Leaf litter decomposition in different tree species of multifunctional agroforestry: decay constant and initial litter chemistry

Litter decomposition is an important process that maintains soil fertility and enriches soil organic matter in agroforestry. They are highly influenced by tree density, age, timing, the quantity of litterfall, soil organisms, the chemical nature of the litter, and environmental conditions. An experiment was conducted in a multifunctional agroforestry model established in 2018 at Forest College & Research Institute, Mettupalayam, India. Based on litter fall, among 25 tree species, seventeen species were chosen to study litter decomposition and the relationship between decay rates, initial litter chemistry, and soil properties. A total of 153 litter bags each of 20 g samples were placed in soil and retrieved at 60, 120, 180, and 360 days to observe litter mass remaining and further analysed in laboratory for its properties. The results of decay rates revealed that the litter of Neolamarckia cadamba (3.03), Tectona grandis (2.85), Annona muricata (2.81), Moringa oleifera twigs (1.10) decomposed fast whereas Calophyllum inophyllum (0.86), Pterocarpus santalinus (1.02) and Melia dubia twigs (1.10) exhibited the lowest rate of decomposition. Calophyllum inophyllum takes 3.50 years while Neolamarckia cadamba takes only 0.99 years for decomposition of 95% of leaf litter. One-way ANOVA revealed significant differences among 17 tree species for initial leaf litter chemistry. Significantly negative correlation with lignin (-0.65) and lignin: nitrogen ratio (-0.56) implies that these parameters are strong predictors of the decomposition process. The soil organic carbon and other soil properties (pH, EC, N, P, K) was higher in the upper surface layer followed by a decreasing trend in the other soil depths. Holistically, diversified cropping mixture in multifunctional agroforestry contributed in improving soil fertility through decomposition.