Open Spruce Woodland Research Articles

Genetic features of soils in altitudinal natural zones of the Khibiny Mountains

The plant cover of the Khibiny Mountains is characterized by the well-pronounced altitudinal zonality: high-alpine barrens—lichen, dwarf shrub, and shrub tundra—elfin birch forest—spruce forest. Humic petrozems (Lithic Leptosols) under sparse vegetation are formed on the tops of the mountains. The soils of the tundra zone are represented by podburs on the eluvium of nepheline syenite; smaller areas are occupied by typical cryozems. Humus-illuvial podzols are developed from moraine deposits under elfin birch forests and open spruce woodland. The moraine deposits in the inner valleys of the Khibiny Mountains are enriched in the products of weathering of nepheline syenite. The humus-illuvial podzols developed from them differ from their analogues on plain territories in the higher humus content and less contrasting eluvialilluvial differentiation.

New York City Mastodons: Big Apple Tusks

Unlike some cities, New York is not known as a locality for fossils, and for good reason, they are few and far between, especially if you exclude the treasure trove of fossils embedded in the dimension stone of facades, lobbies, and rest rooms. It is easy to understand why New York City offers such a paucity of naturally occuring specimens when you consider that most of the city’s bedrock is composed of high-grade metamorphics—gneiss, marble, and schist—1.1 billion to 435 million years old (Baskerville 1994). Any fossils that may have existed in the original parent rock have been destroyed by ensuing high-grade metamorphism, a process by which rocks are altered by heat and/or pressure. The only exposed sedimentary rocks are Cretaceous-age clays and sands. In the past, they have yielded plant fragments including lignite and a few invertebrates (Hollick 1908) and some microfossils, but these exposures are substantially diminished with continuing urbanization. However, almost the entire city has been glaciated, and in places the veneer of glacially transported rocks yield a variety of Paleozoic invertebrate fossils delivered from north and west of the city (Hollick 1893). But it also turns out that late glacial and/or early post glacial sediments contain relatively rare fragments of mastodon skeletons—the ice-age elephant (Mammut americanum)—and finding them is a hit-or-miss undertaking. I have chosen the mastodon for this discussion, focusing on New York City as an unusual locality, because mastodon fossils are well distributed throughout North America, its fossils have been collected by the thousands (Haynes 1991), and mastodons were the rage long before dinosaurs were discovered. The fact that these animals roamed what is now Broadway is an excellent example for starting a discussion on climatic change as well as the hot topic of what caused the demise of the charismatic late Pleistocene megafauna and, as we will see, introducing some aspects of the history of paleontology. Another purpose of this paper is to show that the study of paleontology and evolution can and should be interdisciplinary and multidisciplinary. Often, it is the secondary aspects of these subjects that can excite students and gain their interest. Based on the plant material associated with mastodon fossils in northeastern United States, the mastodons clearly lived in spruce forests and open spruce woodlands containing swamps and bogs. Although the stratigraphic record is not very good for New York City localities, it can be assumed that they lived in a similar vegetation zone, an environment so different than the eastern deciduous forest that exists now in New York City. Today, there are remnants of this forest still extant, not only altered by many introduced species, but also not a true virgin forest because during the occupation by British and Hessian armies during the American Revolution the forests were entirely cut down on Manhattan Island to provide firewood and construction materials. The forest of the present time reestablished itself in many places with the withdrawal of the foreign troops. As most of the glacial deposits are covered by buildings or located in the adjacent waterways that make New York City an archipelago, finding fossils requires diligence at construction sites where, in general, the focus has been on Evo Edu Outreach (2008) 1:204–209 DOI 10.1007/s12052-008-0042-y

Holocene vegetation and fire regimes in subalpine and mixed conifer forests, southern Rocky Mountains, USA

