Nutrient Retention by Savanna Ecosystems: I. Retention in the Absence of Fire

Abstract

(1) The soil-water percolation regime and the concentration of Ca, Mg, K, Na and P in the soil solution were determined daily at five soil depths beneath three types of savanna in Belize, Central America, during wet- and dry-season condition, in the absence of fire. The input of these elements in bulk precipitation and throughfall was also measured. (2) The nutrient concentration of the surface-soil solutions were consistently higher than those of the bulk precipitation, throughfall, and those in deeper soil layers. (3) Despite this difference and the occurrence of frequent percolation, no evidence of any acute movement of nutrients to deeper soil layers was detected. This is attributed to the capacity of the soil to immobilize rapidly any large quantities of nutrients appearing in solution. (4) There was no evidence that root uptake was an important mechanism of short-term nutrient retention at these sites. (5) We conclude that these oligotrophic soil-vegetation systems are highly retentive of nutrients and are not subject to large short-term losses in the absence of fire. Reliable estimates of absolute nutrient fluxes from such systems would require long-term monitoring of fully enclosed lysimeters.