Leaf decomposition and flammability are largely decoupled across species in a tropical swamp forest despite sharing some predictive leaf functional traits.

Decomposition and fire are major carbon pathways in many ecosystems, yet potential linkages between these processes are poorly understood. We test whether variability in decomposability and flammability across species are related to each other and to key plant functional traits in tropical swamp forests, where habitat degradation is elevating decomposition and fire regimes. Using senesced and fresh leaves of 22 swamp tree species in Singapore, we conducted an in situ decomposition experiment and a laboratory flammability experiment. We analysed 16 leaf physical and biochemical traits as predictors of decomposability and components of flammability: combustibility, ignitability and sustainability. Decomposability and flammability were largely decoupled across species, despite some shared predictive traits such as specific leaf area (SLA). Physical traits predicted that thicker leaves with a smaller SLA and volume decomposed faster, while various cation concentrations predicted flammability components, particularly ignitability. We show that flammability and decomposability of swamp forest leaves are decoupled because flammability is mostly driven by biochemical traits, while decomposition is driven by physical traits. Our approach identifies species that are slow to decompose and burn (e.g. Calophyllum tetrapterum and Xanthophyllum flavescens), which could be planted to mitigate carbon losses in tropical swamp reforestation.

Will oil palm's homecoming spell doom for Africa's great apes?

Expansion of oil palm plantations has led to extensive wildlife habitat conversion in Southeast Asia [1]. This expansion is driven by a global demand for palm oil for products ranging from foods to detergents [2], and more recently for biofuels [3]. The negative impacts of oil palm development on biodiversity [1, 4, 5], and on orangutans (Pongo spp.) in particular, have been well documented [6, 7] and publicized [8, 9]. Although the oil palm is of African origin, Africa's production historically lags behind that of Southeast Asia. Recently, significant investments have been made that will likely drive the expansion of Africa's oil palm industry [10]. There is concern that this will lead to biodiversity losses similar to those in Southeast Asia. Here, we analyze the potential impact of oil palm development on Africa's great apes. Current great ape distribution in Africa substantially overlaps with current oil palm concessions (by 58.7%) and areas suitable for oil palm production (by 42.3%). More importantly, 39.9% of the distribution of great ape species on unprotected lands overlaps with suitable oil palm areas. There is an urgent need to develop guidelines for the expansion of oil palm in Africa to minimize the negative effects on apes and other wildlife. There is also a need for research to support land use decisions to reconcile economic development, great ape conservation, and avoiding carbon emissions.