Spruce Pine Forests Research Articles

Geology and paleoecology of a Middle Wisconsin fossil occurrence in Zorra Township, southwestern Ontario, Canada

Nonglacial deposits of Middle Wisconsin age are being discovered with increased frequency across a broad region of southern Ontario, Canada, and provide strong evidence for a time of significant ice withdrawal from the lower Great Lakes region. With each new discovery, a refined understanding of regional climatic and paleoecological environments is emerging. In this paper, we present the results of a sedimentological and paleoecological study of a subtill organic deposit in Zorra Township, southwestern Ontario. The organic deposit, which lies beneath Nissouri Phase Catfish Creek Till (Late Wisconsin), has been dated by accelerator mass spectrometry at between 50.5 and 42.9 14C ka BP. The organic remains are contained within slack water pond deposits infilling a channel incised into till either of Early Wisconsin or Illinoian age. The fossil assemblage appears to be strongly influenced by taphonomic processes, including degradation due to oxidation, bacterial and fungal decay, and glacial overriding. Reworking and (or) recycling and selective sorting as well as long-distance transport has also influenced the composition of the fossil assemblage preserved. Nonetheless, meaningful paleoecological information is still obtained from this record. Collectively, the pollen and plant macrofossils indicate a boreal-type pine–spruce forest with temperatures cooler than present. The absence of arctic tundra plants, as are found in many other deposits of similar age in the lower Great Lakes basin, is notable. A pond or wetland inhabited by shoreline herbs, shrubs, and trees was present at or proximal to the site. The freshwater mollusc and ostracode assemblages are consistent with a shallow water habitat with dense submerged vegetation. The terrestrial mollusc assemblage suggests a taiga or transitional taiga–tundra fauna. Together, these fossil groups provide one of the most comprehensive environmental reconstructions of Middle Wisconsin time (oxygen isotope stage 3 or OIS3) in southern Ontario and serve to build on the ever-increasing database of paleoecological information accumulating for this episode of the late Quaternary.

Paleogeography of the environment in north-eastern Poland recorded in an Eemian sedimentary basin, based on the example of the Jałówka site

The paper presents the results of the research on biogenic sediments from the Jałówka profile (Podlasie region, NE Poland) situated at the foot of a dry valley slope. A 35 cm monolith of sediments was collected from the excavation pit. The sediments were deposited beneath 4 m thick mineral sediments. Interdisciplinary research helped to reconstruct the possible transformations of the local environment. Palynological, physical, and geochemical analyses were applied to organic sediments, and plant macroremains were examined. Five local pollen zones were identified in palynological terms and correlated with the late Warta Stadial (MIS 6) of the Odra Glaciation (Saalian), and four older periods of the Eemian Interglacial: MIS 5e (E1, E2, E3 and E4). Younger zones have not been preserved. They were eroded in the early Vistulian. During the late MIS 6, there was a eutrophic water body with highly transparent water, characterized by a relative stable water level. The landscape was dominated by tundra with a high proportion of Juniperus–Artemisia. Curves of oxygen (δ18O) and carbon (δ13C) stable isotopes confirmed the boundary between MIS 6 and MIS 5e. The beginning of the interglacial vegetation succession (E1) was characterized by expansion of birch–pine–spruce forests. Probably at the end of this period, the lake became shallower. E2 is distinguished by the dominance of pine and birch. The lake was replaced by a peat bog. The sequence of vegetation succession in the landscape was as follows: Quercus (E3), Corylus, Fraxinus-Alnus and Tilia (E4). Probably, the peat bog drained in the E4 and the water level rose again in the climate optimum of the Eemian Interglacial. The results of physical and geochemical analysis clearly corresponded with climatic changes determined by palynological analysis. They provided evidence of the changing redox conditions, variability and intensity of denudation, the scale of biological productivity, and fertility of the environment. The studied sediments were characterized by reducing conditions. The increase in terrigenous silica content and the relatively high N:K ratio indicated the predominance of mechanical denudation during the late glacial period of the Warta Stadial and the E2 period.

