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Title: Spatio-temporal dynamics and hydrogeomorphic implications of soil water repellency within Eucalyptus forests in north-central Portugal
Author: Leighton-Boyce, G.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2003
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This thesis investigates spatio-temporal variations in soil water repellency and their hydrogeomorphic effects within eucalyptus plantations in north-central Portugal. Rainfall simulation with and without wetting agents were used to quantify the effects of repellency on overland flow, slopewash, splash detachment and wetting patterns at the small-plot scale on long-unburnt and recently burnt terrain. Monitoring over 16-months (>9000 paired repellency and soil moisture measurements) was carried out at four different sites at meso-(2 m) and micro-scales (10 cm) to establish spatio-temporal repellency patterns. Repellency increased overland flow generation 16-fold on unburnt terrain at the small-plot scale. Responses on burnt terrain were similarly enhanced with a mean overland flow coefficient of 70% being recorded. Where present, eucalyptus litter layer greatly reduced overland flow and erosions by providing considerable moisture storage and protection. Repellency extent varied seasonally, being widespread following prolonged dry periods and minimal following prolonged wet periods. At its maximum, it was spatially contiguous under 10-year-old eucalyptus stands, but discontinuous under younger stands (d5 years). Discontinuously repellent terrain included wettable soil columns dispersed over the slope area. Regardless of season or extent of repellency, where repellency was recorded it was mainly of extreme severity (³36% Ethanol). Repellency begins to break down following >50 mm but d140 mm rainfall and may become re-established (from minimal extent to contiguous surface repellency) after d22 days of generally dry weather. Where soils were continuously repellent following long dry periods, these soils were wettable at moisture contents ³275 vol. and repellent at d145 vol. Between these thresholds soils could be wettable or repellent. Implications of the spatio-temporal repellency patterns found for slope and catchment hydrogeomorphic responses are explored.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available