Eastern Forests Research Articles

Palynology and the Ecology of the New Zealand Conifers

The New Zealand conifers (20 species of trees and shrubs in the Araucariaceae, Podocarpaceae and Cupressaceae) are often regarded as ancient Gondwanan elements, but mostly originated much later. Often thought of as tall trees of humid, warm forests, they are present throughout in alpine shrublands, tree lines, bogs, swamps, and in dry, frost-prone regions. The tall conifers rarely form purely coniferous forest and mostly occur as an emergent stratum above evergreen angiosperm trees. During Maori settlement in the 13th century, these fire-sensitive trees succumbed rapidly, most of the drier forests being lost. As these were also the more conifer-rich forests, ecological research has been skewed towards conifer dynamics of forests wetter and cooler than the pre-human norm. Conifers are well represented in the pollen record and we here we review their late Quaternary history in the light of what is known about their current ecology with the intention of countering this bias. During glacial episodes, all trees were scarce south of c. 40°S, and extensive conifer-dominant forest was confined to the northern third of the North Island. Drought- and cold-resistant Halocarpus bidwillii and Phyllocladus alpinus formed widespread scrub in the south. During the deglacial, beginning 18,000 years ago, tall conifers underwent explosive spread to dominate the forest biomass throughout. Conifer dominance lessened in favour of angiosperms in the wetter western lowland forests over the Holocene but the dryland eastern forests persisted largely unchanged until settlement. Mid to late Holocene climate change favoured the more rapidly growing Nothofagaceae which replaced the previous conifer-angiosperm low forest or shrubland in tree line ecotones and montane areas. The key to this dynamic conifer history appears to be their bimodal ability to withstand stress, and dominate on poor soils and in cool, dry regions but, in wetter, warmer locations, to slowly grow thorough competing broadleaves to occupy an exposed, emergent stratum where their inherent stress resistance ensures little effective angiosperm competition.

Growth traits of juvenile American chestnut and red oak as adaptations to disturbance

American chestnut (Castanea dentata) was a dominant species in eastern North America prior to the importation of chestnut blight. In light of recent efforts to restore viable populations of chestnut in eastern forests, an increased understanding of its association with other co‐occurring, disturbance‐adapted oak species is necessary. We evaluated crown architecture and leaf morphology in juvenile chestnut and red oak (Quercus rubra) to assess potential differences in establishment strategies of both species. We also investigated differences in nonstructural carbohydrate reserves and whole tree biomass partitioning between species. Seedlings of both species were planted in forest stands treated either with midstory removal or small patch cuts, simulating potential restoration plantings. After 5–7 years, chestnut's allocation to its root system was lower than red oak's, with chestnut saplings instead diverting resources to branches and foliage. Chestnut had lower leaf area index, greater crown projection area, and higher specific leaf area than red oak, indicating the species may have an advantage in shaded understories. There were only minor differences in nonstructural root carbohydrate reserves, between red oak and American chestnut, indicating that chestnut may respond similarly to oak by resprouting after disturbances topkill young saplings. We suggest that American chestnut has morphological and physiological attributes that allow it to function as an opportunistic and plastic species that can utilize gaps to facilitate its canopy recruitment, yet still persist after occasional surface fire. This knowledge can guide restoration strategies for this iconic species of the eastern temperate forest region.

Cold tolerance of mountain pine beetle among novel eastern pines: A potential for trade-offs in an invaded range?

Novel hosts may have unforeseen impacts on herbivore life history traits. The mountain pine beetle (Dendroctonus ponderosae Hopkins) is a tree-killing bark beetle native to western North America but constrained by cold temperatures in the northern limits of its distribution. In recent years, this insect has spread north and east of its historical range, and continued expansion, or accidental introduction, could result in the mountain pine beetle becoming invasive in eastern North America. The limiting effect of cold temperatures among novel host pines is unknown, yet crucial for understanding the risk posed to northeastern North American forests. We report the susceptibility of mountain pine beetle to cold temperatures while overwintering in six different pine species. Brood developed in two western pine hosts (Pinus contorta Dougl. var. latifolia Engelm. and P. ponderosa Dougl. ex. Laws. var. scopulorum Engelm.) as well as four eastern pines (P. banksiana Lamb., P. resinosa Ait., P. strobus L. and P. sylvestris L.) novel to this insect. The cold tolerance and cold tolerance strategy of the most common overwintering stage varied by host and year. Models describing lower lethal temperatures more accurately predicted observed field mortality of overwintering larvae than models based on temperatures at which larvae froze. Rapid development to less cold tolerant pupal and adult stages by brood in novel hosts prior to winter may constitute a trade-off between increased host suitability and winter mortality. We demonstrate that overwintering survival of mountain pine beetles in novel hosts depends on a match between the climate and ecophysiological effects of pine species. These results have implications for risk assessment models and management planning for eastern forests as mountain pine beetle continues to expand its range.

