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Composition of pyrolysis gases for wildland fuels is often determined using ground samples heated in non-oxidising environments. Results are applied to wildland fires where fuels change spatially and temporally, resulting in variable fire behaviour with variable heating. Though historically used, applicability of traditional pyrolysis results to the wildland fire setting is unknown. Pyrolytic and flaming combustion gases measured in wind tunnel fires and prescribed burns were compared using compositional data techniques. CO2 was dominant in both. Other dominant gases included CO, H2 and CH4. Relative amounts of CO, CO2 and CH4 were similar between fire phases (pyrolysis, flaming combustion); relatively more H2 was observed in pyrolysis samples. All gas log-ratios with CO2 in pyrolysis samples were larger than in flaming combustion samples. Presence of live plants significantly affected gas composition. A logistic regression model correctly classified 76% of the wind tunnel samples as pyrolysis or flaming combustion based on gas composition. The model predicted 60% of the field samples originated from pyrolysis. Fire location (wind tunnel, field) and fire phase affected gas composition. The compositional approach enabled analysis and modelling of gas compositions, producing results consistent with the basic characteristics of the data.

Background Traits of mature trees, such as bark thickness and texture, have been documented to promote resistance or resilience to heating in fire-prone forests. These traits often assist managers as they plan and promote prescribed fire management to accomplish specific land management objectives. Species are often grouped together as pyrophobes or pyrophytes as a result of these features. Nonetheless, little is known about species-specific traits of other structures, such as bud diameter, length, mass, moisture content, and surface area, that might be related to heat tolerance. Many prescribed fires are utilized in the eastern United States to control regeneration of less desired species, which could apply a more mechanistic understanding of energy doses that result in topkilling mid-story stems. In this study, we investigated potential relationships between terminal bud mortality from lateral branches of midstory stems and species-specific bud features of six eastern US deciduous trees. Characterized at maturity as either pyrophytes or pyrophobes, each was exposed to different heat dosages in a laboratory setting. Results Bud diameter, length, mass, moisture content, and surface area differed by species. Bud percent mortality at the first heat flux density (0.255–0.891MJm−2) was highest for two pyrophobes, chestnut oak (Quercus montana Willd.) and scarlet oak (Quercus coccinea Münchh). For the second heat flux density (1.275–1.485MJm−2), bud percent mortality was highest for these species and red maple (Acer rubrum L.). Principal component analysis suggested that bud surface area and length differentiated species. Red maple, chestnut oak, and scarlet oak produced clusters of buds, which may explain their more pronounced bud mortality. Yellow-poplar (Liriodendron tulipifera L.) was also present in that cluster, suggesting that its unique bud architecture of pre-emergent leaves may have elicited responses most similar to those of the clustered buds. Conclusions Contrary to expectations, lateral buds of species regarded as pyrophytes at maturity displayed some of the highest values of bud percent mortality when heated at two heat flux densities generated in a laboratory. Their responses may be related to clustering of their lateral buds. Testing of additional species using these methods in a laboratory setting, and perhaps additional methodologies in the field, is warranted.

Summary The dead foliage of scorched crowns is one of the most conspicuous signatures of wildland fires. Globally, crown scorch from fires in savannas, woodlands and forests causes tree stress and death across diverse taxa. The term crown scorch, however, is inconsistently and ambiguously defined in the literature, causing confusion and conflicting interpretation of results. Furthermore, the underlying mechanisms causing foliage death from fire are poorly understood. The consequences of crown scorch – alterations in physiological, biogeochemical and ecological processes and ecosystem recovery pathways – remain largely unexamined. Most research on the topic assumes the mechanism of leaf and bud death is exposure to lethal air temperatures, with few direct measurements of lethal heating thresholds. Notable information gaps include how energy transfer injures and kills leaves and buds, how nutrients, carbohydrates, and hormones respond, and what physiological consequences lead to mortality. We clarify definitions to encourage use of unified terminology for foliage and bud necrosis resulting from fire. We review the current understanding of the physical mechanisms driving foliar injury, discuss the physiological responses, and explore novel ecological consequences of crown injury from fire. From these elements, we propose research needs for the increasingly interdisciplinary study of fire effects.

