Main Article Content
The influence of site factors on nitrogen mineralization in forest soils of the Mpumalanga escarpment area: South Africa: scientific paper
Abstract
Southern African Forestry Journal No.193 2002: 47-64
A significant positive correlation was found between NH 4 + mineralization during summer and the growth of Pinus patula (r = 0,77, p < 0,001). This process of the N cycle can therefore be considered as the rate limiting step influencing tree growth. N mineralization is controlled by a complex interaction of various site factors, and numerous correlations and interactions between NH4 + mineralization (summer) and site factors are discussed. Statistical models were developed through multiple regression techniques, to predict N mineralization from independent site variables. The in situ rates of N mineralization could be predicted with an acceptable degree of accuracy by making use of the natural log of mean annual temperature, geological substrate and total N levels in the topsoil (r2 = 0,71). These models are suitable for incorporation into existing plantation decision support systems. The significance of the response in tree growth, following fertilization with N in existing mid-rotation forest nutrition trials, was evaluated against the predictions of N mineralization using the proposed models. An inverse linear model ( r2= 0,89, p < 0,0001) was found to best describe this relationship. Additional research on the process of N mineralization in South African plantations is required to provide accurate recommendations on nutrient management for the various forest management practices currently in use.