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Earthquake disturbance alters a growth--survival trade-off found along an elevation gradient in a monodominant forest
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  • Robert Allen,
  • Darryl MacKenzie,
  • S. Wiser,
  • Peter Bellingham,
  • Larry Burrows,
  • David Coomes
Robert Allen
Roblyn Place

Corresponding Author:[email protected]

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Darryl MacKenzie
Proteus Wildlife Research Consultants
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S. Wiser
Landcare Research
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Peter Bellingham
Landcare Research
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Larry Burrows
Manaaki Whenua
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David Coomes
University of Cambridge
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Abstract

1. Tree growth–survival relationships link two demographic processes that dictate the com-position, structure and functioning of forest ecosystems. While these relationships have been shown to vary intra-specifically, it remains unclear how this reflects environmental variation and disturbance. We examined the influence of a 700-m elevation gradient and an Mw = 6.7 earthquake in 1994 on intra-specific variability in growth–survival relationships. We expected that survival models that incorporated recent growth would be better sup-ported than those using other factors known to influence tree survival. 2. We used a permanent plot network that representatively sampled a monodominant Nothofagus forest in New Zealand’s Southern Alps in 1974 and that was remeasured seven times through to 2009. The relationships were assessed using pre-earthquake growth and survival, pre-earthquake growth and post-earthquake survival (0–5 years post-earthquake), and post-earthquake growth and survival (5+ years post-earthquake). Sur-vival was related to growth of 4504 trees on 216 plots using Bayesian modelling. We hy-pothesised there would be a positive, logistic relationship between growth and survival. 3. Pre-earthquake, we found a positive, logarithmic growth–survival relationship at all eleva-tions. At higher elevations, trees grew more slowly but had higher survival, supporting our hypothesised demographic trade-off with elevation. As we expected, the earthquake al-tered the pre-earthquake growth–survival relationships and 0–5 years post-earthquake survival held little relationship with growth. Less expected was a strong, logarithmic growth–survival relationship that developed 5+ years post-earthquake because of en-hanced survival of fast-growing trees yet low survival of slow-growing trees. 4. Synthesis. Our findings demonstrate there can be trends in growth–survival relationships along an elevation gradient. If we assume a gradual climate warming is the equivalent of a forest stand shifting to a lower elevation, then data from our pre-earthquake period sug-gests that tree growth–survival relationships at any elevation could adjust to faster growth and lower survival. We also show how these novel growth–survival relationships could be altered by periodic disturbance.
07 Aug 2024Submitted to Ecology and Evolution
12 Aug 2024Submission Checks Completed
12 Aug 2024Assigned to Editor
23 Sep 2024Review(s) Completed, Editorial Evaluation Pending
29 Sep 2024Editorial Decision: Accept