Current Northern Limit Research Articles

Distribution of the northern pampas cat, Leopardus garleppi, in northern South America, confirmation of its presence in Colombia and genetic analysis of a controversial record from the country

Abstract The common name of pampas cat includes a complex of small Neotropical felid species found in various habitats of South America. Recently several species of this complex were proposed, but there are few records in the northernmost distribution of the continent, and reports of the pampas cat’s presence in Colombia have been ambiguous. Current northern limits of Leopardus garleppi are limited to the Andes of Ecuador. Here we present the northernmost record of the species, validating its presence in Colombia and review previous controversial records from the country. The new record is based on a road-killed specimen in a dry tropical forest ecosystem in the municipality of Mercaderes, Department of Cauca. Our morphological and genetic comparisons also shown that a previous record from Colombia supported by a single skin recently used to described a new species named Leopardus narinensis belong to Leopardus tigrinus. With the information compiled from new localities in Colombia and Ecuador, the known distribution range for L. garleppi is increased towards the northern part of South America into areas of Tropical Dry Forest. The distribution now includes 14 ecoregions from Colombia to Bolivia, and four in Colombia (Eastern Cordillera real montane forests, Northwestern Andean montane forests, Northern Andean paramo, and the Patía Valley dry forests), which correspond to similar ecosystems inhabited by the species in other Andean landscapes. The potential distribution hypothesis showed that the species has high suitability in large areas of southwestern Colombia (Nariño). With the recording of L. garleppi in Colombia, the number of extant felid species in the country has increased to seven.

Phenological Features of the Spongy Moth, Lymantria dispar (L.) (Lepidoptera: Erebidae), in the Northernmost Portions of Its Eurasian Range.

The spongy moth, Lymatria dispar, is a classic example of an invasive pest accidentally introduced from Europe to North America, where it has become one of the most serious forest defoliators, as in its native range. The present study was aimed at (i) identifying the current northern limit of L. dispar's Eurasian range and exploring its northward expansion in Canada using pheromone trap data, and (ii) comparing northern Eurasian populations with those from central and southern regions with respect to male flight phenology, the sums of effective temperatures (SETs) above the 7 °C threshold necessary for development to the adult stage, and heat availability. We show that the range of L. dispar in Eurasia now reaches the 61st parallel, and comparisons with historical data identify the average speed of spread as 50 km/year. We also document the northern progression of L. dispar in southern Canada, where the actual northern boundary of its range remains to be identified. We show that the median date of male flight does not vary greatly between northern and southern regions of the spongy moth range in Eurasia despite climate differences. Synchronization of flight at different latitudes of the range is associated with an acceleration of larval development in northern Eurasian populations. Similar changes in developmental rate along a latitudinal gradient have not been documented for North American populations. Thus, we argue that this feature of spongy moths from northern Eurasia poses a significant invasive threat to North America in terms of enhanced risks for rapid northward range expansion.

Stand dynamics over 15 years including an outlying population of Fagus crenata at the northern margin of its distribution range in Hokkaido, Japan

AbstractFagus crenata, a dominant tree species in cool‐temperate deciduous broad‐leaved forest of Japan, is continuously distributed northward to the Kuromatsunai lowland of Hokkaido, beyond which its distribution is patchy and isolated. We analyzed stand dynamics over 15 years (2006–2021) in a plot (0.75 ha) including one such outlying population of F. crenata. At the stand level over 15 years, stem density decreased, but aboveground biomass increased. The dominance of F. crenata consistently increased in stem density and aboveground biomass. Change in the relationship between stem density and mean stem mass indicated a successional nature of the stand undergoing self‐thinning. Increasing F. crenata dominance and the associated compositional shift was due to the higher growth rates and lower mortality of F. crenata compared to other tree species. Judging from tree‐ring analysis, the oldest F. crenata tree in the plot established in 1821, but the density of F. crenata remained low till ca. 1895. The stand started to be affected by persistent disturbance since ca. 1895, with the waves of tree establishment and growth release both peaking at ca. 1930–1960. The F. crenata population mirrored the pattern of the stand, with more pronounced increases during these waves. We suggest that the long‐lasting episode of tree establishment and growth release over ca. 1930–1960 was caused by human disturbance, most likely selective logging for fuelwood. The results support the “northward expansion” hypothesis, implying that F. crenata potentially can become dominant beyond the current northern limit of continuous distribution and that disturbance facilitates the range expansion.

