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Soil variability along a topographic sequence, University of British Columbia endowment lands

University of British Columbia

Environmental factors affecting a topographic sequence of soils were examined on the University of British Columbia Endowment Lands. The soils and other landscape components were studied at four sites along a transect to provide information on those processes which are active in affecting site and soil development. Characterization of the water chemistry of precipitation, organic leachate, soil solution and groundwater; the magnitude of soil spatial variability and the influence of land use on the landscape were also evaluated. The landscape components considered to exert the greatest influence on soil and site development include topography, moisture regime, vegetation and parent material. The interrelationship between these components has resulted in the development of four podzol soils which differ in horizon differentiation and in the extent to which mobile constituents are redistributed in the pedon. Man, considered as an environmental factor, has indirectly influenced site and soil development through land use. The effects attributed to logging are reflected in the modification of the moisture regime along the lower portion of the transect. This appears to be the controlling factor in altering vegetation successional patterns and in affecting soil development. In these soils, soil development appears to be intensified, wiht the resultant increase in weathering and leaching processes in the surface mineral horizons and the initiation of the redistribution of mobile constituents within the pedon. Characterization of selected chemical components of precipitation (including crown wash), organic layer leachate, soil solution and groundwater was conducted to elucidate ion mobility and nutrient availability. The data presented suggest that: the weathering of soil minerals is the main source of ions to the soil-water system; the mineral weathering rates in the soils are fairly constant; the chemical concentrations in the groundwater are controlled to a great extent by the weathering of soil minerals; the input of ions from the atmosphere and organic leachates can be appreciable and may influence the exchange status in the surface mineral horizons; and the leaching of organic materials may be important in maintaining plant nutrient requirements in soils of inherent low fertility. Displacement techniques appear to be useful in providing data for the evaluation of water quality relationships between the atmosphere and the soil system and for assessing site-fertility. Spatial variability in the two soils was studied to elucidate soil chemical heterogeneity. Assessment of three sampling techniques in relation to sampling efficiency and intensity was made in light of the soil heterogeneity expressed by the soils. Spatial variability recorded for these soils, suggests that soil heterogeneity should be considered as an important soil characteristic as are the soils' inherent chemical and physical properties. The greatest extent of variation in soil chemical properties was found in the surface mineral layers where weathering and influences from environmental factor interactions are more pronounced. It is this portion of the soil that will regulate the sampling intensity required for soil field studies. The data presented suggest that the use of composite sampling schemes will allow for reasonable estimates of soil properties and reduce the probable disparites caused by non-representative samples.

Text

2010-02-21

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http://hdl.handle.net/2429/20664

Soil Science

University of British Columbia

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