【数字土壤制图】Brendan P. Malone Alex B. McBratney and Budiman Minasny.Spatial Scaling for Digital Soil Mapping. SSSAJ doi: 10.2136-sssaj2012.0419 Vol. 77 No. 3 p. 890-902

Abstract

We describe in this paper a broad overview of spatial scale concepts and scaling procedures that are specifically relevant for digital soil mapping (DSM). Despite the recent growth and operational status of DSM one existing and foreseeably growing issue for users of digital soil information is the inequality of spatial scales between what is required and what is actually available to adequately address soil-related questions posed from within and from outside the soil science community. In the absence of conducting new soil survey or not being able to acquire the original legacy soil information (soil point data) as a means of creating user-specified soil information products spatial scaling provides a useful solution. Spatial scaling for DSM involves changes in map extent grid-cell resolution and prediction support. We review in this paper the different forms of spatial scaling which are described in terms of changes to grid spacing and prediction support. Fine-gridding and coarse-gridding are operations where the grid spacing changes but support remains unchanged. Deconvolution and convolution are operations where the support always changes which may or may not involve changing the grid spacing. While disseveration and conflation operations occur when the support and grid size are equal and both are then changed equally and simultaneously. Some possible and existing pedometric methods are described for implementation of each scaling process as is an extended example for performing convolution where the support changes yet the resolution remains the same.

【土壤氮同位素变化】P.L. Mudge L.A. Schipper A. Ghani M. Upsdell and W. T. Baisden. Changes in Natural¹⁵N Abundance in Pastoral Soils Receiving Differing Amounts of Superphosphate Fertilizer and Irrigation for 50 Years. SSSAJ doi: 10.2136-sssaj2012.0333 Vol. 77 No. 3 p. 830-841

Abstract

Intensification of pastoral agriculture has led to increased N losses to the wider environment. This has led to an emphasis on improving our understanding of soil N dynamics and development of management practices which mitigate N losses. The natural abundance of the stable isotope δ¹⁵N relative to ¹⁴N (δ¹⁵N) in soils can provide an integrated measure of past N cycle processes and in particular soil δ¹⁵N can reflect past N losses because during most N transformation processes ¹⁴N is preferentially lost. We therefore hypothesized that pastoral soils under intensive management regimes (with high N inputs cycling and loss) would become progressively enriched with ¹⁵N relative to soils under less intensive management. To test this hypothesis we analyzed archived surface soils from two long-term grazed field trials in New Zealand where diff