Catastrophic Storm Research Articles

Habitat disturbances differentially affect individual growth rates in a long‐lived turtle

AbstractDisturbances often help structure ecological communities, and their impacts may have consequences on population dynamics and long‐term species persistence. Should disturbances affect resources, a trade‐off may result between reproduction and individual growth, which in turn could affect the timing of sexual maturity in animals dependent on reaching a requisite size for the onset of maturation. We used a 14‐year mark–recapture dataset to determine the effects of catastrophic storms and the removal of nonindigenous vegetation on individual growth rates of a long‐lived turtle Terrapene carolina bauri. Adult male growth rates increased 19% after the disturbances, whereas female growth rates decreased by a similar percentage. Juvenile growth rates briefly increased, but as these animals became subadults, their growth rates slowed after disturbance, a change more pronounced in females than males. After the disturbances, the onset of male sexual maturity decreased by c. 1 years (from 10.8 to 9.5 years), female maturity was delayed by 2.5 years (from 8.5 to 11.0 years), and the subadult life stage was extended from 2 to 3.5 years. With resources and habitats similarly available to adults, we hypothesize that adult females diverted resources from growth to reproduction, whereas males allocated available resources to growth. Subadult growth rates decreased regardless of sex, implying that fewer or lower quality prey were available to smaller sized turtles in the years following disturbance. The results of this study suggest that habitat disturbances affected individual growth rates differently according to sex and life stage, which in turn affected the timing of maturation. In long‐lived vertebrates, such perturbations on life‐history traits such as growth rates likely affect population recovery, and may help to explain why turtle populations recover slowly following catastrophic disturbance, even when adult survivability is high.

Tree failure following a windstorm in Brewster, Massachusetts, USA

While there are many ex post facto studies of tree failures due to catastrophic storms, relatively few have considered the effect of defects, and even fewer have explored the effect of tree maintenance, on the likelihood of failure. In light of the heightened climate of litigation in the United States, and the complexity of reliably predicting tree failure, additional studies are justified. A catastrophic windstorm in December 2005 on Cape Cod in Massachusetts, USA, provided an opportunity to study how structural defects and maintenance history affect the likelihood of tree failure. Species, height, diameter at breast height (DBH), the presence of defects, and whether trees had been pruned or nearby trees removed were recorded on trees at campsites in a park affected by the storm. The percentage of trees that failed varied among species, and evergreens failed more frequently than deciduous trees, which were leafless at the time of the storm. Large trees were more likely to fail than smaller trees, although this was not true of all species. The defects were more common on standing trees and trunk failures than root failures. Pruning trees had little effect on the failure, but removing trees increased the likelihood of root failure. The results are discussed in the context of managing tree risk.

After the Storms: Tradition and Change in Bayou La Batre

About once a century in Bayou La Batre, Alabama, a catastrophic storm comes roaring from the Gulf of Mexico. Ninety-nine years before Hurricane Katrina there was the hur ricane of 1906, a mighty wind that lasted for more than twenty-four hours, long before these events had names. The memories of it are present even now in the oral history of the Bayou?in the family stories handed down for generations in this coastal fishing village. Alma Bryant, a girl of thirteen in 1906, and later her community's leading educator, re membered being separated from her family in the storm, as the tidal surge tore her house from its moorings. Rain, the coldest and heaviest I have ever felt, pounded me relent lessly, she said. Then the vicious wind picked me up and immersed me in one of those craters made by an uprooted tree. I clutched the limb . . . and held on for dear life, barely conscious of the weird noises all around me?the shrieks of frightened birds, the woeful cry of a drowning calf, the dying moans of Mr. Deakle's old white mare pinned beneath the demolished barn.1 Bryant, in the end, was one of the lucky ones. She managed to swim and clamor through the floating debris?the limp, dead chickens, bloated hogs, writhing snakes? toward the flickering light of a house in the distance. At least 135 others did not make it, and the Mobile Register, the morning newspaper in the nearest city, carefully recorded the details. Two Bayou women lining up the bodies, covering them with shrouds; a fright ened family emerging from the woods, where they had drifted all night in an open skiff; a writer's description of those who survived: Most . . . resembled great chunks of liver colored beef, so badly were they battered and bruised.2 This now is a part of the lore of Bayou La Batre, a place where residents freely acknowl edge that life on the edge of the continent is hard. The hurricanes come and the hurri canes go, requiring resilience of those who survive. So it was in 1906, and so it is after Hurricane Katrina. But there is another understanding more subtle and elusive, more difficult for many people to explain. When the truly massive storms hit the Bayou, those once-a-century calamities, they have often changed the course of local history, much as they might alter the course of a river.

