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  • 1
    Electronic Resource
    Electronic Resource
    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 1-1 
    ISSN: 0950-5636
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  • 2
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 187-187 
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  • 3
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 192-194 
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  • 4
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 214-215 
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  • 5
    Electronic Resource
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 218-218 
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  • 6
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 1-2 
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  • 7
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 179-187 
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  • 8
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 176-178 
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  • 9
    Electronic Resource
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 1-2 
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  • 10
    Electronic Resource
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 1-1 
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  • 11
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 1-2 
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  • 12
    Electronic Resource
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 1-1 
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  • 13
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 220-221 
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  • 14
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 191-192 
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  • 15
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 215-216 
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  • 16
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 220-220 
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  • 17
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 169-176 
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  • 18
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 189-189 
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  • 19
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 195-204 
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  • 20
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 211-213 
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  • 21
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 218-218 
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  • 22
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 205-210 
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  • 23
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 213-214 
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  • 24
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 217-217 
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  • 25
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    Cambridge : Cambridge University Press
    Bulletin of the British Society for the History of Science 1 (1952), S. 219-219 
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  • 26
    Publication Date: 2009-02-01
    Description: Climate models project that by 2100, the northeastern US and eastern Canada will warm by approximately 3–5 °C, with increased winter precipitation. These changes will affect trees directly and also indirectly through effects on “nuisance” species, such as insect pests, pathogens, and invasive plants. We review how basic ecological principles can be used to predict nuisance species’ responses to climate change and how this is likely to impact northeastern forests. We then examine in detail the potential responses of two pest species (hemlock woolly adelgid ( Adelges tsugae Annand) and forest tent caterpillar ( Malacosoma disstria Hubner)), two pathogens (armillaria root rot ( Armillaria spp.) and beech bark disease ( Cryptococcus fagisuga Lind. + Neonectria spp.)), and two invasive plant species (glossy buckthorn ( Frangula alnus Mill.) and oriental bittersweet ( Celastrus orbiculatus Thunb.)). Several of these species are likely to have stronger or more widespread effects on forest composition and structure under the projected climate. However, uncertainty pervades our predictions because we lack adequate data on the species and because some species depend on complex, incompletely understood, unstable relationships. While targeted research will increase our confidence in making predictions, some uncertainty will always persist. Therefore, we encourage policies that allow for this uncertainty by considering a wide range of possible scenarios.
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  • 27
    Publication Date: 2009-02-01
    Description: We review twentieth century and projected twenty-first century changes in climatic and hydrologic conditions in the northeastern United States and the implications of these changes for forest ecosystems. Climate warming and increases in precipitation and associated changes in snow and hydrologic regimes have been observed over the last century, with the most pronounced changes occurring since 1970. Trends in specific climatic and hydrologic variables differ in their responses spatially (e.g., coastal vs. inland) and temporally (e.g., spring vs. summer). Trends can differ depending on the period of record analyzed, hinting at the role of decadal-scale climatic variation that is superimposed over the longer-term trend. Model predictions indicate that continued increases in temperature and precipitation across the northeastern United States can be expected over the next century. Ongoing increases in growing season length (earlier spring and later autumn) will most likely increase evapotranspiration and frequency of drought. In turn, an increase in the frequency of drought will likely increase the risk of fire and negatively impact forest productivity, maple syrup production, and the intensity of autumn foliage coloration. Climate and hydrologic changes could have profound effects on forest structure, composition, and ecological functioning in response to the changes discussed here and as described in related articles in this issue of the Journal.
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  • 28
    Publication Date: 2009-02-01
    Description: In many forest types, over half of the total stand biomass is located in the forest floor. Carbon emissions during wildland fire are directly related to biomass (fuel) consumption. Consumption of forest floor fuel varies widely and is the greatest source of uncertainty in estimating total carbon emissions during fire. We used experimental burn data (59 burns, four fuel types) and wildfire data (69 plots, four fuel types) to develop a model of forest floor fuel consumption and carbon emissions in nonpeatland standing-timber fuel types. The experimental burn and wildfire data sets were analyzed separately and combined by regression to provide fuel consumption models. Model variables differed among fuel types, but preburn fuel load, duff depth, bulk density, and Canadian Forest Fire Weather Index System components at the time of burning were common significant variables. The regression R2 values ranged from 0.206 to 0.980 (P 〈 0.001). The log–log model for all data combined explained 79.5% of the regression variation and is now being used to estimate annual carbon emissions from wildland fire. Forest floor carbon content at the wildfires ranged from 40.9% to 53.9%, and the carbon emission rate ranged from 0.29 to 2.43 kg·m–2.
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  • 29
    Publication Date: 2009-02-01
    Description: Increasing temperatures, precipitation extremes, and other anthropogenic influences (pollutant deposition, increasing carbon dioxide) will influence future forest composition and productivity in the northeastern United States and eastern Canada. This synthesis of empirical and modeling studies includes tree DNA evidence suggesting tree migrations since the last glaciation were much slower, at least under postglacial conditions, than is needed to keep up with current and future climate warming. Exceedances of US and Canadian ozone air quality standards are apparent and offset CO2-induced gains in biomass and predispose trees to other stresses. The deposition of nitrogen and sulfate in the northeastern United States changes forest nutrient availability and retention, reduces reproductive success and frost hardiness, causes physical damage to leaf surfaces, and alters performance of forest pests and diseases. These interacting stresses may increase future tree declines and ecosystem disturbances during transition to a warmer climate. Recent modeling work predicts warmer climates will increase suitable habitat (not necessarily actual distribution) for most tree species in the northeastern United States. Species whose habitat is declining in the northeastern United States currently occur in Canadian forests and may expand northward with warming. Paleoecological studies suggest local factors may interact with, even overwhelm, climatic effects, causing lags and thresholds leading to sudden large shifts in vegetation.
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  • 30
    Publication Date: 2010-07-01
    Description: A synthesis was carried out to examine Alaska’s boreal forest fire regime. During the 2000s, an average of 767 000 ha·year–1 burned, 50% higher than in any previous decade since the 1940s. Over the past 60 years, there was a decrease in the number of lightning-ignited fires, an increase in extreme lightning-ignited fire events, an increase in human-ignited fires, and a decrease in the number of extreme human-ignited fire events. The fraction of area burned from human-ignited fires fell from 26% for the 1950s and 1960s to 5% for the 1990s and 2000s, a result from the change in fire policy that gave the highest suppression priorities to fire events that occurred near human settlements. The amount of area burned during late-season fires increased over the past two decades. Deeper burning of surface organic layers in black spruce ( Picea mariana (Mill.) BSP) forests occurred during late-growing-season fires and on more well-drained sites. These trends all point to black spruce forests becoming increasingly vulnerable to the combined changes of key characteristics of Alaska’s fire regime, except on poorly drained sites, which are resistant to deep burning. The implications of these fire regime changes to the vulnerability and resilience of Alaska’s boreal forests and land and fire management are discussed.
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  • 31
    Publication Date: 2009-12-01
    Description: Methods were developed to predict the moisture content of the elevated dead fine fuel layer in gorse ( Ulex europaeus L.) shrub fuels. This layer has been observed to be important for fire development and spread in these fuels. The accuracy of the Fine Fuel Moisture Code (FFMC) of the Canadian Fire Weather Index System to predict the moisture content of this layer was evaluated. An existing model was used to determine the response time and equilibrium moisture content from field data. This response time was incorporated into a bookkeeping model, combining the FFMC and this response time–equilibrium moisture content model. The FFMC poorly predicted the elevated dead fuel moisture content in gorse fuels, and attempts to improve its accuracy through regression modelling were unsuccessful. The response time of the elevated dead fine fuel layer was very fast (38–77 min) and has important implications for fire danger rating. The bookkeeping approach was the most promising method to predict elevated dead fuel moisture content. A limitation was the inability to model fuel-level meteorology. However, this model warrants further validation and extension to other shrub fuels and could be incorporated into existing fire danger rating systems that can utilize hourly weather data.
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  • 32
    Publication Date: 2010-11-01
    Description: This study investigates geographic patterns of genetic variation in aspen (Populus tremuloides Michaux.) spring phenology with the aim of understanding adaptation of populations to climatic risk environments and the practical application of guiding seed transfer. We use a classical common garden experiment to reveal genetic differences among populations from western Canada and Minnesota, and we present a novel method to seamlessly map heat-sum requirements from remotely sensed green-up dates. Both approaches reveal similar geographic patterns: we find low heat-sum requirements in northern and high-elevation aspen populations, allowing them to take full advantage of a short growing season. High heat-sum requirements were found in populations from the central boreal plains of Saskatchewan and Alberta, and populations from Minnesota exhibit moderately low heat-sum requirements for budbreak. Analysis of corresponding climate normal data shows that late budbreak is strongly associated with the driest winter and spring environments, which suggests selection pressures for late budbreak due to both frost and drought risks in early spring. We therefore caution against long-distance seed transfer of Minnesota provenances to the boreal plains of Alberta and Saskatchewan. Although such transfers have been shown to increase tree growth in short-term field tests, this planting material may be susceptible to exceptional spring droughts.
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  • 33
    Publication Date: 2009-04-01
    Description: Tree species is a key factor in shaping epiphytic lichen communities. In managed forests, tree species composition is mainly controlled by forest management, with important consequences on lichen diversity. The main aim of this work was to evaluate the differences at tree level in macrolichen richness and composition between Abies alba Mill. and Fagus sylvatica L. in a temperate mixed forest in northern Italy, in addition to evaluating two different proportions of the two species at the stand level. Abies alba and F. sylvatica host lichen communities including several rare and sensitive species. Our findings indicate that both tree species were important for lichen diversity, since they hosted different communities. However, F. sylvatica proved to be a more favourable hosting tree for several rare and sensitive species. Species associated with A. alba were mainly acidophytic lichens, while those associated with F. sylvatica were foliose hygrophytic lichens, mainly establishing over bryophytes. The frequency of the flagship species Lobaria pulmonaria (L.) Hoffm. was a valuable predictor of cyanolichen richness and was useful in identifying sites hosting lichen communities that are potentially more sensitive to thinning and human disturbance. The results support the relevance of mixed A. alba – F. sylvatica formations among European habitats worthy of conservation.
