Fire Edge Research Articles

Hannah Mary's Corn Pone

Hannah Mary's Corn Pone Bernard L. Herman (bio) Click for larger view View full resolution My friend Bill McIntire, a Lewes native, wrote me, "We just always have it as a side at Christmas morning breakfast with bacon, eggs, scrapple, etc., there's always some left over for subsequent breakfasts, but we never had it any other time. The pone is large, like I said, so often one pone will get split up so that several households can have some for their Christmas." All illustrations by Nate Beaty. Sweet potatoes flourish in sandy soil. Strawberries announce the advent of spring. Figs sweeten the landscape in August. Canada geese flock to harvest cornfields in winter. Oysters, drum fish, mullet, clams, and spot add a signature dimension to coastal tables, but so, too, do local preparations for stewed pork and pumpkin, black duck and dumplings, peas and doughboys, and sweetened cornbread. The foodways of the coastal South offer a lot more than seafood. Corn pone, as regional fare and culinary concept, covers a good deal of territory, but Hannah Mary's pone offers a glimpse into a dish well seasoned with Eastern Shore associations that embrace relations between the well-to-do and the poor, black and white, and memory and practice. Hannah Mary's pone is not to [End Page 151] be confused with cornbread or its corn pone variations. Hers bore only the most distant relation to the familiar miniature cornbread loaves baked in cast iron pans, each pone embossed with the impression of a shucked ear of corn. These corn pones, typically chokingly bone dry beyond the redemption of all liquid, offer something of a dim caricature of their origins as ashcakes baked in hot coals at fire's edge. Happily, these baked asphyxiations are not the only pones in the world, nor are those other pones without their own extraordinary histories. "Pone" (from the Algonquin apan), as encountered and adapted by Africans and Europeans in the early 1600s in the Chesapeake Bay country, designated bread baked by American Indians. Over time and habit, it acquired more specific reference to cornbread of the American South. Recollecting her childhood in the town of Lewes at the mouth of the Delaware Bay, Sarah Jastak (born Sarah Ellen Rickards) recounted the weekly appearance in the 1930s of an African American huckster, Hannah Mary Burton. Hannah Mary's route carried her from her modest clapboard home in the black community located across the railroad tracks, past the high school, and onto McFee Street, where she sold pone, pies, and a bit of garden produce to a white clientele. "She had a wagon pulled by one horse, and you could hear that horse clip clopping down the street," Sarah begins. "It was just an open old wooden wagon. It just looked creaky and very, very rustic, and I don't even remember how she had her baked goods stored. Maybe boxes or something, but nothing fancy." Wistfulness inflects Sarah's words, spoken with a smile: She was a lovely lady . . . And once or twice I tasted her pies, but we really couldn't afford them because we always made those at home. But Hannah Mary made what she called a "corn pone," and it was huge. [I]t was certainly more than a foot round and about six, seven inches deep. I don't know exactly how she made it, but I know it took cornmeal and molasses and water. I don't know what else she put in it, but I know she baked it. She had an old cookstove range that was wood burning or coal burning, but she would bake it probably for about six hours. And she used to make just one and she would sell it in chunks . . . We didn't get it every week, but when we bought it, we would always get a quarter of it, and, boy, was it good! You cut it in slices and then either steamed it with lots of butter or you cut it in slices and kind of sautéed it on each side and had it with eggs and bacon. That was good!1 [End Page 152] Click for...

Presence and dynamics of ambrosia beetles and other xylophagous insects in a Mediterranean cork oak forest following fire

Abstract Cork oak ecosystems, which are biodiversity hotspots and have great socio-economic importance in the western Mediterranean Basin, have been experiencing serious decline in the last decades attributed to different causes, including wildfires. Besides direct mortality, the surviving burned trees become more vulnerable following fire and may be attacked by wood boring insects (Coleoptera), which may further affect tree vigor and give rise to massive dispersing offspring affecting surrounding areas. In the first spring after a wildfire that occurred in July 2013 in a cork oak stand in central Portugal, we set up different types of insect traps (interception, emergence and aggregation pheromone traps), and monitored them for up to 16 months. Fire occurrence had a great impact on cork oak trees attractiveness to xylophagous insects, which increased significantly with increasing fire severity. Living unburned trees located close to the fire edge were clearly avoided, while burned trees with no regeneration were the most attractive. Four species of ambrosia beetles, represented nearly 90% of all xylophagous insects captured in interception and emergence traps, namely Platypus cylindrus (Platypodinae), Xyleborus monographus, Xyleborinus saxeseni and Xyleborus dryographus (Scolytinae). Therefore, the presence of ambrosia beetles in recently burned forests should be carefully assessed, and their control should focus on preventing colonization and the spread of infestation. Forest management should primarily focus on increasing tree vigor, and on reducing the factors that may increase burn severity if a fire occurs. In the first years after a wildfire, it is advisable to avoid any activities that are likely to increase stress of burned and neighbouring unburned trees, such as cork extraction, branch pruning and soil ploughing. Additionally, post-fire logging and removal of dead trees before the next spring (when first emergences start to occur), and the use of pheromone traps, are other possible measures to reduce the number of beetles in these situations.

