The people of Jabuticabeira II: reconstruction of the way of life in a Brazilian shellmound

Sambaquis are huge shellmounds built along almost the entire Brazilian coast between 8000 and 600 years ago. In the present article, 14 osteological markers from 89 individuals excavated at the Sambaqui Jabuticabeira II (2890±55/2186±60 BP) are analyzed in order to reconstruct the population′s health status and way of life. The present palaeopathological findings (such as lower frequency of degenerative joint diseases in legs, as compared to arms, and the rarity of traumas) together with archaeological findings support the idea of nearby resource abundance and infrequent interpersonal competition. The presence of auditory exostoses mainly in males corroborates previous findings indicating the importance of marine resources. The low caries frequency and the high degrees of dental wear point to a diet poor in cariogenic food, and rich in abrasives such as sand, shell fragments and phytoliths. This suggests a broader diet, based on marine protein as well as plants, than previously thought. The etiology of cribra orbitalia could be explained by gastrointestinal parasites or other sources of physiological stress. These parasites, in turn, could have led to higher frequencies of infectious diseases, either by the debilitation of the immune system or by the direct contact with infectious agents. Despite the periods of illness various individuals experienced, the daily life among the builders of the Sambaqui Jabuticabeira II seems to have been relatively easy due to the abundance and predictability of resources and the paucity of violent traumas.     

Holocene vegetational and coastal environmental changes from the Lago Crispim record in northeastern Pará State, eastern Amazonia

Vegetational and coastal environmental changes have been interpreted from a 600cm long and 764014C yr B.P. old sediment core from Lago Crispim located in the northeastern Pará State in northern Brazil. The radiocarbon dated sediment core was studied by multi-element geochemistry, pollen and charcoal analysis.Holocene Atlantic sea-level rise caused an elevation of local water table, which allowed the formation of organic deposits in a probably former inter-dune valley. Dense, diverse and tall Amazon rain forest, and some restinga (coastal vegetation) covered the study area at the beginning of the record at 764014C yr B.P. Mangrove vegetation developed along rivers close to the core site at that time. Subsequent decrease in less mangrove vegetation near the study site indicates a sea-level regression, beginning since around 700014C yr B.P. Lower sea-levels probably favoured the formation of a local Mauritia/Mauritiella palm swamp at 662014C yr B.P. Oscillations of higher and lower sea-level stands probably changed the size of the local palm swamp area several times between 6620 and 363014C yr B.P. Sea-level transgression at around 363014C yr B.P., caused marked coastal environmental changes: the development of mangroves near the site, the replacement of the local palm swamp by a Cyperaceae swamp, the substitution of the surrounding former Amazon rain forest and some restinga vegetation mainly by salt marshes. High amount carbonised particles suggest a strong human impact by burning on the coastal ecosystems during this late Holocene period.Highest concentrations of NaCl and also Ca, Mg and K in the upper sediment core indicate that the Atlantic was close during the late Holocene period. The core site, which is today 500m from the coastline and only 1-2m above modern sea-level, was apparently never reached by marine excursions during the Holocene.Less representation of mangrove since ca. 184014C yr B.P., may be related due to a slightly lower sea-level or to human impact in the study region. The modern shallow lake seems to be formed recently by road construction, forming an artificial dam.     

The Holocene treeline in the northern Andes (Ecuador): First evidence from soil charcoal