100,000-year-long terrestrial record of millennial-scale linkage between eastern North American mid-latitude paleovegetation shifts and Greenland ice-core oxygen isotope trends

We document frequent, rapid, strong, millennial-scale paleovegetation shifts throughout the late Pleistocene, within a 100,000+yr interval (~115–15ka) of terrestrial sediments from the mid-Atlantic Region (MAR) of North America. High-resolution analyses of fossil pollen from one core locality revealed a continuously shifting sequence of thermally dependent forest assemblages, ranging between two endmembers: subtropical oak-tupelo-bald cypress-gum forest and high boreal spruce-pine forest. Sedimentary textural evidence indicates fluvial, paludal, and loess deposition, and paleosol formation, representing sequential freshwater to subaerial environments in which this record was deposited. Its total age–depth model, based on radiocarbon and optically stimulated luminescence ages, ranges from terrestrial oxygen isotope stages (OIS) 6 to 1. The particular core sub-interval presented here is correlative in trend and timing to that portion of the oxygen isotope sequence common among several Greenland ice cores: interstades GI2 to GI24 (≈OIS2–5d). This site thus provides the first evidence for an essentially complete series of ‘Dansgaard–Oeschger’ climate events in the MAR. These data reveal that the ~100,000yr preceding the Late Glacial and Holocene in the MAR of North America were characterized by frequently and dynamically changing climate states, and by vegetation shifts that closely tracked the Greenland paleoclimate sequence.

Late Quaternary pedogenesis in periglacial zone of northeastern Europe near ice margins since MIS 3: Timing, processes, and linkages to landscape evolution

Two paleosol-sedimentary sequences Koskovo and Puzbol developed within the nearest periglacial zone of Valday glaciation of the East European Plain (56.7°–58.5° N, the Upper Volga River basin) were studied to reconstruct soil mantle and landscape evolution since Marine Isotope Stage (MIS) 3. The sequences are formed on terraces at 130–141 and 172m a.s.l., constituted by ancient (Early Valday (Würm) or Late Moscow (RissII)) lake clayey sediments. The buried paleosols are represented by system of horizons Hb–G3b (Histosol), Agb–G3b and AGb horizon (Umbric Gleysol). The 14C age of the paleosol humus and peat varied between 50,300–39,700 cal. BP. These paleosols were developed under forest-tundra and pine-spruce forests with the meadow plant communities and the areas of swampy vegetation according to palynological data from Puzbol. They represent the northernmost occurrence of the MIS3 fossil soil in Europe dominated by the features of gleyzation, cryogenic aggregation, cracking, and humus and peat formation. Clay coatings in the Middle Valday paleosols and pedosediments are products of Holocene pedogenesis.The upper lithological layers covering the MIS3 paleosols are loess-like (mantle) loams underlain by clayey Late Pleistocene lake deposits. They mark the presence of wide extraglacial lakes with existed within the Upper Volga basin during the maximum advance of the Valday glaciation (MIS2). Based on the stratigraphy of the studied sections, the highstands of these Late Quaternary lakes might exceed ≈170m a.s.l.For the first time it was possible to date the age of humus-clay coatings developed in the Bthk3 horizon (c.1.6–2.0m) of Puzbol where in the upper part of the section the Cutanic Albeluvisol formed. The Early Middle Holocene age of humic acid of humus-clay coatings (≈10,900 cal. BP) and carbonate nodules 7500–8180 cal. BP refer to the first stage of pedogenesis of this polygenetic soil, which occurred from pre-Boreal to the Atlantic period, and was characterized by dark humus accumulation and carbonate precipitation in a poorly drained landscape. The 14C age of the fulvic acids of these coatings (≈6130 cal. BP) is indicative of the beginning of the second stage, dominated by clay illuviation under a better drained, leaching environment.