Background The structure and function of fire-prone ecosystems are influenced by many interacting processes that develop over varying time scales. Fire creates both instantaneous and long-term changes in vegetation (defined as live, dead, and decomposing plant material) through combustion, heat transfer to living tissues, and subsequent patterns of recovery. While fuel available for combustion may be relative to the amount of vegetation, it is equally instructive to evaluate how the physical structure and other characteristics of vegetation influence fire dynamics, and how these interactions change between fire events. This paper presents a conceptual framework for how vegetation not only embodies the legacy of previous fires but creates the physical environment that drives fire behavior beyond its combustion as a fuel source. Results While many environmental factors affect both the post-fire vegetation trajectory and fire dynamics themselves, we present a conceptual framework describing how vegetation’s structural characteristics control the local microclimate and fluid dynamics of fire-induced flows, and how that is influenced by ecosystem and atmospheric processes. Shifting our focus from fuels to vegetation allows us to integrate spatial and temporal feedbacks between fire, vegetation, soil, and the atmosphere across scales. This approach synthesizes the combustion and flammability science, the physical influence on fire behavior, and the ecosystem dynamics and processes that occur between fires and within a fire regime. Conclusions We conclude that fire behavior, including its prediction and ecological effects, should be broadened to include the dynamic processes that interact with vegetation, beyond its role as fuel. Our conceptual framework illustrates the crucial feedbacks across scales that link the finer details of vegetation and fire behavior processes that occur within a fire and have additive effects that feedback into the coarser scale processes and functions within an ecosystem. Shifting the fuels paradigm to integrate the combustion, physical, and ecological roles of vegetation as complex drivers of fire behavior and outcomes will broaden discovery within wildland fire science and ecology.

Long-term fire exclusion may weaken ecosystem resistance to the return of fire. We investigated how a surface wildfire that occurred after several decades of fire exclusion affected a southern Appalachian forest transitioning from a fire-adapted to a fire-intolerant state. Tree traits associated with fire adaptation often co-occur with traits for nutrient conservation, including the ectomycorrhizal (ECM) association. In the absence of fire, the ECM association may facilitate the accumulation of organic matter, which becomes colonized by fine roots that then become vulnerable to consumption or damage by fire. Therefore, a deeper organic horizon might make stands of fire-adapted, ECM trees less resistant to a surface wildfire than stands of arbuscular mycorrhizal (AM), fire-intolerant trees. To test this hypothesis, we established plots in stands that fall along a gradient of mycorrhizal tree relative abundance both inside and outside the perimeter of the 2016 Rock Mountain wildfire. With increasing relative abundance of ECM trees, we found increasing organic horizon depth and mass and slower rates of decay, even for litter of ECM tree species. We calculated a major (73–83%) reduction in fine root biomass and length in the organic horizon following the wildfire. Over three years post-fire, we observed a higher probability of crown decline, basal sprouting and aboveground biomass mortality with increasing abundance of ECM trees. We propose that the biogeochemistry of mycorrhizal associations can help explain why fire exclusion makes stands of fire-adapted trees less resistant to a surface wildfire than those with fire-intolerant trees.

Interest in prescribed fire science has grown over the past few decades due to the increasing application of prescribed fire by managers to mitigate wildfire hazards, restore biodiversity, and improve ecosystem resilience. Numerous ecological disciplines use prescribed fire experiments to provide land managers with evidence-based information to support prescribed fire management. Documenting variation in the context and conditions during prescribed fire experimental treatments is critical for management inference, but inconsistencies in reporting critical experimental details can complicate interpretation. Such details are needed to provide ecological and empirical context for data, facilitate experimental replication, enable meta-analyses, and maximize utility for other scientists and practitioners. To evaluate reporting quality in the recent literature, we reviewed 219 prescribed fire experiments from 16 countries published in 11 refereed journals over the last 5 years. Our results suggest substantial shortcomings in the reporting of critical data that compromise the utility of this research. Few studies had specific information on burning conditions such as fuel moisture (22%), quantitative fuel loads (36%), fire weather (53%), and fire behavior (30%). Further, our analysis revealed that 63% of the studies provided precise coordinates for their study area, while 30% of studies indicated the prescribed fire date. Only 54% of the studies provided descriptions of the ignition characteristics. Given these common deficiencies, we suggest minimum reporting standards for future prescribed fire experiments. These standards could be applied to journal author guidelines, directed to researchers and reviewers by the editor, and promoted in the education of fire ecologists. Establishing reporting standards will increase the quality, applicability, and reproducibility of prescribed fire science, facilitate future research syntheses, and foster actionable science.

