Eastern Forests Research Articles

Effects of fire and its severity on occupancy of bats in mixed pine-oak forests

Prescribed burning has become more common for the management of eastern forests in North America, so understanding if and how foraging bats respond to structural changes generated by fire is of increasing importance. Our objective was to investigate the effects of post-fire landscape conditions on the occurrence of foraging bats in mixed forests of the Cumberland Plateau physiographic region. We deployed Anabat II bat detectors in 164 paired burned and unburned forest sites for ≥2 nights from mid-May through August 2014 and 2015 to monitor bat foraging and commuting habitat use. We conducted vegetation surveys to quantify site-specific structural characteristics, which indicated that measures of structure were significantly lower in burned sites than unburned sites. We used Program Presence to test a priori hypotheses of species-specific probability of detection and site occupancy related to weather, burn history (i.e., site burned within the past 10 years or unburned), and site and landscape characteristics. Bats were detected at 94% of burned sites and 83% of unburned sites. Probability of detection was affected by weather conditions, vegetative structure, and burn history for most species. Occupancy for all species/species groups examined was positively associated with burning and generally associated with lower vegetative structure. Although burn severity did not affect most species groups, occupancy of Myotis species and tri-colored bats (Perimyotis subflavus) was lower in sites that received moderate severity burns than in sites that received low severity burns. Therefore, while prescribed fire may provide vegetative structure conducive to efficient foraging for all bats of the Cumberland Plateau, our results demonstrate that retaining some unburned forests while creating mosaics of lower and higher severity burns across the landscape will result in favorable foraging conditions for all resident bat species.

Sessile oak forest plant community changes on the NE Iberian Peninsula over recent decades

AbstractAimsOur aims were 3-fold: (i) to determine whether global change has altered the composition and structure of the plant community found in the sessile oak forests on the NE Iberian Peninsula over the last decades, (ii) to establish whether the decline in forest exploitation activities that has taken place since the mid-20th century has had any effect on the forests and (iii) to ascertain whether there is any evidence of impact from climate warming.MethodsWe assess changes in the plant community by comparing a current survey of sessile oak forest with a historical data set obtained from previous regional studies dating from 1962 to 1977. We analyse the regional changes in the community in terms of biodiversity variables, species composition and plant traits. Furthermore, plants traits such as plant life forms and chorological groups are used to discern any effects from land-use changes and climate warming on the plant community.Important FindingsThere has been a loss of diversity in the community and, in the hottest region, there is also a loss of species richness. The composition of the community suggests that, although significant changes have taken place over recent decades, these changes differ between regions as a result of the low impact global change has had in the western regions. For instance, while the tree canopy cover in the western sessile oak forests remains stable, the eastern sessile oak forests are still recovering from the former exploitation that led to a loss of their rich and abundant herbaceous stratum. In fact, the recovery process in the Catalan Pre-Coastal Range has constituted an increase in the Euro-Siberian plants typical to this community. Moreover, in the eastern forests, there is evidence that climate warming has impacted the thermophilization of the sessile oak forests found on the Coastal Range.

Spatial variation of correlations between vertical soil water and evapotranspiration and their controlling factors in a semi-arid region

A decrease in soil water content (SWC) has been observed at the global scale and has led to a reduction in evapotranspiration (ET). However, the trend in SWC in eastern Asia differed from the global trend, and this may be due to the overlapping of warm/wet seasons. Because of the limitation of deep soil water content data, especially in drylands, changes in SWC and the correlation between SWC (particularly deep SWC) and ET remain poorly understood. In this study, spatial distribution of correlation coefficient (r) between SWC and ET were calculated based on reanalysis data and remote sensing data, which were validated by in situ data (2004–2005) and sampling data (2016–2017). Firstly, the correlation between SWC and ET decreased with soil depth. The depth of the sharp decrease was 10 cm based on in situ monitoring data (2005–2008) and spatial sampling data (2016–2017). Secondly, the spatial correlation between SWC and ET varied with different vegetation cover types. The correlation increased from the western typical steppe to the eastern forest. The highest values of r were in a forest-covered area, because it had the highest water uptake capacity. However, the difference between r_10 and r_100 (D_r) showed a different spatial pattern, and the lowest negative D_r value was obtained from a forest–grass transition zone in which the enhanced vegetation index showed a significant increasing trend. The significant negative regression determination coefficient (R2 = 0.9, p < 0.01) between B_EVI (0–0.1) and D_r indicated that the narrowed D_r in the transition zone was due to the vegetation increase. This meant that more deep soil water was taken up into the atmosphere. Thus, the deep SWC could become unstable and deep soil could become drier, which would be unsustainable for the ecosystem.