A comprehensive overview of studies related to the ecology and genetics of Fagus crenata Blume (Siebold's beech, Japanese beech) at the species' northernmost range limit

AbstractTemperate forest species, including Fagus crenata Blume, have been experiencing distributional shifts during the climate oscillation throughout the Holocene epoch. This review describes the distinctive context of F. crenata populations at the northern range from the perspective of past distribution shifts, future expansion predictions, biotic and abiotic interactions in population establishment, forest vegetation characteristics, and genetic diversity during the expansion process. The current northern distribution limit of F. crenata is in southern Hokkaido and Okushiri Islands. Since 1900, a dozen of northern limit hypotheses has advocated the presence of restriction factors; however, the species shows signs of expanding its habitat northward at present. The current northern limit is not determined by physiological limitations because of the fact that artificial plantations of F. crenata grow well beyond its range. Several studies regarding climate scenarios have predicted species persistence in the future. Sociological studies revealed that a decline in vegetation units is observed from the southern to the northern populations on the Oshima Peninsula, Hokkaido. Also, vegetation on Okushiri Island includes remnants of warm temperate flora indicating a physiographic constraint of the F. crenata forest on the island, reflecting a past distributional shift. Most of the current northern marginal populations were revealed to be established at the time of large forest disturbance. The genetic diversity of local populations has been lost during the northward distribution shift due to the founder effect in the colonizing process. Then, the gene flow from rearward populations has dwindled by the completion of the population establishment.

A 1900 Year Sediment Record Suggests Recent Establishment of Black Mangrove (Avicennia Germinans) Stands within a Salt Marsh in St. Augustine, Florida, USA

Salt marshes and mangroves are currently being affected by rising temperatures. Mangroves thrive below −29° N latitude in Florida, USA, and have a low tolerance for extreme cold events, whereas salt marshes dominate further north. One potential effect of climate change is a reduction in the frequency of extreme cold events, which may lead to mangrove expansion into salt marsh systems. Our research identified sediment proxy indicators of salt marsh and mangrove environments. These indicators were applied to soil cores from intertidal wetlands near the current northern limit of mangrove presence on the east coast of Florida, to determine if mangrove expansion into salt marsh environments has precedence in the deeper past. Our findings suggest that mangrove and salt marsh sediments can be distinguished using a combination of stable carbon isotope ratios of sedimentary organic matter and macroscopic plant fragments, and our results showed that a mangrove stand that we cored established only recently. This result is consistent with other work in the southeastern United States that suggests that mangroves established at the current boreal limit only recently after the end of the Little Ice Age, and that the current mangrove expansion may be fueled by anthropogenic climate change.

Body size and competitor identity modulate prey consumption and feeding behaviour in a slow-moving benthic predator (Asterias rubens, Linneaus)

Understanding interactive effects of body size and competition on predator-prey relationships is key to predicting shifts in marine communities, particularly under accelerating pace of introductions of non-native species on a global scale. The common sea star, Asterias rubens (Linneaus), is a dominant indigenous predator in rocky subtidal habitats in eastern Canada, affecting community structure through sustained consumption of bivalve prey, mainly blue mussel, Mytilus edulis (Linneaus). Yet, considerable spatial and dietary overlaps with the indigenous rock crab, Cancer irroratus (Say), and introduced green crab, Carcinus maeneas (Linneaus), together with comparatively lower mobility in A. rubens, suggest the latter is poorly fit to compete with both crabs for M. edulis. A laboratory mesocosm experiment was used to examine competitive interactions for variably-sized M. edulis between small and large, 3-week starved A. rubens, and large C. irroratus or C. maenas (in one-on-one sea star versus crab face-offs) from southeastern Newfoundland. Mussel consumption in starved A. rubens, as well as four components of its natural feeding behaviour, were quantified over 75-h trials in relatively cold (~4 to 5.5 °C) seawater representative of the current northern limit of C. maenas' distribution in the northwestern Atlantic. Results showed that starved A. rubens (1) prioritizes consumption, upon contacting mussel prey, over non-feeding activities such as responding to physical contacts initiated by crabs; (2) alters consumption and feeding behaviour under prolonged exposure to C. irroratus; and (3) increases movement in presence of green crab, more so in large than small sea stars. Overall, findings demonstrate that A. rubens' foraging decisions vary ontogenetically and with competitor's identity. Observed differences in consumption and feeding behaviour in A. rubens exposed to familiar (rock crab) or unfamiliar (green crab) competitors also suggest timing and frequency of encounters with competitors have the potential to alter feeding patterns throughout an organism's lifetime.