Indications for the speed and timing of past altitudinal treeline shifts are often contradictory. Partly, this may be due to interpretation difficulties of pollen records, which are generally regional rather than local proxies. We used pedoanthracology, the identification and dating of macroscopic soil charcoal, to study vegetation history around the treeline in the northern Ecuadorian Andes. Pedoanthracology offers a complementary method to pollen-based vegetation reconstructions by providing records with high spatial detail on a local scale. The modern vegetation is tussock grass páramo (tropical alpine vegetation) and upper montane cloud forest, and the treeline is located at ca. 3600 m. Charcoal was collected from soils in the páramo (at 3890 and 3810 m) and in the forest (at 3540 m), and represents a sequence for the entire Holocene.The presence of páramo taxa throughout all three soil profiles, especially in combination with the absence of forest taxa, shows that the treeline in the study area has moved up to its present position only late in the Holocene (after ca. 5850 cal years BP). The treeline may have been situated between 3600 m and 3800 m at some time after ca. 4900 cal years BP, or it may never have been higher than it is today. The presence of charcoal throughout the profiles also shows that fires have occurred in this area at least since the beginning of the Holocene.These results contradict interpretations of palaeological data from Colombia, which suggest a rapid treeline rise at the Pleistocene–Holocene transition. They also contradict the hypothesis that man-made fires have destroyed large extents of forest above the modern treeline. Instead, páramo fires have probably contributed to the slowness of treeline rise during the Holocene.     

Pradosia restingae sp. nov. from the Atlantic forest,Brazil

Pradosia restingae Terra‐Araujo, a new species of Sapotaceae (Chrysophylloideae) from the Brazilian Atlantic forest is described and illustrated. It is only known from the southern coast of the State Rio Grande do Norte and is likely restricted to the coastal sand dune ecosystem, locally known as the restinga forest, from which the epithet is derived. The species is naturally common, but due the low number of known subpopulations we assign P. restingae a preliminary conservation status of ‘Endangered’ (EN).     

New records, threatens and conservation status for Dichotomius schiffleri Vaz-de-Mello, Louzada & Gavino (Coleoptera: Scarabaeidae): an endangered dung beetle species from Brazilian atlantic forest ecosystems

Dichotomius schiffleri Vaz-de-Mello et al is often cited as endemic to the preserved coastal sandy-dune vegetation (restinga) of Guriri Island, Espírito Santo state, and is included in the Brazilian List of Endangered Fauna as "critically endangered" (CR). However, we recorded its occurrence in twelve additional sites along the coasts of Espírito Santo, Bahia, Sergipe and Pernambuco. The geographic distribution of D. schiffleri is limited to the coastal Atlantic Forest domain, mainly in preserved restinga patches. We recommend that D. schiffleri remains in the List of Endangered species, but in the "endangered" (EN) category, according to the IUCN criteria.     

Restoration of a Restinga Sandy Coastal Plain in Brazil: Survival and Growth of Planted Woody Species

In this article we report the results of an experiment introducing 17 native shrub and tree species into a Brazilian restinga (i.e., coastal sandy plain vegetation). Restingas have been affected by human impact for about 8,000 years, and human occupation for housing, tourism, and land speculation has recently increased in such a way that there is a need for conservation of remnant patches and restoration of degraded areas throughout the coast to protect biodiversity. Our study site is a remnant located in Rio de Janeiro, the second largest city in the country, and has been subjected in the past to deforestation, man‐made fire, and sand extraction. Although trees and shrubs predominantly compose natural restinga vegetation, local vegetation after impact was replaced by an exotic grass cover, which meant a drastic reduction in species richness. Thus, in this experiment we removed the grass cover, introduced shrub and tree species, and monitored survival and growth of 20 plants per species for 2 years. Despite the adversities imposed by the nutrient‐poor sandy soil, 70% of the species showed high survival percentage and considerable growth. This report on restoration initiatives in the restingas points out the viability of shrub and tree plantation following exotic grass removal as a strategy to restore Brazilian coastal vegetation.     

Landscape structural analysis of the Lençóis Maranhenses national park: implications for conservation

