“How biodiversity and forest succession affect ecosystem functioning: carbon and nutrient cycling via litterfall in Singapore”
Teo Xian Yao Aloysius
Dept. of Biological Sciences
National University of Singapore
Tue 26 Aug 2014: 3.30pm
DBS Conference Room (S3 level 5)
Supervisor: Assoc Prof Theodore A. Evans
All are welcome
Abstract: – Pervasive deforestation and land-cover changes within the tropics have led to the formation of large tracts of tropical secondary forests. While the loss of species within secondary forests is well-recognised, it remains unclear if the decline in biodiversity is associated with a decline in the level of ecosystem functioning. It is imperative that the provision of essential ecosystem processes and services within secondary forests – in particular carbon and nutrient cycling, be better characterised.
The production and decomposition of vegetative litter is a vital ecosystem process, forming one of the main pathways for carbon and nutrient cycling. These processes are regulated by a range of biotic and abiotic factors – the diversity of the decomposer community, the diversity of plants, the chemical quality of litter produced and the physical environment. However, few studies have characterised the mechanistic linkages of these factors with the litterfall and decomposition processes in secondary forests.
In Singapore, secondary forests dominate the forested landscape. However, there remains a paucity of studies to describe the secondary forests from a functional perspective. Specifically, no studies have been conducted to assess the efficiency of carbon and nutrient cycling via the litterfall and decomposition processes. Henceforth, this study aims to investigate the relative roles of forest succession, the decomposer community, and abiotic factors in determining fine litterfall productivity and litter decomposition rates, as well as the associated fluxes of carbon and nutrients. The phenological patterns of litterfall will be identified too.
Preliminary results revealed that litterfall productivity in mature secondary forests did not approach that of primary forests, despite the former having more than a century of regeneration. Wood wastelands, which had less than 50 years of regeneration, produced significantly more fine litterfall and were characterised by a markedly elevated level of nitrogen and phosphorus cycling.
The monthly production of fine litterfall was found to exhibit an inverse relationship with precipitation. Reproductive litter production did not appear to be influenced by precipitation, except in primary forests, where the drought-triggered masting of Dipterocarps likely contributed to a spike in the quantity of reproductive litter recorded.
Decomposition rates of fine litter remained relatively similar across forest types. Litter nitrogen content and soil moisture levels were strong determinants of decomposition rates. Further studies will investigate the dynamics of coarse litter decomposition and evaluate the relative roles of microbial and invertebrate decomposers experimentally.