyzed dataset was incomplete in the early years of the study period. In this update, we use satellite-derived estimates of fire severity from the three most widely distributed SNFPA forest types to examine the trend in percent high severity and high-severity fire area for all wildfires ≥80 ha that occurred during the 1984 to 2010 period. Time-series regression modeling indicates that the percentage of total high severity per year for a combination of yellow pine (ponderosa pine [ Pinus ponderosa Lawson & C. Lawson] or Jeffrey pine [ P. jeffreyi Balf.]) and mixed-conifer forests increased significantly over the 27-year period. The annual area of high-severity fire also increased significantly in yellow pine-mixed-conifer forests. The percentage of high severity in fires ≥400 ha burning in yellow pine-mixed-conifer forests was significantly higher than in fires ≥400 ha. Additionally, the number of fires ≥400 ha significantly increased over the 1950 to 2010 period. There were no significant trends in red fir ( Abies magnifica A. Murray bis) forests. These results confirm and expand our earlier published results for a shorter 21-year period.

Land use and fire exclusion have influenced ecosystems worldwide, resulting in alternative ecosystem states. Here, I provide two examples from the southeastern United States of fire-dependent open pine and pine-oak forest loss and examine dynamics of the replacement forests, given continued long-term declines in foundation longleaf (Pinus palustris) and shortleaf (Pinus echinata) pines and recent increases in commercial loblolly (Pinus taeda) and slash (Pinus elliottii var. elliottii) pines. Shortleaf pine-oak forest historically may have been dominant on about 32 to 38 million ha, a provisional estimate based on historical composition of 75% of all trees, and has decreased to about 2.5 million ha currently; shortleaf pine now is 3% of all trees in the northern province. Longleaf pine forest decreased from about 30 million ha, totaling 75% of all trees, to 1.3 million ha and 3% of all trees in contemporary forests of the southern province. The initial transition from open pine ecosystems to closed forests, primarily comprised of broadleaf species, was countered by conversion to loblolly and slash pine plantations. Loblolly pine now accounts for 37% of all trees. Loss of fire-dependent ecosystems and their foundation tree species affect associated biodiversity, or the species that succeed under fire disturbance.

Presently, structural grade cross-laminated timber (CLT) panels are manufactured for interior applications. To expand the use of CLT to exterior applications, there is a need to protect the panels from biodegrading agents such as fungi and termites. Pressure treatments are effective methods of increasing the durability of wood and wood-based products. There are limited studies on the influence of micronized copper azole (MCA) treatment on the rolling shear modulus and rolling shear strength of a commercially produced 3-ply southern yellow pine CLT panel Grade V3. It was found that MCA treatment didn’t have a significant effect on the rolling shear strength of the CLT panels, with the rolling shear strength being 2.19 and 2.31 MPa for the untreated and treated CLT panels, respectively. The bonding durability of the CLT panels had mixed results, with the control specimens measuring a significantly lower wood failure percentage (WFP) of 32% as compared to approximately 75% for the MCA treated specimen. The measured block shear strength (BSS) was approximately the same for the treated and the untreated shear block specimen except for one manufacturing group. The average delamination for the treated specimens was 11% while the average delamination for the untreated specimens was 13.2%.

Background Open pine woodlands occur throughout the southeastern United States. Thinning and prescribed fire commonly are used to establish and manage pine woodlands for multiple objectives, often including timber production and wildlife habitat. Although fire effects in loblolly and shortleaf pine woodlands have been summarized widely, the effects of fire during all seasons of the year are not well understood. We implemented 72 burns at 9 sites throughout the southeastern US, 2020–2023, to evaluate how fire treatment during the dormant, early growing-, mid-growing-, and late growing-season on a 2-year fire-return interval may affect understory composition, structure, and species diversity indices. Results Fire intensity and burn coverage were greatest in the dormant-season treatment and least in the mid-growing-season treatment. Coverage of semi-woody and woody plants in the understory was less in all treatments compared to control. However, after two fire events, coverage of semi-woody and woody understory plants increased in the dormant-season treatment and woody understory plants increased in the mid-growing-season treatment, whereas neither increased in the early- and late growing-season treatments. These results indicate growing-season fire sets-back semi-woody and woody vegetation better than dormant-season fire if intensity is adequate to top-kill the plants. Forb coverage increased following all seasons of burning, but the increase was greatest in the late growing-season treatment. Coverage of graminoids decreased in control and in the mid- and late growing-season treatments, partially because of fire timing and because understory sunlight was reduced from an average of 54% to 39% over 4 years as overstory tree crowns expanded following thinning. Percent visual obstruction was least following early growing-season fire. Understory species richness increased in all treatments as well as control. Conclusion We documented changes in plant composition and structure as related to fire seasonality and intensity after 2 fire events on a 2-year fire-return interval. All fire treatments changed understory composition, and each produced different effects that could allow managers to better meet objectives in systems dominated by Southern yellow pines. Growing-season fire offers more flexibility throughout the year to accomplish objectives, including wildlife habitat management, beyond the traditional dormant-season burn window.

The purpose of this research was to investigate the modulus of rupture (MOR) and modulus of elasticity (MOE) in the static bending of yellow pine (Pinus ponderosa Douglas ex C. Lawson) earlywood and latewood. The relationship between the properties of these wood zones and the MOR and MOE of yellow pine wood tested was determined with the methodology specified in the standards. An important element of the research was to verify the suitability of the developed method for testing the MOR and MOE of small wood samples obtained from the earlywood and latewood zone. The MOR of the earlywood was about 6% higher than the MOR of the pine wood determined using standard samples, and these differences were not statistically significant. However, the MOR of the latewood was approximately three times higher than the MOR of the pine wood determined using standard samples, and these differences were statistically significant. The MOR of the latewood was found to be 2.5 times higher than the MOR of the earlywood. The MOE of the latewood was found to be two times higher than the MOE of the earlywood. This was due to the density of particular wood zones and the dimensions of structural elements—tracheids. The maximum load (Fmax) transferred by latewood zones was four times higher than the Fmax transferred by earlywood zones. The deflection at the Fmax of the earlywood zone was 20% smaller than the deflection at the Fmax of the latewood zone.