Richard J. Hebda

Coastal rainforest connections disclosed through a Late Quaternary vegetation, climate, and fire history investigation from the Mountain Hemlock Zone on southern Vancouver Island, British Colombia, Canada

Abstract The post-glacial vegetation and fire history of high-elevation regions on southern Vancouver Island is described using palynological and charcoal records from Porphyry and Walker lakes. A zone consisting mainly of Artemisia , Poaceae, and ferns occurs in the basal clay at Porphyry Lake and may represent a non-arboreal ecosystem in a late-Wisconsin glacial refugium. At both sites, a fire-free Pinus contorta zone occurs before ca 14u2008160 calendar years before present (cal BP). Climate at this time is interpreted as being cool to cold and dry. Mixed conifer forests of Picea , Abies , Tsuga mertensiana and Pinus contorta replaced the Pinus contorta woodlands after ca 14u2008160 cal BP. Fires are recorded for the first time. Climate is interpreted as cool and moist. Forests of Abies , Picea , Tsuga heterophylla , Pseudotsuga menziesii , and Alnus developed and expanded during the early-Holocene from ca 11u2008400–9910 to 7700–7300 cal BP as climate warmed and dried. Charcoal increased during this interval, indicating only slightly more fire activity and reflecting continued moist conditions at high elevations. In the mid-Holocene from ca 7700–7300 to 5200–4900 cal BP, Tsuga heterophylla pollen values increased as forests became dominated by Tsuga heterophylla , Picea , and Abies with Alnus in response to increased moisture. The increase in charcoal influx at this time may reflect an increase in slope wash and erosion resulting from a wetter climate rather than an increase in fire incidence. Starting at ca 5200–4900 cal BP, a further increase in Tsuga heterophylla combined with an increase in Tsuga mertensiana and Cupressaceae pollen suggest that the late-Holocene was characterised by increasing moisture and decreasing temperatures. Late-Holocene forests consisted predominately of Tsuga heterophylla , Tsuga mertensiana , Cupressaceae, and Pinus contorta . A slight reduction in charcoal influx at ca 4600 cal BP implies fewer fires. A recent increase in charcoal at Walker Lake at 1700 cal BP may reflect anthropogenic burning. The timing of events and response of taxa on southern Vancouver Island are comparable to other coastal sites in northwestern North America, suggesting that past ecosystems were widespread and contemporaneous. Palaeoecosystem changes detected in one region of the Pacific Northwest likely reflect a widepsread response to climate throughout the ∼2500 km long zone, a zone that today is home to half of the world’s remaining coastal temperate rainforest.

Studies on pollen morphology of Rosaceae in Canada

Hebda, R.J. and Chinappa, C.C., 1990. Studies on pollen morphology of Rosaceae in Canada. Rev. Palaeobot. Palynol., 64: 103-108. Pollen grains of all genera of Rosaceae surveyed in Canada occur as radially symmetric isopolar monads. Many are tricolporate (rarely tricolpate), except some Sanguisorba species which are bexacolporate. Ectoapertures are slits, mostly constricted at the equator by arching sexinal pore flaps or, less often, an equatorial bridge. Alchemilla, Dalibarda, Dryas, Oemleria, Sorbaria and some Rubus species have reduced or no pore flaps. Fusiform colpus opercula occur in Chamaerhodos, Fragaria, Potentilla, Rosa, Sanguisorba and Sibbaldia. Endoapertures consist of oval to x or dumbell-shaped lalongate openings in the nexine. Weakly to well-developed pore chambers occur in most genera. Sculpturing of parallel ridges and valleys containing perforations predominates. Perforations are of two types, suggesting distinct evolutionary lines. They are (1) large and often extending onto tectal ridges (Amelanchier, Crataegus, Dalibarda, Dryas, Gillenia, Holodiscus, Luetkea, Physocarpus, Prunus, Pyrus, Rosa, Rubus, Sorbus, Spiraea); (2) minute pinholes (Aruncus, Fragaria, Geum, Potentilla, Sibbaldia). Other ridgeand-valley patterns include those perpendicular to the colpus (Agrimonia), intersecting (Chamaerhodos) and mixed (Oemleria, Sorbaria). Pollen with smooth (Cotoneaster, Rubus), verrucate (Rubus, Sanguisorba) and irregular (Purshia) sculpturing with pores and smooth (Alchemilla) and verrucate (Filipendula) sculpturing without pores also occur.

Abrupt climate change and variability in the past four millennia of the southern Vancouver Island, Canada

[1]xa0The identification of past climatic extremes and norms is important for a better understanding of the climate systems and the way they change. Here we present an almost continuous tree-ring and climate record from Vancouver Island, Canada for the last four millennia from Douglas-fir trees (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) that are sensitive to precipitation variation. Spring droughts more severe than that of the mid-1920s occurred in the late 1840s, mid-1460s AD, and ∼ mid-1860s BC. A remarkable climatic anomaly occurred in ∼ the 19th century BC during which strong pentadecadal oscillation prevailed and radial growth decreased by 71% in four years. This event could have been the final stage in the process of climatic and environmental transition beginning 2–3 centuries earlier that led to major cultural transformation in regions sensitive to climate change.

