Growth at the microscale : long term thinning effects on patterns and timing of intra-annual stem increment in radiata pine
Date
2018-10-09
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
SpringerOpen
Abstract
Background: Stem radial growth in forests is not uniform. Rather, it is characterized by periods of relatively fast or
slow growth, or sometimes no growth at all. These fluctuations are generally a function of varying environmental
conditions (e.g. water availability) and, importantly, will also be associated with adjustments in properties in the wood
formed. Stand level conditions and forest management, particularly thinning and stand density will, however, also have
a major influence on patterns of growth variation. We explore how different thinning histories and/or stand densities
influence these dynamics of tree growth in the important commercial plantation species Pinus radiata D. Don.
Methods: Daily stem size change was measured using electronic point dendrometers over two growing seasons on
P. radiata trees at two sites, subjected to different thinning regimes. Timing, rates and periodicity of annual growth
were calculated from these data.
Results: Greater overall cross-sectional growth in thinned plots was driven mainly by two dynamics. First, the cessation
of seasonal growth occurred at least 3 weeks later in the stands in which thinning had taken place. There was no
difference between thinned/unthinned stands, however, in the timing of growth onset. Second, within the longer
season, trees in thinned plots had more growth days (as much as 20% more) than unthinned plots. The rates of
growth on days when growth occurred were not different, however. In this context, it is notable that in trees in
the unthinned plots experiencing the most severe competition there were strong “pulses” of growth following
drought-breaking rainfall events. Unthinned plots at high stand densities also maintained a smaller (but
consistent) zone of dividing cells throughout the season than thinned plots.
Conclusions: In Pinus radiata growing under conditions as in our study, conditions late in summer, particularly
drought, have an important effect on the timing of cessation of growth. Early season temperature appears to
have no effect in determining timing of annual growth. Limiting conditions during the season reduce growing
duration, and thus total growth, more in unthinned stands than thinned stands. These findings are valuable in
developing new generations of fine-scale growth and wood property models.
Description
CITATION: Drew, D. M. & Downes, G. M. 2018. Growth at the microscale : long term thinning effects on patterns and timing of intra-annual stem increment in radiata pine. Forest Ecosystems, 5:32, doi:10.1186/s40663-018-0153-z.
The original publication is available at https://forestecosyst.springeropen.com
The original publication is available at https://forestecosyst.springeropen.com
Keywords
Pinus radiata, Dendrometers, Droughts, Thinning
Citation
Drew, D. M. & Downes, G. M. 2018. Growth at the microscale : long term thinning effects on patterns and timing of intra-annual stem increment in radiata pine. Forest Ecosystems, 5:32, doi:10.1186/s40663-018-0153-z