The implications of American chestnut reintroduction on landscape dynamics and carbon storage

AbstractIn the eastern United States, American chestnut (Castanea dentata) was historically a major component of forest communities, but was functionally extirpated in the early 20th century by an introduced pathogen, chestnut blight (Cryphonectria parasitica). Because chestnut is fast‐growing, long‐lived, and resistant to decay, restoration of American chestnut using blight‐resistant stock could have the potential to increase carbon sequestration or storage in forested landscapes. However, carbon dynamics are also affected by interspecific competition, succession, natural disturbance, and forest management activities, and it is unknown how chestnut restoration might interact with these other processes. We used the PnET‐Succession extension of the LANDIS‐II forest landscape model to study the implications of chestnut restoration on forest composition and carbon storage in the context of other disturbances, including timber harvest and insect pest outbreaks. Our results imply that it could take a millennium or more for chestnut to fully occupy landscapes without aggressive restoration efforts. When successful, chestnut restoration activities displaced other species approximately in proportion to their abundance on the landscape, rather than replacing a single species or genus (e.g., Quercus). Insect pests increased the rate of chestnut colonization by reducing the abundance of competitors, and also had a dominant effect on carbon dynamics. Although chestnut is fast‐growing, moderately shade‐tolerant, and decomposes very slowly, our results suggest that it can only modestly increase the carbon storage potential of eastern forests. However, our results also demonstrate that compositional changes in forest communities can have noticeable effects on biomass accumulation, even with the large uncertainties introduced by invasive pests.

Effectiveness of Winkler Litter Extraction and Pitfall Traps in Sampling Ant Communities and Functional Groups in a Temperate Forest.

Selection of proper sampling methods for measuring a community of interest is essential whether the study goals are to conduct a species inventory, environmental monitoring, or a manipulative experiment. Insect diversity studies often employ multiple collection methods at the expense of researcher time and funding. Ants (Formicidae) are widely used in environmental monitoring owing to their sensitivity to ecosystem changes. When sampling ant communities, two passive techniques are recommended in combination: pitfall traps and Winkler litter extraction. These recommendations are often based on studies from highly diverse tropical regions or when a species inventory is the goal. Studies in temperate regions often focus on measuring consistent community response along gradients of disturbance or among management regimes; therefore, multiple sampling methods may be unnecessary. We compared the effectiveness of pitfalls and Winkler litter extraction in an eastern temperate forest for measuring ant species richness, composition, and occurrence of ant functional groups in response to experimental manipulations of two key forest ecosystem drivers, white-tailed deer and an invasive shrub (Amur honeysuckle). We found no significant effect of sampling method on the outcome of the ecological experiment; however, we found differences between the two sampling methods in the resulting ant species richness and functional group occurrence. Litter samples approximated the overall combined species richness and composition, but pitfalls were better at sampling large-bodied (Camponotus) species. We conclude that employing both methods is essential only for species inventories or monitoring ants in the Cold-climate Specialists functional group.

Seasonal variation in effects of herbivory on foliar nitrogen of a threatened conifer.