Postglacial paleoecology and inferred paleoclimate in the Engelmann spruce–subalpine fir forest of south-central British Columbia, Canada

Abstract Pollen, charcoal, and plant macrofossil analyses reveal five postglacial vegetation periods at Crater Lake, Crater Mountain, British Columbia. The first period, beginning ca. 11u2008400 14C yr BP was characterized by Artemisia steppe-tundra. At 9700 14C yr BP, Pinus parkland developed, and by 6700 14C yr BP was replaced by fire-successional Pinus-dominated Engelmann spruce and subalpine fir forest (ESSF). At 3800 14C yr BP, Picea became a more important element of the forest, and modern forest structure and composition developed by 1600 14C yr BP. Comparison of the fossil vegetation and fossil midge data derived from several ESSF sites in the southern interior reveals (1) similar late-Pleistocene vegetation and climate at all sites, (2) three distinct Holocene climatic stages: warm/dry, warm/moist, and cool/moist, (3) confirmation of the warm/moist period as a distinct climatic period, and (4) distinct differences in Holocene vegetation change among the sites. The driest and warmest site was most sensitive to climatic change, whereas cooler, moister sites were less sensitive. The present east–west climate gradient originated with postglacial warming at the beginning of the Holocene. Vegetation response to climate change and natural disturbance in these sites is strongly controlled by local site characteristics. These characteristics may have implications for forest, environment, and resource management.

The impact of Pleistocene climate change on an ancient arctic–alpine plant: multiple lineages of disparate history in Oxyria digyna

The ranges of arctic–alpine species have shifted extensively with Pleistocene climate changes and glaciations. Using sequence data from the trnH-psbA and trnT-trnL chloroplast DNA spacer regions, we investigated the phylogeography of the widespread, ancient (>3 million years) arctic–alpine plant Oxyria digyna (Polygonaceae). We identified 45 haplotypes and six highly divergent major lineages; estimated ages of these lineages (time to most recent common ancestor, TMRCA) ranged from ∼0.5 to 2.5 million years. One lineage is widespread in the arctic, a second is restricted to the southern Rocky Mountains of the western United States, and a third was found only in the Himalayan and Altai regions of Asia. Three other lineages are widespread in western North America, where they overlap extensively. The high genetic diversity and the presence of divergent major cpDNA lineages within Oxyria digyna reflect its age and suggest that it was widespread during much of its history. The distributions of individual lineages indicate repeated spread of Oxyria digyna through North America over multiple glacial cycles. During the Last Glacial Maximum it persisted in multiple refugia in western North America, including Beringia, south of the continental ice, and within the northern limits of the Cordilleran ice sheet. Our data contribute to a growing body of evidence that arctic–alpine species have migrated from different source regions over multiple glacial cycles and that cryptic refugia contributed to persistence through the Last Glacial Maximum.

Abies lasiocarpa (Hook.) Nutt. in the late-glacial and early-Holocene vegetation of British Columbia, Canada, and adjacent regions in Washington, USA

Abstract Abies lasiocarpa is a major element of high elevation forests and parkland of British Columbia, Canada, and adjacent regions, yet its history, especially in the late-glacial, is poorly understood. We present four new pollen and macrofossil records, summarize modern surface spectra and review previous studies to understand the role of A. lasiocarpa during the marked climatic changes of the late-glacial and early-Holocene. Today, in southern British Columbia, A. lasiocarpa reaches between 5 and 20% cover in the vegetation at Crater Lake, Buckbean Bog, and Lake of the Woods, but the 1–5% Abies pollen values under-represent its occurrence in the vegetation. At Sicamous Creek Lake, A. lasiocarpa grows at 50% cover and Pinus is absent locally, but the modern pollen surface spectra under-represent sub-alpine fir at 10% of the pollen rain. Based on these observations, sediments from Sicamous Creek Lake, Crater Lake, Buckbean Bog, and Lake of the Woods reveal that Abies grew locally in the late-glacial period. On southern Vancouver Island, British Columbia, the occurrence of an A. lasiocarpa needle, dated to 11u2008900±400 14 C yr BP in a lake core, along with only 1–2% Abies pollen, suggests that the tree grew at low elevations where it does not today. These results and a review of regional paleobotanical records suggest that the role of A. lasiocarpa in late-glacial and early-Holocene vegetation communities has been under-estimated. This species was likely a major element of the vegetation during this interval and among the first tree species to colonize deglaciated surfaces. Considering the magnitude of future climate change, a better understanding of the history of A. lasiocarpa during previous climate changes is necessary to project vegetation response and design effective resource management plans.

