Litterfall, nutrient-fall and production in an Acacia albida woodland in Zimbabwe

Abstract

Litterfall was recorded for one year in Acacia albida woodland in Mana Pools National Park, Zimbabwe. Leaves fell throughout the year, but leaf-fall rate peaked in the wet season. Litterfall was 1.5 t ha⁻¹ year⁻¹, comprising 50% leaves, 20% fruits, 17% ‘fine’ material (mainly frass), 4% flowers and 9% wood and bark. Net above ground production by A. albida trees was 1.7 t ha⁻¹ year⁻¹, including leaf production of 1.0 t ha⁻¹ year⁻¹, twig production of 0.3 t ha^-1 year⁻¹ and fruit production of 0.3 t ha⁻¹ year⁻¹. Insects consumed about 26% of leaf production. Net above ground herbaceous production was estimated from rainfall data using regression equations: it was 6.8 t ha⁻¹ year⁻¹ for annual grasses and 2.8 t ha⁻¹ year⁻¹ for forbs. Net above ground primary production in A. albida woodland was 11.3 t ha⁻¹ year⁻¹. The seasonal variations in the nitrogen, phosphorus, potassium, magnesium and calcium concentrations of different A. albida litter components were recorded. The estimated falls of N, P, K, Ca and Mg were 31.1, 2.1, 9.8, 15.0 and 3.4 kg ha⁻¹ year⁻¹ respectively.