By Jim Hilton
Since most of the articles on the government site on fertilization were prior to the wildfires of 2017/18, beetle impacts were stated as the main reason for creating severe mid-term timber supply problems in many management units.
According to one of the latest government publication on fertilization of B.C. forests: “The current forest fertilization program in the British Columbia Interiorfocuses on treating stands of Douglas-fir and spruce that range from about 20 years of age up to 70 years or older. Forest managers may consider fertilizing lodge pole pine stands in the future when mountain pine beetle populations have declined. Not all age-appropriate fir and spruce stands are fertilized, however. Candidate stands must be well-stocked, but stand density must be low enough that the tree crowns can expand after fertilization, which is necessary for increased tree growth. Provincial stand selection guidelines also require the consideration of the site’s natural productivity, the trees’ current amount of foliage, and other biological factors.”
A single fertilizer treatment can be expected to add about 15 cubic metres of wood per hectare within 10 years. Fertilization is considered one of the most effective treatments to maximize volume production and financial return. There are benefits to the forest under story as well. Shrubs and forage plants absorb some of the nitrogen not taken up by conifers, providing nutritional benefits to wildlife and livestock.
An article by Ralph Winter, May 24, 2006: “Mitigating timber supply impacts through strategic impacts through strategic Forest Fertilization” describes how many jurisdictions in similar latitudes (e.g., Sweden, Finland) have used fertilization effectively to improve timber supply.
The B.C. government has done 25 years of fertilizer research in the Interior and has published scientific information for several species, sites, and ages species and ages. Work has been done in close co-operation with universities, industry and others leading to good support for operational fertilization. Mr. Winters presentation looks mainly at Interior spruce best responses which showed a growth increasing 30-40 per cent over nine years.
The smallest growth responses are associated with highest site indexes and other limiting factors can be deficiencies in micro nutrients like sulphur and boron.
The downside of fertilization is that the fast growing trees are also more tasty for some insect and rodent pests. Caution also has to be taken when thinking of fertilization of some Interior pine stands which could be attacked by active pine beetle outbreaks.
Getting precise information on production increases is not easy and there is work being done on operational fertilization monitoring. An alternative monitoring protocol as described by a 2015 article by Rob Brockley where he answers the question. Are stand growth responses from the operational fertilization program consistent with fertilization research results?
I did not find any information on forest enhancement apart from commercial fertilizers so my subsequent articles will look at alternate ways of unceasing forest productivity like nitrogen fixing legumes and the importance of coarse woody debris.
Jim Hilton is a professional agrologist and forester who has lived and worked in the Cariboo Chilcotin for the past 40 years. Now retired, Hilton still volunteers his skills with local community forests organizations.