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  • 1
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    Response of black spruce (Piceamariana) ecosystems to soil temperature modification in interior Alaska (1990)
    Canadian Science Publishing
    Details
    Publication Date: 1990-09-01
    Description: This paper reports results of a study designed to examine the control that soil temperature exerts on soil processes associated with nutrient flux, and in turn, on tree nutrition in interior Alaska black spruce ecosystems. Approximately 50 m2 of forest floor in a 140-year-old black spruce ecosystem, which had developed on permafrost, was heated to 8–10 °C above ambient temperature. This perturbation amounted to approximately a 1589 degree-day seasonal heat sum (above 0 °C), 1026 degree-days above the control total of 563 degree-days. The forest floor, surface 5 cm of mineral soil, and soil solution were compared with those of an adjacent control plot to evaluate the change in nutrient content and decomposition rate of the forest floor. The nutritional response to soil heating of current black spruce foliage also was evaluated. Soil heating significantly increased decomposition of the forest floor, principally because of an increase in biomass loss of the O21 layer. The increased decomposition resulted in greater extractable N and P concentrations in the forest floor, higher N concentrations in the soil solution, and elevated spruce needle N, P, and K concentrations for the experimental period. These results are discussed in light of the importance of soil temperature and other state factors that mediate ecosystem function.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 2
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    Soil temperature, nitrogen mineralization, and carbon source–sink relationships in boreal forests (1992)
    Canadian Science Publishing
    Details
    Publication Date: 1992-05-01
    Description: Boreal forests contain large quantities of soil carbon, prompting concern that climatic warming may stimulate decomposition and accentuate increasing atmospheric CO2 concentrations. While soil warming increases decomposition rates, the accompanying increase in nutrient mineralization may promote tree growth in these nutrient-poor soils and thereby compensate for the increased carbon loss during decomposition. We used a model of production and decomposition to test this hypothesis. In black spruce (Piceamariana (Mill.) B.S.P.), white spruce (Piceaglauca (Moench) Voss), and paper birch (Betulapapyrifera Marsh.) forests, decomposition increased with the soil warming caused by a 5 °C increase in air temperature. However, increased nitrogen mineralization promoted tree growth, offsetting the increased carbon loss during decomposition. In the black spruce forest, increased tree production was maintained for the 25 years of simulation. Whether this can be maintained indefinitely is unknown. In the birch forest, tree production decreased to prewarming levels after about 10 years. Our analyses examined only the consequences of belowground feedbacks that affect ecosystem carbon uptake with climatic warming. These analyses highlight the importance of interactions among net primary production, decomposition, and nitrogen mineralization in determining the response of forest ecosystems to climatic change.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 3
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    Soil nutrient availability and relationships with aboveground biomass production on postharvested upland white spruce sites in interior Alaska (1993)
    Canadian Science Publishing
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    Publication Date: 1993-06-01
    Description: Soil nutrient availability was assessed on unharvested white spruce (Piceaglauca (Moench) Voss) sites, on a recently harvested site and on 14-year-old postharvested sites stratified into four different regeneration types defined by surface soil conditions and colonizing species. These values were compared with field aboveground biomass production that had been estimated in a previous study and with biomass production of bioassay seedlings. All sites were upland and south facing. On this range of sites, laboratory net N mineralization was the soil characteristic that was the most strongly associated with plant growth in the field as well as in the greenhouse bioassay. The significance of this relationship was mainly caused by the presence of sites regenerating to aspen (Populustremuloides Michx.) which showed high plant biomass production and high soil N availability. Total soil N content, cumulative field soil temperature and soil moisture content were poorly related to N mineralization estimates and to plant biomass production. Soil temperature had an effect on N mineralization and plant growth only when sites where the forest floor had been scraped during the harvesting operations, were included in the computations. Despite a higher soil temperature, these sites showed decreased N mineralization rates and decreased plant biomass production. These results suggest that on south facing postharvested white spruce sites (i) soil temperature does not show enough variability to be an important factor controlling nutrient availability and plant growth unless the soil is severely disturbed, (ii) the rate of N mineralization is controlled by a small pool of rapidly cycling N which is poorly related to forest floor total N concentrations, and (iii) N availability and vegetation production vary with regeneration type.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 4
