Red Spruce Research Articles

Balsam Fir (Abies balsamea (L.) Mill.) Wood Quality after Defoliation by Spruce Budworm (Choristoneura fumiferana Clem.) in the Boreal Forest of Quebec, Canada

Eastern spruce budworm (Choristoneura fumiferana Clem.) is considered the most important disturbing insect in coniferous stands in eastern North America. During an outbreak, spruce budworm can cause severe defoliation in balsam fir (Abies balsamea (L.) Mill.), which can affect wood properties such as moisture content and mechanical properties. This project aimed to assess the influence of the duration of spruce budworm defoliation on the wood quality of mature balsam fir trees. To do this, we studied sapwood proportion, decay, moisture content, mechanical properties and tracheid dimensions in stands that had suffered three, four or five years of defoliation. We also compared living and dead balsam firs and evaluated the change in wood properties with time. Our results showed that dead balsam firs suffered from a loss of wood quality rapidly after their death, particularly in terms of moisture content and decay in the sapwood. Sapwood proportion was similar between living and dead trees, but the sapwood of dead trees contained more decay and had a lower moisture content than living trees. Mechanical properties and tracheid dimensions were 10% and 4% lower in dead trees than in living trees. We did not observe any major differences in wood properties between the three durations of defoliation, suggesting that wood degradation occurs before that. The study did not make it possible to determine the optimal duration of defoliation to harvest the stands.

Characteristics of Red Spruce (Picea rubens Sarg.) Encroachment at Two Central Appalachian Heathland Study Areas

During the late 19th and early 20th centuries, intensive land use nearly eliminated red spruce (Picea rubens Sarg.) throughout portions of West Virginia (WV). Red spruce has been slow to regenerate on mountaintop heathland barrens surrounding Canaan Valley, West Virginia (WV), and little is known about the nature of encroachment. Using field surveys, geospatial data, and statistical modelling, the objectives were to 1) characterize and compare red spruce encroachment at two upland heath study areas in West Virginia (Bear Rocks and Cabin Mountain), 2) characterize percent cover of major ground cover types associated with red spruce regeneration sites in order to elucidate biotic interactions, and 3) model the biophysical correlates of red spruce encroachment using geospatial data and statistical modelling. Red spruce count was similar at both study areas, but there were substantially more seedlings and saplings at Cabin Mountain. Modelling revealed a positive relationship between red spruce count and rock cover and a negative relationship between red spruce and stand distance.

The 2014 Crum Workshop: Bryophytes of the Allegheny Highlands of West Virginia

We inventoried bryophytes in Canaan Valley and Blackwater Falls State Resort Parks and in Dolly Sods Wilderness (Monongahela National Forest) during the four-day Crum Workshop. We found a total of 170 species with 140 mosses and 30 liverworts (including collections made before and after the Workshop) on Pottsville sandstone, Greenbrier limestone, and organic substrates in red spruce (Picea rubens)-northern hardwood forests and Sphagnum-dominated fens. About 84% of the species have very broad distributions (63% northern Northern Hemisphere, 21% wide - ranging to the southern Southern Hemisphere), whereas 16% are endemic to the Americas. Five state records include two circumpolar-montane species (Plagiothecium nemorale and Philonotis capillaris), two North American endemics (Brachythecium falcatum and Orthotrichum parvulum), and one globally wide species (Campylopus flexuosus). This was the second Appalachian report for the disjunctive, suboceanic, temperate moss C. flexuosus.

Not just for the birds: Spiders as natural enemies of spruce budworm (Choristoneura fumiferana, Clem.)

Abstract(1) The eastern spruce budworm (Choristoneura fumiferana, Clem.) is a native irruptive forest pest that defoliates spruce‐fir forests throughout North America's boreal zone. (2) Past studies suggest that successful spruce budworm population control requires high natural mortality from a variety of sources, including predators, especially from parasitoids and birds. While well represented in many different ecosystems, the role of generalist predatory spiders in these boreal systems remains largely unstudied. (3) To determine the identity and percentage of spiders preying upon spruce budworm, we hand‐collected spiders from balsam fir (Abies balsamea) in stands with relatively high spruce budworm densities from forests in insular Newfoundland and Labrador, Canada. (4) Using a spruce budworm‐specific TaqMan real‐time PCR assay, we successfully amplified spruce budworm DNA in 32% of collected spiders. After spider molecular barcoding, we found the web builders Grammonota angusta Dondale, Pityohyphantes (aff. subarcticus), Dictyna brevitarsa Emerton and Estrandia grandaeva (Keyserling) represented 58% of the spiders feeding on spruce budworm, and the wandering hunter Philodromus rufus Dondale represented 11.8%. (5) Our molecular approach was an effective means with which to identify recently consumed prey and natural enemies in this boreal system.