Our work evaluated the anthropic effects on the landscape structure of the Lençóis Maranhenses National Park (LMNP) and its Buffer Zone, and proposed strategies for the region’s conservation. LMNP is an important protected area in Brazilian north coast which protects a unique wetland ecosystem composed of sand dunes fields and a coastal vegetation called restinga. Supervised mapping of LMNP and a surrounding buffer of 3 km was carried out through high resolution and fine scale (1:5000) satellite images. The mapped area was subdivided in 1000 ha hexagonal Analysis Units (AU) and the following landscape metrics were calculated for each one of them: cover area (CA) of each soil cover class - dune fields (CA-DUNES), water bodies (CA-WATER), dense restinga (CADENSE), scattered restinga (CA-SCATTER), grassland (CA-SANDY), mangroves (CA-MANG), anthropogenic activity (CA-ANTRO) and, secondary vegetation (CA-SECOND); Landscape Shannon Diversity Index (SHDI), and; percentage of native vegetation cover (NV−COV). Pearson correlations were performed between the CA of each class and SHDI to identify the classes most correlated to CA-ANTRO. Our results showed that anthropic classes (crops, trails, and villages) had a stronger correlation (Pearson Correlation, r ≈ 0.65) with phytophysiognomies of dense restinga, secondary vegetation and SHDI, thus indicating that the land use conversion occurs in dense restinga areas and promotes vegetation secondarization, as well as increasing fragmentation. At least, 42% of the dense restinga habitats was destroyed due to human activities. Five conservation and restoration strategies were proposed in a local scale depending on the percentage of native vegetation cover on each AU, from the most to less conserved: (a) only conservation; (b) conservation with management; (c) management; (d) management and restoration; and, (e) restoration. The implementation of Agroforestry Systems with agro-successional restoration goals was recommended as an alternative for land use.     

Population structure of Litopenaeus schmitti (Decapoda: Penaeidae) from the Brazilian coast identified using six polymorphic microsatellite loci

The population structure of the only Litopenaeus species occurring in Brazilian waters, the white shrimp L. schmitti, was surveyed by screening six microsatellite loci. High diversity (HE = 0.863; average number of alleles per locus = 37.8) was found across eight geographical locations (2 degrees S to 27 degrees S). Estimates of overall FST(0.0060) were low but significantly different from zero (P < 0.05). FST pairwise estimates and amova revealed a significant discontinuity around a major biogeographical boundary, near Cabo Frio, at 23 degrees S. This separation may have been caused either by historical or on-going hydrogeographical and/or selective factors.     

Frog species richness, composition and beta-diversity in coastal Brazilian restinga habitats.

We studied the species richness and composition of frogs in 10 restinga habitats (sand dune environments dominated by herbaceous and shrubby vegetation) along approximately 1500 km of coastal areas of three Brazilian States: Rio de Janeiro (Grumari, Maricá, Massambaba, Jurubatiba and Grussaí), Espírito Santo (Praia das Neves and Setiba) and Bahia (Prado and Trancoso). We estimated beta-diversity and similarity among areas and related these parameters to geographic distance between areas. All areas were surveyed with a similar sampling procedure. We found 28 frog species belonging to the families Hylidae, Microhylidae, Leptodactylidae and Bufonidae. Frogs in restingas were in general nocturnal with no strictly diurnal species. The richest restinga was Praia das Neves (13 species), followed by Grussaí and Trancoso (eight species in each). The commonest species in the restingas was Scinax alter (found in eight restingas), followed by Aparasphenodon brunoi (seven areas). Our data shows that richness and composition of frog communities vary consistently along the eastern Brazilian coast and, in part, the rate of species turnover is affected by the distance among areas. Geographic distance explained approximately 12% of species turnover in restingas and about 9.5% of similarity among frog assemblages. Although geographic distance somewhat affects frog assemblages, other factors (e.g. historical factors, disturbances) seem to be also involved in explaining present frog assemblage composition in each area and species turnover among areas. The frog fauna along restinga habitats was significantly nested (matrix community temperature = 26.13 degrees; p = 0.007). Our data also showed that the most hospitable restinga was Praia das Neves and indicated that this area should be protected as a conservation unit. Frog assemblage of each area seems to partially represent a nested subset of the original assemblage, although we should not ignore the importance of historical factors. This nestedness pattern, in part, probably results from the intensive fragmentation of restinga habitats. Possibly, many frog species may have been lost in some studied areas as a result of the extensive habitat degradation to which restinga habitats are presently exposed.     