Post‐fire recovery of litter detritivores is limited by distance from burn edge

AbstractClimate change is likely to result in an increased frequency of extreme fire events, including more large‐extent wildfires. The effects of fire extent on post‐fire faunal recovery are poorly understood. Effects on invertebrate detritivores are of particular interest due to their functional importance in litter breakdown. We asked if distance from fire edge affected the composition and morphological traits of a key group of large invertebrate detritivores: cockroaches (Blattodea) 6 years after fire. We used six replicate transects in herb‐rich foothill habitat in areas that were severely burnt during the 2009 Black Saturday fires, north‐east of Melbourne, Australia. Transects extended from unburnt controls up to 5 km into large extent burns. Habitat variables were measured and cockroach abundances were recorded using artificial habitats comprised of stacked egg trays. Cockroach morphological traits were recorded in the laboratory. Multivariate generalized linear models revealed that habitats varied with transect, but not distance into the burn, suggesting recovery of habitat features relevant to cockroaches. Distance from burn did not affect the species richness or abundance of cockroaches, but both richness and abundance increased with bark and litter cover and decreased at lower temperatures. Cockroach assemblage composition responded significantly to distance into burn, transect and habitat variables, although only Platyzosteria similis was negatively associated with distance into the burn. Fourth corner models including traits did not provide greater predictive power than models including only species abundances and environmental variables. Wing presence, which was associated with smaller body size, did not affect site occupancy. Although species traits did not predict cockroach responses, our work shows that distance into a fire, a surrogate for fire extent, continued to be an important determinant of post‐fire assemblages 6 years after fire. An increase in large‐extent fires may reduce the recolonization potential of some cockroach species, potentially limiting their functional importance in litter breakdown.

Connectivity of litter islands remaining after a fire and unburnt forest determines the recovery of soil fauna

Forest wildfires can dramatically affect soil communities and reduce abundance and diversity of soil fauna. The recovery of soil animals after a fire depends both on immigration from the unburnt forest and on local survival in less-burnt spots, but the relative importance of these mechanisms is poorly known. Therefore, these factors were studied with regard to soil macrofauna and soil mites seven years after a wildfire occurring in a pine forest area with shallow soil in 2001 in central Sweden. Three replicate transects, each consisting of four plots were studied. The plots were located in (i) the unburnt forest close to the fire edge; (ii) slightly burnt patches directly attached to the unburnt forest; (iii) slightly burnt patches surrounded by bare rock but connected to the unburnt forest edge by a corridor with mostly unburnt litter and vegetation; and (iv) island patches not connected with a corridor to the unburnt forest edge. The hypothesis was that that soil animals would particularly disperse from the unburnt forest to moderately burnt plots inside a burnt area via the network of less-burnt corridors. Poor dispersers would be especially few in the island patches lacking connection to the “mainland”, whereas good dispersers would be independent of gaps in connectivity. As expected, the highest abundance of both macrofauna and oribatid mites was found in the unburnt forest. Resident soil macro- and mesofauna representatives had half the abundance in the edge and corridor plots as compared to the control, but their abundance was not lower in the island plots than in the corridor plots indicating on-site survival and recovery. Mobile mesostigmatid mites did not show any significant reduction of abundance in any of the plots. The abundance of soil-dwelling oribatid mites did not differ between islands and unburnt forest, but mobile aboveground oribatids had significantly lower abundance on the islands than in the unburnt forest. The opposite was observed for aboveground and belowground oribatid mite species richness. In conclusion, belowground animals showed mainly local survival and seemed to be independent of corridors presence, whereas most aboveground and mobile macro- and mesofauna seemed to be more responsive to isolation induced by forest fires. Soil and litter corridors connecting unburnt patches inside the burnt forests with the unburnt edges were important mainly for less mobile groups of soil macrofauna. This supports the idea that there is a relatively slow process of soil ecosystem recovery and that external colonization of the burnt areas dominates over the local survival and recovery from refuges.

