Canadian Forest Service Publications
Estimation of compensatory growth of coastal Douglas-fir following pre-commercial thinning across a site quality variant. 2018. Li, C.; Huang, S.; Barclay, H.; Filipescu, C. Forest Ecology and Management 429(2018):308-316.
Issued by: Northern Forestry Centre
Catalog ID: 39261
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This study is aimed to address the issue of whether the volume loss in stands with partial cutting such as pre-commercial thinning (PCT) treatments could catch-up with the ones of unthinned stands, employing the lens of compensatory growth (CG) in plant ecology to ask the question of how long one could expect to see the complete CG to happen, if any. CG is the ability of plants or vegetation to vary their growth to offset damage caused by disturbances. Though it has been demonstrated in annual plants such as crops and grasslands, it has not been well studied in trees except Douglas-fir under different PCT regimes in the Swiss Central Plateau, trembling aspen seedlings under different fertilization regimes, and fast-growth willow coppice with clipping, etc. Our data from a long-term silvicultural trial (combined PCT and fertilization) near Shawnigan Lake, Vancouver Island, British Columbia, Canada, demonstrate complete CG in coastal Douglas-fir 40 years after treatments at both the tree and stand levels. We present a method of estimating the length of time required to achieve complete CG in stand volume. Our results also show that different patterns of complete CG could be expected under different site conditions differentiated by levels of fertilization. Without fertilization a long length of time would be required to reach complete CG, and the length of time could be reduced by increased fertilization application. Potential forest management implications are discussed including possible alternative shapes of yield curves for managed stands and hence the forecast of future wood supply, positive economic evaluation of PCT and fertilization, and contribution to regional carbon budget.
Plain Language Summary
Many animals and plants undergo compensatory, or catch-up, growth after a disturbance or after their growth has slowed because they have been deprived of nutrients. One form of disturbance that humans apply to tree stands is precommercial thinning. This involves cutting out some of the trees from young tree stands to reduce the density of the stand and increase the growth of the remaining trees. Compensatory growth has not been well explored in trees, partly because trees grow slowly and researchers have relatively short careers. The authors of this study investigated whether compensatory growth after precommercial thinning and fertilization enables thinned plots of trees to catch up with unthinned plots in terms of the volume of wood they contain. They analyzed data from a long-term forestry project near Shawnigan Lake on Vancouver Island, British Columbia. The dominant species in this project is coastal Douglas-fir. The authors found that all of the plots of coastal Douglas-fir that were thinned and fertilized completely caught up with untouched plots within 40 years. Plots that received more fertilizer experienced faster growth. This study’s findings can be used to forecast the yields from managed tree stands.