Invasive herbivores can dramatically impact the nitrogen (N) economy of native hosts. In deciduous species, most N is stored in stem tissues, while in evergreen conifer species N is stored in needles, making them potentially more vulnerable to herbivory. In eastern forests of the USA, the long-lived, foundational conifer eastern hemlock (Tsuga canadensis) is under the threat of extirpation by the invasive hemlock woolly adelgid (HWA: Adelges tsugae). We assessed the impact of HWA infestation on the patterns of seasonal foliar N availability in hemlock planted in a deciduous forest understory. Over the course of a year, we sampled needles and twigs and measured N, carbon (C), C:N ratio, and total protein concentrations. Tissue sampling events were timed to coincide with key life-history transitions for HWA to determine the association between HWA development and feeding with these foliar nutrients. In uninfested trees, needle and twig N concentrations fluctuated across seasons, indicating the potential importance of N storage and remobilization for the N economy of eastern hemlock. Although N levels in HWA-infested trees also cycled annually, the degree to which N concentrations fluctuated seasonally in tissues was significantly affected by HWA feeding. These fluctuations exceeded N levels observed in control trees and coincided with HWA feeding. HWA feeding generally increased N concentrations but did not affect protein levels, suggesting that changes in N do not occur via adelgid-induced protein breakdown. Herbivore-induced mobilization of N to feeding sites and its rapid depletion may be a significant contributor to eastern hemlock mortality in US forests.

Long-term structural and biomass dynamics of virgin Tsuga canadensis-Pinus strobus forests after hurricane disturbance.

The development of old-growth forests in northeastern North America has largely been within the context of gap-scale disturbances given the rarity of stand-replacing disturbances. Using the 10-ha old-growth Harvard Tract and its associated 90-year history of measurements, including detailed surveys in 1989 and 2009, we document the long-term structural and biomass development of an old-growth Tsuga canadensis-Pinus strobus forest in southern New Hampshire, USA following a stand-replacing hurricane in 1938. Measurements of aboveground biomass pools were integrated with data from second- and old-growth T.canadensis forests to evaluate long-term patterns in biomass development following this disturbance. Ecosystem structure across the Tract prior to the hurricane exhibited a high degree of spatial heterogeneity with the greatest levels of live tree basal area (70-129m2 /ha) on upper west-facing slopes where P.strobus was dominant and intermixed with T.canadensis. Live-tree biomass estimates for these stratified mixtures ranged from 159 to 503Mg/ha at the localized, plot scale (100m2 ) and averaged 367Mg/ha across these portions of the landscape approaching the upper bounds for eastern forests. Live-tree biomass 71years after the hurricane is more uniform and lower in magnitude, with T.canadensis currently the dominant overstory tree species throughout much of the landscape. Despite only one living P.strobus stem in the 2009 plots (and fewer than five stems known across the entire 10-ha area), the detrital legacy of this species is pronounced with localized accumulations of coarse woody debris exceeding 237.7-404.2m3 /ha where this species once dominated the canopy. These patterns underscore the great sizes P.strobus attained in pre-European landscapes and its great decay resistance relative to its forest associates. Total aboveground biomass pools in this 71-year-old forest (255Mg/ha) are comparable to those in modern old-growth ecosystems in the region that also lack abundant white pine. Results highlight the importance of disturbance legacies in affecting forest structural conditions over extended periods following stand-replacing events and underscore that post-disturbance salvage logging can alter ecosystem development for decades. Moreover, the dominant role of old-growth P.strobus in live and detrital biomass pools before and after the hurricane, respectively, demonstrate the disproportionate influence this species likely had on carbon storage at localized scales prior to the widespread, selective harvesting of large P.strobus across the region in the 18th and 19th centuries.