The European bison as seed dispersers: the effect on the species composition of a disturbed pine forest community

We studied the process of change in plant species composition in a pine–spruce forest influenced by endozoochorous seed dispersal by the European bison Bison bonasus L. The intensity of endozoochory was 3.4 times higher in the open tree stand than in the surrounding undisturbed forest (t = –3.0836, df = 50, P = 0.003). Over 1578 individuals/ramets belonging to 23 vascular plant taxa developed on 114 bison dung piles. The process of colonization included two plant species that have never before been recorded in the studied forest community. Seven out of 14 species transferred by bison were small-seeded herbaceous plants without morphological adaptations for long-distance dispersal. The majority of plant species recorded on the bison dung (55.9%) occur in deciduous forests. In contrast, over 50% of the plants surrounding bison faeces represented species of coniferous forests. The PCA analysis revealed the existence of two distinct groups of plant species: within bison faeces and on random systematic samples. The Jaccard coefficient of species composition similarity between them was 0.28. Our results demonstrate that the European bison is an effective vector of plant propagules between plant communities. This fact could have great importance for the restoration of degraded habitats, and could also introduce the risk of invasion by alien species.

Vegetation and climate changes during the Eemian and Early Weichselian in the Upper Volga region (Russia)

Ples is the key-section that represents the Mikulino (Eemian) interglaciation and early part of the Valdai (Weichselian) glacial epoch in the north-central Russia. Pollen profile of this section reflects spread of the broad-leaved forest dominated by Quercus, Ulmus, and Tilia with participation of Acer, Fraxinus and Carpinus in the optimum phase of the interglaciation. A gradual cooling and increasing humidity of climate brought about a decline in the broad-leaved forest and development of dark-coniferous communities ( Picea-Abies-Pinus sibirica) in the end of the interglaciation. It was followed by Scots pine and birch forest, and then replaced by communities of tundra shrubs with patches of the open birch forest. During the first post-Eemian cooling the climatic conditions were not uniform, as a short climatic amelioration separated it into two stages. This minor warming is indicated by an increase in birch woodland in complex plant cover. This first Early Weichselian cold stage was followed by a warm interstade, when mixed spruce-birch, and later larch-pine and spruce-pine forests occupied the region. This interstade, known as Verkhnevolzhskiy (Upper Volga) in the climatostratigraphic subdivision of the Late Pleistocene in the Russian Plain (after Grichuk [1961. Fossil floras as the basis for the Quaternary stratigraphy. In: Markov, K.K. (Ed.), Rel`ef i Stratigrafiya Chetvertichnykh Otlozheniy Severo-zapada Russkoi Ravniny, Izdatel'stvo AN SSSR, Moscow, pp. 25–71]), corresponds to the Brörup interstade in the northern Europe, or to Marine Oxygen Isotope Substage (MIS) 5c (e.g. Mangerud [1989. Correlation of the Eemian and the Weichselian with deep sea oxygen isotope stratigraphy. Quaternary International 3, 1–4.]). On the whole, we correlate the sediment sequence at Ples to the MIS from 5e to 5c.

Классификация бореальных лесов севера Европейской России. I. Олиготрофные хвойные леса

Results of a syntaxonomical study of the oligotrophic forests of northern European Russia are presented. The main forest types have been classified into 2 orders of the class Vaccinio-Piceetea, 4 alliances, 6 associations and 1 community. The new alliance Empetro-Piceion all. nov., which includes zonal spruce and birch northern forest association Empetro-Piceetum, has been established. These communities are formed according to cold temperature and high (sometimes temporarily) soil moisture and are characterized by the lower tree canopy, mosaic herb and moss-lichen layers with boreal mosses, sphagnum and lichens. In the middle taiga subzone these communities are replaced by Eu-Piceetum myrtilletosum. The forests with lichens are referred to order Cladonio-Vaccinietalia and divided into 4 associations. Lichen pine forests of the north-west of boreal zone were described as ass. Flavocetrario nivalis—Pinetum ass. nov. This association with a great number of lichens is differentiated by Cladonia arbuscula subsp. mitis, Flavocetraria nivalis, Cetraria ericetorum, Stereocaulon grande, Dicranum fuscescens, D. drummondii, Nephroma arcticum and species of Cladonia. The ass. Cadonio arbusculae—Pinetum (Caj. 1921) K.-Lund 1967 contains lichen pine forests with lower number of lichens and is distributed mostly in middle part of the taiga zone. The spruce-pine forests with mixed moss-lichen cover correspond to ass. Vaccinio-Pinetum. Ass. Hedysaro-Laricetum represents rich and well differentiated larch forests in the east of European Russia.

