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Development of an Individual-Tree Basal Area Increment Model using a Linear Mixed-Effects Approach
Published on: July 3, 2020
Developmental decline in height growth in Douglas-fir
Barbara J Bond1, Nicole M Czarnomski, Clifton Cooper
1Department of Forest Science, Oregon State University, Corvallis, OR 97331, USA. barbara.bond@oregonstate.edu
Tree Physiology
|January 24, 2007
Summary
Tree height growth decline is driven by tree size, not age. Grafting experiments showed that young rootstock revitalized old Douglas-fir scions, increasing growth and altering physiology, confirming size as the primary factor.
Area of Science:
- Plant Physiology
- Forest Ecology
- Tree Biology
Background:
- Trees exhibit a characteristic decline in height growth over their lifespan, often termed 'age-related decline'.
- The underlying cause of this decline—whether intrinsic aging or cumulative size effects—remains a key question in tree biology.
Purpose of the Study:
- To investigate whether the reduction in height growth in aging Douglas-fir (Pseudotsuga menziesii) is mediated by tree size or apical meristem age.
- To evaluate the role of reduced carbon assimilation in the observed decline of height growth.
Main Methods:
- Grafting experiments involving shoot tips from old-growth, young-mature, and seedling Douglas-fir trees onto compatible rootstock.
- Reciprocal grafts were performed between old-growth and young-mature trees.
- Measurements included stem growth (diameter and elongation), mortality, photosynthetic capacity (A/Ci curves), leaf mass per area (LMA), and carbon isotope composition.
Main Results:
- Grafting significantly altered the growth and physiology of scions, with scions adopting characteristics of the rootstock within two years.
- Old-growth scions grafted onto seedling rootstock showed a tenfold increase in stem elongation rate.
- Carbon isotope discrimination indicated physiological adjustments in response to rootstock, but differences in carbon assimilation were minor compared to growth changes.
Conclusions:
- Tree size, rather than chronological age, is the primary driver of developmental changes in height growth in Douglas-fir.
- Reduced carbon assimilation does not play a significant role in the decline of height growth in aging trees.
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