An Autoadaptive Edge-Detection Algorithm for Flame and Fire Image Processing

The determination of flame or fire edges is the process of identifying a boundary between the area where there is thermochemical reaction and those without. It is a precursor to image-based flame monitoring, early fire detection, fire evaluation, and the determination of flame and fire parameters. Several traditional edge-detection methods have been tested to identify flame edges, but the results achieved have been disappointing. Some research works related to flame and fire edge detection were reported for different applications; however, the methods do not emphasize the continuity and clarity of the flame and fire edges. A computing algorithm is thus proposed to define flame and fire edges clearly and continuously. The algorithm detects the coarse and superfluous edges in a flame/fire image first and then identifies the edges of the flame/fire and removes the irrelevant artifacts. The autoadaptive feature of the algorithm ensures that the primary symbolic flame/fire edges are identified for different scenarios. Experimental results for different flame images and video frames proved the effectiveness and robustness of the algorithm.

Influencing factors on early vegetation restoration in burned area of Pinus pumila – Larch forest

Pinus pumila (Dall.) Regel, a rare conifer and key species in high latitude and high altitude mountains, has an important role in soil and water conservation. This evergreen shrub grows 3–6m high in P. pumila – larch (Larix gmelini) open forest at altitudes of 800–1200m in the Greater Kingan Mountain Range (Daxing’an Mountain). Forest fires are major natural hazards to P. pumila – larch forest. The unique ecological role of this community gives important theoretical and practical significance to research on P. pumila – larch forest restoration after fires. Literature concerning factors influencing early vegetation restoration in burned areas in this habitat is sparse. We studied these factors, especially those related to P. pumila seedling establishment. The results showed fires in P. pumila – larch forest usually resulted in severe burns. Typically almost no P. pumila survived after fires. Nearly all ground fuels were consumed. Second growth after fires exhibited low species richness. The dominant tree/shrub seedlings found after fires were birch (Betula platyphylla) and larch, with small number of P. pumila. Other shrub seedlings found were Ledum palustre, Vaccinium vitis-idaea, Betula fruticosa, and Rubus arcticus. The main herb species found were Deyeuxia langsdorffii, and Chamaenerion angustifolium. Important factors influencing early vegetation restoration after fires included seed dispersal, fire size, and site condition. Seed dispersal in birch and larch is higher than in P. pumila; more seedlings of birch and larch were found in burned areas than seedlings of P. pumila. Most seeds germinated in the first year following a fire. The extent of the burned area influences seedling distribution patterns, especially in species with limited seed dispersal ability. Birch and larch seedlings were evenly distributed in the entire burned area, while seedlings of P. pumila were found only at the fire edge. No P. pumila seedlings were found more than 50m away from seed source trees. Site condition significantly influenced seed germination and growth in birch and larch; these seedlings only grew well in burned areas with good site conditions (shallow slopes, thick soils, etc.). They did not grow well in burned areas with poor site conditions (steep slopes, thin soils, etc.). However, P. pumila seedlings could grow well in burned areas with either good or poor site conditions. The strong vitality of P. pumila seedlings gives this species an enormous ecological advantage in soil conservation and environmental restoration and conservation. We conclude that the main factor influencing seedling establishment in P. pumila is its weak seed dispersal ability. Although the P. pumila seeds can germinate in all burned areas, natural regeneration rarely restores burned areas to the original P. pumila – larch forest. Planting seeds and/or seedlings may facilitate burned area restoration to P. pumila – larch forest. Because P. pumila seedlings grow very slowly, the restoration process may take decades.

