Birch Zone Research Articles

Subtill nonglacial deposits and their climatic implications for the Last Interglacial (MIS 5e), Hudson Bay Lowlands, Canada

In Hudson Bay Lowlands (HBL), the Wisconsinan tills are often underlain by organic-bearing nonglacial deposits formed during episodes of significant reduction of ice volumes or complete ice-free conditions in this region. The subtill nonglacial deposits, often correlated with the Missinaibi Formation, are beyond the method limit of radiocarbon dating in general. As such, they have been a subject of debates for their stratigraphy and associated climatic conditions owing to poor age constraints. Extensive studies were undertaken on a subtill argillaceous lacustrine deposit uncovered recently on the Winisk River. This 9 m thick organic-rich deposit, referred to as the Webequie Beds, was dated at 121 ± 9 ka, 126 ± 24 ka and 105 ± 11 ka using optically stimulated luminescence (OSL) dating method and correlated with the Last Interglacial (LIG) or Marine Isotope Stage (MIS) 5e. Pollen and plant macrofossils suggest spruce boreal forests along with extensive wetlands, not unlike what exists in the HBL today. Of particular note is the sporadic rise of birch in the upper part of the pollen sequence, interpreted as a response to the availability of frequent forest clearance by fires under a warmer climate. The birch zone is noteworthy because it corresponds to the development of conspicuous S-rich, ferromagnetic nodules (0.125–1.5 mm diameter) in the lake sediment. The nodules comprise native sulphur and greigite (Fe3S4), along with iron oxyhydroxide goethite and lepidocrocite. They likely resulted from significant warming during this interval that enhanced microbial sulphate reduction and increased the release of H2S, an essential component for the formation of the S minerals in the lake. Besides the strengthened microbial metabolization, a prolonged summer lake stratification and development of an anoxic bottom water also likely promoted the sulphate reduction. Although confirmation is needed, the warming probably linked to the LIG thermal maximum (∼120 ka) when a climate with a higher summer temperature than today prevailed. A similar subtill nonglacial deposit on the Little Current, a tributary of the Albany River, was also examined for comparison. Apart from a similar pollen flora, S-rich nodules were also recovered near a horizon OSL dated at 118 ± 13 ka comparable to the LIG thermal maximum. Results of this study provide new insights into the stratigraphy and climatic conditions of the LIG in the HBL but also help better understand the behavior and dynamics of the Laurentide Ice Sheet during the Late Pleistocene.

Plant Communities of Fennoscandian Subarctic Mountain Ecosystems 60 Years After Human Disturbance

ABSTRACTWe studied the vegetation cover of 60-year-old military sites in the subarctic mountain area in northwestern Finnish Lapland, comparing the vegetation of observation posts in the barren mountain and camps in the mountain birch zone to the undisturbed control sites. These kinds of old disturbance areas give us valuable information about resilience and recovery of vegetation in a fragile subarctic environment and allow us to follow up and predict changes under changing climate.Vegetation of the disturbed sites had not recovered to the initial condition in 60 years; the recovery was slower in the mountain birch zone where the intensity of disturbance had been higher. The coverage of dwarf shrubs, especially Empetrum hermafroditum and Vaccinium myrtillus, was lower at the military sites as compared to the controls; instead, increased coverage of some graminoids was observed in the observation posts and the transition zones of camps. At the most disturbed patches, cryptogams were still prevailing. The results confirm the observations of earlier studies that rather than ecological recovery, the long-term development of vegetation in disturbance areas in high latitudes shows a shift to functionally different plant communities.

Postglacial vegetation history as recorded from the subalpine Lake Ribno (NW Rila Mts), Bulgaria

