New report suggests alternative to using traditional site indices – Williams Lake Tribune


While reading the Community Forests newsletter, I came across a recent article regarding the ongoing discussions about our old growth forests.

State of old-growth forests in British Columbia, the situation in 2021, Oct 21, 2021 by lead author Cam Brown was funded by the British Columbia Council of Forest Industries (BC COFI). One of the main reasons for publishing this article was to provide an alternative approach to the VRI Site Index (SI) data used in the article I wrote last week, Last position for biodiversity by authors Price, Holt and Daust.

Author Cam Brown suggests that there is a superior method for deriving site indices, especially for old growth forests. Provincial forestry research staff released this data as the Provincial Site Productivity Layer (PSPL) with supporting validation. Using the new PSPL site indices, the amount of old growth forest with an SI greater than 25 is 29 percent rather than the three percent as discussed in the Last position for biodiversity publication. As described last week, a site index of 25 means that a tree has reached a height of 25 meters in 50 years.

To illustrate his point, Brown describes how a study of 533 large trees verified on the British Columbia coast showed that a large portion of these large trees have VRI site indices of 20m. PSPL data shows a much stronger relationship between the presence of large old trees and higher site productivity.

Cam Brown is also using data from the Fairy Creek watershed to promote the use of PSPL site indices.

“This high-profile old-growth area has attracted considerable attention for preservation over the past year and is therefore assumed to be valuable old-growth forests. The upper 80 percent of the watershed contains stands between 199 and 319 years old (VRI ages) with VRI site indices generally less than 20 m while the bottom of the watershed has higher site index values ​​but stands younger at 30-70 years.

Thus, if the stands must be 250 years old with site indices of at least 20 m to be considered good quality old growth forests, a small fraction of this valley would meet this definition. Fairy Creek is therefore largely excluded from what the Last

Stand for biodiversity report defined as quality old-growth forest (i.e. 415,000 ha or three percent of all old-growth forest) and is a good example of why this report has caused the confusion it has created around the state of old growth forests in the province.

I think Cam Brown does a good job of describing how forest inventories are done in the province and I have also found his description of the types of natural disturbance to be helpful in explaining how there are older forests in the types of wetter forests on the coast and some inland stands.

I will also be interested in the response of other old growth researchers and forest planners regarding his suggestion to use the PSPL site index.

I found that there was some confusion between the data in some of the tables regarding the discussions and the comparisons with the two reports. that is, the PSPL had five percent old shoots with an SI> 25 while the VRI was three percent. Not much of a difference.

I don’t want to go into the technical details in this article, but I would like to look at the positive side of the fact that there is more than a fraction of three percent old shoots if we accept Mr. Brown’s report.

My concern is that this is not an attempt by the industry to justify an increase in the annual allowable cut and to continue clearcuts as the primary harvesting approach at many sites. old forests.

In my opinion, foresters should experiment with more innovative harvesting approaches rather than clearcuts and more effort should be aimed at limiting the large amount of waste usually associated with past harvesting practices.

Having big old trees sitting in the middle of a clearcut surrounded by a fringe of trees does not, in my opinion, retain much of the old growth values. I would like to highlight the word “manage” in the OGMAs of our forest lands exploited due to pests and climate change, some controlled harvesting and burning may be the only way to ensure their long term survival.


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