From common gardens to candidate genes: exploring local adaptation to climate in red spruce.

Local adaptation to climate is common in plant species and has been studied in a range of contexts, from improving crop yields to predicting population maladaptation to future conditions. The genomic era has brought new tools to study this process, which was historically explored through common garden experiments. In this study, we combine genomic methods and common gardens to investigate local adaptation in red spruce and identify environmental gradients and loci involved in climate adaptation. We first use climate transfer functions to estimate the impact of climate change on seedling performance in three common gardens. We then explore the use of multivariate gene-environment association methods to identify genes underlying climate adaptation, with particular attention to the implications of conducting genome scans with and without correction for neutral population structure. This integrative approach uncovered phenotypic evidence of local adaptation to climate and identified a set of putatively adaptive genes, some of which are involved in three main adaptive pathways found in other temperate and boreal coniferous species: drought tolerance, cold hardiness, and phenology. These putatively adaptive genes segregated into two 'modules' associated with different environmental gradients. This study nicely exemplifies the multivariate dimension of adaptation to climate in trees.

Determination of foliar traits in an ecologically distinct conifer species in Maine using Sentinel-2 imagery and site variables: Assessing the effect of leaf trait expression and upscaling approach on prediction accuracy

Leaf traits are expressed either as area-based content (g m−2) or mass-based concentration (mg/g or %) and subsequently scaled to canopy level using leaf area index (LAI) and foliage biomass, respectively. Despite their wide use, it remains unclear whether the two trait expressions and scaling options (by LAI or foliage biomass) yield the same prediction accuracy using multispectral remote sensing data and additional site variables. In this study, we used LAI (m2 m−2) and foliage biomass (kg) to upscale area-based content [leaf mass per area (LMA), equivalent water thickness (EWT), nitrogen (Narea) and potassium (Karea)] and mass-based concentration [leaf dry matter content (LDMC), leaf water content (LWC), Nmass, and Kmass)], respectively in two contrasting study sites (coastal vs inland) for an ecologically important yet distinct regional species (red spruce, Picea rubens Sarg.) in Maine, USA. We used partial least squares regression (PLSR) and random forest (RF) to examine the effect of these metrics on model performance and prediction accuracy at both leaf- and canopy-scales using Sentinel-2 satellite bands, vegetation indices, as well as several topographical variables and depth to water table (DWT). The best-performing models (based on cross-validated normalized root mean square error: nRMSE) were used to generate high-resolution canopy trait maps. Results demonstrated that prediction accuracies of area-based leaf traits were generally higher (R2 = 0.41–0.65, nRMSE = 0.14–0.20) than the mass-based concentration (R2 = 0.42–0.65, nRMSE = 0.15–0.25) for both sites and modelling techniques. We also observed that canopy traits upscaled by LAI yield better prediction accuracies (R2 = 0.44–0.70, nRMSE = 0.17–0.20) compared to a foliage biomass upscaling approach (R2 = 0.41–0.57, nRMSE = 0.19–0.24). Among site variables, DWT was a significant variable in modeling canopy traits and showed robust behavior across the contrasting study sites. Overall, our study highlights the importance of trait expression and how it affects foliar trait retrieval accuracy at both leaf- and canopy-scale using satellite multispectral data and site variables. These findings have implications on leaf trait modelling especially in the context of monitoring dynamics in forest health and productivity from space.

