Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596613
Title: Temporal variation in the stable isotope signals of trees with contrasting growth strategies
Author: Betson, N. R.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2005
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Abstract:
A long term study of the variation in d12C of bulk leaf material was undertaken under 3 light regimes (3%, 12% and 100% sunlight) using 2 different species displaying contrasting shoot phenologies: Betula pendula Roth. an early successional species with a rapid leaf turnover (“successive” phenology) and Fagus sylvatica L. a late successional species with a single flush of long-lived leaves (“flush” phenology). It was hypothesised that there would be greater seasonal changes in the isotopic composition of the leaves of B. pendula, within a single leaf cohort (due to rapid leaf turnover of that species) and that the different light regimes and shade tolerances of the two species would further extend variation. Physiological and phenological parameters, alongside bulk leaf d13C, were measured over the first growth season (2002) on 4 leaf cohorts in the B. pendula and the single flush of the F. sylvatica. The d13 C of the initial leaf was consistently more enriched in the heavier isotope than bud material.  Further changes were observed both within (up to 2‰) and between (up to 4‰) leaf cohorts in both species as well as substantial shifts between light regime (up to 6‰). During the following growth season, measurements were focused at 2 time points: early season and mild season to attempt to explain the variation within leaf cohort and in the change in isotopic signal between the bud and initial leaf. Alongside the continuation of measurements from the previous season, the d13C of the soluble carbohydrates and starch fractions were measured, as well as the d18 O of leaf organic material to follow the mobile carbon fractions as the organic signal changed and to partition the d13C signal into stomatal and biochemical influences. Carbohydrate d13C values showed that the within cohort variation could be explained by fractionation processes during phloem unloading and, later in the season, the progressive incorporation of new carbohydrate with a more negative delta.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.596613  DOI: Not available
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