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  • 34
    Publication Date: 2010-12-01
    Description: There is increasing recognition that forestry provides a low cost and robust means of climate change abatement through carbon sequestration and substitution. However, current understanding of forest ecosystem carbon exchange and forest–atmosphere interactions are often inadequately characterized by existing empirical growth models with resulting poor representation for regional extrapolations. In this paper, we describe the parameterisation and independent validation, against both eddy covariance and forest growth experimental data, of a process-oriented model 3PGN to provide assessments of carbon sequestration of Sitka spruce (Picea sitchensis (Bong.) Carrière) plantations across Scotland. In comparison with eddy covariance measurements, the model predicted all of the major annual carbon fluxes, i.e., gross primary production (PG), net ecosystem production (PE), and ecosystem respiration (RE), with biases lower than 10%. At a monthly time step, only PG and PE were accurately estimated, whereas RE was not. At longer time scales (i.e., several decades), the model reliably represented the major patterns of the carbon balance. Soil type was identified as the important factor influencing site productivity; fertilization practices did not alter long-term site nutritional status. The analyses also highlighted the potential impact of carbon loss from carbon-rich soils, which can result in differences between optimal rotation length for carbon sequestration and for timber production.
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  • 35
    Publication Date: 2010-10-01
    Description: Understanding of the natural factors that lead to complex changes in forest ecosystems is limited. Worldwide, there are only a few forests as pristine and isolated as the Sierra de La Laguna in the southernmost range of the arid Baja California, Mexico. Its outstanding trait as a model system is that anthropogenic stressors are notably absent, which facilitates the study of natural ecological processes of the forest because separating human-induced ecological changes from natural ones is not a simple matter. In this study, we sampled sites and defined vegetation units on the basis of dominance of the canopy by the main tree species. We identified three forest types: the pine and encino forests that occupy the higher areas and the roble forest at lower elevations. For each living tree in the sampling plots, we measured height, canopy coverage per tree, diameter at breast height, as well as the amount of deadwood, leaf litter, and abundance of young trees. A succesional competition occurs between Pinus and Quercus sensu lato; we conclude that the encino forest represents a climax condition, the pine type represents an early succesional stage, and the roble forest type is a simple climax community.
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  • 36
    Publication Date: 2010-04-01
    Description: Forest structure, as measured by the physical arrangement of trees and their crowns, is a fundamental attribute of forest ecosystems that changes as forests progress through suc;cessional stages. We examined whether LiDAR data could be used to directly assess the successional stage of forests by determining the degree to which the LiDAR data would show the same relative ranking of structural development among sites as would traditional field measurements. We sampled 94 primary and secondary sites (19–93, 223–350, and 600 years old) from three conifer forest zones in western Washington state, USA, in the field and with small-footprint, discrete return LiDAR. Seven sets of LiDAR metrics were tested to measure canopy structure. Ordinations using the of LiDAR 95th percentile height, rumple, and canopy density metrics had the strongest correlations with ordinations using two sets of field metrics (Procrustes R = 0.72 and 0.78) and a combined set of LiDAR and field metrics (Procrustes R = 0.95). These results suggest that LiDAR can accurately characterize forest successional stage where field measurements are not available. This has important implications for enabling basic and applied studies of forest structure at stand to landscape scales.
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  • 37
    Publication Date: 2010-02-01
    Description: Sustainable forest management requires timely, detailed forest inventory data across large areas, which is difficult to obtain via traditional forest inventory techniques. This study evaluated k-nearest neighbor imputation models incorporating LiDAR data to predict tree-level inventory data (individual tree height, diameter at breast height, and species) across a 12 100 ha study area in northeastern Oregon, USA. The primary objective was to provide spatially explicit data to parameterize the Forest Vegetation Simulator, a tree-level forest growth model. The final imputation model utilized LiDAR-derived height measurements and topographic variables to spatially predict tree-level forest inventory data. When compared with an independent data set, the accuracy of forest inventory metrics was high; the root mean square difference of imputed basal area and stem volume estimates were 5 m2·ha–1 and 16 m3·ha–1, respectively. However, the error of imputed forest inventory metrics incorporating small trees (e.g., quadratic mean diameter, tree density) was considerably higher. Forest Vegetation Simulator growth projections based upon imputed forest inventory data follow trends similar to growth projections based upon independent inventory data. This study represents a significant improvement in our capabilities to predict detailed, tree-level forest inventory data across large areas, which could ultimately lead to more informed forest management practices and policies.
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  • 38
    Publication Date: 2010-10-01
    Description: Over the last decades, continuous signs of sugar maple ( Acer saccharum Marsh.) dieback in stands of northeastern North America have promoted the experimentation of corrective measures to restore sugar maple vitality. To verify the hypothesis that K–Mg antagonism may have limited the full response of sugar maple to dolomitic lime application in a previous experiment (CaMg(CO3)2, 12% Mg), two Ca fertilizers (CaCO3 and CaSO4·2H2O), having negligible Mg content, were applied at rates of 1, 2, and 4 t Ca·ha–1 on sugar maple trees adjacent to the limed area. After 3 years, most of the foliar nutrient concentrations of treated trees were improved, particularly Ca, for both Ca fertilizers, in line with published ranges for healthy sugar maple trees, except for Mg. Moreover, no persistent nutrient antagonism was observed. The crown dieback rate of treated sugar maple was ≤5.8% after 3 years, while it reached 12% for the controls. Also, relative basal area growth showed that both Ca sources can improve growth rate. Growth response following Ca treatments was, however, lower than for the former lime experiment after the same period of time. In this context, our results suggest that Mg nutrition could be more important for sugar maple in this ecosystem than initially thought.
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  • 39
    Publication Date: 2010-09-01
    Description: Soil compaction often limits conifer regeneration on sites degraded by landings and roads, but inadequate understanding of the relationship between compaction and tree growth could lead to inappropriate soil conservation and rehabilitation efforts. We tested liquid and plastic limits, oxidizable organic matter, total carbon, particle size distribution, and iron and aluminum oxides on soil samples collected from five forest experiments in interior British Columbia. These data were used to estimate soil maximum bulk density (MBD) and relative bulk density (RBD); our objective was to relate RBD to tree growth. Height of interior Douglas-fir ( Pseudotsuga menziesii var. glauca (Bessin) Franco) was limited when RBD was 〉0.72. For lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) and hybrid white spruce ( Picea glauca (Moench) Voss × Picea engelmannii Parry ex Engelm.), RBDs of 0.60–0.68 corresponded to maximum height, whereas RBDs of 0.78–0.87 appeared to limit height growth. The presence of surface organic material mitigated compaction and was often associated with lower RBD. Our results illustrate the usefulness of RBD to assess compaction and suggest that soil rehabilitation should be considered on disturbed sites where soil RBD is 〉0.80.
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  • 40
    Publication Date: 2009-04-01
    Description: Despite the availability of several protocols for the extraction of chlorophylls and carotenoids from foliage of forest trees, information regarding their respective extraction efficiencies is scarce. We compared the efficiencies of acetone, ethanol, dimethyl sulfoxide (DMSO), and N, N-dimethylformamide (DMF) over a range of incubation times for the extraction of chlorophylls and carotenoids using small amounts of unmacerated tissue. Of the 11 species studied, comparable amounts of chlorophyll were extracted by all four solvents from three species and by ethanol and DMF from nine species. In four species, acetone, ethanol, and DMF extracted comparable chlorophyll amounts, while in another two species comparable amounts were extracted by ethanol, DMSO, and DMF. In one species, ethanol extracted significantly greater amounts of chlorophyll compared with all other solvents. The brown coloration of DMSO extracts for some species compromised the calculations of chlorophylls and carotenoids, making DMSO a poor choice. Overall, extraction efficiencies of ethanol and DMF were comparable for analyzing chlorophyll concentrations. However, because DMF is more toxic than ethanol, we recommend ethanol as the better option of these two for chlorophyll extractions. On the other hand, DMF is the most efficient solvent among the four tested for the extraction of carotenoids from these species. The results presented will facilitate the design of multispecies local- and regional-scale ecological studies to evaluate forest health. Additionally, they will enable reliable comparisons of results from multiple laboratories and (or) studies that used different solvents and help validate chlorophyll estimates obtained by remote sensing.
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  • 41
    Publication Date: 2010-12-01
    Description: A novel “varying-centroid” method is presented for predicting whole-tree, aboveground stem volume (i.e., bole plus branch volume) to bole volume ratios from changes in the centroid of tree bole volume associated with branching of the bole. The method was derived from a simple fractal-like tree model based on a conceptualization of tree branching architecture by Leonardo da Vinci. The method recognizes that the centroid of bole volume (the point at which one half of bole volume is above and one half is below) is always lower than the centroid of whole-tree volume and that shifts in the centroid of bole volume should be predictably related to the size of a tree’s crown. The method assumes that branch-displaced bole volume profiles can be compared with reference bole profiles that are not significantly influenced by branching, at the centroid of bole volume, and that the magnitude of bole centroid displacement predicts the branch volume necessary to cause it. When the method was applied to hardwood trees representing diverse species, sizes, and stand conditions across Michigan, the centroid of bole volume was found to vary predictably with measurable tree crown attributes and bole plus branch wood to bole wood volume ratios were generally predicted within 10% of the true value using the new method.
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  • 42
    Publication Date: 2010-11-01
    Description: Because of the importance of seed surface area, volume, and fill to hydraulic and thermal exchanges with the soil, mechanistic simulation of seed physiological processes associated with tree migration dynamics and the spread of invasive species require accurate equations to model seed shape. Seed dimensions have previously been described with measurements of the three principal axes, assuming an implied single ellipsoid. However, conifer seeds often exhibit anisotropy that results from bilaterally symmetric pairing on cone scales. We developed a method for measuring and modeling conifer seed shape as a sum of 2jpartial ellipsoids fused at their equators, where j = 0, …, 3. We demonstrate the use of the methods in the study of shape characteristics of ponderosa pine (Pinus ponderosa P.& C. Lawson) seeds from four families in Montana and among commercial lots of ponderosa pine, lodgepole pine (Pinus contorta Dougl. ex Loud.), and Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco). The shapes of 92%, 73%, and 47% of seeds in commercial lots studied had eight unique ellipsoids when classified with 1%, 5%, and 10% difference classification rules, respectively. Ponderosa pine seeds with longer minor axes were less well filled with storage reserves. Three-dimensional surface areas of lodgepole and ponderosa pine were approximately 2 and 3.4 times larger, respectively, than previously reported one-sided surface areas.