The archaeology of fire is a developing field. One challenge centers on equifinality: distinguishing the affects of wildfire versus anthropogenic fire. Especially where evidence for control of fire by humans in the early Pleistocene remains debated, there is little consensus regarding what constitutes clear evidence of human-control. Another concern is preservation bias, which reduces clearly identifiable archaeological signatures of fire. In this paper we argue that a peculiar lithic angular fragment—termed thermal curved-fragment (TCF)—exhibits statistically distinct, quantitative evidence of the confluence of human-knapped stone tools and exposure to a high-energy, long-duration, ground-level fire (i.e., campfires). Experimental TCFs are described and compared to unfired knapping debitage, natural exfoliations and suspected archaeological TCFs. The provenance of these archaeological specimens has previously been argued to infer hominin-controlled fire at 1.5–1.6 Ma at the Koobi Fora Formation. We also present data from experiments exposing stone flakes (arranged as “scatters”) of similar raw materials to those found in the Koobi Fora Formation to USDA prescribed burns in a variety of conditions approximating landscape fires. Results indicate that TCFs are formed specifically where (previously) knapped stone is exposed to high-energy ground level fires, similar to those seen in ethnographic campfires. Our analysis indicates that TCFs can be used in conjunction with other lines of evidence indicating the presence of anthropogenic fire in the archaeological record.

Fine dead fuel moisture has a major influence on wildland fire behavior yet the dynamics driving water exchange of fuel particles in forested environments remain poorly understood. Most fire behavior models rely on simple, stand-level fuel moisture estimates, ignoring potentially important variation occurring within fuelbeds that could influence fire behavior. This is especially true in surface fire regimes where variation in fine-scale fuel properties drive fire behavior and subsequent fire effects. Saw palmetto [Serenoa repens (Bartr.) Small] dominated fuelbeds in the pine forests of the southeastern United States have high within stand variation in one of the most fire prone habitats in the world. Pine needles and palmetto fronds dominate the biomass of fine dead fuel types that produce extreme fire behavior. To assess predictors of fine dead fuel moisture, we analyzed fuel moisture dynamics of these two fine dead fuel types over a two-year period in conjunction with under- and overstory forest meteorological data. Using multiple models and time lag analysis of within-stand moisture dynamics, the results indicate that saw palmetto and pine dramatically differ in drying regimes, primarily resulting from different responses to cumulative rainfall, net radiation, and antecedent atmospheric moisture content. Despite being responsive to changes in relative humidity, saw palmetto was significantly dryer than pine under nearly all meteorological conditions, and it was capable of maintaining extremely low fuel moisture despite high relative humidity or rainfall. Our results point to the need to capture additional drivers of microclimatic variation to aid fire managers in accurately predicting within-stand fuel moisture and subsequent fire behavior. Improving the scientific community’s understanding of variation in complex fuel beds is critical for effectively managing risk in fire prone ecosystems.

