The value of six key soil variables for incorporation into a South African forest site classification system

The intensive nature of management practices in the exotic monoculture plantations of South Africa requires reliable decision support systems. Recent socio-economic developments, the need for optimal forest productivity, as well as increasing awareness of broader ecosystem values and environmental risks, highlight the importance of a unified approach to forest site classification and evaluation. This paper highlights the value of specific soil characteristics and its application value for a range of silviculture and management aspects related to site-specific forestry. A limited set of six soil variables are proposed for ecological mapping of forest landscapes at high-resolution operational-level scales. The variables proposed are parent material, soil classification, effective soil depth, depth limiting material, topsoil organic matter and topsoil texture. Each variable is discussed in terms of its significance as well as relevance to plantation forestry in South Africa. Shortcomings in our knowledge base and research requirements are highlighted, and the format of incorporation into a national forest site classification system is proposed. This paper will contribute to unity of purpose and understanding of forest site classification and evaluation in South Africa, and will promote management frameworks and decision support systems with desired environmental, economic and social benefits.