Fire and late-Holocene expansion of Quercus ilex and Pinus pinaster on Corsica

Abstract. The natural origin of old Quercus ilex (holm oak) forests on the west coast of Corsica is a matter of dispute. This paper discusses the use of pedoanthracology, especially adapted to approach topics in palaeoecology requiring a high spatial precision. It also shows the importance of fire in vegetation change during the Holocene. Pedoanthracology relies on botanical identification and AMS ¹⁴C dating of micro-charcoal found in soil. Three test pits were dug in a forest currently protected within the ‘Man and Biosphere’ program. These pits yielded large quantities of charcoal. There is evidence that Pinus nigra ssp. laricio (laricio pine) and understorey heather species (Ericaceae) played an important role in the vegetation at the beginning of the Subatlantic (ca. 2500 BP). The importance of Pinus pinaster (maritime pine), Quercus ilex and a few mesophilic species increased between 2000 and 1000 BP. Charcoal fragments found in the soil show the role of fire in the vegetation changes recorded. The late expansion of P. pinaster results from a high fire frequency. The hypothesis proposed in the paper suggests that fires destroyed the remaining toxic humus that had accumulated during the millennia which preceded the arrival of Q. ilex to our study sites. The late development of holm oak forest is a combination of the migration of the species and the increase of fire frequency since 2500 BP, most probably resulting from slash-and-burn agriculture.     

Ecosystem carbon stocks of mangrove forests along the Pacific and Caribbean coasts of Honduras

Among the many ecosystem services provided by mangrove ecosystems, their role in carbon (C) sequestration and storage is quite high compared to other tropical forests. Mangrove forests occupy less than 1 % of tropical forested areas but account for approximately 3 % of global carbon sequestration by tropical forests. Yet there remain many areas where little data on the size and variation of mangrove C stocks exist. To address this gap and examine the range of C stocks in mangroves at landscape scales, we quantified C stocks of Honduran mangroves along the Pacific and Caribbean coasts and the Bay Islands. We also examined differences in ecosystem C stocks due to size and structure of mangrove vegetation found in Honduras. Ecosystem C stocks ranged from 570 Mg C ha^?1 in the Pacific coast to ~1000 Mg C ha^?1 in Caribbean coast and the Bay Islands. Ecosystem C stocks on the basis of mangrove structure were 1200, 800 and 900 Mg C ha^?1, in low, medium and tall mangroves, respectively. We did not find significant differences in ecosystem C stocks on the basis of location (Pacific coast, Caribbean coast and Bay Islands) or mangrove type (low, medium and tall). Mangrove soils represented the single largest pool of total C in these ecosystems, with 87, 81 and 94 % at the Pacific coast, Caribbean coast and the Bay Islands, respectively. While there were no significant differences in total ecosystem stocks among mangrove types, there were differences in where carbon is stored. Mangrove soils among low, medium and tall mangroves contained 99, 93 and 80 % of the total ecosystem C stocks. In addition, we found a small yet significant negative correlation between vegetation C pools and pore water salinity and pH at the sampled sites. Conversion of mangroves into other land use types such as aquaculture or agriculture could result in loses of these soil C reserves due to mineralization and oxidation. Coupled with their other ecosystem services, an understanding of the size of mangrove ecosystem C stocks underscores their values in the formulation of conservation and climate change mitigation strategies in Central America.     

Effects of Degradation and Replacement of Southern Brazilian Coastal Sandy Vegetation on the Dung Beetles (Coleoptera: Scarabaeidae)

