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  • 1
    ISSN: 1573-5036
    Schlagwort(e): cations ; fire ; nitrogen ; nutrients ; phosphorus ; slash-and-burn ; soil ; tropical forests
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The most commonly observed change in soil following slash-and-burn clearing of tropical forest is a short-term increase in nutrient availability. Studies of shifting cultivation commonly cite the incorporation of nutrient-rich ash from consumed aboveground biomass into soil as the reason for this change. The effects of soil heating on nutrient availability have been examined only rarely in field studies of slash-and-burn, and soil heating as a mechanism of nutrient release is most often assumed to be of minor importance in the field. Few budgets for above and belowground nutrient flux have been developed in the tropics, and a survey of results from field and laboratory studies indicates that soils are sufficiently heated during most slash-and-burn events, particularly in dry and monsoonal climates, to cause significant, even substantial release of nutrients from non-plant-available into plant-available forms in soil. Conversely, large aboveground losses of nutrients during and after burning often result in low quantities of nutrients that are released to soil. Assessing the biophysical sustainability of an agricultural practice requires detailed information about nutrient flux and loss incurred during management. To this end, current conceptual models of shifting cultivation should be revised to more accurately describe these fluxes and losses.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    ISSN: 1573-5036
    Schlagwort(e): fire ; nitrogen ; phosphorus ; soil nutrient heterogeneity ; tree effects ; tropical dry forest
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Individual trees are known to influence soil chemical properties, creating spatial patterns that vary with distance from the stem. The influence of trees on soil chemical properties is commonly viewed as the agronomic basis for low-input agroforestry and shifting cultivation practices, and as an important source of spatial heterogeneity in forest soils. Few studies, however, have examined the persistence of the effects of trees on soil after the pathways responsible for the effects are removed. Here, we present evidence from a Mexican dry forest indicating that stem-related patterns of soil nutrients do persist following slash-and-burn removal of trees and two years of cropping. Pre-disturbance concentrations of resin extractable phosphorus (P), bicarbonate extractable P, NaOH extractable P, total P, total nitrogen (N) and carbon (C), KCl extractable nitrate (NO3 -), and net N mineralization and nitrification rates were higher in stem than dripline soils under two canopy dominant species of large-stemmed trees with contrasting morphologies and phenologies (Caesalpinia eriostachys Benth. and Forchhammeria pallida Liebm.). These stem effects persisted through slash burning and a first growing season for labile inorganic and organic P, NaOH inorganic P, and plant-available P, and through a second growing season for labile organic P, NaOH organic P, and plant-available P. While stem effects for extractable NO3 -, net nitrification rates, total N and C disappeared after felling and slash burning, these stem effects returned after the first growing season. These results support the view that tree-influenced patterns of soil nutrients do persist after tree death, and that trees contribute to the long-term spatial heterogeneity of forest soils.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Theory and decision 40 (1996), S. 191-214 
    ISSN: 1573-7187
    Schlagwort(e): 62J99 ; 62F15 ; 62C10 ; 62C15 ; Utility theory ; non-informative prior ; distributional distance ; entropy ; Hellinger distance ; conjugate prior ; Fisher information ; exponential families ; bayes estimator
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Sociologie , Wirtschaftswissenschaften
    Notizen: Abstract Since the choice of a particular loss function strongly influences the resulting inference, it seems necessary to rely on “intrinsic” losses when no information is available about the utility function of the decision-maker, rather than to call for classical losses like the squared error loss. Since this setting is quite similar to the derivation of noninformative priors in Bayesian analysis, we first recall the conditions of this derivation and deduce from these conditions some requirements on the intrinsic losses. It then appears that these loss functions should only depend on the sampling distribution and that they should be independent of the parameterization of the distribution. The resulting estimators are therefore transformation equivariant. We study the properties of two natural intrinsic losses, namely entropy and Hellinger losses, and show that they can be expressed in closed form for exponential families. Moreover, the entropy loss also provides analytic expressions of Bayes estimators under conjugate priors; the derivation of Bayes estimators associated with the Hellinger loss is more cumbersome, as shown in Poisson and Gamma cases, while leading to similar estimators.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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