Effects of Artificial Defoliation of Pines on the Structure and Physiology of the Soil Fungal Community of a Mixed Pine-Spruce Forest

Loss of photosynthetic area can affect soil microbial communities by altering the availability of fixed carbon. We used denaturing gradient gel electrophoresis (DGGE) and Biolog filamentous-fungus plates to determine the effects of artificial defoliation of pines in a mixed pine-spruce forest on the composition of the fungal community in a forest soil. As measured by DGGE, two fungal species were affected significantly by the defoliation of pines (P < 0.001); the frequency of members of the ectomycorrhizal fungus genus Cenococcum decreased significantly, while the frequency of organisms of an unidentified soil fungus increased. The decrease in the amount of Cenococcum organisms may have occurred because of the formation of extensive hyphal networks by species of this genus, which require more of the carbon fixed by their host, or because this fungus is dependent upon quantitative differences in spruce root exudates. The defoliation of pines did not affect the overall composition of the soil fungal community or fungal-species richness (number of species per core). Biolog filamentous-fungus plate assays indicated a significant increase (P < 0.001) in the number of carbon substrates utilized by the soil fungi and the rate at which these substrates were used, which could indicate an increase in fungal-species richness. Thus, either small changes in the soil fungal community give rise to significant increases in physiological capabilities or PCR bias limits the reliability of the DGGE results. These data indicate that combined genetic and physiological assessments of the soil fungal community are needed to accurately assess the effect of disturbance on indigenous microbial systems.

Was the High Plains a Pine-Spruce Forest?

Twenty thousand years ago a sheet of ice more than a mile thick mantled the Northern Plains, the Midwest, and most of Canada. The ice sheet, called the Laurentide, was the last of several Ice Age glaciers that plowed through the north (Fig. 1). The cold climate that spawned the ice sheet also changed the distribution of plants and animals everywhere in the world. Ecologists speculated that the Great Plains prairies may have disappeared entirely, replaced by forests. Far from the ice sheet, the Llano Estacado or High Plains of

Environmental history and tephrostratigraphy at Carp Lake, southwestern Columbia Basin, Washington, USA

Sediment cores from Carp Lake provide a pollen record of the last ca. 125,000 years that helps disclose vegetational and climatic conditions from the present day to the previous interglaciation (120–133 ka). The core also contained 15 tephra layers, which were characterised by electron-microprobe analysis of volcanic glass shards. Identified tephra include Mount St. Helens Ye, 3.69 ka; Mazama ash bed, 7.54 ka; Mount St. Helens layer C, 35–50 ka; an unnamed Mount St. Helens tephra, 75–150 ka; the tephra equivalent of layer E at Pringle Falls, Oregon, <218 ka; and an andesitic tephra layer similar to that at Tulelake, California, 174 ka. Ten calibrated radiocarbon ages and the ages of Mount St. Helens Ye, Mazama ash, and the unnamed Mount St. Helens tephra were used to develop an age–depth model. This model was refined by also incorporating the age of marine oxygen isotope stage (IS) boundary 4/5 (73.9 ka) and the age of IS-5e (125 ka). The justification for this age-model is based on an analysis of the pollen record and lithologic data. The pollen record is divided into 11 assemblage zones that describe alternations between periods of montane conifer forest, pine forest, and steppe. The previous interglacial period (IS-5e) supported temperate xerothermic forests of pine and oak and a northward and westward expansion of steppe and juniper woodland, compared to their present occurrence. The period from 83 to 117 ka contains intervals of pine forest and parkland alternating with pine–spruce forest, suggesting shifts from cold humid to cool temperate conditions. Between 73 and 83 ka, a forest of oak, hemlock, Douglas-fir, and fir was present that has no modern analogue. It suggests warm wet summers and cool wet winters. Cool humid conditions during the mid-Wisconsin interval supported mixed conifer forest with Douglas-fir and spruce. The glacial interval featured cold dry steppe, with an expansion of spruce in the late-glacial. Xerothermic communities prevailed in the early Holocene, when temperate steppe was widespread and the lake dried intermittently. The middle Holocene was characterised by ponderosa pine forest, and the modern vegetation was established in the last 3900 yr, when ponderosa pine, Douglas-fir, fir, and oak were part of the local vegetation.