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  • 43
    Publication Date: 2010-09-01
    Description: Small-scale disturbance is a significant process in all major forest biomes. Some silvicultural practices, particularly group selection harvesting, intend to emulate natural small-scale disturbance by harvesting small clearcuts in the continuous forest. We conducted a meta-analysis on the effects of small-scale harvesting on North American breeding forest birds. We extracted species richness and relative abundance of several functional bird groups and guilds from published studies and compared them between gap-dominated and unlogged forest as a function of forest type and the size and age of the gap. The abundance of many bird groups was higher in the gap-dominated than in the continuous forest. Species preferring interior parts of the forest had the most negative association with the presence of gaps but this relationship was not statistically significant. Abundances of many bird groups increased with increasing gap size, while its effect on abundance of some bird groups disappeared quickly. Our review suggests that silvicultural practices that bring about small gaps do not negatively affect the abundances of most forest birds and often even enhance it. However, more studies are needed to examine optimal size and abundance of gaps in a forest and whether emulated small-scale disturbance effectively mimics natural processes.
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  • 44
    Publication Date: 2009-12-01
    Description: In this study we examined various measures, including the concordance correlation (CC) coefficient, for determining the goodness of fit of forest models estimated by nonlinear mixed-model (NLMM) methods. Based on the volume–age data for black spruce, we analyzed the use of CC and other traditional goodness-of-fit measures such as coefficient of determination (R2), mean bias, percent bias, root mean square error, and graphic techniques on both the population and subject-specific levels within the NLMM framework. We also examined the relationship between goodness-of-fit measures and the number of observations per subject. We found that the standard overall goodness-of-fit measures commonly reported on combined data from different subjects were generally insufficient in determining the goodness of fitted models. We recommend that CC and other selected goodness-of-fit measures be calculated for individual subjects, and that the frequency distributions of the calculated values be examined and used as the principal criteria for determining the goodness of fit of forest models estimated by NLMM methods and for comparing alternative models and covariance structures. We also emphasized the importance of using pertinent graphic techniques to assess the appropriateness of NLMMs, especially at the subject-specific level, wherein lies the main interest of NLMMs.
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  • 45
    Publication Date: 2009-06-01
    Description: While piñon woodlands cover much of arid North America, surprisingly little is known about the role of fire in maintaining piñon forest structure and species composition. The lack of region-specific fire regime data for piñon–juniper woodlands presents a roadblock to managers striving to implement process-based management. This study characterized piñon–juniper fire regimes and forest stand dynamics in Big Bend National Park (BIBE) and the Davis Mountains Preserve of the Nature Conservancy (DMTNC) in west Texas. Mean fire return intervals were 36.5 and 11.2 years for BIBE and DMTNC, respectively. Point fire return intervals were 150 years at BIBE and 75 years at DMTNC. Tree regeneration in west Texas piñon–juniper woodlands occurred historically during favorable climatic conditions following fire years. The presence of multiple fire scars on our fire-scar samples and the multicohort stands of piñon suggested that low intensity fires were common. This study represents one of the few fire-scar-based fire regime studies for piñon–juniper woodlands. Our results differ from other studies in less topographically dissected landscapes that have identified stand-replacing fire as the dominant fire regime for piñon–juniper woodlands. This suggests that mixed-severity fire regimes are typical across southwestern piñon forests, and that topography is an important influence on fire frequency and intensity.
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  • 46
    Publication Date: 2009-07-01
    Description: Data on the impact of forest management practices on ectomycorrhizal community structure remains fragmentary and mainly originates from studies in northern coniferous forests. This study focuses on a comparison of ectomycorrhizal communities between canopy gaps and closed canopy areas within natural and managed beech-dominated forests at four locations in Europe. We used high resolution rDNA techniques to identify ectomycorrhiza-forming fungi and attempted to extract potential stand-, gap-, soil-, and selected environmentally derived variables by applying multivariate analysis and ordination for pooling of ecological groups of ectomycorrhiza. A significant reduction of diversity indices, ectomycorrhizal and fine root dynamics, in gaps in comparison with closed canopy stands indicates an effect of forest management practice and the high importance of maintaining and protecting natural forest areas for conservation of soil biodiversity and forest genetic resources. The ordination analysis revealed three groups of ectomycorrhiza correlated with changing environmental conditions. The litter and soil pH, number of beech seedlings, and presence of a gap had a pronounced effect on the ectomycorrhizal community. Combined analysis of ectomycorrhiza and environmental factors using correspondence analysis provided an insight into the ecological preferences of the analysed species and confirmed that environmental factors drive ectomycorrhizal community changes.
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  • 47
    Publication Date: 2009-10-01
    Description: Relationships between stand growth and structural diversity were examined in spruce-dominated forests in New Brunswick, Canada. Net growth, survivor growth, mortality, and recruitment represented stand growth, and tree species, size, and height diversity indices were used to describe structural diversity. Mixed-effects second-order polynomial regressions were employed for statistical analysis. Results showed stand structural diversity had a significant positive effect on net growth and survivor growth by volume but not on mortality and recruitment. Among the tested diversity indices, the integrated diversity of tree species and height contributed most to stand net growth and survivor growth. Structural diversity showed increasing trends throughout the developmental stages from young, immature, mature, and overmature forest stands. This relationship between stand growth and structural diversity may be due to stands featuring high structural diversity that enhances niche complementarities of resource use because trees exist within different horizontal and vertical layers, and strong competition resulted from size differences among trees. It is recommended to include effects of species and structural diversity in forest growth modeling initiatives. Moreover, uneven-aged stand management in conjunction with selective or partial cutting to maintain high structural diversity is also recommended to maintain biodiversity and rapid growth in spruce-dominated forests.
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  • 48
    Publication Date: 2009-08-01
    Description: Intraannual features or anomalies in the tree rings of woody species may provided useful information for ecological and climatological studies. The frequency of intraannual density fluctuations (IADFs), differences in IADFs according to the cambial age, changes in IADFs in the last century, and relationships of IADFs to radial growth and climate were analyzed in five stands of Pinus pinaster subsp. mesogeensis (Fieschi & Gaussen) Silba in east-central Spain. Standard dendrochronological techniques were used. Two cores were extracted 1.30 m above ground level from 15 dominant and codominant trees at each sampling site. The data were analyzed by analysis of variance, Pearson’s correlation, and logistic regression. Results showed that (i) the mean frequency of IADFs was higher in younger than older trees; (ii) the frequency of IADFs increased from the 1940s to the present; (iii) radial growth was negatively correlated with the presence of IADFs; and (iv) density fluctuations may be predicted by using a logistic model, with monthly rainfall and temperature as independent variables. Studies of intraannual features or anomalies in radial growth may be useful for ecological and climatological applications under forecasted climate change scenarios.
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  • 49
    Publication Date: 2009-11-01
    Description: As forests develop, changes in soil organic matter quantity and quality affect both nutrient dynamics and microbial community structure. Litter decomposition and nitrogen mineralization in association with soil microbial communities were compared between 45- and 135-year-old lodgepole pine ( Pinus contorta var. latifolia (Englem.)) stands in southeastern Wyoming, USA. Compared with the 45-year-old stand, the 135-year-old stand was found to have greater live-tree biomass, litter decomposition rates (264 versus 135 mg·(g litter)–1·year–1), soil nitrification rates (0.38 versus 0.19 µg NO3–·(g soil)–1 after 265 days of field incubation), and total phospholipid fatty acid (PLFA) concentrations (25 versus 9.2 nmol·(g soil)–1 at 0–5 cm depth). Canonical correspondence analysis indicated that variation of PLFA profiles within the 45-year-old stand was explained by soil pH and bulk density, whereas soil process rates explained the distributions of PLFA profiles within the 135-year-old stand. The results of these studies indicate that stand age influences live-tree biomass and soil properties that can lead to changes in litter decomposition rates and soil microbial communities in lodgepole pine forests.
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  • 50
    Publication Date: 2009-05-01
    Description: We propose a new and relatively simple modification to extend the utility of bioclimatic envelope models for land-use planning and adaptation under climate change. In our approach, the trajectory of vegetation change is set by a bioclimatic envelope model, but the rate of transition is determined by a disturbance model. We used this new approach to explore potential changes in the distribution of ecosystems in Alberta, Canada, under alternative climate and disturbance scenarios. The disturbance model slowed the rate of ecosystem transition, relative to the raw projections of the bioclimatic envelope model. But even with these transition lags in place, a northward shift of grasslands into much of the existing parkland occurred over the 50 years of our simulation. There was also a conversion of 12%–21% of Alberta’s boreal region to parkland. In addition to aspatial projections, our simulations provide testable predictions about where ecosystem changes as a result of climate change are most likely to be initially observed. We also conducted an investigation of model uncertainty that provides an indication of the robustness of our findings and identifies fruitful avenues for future research.
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  • 51
    Publication Date: 2010-04-01
    Description: A system of equations for compatible prediction of total and merchantable volumes that allows for different definitions of tree volume was developed in this study. The use of the developed system will allow the conversion and subsequent comparison of results from forest inventories using different definitions of tree volume (e.g., including or not the top material of the tree and (or) the stump, inside or outside bark). The compatibility between taper, total volume, and volume ratio equations is ensured by properly integrating the taper equation. The diameter under the bark at any height is modeled with the Demaerschalk taper equation, and the corresponding diameter over the bark is obtained by assuming that bark thickness is also modeled with Demaerschalk’s function. The set of equations that has contemporaneous cross-equation error correlation (known as nonlinear seemingly unrelated regression equations) was fit using nonlinear joint generalized least squares regression. The predictive ability was evaluated using an independent data set. The system is consistent and performs well when applied to maritime pine ( Pinus pinaster Ait.) trees in Portugal, showing better performance than do other total volume equations for maritime pine used in the latest Portuguese national forest inventories.