Declining Diversity in Natural and Restored Salt Marshes: A 30‐Year Study of Tijuana Estuary

Abstract Between 1974 and 2004, Tijuana Estuary’s natural salt marsh underwent pulse disturbance (an 8‐month nontidal period in 1984), which caused the sudden loss of two short‐lived halophytes (Salicornia bigelovii [Sb] and Suaeda esteroa [Se]) and rapid dominance of a productive native succulent (Sa. virginica [Sv]), plus ramp disturbance that led to gradual codominance by Jaumea carnosa (Jc) (another productive succulent) by 1994. Species richness was high in 1974 (4.2 species/0.25‐m2 plot), low in 1984 (1.4 species), and not fully recovered by 1994 (3.7 species) or 2004 (3.9 species). Restoration efforts (reseeding former habitat and excavating and planting new sites) did not recover the populations of Sb or Se. In a 1997 project, plantings of these and six other native halophytes survived initially, but by 2005, short‐lived species were lost and Sv and Jc dominated, as in the natural marsh. In a 2000 restoration site, planting mortality was high for five species, but Sv recruited voluntarily and dominated by 2005. We attribute recent vegetation changes to frequent catastrophic storms, flooding, and sedimentation, which contrasted strongly with the benign conditions of decades prior to 1974. Sediment blocked tidal channels in 1984 and gradually elevated the marsh plain, degrading the diverse salt marsh and hindering efforts to restore it. Future restoration efforts will require even greater control over sediment inflows plus contouring sites to include natural topographic features that appear critical to sustaining high species richness and evenness.

RETRACTED ARTICLE: Space and time distributions of major winter storms in the United States

Winter storms are a major weather problem in the United States and their losses have been rapidly increasing. A total of 202 catastrophic winter storms involving ice storms, blizzards, and snowstorms, each causing >$5 million in damages, occurred during 1949-2003, and their losses totaled $35.2 billion (2003 dollars). Catastrophic winter storms occurred in most parts of the contiguous United States, but were concentrated in the eastern half of the nation where 88% of all storm losses occurred. They were most frequent in the Northeast climate district (95 storms), and were least frequent in the West district (14 catastrophic storms). The annual average number of storms is 3.7 with a 1-year high of nine storms, and one year had no storms. Temporal distributions of storms and their losses exhibited considerable spatial variability across the nation. For example, when storms were very frequent in the Northeast, they were infrequent elsewhere, a result of spatial differ- ences in storm-producing weather conditions over time. The time distribution of the nation's 202 storms during 1949-2003 had a sizable downward trend, whereas the nation's storm losses had a major upward trend for the 55-year period. This increase over time in losses, given the decrease in storm incidences, was a result of significant temporal increases in storm sizes and storm intensities. Increases in storm intensities were small in the northern sections of the nation, but doubled across the southern two-thirds of the nation, reflecting a climatic shift in conditions producing intense winter storms.