White-nose syndrome detected in bats over an extensive area of Russia

BackgroundSpatiotemporal distribution patterns are important infectious disease epidemiological characteristics that improve our understanding of wild animal population health. The skin infection caused by the fungus Pseudogymnoascus destructans emerged as a panzootic disease in bats of the northern hemisphere. However, the infection status of bats over an extensive geographic area of the Russian Federation has remained understudied.ResultsWe examined bats at the geographic limits of bat hibernation in the Palearctic temperate zone and found bats with white-nose syndrome (WNS) on the European slopes of the Ural Mountains through the Western Siberian Plain, Central Siberia and on to the Far East. We identified the diagnostic symptoms of WNS based on histopathology in the Northern Ural region at 11° (about 1200 km) higher latitude than the current northern limit in the Nearctic. While body surface temperature differed between regions, bats at all study sites hibernated in very cold conditions averaging 3.6 °C. Each region also differed in P. destructans fungal load and the number of UV fluorescent skin lesions indicating skin damage intensity. Myotis bombinus, M. gracilis and Murina hilgendorfi were newly confirmed with histopathological symptoms of WNS. Prevalence of UV-documented WNS ranged between 16 and 76% in species of relevant sample size.ConclusionsTo conclude, the bat pathogen P. destructans is widely present in Russian hibernacula but infection remains at low intensity, despite the high exposure rate.

Reproductive Ecology of Recently Established Wild Pigs in Canada

An essential component of management efforts to control invasive species is the estimate of life history parameters, such as reproductive rate and litter size. Wild pigs (Sus scrofa), one of the most invasive terrestrial mammals worldwide, have recently become established on the Canadian prairies. We estimated life history traits in a population of wild pigs in Saskatchewan, Canada, at the current northern limit of their North American distribution. The average pregnant wild pig weighed 73.8 kg (46 – 130 kg; n = 7). Fifty-four percent of females ≥46 kg were pregnant in Feb., with an average of 5.6 fetuses per pregnant female (range 4 – 7; n = 7). Although small sample sizes precluded statistical significance, we found that larger females in better body condition tended to have more fetuses and that the sex ratio of fetuses tended to be female-biased. Based on the cohort that we sampled in Feb., we predicted parturition would occur between Feb. and May; this range of parturition dates may have been wider had we sampled wild pigs at other times of the year. We show that the number of fetuses of wild pigs in Saskatchewan is similar to other areas, suggesting that population growth and spread could be just as rapid. Our estimates represent the first empirical life history measures of wild pigs in Canada and are an essential step in developing science-based eradication plans for this highly invasive species.

Current and potential future distribution of the American dog tick (Dermacentor variabilis, Say) in North America

The American dog tick (Dermacentor variabilis) is medically and economically important in North America. This species is found across central and eastern North America from the Gulf Coast of Mexico through southern Canada. In parts of this region, D. variabilis is a vector for pathogens that cause diseases in humans and animals. Our aim was to determine whether climate change would affect the distribution of the climatically suitable area for D. variabilis in North America, to aid monitoring for potential future spread of tick-borne pathogens. We developed a species distribution model for D. variabilis to project where climate will likely be suitable for the tick in North America using a maximum entropy method, occurrence records from museum and laboratory archives, and 10 environmental variables relevant to climate requirements for the tick. We used four emissions scenarios from the Intergovernmental Panel on Climate Change's Fifth Assessment Report and 10 climate models from the Coupled Model Intercomparison Project (phase 5) to estimate potential future climate suitability and determine how the tick's distribution could change. Our consensus model projected that the area of suitable climate in North America could increase from present by approximately 50% by 2070. In areas beyond the current northern limit of D. variabilis, climate could become more suitable for the tick than at present, possibly resulting in a northward expansion in Canada, but the potential suitability of the southern range of D. variabilis could decrease, depending on the region and climate model. Due to the ability of D. variabilis to harbor and transmit pathogens, a change in the distribution of this species could also affect the risk of human and animal diseases throughout North America, particularly in the northern range of the tick.