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  • 52
    Publication Date: 2010-12-01
    Description: Loblolly pine (Pinus taeda L.) is a major plantation species grown in the southern United States, producing wood having a multitude of uses including pulp and lumber production. Specific gravity (SG) is an important property used to measure the quality of wood produced, and it varies regionally and within the tree with height and radius. SG at different height levels was measured from 407 trees representing 135 plantations across the natural range of loblolly pine. A three-segment quadratic model and a semiparametric model were proposed to explain the vertical and regional variations in SG. Both models were in agreement that a stem can be divided into three segments based on the vertical variation in SG. Based on the fitted models, the mean trend in SG of trees from the southern Atlantic Coastal Plain and Gulf Coastal Plain was observed to be higher than in other physiographical regions (Upper Coastal Plain, Hilly Coastal Plain, northern Atlantic Coastal Plain, and Piedmont). Maps showing the regional variation in disk SG at a specified height were also developed. Maps indicated that the stands in the southern Atlantic Coastal Plain and Gulf Coastal Plain have the highest SG at a given height level.
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  • 53
    Publication Date: 2010-07-01
    Description: Subsistence harvesting and wild food production by Athabascan peoples is part of an integrated social–ecological system of interior Alaska. We describe effects of recent trends and future climate change projections on the boreal ecosystem of interior Alaska and relate changes in ecosystem services to Athabascan subsistence. We focus primarily on moose, a keystone terrestrial subsistence resource of villages in that region. Although recent climate change has affected the boreal forest, moose, and Athabascan moose harvesting, a high dependence by village households on moose persists. An historical account of 20th century socioeconomic changes demonstrates that the vulnerability of Athabascan subsistence systems to climatic change has in some respects increased while at the same time has improved aspects of village resilience. In the face of future climate and socioeconomic changes, communities have limited but potentially effective mitigation and adaptation opportunities. The extent to which residents can realize those opportunities depends on the responsiveness of formal and informal institutions to local needs. For example, increases in Alaska’s urban population coupled with climate-induced habitat shifts may increase hunting conflicts in low-moose years. This problem could be mitigated through adaptive co-management strategies that project future moose densities and redirect urban hunters to areas of lower conflict.
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  • 54
    Publication Date: 2010-12-01
    Description: Forest management planners usually treat potential fire loss estimates as exogenous parameters in their timber production planning processes. When they do so, they do not account for the fact that forest access road construction, timber harvesting, and silvicultural activities can alter a landscape’s vegetation or fuel composition, and they ignore the possibility that such activities may influence future fire losses. We develop an integrated fire and forest management planning methodology that accounts for and exploits such interactions. Our methodology is based on fire occurrence, suppression, and spread models, a fire protection value model that identifies crucial stands, the harvesting of which can have a significant influence on the spread of fires across the landscape, and a spatially explicit timber harvest scheduling model. We illustrate its use by applying it to a forest management unit in the boreal forest region of the province of Alberta in western Canada. We found that for our study area, integrated fire – forest management planning based on our methodology could result in an 8.1% increase in net present value when compared with traditional planning in which fire loss is treated as an exogenous factor.
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  • 55
    Publication Date: 2009-11-01
    Description: Soil compaction caused by forest machinery changes the basic conditions for root propagation below skid trails. In consequence, lower fine-root densities have to be expected under wheel tracks compared with other skid trail strata that experience no direct traffic. Explorative data analysis of fine-root densities below a skid trail revealed that the fundamental assumptions for linear modelling were violated. Using a generalized linear model following a Poisson distribution with a log link function for the predictor variables together with an exponential covariance function to cope with spatial autocorrelation, the formal model criteria were met. In contrast to the linear models, generalized additive models provide flexible surface estimators that enable us to model continuous response surfaces. In addition, generalized additive models allow for the calculation of confidence intervals for the estimated density surface and for the use of inferential statistics, such as comparisons between depth gradients of fine rooting at distinct transect locations or depth layers. These model characteristics improve the possibility to recognize differences and to evaluate fine-root disturbances below skid trails without integrating uncertain strata information. They also enhance the options for determining the duration of time that is necessary to restore the rooting capacity on formerly compacted soils.
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  • 56
    Publication Date: 2010-10-01
    Description: White poplar ( Populus alba L.) is a native species in Europe, but its growth potential is largely unknown. The general objectives of our study were to determine the impact of contrasted environments across Europe and the influence of parental characteristics on the growth potential of an intraspecific F1 white poplar family originating from a cross between parents native from the south and the north of Italy. The growth of the family was monitored at three sites located in the north of Italy, in central France, and in the southern United Kingdom. The family showed a highly superior productivity in Italy. A pronounced plasticity among sites was found for the male parent only. Indeed, for this parent, the highest growth was observed in northern Italy, its area of origin. A positive heterosis was observed mainly in France and in the United Kingdom. Broad-sense heritability values were moderate in most cases. However, the growth of the family was in some cases superior to the one of several other interspecific hybrid families growing under the same conditions, underlying the poorly known growth potential of such intraspecific hybrids for biomass production under European conditions.
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  • 57
    Publication Date: 2009-11-01
    Description: The impact of temperature on the linear viscoelastic region, which is characterized by critical strain, of Chinese fir ( Cunninghamia lanceolata (Lamb.) Hook.) was investigated at various temperatures between –100 and 220 °C for specimens with a moisture content of approximately 0.6%. The effect of oscillation frequency on the linear viscoelastic region under various constant temperatures was also examined. The results indicated that critical strain generally decreased with increasing temperature except at –80, –20, 40, 120, and 220 °C. These five exceptions were attributed to the occurrence of relaxation processes. With an increase in testing frequency from 1 to 20 Hz, the critical strain decreased slightly at all temperatures. It is suggested that the stored elastic energy and yield stress, which were obtained at critical strain, could be indicators to predict wood mechanical performance.
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  • 58
    Publication Date: 2010-03-01
    Description: Declines of whitebark pine ( Pinus albicaulis Engelm.) have occurred across much of the species’ range over the last 40 years due to mountain pine beetle outbreaks and white pine blister rust infection. Management efforts to stem these declines are increasing, yet the long-term success of whitebark pine depends on the species itself adapting to the modern environment. Natural regeneration will be a critical part of this process. We examined patterns in natural whitebark pine regeneration as related to the biophysical environment in sixty 0.1 ha plots in Montana, Idaho, and Oregon. Whitebark pine regeneration was present in 97% of our plots and varied widely in density from 0 to 17 000 seedlings/ha and 0 to 2680 saplings/ha. Using nonparametric correlation analysis and ordination techniques, we found whitebark pine regeneration abundance was unrelated to stand age but significantly related to several biophysical site characteristics, including positive relationships with elevation and canopy tree mortality caused by mountain pine beetle and negative relationships with moisture availability, temperature, and subalpine fir importance. Our findings indicate that whitebark pine is regenerating in many areas and that the widespread mortality from recent mountain pine beetle outbreaks may provide suitable settings for whitebark pine regeneration given sufficient seed sources.
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  • 59
    Publication Date: 2009-10-01
    Description: We evaluated whether two indices of light availability resolved differences among microsites within deeply shaded understories (
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  • 60
    Publication Date: 2009-04-01
    Description: In 1- to 2-year-old Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco var. menziesii) plantations near Cave Junction and Glendale, Oregon, sprout clumps of tanoak (Lithocarpus densiflorus (Hook. & Arn.) Rehd.) and other hardwoods were removed with herbicides in April 1983 to leave relative covers of 0%, 25%, 50%, or 100% of the nontreated cover, which averaged 15%. In 1996 (Cave Junction) and 1998 (Glendale), precommercial thinning (PCT) of Douglas-fir and cutting of nonconifer woody species were operationally applied across the four densities of tanoak. In 2005, Douglas-fir in 0% relative cover of tanoak averaged 5–8 cm larger at breast height and 3–6 m taller, and had two to four times the net stand volume of those growing in 100% relative cover. From 1999 to 2005, Douglas-fir stand growth accelerated more rapidly in tanoak relative covers of 0% and 25% than in covers of 50% and 100%. Differential development of Douglas-fir and hardwoods in relative covers of 0%, 25%, and 100%, followed by selection of crop trees via PCT, resulted in three distinct stand structures: pure stands of Douglas-fir with a single canopy layer 12–16 m tall, mixed stands with overstory Douglas-fir (12 m) and midstory hardwoods (7 m), and mixed stands with a single canopy layer (8–9 m).
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  • 61
    Publication Date: 2010-01-01
    Description: We evaluated spruce budworm ( Choristoneura fumiferana (Clem.)) outbreak effects in nine study areas (60–86 ha each) located in the boreal forest of eastern Quebec (Canada). In each area, spruce budworm outbreak effects were measured from vegetation plots, dominant canopy and understory tree age structures, retrospective analysis of aerial photographs, defoliation records, and host tree growth reductions (dendrochronology). Large-scale synchronous outbreaks were detected across the region around the years 1880, 1915, 1950, and 1980. Overall, contrarily to what was expected for a region where host species (balsam fir ( Abies balsamea (L.) Mill.), Picea spp.) content is relatively high, these spruce budworm outbreaks seemed to have a relatively minor influence on stand dynamics, with the exception of the most recent outbreak (1980). This outbreak resulted in major stand mortality in the southern part of the region and favored the establishment of extensive tracts of young even-aged stands with few residual mature trees. This very abrupt increase in outbreak severity compared with earlier outbreaks, perhaps due to climatic or random factors, suggests that historical trends in successive outbreak severity should be extrapolated very cautiously and that the study of several outbreak cycles is needed to establish a range of natural variability that can be used to develop an ecosystem forest management strategy.
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  • 62
    Publication Date: 2009-06-01
    Description: Systematic sampling is easy, efficient, and widely used, though it is not generally recognized that a systematic sample may be drawn from the population of interest with or without restrictions on randomization. The restrictions or the lack of them determine which estimators are unbiased, when using the sampling design as the basis for inference. We describe the selection of a systematic sample, with and without restriction, from populations of discrete elements and from linear and areal continuums (continuous populations). We also provide unbiased estimators for both restricted and unrestricted selection. When the population size is known at the outset, systematic sampling with unrestricted selection is most likely the best choice. Restricted selection affords estimation of attribute totals for a population when the population size — for example, the area of an areal continuum — is unknown. Ratio estimation, however, is most likely a more precise option when the selection is restricted and the population size becomes known at the end of the sampling. There is no difference between restricted and unrestricted selection if the sampling interval or grid tessellates the frame in such a way that all samples contain an equal number of measurements. Moreover, all the estimators are unbiased and identical in this situation.