Protective capacity of mangroves during tropical storms: a case study from ‘Wilma’ and ‘Gamma’ in Belize

Globally threatened mangrove forest habitat is often considered an important buffer protecting coastlines from wave and storm impacts and coastal erosion. However, there is little empirical data quantifying the protective effects of mangroves during storms, primarily because of the difficulty of predicting where and when a storm will intersect the shoreline, to facilitate data collection before and after storm events. In 2005, opportunistic results from an ongoing study quanti- fying differences between intact and cleared mangrove areas on Turneffe Atoll, Belize, provided such pre- and post-storm data from tropical storms 'Wilma' (later a Category 5 Hurricane) and 'Gamma'. We compared differences in equipment retention rates of 3 types of experimental devices previously installed in adjacent intact and cleared mangrove areas. Retention rates were greater in intact mangrove areas, empirically demonstrating the protective capacity of mangroves during moderate magnitude storm events. The results support the assumption that removal of mangroves diminishes coastal protection not only during catastrophic storm events such as hurricanes or tsunamis, but also during less energetic but more frequent events, such as tropical storms. This high- lights the importance of improved coastal zone management, as storm events may increase in frequency and intensity with changing climate, and coastal mangrove forest habitats continue to decline in size and number.

Catastrophic winter storms: An escalating problem

Winter storms are a major weather problem in the USA and their losses have been rapidly increasing. A total of 202 catastrophic winter storms, each causing more than $1 million in damages, occurred during 1949–2003, and their losses totaled $35.2 billion (2003 dollars). Catastrophic winter storms occurred in most parts of the contiguous USA, but were concentrated in the eastern half of the nation where 88% of all storm losses occurred. They were most frequent in the Northeast climate district (95 storms), and were least frequent in the West district (14 catastrophic storms). The annual average number of storms is 3.7 with a 1-year high of 9 storms, and 1 year had no storms. Temporal distributions of storms and their losses exhibited considerable spatial variability across the nation. For example, when storms were very frequent in the Northeast, they were infrequent elsewhere, a result of spatial differences in storm-producing synoptic weather conditions over time. The time distribution of the nation’s 202 storms during 1949–2003 had a sizable downward trend, whereas the nation’s storm losses had a major upward trend for the 55-year period. This increase over time in losses, given the decrease in storm incidences, was a result of significant temporal increases in storm sizes and storm intensities. Increases in storm intensities were small in the northern sections of the nation, but doubled across the southern two-thirds of the nation, reflecting a climatic shift in conditions producing intense winter storms.

