Nutrient Retention by Savanna Ecosystems: II. Retention After Fire

Abstract

(1) The daily patterns of precipitation, soil water movement, and the concentration of nutrient elements in soil solutions at five depths were examined beneath three types of savanna in Belize, Central America, after burning. (2) Large increases in the concentration of some elements were recorded in the rooting zones in all types, but these disappeared within 1 week. Despite much percolation, no comparably large increases were recorced in solution concentrations deeper in the soil. (3) A comparison of the mean element concentrations after this post-fire peak with concentrations before the burn, and during an equivalent period 1 year earlier, showed many significant increases in concentration in the topsoil, but few increases in deeper soil. Ca and P appear to have been most effectively retained, Mg and K less so, and Na the least. (4) The results confirm the resistance of the three savanna types to acute losses of nutrients due to leaching after fire, and it is suggested that greater losses are likely to result from surface run-off during rainstorms. However, repeated burning has not significantly reduced the fertility of the surface soil, but has significantly increased the amounts of Ca and Mg in the soil exchange complex.