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Title: Soil hydrophobicity in wet Mediterranean pine and eucalyptus forests, Agueda Basin, north-central Portugal
Author: Doerr, S. H.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 1998
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This thesis investigates soil hydrophobicity in a comparatively wet (>1500 mm/yr) mediterranean environment focusing on unburnt and burnt commercial Eucalyptus globulus and Pins pinaster forests in north-central Portugal. Principal aims were to assess (i) its severity and spatial and vertical variability, (ii) the impact of fire, (iii) variations between soil particle size fractions and (iv) the causal factors and mechanisms involved. Hydrophobicity in all forest types was found to be amongst the most severe reported in the literature (MED 24%, WDPT >1h). Findings differ from most previous studied: (1) Hydrophobicity was neither of patchy distribution nor confined to distinct layers, but a consistent property of all forest soils. This is thought to be due to the comparatively high release and thorough distribution of hydrophobic substances from the species involved, aided by the relatively wet climate and the uniform character of the forests. (2) Burning had little impact on hydrophobicity. This is attributed to: (i) pre-burn hydrophobicity being so severe that hydrophobic compounds released from litter during burning contribute to detectable additional hydrophobic effects and (ii) soil temperatures reached being insufficient to destroy hydrophobicity. (3) Fine soil particle fractions are as, or more hydrophobic than coarse ones. A high supply of hydrophobic substances is thought to allow a hydrophobic coating on all particles. (4) After wetting, hydrophobicity is not re-established in soils simply by drying, but a fresh input of hydrophobic substances is thought to be required. Soils under E. globulus are more hydrophobic than those under P. pinaster. Hydrophobicity develops within a year of planting E. globulus. The litter layers of both species, and the root zone of E. globulus, are identified as sources of hydrophobic substances. Models are developed regarding the establishment of, fire-effects on, and short-term temporal variations of hydrophobicity. Hydrogeomorphological and land management implications are discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available