Our understanding of the present forest structure of western North America hinges on our ability to determine antecedent forest conditions. Sedimentary records from lakes and bogs in the southern Rocky Mountains of Colorado and New Mexico provide information on the relationships between climate and vegetation change, and fire history since deglaciation. We present a new pollen record from Hunters Lake (Colorado) as an example of a high-elevation vegetation history from the southern Rockies. We then present a series of six sedimentary records from ~2600 to 3500-m elevation, including sites presently at the alpine–subalpine boundary, within the Picea engelmannii–Abies lasiocarpa forest and within the mixed conifer forest, to determine the history of fire in high-elevation forests there. High Artemisia and low but increasing percentages of Picea and Pinus suggest vegetation prior to 13 500 calendar years before present (cal yr BP) was tundra or steppe, with open spruce woodland to ~11 900 cal yr BP. Subalpine forest (Picea engelmannii, Abies lasiocarpa) existed around the lake for the remainder of the Holocene. At lower elevations, Pinus ponderosa and/or contorta expanded 11 900 to 10 200 cal yr BP; mixed conifer forest expanded ~8600 to 4700 cal yr BP; and Pinus edulis expanded after ~4700 cal yr BP. Sediments from lake sites near the alpine–subalpine transition contained five times less charcoal than those entirely within subalpine forests, and 40 times less than bog sites within mixed conifer forest. Higher fire episode frequencies occurred between ~12 000 and 9000 cal yr BP (associated with the initiation or expansion of south-west monsoon and abundant lightning, and significant biomass during vegetation turnover) and at ~2000–1000 cal yr BP (related to periodic droughts during the long-term trend towards wetter conditions and greater biomass). Fire episode frequencies for subalpine–alpine transition and subalpine sites were on average 5 to 10 fire events/1000 years over the Holocene, corresponding to one fire event every ~100 to 200 years. (5) Our Holocene-length sedimentary charcoal records provide additional evidence for the anomalous nature of the 20th-century fire regime, where fires were largely suppressed as a national policy.

Paleoecology of Organic Deposits of Probable Last Interglacial Age in Northern Ontario

Nonglacial deposits in northern Ontario that may date to the last interglacial interval are well known from the Hudson Bay Lowlands where they have been described in sections along several river valleys. Soil horizons, peat beds and other organic sediment sequences comprise the Missinaibi Formation of the Moose River Basin studied for pollen and macrofossils. Results suggest that the climate was as warm or warmer than present, and spruce woodlands prevailed among broad expanses of bog and fen. The Beaver River peat records conditions similar to the present in the Fort Severn area with open spruce woodlands dispersed in peatlands. South of the Lowlands in the Timmins area, a widespread organic-silt horizon termed the Owl Creek beds is stratigraphically equivalent to the Missinaibi Formation. The waning phase of a warm interval is represented, with early climate possibly similar to the present and the later climate much cooler. Correlation of the Missinaibi Formation with substage 5e of the deep-sea oxygen isotope record is corroborated by amino acid results on marine shells from some associated units. Analysis of shells from beneath the Beaver River peat bed indicate that this interval may be considerably younger, possibly substage 5c or, more likely, 5a. The Owl Creek beds may relate to sub-stage 5e, or to one of the younger intervals, 5c or 5a.

Paleolimnological evidence of limnetic nutrient concentration equilibrium in a shallow, macrophyte-dominated lake

