Southern Pine Research Articles

Benefit-cost analysis of forest carbon for landowners: An illustration based on a southern pine plantation

Using a hypothetic southern pine plantation in the state of Georgia of the United States, a benefit-cost analysis of forest carbon is conducted for landowners in the voluntary carbon market. With carbon values being defined by the marginal forest growth, it is found that the inclusion of carbon into the objective function usually leads to longer rotations and higher total profits. In our baseline analysis, the rotation age increases by four years when both timber and carbon are considered. Thus, landowners can benefit from voluntary carbon trading and additional carbon can be fixed in the forests. Landowners’ decision on forest carbon is most sensitive to the discount rate and timber and carbon prices. When the discount rate is higher, future cash flows become less valuable and the optimal rotation shortens. When timber prices exceed carbon price by a large margin, timber value dominates carbon value and the optimal carbon rotation approaches the Faustmann rotation. Therefore, with a higher discount rate and higher timber prices, voluntary carbon trading will result in less carbon additionality. Finally, when the economic uncertainty is incorporated into the decision making, the results tend to be sustained albeit carbon additionality is slightly reduced.

A regional assessment of permanganate oxidizable carbon for potential use as a soil health indicator in managed pine plantations

Soil health assessments require the establishment of soil indicators that are easy to measure and sensitive to changes in management practices. Despite the global demand for wood products and the intensification of silvicultural practices, very few indicators are currently used to monitor changes in soil properties and processes in managed forest plantations. Labile pools of soil organic carbon (SOC) have been widely used in agriculture to detect early alterations in carbon (C) cycling processes but are largely untested in managed forests. Here, we investigate the potential use of permanganate oxidizable carbon (POXC) to monitor impacts of silvicultural practices on soil properties in loblolly pine plantations. Soil samples were collected from 77 managed forest sites and 297 experimental plots throughout the southeastern U.S. at four soil depths: 0–10, 10–20, 20–50, and 50–100 cm. Sites encompassed plantations with ages ranging from 2 to 29 yr that were distributed over five soil orders. Silvicultural practices included herbicide, fertilization at multiple rates, and thinning. Our study showed that POXC concentration decreases with soil depth, while POXC increased proportionally to SOC with depth. POXC positively correlates with SOC, total nitrogen, and mass of soil woody detritus other than live roots, and negatively correlates with soil pH across all soil depths. Impacts of silvicultural practices on POXC concentration were variable across sites. The mean relative response of POXC to silvicultural practices was negative in general but only significant (p < 0.10) in herbicide treatments; compared to control plots herbicide plots at 50–100 cm depth had on average 20% less POXC. The decade-long rotation lengths of southern pine plantations and the carbon cycling dynamics of forest soil O horizons may impact the sensitivity of POXC as an indicator in managed plantations. In contrast to this regional analysis, monitoring POXC in local assessments may be a more practical approach to investigate short-term impacts of silvicultural practices.

Trends in Bark Beetle Impacts in North America During a Period (2000–2020) of Rapid Environmental Change

AbstractOf the more than five hundred and fifty species of North American bark beetles (Coleoptera: Curculionidae, Scolytinae), approximately twenty species occasionally cause large amounts of tree mortality in conifer forests. During 2000–2020, trends in bark beetle impacts changed dramatically across North America compared to those observed during the mid- to late 20th century. We review tools and tactics available for bark beetle suppression and prevention and provide an overview of temporal and spatial trends in bark beetle impacts in North American forests during 2000–2020. Higher impacts were observed for several bark beetle species in western North America accompanied by substantial declines in eastern North America driven by large reductions in southern pine beetle (Dendroctonus frontalis) activity in the southeastern United States. Regional differences likely result from a higher species richness of both bark beetles and their hosts in western North America, stronger direct and indirect effects of climate change (warming and drying) on bark beetles in western North America, and differences in forest composition, management history, and other abiotic stressors and disturbances.Study ImplicationsCompared to the mid- to late 20th century, bark beetles have had increased impacts in western North America and reduced impacts in eastern North America, the latter driven by large reductions in southern pine beetle (Dendroctonus frontalis) activity in the southeastern United States. We review tools and tactics available to foresters and other natural resource managers to reduce the negative impacts of bark beetles on forests. Furthermore, we provide several potential explanations for recent trends in bark beetle impacts between eastern and western North America.