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    Relationships between CO2 evolution from soil, substrate temperature, and substrate moisture in four mature forest types in interior Alaska (1985)
    Canadian Science Publishing
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    Publication Date: 1985-02-01
    Description: A soda lime technique was used to measure CO2 evolution at the soil surface in four mature forest types (aspen (Populustremuloides Michx.), paper birch (Betulapapyrifera Marsh.), black spruce (Piceamariana (Mill.) B.S.P.), and white spruce (Piceaglauca (Moeneh) Voss)) in interior Alaska. Surface temperature, 15-cm depth temperature, and soil moisture were measured concurrently with CO2 evolution. Accumulated CO2 evolution ranged from 1315 to 1654 g CO2•m−2 for the period May 1 – September 30 in 1981 and 1982 in the four stands. Data were used to develop three-dimensional response surfaces and test mathematical models of respiration in relation to substrate temperature and moisture. GRESP, a biologically based model, provided a fairly accurate simulation of the seasonal course of respiration as a function of substrate temperature and moisture. In an attempt to better define the observed response surface trends, a best-fit equation model, BRESP, was formulated. BRESP includes the moisture portion of the GRESP equation, and an altered temperature equation which more adequately defines the upper and lower thresholds of respiration in relation to substrate temperature. GRESP and BRESP each produced similar r2 values; however, higher order polynomial equations gave a better-fit model. The weakest area of all models for simulating seasonal trends was during the periods of peak respiration in June.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 5
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    Weight loss of litter and cellulose bags in a thinned white spruce forest in interior Alaska (1978)
    Canadian Science Publishing
    Details
    Publication Date: 1978-03-01
    Description: Thinning in a white spruce, Piceaglanca (Moench) Voss, forest in interior Alaska stimulated organic matter decomposition in the forest floor as indicated by weight loss of litter and cellulose bags. The general higher weight loss in the most heavily thinned plot is attributed to observed higher average seasonal temperatures. Cellulose bags placed in the boundary between the fermentation–humus and the humus–mineral soil layers of the forest floor showed a significantly higher weight loss than those placed on top of the litter layer. This was attributed to more favorable moisture conditions and a more direct contact with the decomposing microbial populations in the fermentation–humus and humus–mineral soil layers.Regardless of thinning treatment, elements were grouped according to their rate of release from decomposing organic matter as follows: K 〉 Mg 〉 C ≈ P ≈ N ≈ Ca, where potassium is lease resistant. Since relatively small differences in weight loss of litter bags were observed between the treatments, similar studies should extend over a longer period in order to obtain a better understanding of the decomposition processes.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 6
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    Influence of phosphorus on growth and biomass distribution of Alaskan taiga tree seedlings (1983)
    Canadian Science Publishing
    Details
    Publication Date: 1983-12-01
    Description: Seedlings of six Alaskan taiga tree species and one tall shrub were grown in sand at three phosphate levels. There was a positive correlation between the growth rate of a species at the high-phosphate level in sand culture and its productivity in the natural environment. Poplar (Populusbalsamifera L.), which had highest growth rate under high phosphate, was most sensitive to reduction in phosphate supply, followed by birch (Betulapapyrifera (Reg.) Fern, and Raup) and aspen (Populustremuloides Michx.), whereas growth of conifers (larch (Larixlaricina (Du Roi) K. Koch), white spruce (Piceaglauca (Moench) Voss), and black spruce (P. mariana (Mill.) B.S.P.)) from late successional sites was slow and unaffected by phosphate supply. Similarly, when birch and white spruce seedlings were transplanted into natural forest stands, the maximum growth rate of birch was greater than that of white spruce, but birch growth was curtailed more by unfavorable conditions than was that of white spruce. We conclude that a slow growth rate reduces nutrient requirement and therefore minimizes nutrient stress on infertile sites, whereas a rapid growth enables nutrient-demanding species to dominate fertile sites.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 7
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    Vegetation, soils, and forest productivity in selected forest types in interior Alaska (1983)
    Canadian Science Publishing
    Details
    Publication Date: 1983-10-01