Paleolimnological techniques were used to infer long-term changes in trophic status of Lake Opinicon (Ontario), a mesotrophic, shallow, macrophyte-dominated lake, and to assess whether these patterns support the hypothesis of 'alternative equilibria' proposed for shallow lake systems. Analysis of the diatom assemblages indicated cold, oligotrophic to mesotrophic, alkaline conditions during the period shortly following deglaciation (>11000 yr BP). With the establishment of an open spruce-woodland (ca. 11000 yr BP), benthic diatoms dominated, indicating shallow waters and the presence of macrophytes. Pieces of aquatic macrophytes also became common in the core. An increase in lake productivity to mesotrophic levels (diatom-inferred [TP] of 23 μg/L) occurred following the transition to a deciduous forest in the catchment ca. 7500 yr BP. Paleolimnological data did not indicate any significant change in limnetic nutrient concentrations resulting from the hemlock decline (ca. 4800 yr BP) or from extensive flooding with the construction of the Rideau Canal (1828-1832). Modest nutrient enrichment of the lake has occurred more recently with increasing agricultural and residential/recreational activities, with a diatom-inferred [TP] increase to 32 μg/L. However, compared to other, similarly-disturbed deep lakes in the area, Lake Opinicon showed much smaller changes in lakewater conditions, still maintaining a clear-water, mesotrophic state and a large macrophyte community.¶The apparent inertia of Lake Opinicon to changes in trophic status, as compared to other deep, near-by, stratifying lakes in southeastern Ontario, supports the 'alternative equilibria' hypothesis. Paleolimnological evidence suggests that Lake Opinicon has been in a clear-water, equilibrium state dominated by macrophytes since early in its development, and has displayed hysteresis to nutrient enrichment. These results may provide lake managers with important information for effective management strategies of shallow water systems in southeastern Ontario.

Reversion of Forest to Tundra in the Central Yukon

Pollen and plant macrofossil analyses of sediments from three sites in the central Yukon that are presently in shrub tundra provided a record of former forest establishment. Shrub tundra with groves and gallery forest of balsam poplar occupied the region between 10 000 and 8000 BP. At 9400 BP white spruce (Picea glauca) populations expanded, and open white spruce woodlands persisted until 6500 BP when black spruce (Picea mariana) and green alder (Alnus viridis) populations increased, resulting in open spruce woodlands with a distribution of species probably similar to that commonly found today in the northern boreal forest: white spruce on drier south—facing slopes and on alluvial sites with balsam poplar, and black spruce on colder, wetter sites on north—facing slopes and valley bottoms. At 5000 BP forest began to revert to shrub tundra, abruptly at first but then more gradually. The modern groves of spruce in the region, which are mostly white spruce, therefore are probably relict populations surviving in favorable microsites. These results support the conclusion from other recent studies that Alaska and northwest Canada experienced warmer summers than today from as early as 10 000 BP to °6000 BP in response to increased summer insolation arising from changes in the earth's orbital parameters as predicted by the Astronomic Theory of climate change. The decline of forest after 5000 BP is not associated with any significant changes in the abundance of shrub or herb pollen types, suggesting that the ground vegetation has behaved independently of the tree populations.

Holocene pollen and sediment record from the tangle lakes area, central Alaska

Abstract Pollen and sediments have been analyzed from a 5.5 meter‐length core of lacustrine sediments from Tangle Lakes, in the Gulkana Upland south of the Alaska Range (63 ° 01 ‘ 46”; N. latitude, 146° 03 ‘ 48 “ W. longitude). Radiocarbon ages indicate that the core spans the last 4700 years. The core sediments are sandy silt and silty clay; the core shows distinct rhythmic laminations in the lower 398 cm. The laminae appear to be normally graded; peat fibers and macerated plant debris are more abundant near the tops of the laminae. Six volcanic‐ash layers are present in the upper 110 cm of the core. Present‐day vegetation of the Tangle Lakes area is mesic shrub tundra and open spruce woodland, with scattered patches of shrub willow (Salix), balsam poplar (P. balsamifera), spruce (Picea), paper birch (Betula papyrifera), and alder (Alnus). Pollen analysis of 27 core samples suggests that this vegetation type has persisted throughout the past 4700 years, except for an apparently substantial increase in Pi...