Hemlock: A Forest Giant on the Edge ed. by David R. Foster

Reviewed by: Hemlock: A Forest Giant on the Edge ed. by David R. Foster Brenden E. McNeil Hemlock: A Forest Giant on the Edge David R. Foster (editor). Yale University Press. New Haven, CT, 2014. 336 pp. maps, diagrs., photos, notes, bibliog., and index. $40 hardcover (ISBN 978-0-3001-7938-5) If a famous tree could tell us its story and offer its wisdom, it might read something like Hemlock. Few trees or stands of trees in the world might merit such a book-length biography, and the arc of many of those biopics could perhaps trace the relation of a tree to the development of a religion. Just as a hallowed fig tree in Bodh Gaya could shed light on the birth of Buddhism, or groves of olive trees around Jerusalem could add color to the chapters of early Christianity, there exists a set of hemlock [End Page 390] stands in central New England that offer witness to a budding science of resiliency. Fusing forestry, biogeography, environmental history, and ecology, Hemlock brings scientific enlightenment that casts its light far beyond the cathedral-like canopies of its subjects on the Harvard Forest in central New England. Indeed, these trees, and their interlocutors at Harvard Forest tell a tale that we all would do well to hear as we contemplate the Anthropocene. Devoid of the typical trappings and jargon of academic literature, this creatively structured and carefully edited book cleanly reads as a general-audience oriented story of curiosity and discovery. Those of us with an academic bent to their reading will be thankful that the team of Harvard Forest-based authors have also penned a parallel set of highly useful and engaging bibliographic essays. I certainly encourage you to read (and perhaps assign to your students) both these parallel stories within this fascinating, timely, and gorgeous book. To help you decide whether to spend some time with Hemlock, my review proceeds by answering three questions that you may have: First, why hemlock? Second, why read this book now? And finally, in telling the story of a species whose range covers much of eastern North America, what is gained by focusing on just several stands of hemlock in central New England? Surely, Hemlock is partly homage to the tree itself. Beautiful and ecologically important, eastern hemlock (Tsuga canadensis) is an old friend to those of us who love the forests of eastern North America. Its shady evergreen canopy forms forest cathedrals on streambanks and mountaintops from Nova Scotia to Alabama and Maryland to Minnesota. As described in rich scientific and poetic turns (including a lovely chapter epigraph from Longfellow) within the book's second chapter, David Orwig summarizes reams of scientific literature documenting how the special adaptations of hemlock set it apart from other species in the eastern forest. For instance, he describes how hemlocks fundamentally alter the physiology of their ecosystem, often in fascinating and paradoxical ways. By being miserly with their water loss, hemlocks create wet environments that hold snow and water in their deeply shaded and rich forest floor. In the fifth chapter, Aaron M. Ellison and Benjamin H. Baiser convincingly argue that all these adaptations make hemlock a foundation species, which, if lost, would fundamentally change the ecosystem. And this is crucial, because this is exactly what is happening. The book's subtitle, A Forest Giant on the Edge, points toward the ongoing range-wide decline of hemlock at the hands, or indeed the stylet, of the parasitic hemlock woolly adelgid insect. Since it hitched a ride across an ocean and a continent in 1951 on a Japanese hemlock bound for a tree nursery in Virginia (p. 124), this invasive insect has spread rapidly, infesting and killing hemlocks from Maine to Georgia. Especially as climate change reduces the frequency of cold winter temperatures that can slow the insect's march, we do not know of any way to stop its spread. Many have lamented the loss of the hemlock, and the book's editor, David Foster writes a thoughtful lament in the epilogue. This bookends nicely with Hemlock's forward, an entertaining piece written by Robert Sullivan, sections of which also appeared in the top environmental...

Límites e interfaces de Chachapoyas en la región Rodríguez De Mendoza

Chachapoyas was one of the largest prehispanic cultures located in the eastern montane forest. The location on the interface of Andean and Amazonian environments gave middle-man status in trading important exotic goods withneighbors. The nature of the interface with the Chachapoyanos eastern neighbors speaks to important aspects of Chachapoya identity in the past. If Chachapoyas was an extension of highland cultural hegemony, then the eastern Chachapoyas interface may have been an important location for boundary maintenance between «Andean» and «Amazonian» peoples. Conversely, the Chachapoya may have been a bridge society that facilitated interaction by presenting a mutually intelligible venue for exchange. The LIP sites in the Mendoza region share many characteristics with typical Chachapoya sites: settlement pattern; pottery styles; and mortuary style, but Mendoza sites lack elaboration of household architecture, such as cornices, friezes, tenon heads, or platform bases, and these sites do not have the same density of stone constructions as documented at most “Classic” Chachapoya sites. This article reviews survey of Mendoza area habitation sites, mortuary sites, and pathways of movement as part of a network of local, regional, and interregional connections to consider what Mendoza sites can tell us about the construction of what was «Chachapoyas.»

