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Understanding tree rings – how the interplay of climate and seed production controls tree growth


Project Description

This project will explore the interplay of climate with tree growth and reproduction, to improve understanding of climate-growth relationships in tree ring chronologies.
Tree rings have a broad range of applications in environmental science including quantifying forest growth, carbon storage, and the reconstruction of Holocene climate. Many of these applications depend on understanding the drivers of variation in tree ring width (TRW). For example, narrow tree rings associated with drought events are used as an indicator of forest vulnerability to climate extremes, and the relationship between temperature and TRW forms the basis of climate reconstructions.
Recently, a number of studies have shown that an important driver of variation in TRW is variable resource allocation – i.e. where a tree “decides” to allocate carbon and nutrients. In particular, allocation to reproduction (flowers and fruits) is a potentially important drain on resources. In many tree species, a bumper seed crop is associated with a narrow tree ring, indicating a trade-off between growth and reproduction. A number of recent studies have focused on this phenomenon and its implications in European beech (Fagus sylvatica) (Hacket-Pain et al., 2015, 2017, 2018). However, these conclusions require testing for other species, particularly those used in tree-ring based climate reconstructions. For example, narrow tree rings resulting from bumper seed crops may influence the calibration of TRW-climate relationships used for climate reconstruction, and the use of tree-ring metrics to assess species resilience to climate change.
Environmental challenge: How can tree ring data be used to robustly quantify the response of tree growth to variation in climate? And how can a better understanding of growth-climate relationships improve tree-ring based climate reconstructions and assessments of the climate change resilience of forests?
This project will develop new tree ring chronologies to complement existing records of annual seed production. Seed production time-series will be sourced from the MASTREE and MASTREE+ databases (Ascoli et al., 2017a, see http://www.liverpool.ac.uk/geography-and-planning/research/mast-net). Field sampling will include sites across Europe and potentially in Patagonia, taking advantage of a new collaboration with CONICET (National Scientific and Technical Research Council, Argentina). The objective of the project will be to develop robust methods to distinguish between masting- and climate-related variability tree-ring chronologies (i.e. identifying whether a narrow tree ring has resulted from a bumper seed year – a “mast year”) – or a climate anomaly).

There is substantial scope for the student to develop additional objectives. For example, the datasets could provide the basis for a unique multi-century reconstruction of mast years. Alternatively, as inter-annual and decadal variation in seed production is influenced by climate, masting can create an indirect pathway for climate to influence tree growth. This has been tested in European beech (Hacket-Pain et al., 2015, 2018) but remains unexplored in other tree species.
In addition to ring width measurements, the student will develop Blue-Intensity chronologies, and an opportunity exists to measure wood anatomical traits (working with external collaborators). The candidate will also have the opportunity to participate in other fieldwork organised by the lab – this has included recent fieldtrips to Canada (Northwest Territories) the Italian Alps and northern Greece.

Interested candidates are strongly encouraged to contact the lead supervisor for more information.

To apply for this opportunity, please visit: https://www.liverpool.ac.uk/study/postgraduate-research/how-to-apply/ and click the ’Apply online’ button.

Funding Notes

Full funding (fees, stipend, research support budget) is provided by the University of Liverpool for 3.5 years for UK or EU citizens. Formal training is offered through partnership between the Universities of Liverpool and Manchester. Our training programme will provide all PhD students with an opportunity to collaborate with an academic or non-academic partner and participate in placements.

References

Hacket-Pain et al. (2018). Climatically controlled reproduction drives interannual growth variability in a temperate tree species. Ecology Letters, 21, 1833-1844
Hacket-Pain et al. (2019). Temperature and masting control Norway spruce growth, but with high individual tree variability. Forest Ecology and Management 438, 142-150
Hacket-Pain et al. (2017). Drought and reproductive effort interact to control growth of a temperate broadleaved tree species (Fagus sylvatica). Tree Physiology 37, 744-754
Hacket-Pain et al. (2015). The influence of masting phenomenon on growth–climate relationships in trees: explaining the influence of previous summers' climate on ring width. Tree Physiology, 35, 319-330
Hadad et al. (2019). Frost record in tree rings linked to atmospheric circulation in northern Patagonia. Palaeogeography, Palaeoclimatology, Palaeoecology, 524, 201-211
Hadad and Roig. (2016). Sex-related climate sensitivity of Araucaria araucana Patagonian forest-steppe ecotone. Forest Ecology and Management, 362, 130-141

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