AbstractA pollen analysis conducted on a 600 cm core from Lake Ribno (2184 m) in the Northwestern Rila Mountains, supplemented by 13 radiocarbon dates, has revealed the basic stages in its postglacial vegetation dynamics. The lateglacial vegetation, composed of Artemisia, Chenopodiaceae and Poaceae, with stands of Pinus and Juniperus-Ephedra shrubland, dominated in the stadials and partly retreated during the Bølling/Allerød interstadial (14700–12900 cal. yrs. BP). The afforestation in the early Holocene (11600–7800 cal. yrs. BP) started with pioneer Betula forests, with groups of Pinus and Juniperus at mid-high altitudes, and Quercus forests with Tilia, Ulmus, Fraxinus, Corylus below the birch zone. A coniferous belt composed of Pinus sylvestris, P. peuce and Abies was shaped under the conditions of a more humid climate (7800–5800 cal. yrs. BP). The last trees that invaded the study area were Fagus after 4300 cal. yrs. BP and Picea abies after 3400 cal. yrs. BP. Evidence for destructive changes in the vegetation and indications of agricultural and stock-breeding activities (pollen of Triticum, Secale, Plantago lanceolata, Rumex, Juglans) was continuously recorded since the Late Bronze Age (3400–3200 cal. yrs. BP). The postglacial vegetation history in the Northwestern Rila Mountains demonstrated close similarities with that of the Northern Pirin Mountains.

Response of Scots Pine (<i>Pinus sylvestris</i>) to Warming Climate at Its Altitudinal Limit in Northernmost Subarctic Finland

The present study aims to contribute to a fine regional differentiation of Scots pine (Pinus sylvestris) response to climate change at its altitudinal margins in subarctic Finland north of 69˚ N (Utsjoki) and to find out whether a prompt establishment of new pines in response to climate change can be expected above the old pine tree limit in and above the mountain birch zone. In 10 sampling areas, distribution, site characteristics, and condition (damage degree, growth forms) of the new pines (pines that have become established since the mid 20th century) were checked in a zone 50 m to the left and right of our field routes. The field routes extended from the scattered birch forest to the treeless alpine zone and mountaintops and covered a total area of more than 4 km2. In total, 213 new pines were found. Tree height was measured and age estimated by counting the whorls. The degree of damage was estimated and then attributed to four damage classes. Pine establishment was most successful during the 1970s and up until the end of the last century. Pines younger than 10 years are rare (< 3%) in the study areas, with one exception (about 8%). Pine recruitment is comparatively intense in close proximity to old pines in the birch forest while it is sporadic within the scattered birch stands at higher elevations and in the alpine tundra. More than 80% of the new pines show disturbed growth forms due to frequent winter injury, reindeer, and moose. About 66% exhibit severe damage, and 15% have already died. On windswept terrain, microsite facilitation is essential for pine establishment. Lack of local seed sources and severe site conditions at high elevations have probably delayed pine altitudinal advance. New pine generations may become effective seed sources speeding up pine advance beyond the present seed trees. In view of the high proportions of severely damaged and dead new pines, we do not expect that climatic warming will bring about a rapid advance of the pine tree limit.

First data on the expansion of Larix gmelinii (Rupr.) Rupr. into arctic regions of Beringia during the early Holocene

The international program on paleoclimates of El’gygytgyn Lake contemplates the study of different genetic types of sediments established in its basin. The lake, which provided one of the longest continuous climatic records of the Arctic Region, was formed about 4 Ma ago when a meteorite fell in the northern Chukchi Peninsula in the region of 67 ° 30 � N, 172 ° 05 � E [1]. The region belongs to a mountainous variant of a typical tundra subzone [2]. Slopes of the Anadyr Tableland surrounding the lake are occupied by the undershrub‐ lichen tundra. Dwarf birch and willow are encountered on protected areas in valleys of the Enmyvaam River flowing out of the lake and its tributaries (the Anadyr River system). Present-day climatic parameters for El’gygytgyn Lake are as follows: the average temperature is +8.3 ° C for July and ‐28.4 ° C for January; average precipitation is 47.4 mm in July and 21.5 mm in January. A series of radiocarbon ages (figure) accompanies the palynological and paleocarpological analyses of loose deposits exposed in the scarp of the 4-m terrace of the Ol’ga Creek running into the Enmyvaam River on the left at a distance of 1 km from the lake (67 ° 26 � 45 � N, 172 ° 13 � 14 � E). The first age (9125 ± 30 years ago, MAG-994) in this series was established for a large trunk of alder ( Duschekia fruticosa ) found in peat at the depth of 163 cm (figure). This age and two other ages for fragments of shrub branches: 9250 ± 90 years ago (MAG-1477), at the depth of 172 cm, and 8120 ± 25 years ago (MAG-1478), at the depth of 150 cm, allow for correlating the peat formation time with the Boreal interval of the Holocene. The age 7770 ± 50 years ago (MAG-1480) established for plant remains from the depth of 109 cm indicates that peat with sand lenses (figure, Bed 5) formed during the period corresponding to the Atlantic interval of the Holocene. The spore-and-pollen diagram of deposits on the terrace comprises three pollen zones (figure). Subdivision of zones is determined by variations in the content of main pollen taxons and each spore taxon calculated in percent out of the total pollen. It is significant that in contrast to spectra of sediments from El’gygytgyn Lake represented by pollen brought by wind from the Anadyr Tableland [1], peat spectra reflect local plant communities. Pollen zone 1 is distinguished as a zone of birch (figure). It is similar to birch pollen zones in climatic records of Beringia lakes and reflects a response of the vegetation cover to climate warming in the period transitional from the Pleistocene to the Holocene [3]. Spore-and-pollen spectra of the zone underline a wide distribution of such shrubby birch species as Betula middendorffii, B. exilis, and B. fruticosa that replaced herb communities of the Last Glaciation [3].

