Forest Investment Account

Abstract of FIA Project 2241003

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The response of caribou terrestrial forage lichens to forest harvesting and mountain pine beetles in the East Ootsa and Entiako areas annual report - 2003/04 - year 3

Author(s): Williston, Patrick; Cichowski, Deborah
Subject: British Columbia, Biology, Ecology, Forestry, Silviculture/Forest Management Systems
Series: Forest Investment Account (FIA) - Land Base Investment Program - Innovative

Abstract

This study was initiated in 2001 to document the response of caribou terrestrial forage lichens to mountain pine beetle and forest harvesting disturbances. We established 65 permanent plots in the East Ootsa area in 3 biogeoclimatic subzones (ESSFmc, SBSmc2, and SBSdk) and 15 permanent plots in the Entiako areas in the SBPSmc. Each permanent plot contains 6-12 permanently marked photoplots for documenting terrestrial lichen abundance and includes coarse woody debris transects for assessing ease of movement for caribou and fisheye photographs of the canopy for assessing light availability. In addition to permanent sample plots, we are also monitoring: transplants of terrestrial lichens to red-stemmed feathermoss colonies and red-stemmed feathermoss to terrestrial lichen colonies to document competition; kinnikinnick abundance under the canopy of mountain pine beetle killed trees; and growth rates of Cladina, red-stemmed feathermoss and kinnikinnick. This report summarizes activities conducted during the 2003 field season (Year 3).
In Year 3, mountain pine beetle attacked trees accounted for an average of 47-82% of all trees (> 7.5 cm dbh) and 66-87% of the lodgepole pine trees for each site series. Currently, live trees >7.5 cm dbh average 160 - 479 stems/ha in permanent plots. Average density of conifers <7.5 cm dbh was similar in 2001 and 2003 for all MPB Attack plots and for 1 Harvested plot, and higher in 2003 than in 2001 for 3 Harvested plots. Lodgepole pine was the dominant understory tree species on all sites except on ESSFmc/03 sites and on SBSmc2/02 Harvested sites where subalpine fir was dominant and lodgepole pine was the second most prevalent.
In 2003, lichen abundance showed a decline in all beetle-killed stands with the exception of the high elevation ESSFmc/03. The range in loss of lichen abundance was 3-5 % in the SBS between 2001 and 2003, while in the ESSF the lichen cover increased by approximately 1% after two growing seasons. All sites within the SBPSmc showed a decline in the abundance of lichens, with a range of 5-6 %. For SBPSmc (01a, 01b, 02), SBSmc2/01c and SBSdk/03 sites, terrestrial lichens in beetle-killed stands appear to be decreasing due to the rapid expansion of kinnikinnick and to a lesser degree twin-flower, feathermoss, grasses and needle litter. For harvested sites, terrestrial lichens decreased in the ESSFmc/03 and SBSdk/03. The decline of forage lichens in harvested sites in the SBSdk/03 appears to be due to kinnikinnick expansion. In the SBSmc2/01c and SBSmc2/02, terrestrial forage lichens in harvested plots have increased while red-stemmed feathermoss have decreased. Our results support our prediction that lichens respond differently to canopy disturbances under different site conditions and suggest that a single approach to lichen management will not work across all site types in the East Ootsa and Entiako areas.
The percent cover of all transplanted lichens and mosses showed little change over the two year duration of this experiment. The only apparent trend observed was a small decrease in cover of mosses in both the control and the treatment, which can be attributed to an increase in needle litter. Similarly, the cover of kinnikinnick in the Gentian Botanical Research and Caribou Ecological Consulting 5 photoplots beneath dying canopy trees did not change significantly after two growing seasons. We expect the response of kinnikinnick to the defoliation of the canopy trees to become more discernable in the next 2 or 3 years.
Lichens and feathermosses grew the best in canopy gaps and the worst in cutblocks, and were intermediate under canopy trees. Trends in the data suggest that only in cutblock were lichens able to grow more rapidly than mosses. Kinnikinnick showed a different pattern and demonstrated the most rapid growth under canopy trees, followed by gaps and then cutblocks. Although kinnikinnick grows an order of magnitude more rapidly than lichens or mosses, it also has a higher shoot mortality rate. There did not appear to be changes in light transmission between 2002 and 2003. Light levels were similar within treatments across all site types. Generally, light levels were intermediate in beetle-killed forests (between 38-46% full open conditions) and high in harvested stands (87-93% full open conditions). Drier sites (site series 02 and 03) tended to have higher light levels and more open canopies than wetter ones (site series 01a, 01b, and 01c), but differences were slight. We anticipate that changes in light levels will become discernable once the beetle-killed canopy trees completely defoliate, likely in the next 2 or 3 years.
The average number of pieces of large woody debris (>7.0 cm diameter) was similar in 2001 and 2003 at all sites, indicating that beetle-killed trees have not yet started to blow over. There was also little change in the distribution of large woody debris pieces for decay, length and mobility classes at each site. Mobility Index increased slightly at all sites and was highest for the SBSmc2/01c biogeoclimatic subzone/site series. Currently, the amount of coarse woody debris is generally low on all sites and is not enough to impede animal movements. On mountain pine beetle killed sites, coarse woody debris is expected to increase as mountain pine beetlekilled trees (47-82% of the trees on each site) are blown over. Our data suggest that the large-scale infestation of mountain pine beetles in the East Ootsa and Entiako area has led to a proliferation of kinnikinnick, and to a lesser extent, twin-flower, a few grasses and feathermoss, resulting in an associated decrease in the abundance of terrestrial forage lichens. In absence of a major disturbance, such as a catastrophic fire, it is possible that caribou terrestrial forage lichens may continue to decline; however, we do not yet know to what extent this pattern of replacement will proceed. Additional sampling is required in Year 5 to assess whether or not the patterns reported here will continue.


For further information, please contact Jennifer Lecuyer, Fraser Lake Sawmills (Jennifer.Lecuyer@westfraser.com)

Updated September 08, 2005 

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