Temporal trends in CO2 emissions from Picea rubens stumps: A chronosequence approach

Understanding the forest carbon cycle has become increasingly important as carbon dioxide (CO2) emissions contribute to the changing climate. Decomposition is a major component of the forest carbon cycle; however, aspects of wood decomposition remain poorly understood, especially for stumps. To fill this knowledge gap, we examined the change in CO2 emissions over time from Picea rubens Sarg. (red spruce) stumps using a 32-year chronosequence (i.e., 0, 2, 4, 8, 23, and 32 years since harvest) derived from detailed harvesting records in a northern conifer forest in central Maine, USA, that has experienced repeated partial harvests. We found low initial CO2 flux (3.2 μmol CO2 m−2 s−1 at year 0) followed by a rapid increase, peaking 8 years post-harvest (24.3 μmol CO2 m−2 s−1) followed in turn by a decrease to very low rates by years 23 and 32 (1.4 and 1.7 μmol CO2 m−2 s−1, respectively). We found no clear relationship between CO2 emissions and any of the environmental or stump variables tested (wood temperature, wood moisture, soil moisture, and/or stump volume), suggesting that time since harvest was the overriding influence on CO2 flux rates. The large variability in CO2 flux rates among stumps of the same time since harvest points to the need for future research that includes larger sample sizes and covers a wider range of environmental and stump variables to better capture potential sources of variation. Our results add to the growing body of research on carbon emissions from deadwood that can inform forest carbon-cycle models. In addition, forest managers, who are increasingly interested in carbon management, can use these results to assess harvesting impacts on forest carbon emissions.

Canopy gaps facilitate upslope shifts in montane conifers but not in temperate deciduous trees in the Northeastern United States

AbstractMany montane tree species are expected to migrate upslope as climate warms, but it is not clear if forest canopy gaps, which can facilitate tree seedling recruitment, serve as an important mechanism driving tree species range shifts. Patterns of tree seedling establishment can inform us about early stages of tree species migrations and are critical to examine in the context of global climate change.We contrasted elevational distributions of tree seedlings both within and outside of forest canopy gaps with the distributions of conspecific adults and saplings across the deciduous‐coniferous ecotone on ten mountains in four states of the Northeastern United States. We tested if seedling distributions of four dominant tree species (Abies balsamea,Picea rubens,Acer saccharumandFagus grandifolia) were shifted upslope of conspecific adult and sapling distributions. We also examined if this shift was facilitated by canopy gaps and what environmental drivers affected species distributions.There was limited seedling recruitment of dominant tree species at the temperate‐coniferous ecotone, which we attributed to (i) an observed downslope shift of seedling distributions of the low‐elevation deciduous species (Acer saccharum,Fagus grandifolia) and (ii) an upslope shift in seedling distributions of the high‐elevation conifers (Abies balsamea,Picea rubens). The upslope shift of conifer seedlings contrasts with our previous research at these sites which observed downslope shifts of sapling distributions inPicea rubens, suggesting that seedlings may be responding to more recent climate warming. Canopy gaps in high‐elevation conifer forests facilitated these upslope shifts by promoting conifer seedling recruitment. However, gaps at lower elevations did not play a significant role in seedling recruitment or the observed downslope shifts of the dominant deciduous species. Climate was the dominant predictor of adult tree distributions whereas both climate and soil were important predictors of seedling distributions.Synthesis.Our study illustrates that tree seedlings have the potential for monitoring the early stages of tree species migrations, and particularly so in canopy gaps in high‐elevation conifer forests. Further, we stress that species range shifts are sensitive to local scale heterogeneity in light availability (i.e. canopy gaps) and other non‐climatic factors.

Structural characteristics of black spruce (Picea mariana) infested with eastern spruce dwarf mistletoe (Arceuthobium pusillum), Minnesota, USA

Disturbances are important processes within forested ecosystems, influencing stand dynamics, species composition, and ecosystem services, with effects across multiple spatial scales. Interacting effects across scales can influence the suitability and results of management actions, necessitating a thorough understanding of disturbances at multiple scales. Eastern spruce dwarf mistletoe (Arceuthobium pusillum Peck, hereafter ESDM) is a native disturbance agent of lowland black spruce (Picea marina (Mill.) B.S.P.) in Minnesota, USA. ESDM results in mortality at the individual tree scale but is commonly managed through stand-level silvicultural treatments; ESDM can also influence landscape-scale forest composition. Despite its role as a mortality agent of black spruce, little is known about the relationship between structure and infestation at scales finer than the stand. Here, our objective was to quantify the relationship between ESDM infestation and structure at the stand, plot, and neighborhood scales. Twenty-five black spruce stands, 12 infested and 13 uninfested, were sampled using fixed radius plots; variables collected relate to ESDM infestation severity, forest structure, and forest composition. The relationship between forest structure and ESDM infestation presence was analyzed at the stand, plot, individual tree, and neighborhood (a hybrid scale focused on individual trees but including variables measured in the plot in which the tree is located) scales. Infested plots and neighborhoods had significantly lower trees per hectare and higher species richness and Shannon’s Diversity than uninfested plots and neighborhoods; these differences were not significant the stand scale. At the stand scale, stand structure and composition variables, including trees per hectare and species diversity metrics, shift with ESDM severity. However, at the tree level, the presence or absence of ESDM is more strongly related to structure than is severity.. When incorporating ESDM infestations in management planning and decision making, considering the appropriate scale is important. By documenting the effects of ESDM at multiple scales, we can deepen our understanding of stand dynamics and succession in lowland black spruce and use this information to develop new, ecologically based management approaches in these forests that more closely reflect the local disturbance regimes.

