Patterns and consequences of ice storms in forested Appalachian landscapes

Major ice storms deposit heavy loads of freezing rain on trees, causing intense disturbances in eastern North American forests. Two ice storms that affected southwestern Virginia in 1994 caused heaviest damage on windward mountain slopes (those facing southeast or east). Several processes may have contributed to aspect-related variations in ice accretion, including orographic effects on rainfall and influences of wind on twig-surface and raindrop thermodynamics. These topographic patterns in ice storm disturbance appear to be typical in the Appalachians. Another characteristic pattern is the confinement of damage to specific elevation zones. Elevational zonation was evident in forests of Virginia and New York that were affected by ice storms during 1998. Several factors, including tree size, wood strength, and canopy architecture, influence tree damage characteristics within stands. Small trees typically suffer bent or broken stems, and large trees usually sustain canopy damage. Toppling is most common in medium-size trees. Canopy damage is common in species with weak wood and straight boles, whereas toppling is more frequent among trees with stronger wood. Site factors, such as slope and soil depth, also affect damage patterns. Steep slopes and thin soils contribute to higher rates of toppling. Frequency of ice storm disturbance influences how significant these events are for vegetation dynamics. In the southern Appalachians, ice storms occur most frequently in eastern parts of the region, where subfreezing surface air becomes trapped against the mountains and creates conditions favorable for freezing rain. A dendrochronological analysis indicates that ice storms produce tree-ring signatures that may be useful for detecting fine-scale spatial variations in ice storm frequency. Forest modeling results suggest that periodic ice storms have significant long-term consequences for Appalachian forest dynamics. These disturbances may reduce species richness on xeric ridgetops and enhance richness on mesic sites, predictions consistent with theoretical expectations. They are also predicted to reduce the degree of compositional zonation along a topographic gradient of soil moisture and to promote increased Quercus importance over much of the landscape. Ice storms may be especially significant for promoting the maintenance of shade-intolerant species, such as Robinia pseudoacacia and Liriodendron tulipifera, on Appalachian landscapes

Biotic and spatial factors potentially explain the susceptibility of forests to direct hurricane damage

Background Ecologists continue to investigate the factors that potentially affect the pattern and magnitude of tree damage during catastrophic windstorms in forests. However, there still is a paucity of research on which trees are more vulnerable to direct damage by winds rather than being knocked down by the fall of another tree. We evaluated this question in a mixed hardwood–softwood forest within the Big Thicket National Preserve (BTNP) of southeast Texas, USA, which was substantially impacted by Hurricane Rita in September 2005. Results We showed that multiple factors, including tree height, shade-tolerance, height-to-diameter ratio, and neighborhood density (i.e., pre-Rita stem distribution) significantly explained the susceptibility of trees to direct storm damage. We also found that no single factor had pervasive importance over the others and, instead, that all factors were tightly intertwined in a complex way, such that they often complemented each other, and that they contributed simultaneously to the overall susceptibility to and patterns of windstorm damage in the BTNP. Conclusions Directly damaged trees greatly influence the forest by causing secondary damage to other trees. We propose that directly and indirectly damaged (or susceptible) trees should be considered separately when assessing or predicting the impact of windstorms on a forest ecosystem; to better predict the pathways of community structure reorganization and guide forest management and conservation practices. Forest managers are recommended to adopt a holistic view that considers and combines various components of the forest ecosystem when establishing strategies for mitigating the impact of catastrophic winds.Daehyun Kim was supported by the Research Resettlement Fund for the new faculty of Seoul National University

Fire History of the Appalachian Region: A Review and Synthesis

The importance of fire in shaping Appalachian vegetation has become increasingly apparent over the last 25 years. This period has seen declines in oak (Quercus) and pine (Pinus) forests and other fire-dependent ecosystems, which in the near-exclusion of fire are being replaced by fire-sensitive mesophytic vegetation. These vegetation changes imply that Appalachian vegetation had developed under a history of burning before the fire-exclusion era, a possibility that has motivated investigations of Appalachian fire history using proxy evidence. Here we synthesize those investigations to obtain an up-to-date portrayal of Appalachian fire history. We organize the report by data type, beginning with studies of high-resolution data on recent fires to provide a context for interpreting the lower-resolution proxy data. Each proxy is addressed in a subsequent chapter, beginning with witness trees and continuing to fire-scarred trees, stand age structure, and soil and sediment charcoal. Taken together, these proxies portray frequent burning in the past. Fires had occurred at short intervals (a few years) for centuries before the fire-exclusion era. Indeed, burning has played an important ecological role for millennia. Fires were especially common and spatially extensive on landscapes with large expanses of oak and pine forest, notably in the Ridge and Valley province and the Blue Ridge Mountains. Burning favored oak and pine at the expense of mesophytic competitors, but fire exclusion has enabled mesophytic plants to expand from fire-sheltered sites onto dry slopes that formerly supported pyrogenic vegetation. These changes underscore the need to restore fire-dependent ecosystems