Evaluations of alternative herbicides to glyphosate for wilding pine control during forestry site preparation in the southeastern United States

AbstractControl of southern pine species that easily establish from seed, such as loblolly pine and slash pine (wilding pines), has historically been achieved economically through the use of prescribed fire or application of glyphosate or glyphosate and saflufenacil during site preparation. Currently, alternatives to glyphosate are being investigated for wilding pine control because of health and safety concerns over glyphosate reported by some organizations. Two exploratory studies in the Coastal Plain Region of Georgia investigated the potential of several herbicides for wilding pine control with 0.56 to 0.70 kg ha−1 of 0.9-kg ae imazapyr included in all herbicide treatments. Application timings for Study 1 were July and September (n = 8 treatments per timing), whereas Study 2 took place in July and early November (n = 4 treatments per timing). In Study 1, various rates of choline triclopyr, ester triclopyr, fluroxypyr, aminopyralid + florpyrauxifen-benzyl, and aminopyralid + triclopyr were tested, while two treatments contained glyphosate. Study 2 investigated mixtures containing flumioxazin, glufosinate, and triclopyr. Results for Study 1 revealed that the two treatments containing glyphosate had the greatest percent loblolly pine control after 120 d (87.5% and 88.6% control, respectively), while the next best control was offered by a treatment containing imazapyr plus 3.36 kg ha−1 choline triclopyr (52.6% control). July treatments offered better control than September treatments, but the efficacy of September treatments may have been impacted by a severe drought. In Study 2, treatments applied during early November that contained imazapyr and glufosinate or imazapyr, glufosinate, and flumioxazin resulted in 100% control of mixed loblolly and slash pine seedlings and saplings. All November treatments offered better control than July treatments in Study 2. Promising results from Study 2 suggest that glufosinate may warrant additional study for use in forestry site preparation as an alternative to glyphosate to control wilding pines.

Exploratory studies on effects of growth location and conditioning on treatability and permeability of southern pine lumber

Southern pine lumber is often treated with preservatives, but issues related to initial kiln-drying conditions and geographic source across the wide southern pine growth range have been suspected to negatively affect subsequent permeability and treatability. These effects remain poorly understood. In this series of exploratory studies, southern pine from across part of the growing range subjected to different kiln-drying regimes was evaluated in three phases exploring the effects of geographic source and initial kiln-drying conditions on permeability, pit structure and eventual preservative treatment of southern pine lumber. The results suggest that elevated temperatures coupled with poor humidity control at the start of the kiln drying process may negatively influence permeability and preservative penetration, but had only negligible effects on several other wood properties.

Southern Pine Beetle Dendroctonus frontalis (Coleoptera: Curculionidae: Scolytinae)

The southern pine beetle (SPB), Dendroctonus frontalis Zimmermann, has been the most economically important forest insect in the pine timber industry in the southern United States. From 1960 through 1990, the bark beetle caused economic losses estimated at $900 million (Price et al. 1992). From 1998 to 2002, a four-year outbreak in the southern Appalachian Mountains affected more than 1 million acres with an economic loss of more than $1 billion (Clarke and Nowak 2009). In 2001,17,599 acres of pine forest were damaged by SPB in Florida alone, causing an estimated $38 million in damages.&#x0D; While the spectacular outbreaks have captured attention, equally interesting are the long periods of the beetle absence between outbreaks, and the factors that maintain its low populations. Recent observations suggest that in natural conditions the beetle is a rare insect, and rarely responds with an outbreak unless silvicultural practices create a suitable environment: overstocked, even-aged, large pine stands. Despite many decades of research on the beetle ecology, we lack a complete understanding of its population dynamics, and its original (preindustrial) ecology remains elusive (Asaro et al. 2017). Fortunately, silvicultural practices leading to resistant stands are now commonplace, and principally include thinning (either mechanical or by fire) and rapid detection and removal of infestations (Nowak et al. 2015).