Relevance of soil seed bank and seed rain to immediate seed supply after a large wildfire

We examined the density and composition of the immediate seed supply (i.e. instant potential post-fire germination from soil seed bank and off-site seed rain) after a large wildfire in a sub-Mediterranean pine forest. We also tested the effects of fire severity and distance from unburned edges on the density and composition of the seed bank and the immediate off-site seed rain. Our results showed that although seed density did not differ between them, their composition was markedly different. The soil seed bank was dominated by species from the Fabaceae family with limited dispersal mechanisms such as autochory and barochory, whereas the seed rain was mainly composed of species from the Asteraceae family with wind-dispersed seeds. These patterns were not affected either by fire severity or distance from the fire edge. The main conclusion of the study is that both the soil seed bank and the seed rain play an important role in providing seeds for immediate regeneration after a large wildfire throughout the burned area. We suggest that the role of seed rain on immediate post-fire recovery of Mediterranean plant communities might be more important than has previously been thought. However, the effective role of this group of species on the longer term should be evaluated.

Edge effects of wildfire and riparian buffers along boreal forest streams

Summary1. Clearcutting and wildfire are the two major edge‐creating disturbances in boreal forests. While clearcutting retains at least a 30 m buffer, wildfires burn close to streams killing most of the trees and potentially creating a different edge structure. Different edge structures are likely to support different plant assemblages. The riparian buffer and fire edge structures and their effects on plant assemblages are unknown, but they have implications for forest management that aims to harvest trees and conserve biodiversity by emulating natural disturbance.2. We hypothesized that environmental filters created by post‐fire residual structures at the fire edge will support a different plant assemblage than the buffer edge. We further hypothesized that the fire edge with a weaker environmental filter because of post‐fire residual structures and proximity to streams will result in lower depth of edge effects (DEEs) and magnitude of edge effects (MEEs) than buffer edges.3. We determined the structure of canopy trees, understorey cover and the near‐ground microclimate by sampling 576 (5 × 10 m) and 1820 (1 × 1 m) quadrats along 96 transects beside 24 streams near Thunder Bay, Canada. We determined DEEs and MEEs by comparing edge variables with reference forests. We used repeated measures/factorialanovas with Tukey’spost hoctests to determine DEEs andmanovafor MEEs.4. The average microclimatic DEEs extended 8 m into the buffer but only 2·5 m from the fire edge. Similarly, the DEEs for plant life‐forms extended 20 m from the buffer edge and 5 m from the fire edge. At the fire edge, the structural MEEs were significantly higher, but the microclimatic MEEs were lower than the buffer edge. We found no significant difference in the overall life‐form MEEs, but shrubs, shade‐tolerant herbs and grasses were increased at the buffer edge and decreased at the fire edge.5. Synthesis and applications. We discovered that the ecological structure at buffer and fire edges in boreal forests creates different environmental filters supporting different plant assemblages. Lower structural and microclimatic DEEs and MEEs at the fire edge result from (i) edge location, (ii) intact shrub layer and (iii) disturbance‐resilient riparian vegetation. We suggest that replacing the conventional sharp edges of the riparian clear‐cut buffer with ‘feathered’ edges by selective harvesting of trees will create wider edges mimicking wildfire legacy and will help to emulate natural disturbance for conserving biodiversity.

Application of the AMBUR R package for spatio-temporal analysis of shoreline change: Jekyll Island, Georgia, USA

The AMBUR (Analyzing Moving Boundaries Using R) package for the R software environment provides a collection of functions for assisting with analyzing and visualizing historical shoreline change. The package allows import and export of geospatial data in ESRI shapefile format, which is compatible with most commercial and open-source GIS software. The “baseline and transect” method is the primary technique used to quantify distances and rates of shoreline movement, and to detect classification changes across time. Along with the traditional “perpendicular” transect method, two new transect methods, “near” and “filtered,” assist with quantifying changes along curved shorelines that are problematic for perpendicular transect methods. Output from the analyses includes data tables, graphics, and geospatial data, which are useful in rapidly assessing trends and potential errors in the dataset. A forecasting function also allows the user to estimate the future location of the shoreline and store the results in a shapefile. Other utilities and tools provided in the package assist with preparing and manipulating geospatial data, error checking, and generating supporting graphics and shapefiles. The package can be customized to perform additional statistical, graphical, and geospatial functions, and, it is capable of analyzing the movement of any boundary (e.g., shorelines, glacier terminus, fire edge, and marine and terrestrial ecozones).

