Rethinking Tree Growth Response to Extreme Drought on the Southeastern Tibetan Plateau
Rethinking Tree Growth Response to Extreme Drought on the Southeastern Tibetan Plateau
by Ng Kam Ping Lily, The University of Hong Kong
Supervised by Prof. Jinbao Li, Department of Geography
Abstract
The Tibetan Plateau has experienced rapid climate change since industrial revolution, which has dramatically impacted regional pristine forests. It is imperative to understand different species’ responses to more frequent drought events under anthropogenic influence, specifically on southeastern part of TP, in which climatic variability is noticeably dramatic. However, there is a noticeable lack of consensus regarding tree growth response to extreme drought on the southeastern Tibetan Plateau, specifically on genera of Juniper and Fir. This study focused on Abies georgei Orr and Sabina tibetica and analysed their response to drought using standardized tree-ring index and the Palmer Drought Severity Index (PDSI). Sampling sites encompassed highland area, 3610 m a.s.l. and 3970 m a.s.l, while source of PDSI is set in nearest grid to the sampling sites (29º 00’ N – 29º 5’N, 101º00’ E – 101º5’E). Results about the effect of PDSI over tree-rings indicate that micro-climate creates species-specific adaptation to drought suppression in the respective altitude levels. On the other hand, physiological responses of fir and juniper create themselves a contrasting growth condition under drought. Fir was found to be more adaptable to anthropogenic climate change due to their isohydric biology whereas juniper is found imposing itself a bigger threat of physiological collapse. These exceptional findings from the two species point out a new approach to evaluate forest growth in the context of anthropogenic climate change by understanding the mechanism behind changes in tree resilience.
Keywords: Palmer Drought Severity Index (PDSI), Tree-ring, Southeastern Tibetan Plateau, isohydric/ anisohydric physiology, altitude