Ponderosa Pine Regeneration, Wildland Fuels Management, and Habitat Conservation: Identifying Trade-Offs Following Wildfire

Increasing wildfires in western North American conifer forests have led to debates surrounding the application of post-fire management practices. There is a lack of consensus on whether (and to what extent) post-fire management assists or hinders managers in achieving goals, particularly in under-studied regions like eastern ponderosa pine forests. This makes it difficult for forest managers to balance among competing interests. We contrast structural and community characteristics across unburned ponderosa pine forest, severely burned ponderosa pine forest, and severely burned ponderosa pine forest treated with post-fire management with respect to three management objectives: ponderosa pine regeneration, wildland fuels control, and habitat conservation. Ponderosa pine saplings were more abundant in treated burned sites than untreated burned sites, suggesting increases in tree regeneration following tree planting; however, natural regeneration was evident in both unburned and untreated burned sites. Wildland fuels management greatly reduced snags and coarse woody debris in treated burned sites. Understory cover measurements revealed bare ground and fine woody debris were more strongly associated with untreated burned sites, and greater levels of forbs and grass were more strongly associated with treated burned sites. Wildlife habitat was greatly reduced following post-fire treatments. There were no tree cavities in treated burned sites, whereas untreated burned sites had an average of 27 ± 7.68 cavities per hectare. Correspondingly, we found almost double the avian species richness in untreated burned sites compared to treated burned sites (22 species versus 12 species). Unburned forests and untreated burned areas had the same species richness, but hosted unique avian communities. Our results indicate conflicting outcomes with respect to management objectives, most evident in the clear costs to habitat conservation following post-fire management application.

Prescribed Fire Effects on Water Quality and Freshwater Ecosystems in Moist-Temperate Eastern North America

Forests of the eastern United States provide numerous ecosystem services, including water filtration. Forest management activities of eastern forests often include prescribed fire to accomplish a variety of management objectives such as invasive species control, wildlife habitat improvement, ecosystem restoration, and hazardous fuel reduction. Despite widespread use of prescribed fire in this region and the need to maintain adequate water quality from forests impacted by this practice, there is a paucity of knowledge on prescribed fire's impacts on water quality. This article summarizes and consolidates known impacts of prescribed fire on chemical, physical, and biological properties related to water quality and freshwater ecosystems in moist-temperate eastern North America, including impacts on drinking water treatability. Based upon this synthesis, it appears that most prescribed fires in eastern forests are low intensity and low severity and cause minimal changes to forest soil properties, leading to minimal adverse impacts that might exacerbate soil erosion and adversely affect surface waters. In some cases, prescribed fire has been shown to enhance water quality in the region. Technological advancements in monitoring fire behavior have the potential to advance our knowledge regarding the effects of prescribed fire on water quality in the eastern forest region, particularly for fires of mixed or moderate severity and fires occurring in complex terrain.

Trajectory from beech and oak forests to eastern broadleaf forests in Indiana, USA

BackgroundHistorical forests (circa 1799 to 1846) of Indiana were predominantly composed of American beech (25% of all trees) and upland oaks (27% of all trees). I compared historical forest composition, using studies of smaller areas to approximate composition for uncommon species or genera (< 4.5% of all trees) and forest types, to current forest composition and forest types in Indiana. I also compiled published historical density estimates from small studies and estimated current density for the state.ResultsCurrent forests are diverse with an even composition of many eastern broadleaf species. In addition to upland oaks, which decreased to 13% of all trees, only sugar maple currently comprises greater than 10% of all trees. Other increasing species were yellow-poplar, red maple, black cherry, and eastern redcedar. Eastern redcedar increased from no presence to one of the most abundant ten species (≥ 3.5% of composition), similarly to the pine genus, becoming more common currently than American beech. Beech or oak or beech-oak forest types (≥ 24% of all trees) became eastern broadleaf forests, with no dominant species, and black cherry, red maple, and eastern redcedar forest types now occurred. Estimates of historical oak or beech forests ranged from 28 trees per hectare to 175 trees per hectare, which probably represent savannas and woodlands. Current mean density of Indiana forests is 385 trees per hectare, ranging from 180 trees per hectare to 450 trees per hectare. These forests likely contain dense layers of woody vegetation, filling the midstory and replacing herbaceous vegetation in the ground layer.ConclusionHistorically dominant beech and oak forests in the eastern United States have transitioned to an alternative state of closed eastern broadleaf forests due to uncontrolled establishment of many tree species.