Moving Testimonies: Documentary, "Truth," and Reconciliation

Moving Testimonies: Documentary, "Truth," and Reconciliation Janet Walker In 1993 Linda Williams observed the paradox of a historical moment characterized by "a remarkable hunger for documentary images of the real" and at the same time a "loss of faith in the objectivity of the image" (10). The present situation is increasingly inconsonant. There is this appetite for testimony, and yet our understanding deepens of memory's constructive aspect. "Remembering the gist of what happened [but mistaking the precise facts] is an economical way of storing the most important aspects of our experience without cluttering memory with trivial details," summarize Daniel Schacter and Donna Rose Addis in a recent issue of the science weekly Nature (27). First the hunger. The will and the possibility—through increasingly available and capacious capture and storage techniques—to collect and authorize visual history testimony have never been greater.1 The University of Southern California Shoah Foundation Institute intends its 52,000 videotaped interviews with Holocaust survivors and witnesses as an educational legacy for all time. South Africa's Truth and Reconciliation Commission (it seems important to stray from U.S. media and politics better to understand them) oversaw the compilation of a testimonial archive that now includes 22,000 written testimonies, of which some 2,000 were videotaped during public committee hearings.2 Documentary filmmaking has followed the testimonial compulsion. Whereas in past decades documentary scholars have tended to view the "talking head" as evidence of a lack of imagination on the part of film and filmmaker, now, nearly fifty years after the advent of direct cinema, filmmakers, film scholars, and other historians are rediscovering the expressive power of direct address. Ten documentary films derived from testimonies in its video history archive have been produced by the Shoah Foundation.3 The Academy of Motion Picture Arts and Sciences in the United States has taken notice. Over the last dozen years Into the Arms of Strangers: Stories of the Kindertransport (2000), The Last Days (1998), and Anne Frank Remembered (1995)—all involving passionate testimony about past events, all on the subject of the Holocaust—have garnered Oscars for best documentary, as has Errol Morris's The Fog of War: Eleven Lessons from the Life of Robert S. McNamara (2003), a compelling and stylish documentary consisting, [End Page 87] improbably, of a feature-length interview with former U.S. Secretary of Defense Robert McNamara. Fahrenheit 9/11 (2004) also accrues much of its force from the words of the people Michael Moore encounters, including, memorably, a woman unable to comprehend the death of her son, a soldier in the Iraq War. Spike Lee's magisterial When the Levees Broke: A Requiem in Four Acts (five, on DVD, 2006), marked the one-year anniversary of the environmental and governmental devastation of people and property on the U.S. Gulf Coast through an affecting mosaic of witness testimony intercut with footage of the catastrophic storm and surge. Here a man describes pushing his wheelchair-bound mother out of the shelter of New Orleans' Superdome stadium way down to the end where she could be among the first to be evacuated when the buses arrived. After awhile, he tells us, her constant questions ceased; his mother had died where she sat. The buses came four days later. This is all to appreciate humanitarian achievements in video testimony over the far more common instances around the world, including in the United States, where testimony has been unheard, inhibited, or strictly disallowed. George Stoney, Judith Helfand, and Susanne Rostock's The Uprising of '34 (1995) listens to people speaking publicly for the first time in over sixty years about a massive Southern cotton mill workers' strike and the gag order that was imposed as a condition of returning to work. Although the writer Ba Jin has called for the establishment of a Cultural Revolution museum in China, there remains a prohibition against speaking openly about various different atrocities, including the mass famine of the Great Leap Forward, the massacre at Tiananmen...

Sensitivity of Ice Storms in the Southeastern United States to Atlantic SST—Insights from a Case Study of the December 2002 Storm

Abstract Meteorological observations and model simulations are used to show that the catastrophic ice storm of 4–5 December 2002 in the southeastern United States resulted from the combination of a classic winter storm and a warm sea surface temperature (SST) anomaly in the western Atlantic Ocean. At the time of the storm, observations show that the Atlantic SST near the southeastern U.S. coast was 1.0°–1.5°C warmer than its multiyear mean. The impact of this anomalous SST on the ice accumulation of the ice storm was evaluated with the Regional Atmospheric Modeling System. The model shows that a warmer ocean leads to the conversion of more snow into freezing rain while not significantly affecting the inland surface temperature. Conversely, a cooler ocean produces mostly snowfall and less freezing rain. A similar trend is obtained by statistically comparing observations of ice storms in the last decade with weekly mean Atlantic SSTs. The SST during an ice storm is significantly and positively correlated with a deeper and warmer melting layer.

WINDSTORM DISTURBANCE EFFECTS ON FOREST STRUCTURE AND BLACK BEAR DENS IN SOUTHEAST ALASKA

We examined the relationships among forest susceptibility to windstorm damage, forest structure, and black bear winter den site selection in the coastal temperate rain forests of southeastern Alaska, USA. Forest susceptibility to maritime windstorms was determined by applying a wind‐disturbance model (WINDSTORM) to two study areas where bear dens had been identified by radio telemetry. We evaluated model predictions for forest structure against field data for one study area. As predicted, forests in wind‐protected landscapes contained features indicative of later stages of forest development where larger and older trees are more abundant. By contrast, forests located in storm‐susceptible locations contained higher tree densities, less variation in tree diameters, smaller trees, and less evidence of large, old trees with heart rot. Analysis of habitat use relative to its availability on the landscape indicates that bears selected wind‐protected landscapes over storm‐prone landscapes in both study areas for winter dens. The majority (58%) of den sites were located in forests most protected from catastrophic storm effects. By contrast, only 6% were located in forests most exposed to storm damage. Results suggest that forests most protected from catastrophic windstorm disturbance contain more suitable overwinter habitat for black bears as evidenced by den site selection.