A contribution to the postglacial vegetation history of the Rila Mountains, Bulgaria: The pollen record of Lake Trilistnika

Pollen analysis of sediments from the glacial Lake Trilistnika (2216 m) in the Northwestern Rila Mountains (Bulgaria), supplemented by 13 radiocarbon dates, allowed the reconstruction of the palaeoenvironment and vegetation history in postglacial time. The exact time of the cirque glacier retreat is still under discussion but the lake was free of ice before 15,000 cal. BP, when sedimentation of gray silt began. The lateglacial vegetation, composed of Artemisia, Chenopodiaceae and Poaceae, with isolated stands of Pinus and Juniperus– Ephedra shrubland, dominated during the stadials and partly retreated during the Bølling/Allerød interstadial complex. The afforestation in the early Holocene (11,500–7800 cal. BP) started with the distribution of pioneer Betula forests with groups of Pinus ( P. mugo, P. sylvestris and P. peuce) at mid-high altitudes, and Quercus forests with Tilia, Ulmus, Fraxinus, Corylus below the birch zone. The change to more humid and cooler climate ca. 7800–7500 cal. BP favored the vertical migration of Abies, P. sylvestris and P. peuce. The establishment of Fagus sylvatica took place after 5200 cal. BP, when pure or mixed beech communities were formed. The last tree which invaded the coniferous belt between 4300 and 3400 cal. BP was Picea abies. The first expansion maximum of spruce was recorded after ca. 2700 cal. BP. The vegetation development in historical times was also influenced by human interference, indicated by the continuous presence of pollen anthropogenic indicators such as Triticum, Secale, Hordeum, Plantago lanceolata, Rumex, Scleranthus, Juniperus.

Breeding performance of the Fieldfare Turdus pilaris in the subalpine birch zone in southern Lapland: a 20 year study

A Fieldfare population, on average c. 160 pairs, was studied in subalpine birch forest in southern Lapland (c. 66°N; 500–600 m.a.s.l.) in 1983–2002. Onset of egg-laying showed no temporal trend, consistent with absence of spring temperature trend. Eggs were laid with an interval of c. 21 hours and 45 minutes, not 24 hours as normal in passerines. This reduces the exposure time to depredation during egg-laying with 9%. Egg hatchability was 96%. Egg parasitism never occurred. Depredation of nests was 46%, but very variable. Replacement and second clutches did not occur. Although an average of 4.45 young fledged from successful nests (≥1 fledgling), only 2.11 fledglings were produced per pair and year. The population varied without trend over the study period. Adult survival, estimated by the proportion of adults at the start of breeding, was 58%. This infers that first year survival must be at least c. 40%. Since this is a likely value, it seems that the Fieldfare population of the subalpine birch forest is selfsustained and not dependent upon immigration.

Four new pollen sections tracing the Holocene vegetational development of the southern part of the West Siberan Lowland

