The impact of soil water repellency on soil hydrological and erosional processes under Eucalyptus and evergreen Quercus forests in the Western Mediterranean
C. O. A. Coelho A E , A. Laouina B , K. Regaya C , A. J. D. Ferreira A D , T. M. M. Carvalho A , M. Chaker B , R. Naafa B , R. Naciri B , A. K. Boulet A and J. J. Keizer AA Centro de Estudos do Ambiente e Mar (CESAM), Department of Environment and Planning, University of Aveiro, P-3810-193 Aveiro, Portugal.
B Chaire UNESCO-Gas Natural, Faculté des Lettres et Sciences Humaines, Université Mohamed V, BP 1040 Ryad, 10104 Rabat, Morocco.
C Institut National Agronomique de Tunisie, 43 Avenue Charles Nicolle, 1082 – Tunis Mahrajène, Tunisia.
D Centro de Estudos dos Recursos Naturais, Ambiente e Sociedade, Departament of Pure and Environmental Sciences, ESAC, IPC, Bencanta, P-3040-316 Coimbra, Portugal.
E Corresponding author. Email: coelho@dao.ua.pt
Australian Journal of Soil Research 43(3) 309-318 https://doi.org/10.1071/SR04083
Submitted: 23 June 2004 Accepted: 7 January 2005 Published: 25 May 2005
Abstract
Forest areas of the Mediterranean regions of Portugal, Morocco, and Tunisia are suffering major land use changes, with the replacement of traditional evergreen Quercus species (i.e. Quercus suber and Quercus ilex) by fast-growing Eucalyptus species.
Since Eucalyptus species are amongst those with a higher impact on soil water repellency, this study examined the effect of the replacement on soil properties, water repellency, and on soil hydrological processes and erosion rates. Measurements were performed in areas that correspond to the climatic distribution of evergreen Quercus suber: at Mação and Portel in Portugal; Ben Slimane in Morocco; and Cap Bon, Sousse, and Ain Snoussi in Tunisia.
Soil superficial characteristics, including vegetation and litter cover, organic matter content, soil compaction and shear strength, and water repellency were measured for evergreen oak and Eucalyptus stands and related to soil erosion rates and soil hydrological processes.
The data are based on the spatial distribution of properties assessed through the use of intensive spatial sampling and on rainfall simulations to address soil hydrological and erosional processes. The results show very different wetting patterns for some of the Eucalyptus stands during dry and moist periods, as a result of strong hydrophobic characteristics following dry spells. Nevertheless, the Eucalyptus stands in semi-arid climate show no sign of water repellency, which contradicts the theory that water repellency is purely a result of dry conditions. The experiments show no significant increases on overland flow amounts and erosion rates as direct result of soil water repellence (hydrophobicity) characteristics.
Additional keywords: Quercus suber, Eucalyptus spp., water repellency, overland flow, erosion, Mediterranean.
Acknowledgments
This paper was only possible due to the co-operative work developed under the MEDCHANGE Project ERB-IC18-CT97-0147 ‘Effects of land use and land management practices changes on land degradation under forest and grazing ecosystems’, financed by the EC (DG XII) through the INCO-DC program.
This work was also performed with the financial help of the projects FAIR (6-CT98-4027, ‘Development of amelioration strategies to reduce environmental deterioration and agricultural production losses in water repellent losses’.
We thank Laouini Mohamed and Ltaief Moncef for their help in the Tunisian field campaign.
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