Distributional extensions of Carollia castanea and Micronycteris minuta from Guatemala, Central America

Abstract Field expeditions in 2011 that inventoried the terrestrial vertebrate fauna of two wildlife protected areas in the tropical Caribbean of Guatemala have produced the first confirmed records of two bats for the country: the white-bellied big-eared bat, Micronycteris (Schizonycteris) minuta (Gervais 1856) and the Chesnut short-tailed bat Carollia castanea H. Allen, 1890, both of neotropical distribution and with their current northern limit at Lancetilla, Honduras. The record of M. minuta at Sierra de Caral, Guatemala extends the range of this species 137 km to the west, and the record of C. castanea at Cerro San Gil extends its range 147 km to the west.

Modelling the Northward Expansion of Culicoides sonorensis (Diptera: Ceratopogonidae) under Future Climate Scenarios.

Climate change is affecting the distribution of pathogens and their arthropod vectors worldwide, particularly at northern latitudes. The distribution of Culicoides sonorensis (Diptera: Ceratopogonidae) plays a key role in affecting the emergence and spread of significant vector borne diseases such as Bluetongue (BT) and Epizootic Hemorrhagic Disease (EHD) at the border between USA and Canada. We used 50 presence points for C. sonorensis collected in Montana (USA) and south-central Alberta (Canada) between 2002 and 2012, together with monthly climatic and environmental predictors to develop a series of alternative maximum entropy distribution models. The best distribution model under current climatic conditions was selected through the Akaike Information Criterion, and included four predictors: Vapour Pressure Deficit of July, standard deviation of Elevation, Land Cover and mean Precipitation of May. This model was then projected into three climate change scenarios adopted by the IPCC in its 5th assessment report and defined as Representative Concentration Pathways (RCP) 2.6, 4.5 and 8.5. Climate change data for each predictor and each RCP were calculated for two time points pooling decadal data around each one of them: 2030 (2021–2040) and 2050 (2041–2060). Our projections showed that the areas predicted to be at moderate-high probability of C. sonorensis occurrence would increase from the baseline scenario to 2030 and from 2030 to 2050 for each RCP. The projection also indicated that the current northern limit of C. sonorensis distribution is expected to move northwards to above 53°N. This may indicate an increased risk of Culicoides-borne diseases occurrence over the next decades, particularly at the USA-Canada border, as a result of changes which favor C. sonorensis presence when associated to other factors (i.e. host and pathogen factors). Recent observations of EHD outbreaks in northern Montana and southern Alberta supported our projections and considerations. The results of this study can inform the development of cost effective surveillance programs, targeting areas within the predicted limits of C. sonorensis geographical occurrence under current and future climatic conditions.

Range shift and introgression of the rear and leading populations in two ecologically distinct Rubus species.