Wildland fires have a multitude of ecological effects in forests, woodlands, and savannas across the globe. A major focus of past research has been on tree mortality from fire, as trees provide a vast range of biological services. We assembled a database of individual-tree records from prescribed fires and wildfires in the United States. The Fire and Tree Mortality (FTM) database includes records from 164,293 individual trees with records of fire injury (crown scorch, bole char, etc.), tree diameter, and either mortality or top-kill up to ten years post-fire. Data span 142 species and 62 genera, from 409 fires occurring from 1981-2016. Additional variables such as insect attack are included when available. The FTM database can be used to evaluate individual fire-caused mortality models for pre-fire planning and post-fire decision support, to develop improved models, and to explore general patterns of individual fire-induced tree death. The database can also be used to identify knowledge gaps that could be addressed in future research., Measurement(s)plant morphology trait • tree mortality • fire • tree fire injury • wildfireTechnology Type(s)digital curationFactor Type(s)year of data collection • geographic location of fire • tree fire injurySample Characteristic - OrganismtreesSample Characteristic - Environmentforest ecosystemSample Characteristic - LocationCascades Region • Blue Mountains • Far Northern Rockies • Sierra Nevada • Piedmont Province • Region of Piedmont • Atlantic and Gulf Coastal Plain Floristic Province • Northern Rocky Mountains Provincial Park Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.12369293

Background Many Puerto Rican ecosystems evolved without a regular fire regime. As such, many native plants lack adaptations necessary to survive even low-intensity fires. Human-caused fires are increasing in frequency, in part promoted by the presence of invasive grasses. During the afternoon of 19 February 2014, a wildfire burned a large portion of the dry forest in El Faro Natural Reserve, Cabo Rojo, Puerto Rico. Using a previously monitored population, we documented the mortality and morphological damage on three columnar and semi-epiphytic cactus species (Pilosocereus royenii [L.] Byles & Rowley, Harrisia portoricensis Britton, and Leptocereus quadricostatus Britton) and one globular species (Melocactus intortus [Mill.] Urb.) in relation to canopy cover and cactus growth strategy. Results Our results suggest that M. intortus and H. portoricensis were more susceptible to fire damage. Cacti growing in areas dominated by grasses and shrubs were significantly more likely to burn than those growing under a closed tree canopy. Apart from L. quadricostatus, cacti that survived at least one year after the fire had lost spines, developed scarring tissue in some or all ribs, and few were able to regrow. Conclusions Because extensive tissue damage and environmental alterations were observed during the post-fire survey, which occurred between 14 to 19 months after the fire, we argue there will be significant delayed mortality and that the mortality estimates presented here are conservative.

Monitoring understory plant diversity is important, allowing managers to track current diversity status and trends both spatially and temporally at a landscape-scale. Improving precision in quantifying patterns in understory plant diversity improves efficiency in monitoring design and more accurate measures of success of management intervention over time. Patterns of species diversity are dependent upon the scale in which they are examined – an increase in small-scale diversity across a gradient can convert to a decrease in large-scale diversity across that same gradient. Using two extensive datasets including both mined historical data and supplemental experimental data, we performed an additive partitioning of plant diversity to elucidate the hierarchical spatial patterns of understory plant species richness, and independent measures of alpha and beta diversity in the species-rich longleaf pine ecosystem at Eglin Air Force Base in northwestern FL, USA. This analysis allowed us to identify the spatial scale that most effectively captures plant diversity to inform monitoring efforts by using measures of species turnover, specifically beta diversity. We found that while species richness and alpha diversity increased with spatial scale, beta diversity began to reach an asymptote at smaller (1 m2) scales. Furthermore, we found the sampling effort at this 1 m2 scale required as few as 60 plots to effectively estimate plant diversity within management blocks. While our results are attributable to Eglin AFB specifically, these scaling analyses can help to streamline monitoring efforts in other ecosystems that seek to elucidate the individual contributions of diversity components.

Wildland fire dynamics are a complex three-dimensional turbulent process. Cellular automata (CA) is an efficient tool to predict fire dynamics, but the main parameters of the method are challenging to estimate. To overcome this challenge, we compute statistical distributions of the key parameters of a CA model using infrared images from controlled burns. Moreover, we apply this analysis to different spatial scales and compare the experimental results with a simple statistical model. By performing this analysis and making this comparison, several capabilities and limitations of CA are revealed.