Modeling and Performance Assessment of Contraflow Evacuation Termination Points

About 20 hurricane evacuation contraflow segments are planned for use in the United States. When activated, these routes will serve as lifelines for people fleeing the potential destruction of approaching storms. The termination points of these segments are critical because they move traffic from the reverse-flowing lane into the normal flow direction. They are also thought to affect the overall effectiveness of the sections significantly because they can regulate the amount of volume that exits the section. The research effort described in this paper was undertaken to assess and compare the operational characteristics of contraflow evacuation termination point designs that would be used under threat from catastrophic storms. Among the developments of the research was an approach and set of assumptions for using CORSIM to model contraflowing freeway traffic under evacuation conditions. These models were used to assess and rank the planned termination designs comparatively and to identify the factors that made some designs more effective than others, including the effect of reducing traffic volumes before the termination. The quantification of the operations revealed several important concepts relative to the use of contraflow evacuation segments. First, it is advantageous to maintain all lanes through the termination point with split rather than merge designs. Also, it is advantageous to reduce the volume entering the termination point by maintaining exit points along the route. The study suggests that merge zones located after exits, instead of before them, and the use of channelization or separation devices well in advance of forced maneuvers can enhance the quality of the flow through the termination vicinity.

Modeling and Performance Assessment of Contraflow Evacuation Termination Points

About 20 hurricane evacuation contraflow segments are planned for use in the United States. When activated, these routes will serve as lifelines for people fleeing the potential destruction of approaching storms. The termination points of these segments are critical because they move traffic from the reverse-flowing lane into the normal flow direction. They are also thought to affect the overall effectiveness of the sections significantly because they can regulate the amount of volume that exits the section. The research effort described in this paper was undertaken to assess and compare the operational characteristics of contraflow evacuation termination point designs that would be used under threat from catastrophic storms. Among the developments of the research was an approach and set of assumptions for using CORSIM to model contraflowing freeway traffic under evacuation conditions. These models were used to assess and rank the planned termination designs comparatively and to identify the factors that ...

Geoinformation modeling of wind-induced surges on the northern–eastern Caspian Sea

Shallow north part of the Caspian Sea is part of the most important region of the Caspian Sea. The Northeast part. especially its coastal zone, is unexplored areas of the Caspian Sea. In last years the north part of the Caspian Sea became one of the main sources of pollution of the whole sea. For this reason it is necessary to investigate wind-induced level variations of water at northeast coast of Caspian sea and to reveal ecological damage.The role of mathematical modeling rather increases on the background of the shorted data because it allows numerical experiments in areas, there is not enough or at all not covered the measure data with significant expenditures.To solve the task there has been used the system equation theory of sallow water. Using this method has allowed to study storms of fluctuation in areas, where are absent measurements to simulate catastrophic storms of a situation and to determinate of zones of possible flooding of coast with various marks of a background sea level to make a real and forecast maps of flooding, and also to definite to region of the zones of flooding and maximal marks storm surges.

