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Title: Ecological responses of a Philippine dipterocarp rainforest to late holocene climatic changes
Author: Prohaska, Ana
ISNI:       0000 0004 6421 5537
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2016
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Tropical rainforests comprise the world's oldest and most biodiverse biome, covering over 10% of Earth surface and providing livelihoods for over 300 million people. The upcoming consequences of anthropogenic climate change on tropical rainforests remain poorly understood. This is particularly true of the lowland tropical rainforests of Southeast Asia, aka Dipterocarp rainforests, in relation to the projected changes in El Niño/Southern Oscillation dynamics (ENSO). To address this important knowledge gap, this thesis aims to elucidate the ecological responses of Dipterocarp rainforests to past ENSO changes using a sediment-based multiproxy palaeoecological approach. A suite of fossil proxies (e.g. lipid biomarkers, pollen, charcoal) from a Philippine lacustrine sequence spanning the last 1,400 years were used to generate records of precipitation, fire, nutrient availability and plant dynamics. These records were used to explore the effects of major environmental drivers on the structure and functioning of Dipterocarp rainforests, specifically their dominant tree family, Dipterocarpaceae, and their pioneer plant taxa. The results suggest that Dipterocarp rainforests have been exposed to a prolonged period of enhanced ENSO regime during the second half of the Little Ice Age (~AD 1650-1900), yet there was no apparent effect of this climatic variability on the biomass of Dipterocarp trees. In contrast, the findings indicate that major fluctuations in phosphorus availability at the study site have had a significant influence on the biomass of Dipterocarp trees, though it remains uncertain which aspect of their biomass was primarily affected. Finally, my results propose that changes in ENSO conditions can significantly affect the abundance of pioneer taxa, with the nature and magnitude of that effect depending heavily on the level of fire activity. This thesis examined for the first time the vegetation responses of Dipterocarp rainforests to large-scale climatic changes in the past. The findings presented here provide new insights into the likely structure and functioning of this globally important ecosystem in a warming world, and provide a context for understanding its resilience to current and future environmental change.
Supervisor: Willis, Kathy J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available