The realm of wildland fire science encompasses both wild and prescribed fires. Most of the research in the broader field has focused on wildfires, however, despite the prevalence of prescribed fires and demonstrated need for science to guide its application. We argue that prescribed fire science requires a fundamentally different approach to connecting related disciplines of physical, natural, and social sciences. We also posit that research aimed at questions relevant to prescribed fire will improve overall wildland fire science and stimulate the development of useful knowledge about managed wildfires. Because prescribed fires are increasingly promoted and applied for wildfire management and are intentionally ignited to meet policy and land manager objectives, a broader research agenda incorporating the unique features of prescribed fire is needed. We highlight the primary differences between prescribed fire science and wildfire science in the study of fuels, fire behavior, fire weather, fire effects, and fire social science. Wildfires managed for resource benefits (“managed wildfires”) offer a bridge for linking these science frameworks. A recognition of the unique science needs related to prescribed fire will be key to addressing the global challenge of managing wildland fire for long-term sustainability of natural resources.

Globally, there are myriad situations in which people aim to conserve, restore, or manage forest ecosystems at small spatial scales of 50 ha or less. To inform management, forest dynamics models provide an increasingly diverse and valuable portfolio of tools for projecting forest change under different management and environmental conditions. Yet, many models may not be appropriate or feasible to use in small forest management because of their design for larger-scale applications, the information needed to initialize models, or discrepancies between model outputs and information relevant for small forest management objectives. This review explores the suitability of 54 existing forest dynamics models to inform the management of small forests. We evaluated the characteristics of each model using five criteria with implications for small forest management: spatial resolution, number of species the model can simulate, inclusion of spatial structure, modeling approach, and mechanistic detail. While numerous models can be suitable under certain conditions, the review criteria led us to conclude that two models offered the broadest versatility and usability for small forest contexts, SORTIE and FORMIND. This review can help orient and guide small forest managers who wish to add modeling to their forest management efforts.

Much of fire behavior is driven by fine-scale patterns of fuel moisture; however, moisture predictions typically occur over large scales. The source of fine-scale variation in moisture results from a combination of fuelbed properties and overstory forest structure that influences water movement and distribution of solar radiation. Fine-scale moisture variation is of particular relevance in humid forests managed with frequent prescribed fire where fire behavior variation is tightly linked to differential fire effects. Results of a three-tiered experiment combining laboratory and field methods demonstrated that solar radiation exerted a strong influence on fuel moisture patterns in a temperate humid pine forest. Infrared radiation more rapidly dried Quercus and Pinus litter in laboratory experiments compared with controls. Litter exposed to sunlight during small-scale outdoor experiments was significantly drier than shaded litter. Quercus litter was wetter than Pinus on mornings, but dried more rapidly, becoming drier than Pinus litter by mid-day when exposed to sunlight. Field observations validated small-scale outdoor and laboratory results but also revealed the influence of fuel position: elevated litter was wetter than ground-level litter at peak burning time. Results provide insight into how overstory structure and composition may influence fine-scale heterogeneity of surface moisture dynamics and fire behavior.

Current research on interactions between ecological disturbances emphasizes the potential for greatly enhanced ecological effects that may occur when disturbances interact. Much less attention has focused on the possibility of disturbance interactions that buffer ecological change. In this review, we discuss and classify evidence for interactions between two forest disturbances common in eastern North America—wind damage and fire—focusing on studies where forest wind damage precedes fire. Interaction mechanisms are classified according to how they influence ecosystem resistance to and resilience from subsequent disturbances and whether interactions have synergistic or antagonistic effects. Several important generalizations emerge from this synthesis of disturbance interactions. First, buffering interactions between wind damage and fire may be more important when fire intensity is low. Second, wind–fire interactions related to changes in fuel may vary with climatic conditions, with regional differences, and with intensity or severity of individual disturbances. Third, both amplifying and buffering effects may co-occur in a spatial mosaic through a variety of interaction mechanisms. In this respect, the concept of ecosystem response to multiple disturbances parallels that of classical models of successional pathways. It is useful to conceptualize ecosystem response to compounded disturbances as a diverse collection of individual, co-occurring mechanisms of interaction rather than considering multiple disturbances to be wholly amplifying or wholly buffering. Future studies on wind–fire disturbances that explicitly examine mechanisms of interactions and the factors that govern them will aid in understanding these ecologically important and ubiquitous forest disturbances.

