Capitalising on a mass fruiting event to assess the long-term sustainability of rainforest remnants.

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The requirement to feed a rapidly increasingly human population whilst maintaining ecosystem services and reducing biodiversity losses has led to an urgent need to design more sustainable agricultural landscapes. This is particularly relevant in SE Asia where oil palm plantations are replacing hyper-diverse tropical rainforest. Current policies for the sustainable cultivation of oil palm (an important source of edible vegetable oil) require the retention of rainforest fragments within plantations. However, the assumption that these forest fragments can continue to support high biodiversity, maintain their viability, and regenerate over time has not previously been tested. Thus one of the primary criteria for sustainability is essentially untested, and forms the basis of this proposal.SE Asian rainforests are unique in being dominated by Dipterocarpaceae trees which reproduce irregularly (at intervals from 1 to many years) but synchronously in mass fruiting events. One of these unpredictable mass fruiting events has recently been initiated on Borneo, and provides a rare opportunity to study dipterocarp reproduction in rainforest fragments. Dipterocarp trees are a vital component of rainforest ecosystems in SE Asia, and hence any changes that affect dipterocarps are likely to have considerable knock-on impacts for rainforest biodiversity. Our recent data show an absence of dipterocarp seedlings in small forest fragments even when mature dipterocarps are present, raising a serious concern of reproductive failure of dipterocarps in fragments. The recently-initiated mass fruiting event provides us with an opportunity to explore potential mechanisms leading to reproductive failure and/or recruitment failure in forest remnants. The main objective of this project is to: (1) examine how forest fragmentation affects dipterocarp reproduction, (2) relate reproductive rates to biotic and abiotic changes arising from forest fragmentation (altered microclimates, habitat quality, predation), and (3) assess whether dipterocarp species are equally sensitive to impacts of forest fragmentation. The proposed work will provide the first investigation of the long-term viability of forest remnants in tropical agricultural landscapes. The project will address fundamental questions about reproduction in dipterocarp trees under altered abiotic and biotic conditions, as well as producing results of considerable practical value for policy makers. It will form the basis for new research in future focussed on understanding the impacts of habitat degradation and fragmentation on biodiversity, and contribute to scientific evidence to inform the debate on developing effective conservation and sustainability strategies.