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Foothills Growth and Yield Association Quicknote #14

March 2012

By: Dick Dempster

Regenerated Lodgepole Pine Trial 10-year Results: Tree Mortality and Health

The Regenerated Lodgepole Pine Trial consists 102 one-hectare permanent sample plot clusters (“installations�) installed about 10 years ago throughout the Alberta foothills to monitor stand development of lodgepole pine, planted and naturally regenerated after harvesting, in relation to site and treatment factors. This note is one of 3 summarizing results after10 years. A more detailed report is also available.1 During the last decade, Alberta foresters have become increasingly aware of health risks to lodgepole pine, including to postharvest regneration such as that shown in the image at left.

The figure below shows trends by site class2 in cumulative mortality of planted stock to the end of the trial’s 10th growing season since

1

30.0 Cumulative Mortality %

planting. The highest mortality occurs on dry (class 1) and rich (class 4) sites. Weeding has not yet shown any statistically significant effect. Because of ingress delay, it is too early to accurately assess mortality in natural regeneration and to reliably compare it with mortality in planted stock.

Mortality of planted stock is positively correlated (i.e. increases) with deciduous tree stocking and density, but is negatively correlated with the presence of willow, alder, other tall shrubs, forbs and mosses.

Site Class

25.0 20.0

1 2

15.0

3

10.0

4

5.0

5

0.0 3

4

5

6

7

8

9

10

Growing Seasons since Planting

Regenerated lodgepole pine trial 10-year crop performance report. Foothills Growth and Yield Association, February 2012. http://foothillsresearchinstitute.ca/pages/Publications/ 2 1 = bearberry / lichen / hairy wild rye (submesic-subxeric, medium-poor); 2 = Labrador tea - mesic (mesic, poor); 3 = billberry / cranberry / sarsaparilla / rhododendron (mesic, medium); 4 = honeysuckle / fern (subhygric, rich); 5 = Labrador tea - hygric (hygric, poor).

% of All Mortality

A strong relationship was found between mortality and mean annual temperature. Responses of mortality to climate variables differ between 70 ecological site classes, but overall mortality 60 increases with temperature. (These responses are 50 40 described and discussed in detail elsewhere.)

30 20 10 0

The figure at left shows apparent causes of mortality measured over the last 2 years. The primary direct causes during this period have been root disease (mostly Armillaria spp., pictured below left), followed by root collar weevils (mostly Hylobius warreni, larval stage pictured below right) and rusts (mostly Endocronartium harknessi).

Mortality Cause

100 80

60 40

GS 7

20

GS 9

0 Armillaria Warren Western Root Root Collar Gall Rust Disease Weevil

Pathogen

Average % of Trees with Symptoms

% of Installations with Pathogen Present

Occurrence of the 3 leading lethal pathogens has increased in the last few years: the figure below left compares the percentage of installations with the pathogens detected as present in the 7th and 9th growing seasons (GS).

The figure below right makes a similar comparison for the percentage of trees (including both live and dead) showing symptoms of infection.

20 15 10 GS 7

5

GS 9

0 Armillaria Warren Root Root Collar Disease Weevil

Western Gall Rust

Pathogen

For more information on this or other Foothills Growth and Yield Association publications, please contact: Dick Dempster (email: difc@btinternet.com) or visit www.foothillsresearchinstitute.ca.