Leaves litterfall and nutrient inputs from four multipurpose tree/shrub species of homegarden agroforestry systems

Abstract

BackgroundAs compared to natural forest ecosystems, soils under agroecosystems are more subjected to changes in physical and biochemical attributes. But, tree species that are retained and/or planted on these agroecosystems replenish soil fertility through the influence of leaves litterfall quantity and quality. Tree species-related differences in the quantity and seasonality of leaves litterfall and the associated amounts of annual returns of nutrient elements were assessed from four multipurpose tree/shrub species (Erythrina brucei Schweinf, Cordia africana Lam., Grevillea robusta R. Br. and Malus sylvestris Mill.) in homegarden agroforestry systems. Five replicates of two leaf litterfall traps per species were randomly positioned beneath the subcanopy area for 12 months, totaling 40 litterfall traps distributed among the four species.ResultsThe results of this study suggested that total annual leaves litterfall varied significantly among species (ranging from 171.18 to 962 kg ha− 1), with the combined per tree mean monthly (28.13 kg tree− 1), per tree annual (331.10 kg tree− 1 year− 1) and per area basis total annual (9439.33 kg ha− 1) leaves litterfall production. A clear seasonal leaves litterfall pattern with varying peaks was observed for the multipurpose tree/shrub species in the present study, with a bimodal distribution pattern for E. brucei and C. africana and a unimodal distribution pattern for G. robusta and M. sylvestris. Similarly, both the concentrations and inputs of nutrients from the leaves᾽ litterfall showed considerable variations among species (p < 0.05). Among the investigated species, C. africana and E. brucei were found to be the best in terms of carbon (C) and nitrogen (N) return, G. robusta the best in terms of phosphorous (P) return, and C. africana as well best for potassium (K) return. The combined mean annual nutrient inputs recorded for all the species were 3125.32 kg C ha− 1 year− 1, 149.70 kg N ha− 1 year− 1, 54.86 kg K ha− 1 year− 1, and 3.56 kg P ha− 1 year− 1.ConclusionsLeaves litterfall amount differed among tree species as influenced by tree species characteristics (canopy area, diameter at breast height (DBH), height), but no cause-effect relationship with age and climate (monthly precipitation and temperature).