Effects of fire disturbance on the soil physical and chemical properties and vegetation of Pinus massoniana forest in south subtropical area

A variety of studies on the impact of fire disturbance on ecosystems has shown that the physical and chemical properties of soil after fire disturbance change notably. Meanwhile, little is known about the effects of different fire intensities on the soil properties and vegetation after fire disturbance, especially in the south subtropical area. In this paper, we analyzed the soil physical and chemical properties, vegetation species and species diversity of fire center, fire edge (which was burned a year ago) and non-burned Pinus massoniana plantation in Gaoyao, Guangdong province, China. The results showed that the soil conductivity, water content, total nitrogen, total potassium, and available potassium content of fire center were significantly higher than those of the non-burned land, and pH was higher than that of fire edge, whereas the available nitrogen, total phosphorus and organic matter content were much lower, which were generally existed in 0–10 cm soil layer and 10–30 cm soil layer. Changes of the soil properties of fire edge were similar with those of fire center, but less significant, and seemed to be more complex. Effects of burning on the vegetation of fire disturbance plots were found to be notable, species number and average height of plants of fire disturbance plots were lower than those of the non-burned plots, a difference of species diversity and uniformity were also shown, and finally, the composition of plant community also changed, e.g., pioneer species such as D. dichotoma, etc., dominated, and drought-resistant plants, heat-resistant plants and positive plants increased after burning.

Can soil phytolith analysis and charcoal be used as indicators of historic fire in the pinyon-juniper and sagebrush steppe ecosystem types of the Great Basin Desert, USA?

Wildland fire intensity and area are increasing across the Intermountain West, USA, in a variety of ecosystem types including the pinyon-juniper woodlands and sagebrush steppe of the Great Basin Desert. Unfortunately, we do not know if there were historic analogues for these high-intensity stand-replacing fires because of the lack of fire scars that record evidence of them. Soil-charcoal and phytolith analyses have been successfully employed in other regions to garner information about fire regimes through the Holocene. We studied the utility of these methodologies and related taphonomic issues in soils in the Great Basin Desert. Our results showed that both microscopic charcoal and burned phytoliths can be found in soils with radiocarbon ages from modern to late Holocene. Microscopic charcoal abundance was more useful than size class as an indicator of recent local fire. Its abundance declined rapidly and remained low at 2.8 to 4.8 km from the edge of the fire. A Burned Phytolith Index shared a similar pattern starting at 0.4 km from the fire edge. Both proxies declined in abundance with depth in the soil at recent burn sites while remaining constant in unburned sites. We were unable to detect a signal for a known historic fire, however, this may have been a result of sample depth. Our results indicate that soil-charcoal and phytolith analysis can be used to examine questions about historical fires in these two ecosystems of the Great Basin Desert.

Spatial variability of stand-scale residuals in Ontario’s boreal forest fires

Knowledge of postfire residuals in boreal forest landscapes is increasingly important for ecological applications and forest management. While many studies provide useful insight, knowledge of stand-scale postfire residual occurrence and variability remains fragmented and untested as formal hypotheses. We examined the spatial variability of stand-scale postfire residuals in boreal forests and tested hypotheses of their spatial associations. Based on the literature, we hypothesized that preburn forest cover characteristics, site conditions, proximity to water and fire edge, and local fire intensity influence the spatial variability of postfire residuals. To test these hypotheses, we studied live-tree and snag residuals in 11 boreal Ontario forest fires, using 660 sample points based on high resolution photography (1:408) captured immediately after the fires. The abundance of residuals varied considerably within and among these fires, precluding attempts to generalize estimates. Based on a linear mixed-effects model, our data did not support the hypotheses that preburn forest cover characteristics, site conditions, and proximity to water significantly affect the spatial variability of stand-scale residuals. The results do indicate, however, that stand-scale residual variability is associated with local fire intensity (strongly) and distance to fire edge (weakly).

Recolonization of a burned Mediterranean area by terrestrial gastropods

Wildfires are common natural perturbations in Mediterranean ecosystems. Their frequency and extent have changed in recent decades to become one of the main ecological problems for wildlife. The response of fauna to wildfires depends greatly on the life histories and biological traits of each species. Terrestrial gastropods have limited mobility, and their presence is restricted by the vegetal and abiotic characteristics of habitats. For this reason, they are expected to have a low ability to recolonize burned areas. We have explored their survivorship and recolonization patterns according to the cryptic-refuge and fire-edge models in a Mediterranean protected area affected by a large fire in August 2003. The low number of species recorded at burned sites demonstrates the negative effects of a wildfire on the richness of gastropod assemblages 4 years after the perturbation. However, the total number of living individuals did not vary between burned and unburned areas, suggesting an after-fire shift in dominant species from woodland to open-space species. Forest species with wide European distributions dominated in unburned sites, whereas open-space species and xerophytic Mediterranean species were present at burned sites. These differences were evident even at the burned sites closest to the unburned forest, suggesting low recolonization rates from the fire edge. By contrast, the abundance of xerophilous species as well as isolated records of mesophilous species in the burned areas suggests the survival of small populations and further recuperation after fire following the cryptic-refuge model.