    Description: Vegetation, forest productivity, and soils of 23 forest stands in the taiga of interior Alaska are described. The stands are arranged on an environmental gradient from an aspen (Populustremuloides Michx.) stand on a dry, steep south-facing bluff, to open black spruce (Piceamariana (Mill.) B.S.P.) stands underlain by permafrost on north-facing slopes. The coldest site is a mixed white spruce (Piceaglauca (Moench) Voss) and black spruce woodland at the treeline. Mesic upland sites are represented by successional stands of paper birch (Betulapapyrifera Marsh.) and aspen, and highly productive stands of white spruce. Several floodplain stands represent the successional sequence from productive balsam poplar (Populusbalsamifera L.) and white spruce to black spruce stands underlain by permafrost on the older terraces. The environmental gradient is described by using two soil factors: soil moisture and annual accumulated soil degree days (SDD), which range from 2217 SDD for the warmest aspen stand to 480 SDD for the coldest permafrost-dominated black spruce site. Soils vary from Alfie Cryochrepts on most of the mesic sites to Histic Pergelic Cryochrepts on the colder sites underlain by permafrost. A typical soil profile is described for each major forest type. A black spruce stand on permafrost has the lowest tree standing crop (15806 g•m−2) and annual productivity (56 g•m−2•year−1) whereas a mature white spruce stand has the largest tree standing crop (24 577 g•m−2) and an annual productivity of 540 g•m−2•year−1, but the successional balsam poplar stand on flood plain alluvium has the highest annual tree increment (952 g•m−2•year−1). The study supports the hypothesis that black spruce is a nutrient poor, unproductive forest type and that its low productivity is primarily the result of low soil temperature and high soil moisture.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 8
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    Productivity and nutrient cycling in taiga forest ecosystems (1983)
    Canadian Science Publishing
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    Publication Date: 1983-10-01
    Description: This paper considers the productivity and nutrient cycling in examples of the major forest types in interior Alaska. These ecosystem properties are examined from the standpoint of the control exerted over them by soil temperature and forest-floor chemistry. We conclude that black spruce Piceamariana (Mill.) B.S.P. occupies the coldest, wettest sites which support tree growth in interior Alaska. Average seasonal heat sums (1132 ± 32 degree days (DD)) for all other forest types were significantly higher than those encountered for black spruce (640 ± 40 DD). In addition, black spruce ecosystems display the highest average seasonal forest-floor and mineral-soil moisture contents. Forest-floor chemistry interacts with soil temperature in black spruce to produce the most decay-resistant organic matter. In black spruce the material is characterized by the highest lignin content and widest C/N (44) and C/P (404) ratios. Across the range of forest types examined in this study, soil temperature is strongly related to net annual aboveground tree production and the annual tree requirement for N, P, K, Ca, and Mg. Forest floor C/N and C/P ratios are strongly related to annual tree N and P requirement and the C/N ratio to annual tree production. In all cases these controls act to produce, in black spruce, the smallest accumulation of tree biomass, standing crop of elements, annual production, and element requirement in aboveground tree components.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 9
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    SOIL INCUBATIONS IN POLYETHYLENE BAGS: EFFECT OF BAG THICKNESS AND TEMPERATURE ON NITROGEN TRANSFORMATIONS AND CO2 PERMEABILITY (1987)
    Canadian Science Publishing
    Details
    Publication Date: 1987-02-01
    Description: Ground, sieved forest floor material, collected from an interior Alaskan white spruce (Picea glauca (Moench.) Voss) stand was incubated in polyethylene bags of three thicknesses (0.015, 0.020 and 0.032 mm) at three temperatures (5, 15 and 25 °C) for periods of up to 28 d. Temperature and length of incubation proved to be more important factors affecting nitrogen mineralization than thickness of bag over the range of thicknesses tested. Regardless of temperature and time of incubation, all thicknesses of bags remained permeable to CO2. All bag thicknesses remained impermeable to H2O loss, thus ensuring constant moisture content over the duration of the experiment. An additional experiment which utilized a urea-amendment to stimulate CO2 production indicated that, even under circumstances of high CO2 evolution, the bags remained well oxygenated. Key words: Spruce (white), soil incubation, polyethylene bags, nitrogen mineralization
    Print ISSN: 0008-4271
    Electronic ISSN: 1918-1841
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 10
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    Seasonal Nutrient Dynamics of Tundra Vegetation at Barrow, Alaska (1975)
    Taylor & Francis
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    Publication Date: 1975-01-01
    Print ISSN: 0004-0851
    Topics: Geography , Geosciences
    Published by Taylor & Francis
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