Integrating Agriculture and Ecosystems to Find Suitable Adaptations to Climate Change

Climate change is altering agricultural production and ecosystems around the world. Future projections indicate that additional change is expected in the coming decades, forcing individuals and communities to respond and adapt. Current research efforts typically examine climate change effects and possible adaptations but fail to integrate agriculture and ecosystems. This failure to jointly consider these systems and associated externalities may underestimate climate change impacts or cause adaptation implementation surprises, such as causing adaptation status of some groups or ecosystems to be worsened. This work describes and motivates reasons why ecosystems and agriculture adaptation require an integrated analytical approach. Synthesis of current literature and examples from Texas are used to explain concepts and current challenges. Texas is chosen because of its high agricultural output that is produced in close interrelationship with the surrounding semi-arid ecosystem. We conclude that future effect and adaptation analyses would be wise to jointly consider ecosystems and agriculture. Existing paradigms and useful methodology can be transplanted from the sustainable agriculture and ecosystem service literature to explore alternatives for climate adaptation and incentivization of private agriculturalists and consumers. Researchers are encouraged to adopt integrated modeling as a means to avoid implementation challenges and surprises when formulating and implementing adaptation

Advancing dendrochronological studies of fire in the United States

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. Dendroecology is the science that dates tree rings to their exact calendar year of formation to study processes that influence forest ecology (e.g., Speer 2010 [1], Amoroso et al., 2017 [2]). Reconstruction of past fire regimes is a core application of dendroecology, linking fire history to population dynamics and climate effects on tree growth and survivorship. Since the early 20th century when dendrochronologists recognized that tree rings retained fire scars (e.g., Figure 1), and hence a record of past fires, they have conducted studies worldwide to reconstruct [2] the historical range and variability of fire regimes (e.g., frequency, severity, seasonality, spatial extent), [3] the influence of fire regimes on forest structure and ecosystem dynamics, and [4] the top-down (e.g., climate) and bottom-up (e.g., fuels, topography) drivers of fire that operate at a range of temporal and spatial scales. As in other scientific fields, continued application of dendrochronological techniques to study fires has shaped new trajectories for the science. Here we highlight some important current directions in the United States (US) and call on our international colleagues to continue the conversation with perspectives from other countries

Identification of metabolic pathways influenced by the G-protein coupled receptors GprB and GprD in Aspergillus nidulans

Heterotrimeric G-protein-mediated signaling pathways play a pivotal role in transmembrane signaling in eukaryotes. Our main aim was to identify signaling pathways regulated by A. nidulans GprB and GprD G-protein coupled receptors (GPCRs). When these two null mutant strains were compared to the wild-type strain, the DeltagprB mutant showed an increased protein kinase A (PKA) activity while growing in glucose 1% and during starvation. In contrast, the DeltagprD has a much lower PKA activity upon starvation. Transcriptomics and (1)H NMR-based metabolomics were performed on two single null mutants grown on glucose. We noted modulation in the expression of 11 secondary metabolism gene clusters when the DeltagprB and DeltagprD mutant strains were grown in 1% glucose. Several members of the sterigmatocystin-aflatoxin gene cluster presented down-regulation in both mutant strains. The genes of the NR-PKS monodictyphenone biosynthesis cluster had overall increased mRNA accumulation in DeltagprB, while in the DeltagprD mutant strain the genes had decreased mRNA accumulation. Principal component analysis of the metabolomic data demonstrated that there was a significant metabolite shift in the DeltagprD strain. The (1)H NMR analysis revealed significant expression of essential amino acids with elevated levels in the DeltagprD strain, compared to the wild-type and DeltagprB strains. With the results, we demonstrated the differential expression of a variety of genes related mainly to secondary metabolism, sexual development, stress signaling, and amino acid metabolism. We propose that the absence of GPCRs triggered stress responses at the genetic level. The data suggested an intimate relationship among different G-protein coupled receptors, fine-tune regulation of secondary and amino acid metabolisms, and fungal development

The North American tree-ring fire-scar network

Fire regimes in North American forests are diverse and modern fire records are often too short to capture important patterns, trends, feedbacks, and drivers of variability. Tree-ring fire scars provide valuable perspectives on fire regimes, including centuries-long records of fire year, season, frequency, severity, and size. Here, we introduce the newly compiled North American tree-ring fire-scar network (NAFSN), which contains 2562 sites, >37,000 fire-scarred trees, and covers large parts of North America. We investigate the NAFSN in terms of geography, sample depth, vegetation, topography, climate, and human land use. Fire scars are found in most ecoregions, from boreal forests in northern Alaska and Canada to subtropical forests in southern Florida and Mexico. The network includes 91 tree species, but is dominated by gymnosperms in the genus Pinus. Fire scars are found from sea level to >4000-m elevation and across a range of topographic settings that vary by ecoregion. Multiple regions are densely sampled (e.g., >1000 fire-scarred trees), enabling new spatial analyses such as reconstructions of area burned. To demonstrate the potential of the network, we compared the climate space of the NAFSN to those of modern fires and forests; the NAFSN spans a climate space largely representative of the forested areas in North America, with notable gaps in warmer tropical climates. Modern fires are burning in similar climate spaces as historical fires, but disproportionately in warmer regions compared to the historical record, possibly related to under-sampling of warm subtropical forests or supporting observations of changing fire regimes. The historical influence of Indigenous and non-Indigenous human land use on fire regimes varies in space and time. A 20th century fire deficit associated with human activities is evident in many regions, yet fire regimes characterized by frequent surface fires are still active in some areas (e.g., Mexico and the southeastern United States). These analyses provide a foundation and framework for future studies using the hundreds of thousands of annually- to sub-annually-resolved tree-ring records of fire spanning centuries, which will further advance our understanding of the interactions among fire, climate, topography, vegetation, and humans across North America

