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Numerical assessment of soil properties in relation to classification and genesis

University of British Columbia

Soil properties are examined from two perspectives: (1), in relation to classes and categories of classification systems, and (2), in terms of mathematically tractable, chemical and physical continuums. Through four independent studies, major limitations of each approach are defined and evaluated. The first study examines samples from six different types of horizons commonly found in podzolic soils. The results suggest that in a chemical context the horizons do not represent distinct entities; rather they appear to dominate overlapping regions along a multidimensional chemical spectrum. The second study analyzes the extent to which V.J. Krajina's phytosociological classification of biogeocoenoses explains the variability of a number of site properties. It is determined that many of the physiographic properties are significantly related to the association category of the system, but that many of the pedologic properties are not. The two studies lead to a dichotomy concerning classification and the statistical relationships both among soil properties and between soil properties and other elements of an ecosystem. Where sampling is restricted to comparatively limited ranges along environmental gradients, relationships may be so weak that a classification based on only a few properties or elements may not be that useful for associated properties and elements. On the other hand, because of the implied high degree of variability, attempts to develop a holistic, integrated classification are not likely to be highly successful either. In the third study chemical and physical changes across a prograded beach chronosequence are examined. It is found that soil development over both time and depth may be modelled by a non-linear regression equation. The last of the four studies concerns an evaluation of the extent to which the inherent variability of soil properties masks expected trends across a morainal chronosequence. For those properties most affected by vegetation succession, the same type of regression equation as used in the previous study was applied with excellent results. For the other, less dynamic properties, assumed trends were too obscure to model. The two studies suggest that, where soil properties are directly influenced by strong environmental gradients, ordination techniques may be quite illuminating. In less biologically stressful environments and in those which have reached steady state, both the predictive and explanatory capabilities of such techniques may be relatively low. These findings closely parallel those discussed earlier concerning classification. The thesis concludes that for many applications attempts to model and map the landscape as an integrated whole should be abandoned. Furthermore, instead of viewing the landscape from either a classification or ordination perspective, digital terrain models should be considered. Data for the models could be generated from regionalized, statistical, stochastic, and deterministic equations, calibrated with ground truth observations. Traditional polygon and contour maps can also be transformed into digital terrain models. Landscape interpretations could then be tied directly to measured and estimated data. This approach involves a minimum loss of information and is conceptually simple.

Text

2010-04-15

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http://hdl.handle.net/2429/23676

Soil Science

University of British Columbia

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