Alternative land uses to forestry in the Western Cape : a case study of La Motte plantation

[摘要] ENGLISH ABSTRACT:The South African government started the restructuring process of the state's forest assets in 1998. Theprivatisation process includes all the assets of the South African Forestry Company (SAFCOL) and half of theformer homelands' 150 000 hectares of forest. In August 2000 SAFCOL released their 'Operational Plan forImplementing Exit from Forestry in the Southem-Cape Portion of the Western Cape Region. This planidentified only major land uses (agriculture, forestry, and conservation). A more detailed and intensive landevaluation study was required to specify land utilisation types that are tailor-made to each land unit of the studyarea.The main intention of this research study is to develop a more detailed evaluation process that elaborates on theland uses proposed by SAFCOL, which is site-specific in terms of the type of agricultural system to be used onspecific areas, or the type of indigenous vegetation to be restored in conservation areas. La Motte plantation wastaken as the case study and the SAFCOL digital database for the study area was used as the input data.The Automated Land Evaluation System (ALES) was the computer software package used to build the expertsystem to evaluate land according to the method presented in the FAO 1976 report. The ALES model built inthis research study had 15 decision trees (one per land utilisation type) resulting in a total of 1678 branches,which relate land characteristics to severity levels of land qualities. During the computation of an evaluationALES attempts to place each map unit into one of the four severity levels of land qualities within each landutilisationtype. Physical suitability of each land unit for each land utilisation type was determined by themaximum limitation method. ALES is not a GIS and does not by itself display maps. The evaluation resultmatrix was exported into ArcMap for further optimisation and geographical analysis to enable the spatialrepresentation of the results. After completion, taking into account the theoretical background, optimal terrainunits were identified for the different land uses considered and the results are presented as tables and maps.Fynbos is the most suitable alternative land use for the study area followed by Pears, Sauvignon Blanc andChardonnay vines. Pinotage, Shiraz, Cabernet Sauvignon and Cabernet Franc vines were least suitable asalternatives. The study found that the SAFCOL's database is not sufficient to meet the requirements of a detailedsite-specific land evaluation process. The polygon attribute table of the soil coverage only provided a subset ofthe land characteristics necessary to build and run the model. Data fields like soil form, depth, drainage,wetness, terrain type, aspect and climatic information had to be created because most of the data provided werein a non-digital form. The database was not complete and more precise data are needed to improve the system.

[发布机构] Stellenbosch University