Landscape structural features control fire size in a Mediterranean forested area of central Spain

Landscape structure may affect fire propagation and fire size. Propagation may be favoured in landscapes that are homogeneous and hindered at places of greater heterogeneity, and where discontinuities occur. We tested whether there is continuity in landscape structure across the edges of 110 fires in the Sierra de Gredos (central Spain). We used Landsat Multispectral Scanner images to map and assess the land-cover composition and other features of fires. Landscape diversity along the pixel row of the fire edge and of the two adjacent ones (burned and unburned) was compared for all fires. Additionally, changes in landscape properties and fuel hazard perpendicular to the fire edge evaluated the degree of discontinuity from inside the burn towards the outside across the edge. Fire size was related to landscape properties and weather conditions using generalized linear regression models. Diversity increased from inside the burn towards the edge and outside the burn. Discontinuity in land-cover types and fuel hazard increased from the inside towards the outside. Modelling confirmed that fire size was in part related to landscape characteristics of the burned area and of the edges of the fire perimeter. We conclude that landscape structure was important in determining fire size in this area.

Long-distance transport of macroscopic charcoal by an intensive crown fire in the Swiss Alps - implications for fire history reconstruction

The correct interpretation of charcoal records in a palaeoecological context requires the understanding of the sources and transport of charcoal particles. Conventionally, it is assumed that macroscopic charcoal particles are not transported far from fires ( c. 200m). Therefore macroscopic charcoal records are used to reconstruct local fire frequencies. However, the general scarcity of empirical and experimental evidence impedes a thorough check of this assumption. In this study we present the first unambiguous evidence of kilometre-scaled macroscopic charcoal transport in Europe. During the hot summer of 2003 an intensive crown fire occurred in Leuk, central Swiss Alps. It affected 300 ha of forest as well as 10 ha of pasture and fallow land. Litter traps and nets had been located approximately 5 km west and east of the burned area. The downwind site in the east (Jeizinen) recorded a strong charcoal fallout at 5.3 km from the fire edge. The observed charcoal influx of fragments with a size up to 1.3 cm reached average values of 0.144 and 0.098 mm2/Cm2 per fire (or yr) in five traps and two nets, respectively. These values are comparable with charcoal accumulations measured at only c. 50 m from large fires, suggesting that macroscopic charcoal transport does not decay rapidly to zero with increasing distance from the fire. We suggest a long-distance dispersal model for transport of macroscopic charcoal during large fire events. Reconstructions of local fire regimes may be affected by long-distance transport of macroscopic charcoal, although this problem is mitigated by the tendency of most macroscopic charcoal particles to be deposited within very short distances (< 50 m) from the fire edge.

Tree recruitment from burn edges

We developed and tested a wind-dispersal model of tree recruitment into burns from living sources at the fire edge or from small unburned residual stands. The model was also tested on recruitment of serotinous Pinus banksiana Lamb. within a burn. The model assumed that source strength is proportional to basal area density and that an individual (point source) recruitment curve can be expressed as a lognormal distribution. The model made significant predictions of the recruitment curves of Engelmann spruce (Picea engelmannii Parry ex Engelm.), white spruce (Picea glauca (Moench) Voss), and balsam fir (Abies balsamea (L.) Mill.) to distances as great as 2.0 km, although it tended to underpredict Abies and overpredict Picea. The model gave significant prediction of recruitment for jack pine (Pinus banksiana) within burns with seeds derived from aerial seed banks, and of white spruce and tamarck (Larix laricina (Du Roi) K. Koch) up to 100 m from residual stands. By forestry standards, burns are poorly stocked by those species that must obligately recruit from edges. In large fires, adequate stocking by a species such as white spruce that had 5 m2/ha of basal area would be limited to about 70 m from the edge. Small residual stands are expected to supply about half of all the recruits of white spruce or fir at distances exceeding about 800 m from a nominal burn edge.