Quantifying the Accuracy of LiDAR-Derived DEM in Deciduous Eastern Forests of the Cumberland Plateau

Digital elevation models (DEMs) derived from light detection and ranging (LiDAR) technology are becoming the standard in representing terrain surfaces. They have numerous applications in forestry, agriculture, and natural resources. Although elevation errors are much lower than those derived from traditional methods, accuracies have been reported to decrease with terrain slope and vegetation cover. In this study, we quantified the accuracy of airborne LiDAR-derived DEM in deciduous eastern forests of the Cumberland Plateau. We measured relative elevation changes within field plots located across different slope and ruggedness classes to quantify DEM accuracy. We compared elevation change errors of DEMs derived from three LiDAR datasets: a low-density (~1.5 pts•m−2), a high-density (~40 pts•m−2), and a combined dataset. We also compared DEMs obtained by interpolating the ground points using four interpolation methods. Results indicate that mean elevation change error (MECE) increased with terrain slope and ruggedness with an average of 73.6 cm. MECE values ranged from 23.2 cm in areas with lowest slope (0% - 39%) and ruggedness (0% - 28%) classes to 145.5 cm in areas with highest slope (50% - 103%) and ruggedness (46% - 103%) classes. We found no significant differences among interpolation methods or LiDAR datasets; the latter of which indicates that similar accuracy levels can be achieved with the low-density datasets.

Integration of Vegetation Community Spatial Data into a Prescribed Fire Planning Process at Shenandoah National Park, Virginia (USA)

ABSTRACT: Many eastern forest communities depend on fire for regeneration or are enhanced by fire as a restoration practice. However, the use of prescribed fire in the mesic forested environments and the densely populated regions of the eastern United States has been limited. The objective of our research was to develop a science-based approach to prioritizing the use of prescribed fire in appropriate forest types in the eastern United States based on a set of desired management outcomes. Through a process of expert elicitation and data analysis, we assessed and integrated recent vegetation community mapping results along with other available spatial data layers into a spatial prioritization tool for prescribed fire planning at Shenandoah National Park (Virginia, USA). The integration of vegetation spatial data allowed for development of per-pixel priority rankings and exclusion areas enabling precise targeting of fire management activities on the ground, as well as a park-wide ranking of fire planning co...

Elevated light levels reduce hemlock woolly adelgid infestation and improve carbon balance of infested eastern hemlock seedlings

The rapid loss of eastern hemlock (Tsuga canadensis) due to infestation with hemlock woolly adelgid (Adelges tsugae, HWA) has greatly altered structure and function of eastern forests. Numerous control strategies including local pesticide use and biocontrol with predator beetles have been implemented with considerable cost and varying success. Silviculture treatments that increase incident light on surviving hemlock trees to reduce infestation and ameliorate carbon starvation have been proposed as another possible conservation strategy, yet no controlled studies have evaluated the coupled plant-insect responses to increased light. We conducted a nursery experiment on artificially infested eastern hemlock seedlings under varying levels of ambient light, ranging from 0 to 90% shade. We measured HWA infestation (ovisac density), short- and long-term indicators of carbon balance (leaf chlorophyll fluorescence, net photosynthesis, total nonstructural carbohydrate content, and shoot growth), and nutrition (leaf N content). We hypothesized that higher light would result in reduced HWA densities, higher C assimilation rates, and improved tissue non-structural carbohydrate balance; and these effects would ameliorate the effects of infestation on C balance and lead to improved seedling growth. HWA density decreased with increasing light, and was highest in the 90% shade treatments. However, photosystem II efficiency and net assimilation were also lower under the higher light treatment. Despite tradeoffs between reduced infestation and reduced leaf function from higher light, and little variation in sugar content among treatments, both leaf and root starch content and seedling growth were higher under the higher light treatment. Increasing light levels improves long-term carbon balance for hemlock seedlings in the presence of HWA. Although hemlock typically occurs in deeply shaded forests, our results suggest that silvicultural treatments such as forest thinning that increase light exposure may reduce HWA abundance and lead to better tree C balance, and may be an effective component of large-scale conservation and restoration strategies.

Diversity and distribution character of wood-rotting fungi in the secondary forest ecosystem of Liaodong areas, Northeast China

During July to September of 2013, field investigations and specimen collections on wood-rotting fungi were carried from three sites in the secondary forests (Qingyuan forest farm, Laotudingzi National Nature Reserve and Baishilaizi Nature Reserve) of eastern Liaoning Province. A total of 1062 specimens were collected and recorded, and 92 species were identified, belonging to48 genera. Among the three studying sites, Baishilaizi Nature Reserve had the most abundant polypore species and the Shannon diversity index was 4.04. The species biogeography of eastern Liaoning could be divided into 4 groups at genus level. The main elements were North temperate element and cosmopolitan element, and floristic analysis showed a distinct north temperate character. White rot species were the dominant decomposers here. Most species distributed in the fallen wood with decay stages 2 and 3. The wood dominant hosts of wood-rotting fungi were the Acer genus in the secondary forests of eastern Liaoning Province, and 243 specimens were collected from maples, occupying 23.2% of the total.