ROSS AND BUDE FORMATIONS (CARBONIFEROUS, IRELAND AND ENGLAND): REINTERPRETED AS LAKE‐SHELF TURBIDITES

The Ross Formation (Namurian, Ireland) and the near‐identical Bude Formation (Westphalian, England), both amply described in the literature, are used by oil companies as deep‐sea‐fan reservoir analogues. However, the Ross Formation is reinterpreted here, like the Bude Formation in recent publications, to be composed of river‐fed turbidites deposited on the wave‐influenced northern shelf of a Variscan foreland‐basin lake, which also had a southern flysch trough.Key features of these formations are: (i) two classes of thin (≤ 0.4m) sandstone “event bed” in shale comprising (a) structureless turbidite‐like beds, and (b) rippled beds with combined‐flow ripples and/or hummocky cross‐stratification, neither structure having previously been reported from the Ross Formation; (ii) “trademark” tabular packets (1–10 m) of amalgamated event beds which interfinger laterally with mudstones; (iii) sharp packet bases and tops; (iv) rare sinuous channel fills; and (v) rare thick (1–10m) shale units, each containing a thin (cm‐dm) fossiliferous band.The fossil bands are interpreted here as maximum flooding surfaces, reflecting glacioeustatic marine incursions over the lake spill point (sill), forcing the lake to rise and to turn marine or strongly brackish; these bands define Galloway‐type depositional sequences 50–100 m thick. During eustatic falls, the lake was forced down to sill level, where it perched and turned fresh (desalination). Intervals containing sandstone packets are attributed to the falling‐stage and lowstand systems tracts, each packet representing a higher‐order lowstand systems tract. Packets are interpreted as tongue shaped, supplied by river‐fed underflows. Packet bases (sharp) represent the storm‐wave‐graded equilibrium shelf profile, glacioeustatically forced to its lowstand position. On this erosion surface were deposited underflow turbidites produced by floods in the catchment. Occasional catastrophic storms on the lake shaved these turbidites and interfingering fair‐weather muds back down to the equilibrium level, leaving behind a subsidence‐accommodated increment whose surface was sculpted by storm wind and wave currents, forming hummocks, combined‐flow ripples and erosional megaflutes. Whenever a river‐fed underflow accompanied one of these storms, the resulting highly erosive combined flow carved a sinuous channel on the wave‐sculpted equilibrium surface. Sandstone‐shale intervals separating the sandstone packets are interpreted as transgressive‐ and highstand systems tracts. They contain both turbidites and wave‐modified turbidites (rippled beds), deposited on the out‐of‐equilibrium drowned shelf.A gradual rotation in sole‐mark direction with time in both formations is attributed to a reversal of Coriolis deflection as the plate drifted north across the equator, causing underflows (deflected along‐shelf geostrophically) to flow first NEwards and then SWwards on an inferred SE‐facing shelf.The lack of evidence for emergence in the Ross and Bude Formations, in spite of the great thicknesses (460m and 1,290m, respectively) of these shallow‐water deposits, is attributed to regulation of minimum water depth firstly by the lake sill blocking eustatically‐forced exposure, and secondly by storm grading, preventing emergence by sedimentation.

Man and environment in the marsh area of Schleswig–Holstein from Roman until late Medieval times

Reconstruction of coastal development, environment and settlement history is one of the main objectives of coastal archaeology in Schleswig–Holstein. The fieldwork program concentrated until 1975 on the excavation of dwelling mounds, and after that on the reconstruction of the landscape and settlement history of large areas. Cultural elements of the coastal area were mapped in several surveys integrating archaeological, geological and palaeobotanical aspects on the island of Sylt (Archsum project), in the North Frisian tidal flats (Norderhever project), on the Eiderstedt penisula, and in Dithmarschen. According to this kind of research, environmental changes dominated the settlement history and settlement pattern in the 1st millennium AD. Archaeological finds and excavations indicate that the earliest coastal settlements were founded in the salt marshes of Schleswig–Holstein in the early Roman period. In Dithmarschen as well as in the southern part of Eiderstedt the river marshes and salt marshes were densely populated during this period. In the 1st and 2nd century AD the inhabitation of the area took place in a phase of lowering of the sea level. The settlements were erected on the natural surface of the coastal marshland, preferably on elevated areas. Thereafter, a rising sea level and intensified flooding led to the abandonment of some settlements. At other localities the inhabitants protected themselves against the storm surges by the construction of dwelling mounds, so-called Wurten. The first phase of inhabitation of the coastal marshland ended at about AD 450. A second phase of inhabitation of the coastal marshes began in the middle or late 7th century AD. It started with new settlements on the natural land surface of the marshland and was followed by as second phase of Wurt construction. The present-day North Frisian tidal flat area was covered with extended peat bogs and could not be inhabited before high Medieval times. Starting with this period the natural landscape changed to a cultural landscape. Cooperatives of peasants and the parishes played an important role in this process. Dikes were built and deep seated areas were drained and cultivated. In the late Middle Ages catastrophic storm floods had terrible effects: the sea destroyed large parts of the North Frisian Utlande. Remnants of this period like Warften, dikes, field pattern, and churches, are still visible in the present-day tidal flats. The unfavourable combination of human activities (peat cutting for salt production) and natural geological processes was responsible for the catastrophic floods of late Medieval times. Cultural monuments of this evolution are still preserved in the coastal landscape. The protection of the Cultural Heritage is of high value for the future.