Half hole and full hole dowel embedment Strength: A review of international developments and recommendations for Australian softwoods

Embedment strength is an essential system property of the European Yield Model which is commonly used to predict the ductile capacity of timber joints using dowel-type fasteners. This paper presents a comprehensive review of international embedment test methods and prediction formulae in design codes and literature, as well as an experimental study to evaluate the impact of different test methods parallel to the grain. A total of 224 full hole (FH) tension and half hole (HH) compression tests were conducted according to AS/NZS ISO 10984.2 on Australian sawn softwoods (Radiata Pine and Southern Pine) to compare embedment strength resulting from FH specimens sized to EN 383 and HH specimens sized to ASTM D5764, respectively. The results were compared to dowel embedment strength formulae from literature, those contained in Eurocode 5, the National Design Specification (NDS) for Wood Construction, and the respective joint group strength values contained in AS 1720.1, which are based on empirical test data. It was found that all strength prediction models were non-conservative except for a formula proposed by Smith et al. in 2004, which was based on FH tension tests in Australian Radiata Pine and Slash Pine. Furthermore, a strong correlation between timber density and embedment strength was found for both test methods, however, only FH tests displayed a correlation between dowel diameter and embedment strength, which is consistent with the embedment strengths formulae currently contained in Eurocode 5 and the NDS.

Using RNAi to silence heat shock protein has congeneric effects in North America’s Dendroctonus bark beetles

Losses associated with forest pest outbreaks are increasing at an alarming rate, exacerbated by fluctuating climate patterns, and unimpeded by traditional management approaches that fail to keep pace with growing pressures. Future forest pest management strategies demand augmentation with next generation approaches. RNA interference, or RNAi, is a naturally occurring eukaryotic immune response to viral infection that works by disrupting the translation of mRNA into protein and can be manipulated to cause insect mortality through the introduction of carefully designed dsRNAs. The effective induction of the RNAi pathway depends on the exact match of a sequence at least sixteen nucleotides in length, making non-target effects unlikely. Thus, RNAi is increasingly praised as a species-specific pest management approach. The southern pine beetle (SPB), Dendroctonus frontalis, and its congener, the mountain pine beetle (MPB), D. ponderosae, are highly destructive forest pests endemic to North and Central America experiencing unprecedented range expansions, with extensive impacts on affected ecosystems. We have demonstrated that oral ingestion of specific dsRNAs induces gene silencing via RNAi and causes rapid and significant mortality in both SPB and MPB. Here we evaluate the ability of dsRNAs targeting SPB to affect gene expression in MPB, and the ability of dsRNAs targeting MPB to affect gene expression in SPB. We found that species-specific dsRNAs designed for gene silencing in one species can silence genes in the reciprocal species, offering the potential for development of RNAi as a Dendroctonus-specific management tool against rapidly expanding bark beetle populations.