The spatial pattern of surface fuelbeds in fire-dependent ecosystems are rarely captured using long-standing fuel sampling methods. New techniques, both field sampling and remote sensing, that capture vegetation fuel type, biomass, and volume at super fine-scales (cm to dm) in three-dimensions (3D) are critical to advancing forest fuel and wildland fire science. Such scales are particularly important for some computational fluid dynamics fire behavior models that operate in 3D and have implications for wildland fire operations and fire effects research. This study describes the coupling of new 3D field sampling data with terrestrial laser scanning (TLS) data to infer fine-scale fuel mass in 3D. We found that there are strong relationships between fine-scale mass and TLS occupied volume, porosity, and surface area, which were used to develop fine-scale prediction equations using TLS across vegetative fuel types, namely grasses and shrubs. The application of this novel 3D sampling technique to high resolution TLS data in this study represents an advancement in producing inputs for computational fluid dynamics fire behavior models that will improve understanding fire-vegetation feedbacks in highly managed fire-dependent ecosystems.

Fire is a global process that drives patterns of biodiversity. In frequently burned fire-dependent ecosystems, surface fire regimes allow for the coexistence of high plant diversity at fine-scales even where soils are uniform. The mechanisms on how fire impacts groundcover community dynamics are however, poorly understood. Because fire can act as a stochastic agent of mortality, we hypothesized that a neutral mechanism might be responsible for maintaining plant diversity. We used the demographic parameters of the Unified Neutral Theory of Biodiversity (UNTB) as a foundation to model groundcover species richness, using a southeastern U.S. pine woodland as an example. We followed the fate of over 7,000 individuals of 123 plant species for four years and two prescribed burns in frequently burned Pinus palustris sites in NW FL, USA. Using these empirical data and UNTB-based assumptions, we developed two parsimonious autonomous agent models, which were distinct by spatially explicit and implicit local recruitment processes. Using a parameter sensitivity test, we examined how empirical estimates, input species frequency distributions, and community size affected output species richness. We found that dispersal limitation was the most influential parameter, followed by mortality and birth, and that these parameters varied based on scale of the frequency distributions. Overall, these nominal parameters were useful for simulating fine-scale groundcover communities, although further empirical analysis of richness patterns, particularly related to fine-scale burn severity is needed. This modeling framework can be utilized to examine our premise that localized groundcover assemblages are neutral communities at high fire frequencies, as well as examine the extent to which niche-based dynamics determine community dynamics when fire frequency is altered and spatial fire intensity patterns differ.

Frequently disturbed ecosystems are characterized by resilience to ecological disturbances. Longleaf pine ecosystems are not only resilient to frequent fire disturbance, but this feature sustains biodiversity. We examined how fire frequency maintains beta diversity of multi-trophic interactions in longleaf pine ecosystems, as this community property provides a measure of functional redundancy of an ecosystem. We found that beta interaction diversity at small local scales is highest in the most frequently burned stands, conferring immediate resiliency to disturbance by fire. Interactions become more specialized and less resilient as fire frequency decreases. Local scale patterns of interaction diversity contribute to broader scale patterns and confer long-term ecosystem resiliency. Such natural disturbances are likely to be important for maintaining regional diversity of interactions for a broad range of ecosystems.

Eglin Air Force Base (AFB) in Florida, in the United States, conserves a large reservoir of native longleaf pine (Pinus palustris Mill.) stands that land managers maintain by using frequent fires. We predicted tree density, basal area, and dominant tree species from 195 forest inventory plots, low-density airborne LiDAR, and Landsat data available across the entirety of Eglin AFB. We used the Random Forests (RF) machine learning algorithm to predict the 3 overstory responses via univariate regression or classification, or multivariate k-NN imputation. Ten predictor variables explained ∼ 50% of variation and were used in all models. Model accuracy and precision statistics were similar among the various RF approaches, so we chose the imputation approach for its advantage of allowing prediction of the ancillary plot attributes of surface fuels and ground cover plant species richness. Maps of the 3 overstory response variables and ancillary attributes were imputed at 30-m resolution and then aggregate...