Differentiating between distribution and suitable habitat in ecological niche models: A red spruce (Picea rubens) case study

Ecological niche modeling has become common practice amongst ecologists in the last two decades. The terms in the field of ecological niche modeling, such as ecological niche model, species distribution model, and habitat suitability model are often used interchangeably, although each term can have very different meanings depending on the context of the study. Without full understanding of model inputs and careful interpretation of model outputs, there is a possibility that the dimension of the ecological niche being predicted does not align with the modeling goals of the author. This study showcases an example which indicates that it is possible to intentionally model species distribution and habitat suitability separately. Red spruce (Picea rubens) distribution was modeled by collecting true-absence points in proximity to red spruce presence points. Red spruce suitable habitat was modeled by excluding true-absence points and only using pseudo-absence points along with presence points. Models which included presence-proximal true-absences had functionally greater discriminatory ability in map projections and were more sensitive to subtle environmental changes when compared to models which only included pseudo-absence points. Therefore, models which included true-absence points more closely approximated the current distribution of red spruce whereas models which only included pseudo-absences more closely approximated the potential distribution within the realized niche or suitable habitat of red spruce. This study demonstrates that distribution and suitable habitat can and should be modeled separately and emphasizes the necessity of carefully considering modeling objectives and methodologies when interpreting modeling outcomes.

Seasonal Activity Patterns of Bats in High-Elevation Conifer Sky Islands

In the southern Appalachian Mountains of the southeastern USA, bat communities in high-elevation habitats tend to be relatively under-surveyed. High-elevation habitats may provide important habitat to certain species (i.e., migratory tree bats), and may serve as climate refugia during droughts or high temperatures. We conducted an opportunistic acoustic survey of bat communities in ten survey areas in high elevation (1,585–1,920 m a.s.l.) montane Picea rubens (red spruce)-Abies fraseri (Fraser fir) forest in the southern Appalachian Mountains of western North Carolina. In each survey area, we randomly placed three full spectrum acoustic detectors (N = 30) during three seasons (spring, summer and fall) in 2015. We deployed each detector for two five-day periods during each season (n = 900 survey nights). Although we detected seven bat species/groups during the surveys, 73% of echolocation files were attributed to Lasiurus cinereus (hoary bat) and Lasionycteris noctivagans (silver-haired bat). Generally rare in the Appalachians and typically present only at low densities in the summer at mid- and low-elevations, both species were detected at all sites during all seasons. Overall, mean nightly activity of bats was higher in the summer than the spring or fall. We observed 3.7–5 times greater activity of L. cinereus in spruce-fir forests during the summer compared to spring and fall, whereas L. noctivagans had 1.3–5 times more activity in the summer compared to other seasons. After accounting for precipitation events, our finite mixture models showed that season, temperature, elevation, and canopy height influenced L. cinereus activity, whereas season and temperature affected L. noctivagans activity. Our observations suggest that high-elevation spruce-fir forests are providing summer foraging and possibly day-roosting habitat of tree bats not previously documented this far south in North America.

How do advance regeneration and planted seedlings of Thuja occidentalis and Picea rubens acclimate under a first irregular shelterwood cut?