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  • 63
    Publication Date: 2009-03-01
    Description: As part of a larger study to examine the operational feasibility, ecological benefits, and environmental impacts of partial-harvest logging in riparian buffers along boreal mixedwood forest streams, we determined the effects on summer stream temperatures. Three logged study reaches were compared with three reference reaches over two prelogging and two postlogging summers. Partial-harvest logging resulted in an average removal of 10%, 20%, and 28% of the basal area from riparian buffers at the three logged sites. At the two more intensively logged sites, there were small ( 0.18). There were no measurable impacts on stream temperatures at two of the three logged sites. At the most intensively logged site, daily maximum temperatures were significantly higher (∼4 °C) for about 6 weeks in the first summer after logging than in prelogging years or at the reference sites (P 〈 0.001). Temperature increases were attributed to a logging-induced temporary disruption of cool water inputs from ground disturbance in a lateral-input seep area. Our results indicate that partial-harvest logging in riparian buffers of boreal mixedwood forest streams can sustain effective canopy cover and mitigate logging-induced water temperature increases.
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  • 64
    Publication Date: 2010-03-01
    Description: Forest managers are seeking strategies to create stands that can adapt to new climatic conditions and simultaneously help mitigate increases in atmospheric CO2. Adaptation strategies often focus on enhancing resilience by maximizing forest complexity in terms of species composition and size structure, while mitigation involves sustaining carbon storage and sequestration. Altered stand age is a fundamental consequence of forest management, and stand age is a powerful predictor of ecosystem structure and function in even-aged stands. However, the relationship between stand age and either complexity or carbon storage and sequestration, especially trade-offs between the two, are not well characterized. We quantified these relationships in clearcut-origin, unmanaged pine and aspen chronosequences ranging from 130 years in northern Minnesota. Complexity generally increased with age, although compositional complexity changed more over time in aspen forests and structural complexity changed more over time in pine stands. Although individual carbon pools displayed various relationships with stand age, total carbon storage increased with age, whereas carbon sequestration, inferred from changes in storage, decreased sharply with age. These results illustrate the carbon and complexity consequences of varying forest harvest rotation length to favor younger or older forests and provide insight into trade-offs between these potentially conflicting management objectives.
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  • 65
    Publication Date: 2009-03-01
    Description: In the Finnish National Forest Inventory thousands of trees are cored every year. Based on the increment cores we assessed the progress of the radial increment in Scots pine ( Pinus sylvestris L.) and Norway spruce ( Picea abies (L.) Karst.) during the growing season. Data for 18 and 15 years were available from the southern and middle boreal zones, respectively. No major differences were found in the progress of the radial increment between either tree species or vegetation zones. In both zones, the radial increment began at approximately the same time, in late May or early June. On average, half of the annual radial increment was completed in early July, and ceased in late July or early August. However, there was large variation among years in the progress of the radial increment. On average, the radial-increment period (10%–90% of the total increment) was 41–59 days depending on tree species and region. The increment period was slightly shorter in the middle boreal zone, as increment ended 5–11 days later in the southern boreal zone. The variation of annual radial-increment indices was related to the dates of increment onset and cessation. However, increment-period length was more closely related to the differences in increment indices.
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  • 66
    Publication Date: 2009-03-01
    Description: A stochastic model to simulate the processes of initiation, diameter growth, death, and self-pruning of branches in loblolly pine ( Pinus taeda L.) trees is presented. Information on whorl formation and branch growth was obtained from destructive sampling of whorl sections from 34 trees growing under 10 different initial spacings. Three different components were modeled and hierarchically connected: whorl, branches, and knots. For each new growing season, whorls and branches are assigned stochastically along and around the stem. Thereafter, branch diameter growth is predicted as a function of relative location within the live crown and stem growth. The branch model was linked to an individual-tree growth model, PTAEDA3.1, to simulate the dynamics of first-order branches arising from the main stem. Information on (i) vertical trend of branch diameter along and around the stem, (ii) volume of knots (live and dead portions), and (iii) spatial location, size, and type (live and dead) of knots can be obtained. In its current stage, the framework allows evaluation of the quality of trees and sawlogs produced, inclusion of additional wood properties, and linkage with industrial conversion processes (e.g., sawing simulation). However, further research is needed to obtain data on branch dynamics to validate the overall performance of the model and improve developed submodels.
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  • 67
    Publication Date: 2009-01-01
    Description: Variable retention harvest systems are encouraged to promote complexity in managed forests, and aggregated retention has been suggested as a means of reducing moisture stress in residual trees. We studied the impacts of within-aggregate position on growth and foliar physiology to better understand the spatial dynamics of residual-tree responses to aggregated retention harvests in even-aged Pinus resinosa Ait. stands. Distance from edge and edge aspect influenced radial growth, volume increment, and growth efficiency, but only edge aspect affected foliar nitrogen content. Spatial variables had no significant relationships with foliar carbon isotope ratios (δ13C). Increases in radial growth, volume increment, and growth efficiency following harvesting were greatest near edges and in the northeastern quadrants of aggregates that received mechanical understory release treatments, and lowest in the southeastern quadrant of aggregates and near aggregate centers. Foliar nitrogen content was highest in the southwestern quadrants of aggregates that received understory release treatments, and lowest in the northwestern quadrants of aggregates. Our results suggest spatial relationships are important determinants of residual-tree responses to aggregated retention harvests.
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  • 68
    Publication Date: 2009-08-01
    Description: Red maple ( Acer rubrum L.) is becoming increasingly dominant in forest stands throughout the eastern United States. To investigate the reasons for the increase, we examined the development of red maple and oak ( Quercus spp.) seedlings and stump sprouts following the harvest of oak-dominated stands. Within 7 years after harvest, red maple seedlings were present in far greater numbers and captured more growing space than all oaks combined. Growing space occupied by red maple stump sprouts exceeded oak sprouts by a ratio of 3.5:1. Through stump sprouts alone, red maple fully recaptured the amount of growing space it had previously occupied in the overstory 7 years after harvest. Results from similar but older stands show that red maple dominance is sustained into the third decade of stand development. Red maple surpassed all oaks combined in rapid site capture through both seed-origin and sprout-origin regeneration. Red maple’s superior ability to regenerate by sprouts is particularly favored by timber harvesting following a history of management and disturbance regimes that permit the accumulation of suppressed small-diameter red maple stems. Among the events and processes that promote stand conversion, timber harvesting may be the major proximal cause of the widespread, increasing dominance of red maple.
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  • 69
    Publication Date: 2009-12-01
    Description: Forest business clusters offer a unique opportunity to improve competitiveness of the forest products sector and stimulate economic development in rural areas. This study utilized georeferenced data on the location of primary wood products manufacturers in the US South to examine spatial clustering within this industry. Independent spatial analyses, F-hat and L-hat, and a χ2 statistic provided evidence of regional clustering. A count data model was used to determine location preference of primary wood-using mills and identify factors promoting industry clustering. It was determined that access to a labor pool, low cost of primary inputs, presence of related industries, adequate transportation infrastructure, and low land values positively influenced clustering among primary wood-using mills. A marginal analysis indicated that counties with adequate transportation infrastructure and presence of related industries were most likely to attract new primary forest products manufacturers. These two factors increased the predicted number of sawmills by 26.83% and 22.65%, respectively. Increases in prices of logs and energy can deter the spatial aggregation of wood-using mills. Results provide evidence that public investments in infrastructure can have an important role in attracting wood products industry firms.
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  • 70
    Publication Date: 2010-09-01
    Description: An integrated forest management optimization model was developed to calculate potential spruce budworm ( Choristoneura fumiferana Clemens) effects on forest and wood product carbon (C) from 2007 to 2057 and to evaluate potential C sequestration benefits of alternative management strategies (salvage, biological insecticide application). The model was tested using simulated spruce budworm outbreaks on a 210 000 ha intensively managed forest in northwestern New Brunswick, Canada. Under a severe spruce budworm outbreak scenario from 2007 to 2020, harvest volume and forest and wood product C storage in 2027 were projected to be reduced by 1.34 Mm3, 1.48 Mt, and 0.26 Mt, respectively, compared with the levels under no defoliation. Under the same severe outbreak scenario, implementation of salvage and harvest replanning plus a biological insecticide applied aerially to 40% of susceptible forest area, reduced harvest, forest C, and wood product C impacts by 73%, 41%, and 56%, respectively. Extrapolation of these results to all of New Brunswick suggests that a future severe spruce budworm outbreak could effectively increase total provincial annual C emissions (all sources) by up to 40%, on average, over the next 20 years. This modeling approach can be used to identify to what extent insecticide application, as a forest-C-offset project, could result in additional C storage than without forest and pest management.
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  • 71
    Publication Date: 2010-05-01
    Description: Managed coniferous forest dominates much of the black-backed woodpecker’s ( Picoides arcticus Swainson) breeding range. Despite this, little is known about the fine-scale foraging behaviour of this focal species in unburned managed forest stands in the absence of insect outbreaks. To investigate the foraging substrates used in such a habitat, we employed radio-telemetry to track a total of 27 black-backed woodpeckers. During two successive summers (2005–2006), 279 foraging observations were recorded, most of which were on dying trees, snags, and downed woody debris. Individuals frequently foraged by excavation, suggesting that in the absence of insect outbreaks the black-backed woodpecker forages mainly by drilling. The majority of foraging events occurred on recently dead snags with a mean dbh (±SE) of 18.3 ± 0.4 cm. Our results suggest that in unburned boreal forest stands, substrate diameter and decay class are important predictors of suitable foraging substrates for black-backed woodpeckers. We suggest that conservation efforts aimed at maintaining this dead-wood dependent cavity nesting species within the landscape, should endeavour to maintain 100 ha patches of old-growth coniferous forest. This would ensure the continuous production of a sufficient quantity of recently dead or dying trees to meet the foraging needs of this species.
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  • 72
    Publication Date: 2009-02-01
    Description: Stand conditions influence the partitioning of biomass to stem, needle, branch, and root components. Using data from 4- to 6-year-old loblolly pine ( Pinus taeda L.) trees grown in a miniature-scale spacing trial, this study determined the effect of initial spacing on the biomass partitioning of loblolly pine. Multivariate analysis of variance procedures concluded that row and column spacing did not have a significant effect on the relative amount of biomass among tree components. Root/shoot and height/diameter ratios, however, differed across densities, indicating that allometric-based partitioning tradeoffs occurred. Results from the miniature-scale trees showed trends similar to those observed with mature-sized trees at operational spatial scales. Stem and woody roots were 70% and 14% of total mass, respectively. Since these trees were physiologically young at the time of harvest, the allocation of mass to needle continued to be a priority, accounting for 10% of the total mass. Initial planting spacing did not directly affect partitioning patterns; however, allometric ratios offered some evidence that partitioning may have changed between above- and below-ground tree components. This analysis offers insight into using principles from similarity analysis to analytically relate biomass partitioning from miniature to operational spatial scales.
