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Research papers, Lincoln University

Tree mortality is a fundamental process governing forest dynamics, but understanding tree mortality patterns is challenging because large, long-term datasets are required. Describing size-specific mortality patterns can be especially difficult, due to few trees in larger size classes. We used permanent plot data from Nothofagus solandri var. cliffortioides (mountain beech) forest on the eastern slopes of the Southern Alps, New Zealand, where the fates of trees on 250 plots of 0.04 ha were followed, to examine: (1) patterns of size-specific mortality over three consecutive periods spanning 30 years, each characterised by different disturbance, and (2) the strength and direction of neighbourhood crowding effects on sizespecific mortality rates. We found that the size-specific mortality function was U-shaped over the 30-year period as well as within two shorter periods characterised by small-scale pinhole beetle and windthrow disturbance. During a third period, characterised by earthquake disturbance, tree mortality was less size dependent. Small trees (,20 cm in diameter) were more likely to die, in all three periods, if surrounded by a high basal area of larger neighbours, suggesting that sizeasymmetric competition for light was a major cause of mortality. In contrast, large trees ($20 cm in diameter) were more likely to die in the first period if they had few neighbours, indicating that positive crowding effects were sometimes important for survival of large trees. Overall our results suggest that temporal variability in size-specific mortality patterns, and positive interactions between large trees, may sometimes need to be incorporated into models of forest dynamics.

Images, UC QuakeStudies

Lucy Johnson, Dean of Postgraduate Studies at a function with Vice Chancellor Rod Car and Vice-Chancellor of Oxford University, Andrew Hamilton to sign a Memorandum of Understanding between the two Universities.

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Warden of Rhodes House, Don Markwell speaks at a function with Vice Chancellor Rod Car and Vice-Chancellor of Oxford University, Andrew Hamilton to sign a Memorandum of Understanding between the two Universities.

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Post graduate students and visitors from Oxford at a function with Vice Chancellor Rod Car and Vice-Chancellor of Oxford University, Andrew Hamilton to sign a Memorandum of Understanding between the two Universities.

Images, UC QuakeStudies

Lucy Johnson, Dean of Postgraduate Studies at a function with Vice Chancellor Rod Car and Vice-Chancellor of Oxford University, Andrew Hamilton to sign a Memorandum of Understanding between the two Universities.

Images, UC QuakeStudies

Lucy Johnson, Dean of Postgraduate Studies and a postgraduate student at a function with Vice Chancellor Rod Car and Vice-Chancellor of Oxford University, Andrew Hamilton to sign a Memorandum of Understanding between the two Universities.

Images, UC QuakeStudies

Ian Town talking to a visitor from Oxford at a function with Vice Chancellor Rod Car and Vice-Chancellor of Oxford University, Andrew Hamilton to sign a Memorandum of Understanding between the two Universities.

Images, UC QuakeStudies

Lucy Johnson, Dean of Postgraduate Studies talks to visitors from Oxford at a function with Vice Chancellor Rod Car and Vice-Chancellor of Oxford University, Andrew Hamilton to sign a Memorandum of Understanding between the two Universities.

Images, UC QuakeStudies

Vice-Chancellor of the University of Canterbury Rodd Carr hands Vice-Chancellor of the Univeristy of Oxford Andrew Hamilton a gift at the function to sign a Memorandum of Understand between the two Universities.

Images, UC QuakeStudies

Lucy Johnson, Dean of Postgraduate Studies and a postgraduate student at a function with Vice Chancellor Rod Car and Vice-Chancellor of Oxford University, Andrew Hamilton to sign a Memorandum of Understanding between the two Universities.

Images, UC QuakeStudies

Postgraduate students who went on an exchange to Oxford after the February earthquakes at a function with Vice Chancellor Rod Car and Vice Chancellor of the University of Oxford Andrew Hamilton to sign a Memorandum of Understand between the two Universities.

Images, UC QuakeStudies

Postgraduate students who went on an exchange to Oxford after the February earthquakes at a function with Vice Chancellor Rod Car and Vice Chancellor of the University of Oxford Andrew Hamilton to sign a Memorandum of Understand between the two Universities.

Images, UC QuakeStudies

Postgraduate students who went on an exchange to Oxford after the February earthquakes at a function with Vice Chancellor Rod Car and Vice Chancellor of the University of Oxford Andrew Hamilton to sign a Memorandum of Understand between the two Universities.