Litter decomposition and inorganic element dynamics in a secondary rainforest at Ile‐Ife, Nigeria

Summary Leaf litter decomposition rates and variations in mineral elements content of decomposing litter of four tree species (Alstonia boonei, Funtumia elastica, Manihot glaziovii, Pycnanthus angolensis) were studied in a regrowth rainforest at Ile-Ife, Nigeria using the litter bag method. Decomposition rates of the species varied: M. glaziovii < A. boonei < F. elastica < P. angolensis. The loss in original weight of decomposing litter was linear in the early stages of decomposition but declined gradually at the later stages. No significant correlation was found between decomposition constants and initial chemical constituents of leaf litter of these species. Monthly maximum and minimum temperatures and evaporation were significantly negatively correlated with monthly weight loss. The relationship between monthly rainfall and the rainfall: evaporation ratio with monthly weight loss though positive, was not significant. It took a minimum of six months for the litter to completely decompose. Copper, iron, manganese and zinc increased in concentration with decomposition. The concentration of calcium, magnesium, potassium and sodium increased at the early stages of decomposition and subsequently decreased with decomposition. Nitrogen and phosphorus first decreased before increasing in concentration with decomposition. The elements showed different trends in their original mass remaining with decomposition and in some cases elements exhibited different trends in different species. Resume On a etudie le taux de decomposition de la litiere de feuilles et la variation du contenu en elements mineraux de la litiere en decomposition de quatre especes d'arbres (Alstonia boonei, Funtumia elastica, Manihot glaziovii, Pycnanthus angolensis) dans une foret humide rconstituee a Ile-Ife, au Nigeria, en utilisant la methode du sac de litiere. Les taux de decomposition variaient comme suit selon les especes: M. glaziovii < A. boonei < F. elastica < P. angolensis. La perte de poids original de la litiere etait lineaire au debut de la decomposition mais diminuait graduellement par la suite. On n'a pas trouve de correlation significative entre les constantes de la decomposition et les constituants chimiques initiaux de la litiere de feuilles de ces especes. Les maxima et les minima mensuels de To et d'evaporation etaient significativement negativement lies aux pertes de poids mensuelles. La relation entre les chutes de pluies mensuelles et le rapport chutes de pluies/evaporation avec la perte de poids mensuelle, bien que positive, n'etait pas significative. II fallait un minimum de six mois pour que la litiere soit completement decomposee. Les concentrations de cuivre, fer, manganese et zinc augmentaient avec la decomposition. Les concentrations en calcium, magnesiun, potassium et sodium augmentaient au debut puis diminuaient au cours de la decomposition. L'azote et le phosphore diminuaient d'abord avant d'augmenter avec la decomposition. Les elements montraient differentes tendances dans ce qui restait de la masse originale au cours de la decomposition, et dans certains cas, les elements montraient des tendances differentes selon les especes.