Flux-profile relationships over a boreal forest — roughness sublayer corrections

Calculation of fluxes from profile measurements above forest stands have for some time been considered unfeasible and profiles have primarily been used to only characterise the lowest part of the planetary boundary layer. Extension of traditional theory to correctly relate fluxes to gradients would provide both new insight into transfer processes and a way to measure fluxes. This paper presents measurements and analysis of profiles of wind speed, air temperature and humidity, and also eddy-correlation fluxes under unstable conditions. The measurements were carried out at the NOPEX Central Tower Site 30km north of Uppsala, Sweden. This site represented a mixed pine-spruce forest of a height of about 24.5m. The displacement height (d) was found to be 21.1m. A roughness sublayer with enhanced eddy diffusivities and decreased gradients was found above the forest. This was accounted for by multiplying the traditional non-dimensional gradients with a correction function of the form φu,t,q=(z/z*)n (z denotes height above d). φ was a linear function of height (n=1) for temperature and humidity with their roughness sublayer height z*=35.9m. Enhancement of momentum exchange and its extension were lower (n=0.6, z*=23.9m). The fluxes calculated from profiles by a method which took into account the roughness sublayer corrections were generally in good agreement with those measured by the eddy-correlation method.

Deglaciation and Postglacial Vegetation History of the West Mountains, West-central Idaho, U.S.A.

The West Mountains, west-central Idaho, were deglaciated before ca. 11,500 BP, as indicated by radiocarbon ages and Glacier Peak tephra, at several sites in cirques. Pollen analysis of a sediment core, and plant macrofossils from sediments recovered from the cirque at the head of Van Wyck Creek, indicate that a closed spruce-pine forest surrounded the site from ca. 11,500 to 9800 BP. Early in this period, spruce (probably krummholz) was already growing near the present-day altitudinal limit of large upright spruce. Hence, the climate during this period was significantly warmer than before 11,500 BP. Between ca. 9800 and 3200 BP the climate was warmer and drier than present. Pollen data indicate that from ca. 9300 to the time of Mazama tephra deposition (ca. 6700 BP), the climate was warmer and drier than at any time since 11,500 BP. From ca. 6700 to 3200 BP there was a small decrease in temperature with a minor increase in effective moisture. Beginning ca. 3200 BP, the climate was characterized by cooler temperatures and more mesic conditions. Modern plant communities were established by ca. 1500 BP.

Change of the morphological structure of leaves of Vaccinium vitisidaea caused by heavy metal pollution

The objective of the present investigation is to study the specific effect of the “Severonickel” smelting complex emissions on processes in the soil-plant system. The experiment was carried out in the central part of the Kola Peninsula in a spruce-pine forest in the northern taiga zone and included 5 field sites treated with contaminants of differing compositions (water soluble and hard soluble copper and nickel contaminants). In the beginning of the experiment high amounts of copper and nickel in plant tissue were found in the sites treated with hard soluble contaminants which is caused by precipitation of insoluble particles on the surface of the leaves. In two years the plants began to take up the available forms of nickel and copper from the soil. Easily water soluble contaminants damaged the epidermis of plant leaves to a greater extent than the hard soluble ones, epidermal cells were collapsed, cuticular structures and stomatal complexes destroyed.

A postglacial pollen and nonsiliceous algae record from Gegoka Lake, Lake County, Minnesota

As part of a multidisciplinary investigation of the Misiano archaeological site, pollen and nonsiliceous algae were recovered from a 262 cm core from Gegoka Lake, Lake County, Minnesota. The palynomorph assemblage from Gegoka Lake records changes in local and regional vegetational and lake productivity over the past 10 000 years. Pollen spectra indicate that vegetation progressed from a shrub parkland/open conifer forest, to a spruce-pine forest, to a mixed conifer-hardwood forest. Pinus banksiana/resinosa is replaced by Pinus strobus about 7000 years ago. A small rise in Gramineae in the upper 17.5 cm of the core is attributed to the expansion of wild rice (Zizania aquatica) in Gegoka Lake. Four cycles of nutrient enrichment are indicated by the Pediastrum and Scenedesmus maxima in the nonsiliceous algae record. Oscillations in the nonsiliceous algae abundance probably result from changing environmental and/or limnologic conditions. The decline in nonsiliceous algae in the upper 57.5 cm of the core suggests that there has been an apparent shift to more nutrient poor conditions in Gegoka Lake in the recent past.