The Modern and Late Quaternary Vegetation of the Campbell‐Dolomite Uplands, near Inuvik, N.W.T., Canada

The Campbell—Dolomite uplands comprise a small area (140 km2) of outcropping, faulted dolomite, limestone, and shale east of the Mackenzie River Delta, ~ 40 km south of the northern limit of trees. The major landforms are bedrock ridges and plateaux, steep colluvium, stable slopes, shorelines, and depressions. A principal component analysis of vegetation—cover data from 150 stands suggest that much of the variation within the heterogeneous vegetation is correlated with these broad habitat categories. Stable surfaces bear an open spruce woodland with alder, tree and dwarf birch, and a varied lichen—heath—Dryas ground vegetation. A glacially modified karstic (solution) depression contains a small (8 ha), relatively deep (22 m), apparently meromictic lake, which yielded a 12,000—yr core of sediment. A conventional percentage diagram, an influx diagram, and numerical analysis (principal components) suggest a sequence of pollen assemblage zones as follows: (1) Salix—Gramineae—Artemisia: 13,000 to 11,300 radiocarbon yr ago, (2) Betula (shrub)—Salix—Gramineae—Artemisia: 11,300 to 10,300, (3) Betula—Populus: 10,300 to 9,700, (4) Betula—Populus—Juniperus: 9,700 to 8,900, (5) Picea—Betula (tree and shrub)—Juniperus: 8,900 to 6,500, and (6) Picea—Betula—Alnus: 6,500 to present. Both percentage data and numerical analyses show that none of the pollen assemblage zones 1 to 5 has a modern analogue. With 1 exception, these patterns of change in pollen spectra can be interpreted parsimoniously without reference to regional environmental change. They suggest an initial phase of migration of willow and herbs from adjacent unglaciated Megaberingia (North Yukon and Alaska), followed rapidly by dwarf birch and later poplar. Megaberingian floristic elements (e.g., Plantago canescens, Selaginella sibirica) reached the area during this early phase of migration. Subsequently arriving from the south along the Mackenzie valley were juniper, ericads, spruce, and finally alder, which intensified competition and restricted the early Megaberingian herb types to open, unstable habitats where they persist today. Slow soil development (humus accumulation, rising permafrost table) probably favoured the spread of the palynologically 'silent' elements–lichens, ericads, and Dryas (the dominants of the modern ground vegetation). Changes in the influx values of Picea suggest a climatically induced increase in tree density and/or pollen production during the period 9,000—7,000 BP (Zone 5).

Pollen accumulation rates at Rogers Lake, Connecticut, during late- and postglacial time

Pollen accumulation rates have been estimated by dividing the pollen number per unit volume in 1 ml samples from a core from Rogers Lake, Connecticut, by the number of years represented by each sample. The latter variable was estimated from 24 radiocarbon-dated levels within the core. The result shows that total pollen deposition rose steepy from 1,000 /cm 2 / year, 14,000 years ago to 10,000/cm 2/year in later Late Glacial time, reaching a maximum of 40,000/cm 2/year, 9,000 years ago when the Pine Pollen Zone (B) was deposited. Subsequently the deposition rate fall to 20,000–25,000/cm 2/year, remaining stable at this level for the last 8,000 years. The pollen-percentage stratigraphy at Rogers Lake is similar to that at other sites in the vicinity. The changes in pollen percentages in sediments less than 8,000 years old directly reflect changes in deposition rates for these types, since the pollen total was almost constant. A rise in the numbers of Carya pollen grains took place about 5,000 years ago, and minimum rates for Tsuga-pollen deposition occurred between 1,500 and 4,000 years ago. These changes have been considered evidence for a xerothermic interval, but this event may be represented instead by the maximum in percentages and increase in deposition rates for Ambrosia pollen that occurred between 5,000 and 8,000 years ago. In sediments older than 8,000 years, the changes in pollen percentages are quite different from the changes in rates of pollen deposition of individual types. The pollen-accumulation-rate diagram shows that few pollen grains from trees were being deposited 12,000 years ago. Spruce pollen increased at that time, reaching a maximum 10,000 years ago, when an open spruce woodland may have grown in the region. Pine pollen began to increase 12,000 years ago, reaching maximum rates 9,000 years ago 18 times higher than the later Post-glacial rate. Oak pollen increased in numbers 12,000 years ago and held steady throughout the remainder of Late Glacial time, increasing rapidly by a factor of 30 during Early Postglacial time.