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  • 1
    Publication Date: 2002-07-01
    Description: The vertical distributions of fine roots of western hemlock (Tsuga heterophylla (Raf.) Sarg.) western redcedar (Thuja plicata Donn ex D. Don), and salal (Gaultheria shallon Pursh) were characterized in old-growth cedarhemlock forests on northern Vancouver Island. Total biomasses of cedar, hemlock, and salal roots in the forest floor and upper mineral soil were 817, 620, and 187 g·m2, respectively. Hemlock and salal fine roots were concentrated in the upper forest floor, while cedar fine roots were evenly distributed through the profile. Salal and hemlock fine root densities (g·m3) in the forest floor and mineral soil were positively correlated, as were salal and cedar root biomass distributions (g·m2). Only salal and hemlock root densities were significantly correlated with N concentrations. Hemlock root densities were negatively correlated with total N, and salal root densities were negatively correlated with total N and soluble organic N. Based on fine root densities, hemlock and salal probably compete for resources in the upper forest floor, whereas cedar accesses resources in the lower organic and mineral soil horizons. The differences in the vertical distributions of cedar, hemlock, and salal fine roots may partly explain the co-occurrence and different productivities of the three species in cedar-hemlock forests.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 2
    Publication Date: 2015-08-01
    Description: Soil disturbance from organic matter loss and soil compaction can impair site productivity, but less is known about whether these disturbances also affect forest health (defined here as the presence and severity of damaging pests and diseases, mortality, and overall vigour). We used six long-term soil productivity (LTSP) sites in the interior of British Columbia, Canada to test the effects of organic-matter removal and soil compaction on forest health, and to explore the relationship between forest health response and potential indicators of site sensitivity: mineral soil pH, base saturation, carbon to nitrogen ratio (C:N), carbon to phosphorus ratio (C:P), and calcium to aluminum ratio (Ca:Al). Visual forest health surveys were conducted on 5400 15 and 20 year old lodgepole pine (Pinus contorta Dougl. ex Loud.) trees. Soil disturbance treatments significantly affected forest health metrics, but this response typically differed among sites. Principle component analyses indicated the response of healthy trees was negatively related to soil base saturation, the response of dead or dying trees related to soil C:P, and the response of tree disease related to soil Ca:Al, pH, base saturation, and C:N. We found forest health response to soil disturbance varied among sites with relationships between response and soil chemical properties, suggesting a greater vulnerability of pine stands to disease with increasing soil acidity.
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    Electronic ISSN: 1208-6037
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  • 3
    Publication Date: 2006-01-01
    Description: Boreal mixedwood forests with varying proportions of coniferous and deciduous species are found throughout the North American continent. Maintenance of a deciduous component within boreal forests is currently favoured, as deciduous species are believed to promote faster nutrient turnover and higher nutrient availability. Results of comparisons of deciduous and coniferous forests are, however, inconsistent in supporting this generalization. We compared indices of soil nitrogen (N) availability in the forest floor and mineral soil of deciduous, mixed, and coniferous stands of boreal mixedwood forest in northwestern Alberta. Deciduous stands had higher N availability, reflected by higher pools of NH4-N and inorganic N in the forest floor. Forest floors of deciduous stands also tended to have higher concentrations of microbial N but did not have higher levels of NO3-N or higher rates of net nitrification. Mixed stands showed the highest rates of net N mineralization. Soil N availability was more closely related to litter N content than to litter decomposition rate. The variation among the forest types is likely attributable to vegetation, as topography is fairly uniform, stands do not differ in soil texture, and N-availability indices correlated directly with the proportion of deciduous trees.
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  • 4
    Publication Date: 2011-09-01
    Description: One of the assumed advantages of variable-retention (VR) harvesting over clearcut harvesting is reduced postharvest leaching losses of nitrogen. We test this assumption by synthesizing results from long-term field trials in a meta-analysis. Overall, clearcutting significantly increased soil NO3-N concentration, NO3-N as a proportion of soluble inorganic nitrogen (SIN), N concentration in leachates, N flux, nitrification rates, and pH, but not total N, NH4-N, SIN concentration, ammonification, or N mineralization rate. The proportion of soil NO3-N in deciduous forests increased immediately and returned to preharvest levels within five years; the effect was delayed in coniferous forests, but levels remained elevated for several years. Deciduous leaf litter decomposed faster and needle litter decomposed more slowly on clearcut sites than in uncut forests. Single-tree selection caused smaller changes in NO3-N than removal of groups of trees (i.e., gap creation) and led to smaller increases in NO3-N as a proportion of SIN than clearcut harvesting. High levels of retention (〉70%) were required to maintain uncut stand N-cycling characteristics. Postharvest NO3-N levels could be predicted from NO3-N availability in the uncut forests.