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  • 73
    Publication Date: 2009-10-01
    Description: Resource managers, planners, and the public are unified in their calls for monitoring of land-use plans. Unfortunately, many monitoring initiatives fall short of their potential for several reasons: indicators are not explicitly linked to objectives, hindering feedback to planning; knowledge is not represented in a manner that facilitates learning; and monitoring priorities are driven subjectively. We describe a framework that links indicators to existing objectives, presenting knowledge as hypotheses about the probability of achieving an objective as a function of various indicator levels. Uncertainty is explicitly included in the models. The framework can be used for management decision support and to prioritize objectives for implementation, effectiveness, and validation monitoring, and research. Monitoring priority is determined first by probability of success and uncertainty and then by the importance of an objective. We present a case study for the Babine Watershed, an area in the interior of British Columbia with high resource values and decades of controversy and ineffective monitoring. The framework sifted through existing objectives to focus effort on those most critical to monitor. By concentrating on publicly derived, regionally applicable objectives and strategies taken from existing land-use plans, the framework provided relevant results and enabled rapid feedback.
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  • 74
    Publication Date: 2009-01-01
    Description: The paper studied the short-term effects of experimental warming, nitrogen fertilization, and their combination on growth and photosynthetic performances of Picea asperata Mast. and Pinus tabulaeformis Carr. seedlings. These seedlings were subjected to two levels of temperature (ambient temperature and infrared heater warming) and two nitrogen levels (0 and 25 g N·m–2·year–1) for 6 months. Warming alone and fertilization alone significantly increased biomass accumulation and photosynthetic performances of both two species. The combination of warming and fertilization stimulated greater accumulation of stem, root, and total biomass and further increased chlorophyll content and net photosynthesis rate (A) in Pinus tabulaeformis seedlings. However, for Picea asperata seedlings, the interaction induced less increment in plant height, total biomass, chlorophyll contents, A, and the efficiency of photosystem than nitrogen treatment alone. These results implied that both climate warming and nitrogen addition were favorable for the early growth of both coniferous species; the interaction of these two factors caused adding or multiplying single-factor effects in the case of Pinus tabulaeformis seedlings but dampening them in the case of Picea asperata seedlings, at least in short time.
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  • 75
    Publication Date: 2010-11-01
    Description: New sensor-based approaches for assessing the quantity, quality, and value of timber are being developed with the goals of improving the accuracy and economics of forest measurements. One new approach is based on terrestrial laser scanning (TLS). Thirty-three plots in six radiata pine (Pinus radiata D. Don) stands were scanned using TLS. Tree locations were automatically detected. Stem profiles were measured using three methods: (i) TLS scans, (ii) Atlas Cruiser inventory procedures, and (iii) manual measurement after harvesting. Stems were optimally bucked based on log specifications and prices for Australian markets. Tree values and log product yields were estimated for the TLS data and compared with estimates based on Cruiser and actual manual measurements of stem profiles. TLS volume and value recovery were within 8% and 7%, respectively, of actual harvester recovery for five of the six stands in which it was used. Cruiser volume and value estimates were both within 4% of actual harvester recovery. Plot preparation procedures, tree characteristics, and taper equations used to model diameters on hidden stem sections affected the accuracy of automated stem detection and profile measurements for the TLS system. Improvements in data capture and analytical procedures should improve the accuracy of TLS-based volume and value estimates.
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  • 76
    Publication Date: 2010-06-01
    Description: Declining biodiversity is a critical component of global change owing to its influence on ecosystem functioning. Decomposition rate frequently increases with fungal species number, but the responses of extracellular enzymes to fungal species number have not been tested. To test the effect of biodiversity on decomposition and enzyme activities, quaking aspen ( Populus tremuloides Michx.) litter was inoculated with mixtures of one, two, four, or eight fungi from a pool of 16 fungi that had been isolated from a boreal forest in Alaska. Total CO2 release and the activities of β-glucosidase, which targets cellulose, and polyphenol oxidase, which targets lignin and other recalcitrant phenolic compounds, were observed across the range of species numbers in the mixtures. Total CO2 release and β-glucosidase activity increased with number of species but were only weakly correlated with each other; polyphenol oxidase activity had no correlation with number of species or CO2 release. The results indicate that, over 4 months, decomposition of labile carbon is positively correlated with number of species.
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  • 77
    Publication Date: 2009-02-01
    Description: Conversion of coniferous pine plantations into mixed-species forests on sandy soils is an important concern for forest and nature management in Europe. However, little is know of the effect of the applied sylvicultural strategy on biogeochemical cycling throughout the conversion process. This study examined the aboveground biomass production and nutrient (N, P, K, Ca, and Mg) cycling in terms of litterfall, immobilization in stems and branches, canopy exchange, and yearly root uptake in two scenarios of continuous cover forestry a decade after the first intervention for converting a homogeneous Scots pine (Pinus sylvestris L.) forest. Four regeneration types were studied: silver birch (Betula pendula L.) and pine after a shelterwood cutting and birch and pine after a group cutting. In conclusion, it can be stated that both the tree species and the conversion scenario influence the circulation of nutrients through the forest ecosystem: cycling of N, P, and K is determined by the tree species as well as the conversion scenario, whereas circulation of Ca and Mg is predominantly influenced by the type of conversion.
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  • 78
    Publication Date: 2009-02-01
    Description: The study of past historical events that have led to ecological changes is a recurrent topic in many disciplines. Given that many of these events have left a large and long-lasting evolutionary imprint on the extant population genetic structure of species, phylogeographic studies on modern taxa have been largely used to infer the impacts of these events and to complement previous paleoecological and paleobotanical surveys. In spite of the geographical and geological complexity of North America, converging patterns can be observed when comparing the available genetic data for forest trees. Such patterns include the co-location of genetic discontinuities among species and their coincidence with mountain ranges (e.g., the Appalachians, the Rocky Mountains, the Sierra Nevada, or the Transverse Volcanic Belt) and with previously inferred glacial refugia. Using examples drawn from the available literature, we illustrate such shared features and present the contrasting phylogeographic patterns observed among the different regions of the continent. The various evolutionary consequences of historical events that can be deduced from these phylogeographic studies (e.g., past bottlenecks, founder effects, allopatric divergence, or introgressive hybridization) are additionally discussed. The present challenges and future research prospects that are likely to further advance this field are finally outlined.
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  • 79
    Publication Date: 2010-07-01
    Description: In recent years, the annual imports of wooden bedroom furniture by the United States have been over five billion dollars, with more than two billion dollars of that coming from China. This trend led to an antidumping action against China in October 2003. Since January 2005, antidumping duties of 0.83% to 198.08% have been imposed on individual Chinese firms. To assess the impact of this antidumping action, intervention analysis was employed to examine the import values of four furniture commodities and the prices of two of them over 1997–2008. China and six other major competing countries were included in the analysis. With regard to import values from China, significant trade investigation effects were identified: the petition announcement generated a positive impact in March 2004; the preliminary less-than-fair-value (LTFV) determination had a negative impact from July to December 2004. However, the final implementation did not show any expected trade duty effect. The aggregate impact of the antidumping action on import values from China over 2003–2008 was approximately equivalent to a 1-month import reduction. The impact on the unit prices for China was insignificant. For the six competing countries, intervention analyses revealed that the antidumping action generated a positive trade diversion effect, with the magnitude smaller than the trade depression effect on China.
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  • 80
    Publication Date: 2009-09-01
    Description: We examined the use of dendroecological techniques for detecting past defoliations caused by Ormiscodes amphimone Fabricius (Saturniidae) in Nothofagus pumilio (Poepp. et Endl.) Krasser forests in northwestern Patagonia. We evaluated the suitability of the conifer Austrocedrus chilensis (D. Don) Pic. Serm. et Bizarri as a nonhost climate control for reconstructing Ormiscodes outbreaks on N. pumilio. Additionally, we assessed the effectiveness of three alternative procedures to detect past outbreaks: the use of a regional host chronology (instead of the nonhost chronology), the detection of pointer years (i.e., extremely narrow tree rings caused by defoliation), and the use of a morphological tree-ring signature associated with defoliation. Although differences in tree-ring growth response to climate between N. pumilio and A. chilensis did not support the use of the latter species as a reliable climatic control in most of our study area, the alternative procedures were effective in detecting past defoliation events. Based on the performance of the methods assessed here, we designed and tested a protocol for reconstructing past Ormiscodes defoliations on N. pumilio stands. Our results reinforce the need to conduct explicit comparisons of growth responses to climatic variability for host and potential nonhost species on a site-specific basis as well as the advantages of using multiple independent methods to more accurately detect past insect outbreaks.
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  • 81
    Publication Date: 2009-03-01
    Description: This paper presents soil fluxes of methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) from 12 sites located in four major forest types, black spruce ( Picea mariana (Mill.) BSP), jack pine ( Pinus banksiana Lamb.), aspen ( Populus spp.), and alder ( Alnus spp.) stands, in the Eastmain and Chibougamau regions of Quebec. Fluxes were determined with closed chambers during the snow-free period from May to October 2007. Well-drained black spruce, jack pine, and aspen forest soils were net sinks of atmospheric CH4 (–0.33 ± 0.11 mg·m–2·day–1), while alder-dominated wetland soils were sources of CH4 (0.45 ± 0.12 mg·m–2·day–1). The cut-over alder wetland soil produced 131 times more CH4 than the undisturbed wetland soil. Soil moisture and temperature mainly regulated CH4 fluxes. N2O fluxes from these forest soils were highly variable and smaller (1.6 ± 0.33 µg N·m–2·h–1) than those from deciduous forest soils. N2O emission from the cut-over black spruce forest soil was 2.7 times greater than that from the mature black spruce forest soil. Large C/N ratios (27 to 78) and slow soil N mineralization and nitrification rates in these forest soils may have led to small N2O fluxes. CO2 emissions from these forest soils, ranging from 0.20 to 2.7 g·m–2·day–1, were mainly controlled by soil temperature.
