Leaf litter decomposition of dominant tree species of Namdapha National Park, Arunachal Pradesh, northeast India

Abstract

Rates of weight loss and nutrient (N and P) release patterns were studied in the leaf litter of the dominant tree species (Ailanthus grandis, Altingia excelsa, Castanopsis indica, Duabanga sonneriatioides, Dysoxylum binectariferum, Mesua ferrea, Shorea assamica, Taluma hodgsonii, Terminalia myriocarpa and Vatica lancefolia) of a tropical wet evergreen forest of northeast India. Nitrogen and phosphorus mineralization rate and decay pattern varied significantly from species to species. In general, the decay pattern, characterized by using a composite polynomial regression equation, exhibited three distinct phases of decay during litter decomposition-an initial slow decay phase (0.063% weight loss day -1 ), followed by a rapid decay phase (0.494% weight loss day -1 ) and a final slow decay phase (0.136% weight loss day -1 ). The initial chemical composition of the litter affected decomposition rates and patterns. Species like D. sonneriatoides, D. binectariferum, and T. hodgsonii with higher N and P content, lower carbon and lignin content, and lower C:N ratio and lignin:N ratio exhibited relatively faster decomposition rates than the other species, for example M. ferrea, C. indica and A. grandis. A slow decay rate was recorded for species such as M. ferrea, C. indica, and A. grandis. The initial N and P content of litter showed significant positive correlations with decay rates. Carbon and lignin content, lignin:N, and C:N showed significant negative correlations with decay rates. Soil total N and P, and rainfall, soil temperature, and soil moisture had positive correlations with decay rates. The rapid decomposition rates observed in comparison with other different forest litter decay rates confirm that tropical wet evergreen forest species are characterized by faster decomposition rates, indicating a faster rate of organic matter turnover and rapid nutrient cycling.

Foliar Litter Decomposition of Four Dominant Tree Species in the Hollongapar Gibbon Wildlife Sanctuary, Assam, North East India

“…Likewise, Jamaludheen and Kumar 27 reported a positive yet non-significant relation of soil moisture with residual litter weight. Soil total N also showed a positive correlation with decay rate, which corroborates with reports by other workers 6,32 . According to Liu et al 32 , N availability is essential for litter decomposition, as increased soil N can cause changes in the soil nutrient level and decomposers as well as the quality of decomposing litter.…”

“…The rate of decomposition of foliar litter was high in the study site, which was revealed from the fairly high value of annual decomposition constant (k). The recorded value (k year -1 ) in the present study is comparable with those of Barbhuiya et al 6 (1.04-5.37), Upadhyaya et al 21 (1.3-8.19). However, it is relatively higher than ranges reported by several others workers 11,20,24,25 .…”

“…The recorded values of primary litter quality characteristics, i.e. C, N and ratios of the two parameters (C/N) observed in the present study are within the reported range from various studies 6,11,24 . The initial N concentration was positively correlated (r = 0.738) with the decay rate constants of all tree species (Table 2).…”

“…Positive correlation with rainfall, air temperature, soil moisture and soil temperature reveals high rate of decomposition in hot, rainy season and low rate during cool, dry periods. Various reports also support such observations 6,25,31 . Likewise, Jamaludheen and Kumar 27 reported a positive yet non-significant relation of soil moisture with residual litter weight.…”

“…Four dominant tree species of the forest, based on phytosociological study by Sarkar Freshly fallen leaves of these selected species were collected and 10 g of air-dried leaf litter samples were placed within nylon mesh bag of 15 cm  15 cm having mesh size of 2 mm, good enough to avoid major losses of litter samples but allow aerobic microbial activity and free entry of small soil organisms 6 . The litter bags were placed on the soil surface (total 240; 4 species  5 replicates  12 months) just below the litter layer of the forest from June 2011.…”