Tunnel development over a 12 year period in a semi‐arid catchment of the Loess Plateau, China

AbstractThe tunnel systems in a semi‐arid catchment of the Loess Plateau of China were repeatedly surveyed prior to the rainy seasons of 1989, 1999 and 2001. The surveys aimed to: (1) measure tunnel development over the 12 year period 1989–2001; (2) explore how the physiographical conditions affect the spatio‐temporal variability of tunnel development; and (3) to identify the geomorphic processes associated with tunnel development. The ultimate goal was to quantify the geomorphic significance of tunnel systems in the catchment. Over the 12 year period, the number of tunnel inlets was more than doubled and most of the newly increased inlets were initiated in the few catastrophic storm events. However, tunnel enlargement can occur in storm or inter‐storm periods, mainly through earth falls and slumps in inlets, and water erosion and roof cave‐in collapses in tunnel paths. Tunnel development varied with material properties, land uses and topographic conditions. Net tunnel erosion may contribute at least 25–30% of the catchment sediment yield and was mainly produced by the initiation and enlargement of tunnel inlets rather than tunnel paths. To protect the areas against tunnel erosion, terracing of the upper slopes seems to be more effective than planting vegetation on the lower slopes. Copyright © 2003 John Wiley & Sons, Ltd.

Quaternary deposits and landscape evolution of the central Blue Ridge of Virginia

A catastrophic storm that struck the central Virginia Blue Ridge Mountains in June 1995 delivered over 775 mm (30.5 in) of rain in 16 h. The deluge triggered more than 1000 slope failures; and stream channels and debris fans were deeply incised, exposing the stratigraphy of earlier mass movement and fluvial deposits. The synthesis of data obtained from detailed pollen studies and 39 radiometrically dated surficial deposits in the Rapidan basin gives new insights into Quaternary climatic change and landscape evolution of the central Blue Ridge Mountains. The oldest depositional landforms in the study area are fluvial terraces. Their deposits have weathering characteristics similar to both early Pleistocene and late Tertiary terrace surfaces located near the Fall Zone of Virginia. Terraces of similar ages are also present in nearby basins and suggest regional incision of streams in the area since early Pleistocene–late Tertiary time. The oldest debris-flow deposits in the study area are much older than Wisconsinan glaciation as indicated by 2.5YR colors, thick argillic horizons, and fully disintegrated granitic cobbles. Radiocarbon dating indicates that debris flow activity since 25,000 YBP has recurred, on average, at least every 2500 years. The presence of stratified slope deposits, emplaced from 27,410 through 15,800 YBP, indicates hillslope stripping and reduced vegetation cover on upland slopes during the Wisconsinan glacial maximum. Regolith generated from mechanical weathering during the Pleistocene collected in low-order stream channels and was episodically delivered to the valley floor by debris flows. Debris fans prograded onto flood plains during the late Pleistocene but have been incised by Holocene stream entrenchment. The fan incision allows Holocene debris flows to largely bypass many of the higher elevation debris fan surfaces and deposit onto the topographically lower surfaces. These episodic, high-magnitude storm events are responsible for transporting approximately half of the sediment from high gradient, low-order drainage basins to debris fans and flood plains.