BackgroundThe margins of a species’ range might be located at the margins of a species’ niche, and in such cases, can be highly vulnerable to climate changes. They, however, may also undergo significant evolutionary changes due to drastic population dynamics in response to climate changes, which may increase the chances of isolation and contact among species. Such species interactions induced by climate changes could then regulate or facilitate further responses to climatic changes. We hypothesized that climate changes lead to species contacts and subsequent genetic exchanges due to differences in population dynamics at the species boundaries. We sampled two closely related Rubus species, one temperate (Rubus palmatus) and the other subtropical (R. grayanus) near their joint species boundaries in southern Japan. Coalescent analysis, based on molecular data and ecological niche modelling during the Last Glacial Maximum (LGM), were used to infer past population dynamics. At the contact zones on Yakushima (Yaku Island), where the two species are parapatrically distributed, we tested hybridization along altitudinal gradients.ResultsCoalescent analysis suggested that the southernmost populations of R. palmatus predated the LGM (~20,000 ya). Conversely, populations at the current northern limit of R. grayanus diverged relatively recently and likely represent young outposts of a northbound range shift. These population dynamics were partly supported by the ensemble forecasting of six different species distribution models. Both past and ongoing hybridizations were detected near and on Yakushima. Backcrosses and advanced-generation hybrids likely generated the clinal hybrid zones along altitudinal gradients on the island where the two species are currently parapatrically distributed.ConclusionsClimate oscillations during the Quaternary Period and the response of a species in range shifts likely led to repeated contacts with the gene pools of ecologically distinct relatives. Such species interactions, induced by climate changes, may bring new genetic material to the marginal populations where species tend to experience more extreme climatic conditions at the margins of the species distribution.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-014-0209-9) contains supplementary material, which is available to authorized users.

Lycaena disparon its northern distribution limit: an expansive generalist

The aim of this study was to evaluate host plant and habitat pref- erences of Lycaena dispar, an oligophagous butterfly species endangered in some parts of its European range. 2. In laboratory trials, the females of Estonian populations accepted various species of Rumex as oviposition substrates. Growth performance of the lar- vae did not differ between the hosts offered (only R. acetosa proved to be unsuitable). 3. In the field, extensive use of the two most common host species - R. cris- pus and R. obtusifolius - by the Estonian populations of L. dispar was con- firmed. Unlike in the laboratory, larval performance in the field was better on R. obtusifolius than R. crispus. A likely explanation is the more ephemeral char- acter of the aboveground parts of R. crispus plants: these tend to wilt before the larvae of L. dispar have reached the stage adapted to hibernation. 4. A countrywide analysis of landscape occupancy revealed a positive associa- tion of the occurrence of L. dispar with ditches and human settlement. We conclude that moderate anthropogenic pressure maintains suitable habitats for L. dispar through creating favourable conditions for R. obtusifolius, the primary host of the butterfly in the region. 5. Due to its generalism in both host and habitat use, L. dispar is not in the need of active conservation measures on the current northern limit of its distribu- tion. The favourable status of the species in Estonia is corroborated by its recent range expansion which parallels similar trends elsewhere in Eastern Europe.

近畿地方におけるミナミアオカメムシの分布拡大：加速する北上

Recently, poleward range expansions in association with recent climate warming have been reported in several species around the world. In Japan, Nezara viridula, a serious pest of various crops, has been expanding its range northward, possibly due to climate warming. Data on the current distribution and accurate prediction of range expansion are important for pest management. Here, we show that the current distribution of N. viridula in the Kinki district has been expanded northward. Moreover, comparison of the current distribution with the data from five and fifty years ago reveals that the speed of range expansion has accelerated. In addition, the current distribution cannot be simply explained by temperature, which was previously believed to determine the northern limit of N. viridula, because the temperature in the current northern limit area does not meet the conditions. This suggests that factors other than temperature are also involved in the northward range expansion of N. viridula. To understand the impact of climate warming on the northward range expansion, it is important to consider not only temperature but also other factors, including physiological and/or behavioral adaptations.

Holocene vegetation and climate on Hokkaido Island, northern Japan

Hokkaido is classified into five regions based on climatic features: the Japan Sea coast, the Pacific coast, the Okhotsk Sea coast, the inland region, and southwest Hokkaido. Holocene vegetation and climate changes at twelve sites selected from these regions are reviewed and compared. On the Japan Sea coast, Picea and Quercus pollen fluctuated at millennial scale, matching with pulses of the Tsushima Current revealed from diatom-based temperature reconstructions in the Japan Sea. A marine core obtained from off the Pacific coast revealed a maritime climate through increasing Betula pollen percentages during the last deglaciation and early Holocene. In summer, dense sea fog resulting from the Oyashio Cold Current and Ogasawara High caused a maritime climate on the Pacific coast. Pollen percentages of Betula ermanii, which is well adapted to the maritime climate in Northeast Asia, increased during this period. Vegetation changes on the Okhotsk Sea coast and in inland regions were similar, indicating similar climatic changes. In these regions, Quercus forests have been distributed steadily since 8000 BP under a warm and moist climate, except for the northern coast, at the Sea of Okhotsk, where Picea and Abies increased slightly since 2000 BP. In southwest Hokkaido, Quercus began to increase 1000 years earlier than in other regions. Fagus crenata migrated from Honshu Island to southernmost Hokkaido around 6000 BP and reached the current northern limit around 1000 BP. The period during which Quercus pollen percentages increased is recognized in almost all regions at around 8000–9000 BP. However, local factors, such as river flooding and local strong winds, also influenced the vegetation changes. Comparison of the vegetation changes in three neighboring regions of Northeast Asia indicate abrupt warming at around 8000–9000 BP and cooling at 2500 BP common to all regions, suggesting global climatic changes.