An Inverse Growth Curve Representation of the Clutter-Jones Stand Survival Model

Abstract The Clutter-Jones (CJ) stand survival model has been widely used for the projection of the reduction in trees per unit area in a forest stand over time. To better understand this well-recognized model, we introduced a varying-parameter formulation as an alternative to its original difference equation form, where plot-specific effects are presented explicitly. This new parameterization turns out to be a type of Richards (generalized logistic) equation with its independent variable age log-transformed, which might be termed “log-Richards” (LR) and falls into the category of the generalized algebraic difference approach (GADA) models. Under the LR GADA representation, a half-reduction age, at which half of the trees in a stand die, may be examined to improve stand survival simulation. The new reformulation provides an inverse growth curve modeling viewpoint of stand survival over time. It may motivate one to derive new survival models directly from existing growth equations that allow for generating inverse growth curves, complementary to the commonly used differential equation method in developing stand mortality models. Study Implications: The Clutter-Jones stand survival model plays an important role in southern pine plantation management as a component of whole-stand modeling systems. This study introduces a varying-parameter formulation as an alternative to its original difference equation form, providing an inverse growth curve modeling viewpoint of stand survival over time.

Variability in Growth Patterns and Tree-Ring Formation of East European Scots Pine (Pinus sylvestris L.) Provenances to Changing Climatic Conditions in Lithuania

An increase in the mean monthly temperature in July and a lack of precipitation during the vegetation period will cause an increase in the frequency and severity of droughts during the vegetation period in Lithuania. Thus, the aim of this study was to assess the growth response to climate change of East European pine provenances in Lithuania. The research was performed based on a long-term pine provenance experiment that was established in 1975 in Lithuania. The results showed that central populations demonstrated the same or better survival and growth results compared with western populations that also included local Lithuanian provenances. Even though southern populations were characterized by the same productivity, their low survival rate suggests a negative introduction effect. Analysis of temporal variation in climate sensitivity showed a higher resistance of central and southern Scots pine provenances to the negative climatic changes, compared to the western provenances. Provenances from the central, southern and especially western locations demonstrated an increasing statistically significant negative effect of monthly temperatures in July. Additionally, provenances from western locations were more sensitive to precipitation amounts, water balance and droughts in June and July. Considering that central and southern provenances demonstrated the consistent effect of growth tolerance, the incorporation of the genetic material from the southern part of European Russia and Ukraine into local breeding programs of Scots pine might amplify positive effects of the transfer. Moreover, knowledge gaps remain regarding the growth performance of Scots pine provenances that originated from central or western European regions. Thus, Scots pine origins from Poland and the northeastern part of Germany should be included in Lithuanian provenance experiments.

4‐allylanisole as a lure adjuvant for Dendroctonus frontalis (Coleoptera: Curculionidae: Scolytinae) and two associated beetles

AbstractThe southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae), is a major pine tree killer in North and Central America. In the southeastern USA, responses by D. frontalis to its aggregation pheromone can be substantially increased by at least three host odours: the monoterpenes alpha‐ and beta‐pinene, and the phenylpropanoid 4‐allylanisole. We executed three trapping experiments to assess the influence of 4‐allylanisole release rate on aggregation behaviour of D. frontalis and to evaluate the compound as an adjuvant for the operational monitoring lure for D. frontalis. Addition of devices releasing 4‐allylanisole at any of three rates (4.8, 48, and 500 mg/day measured at mean 21°C) increased D. frontalis attraction to a pheromone lure, both in the presence and in the absence of an alpha‐pinene lure. The increase was 5‐ to 50‐fold with a positive dose response up to the highest tested release rate of 4‐allylanisole. Attraction of an associate, the black turpentine beetle, Dendroctonus terebrans (Olivier), and a major D. frontalis predator, Thanasimus dubius (F.) (Coleoptera: Cleridae), was also significantly increased by 4‐allylanisole. A device releasing 4‐allylanisole at 0.05 g/day (at mean 23°C) increased attraction of D. frontalis to the current operational monitoring lure (which uses alpha‐ and beta‐pinene as the host odour component) approximately 4‐fold, but it did not increase attraction to a lure with turpentine as the host odour component (used in a former operational monitoring lure). Additionally, we observed none of the attraction‐inhibiting effects that were previously reported for 4‐allylanisole with D. frontalis. It is possible that the addition of 4‐allylanisole to the D. frontalis lure might allow detection of beetles at lower population densities and, if so, aid in earlier detection of populations invading the northeastern USA in response to climate change. This possibility should receive further investigation.