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  • 82
    Publication Date: 2010-07-01
    Description: The comparative analysis of a large set of long-term fertilization and thinning studies in the major forest types of interior Alaska is summarized. Results indicate that nutrient limitations may only occur during the early spring growth period, after which moisture availability is the primary control of tree growth on warm sites. The temperature dynamics of both air and soil set seasonal bounds on the nutrient and moisture dynamics for all forest types. Air and soil temperature limitations are the primary control of intraseasonal growth in the colder topographic locations in interior Alaska. These locations are usually dominated by black spruce (Picea mariana (Mill.) Britton, Sterns, Poggenb.) vegetation types. The seasonal progression of factors controlling growth is strongly tied to the state factor structure of the landscape.
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  • 83
    Publication Date: 2010-03-01
    Description: Restoration by imitating natural disturbances is widely practised in boreal forests to increase the availability of habitats for specialized species. We studied the abundance and species richness of saproxylic beetles on different types of created dead wood during 2 years after restoration. The study was conducted on areas of a large-scale experiment in which Norway spruce ( Picea abies (L.) Karst.) forests were restored by controlled burning and partial harvesting with down wood retention in southern Finland. More beetle species were attracted to spruces than to birches and more species were attracted to burnt trees than to unburnt trees killed by girdling. Birch-living species consistently benefited from fire, but on spruce, the abundance of cambium consumers and their associates was negatively affected by fire. Trees at harvested sites attracted more beetles in the first year, but the volume of down wood retention had only minor effects. Beetle assemblages were strongly altered by burning and harvesting. We conclude that burning and harvesting are efficient tools to promote species richness within a short time period, but there is a risk that the dead wood resource may be rapidly exhausted. Moreover, many saproxylic species of spruce forests may not be adapted to open habitats formed by stand-replacing disturbances.
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  • 84
    Publication Date: 2010-04-01
    Description: The current mountain pine beetle infestation in British Columbia’s lodgepole pine forests has raised concerns about potential impacts on water resources. Changes in forest structure resulting from defoliation, windthrow, and salvage harvesting may increase snow accumulation and ablation (i.e., spring runoff and flooding risk) below the forest canopy because of reduced snow interception and higher levels of radiation reaching the surface. Quantifying these effects requires a better understanding of the link between forest structure and snow processes. Light detection and ranging (lidar) is an innovative technology capable of estimating forest structure metrics in a detailed, three-dimensional approach not easily obtained from manual measurements. While a number of previous studies have shown that increased snow accumulation and ablation occur as forest cover decreases, the potential improvement of these relationships based on lidar metrics has not been quantified. We investigated the correlation between lidar-derived and ground-based traditional canopy metrics with snow accumulation and ablation indicators, demonstrating that a lidar-derived forest cover parameter was the strongest predictor of peak snow accumulation (r2 = 0.70, p 〈 0.001) and maximum snow ablation rate (r2 = 0.59, p 〈 0.01). Improving our ability to quantify changes in forest structure in extensive areas will assist in developing more robust models of watershed processes.
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  • 85
    Publication Date: 2009-10-01
    Description: Tree bark provides habitat for many organisms in forest ecosystems, but forest bark structure is typically not considered when important forest structural attributes are discussed. We describe a new metric for quantifying bark structure: a bark-fissure index (BFI). We examined species-specific changes in the frequency and depth of bark fissures caused by both horizontal and vertical splitting of bark layers for trees of different sizes and found that BFI generally scaled exponentially with stem diameter, with distinctively different patterns for 15 different tree species. We found a strong correlation between BFI and tree species preferences of the white-breasted nuthatch, a bark-foraging bird species. We demonstrate how BFI can be scaled up to define forest-scale bark structure using simple stand structural data, such as stand tables. This research contributes a new, objective, and repeatable way of quantifying tree and forest bark structure using simple bark measurements.
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  • 86
    Publication Date: 2009-11-01
    Description: Windstorms are among the most severe disturbances that affect mountain forests in central Europe. This study was conducted in a windthrow area resulting from a windstorm of an enormous scale in November 2004 in the Slovakian High Tatras Mountains. In this study, we used dendrochronological methods to determine the age structure and growth pattern of 529 Norway spruce ( Picea abies (L.) Karst) and 103 European larch ( Larix decidua Mill) during the last 200 years by examining cross sections of stumps. The multiage structure of the spruce indicated that this species regenerated constantly throughout the reconstruction period. The age structure of the larch was distinctly bimodal with only two ca. 20 year periods of regeneration. The initiation of larch recruitment overlapped in time with release pulses and showed severe disturbance events. A sudden and simultaneous production of compression wood and resin pockets in survivor trees indicated that wind was the most probable disturbance factor. The current composition of the stand with coexisting spruce and larch was a result of infrequent and severe windstorms events. Larch benefits from broader openings and regenerates in recruitment pulses once or twice per century, whereas spruce may regenerate constantly taking advantage of small-scale, gap-phase processes. Such a disturbance scenario allows the light-demanding larch to coexist among the more shade-tolerant spruce.
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  • 87
    Publication Date: 2009-02-01
    Description: A critical component of assessing the impacts of climate change on forest ecosystems involves understanding associated changes in the biogeochemical cycling of elements. Evidence from research on northeastern North American forests shows that direct effects of climate change will evoke changes in biogeochemical cycling by altering plant physiology, forest productivity, and soil physical, chemical, and biological processes. Indirect effects, largely mediated by changes in species composition, length of growing season, and hydrology, will also be important. The case study presented here uses the quantitative biogeochemical model PnET-BGC to test assumptions about the direct and indirect effects of climate change on a northern hardwood forest ecosystem. Modeling results indicate an overall increase in net primary production due to a longer growing season, an increase in NO3– leaching due to large increases in net mineralization and nitrification, and slight declines in mineral weathering due to a reduction in soil moisture. Future research should focus on uncertainties, including the effects of (1) multiple simultaneous interactions of stressors (e.g., climate change, ozone, acidic deposition); (2) long-term atmospheric CO2 enrichment on vegetation; (3) changes in forest species composition; (4) extreme climatic events and other disturbances (e.g., ice storms, fire, invasive species); and (5) feedback mechanisms that increase or decrease change.
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  • 88
    Publication Date: 2010-06-01
    Description: Automated individual tree detection and delineation from high spatial resolution imagery provides good opportunities for forest inventory at a large scale. However, the accuracy of delineated crown size compared with ground measurements may not be sufficient. Thus, ordinary least squares (OLS) regression is no longer an appropriate approach to estimating and predicting variables from the delineated tree crown because both response variable and regressor are subject to measurement errors. In this study, we describe the functional and structural relationships between field-measured tree variables (i.e., tree diameter and crown width) and delineated tree crown width from remotely sensed imagery. We investigated the performance of OLS and three error-in-variable regression techniques including maximum likelihood estimator (MLE), major axis (MA) regression, and reduced major axis (RMA) regression using field-measured data and simulated data under different conditions. Our results indicated that MLE was desirable for estimating unbiased model coefficients. However, the adjustment assumption of the MLE model should be checked for predicting tree variables from remotely sensed imagery. When the assumption holds, the MLE model performed better for predicting the response variables than did the OLS model. Otherwise, the MLE model produced biased predictions for the response variables.
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  • 89
    Publication Date: 2010-09-01
    Description: It is widely accepted that N limits primary production in temperate forests, although colimitation by N and P has also been suggested, and on some soils, Ca and base cations are in short supply. I conducted a meta-analysis to assess the strength of existing experimental evidence for limitation of primary production by N, P, and Ca in hardwood forests of the northeastern United States and southeastern Canada using data from 35 fertilization experiments in deciduous forests on glaciated soils across the region. There is strong evidence for N limitation (formal meta-analysis weighted mean response ratio = 1.51, p 〈 0.01; simple mean = 1.42, p 〈 0.001). Forest productivity also tended to increase with additions of P (simple mean = 1.15, p = 0.05) and Ca (simple mean = 1.36, p 〈 0.001). Across all treatments, 85% of response ratios were positive. Multiple-element additions had larger effects than single elements, but factorial experiments showed little evidence of synergistic effects between nutrient additions. Production responses correlated positively with the rate of N fertilization, but this effect was reduced at high rates of ambient N deposition.
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  • 90
    Publication Date: 2010-07-01
    Description: The resilience and vulnerability of permafrost to climate change depends on complex interactions among topography, water, soil, vegetation, and snow, which allow permafrost to persist at mean annual air temperatures (MAATs) as high as +2 °C and degrade at MAATs as low as –20 °C. To assess these interactions, we compiled existing data and tested effects of varying conditions on mean annual surface temperatures (MASTs) and 2 m deep temperatures (MADTs) through modeling. Surface water had the largest effect, with water sediment temperatures being ~10 °C above MAAT. A 50% reduction in snow depth reduces MADT by 2 °C. Elevation changes between 200 and 800 m increases MAAT by up to 2.3 °C and snow depths by ~40%. Aspect caused only a ~1 °C difference in MAST. Covarying vegetation structure, organic matter thickness, soil moisture, and snow depth of terrestrial ecosystems, ranging from barren silt to white spruce ( Picea glauca (Moench) Voss) forest to tussock shrub, affect MASTs by ~6 °C and MADTs by ~7 °C. Groundwater at 2–7 °C greatly affects lateral and internal permafrost thawing. Analyses show that vegetation succession provides strong negative feedbacks that make permafrost resilient to even large increases in air temperatures. Surface water, which is affected by topography and ground ice, provides even stronger negative feedbacks that make permafrost vulnerable to thawing even under cold temperatures.
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  • 91
    Publication Date: 2009-07-01
    Description: We identify species–environment relationships to predict the occurrence of Chinese tallow ( Triadica sebifera (L.) Small) on forestlands in the southern US, where it has emerged as the most pervading, stand-replacing, alien tree species. Tallow invasions are more likely to be observed on low and flat lands, areas adjacent to water and roadways, sites recently harvested or disturbed, younger stands, and private forestlands. The winter extreme minimum temperature tends to restrain tallow northward migration. Increases in both range and severity of tallow invasions are predicted with a warming climate trend, and the situation could be worse if the warming is coupled with an increased frequency and intensity of disturbances. Monitoring and mitigation strategies are proposed to assist this region and other countries threatened by tallow invasions.