Understanding fine-scale variability in understory fuels is increasingly important as physics-based fire behavior models drive needs for higher-resolution data. Describing fuelbeds 3Dly is critical in determining vertical and horizontal distributions of fuel elements and the mass, especially in frequently burned pine ecosystems where fine-scale fuels arrangement drives fire intensity and resulting fire effects. Here, we describe research involving the use of highly resolved 3D models. We create fuelbeds using individual grass, litter, and pinecone models designed from field measurements. These fuel models are distributed throughout the fuelbed to replicate fuel distribution in rectified nadir photography taken for each plot. The simulated fuelbeds are converted into voxel arrays and biomass is estimated from calculated surface area between mesh vertices for each voxel. We compare field-based fuel depth and biomass with simulated estimates to demonstrate similarities and differences. Biomass distri...

Methods characterizing fine-scale fuels and plant diversity can advance understanding of plant-fire interactions across scales and help in efforts to monitor important ecosystems such as lo...

Wildland fire radiant energy emission is one of the only measurements of combustion that can be made at high temporal and spatial resolutions. Furthermore, spatially and temporally explicit measurements are critical for making inferences about ecological fire effects. Although the correlation between fire frequency and plant biological diversity in frequently burned coniferous forests is well documented, the ecological mechanisms explaining this relationship remains elusive. Uncovering these mechanisms will require highly resolved, spatially explicit fire data (Loudermilk et al. 2012). Here, we describe our efforts at connecting spatial variability in fuels to fire energy release and fire effects using fine scale (1 cm2) longwave infrared (LWIR) thermal imagery. We expected that the observed variability in fire radiative energy release driven by canopy-derived fuels could be the causal mechanism driving plant mortality, an important component of community dynamics. Analysis of fire radiant energy ...

Light Detection and Ranging (LiDAR) has demonstrated potential for forest inventory at the individual-tree level. The aim in this study was to predict individual-tree height (Ht; m), basal area (BA; m2), and stem volume (V; m3) attributes, imputing Random Forest k-nearest neighbor (RF k-NN) and individual-tree-level-based metrics extracted from a LiDAR-derived canopy height model (CHM) in a longleaf pine (Pinus palustris Mill.) forest in southwestern Georgia, United States. We developed a new framework for modeling tree-level forest attributes that comprise 3 steps: (i) individual tree detection, crown delineation, and tree-level-based metrics computation from LiDAR-derived CHM; (ii) automatic matching of LiDAR-derived trees and field-based trees for a regression modeling step using a novel algorithm; and (iii) RF k-NN imputation modeling for estimating tree-level Ht, BA, and V and subsequent summarization of these metrics at the plot and stand levels. RMSDs for tree-level Ht, BA, and V were 2.96%, 58.62%, and 8.19%, respectively. Although BA estimation accuracy was poor because of the longleaf pine growth habitat, individual-tree locations, Ht, and V were estimated with high accuracy, especially in low-canopy-cover conditions. Future efforts based on the findings could help improve the estimation accuracy of individual-tree-level attributes such as BA.

Emerald ash borer (EAB) (Agrilus planipennis), is a non-native beetle responsible for widespread mortality of several North American ash species (Fraxinus sp.). Current non-destructive methods for early detection of EAB in specific trees are limited, which restricts the effectiveness of management efforts to contain this invasive threat. This study explored the application of near-infrared (NIR) spectroscopy as a novel method for detection of EAB in white ash (Fraxinus americana). Increment borers were used to non-destructively and efficiently collect increment cores from visibly healthy and EAB infested white ash trees for subsequent NIR analysis. White ash trees were sampled across sites of different land use categories (i.e., natural forests versus recreational areas) and different latitudinal regions in the eastern Lower Peninsula and in the western Upper Peninsula of Michigan. NIR diffuse reflectance spectra were collected from three stem tissue types (outer bark, phloem, and xylem) using a NIR spectrometer over the wavelength range of 1134–2190 nm. Spectral measurements were treated with a Savitzky–Golay smoothing filter, followed by a 1st and 2nd derivative transformation to increase spectral sensitivity. Near-infrared spectroscopy was successfully able to discriminate between EAB infested and visually healthy trees using step-wise linear discriminant analysis for each of the three stem tissue types (outer bark, phloem and xylem). The NIR spectra of xylem tissue transformed using a Savitzky–Golay smoothing filter with a 1st derivative transformation over the full NIR wavelength range (1134–2190 nm) had the highest classification accuracy (97%) for discriminating between healthy versus EAB infested trees. This study underscores potential for future research in developing NIR spectroscopy as a cost-effective method of early detection and monitoring of emerald ash borer and other stem-boring insects in support of current detection methods.

