Nutrient contents and rate of litter decomposition were investigated in Leucaena leucocephala plantation in the University of Agriculture, Abeokuta, Ogun State, Nigeria. Litter bag technique was used to study the pattern and rate of litter decomposition and nutrient release of Leucaena leucocephala. Fifty grams of oven-dried leaf litter of the species was weighed into 0.2 mm mesh litter bag, 35 cm × 25 cm in size, these bags were closed at all ends. Eighteen litter bags were used for the studies. The litter bags were numbered and placed on the field (above ground) on 26th April 2005. Three bags were retrieved randomly from the field at 20-day intervals for 120 days. The nutrient concentration in L. leucocephala followed the trend N > P > Mg > Ca > K > Na for leaf litter and seed components. Nutrient concentration in twigs and pods ranked N > Mg > P > Ca > K > Na. Among all the litter components, leaf litter contributed more nutrients, especially nitrogen, than other litter components. High potassium concentration during the dry season was due to lack of rainfall to leach out the element. Lower magnesium content in leaf litter was due to chlorophyll decay. High N-flux reflected the quantity and quality of nitrogen in the soil. Mass loss was significantly correlated with calcium (P < 0.05). At 120 days, 80% of the litter had decomposed; this implies that decomposition rate was at 0.6% per day. A net immobilization of all the nutrient elements at 20 days was due to lack of rainfall to leach out the nutrients. High rate of decomposition at the early stage was due to less moisture content in the soil and high temperature. Litter decomposed more during the wet season than the dry season.

Variations in 25 populations of Luffa aegyptiaca L. in southwestern Nigeria and their possible causes were studied. The variations were most pronounced in the leaf, especially in texture, invagination, area, and dry weight. Shoot and fruit dry weights also showed considerable variation. While mean seed dry weight showed remarkable constancy in the populations studied, mean seed number per fruit varied greatly.Populations growing in acid soil with low nutrient content had deep leaf invaginations, small leaf areas per shoot, and small leaf, shoot, and fruit dry weights, while populations growing in neutral or basic soils with high nutrient content had shallow leaf invaginations, large leaf area per shoot, and large leaf, shoot, and fruit dry weights.When seeds from a population with deep leaf invagination and small leaf area were grown in soil from the site of a population with shallow leaf invagination and large leaf area, the resulting plants developed the characteristics of the second population. The reciprocal procedure gave a similar result. The variations in soil were thought to be responsible for the variation noted in leaf morphology, size, and weight and for variation in shoot and fruit dry weights. Light was partially responsible for the variations in the leaf colour and in the prominence of leaf veins.

SummaryLitter was collected from 18‐year‐old Tectona grandis (teak) and 13‐year‐old Terminalia superba (afara) planted at various square spacings at Gambari Forest Reserve, Southwestern Nigeria. Litter was collected throughout the year in both species with the rate of fall being particularly high in the dry season in the case of teak and in the wet season in the case of afara. The peak of litter fall in teak may be related to the degree of desiccation or water stress and that of afara to diurnal temperature range and rainfall. The mean annual litter production (kg/ha) in Tectona grandis amounted to 5067, 4688, 4998 and 5196 in square spacings (m2) of 1·37, 1·98, 2·9 and 3·96, respectively. The mean annual litter production (kg/ha) in Terminalia superba amounted to 4157, 3873, 3108 and 4032, in square spacings (m2) of 1·8, 2·8, 4·2 and 6·1, respectively. There were no significant differences in the amount of litter produced and nutrient contents between the various spacings in both species.RésuméOn a collecté la litière sous des Tectona grandis (Teak) de 18 ans et des Terminalia superba (Afara) de 13 ans, plantés à des écartements variables dans la Réserve de Gambari Forest, au sud‐ouest du Nigéria. On a récolté la litière tout au long de l'année pour les deux espèces, les chutes étant particulièrement importantes pendant la saison sèche pour le ‘teak’ et en saison des pluies pour l“afara‘. Le pic de la chute des feuilles du ’teak‘ peut être lié au degré de dessiccation ou au manque d'eau, et celui de l”afara’à la temperature diurne et aux chutes de pluie. La production annuelle moyenne de litière (en kg/ha) de Tectona grandis atteint 5067, 4688, 4998, et 5196 pour des espacements (en m2) de 1,37, 1,98, 2,9, et 3,96 respectivement. Pour Terminalia superba, ces chiffres (en kg/ha) sont de 4157, 3873, 3108 et 4032 pour des espacements (en m2) de 1,8, 2,8, 4,2 et 6,1 respectivement. Il n'y a pas de différence significative dans les quantités de litière produites et le contenu en éléments nutritifs selon la variation d'espacement, pour les deux espèces.