The effects of forest degradation on trophic interactions and elemental fluxes in an experimental landscape, Malaysian Borneo
Despite occupying only 12% of Earth’s surface, tropical forests contain disproportionate biodiversity, contribute approximately 40% of terrestrial net primary productivity, and contain 20% of global carbon biomass. In parallel, tropical forests experience extreme destruction and degradation, leading to a pressing need to understand the value of degraded forest. Recent work suggests that degraded forests which retain a high percentage of native tree cover, or are in late stage recovery, can support levels of species richness close to those of intact forests. However, the impacts of tropical forest degradation on ecosystem functions remain unclear due to a paucity of studies. Among the key functions that may be modified by habitat degradation is the flux of energy and nutrients through an ecosystem. In chapter two, I determined insectivorous bat community response to short- and long-term pressures, climatic and logging respectively. In the second and third chapters. In the third and fourth chapters I examined how forest degradation influenced bat resource use, food web structure, and associated ecological functions. I focused on summarising complex interactions between bats, their prey and basal resources by analysing naturally abundant isotope compositions. Initially, I focused on shifts across a narrow degradation gradient, and found that both landscape- and localscale traits correlated with changes to isotopic niche and trophic position, respectively. I extended this investigation to examine patterns across both logged and primary forest, and examined how long term habitat changes correlated with dietary shift. Furthermore, I explored how short-term environmental stress interacted with established gradients of habitat quality. In the last chapter, I undertook a 15nitrogen-tracer mesocosms study to investigate dung beetle effects upon nitrogen cycling in tropical soils, facilitating future studies on the response of nitrogen processes to environmental change. This research assists in identification of landscape elements which should be favoured by management policies in order to retain ecosystem functioning.
- Theses