Eastern white cedar ( Thuja occidentalis) and red spruce ( Picea rubens) contribute to the biodiversity and resilience of mixedwood forests. However, cuts that remove most or all the forest cover can cause the decline of these species. Among partial cutting options, the irregular shelterwood system (ISS) can create successful conditions for the development of advance regeneration and enrichment planting. We studied 6 years of ecophysiology of lower advance regeneration and planted seedlings of eastern white cedar and red spruce growing under a first ISS cut according to three cutting intensities: light cut (35% removal, 20 m2·ha−1 residual basal area), moderate cut (42%, 18 m2·ha−1), and heavy cut (52%, 15 m2·ha−1). Light-saturated photosynthesis and height growth of planted cedar and both spruce types decreased with increasing cutting intensity, in response to an increase in competing vegetation. Therefore, to limit the negative impact of competing species on cedar and spruce regeneration, we recommend protecting tall advance regeneration (2 m+) during partial cut operations and using large-sized containerized seedlings (40–50 cm height) for enrichment planting. Results also suggest that a mechanical release could help optimize the physio-morphology and growth of both regeneration types of cedar and red spruce.

Crushed mussel shell powder and optional borax in surface char layers to protect four wood species against fire

The goal is to protect semi-finished/finished wood components from burning/fires in a variety of settings (wooden buildings, historical sites, restoration, etc.). Natural (organic) sea mussel shells (Chamelea gallina) were crushed and prepared with water in various solution concentrations (10%, 15%) after the pyrolysis process, either alone or together with boron compounds (borax). The limiting oxygen index value (LOI) was determined by making retention calculations. Coatings were applied to the wood as a double treatment, with boron compounds (borax) used for comparison purposes. Eastern spruce (Picea orientalis (L.) Link.), Anatolian chestnut (Castanea sativa Mill.), eastern beech (Fagus orientalis Lipsky), and locust (Robinia pseudoacacia) were chosen for this research. When the pyrolysis-treated impregnated samples were compared to the pyrolysis-treated control sample, the limiting oxygen index value (LOI) was found to be significantly higher in the impregnated samples. After impregnation, 15% borax (0.89%) in acacia wood had the highest retention value, whereas 10 percent mussel shell (0.22%) in spruce wood had the lowest. The maximum limiting oxygen index value (LOI) was found in acacia wood (42.8%), while the lowest value was found in acacia wood (28.9%) impregnated with 10% mussel shell powder after the pyrolysis process.

Sapling growth dynamics after partial cutting in temperate mixedwood stands

The temperate mixedwood forests of eastern North America have been managed by partial cutting for several decades. To ensure that regeneration contributes to replacing the commercial-size stems that are removed by partial cutting, forest managers need to anticipate how saplings (i.e., regenerating trees with a diameter at breast height >1.0 cm) develop in terms of number and diameter. Using up to 20 years of monitoring data from three study sites, we developed a transition matrix model to predict the future number of saplings and their diameter distribution for mixed yellow birch ( Betula alleghaniensis Britton) – conifer stands. Our results show that partial cutting allowed yellow birch, red maple ( Acer rubrum L.), red spruce ( Picea rubens Sarg.), and balsam fir ( Abies balsamea (L.) Mill.) saplings to reach merchantable size faster and in greater numbers than in untreated control plots. We also found that fewer hardwood saplings (yellow birch and red maple) than softwood saplings (red spruce and balsam fir) were required to produce 1 m2·ha−1 of merchantable basal area after 20–40 years. Finally, our model provides a tool for forest managers to predict sapling development in mixed hardwood and softwood stands over a full cutting cycle.

Effects of whole-tree and stem-only clearcutting on forest floor and soil carbon and nutrients in a balsam fir (Abies balsamea (L.) Mill.) and red spruce (Picea rubens Sarg.) dominated ecosystem