Conception participative et évaluation d'un serious game pour les enfants asthmatiques

International audienceThe study described in this paper highlighted the participatory design process (PD) in the context of asthma e-learning. First, we described global process to design this tool named KidBreath. Second, we evaluated in two Year 4 classes its efficacy in a motivation way, usability, disease knowledge and interests of children by their system. Results showed, in acceptance with behaviors, high level of intrinsic motivation when using KidBreath, usability and enjoyment of edutainment activities. This pilot study tends to confirm to continue with this approach with asthma kids at home.L'étude décrite dans cet article met en exergue l'intérêt d'une approche de conception participative (CP) dans le cadre d'un apprentissage en ligne sur l'asthme pour les enfants. Après avoir décrit l'ensemble de la démarche pour la conception de cet e-learning nommé KidBreath, nous évaluons dans 2 classes de CE2 son efficacité au niveau motivationnel, utilisabilité, connaissance sur la maladie et émergence de l'intérêt que les enfants y portent à travers la curiosité qui en émerge. Les résultats, probants aux comportements observés, montrent un haut niveau de motivation intrinsèque pour utiliser l'outil, un fort taux d'utilisabilité et une grande satisfaction des activités ludo-éducatives. Cette étude pilote nous confirme de continuer dans cette approche en testant le système notamment auprès des enfants asthmatiques sur du moyen terme

Fire Regimes of the Southern Appalachian Mountains: Temporal and Spatial Variability over Multiple Scales and Implications for Ecosystem Management

Information about historic fire regimes and the departure of current fire regimes from historic conditions is essential for guiding and justifying management actions, such as prescribed burning programs for ecosystem process restoration and fuel reduction. Such information is noticeably lacking for the southern Appalachian Mountains, where human populations are encroaching onto wildland areas, and where decades of fire exclusion have contributed to the decline of fire-associated communities and also to altered fuel loads. We address this knowledge gap via a multi-scale investigation of the variability in fire regimes over time and space using tree-ring reconstructions of fire history and stand dynamics in pine and mixed hardwood-pine forests. The tree-ring analyses are augmented by soil charcoal analyses and by statistical and GIS analyses of fire records from federal agencies. We used a multi-spatial scale approach to determine locations for tree-ring reconstructions of fire history. First, we established a network of four sites across the lowelevation pine-hardwood ecosystems in the western Great Smoky Mountains National Park (GSMNP), where we also set up plots for examining vegetation dynamics via age structure and species composition. We established a second network for reconstructing fire history and vegetation dynamics in middle-elevation forests of GSMNP spanning xeric to mesic sites. Together these low- and middle-elevation reconstructions portray patterns of fire and vegetation response across a broad landscape. Finally, we established two additional fire history sites, one in the Ridge and Valley terrain west of the GSMNP, and the other along the eastern escarpment of the Blue Ridge Mountains to the northeast of GSMNP. These sites combine with the GSMNP sites to characterize region-scale patterns and variations in fire history. Analyses of the tree-ring data reveal that fires burned frequently (at about 2–14 year intervals) in the southern Appalachian Mountains from the late 1700s/early 1800s until the early to middle 1900s, when burning declined coincident with fire protection. The density of trees, especially fire-intolerant species, increased in the 1900s as fire frequency declined. The soil charcoal study was conducted within the low-elevation tree-ring study sites in GSMNP. Charcoal fragments range in age from modern to about 3000 years old. About 75% of the hundreds of charcoal fragments identified in the cores are of pine. These results suggest that fire was a component of the forests long before the beginning of the tree-ring fire chronologies. They also emphasize the association of pine with fire in these humid environments where vegetation succession tends toward the replacement of pines by hardwoods. The GIS and statistical analyses of recent burning patterns clarify relationships among fire, climate, and terrain. Fire occurs most commonly in drier climates within the region, and during dry years. At the scale of local terrain, dry sites (e.g., ridgetops) burn more commonly than moist sites (e.g., valleys). Such topographic patterns are influenced by broader climatic conditions, however. Topographic patterning is more pronounced under wet climatic conditions than under dry conditions, which permit fires to spread into mesic topographic positions