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Research article2022Peer reviewedOpen access

Mortality and basal area growth following precommercial thinning in stands affected by Armillaria, Laminated and Tomentosus root diseases in southern British Columbia

Morrison, Duncan J.; Ronnberg, Jonas; Pellow, Kevin; Cleary, Michelle

Abstract

Precommercial thinning aims to reduce the density of immature stands to stimulate growth of well-spaced crop trees of preferred species and free from defects and disease. The chronic persistence of Armillaria, Laminated and Tomentosus root diseases in coniferous forests of British Columbia, Canada may offset potential gains in timber yield of commercially important tree species by creating stumps that the fungi utilize as an energy source to infect neighbouring trees. In juvenile plantations and naturally regenerated stands in six biogeoclimatic (BEC) zones with evidence of root disease caused by Armillaria ostoyae (8 sites), Coniferiporia sulphurascens (2 sites) or Onnia tomentosa (1 site), five of ten 20 m square plots per site were randomly selected for thinning to British Columbia Ministry of Forests specifications. Crop tree diameter at breast height and mortality from all causes were recorded at establishment and periodically thereafter up to 19 years post-thinning. Logistic regression analysis of mortality rates showed significant differences among root disease pathogens, between planted and natural stands, and among ecological zones. Yet over all sites, differences between thinned and control plots were not significant. At the final assessment, crop tree basal area was higher in thinned than in control plots at 10 of 11 sites. Root disease, including infected and dead trees and other lethal biotic and abiotic agents, reduced potential yield in both treatments (thinned and control). At several Armillaria sites, mortality was slightly to substantially higher in thinned than in control plots, suggesting that thinning can increase the amount and potential of inoculum which may continue to adversely impact productivity of those stands. Recommendations for silvicultural management of the three root diseases are discussed.

Keywords

growth loss; mortality; root disease; thinning

Published in

Forest Pathology
2022, volume: 52, number: 6, article number: e12778
Publisher: WILEY

SLU Authors

Associated SLU-program

SLU Plant Protection Network
SLU Forest Damage Center

UKÄ Subject classification

Forest Science

Publication identifier

  • DOI: https://doi.org/10.1111/efp.12778

Permanent link to this page (URI)

https://res.slu.se/id/publ/120000