Grassland Vegetation in the Southern Great Plains during the Last Glacial Maximum

New pollen records from White Lake in the Southern High Plains and from Friesenhahn Cave on the southeastern Edwards Plateau of Texas indicate that the glacial-age vegetation of the southern Great Plains was a grassland. The High Plains was a treeless Artemisia grassland and the Edwards Plateau, at the south edge of the Great Plains, was a grassland with pinyon pines and deciduous trees in canyons and riparian habitats. The glacial-age grasslands differ from modern shortgrass and tallgrass prairies and may have no modern analog. The dominance of prairie vegetation during the last glacial maximum is compatible with late Pleistocene mammalian faunas and late-glacial grassland pollen records from the region. Earlier interpretations of a pine-spruce forest on the High Plains were based on pollen assemblages that are here shown to have been altered by postdepositional deterioration, resulting in differential preservation of conifer pollen grains. Accordingly, the "Tahoka Pluvial" and other "climatic episodes" defined by High Plains pollen records are abandoned.

Recent acidification and biological changes in Lilla Öresjön, southwest Sweden, and the relation to atmospheric pollution and land-use history

Palaeolimnological techniques were used to study the recent acidification history of Lilia Oresjon in southwest Sweden, and its relation to the deposition of airborne pollutants and land-use. The sediment analyses suggest that water quality began to deteriorate at the beginning of the 20th century and resulted in an acute acidification phase in the 1960s. An indifferent (circumneutral) diatom flora with some planktonic taxa was replaced by a non-planktonic acidophilous and acidobiontic flora; diatom inferred pH decreased from 6.1 in the 19th century to the present value of about 4.6. The history of acidification and of major biological change in the lake is reinforced by the analyses of chrysophyte scales and cladocera and chironomid remains, which show that alterations of species composition and an impoverishment of faunal communities took place. There is close stratigraphic agreement between these biological changes and indicators of the deposition of atmospheric pollutants. The concentration of Pb, Zn, Cu and S increased from the beginning of the 19th century to peak values during the 1960s and 1970s. Spheroidal carbonaceous particles, polycyclic aromatic hydrocarbons (PAH) and ‘hard’ isothermal remanence, indicative of oil and coal combustion, peaked during the 1970s and 1980s, respectively. The increased deposition of airborne pollutants from fossil fuel combustion and industrial processes is suggested as the main cause of the acidification of the lake, although vegetation changes, such as a recent expansion of spruce-pine forest, have also occurred during the 200—300 year period studied.

Input, accumulation, and residence times of carbon, nitrogen, and phosphorus in four Rocky Mountain coniferous forests

Annual aboveground litterfall in forests of Pinuscontorta Loud., Piceaglauca (Moench) Voss, Piceaengelmannii Parry ex Engelm., and Abieslasiocarpa (Hook.) Nutt. in southwestern Alberta ranged from 286 to 321 g•m−2•year−1. The mass of litter accumulated on the forest floors ranged from 6.3 to 11.0 kg•m−2. Residence times of organic matter in the forest floor were 11 years in a 90-year-old P. contorta stand, 16 years in a 120-year-old P. glauca–P. contorta stand, and 23 years in a 350-year-old P. engelmannii–A. lasiocarpa stand. Residence times of litter in the L layer of the forest floor were longer in a recently clearcut area than in the older forests. Residence times of individual nutrients in the forest floors were in the order N &gt; P &gt; C. Litter in the pine forest had lower concentrations of both N and P than did litter in the spruce–pine forest; litter in the spruce–fir forest had relatively high N and low P concentrations. Differences in nutrient concentrations of litter among sites reflected differences in the nutrient-use efficiency of the vegetation, suggesting that the species composition of vegetation is important in determining availability of nutrients in the floor of these forests.