A Cryptic New Species of Polemon (Squamata: Lamprophiidae, Aparallactinae) from the Miombo Woodlands of Central and East Africa

African snake-eaters of the genus Polemon are cryptic, fossorial snakes that mainly inhabit the forests of central, eastern, and western Africa. Molecular results from a previous study demonstrated that Polemon christyi is not monophyletic—two distinct lineages were recovered from Uganda (the type locality) and southeastern Democratic Republic of the Congo (DRC). Genetic data indicated differences in sequence divergence and encoded amino acids between these lineages. Based on these molecular differences and diagnostic differences in morphology, we describe the lineage from southeastern DRC as a new species. Literature records indicate that it likely occurs in adjacent Tanzania and Zambia. It is the first species of Polemon to be described in over 70 years.

УРОЖАЙНІСТЬ КВАСОЛІ ЗАЛЕЖНО ВІД НОРМИ ВИСІВУ НАСІННЯ В СХІДНОМУ ЛІСОСТЕПУ УКРАЇНИ

УРОЖАЙНІСТЬ КВАСОЛІ ЗАЛЕЖНО ВІД НОРМИ ВИСІВУ НАСІННЯ В СХІДНОМУ ЛІСОСТЕПУ УКРАЇНИ

Exploring variation in phyllosphere microbial communities across four hemlock species

AbstractThe hemlock woolly adelgid (HWA) is an insect native to Asia and likely western North America. First reported in eastern North America in 1951, it has devastated eastern hemlock (Tsuga canadensis) populations. Loss of hemlock will greatly affect the structure and function of eastern forests. Susceptibility to adelgid infestation varies within eastern hemlocks and across other hemlock species. Our study was conducted to determine whether eastern hemlocks share a similar stem (phyllosphere) microbial community with other co‐occurring hemlocks and whether community‐level shifts are associated within trees of the same species based on HWA infestation. Surprisingly, we found no difference in microbial community composition or diversity between trees of the same species based on the level of HWA infestation. However, microbial communities varied significantly across the four hemlock trees sampled, native T. canadensis and three non‐natives: Tsuga chinensis, Tsuga dumosa, and Tsuga sieboldii. Within these tree hosts, microbial communities from T. dumosa and T. chinensis clustered together, and microbial communities from T. canadensis and T. sieboldii clustered separately from all other tree species. Additionally, specific indicator taxa were identified for all the tree species sampled. These results indicate that Asian hemlocks might not fill the same niche in eastern forests as the native eastern hemlock. Further work should be conducted to determine how differences in hemlock species and associated microbial communities might scale up to alter organismal interactions involving hemlocks.

Climatic synchrony and increased outbreaks in allopatric populations of an invasive defoliator

Larch casebearer is an invasive defoliator in North America distributed within the regions of two allopatric hosts, eastern larch and western larch. Despite the establishment of a successful importation biological control program and ongoing parasitism by both native and introduced parasitoids, larch casebearer has recently undergone outbreaks on eastern larch and western larch. We analyzed defoliation data from aerial surveys to quantify spatiotemporal synchrony and found that defoliation by larch casebearer was synchronous both within and between eastern and western larch forests. We also analyzed monthly minimum temperatures across the study region and found that warming spring temperatures in March and cooling fall/winter temperatures in October through December were positively correlated at distances comparable to those between the allopatric outbreaks of larch casebearer. For allopatric populations with positively correlated population dynamics, climate is the most likely driver of synchrony. Thus, we suggest that a changing climate has facilitated recent outbreaks of larch casebearer.

Have some landscapes in the eastern Canadian boreal forest moved beyond their natural range of variability?

