Long-Term Ecological Responses of a Dipterocarp Forest to Climate Changes and Nutrient Availability

Understanding the long-term impact of projected climate change on tropical rainforests is critical given their central role in the Earth’s system. Palaeoecological records can provide a valuable perspective on this problem. Here we examine for the first time the effects of past climatic changes on the dominant forest type of Southeast Asia – Dipterocarp forest. We use a range of proxies extracted from a 1,400-year-old lacustrine sedimentary sequence from north-eastern Philippines to model long-term vegetation responses of Dipterocarp forest, including its dominant tree group Dipterocarps, to changes in precipitation, fire and nutrient availability over time. Our results show a positive relationship between Dipterocarps pollen accumulation rates (PARs) and leaf wax hydrogen isotope values, which suggests a negative effect of drier conditions on Dipterocarp tree abundance. Furthermore, we find a positive relationship between Dipterocarp PARs and the proxy for phosphorus availability, which suggests phosphorus controls the productivity of these keystone trees on longer time scales. Other plant taxa show widely varying relationships with the abiotic factors, demonstrating a high diversity of functional responses. Our findings provide novel insights into Dipterocarp forest responses to changing climatic conditions in the past, and highlight potential impacts of future climate change on this globally important ecosystem.