In this paper we address the effects of anthropogenic disturbance and replacement of Brazilian Coastal sandy vegetation (restingas) on dung beetles communities. We sampled dung beetles in the four main vegetative physiognomies of Guriri Island, Espírito Santo State: forest restinga, restinga Clusia, disturbed restinga (from burning events), and pastures. We placed four sets of two pitfall traps (baited with horse and human dung) in four independent areas of each vegetation type, and collected 14,534 individuals of 13 dung beetle species. Neither log₁₀ of individuals nor log₁₀ of species richness were good predictors of restinga disturbance. However, a significant amount of variation in dung beetle abundance and richness could be explained by bait type. Ordination of these sites using hybrid multidimensional scaling revealed a gradient of habitat disturbance from undisturbed restinga samples to pasture. Dung beetle communities along this gradient demonstrated a complete turnover in species composition, from restinga‐specialists to invasive and generalists species respectively. This complete turnover signals the local extirpation of forest‐adapted species in disturbed and converted areas. Only a single dung beetle species in preserved restingas is protected by Brazilian law (Dichotomius schiffleri). Given the extent of the clearing of restinga habitat, the conservation status of dung beetles associated with restinga forest gives cause for concern.     

Holocene mangrove dynamics and sea-level changes in northern Brazil, inferences from the Taperebal core in northeastern Pará State

A 450 cm sediment core from Taperebal, in the mangrove region of northeastern Pará State in northern Brazil has been studied through pollen analysis in order to reconstruct mangrove development and dynamics and to infer relative sea-level (RSL) changes during the Holocene. Six AMS radiocarbon dates, which provide a somewhat limited age control with some uncertainties, suggest early and late Holocene deposits interrupted by a hiatus between them. A patchy vegetation of coastal Amazon rain forest, restinga, salt marsh and some mangrove, which was dominated by Avicennia, covered the study area during the early Holocene period. The occurrence of an early Avicennia dominated mangrove phase has not been reported so far from other sites in northern Brazil. During the mid Holocene mangroves mostly replaced the former coastal Amazon rain forest, restinga and some salt marsh vegetation, reflecting the rise in the RSL. Rhizophora trees expanded markedly and Avicennia became rare. In the sediment core there is apparently a gap between the depths of 115 and 85 cm (possibly starting between 5900 and 5750 b.p.). The deposits above 85 cm are of modern age and were probably deposited during the last decades. This gap can be explained by the lowering of the RSL as is shown for other northern Brazilian coastal sites. The deposition of sediments during the last decades suggests that the modern RSL is high compared to other periods in the Holocene. Pollen data from these deposits show that Rhizophora trees dominate the mangrove forests, also indicating a high RSL.     

Impact of sea-level and climatic changes on the Amazon coastal wetlands during the late Holocene

Wetland dynamics in northern Brazil during the Holocene were studied by pollen analysis and AMS radiocarbon dating of three cores. Near the Amazon mouth region, covered mainly by primary Amazon coastal forest and herbaceous vegetation, the pollen record indicates the dominance of mangroves between 4800 and 1100 cal yr b.p. A contraction of the mangrove area and an expansion of herbaceous and fern vegetation occurred between 1100 and 750 cal yr b.p. The period between 750 and 200 cal yr b.p. is characterized by an expansion of mangrove and a decrease in herbaceous and fern vegetation. This trend continued until the present. On Atalaia Island, the sediment core indicates a period with poor pollen preservation between 830 and 630 cal yr b.p. Between 630 and 330 cal yr b.p., mangroves expanded. Later, up to 45 cal yr b.p., the mangrove area decreased and the herbaceous vegetation expanded. During the last hundred years, the relative sea-level rise most probably favored the mangrove expansion as far as the topographically highest sector on this island, while the herbaceous vegetation decreased. The pollen data from água Preta Lake indicate dry conditions, as reflected by the poor pollen preservation between 390 and 240 cal yr b.p. Between 240 and 60 cal yr b.p., restinga and Amazon coastal forest with palms dominated this region. For the last 120 years, the record indicates an expansion of the mangrove area. However, recent confinement of mangrove development to the topographically highest area, and the loss of mangrove areas on the lowest surfaces have led to a net loss of mangrove coverage during the last decades.     