BackgroundIn the context of ecosystem management, the present study aims to compare the natural and the present-day forested landscapes of a large territory in Quebec (Canada). Using contemporary and long-term fire cycles, each natural forest landscape is defined according to the variability of its structure and composition, and compared to the present-day landscape. This analysis was conducted to address the question of whether human activities have moved these ecosystems outside the range of natural landscape variability.MethodsThe study encompassed a forested area of 175 000 km2 divided into 14 landscapes. Using a framework that integrates fire cycles, age structure and forest dynamics, we characterized the forest composition and age structures that resulted from three historical fire cycles (110, 140, and 180 years) representative of the boreal forest of eastern Canada. The modeled natural landscapes were compared with present-day landscapes in regard to the proportion of old-growth forests (landscape level) and the proportion of late-successional forest stands (landscape level and potential vegetation type).ResultsFour landscapes (39%) remain within their natural range of variability. In contrast, nine landscapes (54%) show a large gap between natural and present-day landscapes. These nine are located in the southern portion of the study area, and are mainly associated with Abies-Betula vegetation where human activities have contributed to a strong increase in the proportion of Populus tremuloides stands (early-successional stages) and a decrease of old-growth forest stands (more than 100 years old). A single landscape (7%), substantially changed from its potential natural state, is a candidate for adaptive-based management.ConclusionComparison of corresponding natural (reference conditions) and present-day landscapes showed that ten landscapes reflecting an important shift in forest composition and age structure could be considered beyond the range of their natural variability. The description of a landscape’s natural variability at the scale of several millennia can be considered a moving benchmark that can be re-evaluated in the context of climate change. Focusing on regional landscape characteristics and long-term natural variability of vegetation and forest age structure represents a step forward in methodology for defining reference conditions and following shifts in landscape over time.

Sharp Savanna-forest Transitions in the Midwest Followed Environmental Gradients but are Absent from the Modern Landscape

Historically, closed eastern forests transitioned into open savannas and prairies in the U.S. Midwest, but this transition is poorly understood. To investigate the eastern boundary of the prairie-forest ecotone, we conducted a case study of historic and modern vegetation patterns of the Yellow River watershed in northwest Indiana. Historic vegetation came from the Public Land Survey notes collected in the early 1800s, whereas modern vegetation came from the Forest Inventory Analysis and USGS National Land Cover Database. We mapped vegetation data using GIS to reconstruct the region's past and current forest composition and structure. We also mapped climate, topography, and soil composition across the watershed to investigate the relationship between historic vegetation and environmental gradients. We found a sharp transition in the presettlement forest structure and composition, with dense deciduous forests in the eastern portion of our study area and open oak savannas in the west. The savanna ecosystem dominated in sandy well-drained soils and was at a slightly lower elevation than the adjacent closed forest. Modest environmental changes accompanied major vegetation changes in the past, which might suggest fire and hydrological patterns helped maintain the sharp ecotone. By contrast the modern forest shows no difference in tree density and composition across the watershed, which is consistent with major land use and hydrology changes in the watershed since settlement. On the modern landscape, land that was historically closed forest now has higher agricultural productivity compared to land that was historically savanna, whereas the historic savanna currently supports more mesic forest. These results suggest the environmental gradient continues to subtly shape the landscape. Though land use change has largely removed the closed mixed hardwood forests and oak savannas from this area, a better understanding of the historic vegetation and the conditions that supported it can help inform land management and restoration, as well as reveal ecological processes that drive vegetation transitions.

Detection of Annual Spruce Budworm Defoliation and Severity Classification Using Landsat Imagery