New species and species reports of Croton L. (Euphorbiaceae) from the eastern forest corridor of Madagascar

Abstract Kainulainen, K., B. Van EE, P. Antilahimena, H. Razafindraibe & P.E.Berry (2016). New species and species reports of Croton L. (Euphorbiaceae) from the eastern forest corridor of Madagascar. Candollea 71: 327–356. In English, English and French abstracts. Six species of Croton from the Moramanga District of the Alaotra-Mangoro Region of eastern Madagascar (Toamasina Prov.) are newly described here, five of which occur in the Ambatovy mining concession. A seventh new species is described from the Ankerana Forest in the Atsinanana Region, some 80 km to the northeast of the town of Moramanga, which is one of the offset areas intended to mitigate the deforestation incurred by the Ambatovy mining project. Of the new species, Croton ferricretus Kainul., B.W. van Ee & P.E. Berry is the one most closely associated with the ultramafic soils where nickel and cobalt is being extracted. Although it is locally common, it is only known from the mine concession. Croton enigmaticus P.E. Berry & B.W. van Ee is co...

Improved accuracy of aboveground biomass and carbon estimates for live trees in forests of the eastern United States

Accurate estimation of forest biomass and carbon stocks at regional to national scales is a key requirement in determining terrestrial carbon sources and sinks on United States (US) forest lands. To that end, comprehensive assessment and testing of alternative volume and biomass models were conducted for individual tree models employed in the component ratio method (CRM) currently used in the US' National Greenhouse Gas Inventory. The CRM applies species-specific stem volume equations along with specific gravity conversions and component expansion factors to ensure consistency between predicted stem volumes and weights, and additivity of predicted live tree component weights to match aboveground biomass (AGB). Data from over 76 600 stem volumes and 6600 AGB observations were compiled from individual studies conducted in the past 115 years – what we refer to as legacy data – to perform the assessment. Scenarios formulated to incrementally replace constituent equations in the CRM with models fitted to legacy data were tested using cross-validation methods, and estimates of AGB were scaled using forest inventory data to compare across 33 states in the eastern US. Modifications all indicated that the CRM in its present formulation underestimates AGB in eastern forests, with the range of underestimation ranging from 6.2 to 17 per cent. Cross-validation results indicated the greatest reductions in estimation bias and root-mean squared error could be achieved by scenarios that replaced stem volume, sapling AGB, and component ratio equations in the CRM. A change in the definitions used in apportioning biomass to aboveground components was also shown to increase prediction accuracy. Adopting modifications tested here would increase AGB estimates for the eastern US by 15 per cent, accounting for 1.5 Pg of C currently unaccounted for in live tree aboveground forest C stock assessments. Expansion of the legacy data set currently underway should be useful for further testing, such as whether similar gains in accuracy can be achieved in estimates of regional or national-scale C sequestration rates.

The diet of Cerulean Warbler (Setophaga cerulea) nestlings and adult nest provisioning behaviors in southern Indiana

ABSTRACT We studied the diet of nestling Cerulean Warblers (Setophaga cerulea) and the provisioning behaviors of parents in southern Indiana. The Cerulean Warbler, a small insectivorous passerine breeding in eastern North American deciduous forests, is one of the fastest declining Neotropical wood warblers. Our primary objectives were to determine the importance of specific prey items in the diet of nestling Cerulean Warblers, and to assess whether the proportion of lepidopteran larvae (caterpillars) in the diet changed during the breeding season. We also describe general nest provisioning behavior, including differences between females and males, and assess breeding success across years. We video-taped provisioning behavior to determine the prey types (insects and arachnids) that parent Cerulean Warblers fed their young during the breeding season in 2013 and compared the proportions of lepidopteran larvae in the diet to that in the environment. The proportion of lepidopteran larvae in the nestling diet w...

