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

Abstract

Understanding the long-term impact of projected climatic changes on tropical rainforests is critical given their central role in the Earth's system. Palaeo-records that document ecological responses to comparable climatic changes in the past 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, including fossil pollen, charcoal, and stable isotopes, to model long-term vegetation responses of Dipterocarp forest, including its dominant tree family Dipterocarps, to precipitation, fire and nutrient variability over time. Our results show a positive relationship between Dipterocarp pollen accumulation rates (PARs) and leaf wax hydrogen isotope values, which suggest a negative effect of drier conditions on the abundance of Dipterocarp trees. Furthermore, we find a positive relationship between Dipterocarp PARs and the proxy for phosphorus availability, which suggests phosphorus controls the productivity of this keystone tree group 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.

What is in store for the tropical forests of Indo‐Australia?

“…In a new study published in this issue of New Phytologist , Prohaska et al . (2023; 2513–2529) use a 1400 yr old sedimentary record from the Philippines to determine long‐term vegetation responses of lowland tropical forest. Specifically, the study examines the pollen accumulation rates (PARs), leaf wax hydrogen isotopes, and nitrogen and phosphorous availability from sediment cores taken from the Bulusan Lake in the Bulusan Volcano National Park where logging has been strictly regulated.…”