Intensive harvesting of forest biomass for bioenergy has the potential to degrade forest soils and productivity if ecosystem carbon and other nutrients are depleted faster than replenished naturally or by management inputs. Climate change mitigation potential associated with bioenergy may be threatened if forest management operations reduce soil carbon stocks. Research reported here was initiated in 1979 to determine the effects of whole-tree harvesting on long-term site productivity and ecosystem carbon and nutrient pools and fluxes in a northeastern North American temperate balsam fir-red spruce forest. A sequence of harvesting and silvicultural treatments were applied from 1981 to 1993 using a paired-watershed experimental design. Treatments included whole-tree clearcutting, stem-only harvesting, simulated by return of chipped or lopped delimbing residue, conifer release by applying herbicide, and pre-commercial thinning and fertilizer application. Quantitative samples of the forest floor were excavated in 2016. Quantitative soil pits were sampled in 2017 to a depth of 50 cm below the forest floor, where possible; the basal till subsoil was sampled to a depth of 100 cm with an auger. Forest floor samples were analyzed for total carbon, nitrogen, phosphorus, potassium, calcium, magnesium and aluminum. Organic and mineral soil layer samples from the quantitative pits were analyzed for pH, short and long-lived soil carbon via 13C cross polarization magic angle spinning (CP-MAS) nuclear magnetic resonance (NMR), total carbon and nitrogen and extractable phosphorus, potassium, calcium, magnesium and aluminum. Forest floor carbon and nitrogen on whole-tree harvested plots 35 years after harvest were about 50% of the amount on the unharvested watershed. Stem-only harvesting partially mitigated the reduction, and gross losses were apparently offset by increases in the mineral soil solum to depth 50 cm, suggesting that downward translocation of soil organic matter was a significant ecosystem process during the 35 years since harvest. Accumulated forest floor and mineral soil stock of total carbon and nitrogen and extractable nutrients to depth 100 cm did not differ significantly between the harvested and unharvested watershed. A corresponding similarity in mineral soil pools of extractable phosphorus and non-acid cations in the two watersheds suggests that inputs from atmospheric deposition, primary and secondary mineral weathering, organic matter mineralization and litterfall balanced exports including leaching and plant uptake. Ecosystem stocks of extractable phosphorus, base cations, and total organic carbon and nitrogen were maintained 35 years after whole-tree harvesting of a primary spruce-fir forest.

Conservation planning integrating natural disturbances: Estimating minimum reserve sizes for an insect disturbance in the boreal forest of eastern Canada.

Large natural disturbances such as insect outbreaks and fire are important processes for biodiversity in forest landscapes. However, few methods exist for incorporating natural disturbances into conservation planning. Intact forest landscapes, such as in the North American boreal forest, can produce large natural disturbance footprints. They also have the potential to support large reserves but size estimates based on natural disturbance are needed to guide reserve design. Historical fire data have been used to estimate minimum dynamic reserves, reserve size estimates based on maintaining natural disturbance dynamics and ensuring resilience to large natural disturbance events. While this has been a significant step towards incorporating natural disturbance into reserve design, managers currently lack guidance on how to apply these concepts in areas where fire is not the dominant natural disturbance. We generalize the minimum dynamic reserve framework to accommodate insect outbreaks and demonstrate the framework in a case study for eastern spruce budworm (Choristoneura fumiferana) in the Canadian boreal forest. Our methods use geospatial analysis to identify minimum dynamic reserves based on a set of spatially explicit initial conditions, and simulation models to test for the maintenance of a set of dynamic conditions over time. We found considerable variability in minimum dynamic reserve size depending on the size of historic budworm disturbance events and the spatial patterns of disturbance-prone vegetation types. The minimum dynamic reserve framework provides an approach for incorporating wide-ranging natural disturbances into biodiversity conservation plans for both pro-active planning in intact landscapes, and reactive planning in more developed regions.

Gaining Insights about Forest Health Prescriptions from Loggers and Foresters: Understudied Voices in the Human Dimensions of Forest Health.

Maintaining healthy forests requires multiple individuals, including foresters who develop timber sale silvicultural prescriptions and loggers who implement those prescriptions, resulting in the transplantation of forest health science into workable management plans. However, data on the experiences, attitudes, and opinions of these two groups are often missing when developing or refining forest health treatment strategies. To explore the role that these groups play in sustaining forest health, we examined timber sale administrators' and loggers' perspectives on treatment approaches for eastern spruce dwarf mistletoe (Arceuthobium pusillum) (ESDM), a parasitic plant native to Minnesota that increases mortality and reduces growth rate and regeneration success of black spruce (Picea mariana). While ESDM has been managed for decades in black spruce stands in Minnesota, little is known about the effectiveness of the management approaches. Data were gathered through interviews and focus groups with loggers, as well as an online survey and focus groups with foresters who administer timber sales. Study participants identified a range of field-based barriers, knowledge gaps, and uncertainties that hamper the ability to effectively implement ESDM treatment strategies as designed, including financial, administrative, informational, policy-related, and environmental factors. These factors have a significant bearing on the ability to effectively implement ESDM treatment approaches; yet may be factors that were not known or considered when developing treatment strategies. This case study underscores the value of nurturing a science-management partnership to ensure that a broad set of voices are considered when developing or revising forest health treatment strategies.

Antimicrobial diterpene induced by two gall-inducing adelgids coexisting on Picea koraiensis.