Sowing the Seeds of Fire and Oak in the Eastern US: A Tribute to Buell et al. 1954

A 323-year-old white oak (Quercus alba L.) tree in Mettler’s Woods in central New Jersey, USA, was the subject of the Buell et al. 1954 paper. They identified six fire scars formed between 1641 and 1711, with a mean fire return interval of 8.6 years over this period. The fires were primarily associated with narrow rings, which are indicative of drought years. The cessation of fire scars occurred shortly after European settlement. The results of this groundbreaking study provided the first estimate of pre-European settlement fire history for mid-Atlantic oak forests and evidence that these fires were a function of Native American burning combined with drought years. The authors proposed that oak and hickory establishment (forming distinct age cohorts) was associated with recurring fire, that European settlement corresponded to reduced burning in some Eastern forests, that the cessation of burning might impact oak-hickory forest dynamics, and that old-growth forests should be preserved and studied for ecological purposes.

Recovery dynamics and climate change effects to future New England forests

Forests throughout eastern North America continue to recover from broad-scale intensive land use that peaked in the nineteenth century. These forests provide essential goods and services at local to global scales. It is uncertain how recovery dynamics, the processes by which forests respond to past forest land use, will continue to influence future forest conditions. Climate change compounds this uncertainty. We explored how continued forest recovery dynamics affect forest biomass and species composition and how climate change may alter this trajectory. Using a spatially explicit landscape simulation model incorporating an ecophysiological model, we simulated forest processes in New England from 2010 to 2110. We compared forest biomass and composition from simulations that used a continuation of the current climate to those from four separate global circulation models forced by a high emission scenario (RCP 8.5). Simulated forest change in New England was driven by continued recovery dynamics; without the influence of climate change forests accumulated 34 % more biomass and succeed to more shade tolerant species; Climate change resulted in 82 % more biomass but just nominal shifts in community composition. Most tree species increased AGB under climate change. Continued recovery dynamics will have larger impacts than climate change on forest composition in New England. The large increases in biomass simulated under all climate scenarios suggest that climate regulation provided by the eastern forest carbon sink has potential to continue for at least a century.

Evaluation of FOFEM Fuel Loads and Consumption Estimates in Pine-Oak Forests and Woodlands of the Ouachita Mountains in Arkansas, USA

Accurate fuel load and consumption predictions are important to estimate fire effects and air pollutant emissions. The FOFEM (First Order Fire Effects Model) is a commonly used model developed in the western United States to estimate fire effects such as fuel consumption, soil heating, air pollutant emissions, and tree mortality. However, the accuracy of the model in the eastern United States has not been well tested. As a result, managers are turning to locally collected data sets from eastern forests to improve the accuracy of FOFEM and other models. FOFEM lacks local fuel load and consumption data for the Ouachita Mountains, an area with nearly 50,000 ha prescribe burned annually. In this study, we compared fuel loads and consumption using field-collected data with data predicted by FOFEM. We determined fuel loads before and after 15 prescribed fires by sampling live fuels, down woody debris, litter, and duff in three cover types (oak forest, pine-oak forest, and pine woodland) on the Ouachita National Forest in Arkansas. Default estimates of litter and duff fuel load in FOFEM were up to 346 and 1,307% greater than field estimates, respectively. FOFEM estimates of 10-hour, 1-hour, and litter fuel consumption were up to 182, 150, and 46% greater, respectively, than field-measured consumption. These overestimations of fuel load and consumption could result in overpredictions of air pollutant emissions and reduce the area of habitat restored and maintained by prescribed burning as fire managers seek to comply with air quality standards.

Tree diversity, tree height and environmental harshness in eastern and western North America.

Does variation in environmental harshness explain local and regional species diversity gradients? We hypothesise that for a given life form like trees, greater harshness leads to a smaller range of traits that are viable and thereby also to lower species diversity. On the basis of a strong dependence of maximum tree height on site productivity and other measures of site quality, we propose maximum tree height as an inverse measure of environmental harshness for trees. Our results show that tree species richness is strongly positively correlated with maximum tree height across multiple spatial scales in forests of both eastern and western North America. Maximum tree height co-varied with species richness along gradients from benign to harsh environmental conditions, which supports the hypothesis that harshness may be a general mechanism limiting local diversity and explaining diversity gradients within a biogeographic region.