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dc.contributor.authorByrne Damianen
dc.date.accessioned2011-01-20T22:18:19Z
dc.date.issued2001en
dc.identifier.urihttps://hdl.handle.net/10182/3095
dc.description.abstractOne-year-old (C+1) and current (C) cohorts, labelled with a ¹⁵N tracer, were studied on second order branch systems of four trees of five-year-old Pinus radiata D. Don. Concurrent with this, individual one-year-old (C+1) and current (C) fascicle nitrogen (N) and ¹⁵N dynamics were also studied on the second order branches. The objective was to improve our understanding of internal cycling of N within second order branches, used for standard foliage analysis, within different canopy positions over a growing season. Branches were destructively sampled from two canopy levels on the north side of the four trees. Individual C+1 fascicles were sampled from set positions along second order branches at each sampling, including new current fascicles (C). The trees were classed as blocks and the canopy level as a split-plot. The experiment was carried out between August 1995 and June 1996 over one complete growing season at the Lincoln University agroforestry experiment (43°38'S, 172°30' E) Canterbury, New Zealand. The climate is temperate and has a mean annual rainfall of 695mm which is evenly distributed and the soil is a Templeton silt loam, a moderate to free draining fertile soil. Mass of C+1 fascicles over all positions decreased 7-12% over the experimental period. The C-base and C-top fascicles increased in dry weight mass over the growing season to 63 and 64 mg respectively but never attained the same mass as the C+1 fascicles. The second order branch system mass of the C+1 foliage accounted for over 70%, or 19.3g, of the branch system in August 1995. By June 1996 the C+1 and C cohorts accounted for 32% and 38% respectively of the total mass of the branch system. C+1 wood and bark components had increased their mass by June 1996 by 136% and 16% respectively. C+1 fascicle N and ¹⁵N concentration declined from August 1995 until March 1996, however, from March 1996 to June 1996 there was a small increase in concentration again in all fascicle positions. C fascicles fluctuated in concentration from December 1995 to June 1996. Branch system foliage N concentrations for both the C+1 and C cohorts exhibited periods of increases and decreases. However, at the final sampling in June 1996, the C+1 cohort N concentration was 9.0% less than the concentration of the C cohort which was 1.66% N. Other components were considerably lower, apart from the bud component, in N concentration with the C+1 wood the lowest at 0.237% N at June 1996. ¹⁵N atom% in initial components at August 1995 had decreased from 0.571% at August 1995 to 0.506% in June 1996, an 11% decrease. N and ¹⁵N content of the three C+1 fascicles decreased 8-17% and 32-41% respectively from August 1995 to June 1996. From March 1996 to June 1996 there was an increase in all fascicle positions. Both the new C fascicle positions increased their N and ¹⁵N content at each sampling. The branch system total N content nearly doubled over the experimental period from 359 mg to 666 mg, while excess ¹⁵N content was relatively constant from December 1995 to March 1996. A 20% reduction in N content between December 1995 and March 1996 was evident for the C+1 cohort indicating possible stress due to seasonal drought. The N content in the C cohort increased over the experimental period following growth patterns. There was evidence of late N and ¹⁵N content, 8% and 30% respectively, withdrawal from the C cohort from March 1996 to June 1996. The increase in excess ¹⁵N in the C cohort indicated retranslocation from the older components from within the whole tree. The net losses of N content from the C+1 cohort did not meet the N needs of the expanding C cohort. Excess ¹⁵N content loss from the C+1 cohort exceeded the accrual of excess ¹⁵N content in the C cohort. The branch system was deemed not be independent for N use but showed autonomous behaviour for the excess ¹⁵N pool within the branch system. The variability in excess ¹⁵N and atom% data may indicate isotope fractionation within the trees at the experimental site.en
dc.language.isoenen
dc.publisherLincoln Universityen
dc.subjectPinus radiataen
dc.subjectnitrogen cycleen
dc.subjectsecond order branch systemsen
dc.subjectinternal cycleen
dc.subjecttree physiologyen
dc.subjecttree nutritionen
dc.subjectgrowthen
dc.subjectforestryen
dc.titleInternal cycling of nitrogen in second order branches of Pinus radita D. Donen
dc.typeThesis
thesis.degree.grantorLincoln Universityen
thesis.degree.levelMastersen
thesis.degree.nameMaster of Agricultural Scienceen
lu.contributor.unitLincoln Universityen
dc.rights.accessRightsDigital thesis can be viewed by current staff and students of Lincoln University only. Print copy available for reading in Lincoln University Library. May be available through inter-library loan.en
pubs.organisational-group/LU
pubs.publication-statusPublisheden


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