In the southeast of Western Siberia within the zone of birch and pine forests in the Ob'-Tom' interfluve area, four new pollen diagrams from sites in different landforms (interfluve, terraces, floodplain, and ancient drainageways) with sandy and clay soils were correlated with two published pollen diagrams. Two main types of pollen stratigraphy are characteristic for areas with clay and sandy soils, reflecting different vegetational developments during the Holocene that were controlled by changes in climate and soil properties. Open birch forest-steppe with Artemisia and Chenopodiaceae was widespread in the Ob'-Tom' interfluve during the early Holocene, whereas the young floodplains had flooded meadows and willow scrub. The principal vegetation change from open steppe and forest-steppe to dense forest took place about 7000 yr BP, after which forest vegetation has prevailed. On sandy soils the dominant tree species was Pinus sylvestris throughout, but on clay Pinus sibirica and Abies sibirica together with Betula pendula had more important roles, alternating periodically with Pinus sylvestris. Expansion of Pinus sibirica and Abies sibirica in this area started about 4500-4000 yr BP, but in some places they declined markedly during recent centuries due to human influence. Based on the vegetational development, the climate in the southeast of Western Siberia changed from colddry to warm-dry (9500 yr BP) then to warm-wet (7000 yr BP), and finally to cool-wet (4000 yr BP).

The influence of hybridization on epidermal properties of birch species and the consequences for palaeoclimatic interpretations

The Fennoscandian birch population primarily consists of Betula nana, B. pendula and B. pubescens ssp. czerepanovii, the Mountain birch. Frequent hybridization between the Mountain birch and B. nana generates a wide range of genotypic and phenotypic plasticity in the subarctic birch zone of Fennoscandia. Phases of subarctic conditions prevailed during the Late Glacial in large parts of NW Europe, and palynological as well as macrofossil analysis provide some evidence for the occurrence of birch hybrids during these intervals. Leaves from genetically controlled specimens of Betula pendula, B. pubescensssp. czerepanovii, B. nanaand the hybrids B. pubescensssp. czerepanovii nana and B. nana pubescens ssp. czerepanovii are investigated for their specific characteristics of the epidermis morphology. Frequency and size of epidermal cells and stomata reveal a close affinity of both hybrids to B. nana and allow a differentiation of the intermediate forms between B. nana and the Mountain birch. With respect to palaeoatmospheric CO2 reconstructions based on stomatal index, epidermal analysis shows that a possible occurrence of hybrids in fossil leaf assemblages has no profound consequences for combined species records. However, the significant differences observed in B. nana demand the separation of this species. A comparison of the cuticle properties of B. pendula and B. pubescensfrom Finnish Lapland and leaf material from The Netherlands reveals a divergence of the stomatal index that may be due to differences in day light length.

Late Quaternary Pollen Records from Oil Lake and Feniak Lake, Alaska, U.S.A.

The pollen analysis of two sediment cores from Oil Lake, in the eastern foothills of the Brooks Range, and Feniak Lake, in the Noatak River drainage, reveal late Wisconsin and Holocene vegetation changes. These cores exhibit alternative trends in the development of the modern tundra biome. At Oil Lake, a long birch/herb zone with little fluctuation is followed by a rapid rise in sedge, which is then followed by a birch zone and an alder zone. There is a drop in birch pollen at the late glacial/Holocene boundary, with a rise in sedge and Nymphaea, an indication of the increase in moisture at the end of the late glacial. Feniak Lake yields a detailed history of Holocene vegetation change that includes an early Alnus pollen rise during the Birch Zone, indicating local expansion of alder in the Noatak River region.

Postglasiale skoggrenser i sentrale sørnorske fjelltrakter.14C-datering av subfossile furu- og bjørkerester. (Postglacial forest limits in central south Norwegian mountains. Radiocarbon datings of subfossil pine and birch specimens)

Aas, B. & Faarlund, T. 1988. Postglasiale skoggrenser i sentrale sørnorske fjelltrakter. 14C-datering av subforssile furu- og bjørkerester. (Postglacial forest limits in central south Norwegian mountains. Radiocarbon datings of subfossil pine- and birch specimens.) Norsk geogr. Tidsskr. Vol. 42, 25–61. Oslo. ISSN 0029-1951. Subfossil specimens of Scots pine (Pinus sylvestris L.) and mountain birch (Betula pubescens Ehrh. subsp. tortuosa (Ledeb.)) have been collected in central south Norwegian mountains at levels from 900 to 1370 m a.s.l. Radiocarbon datings provide evidence of a pine forest limit having exceeded 1200 m a.s.l. in the first half of the Boreal period, a culmination at about 1300 m during the first part of the Atlantic and a high, if somewhat declining, level until the last part of the Subboreal period (i.e. about 3000 years before present (BP)). Between the pine forest and the alpine tundra a subalpine birch zone has prevailed throughout Postglacial time, possibly approaching 1400–1450 m a.s.l. The area of alpine tundra has been smaller than now. Reindeer, living in the open mountain forest provided prey for Stone Age hunters. Most Stone Age sites known from present day alpine surroundings may originally have been located in, or near, the mountain forest, a possibility which may also be due to many seters (summer farms) at high altitudes.