Long-term dynamics of vegetation and disturbance of a southern boreal spruce swamp forest

Abstract. Analysis of pollen, charcoal and loss-on-ignition in peat cores from a Picea aèies-dominated swamp forest in central Sweden show the vegetation changes and disturbance patterns over 9500 yr. Six major sequences of local vegetation development are identified: (A) Pinus period, ca. 9500–7000 cal. BP; (B) Open mire period (ca. 7000–4500 cal. BP; (C) Betula period, ca. 4500–2300 cal. BP; (D) Picea period (ca. 2300–1000 cal. BP; (E) Human impact period (ca. 1000–100 cal. BP); and (F) Period of human abandonment during the last ca. 100 yr. The swamp forest has been highly dynamic in response to various natural and anthropogenic disturbance agencies. Several fires have heavily influenced the vegetation development. During the last ca. 900 yr human influence has been important, initially from grazing and trampling by domesticated animals (ca. 1000–500 cal. BP), and subsequently small-scale cereal growing (ca. 400–100 BP). Cutting, burning and animal browsing influenced the structure and dynamics of the swamp forest by creating a more open stand and suppressing tree regeneration. Recent cessation of human impact has led to increased tree regeneration and a denser swamp forest stand. The present high biodiversity, and subsequent conservation interest does not result from long-term stability or absence of fire and human impact. However, in spite of repeated disturbances, a continuity of old and senescent trees produced a forest type with abundant dead wood. With the relatively minor importance of fire over long periods of time, the swamp forest developed a structure maintaining a high biological diversity. An important issue for maintaining long-term biodiversity in the boreal landscape must be to create a mosaic where different forest types are present, with a variety of structures, substrates and processes, to provide a certain degree of freedom for species to move around in the landscape.     

Dinoturbation in Upper Jurassic siliciclastic levels at Cabo Mondego (Lusitanian Basin,Portugal): evidences in a fluvial-dominated deltaic succession

At Cabo Mondego (western central Portugal), the Upper Jurassic marine to coastal succession contains several stratigraphic levels preserving dinosaur footprints on the surface bedding plane, as well as convolute bedding and soft sediment injection structures interpreted as dinoturbation structures. At least nineteen new three-dimensional structures observed in cross-sections are interpreted as produced by dinosaur trampling. The identification of three-dimensional structures of dinosaur footprints provides an important complement to the information obtained from footprints preserved on single bedding surfaces, such as the substrate consistency, potential trackmaker identification, and the possibility to enhance the distinction of sauropods and tridactyl dinosaurs, and paleoenvironmental interpretations. In the lower part of the Arenitos da Boa Viagem Formation, eight levels of probable lowermost Kimmeridgian age (ca. 157–156 Ma), displaying the above-mentioned deformational structures, were analyzed in detail. They support interpretations concerning the relationship between the footprints and the substrate consistency at the time of their formation. Three distinct cohesiveness patterns, defined by the penetration of the feet from the paleosurface, are the result of different degrees of substrate cohesiveness. Identifying the trackmakers of levels belonging to the middle Oxfordian–lower Kimmeridgian has important implications for Late Jurassic ecosystem reconstructions, as the footprints observed in Cabo Mondego indicate a change in the morphotypes throughout the Upper Jurassic succession.     

Vegetation changes and human action from the Neolithic to the Bronze Age (7000–4000 B.P.) in Alicante,Spain, based on charcoal analysis

Charcoal analysis reveals various palaeo-ecological phases from the Neolithic to the Bronze Age. Agriculture starts about 7000 B.P. in favourable ecological conditions. Most of the charcoal spectra from sites on the coast represent thermomediterranean holm-oak forest; those from the inland mountains represent mesome-diterranean holm-oak forest. The Neolithic I Impressed Ware people were the first to clear the forest to plant their crops. This clearance of primary woodland resulted in the development of secondary vegetation of pine woods or scrub. The scrub reached its maximum during the Bell Beaker phase and Bronze Age in the Cova de les Cendres. In the Neolithic II open air sites, the percentages of Quercus ilex/coccifera remain high. This may be the result of a different exploitation of the land, or suitable conditions for the growth and survival of the vegetation.     

