Ximeng Li

Candidature

PhD Candidate

Thesis Title

Identifying regions of high drought mortality risk for tree species in NSW

Research Project

Drought induced forest die-off is a world-wide phenomenon and is expected to be more widespread in the near future due to increased severity and frequency of dry period. Climate of origin shapes plant functional traits phenotypically and genetically, leading to difference in plant drought resilience and resistance. Examining drought response of plants differ in provenance can add to our understanding on the mechanisms underlying drought induced tree mortality, and also has important implications on plant conservation and management. In this project, we will select different species native to diverse ecosystems with divergent climates across NSW. Our overarching objective is to investigate the variation of plant functional traits to drought stress, thereby informing and advancing model predictions. Specifically, we ask how plant hydraulic traits respond during drought stress and, in addition, if such variation relates to climate of origin. To this end, three experiments are developed. Firstly, a common garden experiment is conducted to examine traits variation and test if such variation is related to climate of origin. Secondly, we use a glasshouse based experiment to examine the response of stomatal conductance to environmental factors, as stomata play a central role in linking plants and atmosphere. Emphasis will be placed on the dependence of stomatal conductance on leaf water potential and soil water content, which is one of the main controversy among diverse models of stomatal conductance. Finally, a field experiment will be conducted to certify the results obtained in the first experiment with mature trees. In summary, the results of this project will guide us towards a better understanding of mortality mechanisms and inform models to identify regions of high drought-mortality risk in NSW.

Research Images

Branch dieback of Sydney pepper mint (Eucalyptus piperita) of Blue mountain area due to winter drought in 2017.

Common garden experiment aims to identify the variation of plant functional traits across species.

Photos showing gas exchange measurement (left panel) and stem hydraulics measurement (right panel).

Publications

Li X, Xu C, Li Z, Feng J, Tissue DT, Griffin KL, (2019) 'Late growing season carbon subsidy in native gymnosperms in a northern temperate forest', Tree physiology, vol.39, no.6, pp 971-982

Li XM, Blackman CJ, Choat B, Rymer PD, Medlyn BE, Tissue DT, (2019) 'Drought tolerance traits do not vary across sites differing in water availability in Banksia serrata (Proteaceae)', Functional Plant Biology, vol.46, no.7, pp 624-633

Li XM, Blackman CJ, Peters JMR, Choat B, Rymer PD, Medlyn BE, Tissue DT, (2019) 'More than iso/anisohydry: Hydroscapes integrate plant water use and drought tolerance traits in 10 eucalypt species from contrasting climates', Functional Ecology, vol.33, no.6, pp 1035-1049

Li XM, Blackman CJ, Choat B, Duursma RA, Rymer PD, Medlyn BE, Tissue DT, (2018) 'Tree hydraulic traits are coordinated and strongly linked to climate-of-origin across a rainfall gradient', Plant Cell and Environment, vol.41, no.3, pp 646-660

Li XM, Blackman CJ, Rymer PD, Quintans D, Duursma RA, Choat B, Medlyn BE, Tissue DT, (2018) 'Xylem embolism measured retrospectively is linked to canopy dieback in natural populations of Eucalyptus piperita following drought', Tree Physiology, vol.38, no.8, pp 1193-1199

Li Z, Li X,  Rubert-Nason KF, Yang Q, Fu Q, Feng J, Shi S, (2018) 'Photosynthetic acclimation of an evergreen broadleaved shrub (Ammopiptanthus mongolicus) to seasonal climate extremes on the Alxa Plateau, a cold desert ecosystem', Trees, vol.32, no.2, pp 603-614

Patterson AE, Arkebauer R, Quallo C, Heskel MA, Li X, Boelman N, Griffin KL, (2018) 'Temperature response of respiration and respiratory quotients of 16 co-occurring temperate tree species', Tree Physiology, vol.38, no.9, pp 1319–1332

Supervisors

Professor David Tissue, Professor Belinda Medlyn and A/Professor Brendan Choat