Spruce budworm (SBW) is the most destructive forest pest in eastern forests of North America. Mapping annual current-year SBW defoliation is challenging because of the large landscape scale of infestations, high temporal/spatial variability, and the short period of time when detection is possible. We used Landsat-5 and Landsat-MSS data to develop a method to detect and map SBW defoliation, which can be used as ancillary or alternative information for aerial sketch maps (ASMs). Results indicated that Landsat-5 data were capable of detecting and classifying SBW defoliation into three levels comparable to ASMs. For SBW defoliation classification, a combination of three vegetation indices, including normalized difference moisture index (NDMI), enhanced vegetation index (EVI), and normalized difference vegetation index (NDVI), were found to provide the highest accuracy (non-defoliated: 77%, light defoliation: 60%, moderate defoliation: 52%, and severe defoliation: 77%) compared to using only NDMI (non-defoliated: 76%, light defoliation: 40%, moderate defoliation: 43%, and severe defoliation: 67%). Detection of historical SBW defoliation was possible using Landsat-MSS NDVI data, and the produced maps were used to complement coarse-resolution aerial sketch maps of the past outbreak. The method developed for Landsat-5 data can be used for current SBW outbreak mapping in North America using Landsat-8 and Sentinel-2 imagery. Overall, the work highlights the potential of moderate resolution optical remote sensing data to detect and classify fine-scale patterns in tree defoliation.

Intermittent development of forest corridors in northeastern Brazil during the last deglaciation: Climatic and ecologic evidence

The semi-arid northeastern (NE) Brazil vegetation is largely dominated by Caatinga, one of the largest and richest dry forests in the world. Caatinga is a strategic biome, since it has borders with Cerrado, Atlantic forests and the Amazon, acting as a potential corridor (or barrier) for biotic interchange between these regions during evolutionary times. Therefore, accurate reconstructions of past vegetation, ecological and hydrological changes in this area are critical to understanding the dynamics of biome boundaries that may play an important role in dispersal and diversification mechanisms and, more specifically, the link between the long-term climate variability and tropical biodiversity. Here, we present high-resolution palynological and elemental data from marine core GeoB16205-4 retrieved off the Parnaíba River mouth (NE Brazil) mainly covering the Younger Dryas (YD). We show that the YD interval was predominantly wet in NE Brazil, yet it was not homogenous and two distinct phases could be distinguished. A marked intensification of wet conditions between ∼12.3 and 11.6 cal kyr BP was recorded by the expansion of tropical rainforest and tree ferns. These results are in agreement with the transient TraCE-21k coupled climate model simulation. We infer that the second pluvial phase of the YD is related to a weak AMOC due to meltwater pulses in the North Atlantic, which forces a southward shift of the Intertropical Convergence Zone and its associated rainfall. Our records provide new evidence on the establishment of an “eastern forest corridor” in the nowadays semi-arid Caatinga allowing for past biotic interchanges of plant species.

Predicting the origins of next forest-based emerging infectious disease.

Land use change near dense forests is the single major cause of emergence of forest-based emerging infectious diseases (EIDs) among humans. In an attempt to predict where the next EID would originate from, we are hypothesizing that future EIDs would originate from a region having high population density, excessive poverty, and is located near dense vegetation. Using ArcGIS, we identified forest regions in ten countries across the globe that meet all the three conditions identified in the hypothesis. We further narrowed down the locations using Global Forest Watch data, which eliminates locations next to protected forests and fragmented forests. Our results indicate that there is high likelihood of next infectious disease originating from the southern and eastern forests around Freetown in Sierra Leone, the forest region around Douala in Cameroon, or the southern forest region in Nigeria. Concerted efforts need to be made to identify any new disease in the areas as soon as it emerges in the human population and contain the spread within the population.

Is increased precipitation during the 20th century statistically or ecologically significant in the eastern US?

ABSTRACTWe address the climate versus disturbance debate to understand drivers of change in human-environment systems. We examine whether recent increased precipitation episodes (‘pluvials’) are unique and have ecological implications for the humid climate of the eastern United States. Robust statistical analyzes presented here indicate that the 20th century was wet, but not significantly different than other centuries during the last millennium. Statistical methods did not establish increased precipitation episodes as an unusual change that correlated with transition shifts in eastern forests during the early 20th century. Additionally, modest precipitation change was not ecologically significant enough to result in forests composed of drought-tolerant trees in the past or drought-intolerant trees currently. We conclude that fire is a parsimonious explanation for composition and structure of historical open fire-tolerant oak and pine forests. Fire exclusion was unprecedented during early 20th century and loss of this driver provides a mechanism for forest transitions.