A new species of Achetaria (Plantaginaceae) from south-eastern Brazil

A new species, Achetaria latifolia V.C.Souza, is described and illustrated. It is characterized by its broadly ovate leaves, indument of stems and leaves of noncapitate hairs, and pubescent capsule. Achetaria latifolia is known only in the coastal dune-area of Cabo Frio region, Rio de Janeiro State, Brazil.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 73–75.     

Holocene vegetation–fire–climate linkages in northern Yellowstone National Park,USA

Yellowstone National Park has been an important location for paleoecologic studies that focus on the use of charcoal data to reconstruct past fire activity and on the role of climate variations in shaping past vegetation and fire regimes. One hypothesis, which has been explored in other parts of the western U.S., is the idea that present-day summer-dry and summer-wet precipitation regimes were intensified during the early Holocene as a result of greater-than-present summer insolation and its effect on atmospheric circulation patterns. In Yellowstone, this hypothesis was previously examined at two sites, one in summer-wet and one in summer-dry precipitation regions. The records showed variation in both fire and vegetation history that supported the hypothesis. We present a fire and vegetation history from Blacktail Pond, located in Pseudotsuga parkland in the transitional region. The Blacktail Pond data indicate the following ecological history: prior to 12,000 cal yr BP, the site supported tundra vegetation and fire episodes were infrequent. Between 12,000 and 11,000 cal yr BP, Picea–Pinus parkland was established and fire activity increased; these changes are consistent with increasing temperature, as a result of rising summer insolation. From 11,000 to 7600 cal yr BP, the presence of a closed forest of Pinus and some Picea is attributed to high levels of winter moisture, but high fire activity indicates that summers were drier than at present. After 7600 cal yr BP, the presence of forest and steppe vegetation in combination with high fire activity suggest that middle-Holocene conditions were warm and dry. The decrease in Picea and Betula in the last 4000 cal yr indicates continued drying in the late Holocene, although fire-episode frequency was relatively high until 2000 cal yr BP. The pollen data at Blacktail Pond and other low-elevation sites in the northern Rocky Mountains suggest a widespread vegetation response in summer-wet regions to effectively wetter conditions in the early Holocene and decreased moisture in the middle and late Holocene. In contrast, the more-variable fire history among the three sites implies either that (1) summer moisture stress and fire conditions are related to year-round moisture balance and not well predicted by the hypothesis, (2) the transitional area between summer-wet and summer-dry precipitation regimes experienced complicated shifts in effective moisture through time, and/or (3) fire-episode data have a limited source area that makes it difficult to separate local influences from regional climate changes in understanding long-term variations in fire-episode frequency.     

Holocene land uplift and its influence on fire history and ecosystem development in boreal Sweden

Lake Uddjaur in northern Sweden was formed as a consequence of non‐uniform glacio‐isostatic uplift in which a forested valley was gradually flooded and high elevation areas became islands. We hypothesized that small islands in Lake Uddjaur burnt through lightning strike more frequently when they were part of a large forested area compared to when they became true islands, and that this reduction in fire impact has enhanced the domination of late successional species and humus accumulation. Fire history and vegetation dynamics were studied by analysis of macroscopic charcoal (> 0.5 mm) and pollen in humus profiles from two islands. According to a model of isostatic uplift, the islands became gradually isolated from the mainland between ca. 2000 to 1000 BP, i.e. during the same time that fire impact declined. Prior to that, both islands were part of a Pinus‐Betula forest landscape affected by fires from ca. 5800 to ca. 1500 BP. Thereafter fire influence ceased and the islands became more strongly characterized by late successional species, e.g. Picea. This change was associated with substantial humus accumulation. The decreased fire influence on these islands contrasts with the regional increase in fire influence during the last 1000 yr. Long‐term influence of wildfire is important in vegetation dynamics and humus accumulation and, thus, post‐glacial isostatic land uplift can indirectly have a substantial influence on ecosystem development. Consequently, this effect should be further considered in long‐time ecosystem studies of areas with large, non‐uniform land uplift such as those found in northern Fennoscandia and eastern Canada.