Insect infestations and the persistence and functioning of oak-pine mixedwood forests in the mid-Atlantic region, USA.

Damage from infestations of Lymantria dispar L. in oak-dominated stands and southern pine beetle (Dendroctonus frontalis Zimmermann) in pine-dominated stands have far exceeded impacts of other disturbances in forests of the mid-Atlantic Coastal Plain over the last two decades. We used forest census data collected in undisturbed and insect-impacted stands combined with eddy covariance measurements made pre- and post-disturbance in oak-, mixed and pine-dominated stands to quantify how these infestations altered forest composition, structure and carbon dynamics in the Pinelands National Reserve of southern New Jersey. In oak-dominated stands, multi-year defoliation during L. dispar infestations resulted in > 40% mortality of oak trees and the release of pine saplings and understory vegetation, while tree mortality was minimal in mixed and pine-dominated stands. In pine-dominated stands, southern pine beetle infestations resulted in > 85% mortality of pine trees but had minimal effect on oaks in upland stands or other hardwoods in lowland stands, and only rarely infested pines in hardwood-dominated stands. Because insect-driven disturbances are both delaying and accelerating succession in stands dominated by a single genus but having less effect in mixed-composition stands, long-term disturbance dynamics are favoring the formation and persistence of uneven age oak-pine mixedwood stands. Changes in forest composition may have little impact on forest productivity and evapotranspiration; although seasonal patterns differ, with highest daily rates of net ecosystem production (NEP) during the growing season occurring in an oak-dominated stand and lowest in a pine-dominated stand, integrated annual rates of NEP are similar among oak-, mixed and pine-dominated stands. Our research documents the formation of mixedwood stands as a consequence of insect infestations in the mid-Atlantic region and suggests that managing for mixedwood stands could reduce damage to forest products and provide greater continuity in ecosystem functioning.

Field Response of Black Turpentine Beetle to Pine Resin Oxidation and Pheromone Displacement.

The black turpentine beetle, Dendroctonus terebrans, is an economically important pest of pines in the Southeastern U.S., with a high potential for invasion to other pine-rich regions. Dendroctonus terebrans attraction to an injured host tree lessens over time as the host material degrades. Likewise, kairomonal volatiles emitted from the host change as constituents of the defensive resin oxidize. Therefore we hypothesized that volatiles associated with a fresh host would be more attractive to D. terebrans than those associated with a dead or dying host. We replicated the natural oxidation process of turpentine, fractionated the distilled products to isolate the oxidized products, and deployed the complex mixtures to measure field attraction based on the amount of oxidation performed. Contrasting with previous studies, our results suggest that D. terebrans attraction is not primarily based on host tree degradation. In a second experiment incorporating Dendroctonus pheromones, we demonstrate D. terebrans has a displacement-dependent response to endo-brevicomin, a pheromone associated with the sympatric southern pine beetle, D. frontalis. This has implications not only for possible interspecific signaling, but also for the role of endo-brevicomin in D. terebrans colonization behavior. The results from this study broaden the understanding of D. terebrans chemical ecology and directly contribute to the development of an effective lure-based monitoring system that will benefit future research and management efforts. This may become important if the species is established outside its native range, as in the closely related red turpentine beetle, Dendroctonus valens, which caused mass pine tree mortality following its introduction to Asia.

Informing adaptive forest management: A hazard rating tool for southern pine beetle Dendroctonus frontalis in pitch pine barrens

Abstract Climate change is facilitating a novel range expansion of southern pine beetle (SPB) into globally rare north‐eastern pitch pine barrens. By assessing stand conditions present in SPB‐infested and uninfested pitch pine stands on Long Island, NY, USA, we developed a regionally‐calibrated hazard rating model that predicts stand‐level SPB susceptibility. The model indicates that a stand's SPB susceptibility increases with (1) increasing pitch pine basal area, (2) increasing instances of previous year SPB spots nearby, and (3) sandy soil texture. The model informs adaptation strategies to a novel pest dynamic by supporting the identification and prioritization of high hazard stands for prevention management. An alignment between treatments effective in reducing SPB vulnerability and conserving pine barrens communities indicates that pine barrens can be managed both to improve resilience to future threats and preserve historic ecological conditions.