The mechanism by which closely related species can coexist is a central factor in the stability of ecological communities. The larch adelgid (Adelges laricis laricis) and the eastern spruce adelgid (Adelges (Sacchiphantes) abietis) have both been found on the branches of Picea koraiensis in China. These two adelgids exhibit strong infectivity and readily induce the formation of 'fish scale-like' and 'pineapple-like' galls with branch parasitism rates of between 75.01±7.03 and 88.02±4.39%. Interestingly, the gall tissues in which these two gall-inducing insects were found to be coexisting were discovered at a rate of ~0.2% in the studied populations. The weight and number of gall chambers as well as the number of adelgids in the 'fish scale-like' side were higher than those in the 'pineapple-like' side. Furthermore, compared with the normal branches, a diterpene neoabietic acid was found at elevated concentrations in the gall tissues, with especially high concentrations seen in the tissues of the co-occupied galls. Neoabietic acid exhibited strong antibacterial activities against Bacillus spp. isolated from the branches of P. koraiensis, as well as potent antifungal activity against the hyphal growth of Fusarium graminearum JMY-1, which was obtained from the gall tissues. Our result provides evidence that the coexistence of the two closely related species could be explained by alterations of the host tissues by the insects resulting in increased concentrations of the antimicrobial agent.

Estimating tree Diameter at Breast Height (DBH) using an iPad Pro LiDAR sensor

ABSTRACT Diameter at Breast Height (DBH) plays an important role in forest management. New technologies such as airborne and terrestrial Light Detection and Ranging (LiDAR) are expensive and time-consuming. We explored the iPad LiDAR sensor to measure DBH considering affordability and availability. The study was carried out at a research forest plantation near Thunder Bay, Ontario, Canada. Five plots were selected for differences in stem spacing, average DBH and species, and made 360° scans separately. A manual circle fitting method was used to produce circular features for the estimation of DBH. The coefficient of determination (R 2) between estimated DBH and field measurements was 0.52, indicating a moderate accuracy. The Root Mean Square Error (RMSE) of DBH estimation ranged from 2.82 cm to 8.24 cm. The accuracy of smaller red pine trees was found to be relatively higher than that of larger red pine and white spruce trees. These accuracies did not change with the distance from the scanning location to trees. Therefore, results showed the potential use of an iPad LiDAR Scanner for DBH estimation. We recommend developing an application combining the iPad’s location and LiDAR sensors and incorporating a precise positioning method for fieldwork, and further broad field testing.

Integrating historical observations alters projections of eastern North American spruce–fir habitat under climate change

AbstractSpruce–fir (Picea–Abies) forests of the North American Acadian Forest Region are at risk of disappearing from the northeastern United States and Canada due to climate change. Species distribution models (SDMs) have been used to predict changes in this critical transitional ecosystem in the past, but none have addressed how seasonal patterns of temperature and precipitation interact to influence tree species abundance. Inferences have also been limited by contemporary inventory data that could not fully characterize species ranges because they either, (1) only sampled species occurrence after large‐scale human disturbance and settlement, or (2) did not span critical geopolitical boundaries (e.g., the US–Canadian border) that intersect the focal species' range(s). Here, we built new SDM models to better assess the bioclimatic distribution of four spruce–fir species and to test the importance of seasonal climate interactions. We compiled an extensive database of tree occurrence and abundance from recent (~1955–2012) and historical time periods (1623–1869) to model current species distributions and to predict how these might change under future climate. We found that including historical tree data in our SDMs revealed previously unrecognized suitable habitat along the southern edge of species' contemporary ranges. Random forest models predicted occurrence with high accuracy (area under receiver operator curve >0.98), and the seasonal climate variables that emerged as most important for these cold‐adapted species all included interactions that reflected sensitivity to colder temperatures, and preferences for wet weather concentrated in the winter months. Under moderate climate warming (representative concentration pathway 6.0), the northeastern United States retained additional suitable habitat when historical data were included through 2060 for three of the four species: red spruce (Picea rubens), black spruce (Picea mariana), and balsam fir (Abies balsamea), while white spruce (Picea glauca) habitat contracted into Canada. In contrast, future predictions from models that used contemporary data alone forecast extirpation for all four species from the northeastern United States. Overall, these findings highlight that prediction of species ranges in transitional ecosystems that span geopolitical boundaries and gradients of intense land use are improved when historical data and seasonal climate interactions of both temperature and precipitation variables are incorporated.