The biogeographic histories of Pinus edulis and Pinus monophylla over the last 50,000 years

Well-preserved pine needles found in fossil packrat middens document the biogeographic responses of pinyon pines to changing climates over the last 50,000 years. During the full glacial Wisconsinan (MIS2), Pinus monophylla (single-needle pinyon), Pinus edulis (Colorado pinyon), and P. edulis var. fallax (Arizona singleleaf pinyon) all grew along the southern portions of their current ranges. P. monophylla extended from the southern Sierra Nevada across the Mojave Desert to northwestern Arizona. P. edulis grew from northwestern Arizona across central Arizona to New Mexico and south to westernmost Texas. P. edulis var. fallax grew throughout what is now the Sonoran Desert of southern Arizona. Application of the modern climate requirements for these species suggest that winter precipitation at this time was at least 150% of modern, but also that summer precipitation may have been somewhat greater than today, at least at the northernmost end of the Gulf of California. During the Bølling and Allerød intervals P. edulis and P. edulis var. fallax quickly expanded northward over the Mogollon Rim of central Arizona into the Little Colorado River basin and northwestern Arizona. This northerly expansion of the fallax variety during the Allerød interval suggests that temperatures were warmer than most of the latest Wisconsinan and that summer precipitation was at least 120% of modern. After the rapid warming at the start of the Holocene (11.7 ka), P. monophylla and P. edulis populations were reduced in extent as their retreating southerly stands were not immediately replaced by expansion into cooler regions. These populations slowly expanded 300–500 km northward at rates between 20 and 60 m y−1, reaching some of their current northern limits only within the last millennium. Increases in temperature expected over the next several hundred years will result in a similar reduction in populations unless this warming is ameliorated by favorable increases in precipitation. The consistent needle anatomy and distributions of the three types relative to each other suggest that there has been little evolutionary change discernible from these needles over at least the last 25,000 years.

Submerged reefal deposits near a present‐day northern limit of coral reef formation in the northern Ryukyu Island Arc, northwestern Pacific Ocean

AbstractHigh‐resolution single‐channel seismic reflection surveys were carried out in the northern Ryukyu Island Arc during an NT05‐14 cruise of the R/V Natsushima. The survey area is located northeast of Amami Oshima and southwest of Kikai Shima immediately south of the current northern limit of coral reef formation in the northwestern Pacific Ocean. The main purpose of the surveys was to ascertain whether coral reefs formed during glacial periods and, if so, to determine their three‐dimensional distribution. We collected 784 km of high‐resolution single‐channel seismic data during the cruise. The acoustic basement is clearly observed under the Amami Spur, off Amami Oshima. The seismic profiles show two anticlines, each with an axis trending northeast to southwest. Thin Quaternary stratified sediment overlies the acoustic basement in the northwestern and southeastern slope areas, as well as between the anticlinal axes. The stratified sediment can be divided into several sedimentary units. The mound‐shaped reflections are found within the stratified sedimentary units in the central to eastern parts of the spur. Because the mound‐shaped reflections are characterized by strong reflections and chaotic internal structures in profiles, they are considered biogenic ‘reefs’ or banks consisting of coarse‐grained bioclasts. They overlie the acoustic basement or stratified sediment and reach 15 m in thickness and 400 m in width. In contrast, irregularly shaped topographic highs were detected at the shelf edge southwest off Kikai Shima, which are likely to be remnants of coral reefs formed during the last glacial period. Our seismic data indicate probable coral reef formation at low stands during glacial stages, such as the Last Glacial Maximum, even in the northern Central Ryukyus. The occurrence of drowned reefs may indicate that their growth rate was not sufficient to keep up with a rapid rise in sealevel after a glacial period.