Population dynamics of Common Sandpipers Actitis hypoleucos in the Peak District of Derbyshire – a different decade

Capsule A report of the failure of a population to recover from a catastrophic snow storm. Aims To examine why our study population of Common Sandpipers failed to recover from a sharp drop in 1989, caused by a severe late April snowstorm, when it had recovered from a similar event in 1981. Methods Populations were censused weekly, with extra visits to ring adults and chicks. Hatching was assumed to have occurred if adults alarmed, and fledging if alarming continued for three weeks. Data from 1989–99 and 1979–88 were compared. Results The recruitment of new adults to the population was much lower, but these recruits mostly came from other breeding areas, and the local recruits appeared to go elsewhere. Median dispersal distance is estimated as 3.3 km, sufficient to take most locally produced young adults outside the study area. Conclusions We do not know if poorer breeding in the source populations for our birds, or poorer survival of first year birds over winter in West Africa, is the cause of the failure of this population to recover in the 1990s.

An assessment of stem breakage and the reduction in timber volume and value recovery resulting from a catastrophic storm: an Irish case study

Summary This article reports on a study initiated to assess in detail the volume and value recovery losses associated with damage resulting from a 1998 catastrophic storm in Ireland. The results are based on a 0.39 ha representative site in Swanlinbar forest, County Cavan. Detailed analysis showed that the loss in recovery in the broken stems amounted to a volume loss of 27 per cent with an associated value loss of 29 per cent. On a stand basis this corresponded to 13.4 per cent of stems broken, resulting in a 2.6 per cent volume loss. The value loss of IR£0.87 per cubic metre recovered amounted to IR£310.94/ha or 2.8 per cent of the potential revenue. During the milling of the blown timber, no additional loss was incurred as a result of log defects resulting from storm damage. A significant relationship between diameter at breast height (d.b.h.) and the occurrence of breakage was established, with the smaller diameter trees more likely to snap than those with larger d.b.h. measurements. No significant relationship between the location of the breakage along the stem and the d.b.h. of the trees was found.

Microbialites in a modern lagoonal environment: nature and distribution, Tikehau atoll (French Polynesia)

Microbialites, including stromatolitic structures, gelatinous masses and mats develop in Tikehau lagoon (Tuamotu, French Polynesia), on the flanks and slopes of numerous pinnacles and ‘motu’ islets between 0 and 25 m deep, on coral colonies, algal tufts or on lagoonal sediments. Individual stromatolitic structures consist of hemispherical domes and are produced by monospecific populations of filamentous cyanobacteria belonging to three distinctive Phormidium species, Symploca, and possibly to one new species of Schizothrix. Gelatinous masses hanging from the ceiling of caverns are produced by Phormidium laysanense. Microbial mats are well developed at all depths on pinnacle slopes and are produced by either monospecific or mixed cyanobacterial populations. The study of micro- and ultrastructure of stromatolites reveals that they result both from trapping and binding of sediments and from carbonate precipitation. In addition to phototrophic biomineralization, pervasive carbonate precipitation occurred in association with decaying organic matter. The basic constructional elements of the precipitated carbonate consist of 0.1–0.2-μm rounded bodies that form very fine anhedral to subhedral micrite; their surfaces comprise extremely small carbonate granules (20–50 nm). Gradual changes (ageing) in the ultrastructure of carbonate precipitates include the precipitation of successive euhedral calcite layers around these grains. Widespread development of microbialites in this pristine lagoonal environment results from rapid blooms of microbial benthic communities, possibly induced by temporary and local nutrient pulses. Nutrients seem to undergo a restricted circulation between the sediment and pinnacle reef frameworks. Pinnacles and reef islets are repeatedly affected by catastrophic storm events which cause redistribution of sediments and nutrients.