Explaining niche separation in tropical forests: feedbacks between root-fungal symbioses and soil phosphorus partitioning

High diversity is a striking feature of almost all tropical forests, which provide numerous important ecosystem functions, and contribute to the resilience of communities in response to global change. Although several mechanisms have been proposed to explain the origin and maintenance of tropical forest diversity, recent theoretical work suggest that resource partitioning for soil phosphorus (P) is likely to be one of the main contributors to tropical plant diversity and coexistence. However, we currently lack vital experimental evidence to test this hypothesis, which requires understanding the relationships among mycorrhizal plant and fungal diversity, and soil P fractions in these systems, and how these associations relate to P utilisation. In this proposal, we will therefore determine the network of interactions among plants and mycorrhizal fungi in the field, and show using manipulation experiments whether this is related to edaphic factors, and in particular the composition and structure of the soil P pool. This aim requires coupling a comprehensive and unique dataset of spatial analyses of plant diversity with new analyses of mycorrhizal fungal diversity and soil nutrient pools in pristine tropical forest, and novel manipulation experiments. This project will show whether, despite overall nutrient limitation, the diversity of a mineral fraction in the soil is a driver of plant hyperdiversity. This will make a step-change in our understanding of the role of soil biodiversity in niche separation.
The project will provide mechanistic insight into the maintenance of hyper-diverse plant communities and make a step-change in our understanding of the role of soil biodiversity in niche separation within tropical tree communities. It targets NERC priority areas in biodiversity, and will aid stakeholders who are charged with managing plant and soil biodiversity and the goods and services provided by tropical ecosystems (see Pathways to Impact).

Our project will help understand the mechanisms that maintain the remarkable richness of tree species found in pristine SE Asian tropical forests. It will also highlight the importance of above-below ground interactions and encourage conservation organisations to have broad perspectives on how to conserve these keystone ecosystems. Because it impacts on several aspects of tropical forest ecology and sustainability it will be of interest to a broad range of end-users and stakeholders.

1. Politicians in Malaysia and the UK who seek to find a balance between timber production and forest sustainability

Examples: The Sabah State Government is committed to sustainable forest management through it current forestry policy and will benefit from evidence-based understanding of the fundamental mechanisms that determine biogeochemical cycling and maintenance of forest biodiversity. We will seek to inform and influence these policies through on-going interactions with the Sabah Forestry Department and contributions to local media. Similarly the UK and devolved governments have policies to limit procurement of tropical timber to well-managed forests and will benefit from blue-skies research that provides the evidence base for an understanding of the determinants of tropical forest sustainability.

2. Private sector companies who seek to exploit lowland tropical forests for commercial reasons

Examples: Sustainable timber production from forests is dependent on maintenance of functioning biogeochemical cycles that are themselves heavily reliant on plant-microbial interactions. Although the role and importance of mycorrhizal interactions will not be well-known to timber producers, they will be understood by technical staff in forest nurseries who generate seedlings for re-planting programmes. To reach this audience we will target training in mycorrhizal inoculation techniques for staff of the nurseries that supply seedlings for large-scale rehabilitation of degraded logged forests adjacent to the Danum Valley Conservation Area.

3. National and international organisations who have remits for conservation of tropical diversity, e.g. WWF, International Mycological Association, International Union for Conservation of Nature.

Examples: We are already active in the IUCN's Species Survival Commission, and our research will therefore inform the development of conservation assesments and advice that feeds into the international conservation policy agenda. Data on the identity, role and conservation status of tropical fungi are currently very limited, therefore the new data from our project will achieve a high profile in discussions around conservation policy for tropical fungi. Indirectly, our work will also be relevant to the needs of those with interests in understanding the causes and importance of plant diversity more generally, including the UK Biodiversity Research Advisory Group (UK BRAG) who highlight the urgent need to understand the link between plant and microbial functional diversity.

4. The Sabah Tourism Board and the Sabah Foundation

Examples: Tourism policy in Sabah is heavily based on its remaining patches of primary tropical forest such as the DVCA. We will generate display and education materials for the Borneo Rainforest Lodge and the Rainforest Discovery Centre summarising research findings in a manner accessible to local and foreign tourists.

5. The general public through educational activities associated with the project (see Pathways to Impact)

Examples: The future of tropical rainforests is of concern to the general public in the UK and Malaysia and publicity for forest destruction can elicit negative responses, while support for NGOs and organisations supporting conservation and restoration of tropical forest remains strong. We will access these groups using our website, contributions to media, popular articles, talks and interactive sessions and events targeting public engagement with science.