Nanostructural Changes Correlated to Decay Resistance of Chemically Modified Wood Fibers

Reactive chemical modifications have been shown to impart decay resistance to wood. These modifications change hydroxyl availability, water uptake, surface energy, and the nanostructure of wood. Because fungal action occurs on the micro and nano scale, further investigation into the nanostructure may lead to better strategies to prevent fungal decay. The aim of this article is to introduce our findings using small angle neutron scattering (SANS) to probe the effects of chemical modifications on the nanostructure of wood fibers. Southern pine wood fiber samples were chemically modified to various weight percentage gains (WPG) using propylene oxide (PO), butylene oxide (BO), or acetic anhydride (AA). After modification, the samples were water leached for two weeks to remove any unreacted reagents, homopolymers or by-products and then the equilibrium moisture content (EMC) was determined. Laboratory soil-block-decay evaluations against the brown rot fungus Gloeophyllum trabeum were performed to determine weight loss and decay resistance of the modifications. To assist in understanding the mechanism behind fungal decay resistance, SANS was used to study samples that were fully immersed in deuterium oxide (D2O). These measurements revealed that modifying the fibers led to differences in the swollen wood nanostructure compared to unmodified wood fibers. Moreover, the modifications led to differences in the nanoscale features observed in samples that were exposed to brown rot fungal attack compared to unmodified wood fibers and solid wood blocks modified with alkylene oxides.

Trap Type Affects Catches of Bark and Woodboring Beetles in a Southern Pine Stand

AbstractIn 2012, we tested the relative efficacy of four commercial types of insect traps (panel; standard multiple-funnel; modified multiple-funnel; and sea, land, and air Malaise [SLAM]) for capturing bark and woodboring beetles (Coleoptera) in a pine stand in northcentral Georgia. All traps were baited with ethanol, α-pinene, ipsenol, and ipsdienol lures. The SLAM trap outperformed the panel trap for diversity and abundance of Cerambycidae. Mean catches of Asemum striatum (L.) in SLAM traps were greater than those in all other traps. SLAM traps caught more Acanthocinus obsoletus (LeConte) and Xylotrechus sagittatus (Germar) than standard multiple-funnel funnel and panel traps. The greatest numbers of Monochamus titillator (F.) were in SLAM and modified multiple-funnel traps. In contrast, SLAM traps were inferior to all other trap types in trapping bark beetles (Curculionidae: Scolytinae). More Dendroctonus terebrans (Olivier), Hylastes porculus Erichson, and Hylastes salebrosus Eichhoff were captured in panel traps than the other types of traps. Catches of Ips avulsus (Eichhoff), Ips calligraphus (Germar), Orthotomicus caelatus (Eichhoff), and Pityophthorus spp. were the same in panel, standard multiple-funnel, and modified multiple-funnel traps. Our data suggest that combinations of trap types should be considered in maximizing the effectiveness of detection programs for pine bark and woodboring beetles.