Research Activities on the Forest Line in Northern Finland

Forest line research is one of the main areas of study open to the northern research stations, especially numerous in Fennoscandia. High latitude environmental conditions make considerable demands on the adaptability of plants growing in the subarctic. Besides low temperatures, low light intensity and low energy yield are a challenge to autotrophs: the light rhythm is quite different from that farther south. Detailed mapping of the forest line is now undertaken every 10 years in northern Finland to study the climatic changes causing shifts in the limit. All 12 monitoring areas are situated north of the Arctic Circle. Similar monitoring may be started in other Fennoscandian countries in the near future and might prove useful for studying the effect of the general pollution of the forests. One of Finland's many northern research stations is at Kevo and belongs to the University of Turku. It is the site of the Circumpolar Forest Line Arboretum, where material is collected from all the circumpolar areas. There are three gardens altogether: one close to the station, and the others at a distance of some 10 km. They are managed jointly by the Kevo Station, the National Board of Forestry and the Forest Research Institute. Cooperation in northern research has a long history in Fennoscandia; for example, the project started during the IBP period for studying the northern birch zone continued the work begun by Wahlenberg at the start of the 19th century. The project deals mainly with the variation of the birch and other components of this northern ecosystem. Attention is also paid to the stimulating question of the co-evolution of the different organisms.Key words: arboretum, circumpolar, monitoring, mountain birch, treeline, tree provenances

Programmes of the Kevo Station

Symposium of Subarctic ecology in 1966. The main features of the Fennoscandian Sector of the circumpolar Subarctic were already presented by Wahlenberg (1812) in his zonation of the area as birch zone (regio betulina), pine zone (regio subsilvatica) and coniferous zone (regio silvatica). The zonation received a great deal of attention during the time between Hult (1899) and Ahti et al. (1968). The special forest line problems in Finland have been discussed especially by Renvall, Heikinheimo, Hustich and Mikola (see References in Mikola 1970). The fundamental special features of the area are reflected in the central research programme of the Station presented in Kevo Notes No. 3 (1976). The basic attitude to research has been mainly in accordance with the recommendations (point 2) of the Circumpolar Conference on the Northern Ecology, held in Ottawa in 1975 where much more emphasis and effort be placed upon basic research than the 'management' or 'applied' studies, and that basic research include studies on the function of ecosystems, the physiological ecology of individual species, and greater development of systematic biology. This would give possibilities for a closer cooperation and communication between science and ... the native northern peoples than exist at present (point 4 in the same recommendations). Although these recommendations refer directly to Canada, they also have a circumpolar validity. In addition to the marginal birch and pine forest ecosystem studies, activated particularly during the IBP/Tundra Biome period, the programme includes the following main groups of research plans. (1) The main mapping of the area. Much geological, geomorphologi-

Past and Present Distribution of Marten in New York

A century ago the marten, Martes americana americana , was rather widely distributed in suitable habitats of New York State. These habitats included the “green timber” of white and red spruce and balsam fir, found principally in the Adirondack and Catskill mountains. Occasionally martens move into the rock maple, hemlock and yellow birch zone, but they appear to favor the deep cold swamps and steep mountain slopes above 2000 feet. DeKay (Zoology of New York: Part 1. Mammalia, 1842) indicated that the marten occurs in the elevated and wooded districts of the northern parts of the state. Coues (Fur-bearing animals: a monograph of North American Mustelidae. Misc. Publ. U.S. Geol. Survey, 1877) recorded four specimens from Essex County but did not remark on their abundance. Merriam (The mammals of the Adirondacks, 1884) regarded the animal as common in the dark evergreen forests of the Adirondacks, stating that hundreds were trapped every winter for their fur. Correspondents and older trappers of the Adirondack counties have told me that the marten was common in the early 1900′s. Mearns (Notes on the mammals of the Catskill Mountains, etc. Proc. U.S. Nat. Mus., Vol. 21, No. 1147, 1898) does not list the species from the Catskills, although he was informed that the marten still existed in these mountains. Miller (Preliminary list of …