Within the temperate, deciduous forests of the eastern US, diverse soil-fauna communities are structured by a combination of environmental gradients and interactions with other biota. The introduction of non-native soil taxa has altered communities and soil processes, and adds another degree of variability to these systems. We sampled soil macroinvertebrate abundance from forested sites in Missouri (MO), Michigan (MI), Massachusetts (MA), and New Hampshire (NH), with the objective of comparing community assemblages and evaluating the role of invasive earthworms along the temperature—productivity gradient represented by the sites. The primary detritivores encountered were earthworms and millipedes. Earthworms were collected only in MO and MI, and at much greater density in MO. Millipedes were found at every site except in MO, and at their highest mean density in NH. Warmer temperatures, higher litter productivity, and low Oa horizon depth (as found in MO) were correlated with high earthworm activi...

In the fire maintained longleaf pine (Pinus palustris) ecosystem, underground refugia such as gopher tortoise (Gopherus polyphemus) burrows and stump holes may be important for animals to escape fire and extreme temperatures. Despite being documented as refugia for several species of concern including the black pine snake (Pituophis melanoleucus lodingi) and eastern diamondback rattlesnake (Crotalus adamanteus), longleaf pine stumps are commonly removed and harvested for rosin, eliminating associated underground habitats. We used trail cameras to examine the use of stump holes by vertebrates from September 2018 – May 2019. Each of 35 stump holes was paired with a nearby gopher tortoise burrow, a documented high value refugium type, to serve as a reference. We used Shannon Diversity Index to investigate species diversity differences and non-metric multidimensional scaling to investigate species composition differences between stump holes and tortoise burrows. We developed multi-season occupancy models to investigate reptile, amphibian, bird, and small mammal occupancy differences between tortoise burrows and stump holes. We documented 13 taxa unique to stump holes, 14 taxa unique to tortoise burrows, and 26 shared taxa. Although overall species diversity was similar between tortoise burrows and stump holes, species composition differed, with more reptile species associated with stump holes and more bird species associated with gopher tortoise burrows. Reptile, amphibian, bird, and small mammal occupancy was similar between stump holes and tortoise burrows and among stumps of varying decay states. Our research underscores the collective importance of tortoise burrows and stump holes as refugia and foraging sites for wildlife in the longleaf pine ecosystem. Additionally, our study demonstrates the importance of developing best management practices for stump removal such as retaining a proportion of stumps of different decay classes.

In the Southeastern United States, the function and stability of pine ecosystems depends on frequent low intensity fires. One of the critical effects of frequent fire is the inhibition of hardwood competition by removing above-ground stems (top-kill). Previous long-term studies have correlated early growing season burns with higher understory mortality when compared to dormant season burns. Seasonal differences in mortality from insufficient carbon reserves in roots after leaf flush were posited as the mechanism but this was never explicitly tested. In this experiment, we burned two-year-old pot-grown sweetgums (Liquidambar styraciflua L.) in the dormant season (February), growing season (May), and compared their physiological responses to plants that were unburned. By the end of the first post-burn growing season, mortality was higher after the dormant season burn than the growing season burn and unburned trees had nearly twice the mass of either the burned treatments. Tissue starch concentrations were similar across all treatments highlighting the resiliency of sweetgum carbon stocks to recover from above-ground stem removal regardless of season. We showed the critical importance of top-killing stems regardless of season of burn. Our results further suggest that dormant season fires can be more lethal to young sweetgum, possibly due to susceptibility of tender new shoots to freezing damage.