Durability of Thermally Modified Western Hemlock Lumber Against Wood Decay Fungi

The chemical modification of wood is gaining popularity as a treatment to increase wood durability, particularly in jurisdictions where restrictions on the use of chemical impregnation are increasing. This work measures the impact of thermal modification of western hemlock lumber durability against decay fungi. Western hemlock lumber was thermally modified using a cycle with temperatures ranging from 80 to 170°C and was cut into standard 19 mm blocks for testing according to AWPA method E10. Performance of thermally modified wood was measured against two brown rot fungi, Rhodonia placenta and Gloeophyllum trabeum and one white rot fungus, Trametes versicolor over an 8, 12, and 16-week incubation period. Unmodified western hemlock wood, untreated southern pine and copper azole-treated southern pine were included for comparison. Thermal modification resulted in a slight improvement in durability against Gloeophyllum trabeum, but not Rhodonia placenta compared to untreated western hemlock which caused 50.3 and 52.2% mass loss in thermally modified western hemlock after 16 weeks, respectively. T. versicolor caused a 21.2% mass loss after 16 weeks, but this value was not statistically different than untreated western hemlock (p = 0.46). For comparison, copper azole-treated southern pine showed only an average of 0 and 15% mass loss when exposed to G. trabeum or R. placenta for 16 weeks, respectively. Together, these data indicate that while there may be some protective effect of thermally modifying western hemlock, further development of treatment processes are needed to improve the durability of thermally modified western hemlock.

Comparative study on weathering durability property of phenol formaldehyde resin modified sweetgum and southern pine specimens

Comparative study on weathering durability property of phenol formaldehyde resin modified sweetgum and southern pine specimens

The Role of Wind and Semiochemicals in Mediating Switching Behavior in the Southern Pine Beetle (Coleoptera: Curculionidae: Scolytinae).

Aggressive bark beetles colonize and kill healthy conifers through pheromone-mediated mass aggregation. In several species, the focal point of aggregation moves progressively from mass-attacked 'focus trees' to adjacent, unattacked 'recipient trees', resulting in infestation growth. This process, termed 'switching', is hypothesized to be mediated in whole or in part by antiaggregation pheromones released by beetles as colonization intensifies on a focus tree. We tested this hypothesis with the southern pine beetle, Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae), by using a windvane apparatus that maintained an unbaited, black, cylindrical trap (surrogate for a recipient tree) continuously 4 m downwind from an identical trap baited with synthetic aggregation attractant (surrogate for a focus tree). In two of three replicated trials, addition of pheromone components with antiaggregation activity, endo-brevicomin or verbenone, to the upwind trap caused a significant but small (<15%) increase in the proportion of beetles caught in the downwind trap. In one of two trials with endo-brevicomin, this shift was associated with a significant reduction in catches in the downwind trap and an overall reduction in catches of beetles by the trap pair. This suggests that an inhibitor-induced increase in landings on the recipient relative to the focus tree may be countered by the radial effects of the inhibitor, which at sufficiently high release may reduce responses to both the focus and recipient tree. We discuss spatial factors that might govern the role of antiaggregation pheromones in stimulating infestation growth as well as additional factors that likely govern switching behavior.

Future of Winter in Northeastern North America: Climate Indicators Portray Warming and Snow Loss That Will Impact Ecosystems and Communities

Winters in northeastern North America have warmed faster than summers, with impacts on ecosystems and society. Global climate models (GCMs) indicate that winters will continue to warm and lose snow in the future, but uncertainty remains regarding the magnitude of warming. Here, we project future trends in winter indicators under lower and higher climate-warming scenarios based on emission levels across northeastern North America at a fine spatial scale (1/16°) relevant to climate-related decision making. Under both climate scenarios, winters continue to warm with coincident increases in days above freezing, decreases in days with snow cover, and fewer nights below freezing. Deep snowpacks become increasingly short-lived, decreasing from a historical baseline of 2 months of subnivium habitat to <1 month under the warmer, higher-emissions climate scenario. Warmer winter temperatures allow invasive pests such as Adelges tsugae (Hemlock Woolly Adelgid) and Dendroctonus frontalis (Southern Pine Beetle) to expand their range northward due to reduced overwinter mortality. The higher elevations remain more resilient to winter warming compared to more southerly and coastal regions. Decreases in natural snowpack and warmer temperatures point toward a need for adaptation and mitigation in the multi-million-dollar winter-recreation and forest-management economies.