LEAF LITTER DECOMPOSITION OF EVERGREEN AND DECIDUOUS <em>DILLENIA</em> SPECIES IN HUMID TROPICS OF NORTH-EAST INDIA

Abstract

Litterbags were used to study the decomposition of abscissed leaves of two tree species belonging to one genus, Dillenia indica (evergreen) and Dillenia pentagyna (deciduous) in a humid tropical forest of Arunachal Pradesh, north-eastern India. Hundred per cent decomposition was observed after 150 days for D. indica and 120 days for D. pentagyna. The leaf litter decomposition of the two species showed different temporal trends; decomposition of D. indica leaf litter showed an initial lag phase, followed by a rapid decay phase and a final slow decay phase, while D. pentagyna leaf litter decomposed rapidly initially up to 60 days, but declined sharply afterwards. A composite linear equation showed a good fit for the observed decay patterns. Theannual decay constant (k) was significantly higher (p < 0.01) for D. pentagyna (9.11) than for D. indica (6.15).
The nutrient concentrations differed significantly between species. The mature as well as decomposing leaves had more nutrient concentrations compared with the abscissed leaves (leaf litter). The retranslocation of nitrogen before abscission was greater in D. indica, while percentage phosphorus retranslocation was similar in both species. The nutrient release patterns indicated that the N and P mineralisation of D. pentagyna leaf litter is faster compared to D. indica, as associated with their respective decay rates.