Shifting zonal patterns of the southern boreal forest in eastern Canada associated with changing fire regime during the Holocene

This research aims at uncovering the stand-scale Holocene fire history of balsam fir forest stands from two bioclimatic zones of the boreal forest and assessing the existence of a sub-continental shift in past fire activity that could have triggered a change in the Holocene zonal pattern. In eastern Canada, the extant closed-crown boreal forest corresponds to two ecological regions separated along 49°N, the northern black spruce zone and the southern balsam fir zone. We sampled balsam fir stands from the southern fir zone ( n = 7) and among the northernmost patches of fir forest located far beyond the fir zone boundary, into the spruce zone ( n = 6). Macrofossil analysis of charcoal in mineral soils was used to reconstruct both the stand-scale and regional Holocene fire histories. Data were interpreted in the context of published palaeoecological evidence. Stands of the balsam fir zone were submitted to recurrent fire disturbances between c. 9000 and 5000 cal. yr B.P. Local fire histories suggested that four sites within the fir zone escaped fire during the Holocene. Such fire protected sites allowed the continuous maintenance of the balsam fir forest in the southern boreal landscape. Stands of the spruce zone have been affected by recurrent fires from 5000 cal. yr B.P. to present. Local fire histories indicated that no site escaped fire in this zone. Published palaeoecological data suggested that balsam fir migrated to its current northern limit sometime between 7300 and 6200 cal. yr B.P. A change of the fire regime 5000 years ago caused the regional decline of an historical northern balsam fir forest and its replacement by black spruce forest. The consequence was a sub-continental reshuffling of the fir and spruce zones within the closed-crown boreal forest. The macrofossil analysis of charcoal in mineral soils was instrumental to the reconstruction of stand-scale Holocene fire history at sites where no other in situ fire proxies were available.

Dendrochronological evidence for a lower water-table on peatland around 3200-3000 BC from subfossil pine in northern Scotland

Tree-ring analysis of subfossil Pinus sylvestris L., from nine new peatland sites located beyond the species’ current northern limit in Scotland, established a regional chronology called WRATH-9. The chronology has been provisionally dated against Irish pine chronologies and provides the first annual resolution picture of Scots pine expansion from c. 3200 BC and subsequent demise from c. 3000 BC. Pine germination and growth is suggested to be associated with a widespread fall in bog water-tables that indicates a regional climatic control. Bog pines progressively declined in number, rather than died out in a single event, reflecting their growth in a marginal habitat, close to a critical ecological threshold. The use of tree-ring sequences from in situ bog pine macrofossils provides a higher resolution insight into past conditions than possible with existing radiocarbon and pollen-based chronologies.

50,000 years of vegetation and climate history on the Colorado Plateau, Utah and Arizona, USA

Sixty packrat middens were collected in Canyonlands and Grand Canyon National Parks, and these series include sites north of areas that produced previous detailed series from the Colorado Plateau. The exceptionally long time series obtained from each of three sites (> 48,000 14C yr BP to present) include some of the oldest middens yet discovered. Most middens contain a typical late-Wisconsinan glaciation mixture of mesic and xeric taxa, evidence that plant species responded to climate change by range adjustments of elevational distribution based on individual criteria. Differences in elevational range from today for trees and shrubs ranged from no apparent change to as much as 1200 m difference. The oldest middens from Canyonlands NP, however, differ in containing strictly xeric assemblages, including middens incorporating needles of Arizona single-leaf pinyon, far north of its current distribution. Similar-aged middens from the eastern end of Grand Canyon NP contain plants more typical of glacial climates, but also contain fossils of one-seed juniper near its current northern limit in Arizona. Holocene middens reveal the development of modern vegetation assemblages on the Colorado Plateau, recording departures of mesic taxa from low elevation sites, and the arrival of modern dominant components much later.