Interpretation of the charcoal record in forest soils: forest fires and their production and deposition of macroscopic charcoal

Traps were used to quantify charcoal production and transport during three experimental forest fires in Boreal Scandinavia. The traps were spatially arranged to collect charcoal particles inside burn areas, and outside burn areas at different distances (0.1–100 m) from the fire edge. The number of inside and outside traps was 280 and 424, respectively. Trap area was 48 cm2. After the burn, trap content was sorted and sieved in two size-classes of charcoal particles, namely small (0.5–2.0 mm) and large (. 2.0 mm), and number and mass of particles were determined. The production and distribution of charcoal were highly variable at fine spatial scales inside burn areas. On average, inside traps contained 12.1 small and 10.1 large particles, and the average charcoal mass was 0.112 g per trap (corresponding to 235 kg ha-1). The largest size-class made up 94% of the mass. Outside traps contained 0.3 small and 0.1 large particles per trap, and 45% of the outside particles were distributed, 1 m from the fire edge. It is concluded that the occurrence of macroscopic charcoal ($ 0.5 mm) in forest soils provides a solid evidence for local fire influence, and that the presence of large charcoal particles can be used to distinguish between fire-prone and fire-free areas with high spatial precision. Absence of large particles must, however, be more carefully interpreted as 14% of the inside traps lacked macroscopic charcoal. We argue that the charcoal in Boreal forest soils should be less persistent than previously suggested because documented fire-return intervals result in an unrealistic charcoal accumulation presupposing high persistence.

Experimental and Numerical Studies of a Laminated Composite Single-Lap Adhesive Joint

The problem of a single-lap bonded joint with laminated polymeric composite adherents and with a spew fillet, subjected to tensile loading, is investigated. Experimental and numerical analyses of this problem are presented to address the mechanics and deformation of such material and bonding configuration. Strain gages are employed to record the geometrically nonlinear deformation of the specimen. Full-field moiré interferometr is used to measure the surface deformation of the adherends and adhesive (including a spew fillet). A geometrically nonlinear, two-dimensional finite element analysis is performed to check the mechanics assumptions by comparing with the experimental measurement. A good correlation between experimental and numerical solutions is obtained. It is observed that the composite single-lap joint deforms nonlinearly when subjected to tensile loading. The resulting displacement and strain fields for the adherend and adhesive layer are also presented. The moire results show that the transverse normal and shear strains, but not the longitudinal stain, for composite adherents on the free surface suffer from the fire edge effect, anticlastic as well as bending-twisting coupling effects. For the adhesive strains, the transverse normal (peel) component on the free surface is compressive throughout all the bond line except for a small region near the tip of the spew fillet, wile this component in the interior becomes tensile near the end of the overlap. The adhesive longitudinal strain in the spew fillet is insensitive to the three-dimensional defamation effect, but not the adhesive shear strain in the spew fillet. The adhesive longitudinal strain is not small enough to be neglected in the stress analysis.

The Cell

Ad Libitum15 September 1993The CellAlice Jones, MDAlice Jones, MDSearch for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/0003-4819-119-6-199309150-00018 SectionsAboutFull TextPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail Like every reception, there's foodand dancing and bumpinginto all those quirkyrelatives: blood, Great-aunt Henriettedeclares, is thicker thananything. Familyis in the genes, she says, as if shejust discovered the cell,the body's time capsule,recording history for the clumsy, nakedbipeds who hover atthe edge of fire,evolving into creatures who learnthe cell's workings:how it sucks upwater from the surrounding matrixthrough sticky-lippedpores; how each tinyapparatus for food or sex floatsin this one drop of opaquesalinethe primal jelly;how it composes proteins frominborn templates forgenerations of identical daughters;pull ... Author, Article, and Disclosure InformationAffiliations: PreviousarticleNextarticle Advertisement FiguresReferencesRelatedDetails Metrics 15 September 1993Volume 119, Issue 6Page: 533KeywordsBirthBlood cellsChromosomesFoodProteins ePublished: 15 August 2000 Issue Published: 15 September 1993 Copyright & PermissionsCopyright © 1993 by American College of Physicians. All Rights Reserved.PDF downloadLoading ...

The Edge of Fire: Volcano and Earthquake Country in Western North America and Hawaii

The Edge of Fire: Volcano and Earthquake Country in Western North America and Hawaii