Biomass, productivity, and nutrient-use efficiency of aboveground vegetation in four Rocky Mountain coniferous forests

Aboveground biomass, annual production, and internal nitrogen and phosphorus dynamics of vegetation were compared among a 90-year-old Pinuscontorta Loudon forest, a 120-year-old Piceaglauca (Moench) Voss–P. contorta forest, a 350-year-old Piceaengelmannii Parry ex Engelm.–Abieslasiocarpa (Hook.) Nutt. forest, and a 13-year-old P. contorta stand in the Rocky Mountains of southwestern Alberta. Aboveground biomass of vegetation ranged from 109 to 203 t•ha−1, while aboveground net primary productivity ranged from 4.4 to 5.3 t•ha−1•year−1 in the mature forests. Approximately 30% of the N and 20–40% of the P in ground vegetation were reabsorbed during senescence; 40–50% of the N and 50–80% of the P were reabsorbed from senescing tree foliage. Annual uptake of nutrients (production minus reabsorption) was between 1.8 and 2.2 g•m−2•year−1 for N and 0.2–0.4 g•m−2•year−1 for P. Efficiency of nutrient use (milligrams of new biomass produced per milligram of nutrient taken up in 1 year) ranged from 249 to 262 for N and 1604 to 2355 for P in the mature forests, and 72 and 642, respectively, in the young pine stand. Both N and P were used very efficiently in the pine forest and relatively inefficiently in the spruce–pine forest, reflecting differences in the inherent nutrient-use efficiency of these tree species. In the spruce–fir forest, N was used less efficiently and P more efficiently than in other forests, in response to lower phosphorus availability in this forest. Differences in nutrient-use efficiency of vegetation were related to differences in the amount of biomass produced per unit amount of N or P taken up, and not to differences in efficiency of N or P reabsorption.

Ecology of Lichen and Bryophyte Communities in Saskatchewan

Lichen and bryophyte communities have been classified in five associations whose primary affinities with the vascular vegetation are: Parmelietum chlorochroae with the declining phase of the Astragaletum caespitosi; Cladonietum nemoxynae with the Astragaletum pectinati; initial phase of the Cladonietum multiformis with Danthonion intermediae associations; the Cladonietum multiformis typicum with dry pine and pine—spruce forest; the Cladonietum alpestris with damp pine—spruce and spruce forest; the Physcientum muscigenae with dry, open vegetation and overgrazed grassland. The general ecology of lichens and bryophytes is discussed and the associations are regarded as unions in a phytocoenose occupying niches created by the vascular vegetation. Lichen and bryophyte life forms are considered indicators of gross climatic conditions; their indicative value is mainly quantitative as expressed in the biological spectra of the associations. Cryptogams are believed important as ecological indicators....

Postglacial Vegetation of the North-Central United States: A Review

The dramatic changes in climate and physiography following the retreat of the last glaciers are reflected in the record of forest succession as gleaned from pollen studies made chiefly in the Great Lakes area. Fairly rapid deglaciation began about 8500 B.C. while spruce-fir forests still dominated (Valders Retreat). Soon the pine came in, and spruce-pine forests took over (about 7000 B.C.). At the time of the Terminal Glacial (Cochrane, 6000 B.C.) pine was the dominant forest tree, whereas spruce-fir forests had migrated north. During the following three thousand years, while the climate was warmer and drier, pine forests were dominant. Then broad-leaved trees (oaks) made their appearance. First came an oak stage that extended until about 1000 B.C. It was followed, during the next five hundred years, by an oak-hickory stage. The period from 7000 to 600 B.C. is now known as the "hypsithermal interval" rather than by its former, but less suitable, designations (postglacial climatic optimum, thermal maximum) and as such has been correlated with corresponding stages in the European sequence and postglacial chronology. The various radiocarbon dates based oil different sites and carried out in different laboratories have not yet been completely aligned but show considerable agreement with other sources of evidence. Events during Late Glacial and postglacial times apparently had a more far-reaching effect on present-day distribution patterns of plants and animals than did those of the various Glacial and Interglacial periods. These pronounced postglacial changes in climate and physiography definitely affected the mode of life of various paleo-Indian groups living in this region.