Restoration of Legacy Trees as Roosting Habitat for Myotis Bats in Eastern North American Forests

Most eastern North American Myotis roost in forests during summer, with species forming maternity populations, or colonies, in cavities or crevices or beneath the bark of trees. In winter, these bats hibernate in caves and are experiencing overwinter mortalities due to infection from the fungus Pseudogymnoascus destructans, which causes white-nose syndrome (WNS). Population recovery of WNS-affected species is constrained by the ability of survivors to locate habitats suitable for rearing pups in summer. Forests in eastern North America have been severely altered by deforestation, land-use change, fragmentation and inadvertent introduction of exotic insect pests, resulting in shifts in tree distributions and loss of large-diameter canopy-dominant trees. This paper explores patterns in use of tree roosts by species of Myotis across Canada and the United States using meta-data from published sources. Myotis in western Canada, the Northwest, and Southwest selected the largest diameter roost trees and also supported the largest maximum exit counts. Myotis lucifugus, M. septentrionalis and M. sodalis, three species that inhabit eastern forests and which are currently experiencing region-wide mortalities because of WNS, selected roosts with the smallest average diameters. Recovery efforts for bark- and cavity-roosting Myotis in eastern North American forests could benefit from management that provides for large-diameter trees that offer more temporally-stable structures for roosting during the summer maternity season.

Prescription side effects: Long-term, high-frequency controlled burning enhances nitrogen availability in an Illinois oak-dominated forest

Abstract Controlled burning is a common management technique used to control invasive understory plants and promote oak regeneration throughout the prairie-forest ecotone and across eastern deciduous forests. However, prescribed burning effects on oak forest and woodland soils remain largely unknown. As fire has significant and often disproportionate impacts on soil carbon (C), nitrogen (N), and phosphorus (P), evaluating the impacts of repeated, low-intensity prescribed burning on oak forest soil is fundamental for understanding and predicting burning effects on vegetation dynamics and ecosystem functions. The goal of this study was to evaluate relative changes in soil C and nutrient dynamics in response to three decades of annual, low-intensity controlled burning in an oak-dominated forest in northern Illinois. We found that annual burning increased soil organic and inorganic N availability and microbial biomass N. Burning also increased N cycling rates and N-degrading enzyme activity in the 5–15 cm soil layer. Surprisingly, annual burning had little effect on soil P pools and fluxes, likely due to intrinsically high soil P availability. Similarly, though total soil C increased, burning did not alter available C concentrations, microbial biomass C, C-degrading enzyme activities, or C mineralization rates. As such, annual burning created a positive feedback on inorganic N production, altering relationships among C, N, and P. In contrast with management goals, controlled burning often fails to enhance oak proliferation or decrease the abundance of invasive plants. As Eastern forests were historically N-limited, our study suggests a potential mechanism behind these restoration outcomes: frequent, low-intensity burning may produce soil environments that are incompatible with restoration goals.

Caterpillars of Eastern Forests. David L. Wagner, Valerie Giles, Richard C. Reardon and Michael L. McManus. 1997. USDA Forest Service FHTET-96-34, 113 pp., soft cover.

Caterpillars of Eastern Forests. David L. Wagner, Valerie Giles, Richard C. Reardon and Michael L. McManus. 1997. USDA Forest Service FHTET-96-34, 113 pp., soft cover.

Short-term changes in spatial distribution pattern of an herbivore in response to accumulating snow

Deep snow can reduce accessibility to vegetation and cover by herbivores by blanketing understory cover, yet simultaneously increase access to foliage at higher levels. Thus, snow depth fluctuation should lead to spatiotemporal variation in herbivore habitat use. We measured shifts in habitat use by snowshoe hare (Lepus americanus Erxleben, 1777) as a function of snow depth in an eastern Canadian boreal forest where snow depth often exceeds 1 m. We hypothesized that as snow accumulates, snowshoe hares shift from locations with dense vegetation just above ground to locations with dense vegetation higher above ground. We surveyed 58 km of transects over three winters and found 1954 hare tracks. We analyzed track counts as a response to a density index of low vegetation (0–1.5 m above ground), high vegetation (2–4 m above ground), predator tracks, and snow depth. We found more hare tracks in sites with dense high vegetation when snow was deeper, and more hare tracks in sites with dense low vegetation when snow was shallower. Predator track presence did not influence responses to snow depth. Snow depth dynamics can drive hare distribution, and in turn, introduce uncertainty in spatial distribution models for the species and possibly its interactions with predators.