Vicariance, long‐distance dispersal, and regional extinction–recolonization dynamics explain the disjunct circumpolar distribution of the arctic‐alpine plant Silene acaulis

PREMISE OF THE STUDYnMany arctic-alpine species have vast geographic ranges, but these may encompass substantial gaps whose origins are poorly understood. Here we address the phylogeographic history of Silene acaulis, a perennial cushion plant with a circumpolar distribution except for a large gap in Siberia.nnnMETHODSnWe assessed genetic variation in a range-wide sample of 103 populations using plastid DNA (pDNA) sequences and AFLPs (amplified fragment length polymorphisms). We constructed a haplotype network and performed Bayesian phylogenetic analyses based on plastid sequences. We visualized AFLP patterns using principal coordinate analysis, identified genetic groups using the program structure, and estimated genetic diversity and rarity indices by geographic region.nnnKEY RESULTSnThe history of the main pDNA lineages was estimated to span several glaciations. AFLP data revealed a distinct division between Beringia/North America and Europe/East Greenland. These two regions shared only one of 17 pDNA haplotypes. Populations on opposite sides of the Siberian range gap (Ural Mountains and Chukotka) were genetically distinct and appear to have resulted from postglacial leading-edge colonizations. We inferred two refugia in North America (Beringia and the southern Rocky Mountains) and two in Europe (central-southern Europe and northern Europe/East Greenland). Patterns in the East Atlantic region suggested transoceanic long-distance dispersal events.nnnCONCLUSIONSnSilene acaulis has a highly dynamic history characterized by vicariance, regional extinction, and recolonization, with persistence in at least four refugia. Long-distance dispersal explains patterns across the Atlantic Ocean, but we found no evidence of dispersal across the Siberian range gap.

AMS-dated late Pleistocene taiga vole (Rodentia: Microtus xanthognathus) from northeast British Columbia, Canada: a cautionary lesson in chronology 1

Dissected colluvial sediments on a Peace River terrace at Bear Flat, northeast British Columbia enclosed a late Pleistocene micromammalian faunule. The fossil remains, including a few loosely articulated skulls and mandibles, were dominated by taiga voles (Microtus xanthognathus). The Bear Flat site constitutes the second fossil occurrence in the region of this elusive species, which is unknown in British Columbia in historic times. The late Pleistocene age, determined by accelerator mass spectrometry directly on taiga vole bone collagen, is consistent with the ages of widespread taiga vole records peripheral to the Laurentide ice sheet in western, mid-western, and eastern North America. The presence of allo-chronous remains within a comprehensively dated sedimentary sequence provides a cautionary note about straightforward acceptance of relative stratigraphic dating.

Palynology of Holocene top-set aggradational sediments of the Fraser River Delta, British Columbia

Abstract Palynological study of radiocarbon-aged top-set Holocene sediments of the Fraser Delta, British Columbia, reveals a record of tidal marsh, river marsh and river swamp environments which indicate former sea-level positions and rates of sea-level change. Interbedded silts and fine sands, containing Pinus and Cyperaceae pollen and monolete fern spores, occur between 15.1 and 14.2 m depth and are interpreted as freshwater-dominated delta-front marsh deposits. Organic-rich silts, containing grass and skunk cabbage pollen and horsetail spores, between 14.2–7.8 m depth, represent an emergent delta-top marsh environment, regularly flooded by the Fraser River. Arboreal pollen types pine, spruce and alder dominate organic-rich silts between 7.8 and 5.8 m, but Rosaceae pollen rises to dominance in peatier sediments between 4.7–5.8 m. These two zones record natural vegetation succession from marsh to swamp, due to increased relative elevation of the site. An increase in arboreal pollen in organic-rich silts between 4.7 and 2.3 m, signals a drop in relative elevation and return to regular flooding. Declines in percentages of arboreal pollen and increases in Rosaceae and skunk cabbage pollen, indicate preliminary stages of bog development and disappearance of fluvial influence above 2.3 m. Organic-rich silts formed mainly in a fluvially-dominated marsh setting, as top-set aggradation kept pace with sea-level rise between approximately 7960 and 4410 yr B.P. An apparent slowing or cessation in sea-level rise allowed peaty sediments to form around 6000 yr B.P. The rate of sea-level rise again declined at 4410 yr B.P., causing organic-rich silts to be replaced by peat deposition. The study provides insights into the history of sea-level change and aggradation in the Fraser River Delta.

Bog surface oscillation (mire breathing): A useful measure in raised bog restoration

Office of Climate Action and Environment, City of Delta, 4500 Clarence Taylor Crescent, Delta, BC V4K 3E2, Canada School of Environmental Studies and School of Earth and Ocean Sciences, University of Victoria, Victoria, BC V8W 2Y2, Canada Correspondence Sarah A. Howie, Office of Climate Action and Environment, City of Delta, 4500 Clarence Taylor Crescent, Delta, BC V4K 3E2, Canada. Email: showie@delta.ca