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  • 5
    Publication Date: 2004-04-01
    Description: We synthesize current information on input, accumulation, and decay of coarse woody debris (CWD) compared with other aboveground litter to assess the role of CWD in the nutrient cycles of northern coniferous forests. CWD contributes between 3% and 73% of aboveground litter input, but
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  • 6
    Publication Date: 2009-06-01
    Description: We explored the impacts of fertilization on soil greenhouse gas fluxes and underlying soil nutrient transformations using short-term (up to 7 months) simulated operational fertilization with urea-nitrogen or nitrogen, phosphorus, potassium, and micronutrients in lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm.), western hemlock ( Tsuga heterophylla (Raf.) Sarge.), and Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) forests in British Columbia. Urea appeared to be rapidly mineralized to ammonium, and nitrification (relative to controls) was only observed at the lodgepole pine site and represented only 0.5% of added nitrogen. All sites were small net sinks for atmospheric methane, and fertilization effects, both stimulatory and inhibitory, were short-lived. Across all sites and treatments, soils were as likely to consume as emit nitrous oxide, and among treatment replicates, rates were never significantly different from 0, with the exception of one efflux rate of 1.5 µg·m–2·h–1on the warmest day in the study. We conclude from this pilot study that in acidic, unpolluted (with regard to nitrogen deposition) upland conifer forest soils in western Canada fertilized once or infrequently with urea, ammonium, or a combination of nutrients, the dynamics of soil greenhouse-gas fluxes are generally not disturbed over the short-term, with soils remaining small sinks for atmospheric methane and neutral with regard to flux of nitrous oxide.
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  • 7
    Publication Date: 2003-11-01
    Description: Possible mitigation of nitrate losses associated with clearcuts through harvesting smaller gaps was tested in a high-elevation forest of Engelmann spruce (Picea engelmannii Parry ex Engelm.) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.). We measured concentrations of ammonium and nitrate after 6-week buried bag incubations of forest floor and mineral soil samples in replicated plots of uncut forest and gaps of 10, 1.0, and 0.1 ha and single-tree removal for 7 years after harvest. Nitrate concentrations in forest floor and mineral soil were elevated 37 years after harvesting in gaps of 0.1 ha and larger. Removal of the same proportion of trees as single trees did not result in increased nitrate concentrations, suggesting that nitrate losses could be reduced by harvesting single trees rather than creating gaps. Greater N availability was not associated with faster rates of decomposition of litter and forest floor, which were similar in gaps of all sizes (010 ha). Reciprocal transplant of forest floor and soil from the 10-ha gaps and the uncut forests indicated that changes in the nature of the forest floor or soil following harvest had a greater influence on nitrate concentrations than the changes in environmental conditions in the gaps.
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  • 8
    Publication Date: 1999-10-01
    Description: The contribution of coarse woody debris to C, N, and P cycles was assessed in forests of lodgepole pine (Pinus contorta Dougl. ex Loud.), white spruce (Picea glauca (Moench Voss), and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) - Engelmann spruce (Picea engelmannii Parry ex Engelm.) in southwestern Alberta. Mass loss and changes in C, N, and P concentrations in decomposing log segments were measured for 14 years. Litter input was measured during 10 years for coarse woody debris, 1 year for ground vegetation, and 5 years for other aboveground litter types. Release of C, N and P from decomposing litter were simulated for a period of 40 years. After 14 years, log segments of pine, spruce, and fir had lost on average 71, 38, and 40%, respectively, of their dry mass. The N content of the pine logs increased, spruce changed little, and fir lost N. Phosphorus accumulated in all logs. The greatest imports of N and P occurred at the pine sites and fir sites, respectively, where these nutrients were the least available, indicating that wood decay organisms may compete with vegetation for limiting nutrients in these forests. Coarse woody debris comprised 3-24% of aboveground litter and contributed less than 5% of the N and P released. Coarse woody debris does not appear to make a significant contribution to N and P cycling in these forests.
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  • 9
    Publication Date: 2017-05-01
    Description: In a changing climate, understanding how soil hydrology impacts greenhouse gas dynamics will be important for the future management of the soils in the forests on the Canadian Pacific west coast. In a laboratory study, the impact of soil hydrology on potential net methane (CH4) exchange rates and the abundance of methanotrophs (CH4oxidation) and methanogens (CH4production) in upland and water-saturated wet soils were investigated. CH4oxidation and production rates were highest in the wet soils, which corresponded to higher numbers of methanotrophs and methanogens, indicating a link between the microbial abundance and CH4exchange rates. Also, CH4production was induced in the upland soils, indicating the presence of methanogens. The optimum soil moisture content for CH4oxidation was highest in upland soils and the wet soils sustained higher CH4oxidation rates over a broader range of soil moisture. These results underline the importance of the soil hydrological controls of CH4oxidation in contrasting soils and forest types, which deserves further attention in field-based studies.
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  • 10
    Publication Date: 2005-12-01
    Description: A factorial thinning and fertilization experiment was established in central British Columbia in a 36-year-old high-density fire-origin lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) stand to examine the effects of density, nutrition, and their interaction on tree and stand growth, foliage biomass per hectare, and growth efficiency. Volume growth was increased from 2 to 7 m3·ha1·year1 when fertilizer was applied without thinning and to 5 m3·ha1·year1 when fertilizer was applied with thinning. Thinning increased tree-level foliage biomass and growth efficiency by concentrating limited resources onto fewer trees, resulting in increased tree-level volume growth. Stand-level volume growth was reduced by thinning because of the large reduction in stocking. However, by year 4, stand-level volume growth was the same on control and thinned plots, suggesting that thinned trees have already recaptured the site potential. Fertilization increased both tree-level and stand-level productivity through increases in resource availability per tree and per hectare. This resulted in increased foliage biomass and growth efficiency at the tree and stand level. The combination of thinning and fertilization resulted in the greatest tree-level growth because of increased tree-level foliage biomass and growth efficiency. Boron appears to be the most limiting element followed by sulfur and nitrogen.
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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