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  • 92
    Publication Date: 2010-07-01
    Description: This paper assesses the resilience of Alaska’s boreal forest system to rapid climatic change. Recent warming is associated with reduced growth of dominant tree species, plant disease and insect outbreaks, warming and thawing of permafrost, drying of lakes, increased wildfire extent, increased postfire recruitment of deciduous trees, and reduced safety of hunters traveling on river ice. These changes have modified key structural features, feedbacks, and interactions in the boreal forest, including reduced effects of upland permafrost on regional hydrology, expansion of boreal forest into tundra, and amplification of climate warming because of reduced albedo (shorter winter season) and carbon release from wildfires. Other temperature-sensitive processes for which no trends have been detected include composition of plant and microbial communities, long-term landscape-scale change in carbon stocks, stream discharge, mammalian population dynamics, and river access and subsistence opportunities for rural indigenous communities. Projections of continued warming suggest that Alaska’s boreal forest will undergo significant functional and structural changes within the next few decades that are unprecedented in the last 6000 years. The impact of these social–ecological changes will depend in part on the extent of landscape reorganization between uplands and lowlands and on policies regulating subsistence opportunities for rural communities.
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  • 93
    Publication Date: 2010-02-01
    Description: Multiple-use forestry requires comprehensive planning to maximize the utilization and sustainability of many forest resources whose growth and productivity are interconnected. Forest fungi represent an economically important nonwood forest resource that provides food, medicine, and recreation worldwide. A vast majority of edible and marketed forest mushrooms belong to fungi that grow symbiotically with forest trees. To respond to the need for planning tools for multiple-use forestry, we developed empirical models for predicting the production of wild mushrooms in pine forests in the South-Central Pyrenees using forest stand and site characteristics as predictors. Mushroom production and species richness data from 45 plots were used. A mixed modelling technique was used to account for between-plot and between-year variation in the mushroom production data. The most significant stand structure variable for predicting mushroom yield was stand basal area. The stand basal area associated with maximum mushroom productivity (15–20 m2·ha–1) coincides with the peak of annual basal area increment in these pine forests. Other important predictors were slope, elevation, aspect, and autumn rainfall. The models are aimed at supporting forest management decisions and forecasting mushroom yields in forest planning.
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  • 94
    Publication Date: 2009-11-01
    Description: Based on a multilevel nonlinear mixed model approach, a basal area increment model was developed for individual aspen ( Populus tremuloides Michx.) trees growing in boreal mixedwood stands in Alberta. Various stand and tree characteristics were evaluated for their contributions to model improvement. Total stand basal area, basal area of larger trees, and the ratio of target tree height to maximum stand height were found to be significant predictors. When random effects were modeled at the plot level alone, correlations among normalized residuals remained significant. These correlations were successfully removed when random effects were modeled at both plot and tree levels. The predictive abilities of two alternative models were evaluated at the population, plot, and tree levels. At the tree level, a tree measured at the first growth period was used for estimating random parameters, and basal area increments of that tree in future growth periods were subsequently predicted. At the plot level, one to five trees in each plot at each growth period were used to estimate random parameters. Basal area increments of the remaining trees in the same plot at the same growth period were subsequently predicted. The final model provided accurate predictions at all three levels.
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  • 95
    Publication Date: 2009-06-01
    Description: Population-averaged (PA) and subject-specific (SS) approaches for modeling the height of dominant or codominant lodgepole pine ( Pinus contorta Dougl. ex Loud.) trees were evaluated using six candidate models derived from the Chapman–Richards and logistic functions. The true PA response obtained from separate fits of the models was compared with the typical mean (TM) response computed using only the fixed-effects parameters of the mixed-effects models. Results showed that the TM response had higher prediction errors than the PA response, suggesting that a true PA response and not the TM response is needed to reflect the overall mean response of the model. The SS approach produced improved height predictions relative to the PA approach when evaluated using independent validation data. In addition, the logistic performed better than the Chapman–Richards function, regardless of whether the SS or PA approach was applied. Among the candidate models, the logistic function with the inclusion of site index gave the most accurate predictions. Three scenarios of calibrating the mixed-effects models on the validation data set were compared. The SS predictions obtained using only one premeasured observation per subject were poorer than those using all observations, but they were still generally better than PA predictions.
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  • 96
    Publication Date: 2010-02-01
    Description: Exotic Pinus taeda L. plantations may be more productive than native ones. Several hypotheses may explain this difference; however, process models with a light-interception-driving variable cannot test these hypotheses without foliage display first being quantified in native and exotic trees. We quantified leaf area duration in North Carolina, USA (natural), and Gobernador Virasoro, Argentina (exotic), with no additional nutrients and optimum fertilizer treatments. More (60%–100%) foliage was displayed but for a shorter (∼86 fewer days) time per fascicle in the exotics than in the naturals. Study inference was limited, with only one native and one exotic site. However, while the sites were markedly different in soils, climate, resource availability, and genetics, and we observed significant differences in fascicle display and longevity, most fascicles at both sites survived two growing seasons: the one in which they were produced and the subsequent one. This robust finding indicates it would be reasonable to use two growing seasons for fascicle longevity in process modeling to test hypotheses explaining growth differences in native and exotic loblolly. Fertilization had no effect on any exotic tree parameter, but it increased natural tree fascicle number (24%) and length (30%).
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  • 97
    Publication Date: 2009-11-01
    Description: We document accelerating invasion of woody vegetation into wetlands on the western Kenai Peninsula lowlands. Historical aerial photography for 11 wetland sites showed that herbaceous area shrank 6.2%/decade from 1951 to 1968, and 11.1%/decade from 1968 to 1996. Corresponding rates for converting herbaceous area to shrubland were 11.5% and 13.7%/decade, respectively, and, for converting nonforest to forest, were 7.8% and 8.3%/decade, respectively. Black spruce ( Picea mariana (Mill.) BSP) forests on three wetland perimeters established since the Little Ice Age concluded in the 1850s. Dwarf birch shrubs at three wetland sites showed median apparent tree-ring age of 13 years, indicating recent shrub colonization at these sites. Peat cores at 24 wetland sites (basal peat ages 1840 – 18 740 calibrated years before present) indicated that these peatlands originated as wet Sphagnum –sedge fens with very little woody vegetation. Local meteorological records show a 55% decline in available water since 1968, of which one-third is due to higher summer temperatures and increased evapotranspiration and two-thirds is due to lower annual precipitation. These results suggest that wet Sphagnum–sedge fens initiating since the end of the Wisconsin glaciation began to dry in the 1850s and that this drying has greatly accelerated since the 1970s.
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  • 98
    Publication Date: 2009-03-01
    Description: Photosynthetic gas-exchange characteristics were measured in Pinus flexilis James (limber pine) during two drought years in a xeric, subalpine ecosystem of the Rocky Mountains. Limber pine exhibited conservative water-use traits, including low specific leaf area, leaf nitrogen, stomatal conductance, transpiration (E), and light-saturated net photosynthesis (Amax), but exhibited high needle longevity, water-use efficiency (Amax/E), and stable carbon isotope composition. Net photosynthesis declined strongly with leaf-to-air vapour pressure deficit, resulting in a bimodal seasonal pattern of Amax. Although very little gas exchange was observed in late summer, photosynthetic activity extended into October. The avoidance of gas exchange during high atmospheric demand maximized whole-season water-use efficiency. Leaf temperature and leaf-to-air vapour pressure deficit were higher on south-facing slopes during both moderate (2006) and severe (2007) drought. Severe drought caused lower stomatal conductance and E on the southeast-facing slope, but neither Amax nor canopy reflectance indices differed among slope aspects. Although Amax was lower in 2007 than 2006, branch-length increment did not differ. Foliar stable carbon isotope composition was higher in needles produced in dry years but did not vary among slope aspects. These results indicate that physiological acclimation to water stress prevented among-aspect differences in Amax and that shoulder-season photosynthesis may become increasingly important in a warmer climate.
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  • 99
    Publication Date: 2009-08-01
    Description: Acoustic tools are increasingly used to estimate standing-tree (dynamic) stiffness; however, such techniques overestimate static stiffness, the standard measurement for determining modulus of elasticity (MOE) of wood. This study aimed to identify correction methods for standing-tree estimates making dynamic and static stiffness comparable. Sixty Pinus taeda L. trees, ranging from 14 to 19 years old, obtained from genetic tests established in the southeastern United States, were analyzed. Standing-tree acoustic velocities were measured using the TreeSonic tool. Acoustic velocities were also recorded in butt logs cut from the same trees using the Director HM200. A strong but biased relationship between tree and log velocities was observed, with tree velocities 32% higher (on average) than the corresponding log velocities. Two correction methods, one for calibrating tree velocities and one for accounting for differences in wood moisture content, were used to determine an adjusted MOE. After correction, adjusted MOE estimates were in good agreement with static longitudinal MOE values measured on clearwood specimens obtained from the trees, and no systematic bias was observed. The results of this study show that acoustic estimates of MOE on standing trees largely depend on how the data are processed and the reference method used.
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  • 100
    Publication Date: 2009-09-01
    Description: The need to improve control of cone rust epidemics led us to investigate seasonal fruiting and sporulation of cone rusts in Norway spruce ( Picea abies (L.) Karst.) cones and alternate hosts in 2006–2008. Spermogonia of Chrysomyxa pirolata Wint. and aecia of Thekopsora areolata (Fr.) Magnus developed in current-year cones in June, whereas C. pirolata aecia developed and started to sporulate in July. Thekopsora areolata aecia sporulated mainly in previous-year cones in May–August. Uredinia, telia, and basidia of C. pirolata developed in overwintered Pyrola sp. and Orthilia secunda L. leaves in May and sporulated in May–June. Uredinia of T. areolata developed in current-year Prunus padus L. leaves in June and sporulated in June–August. Telia of T. areolata developed in late summer, but no basidia were observed in overwintered Prunus padus leaves in March–May. Only minor variation occurred at the time of fruiting and sporulation of cone rusts both among cones and leaves of alternate hosts. Periods of high daily rainfall in May coincided with the epidemic peaks during female flowering in 2006. Dry periods in May coincided with high C. pirolata uredinia and low telia production on alternate hosts. However, monthly rainfall during pollination did not explain the epidemic rust patterns in cones. Timing of disease control is discussed.
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