Forest Investment Account

Abstract of FIA Project 2018011

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Influence of Fire Retention on Stand Structure and Mammal Communities in Mixed Douglas-Fir - Lodgepole Pine Forests

Author(s): Sullivan, Thomas P.
Subject: British Columbia, Biodiversity, Wildlife
Series: Forest Investment Account (FIA) - Land Base Investment Program - Innovative


Variable retention harvests or 'green-tree retention systems' are an important management component of temperate zone coniferous forests. Green-tree retention may help enhance functional links among forest structures, ecological processes, and biological diversity found in natural forest ecosystems. This project was designed to determine if (i) diversity of stand structure attributes (species diversity and structural diversity of herb, shrub, and tree layers), (ii) abundance and diversity of forest floor small mammal communities, and (iii) relative habitat use by mule deer, will decline with decreasing levels of tree retention. This document reports on progress for year 3 of the 4-year project.
Stand structure attributes and communities of forest floor small mammals were sampled from 1996 to 2002 in replicated clearcut, single seed-tree, group seed-tree, patch cut, and uncut forest sites in mixed Douglas-fir (Pseudotsuga menziesii) - lodgepole pine (Pinus contorta) forest in southern British Columbia, Canada. Habitat use by mule deer was measured in 1999, 2000, 2001, and 2002.
Clearcut, single seed-tree, and group seed-tree sites had similar mean basal areas of residual trees, ranging from 0.1 to 2.5 m2/ha, with significantly higher levels on patch cut (23.4 m2/ha) and uncut forest (39.0 m2/ha) sites. Mean densities of residual trees also followed this pattern, ranging from 0.7 to 16.3 stems/ha on the clearcut to group seed-tree sites, to 769.4 and 2050.0 stems/ha on the patch cut and uncut forest sites, respectively. Mean diameters of trees in the 30-60 cm and >60 cm classes were similar across treatment sites.
Mean volume (m3/ha) of down wood was similar among treatment sites ranging from 116.7 in the single seed-tree to 210.2 in the patch cut sites. Harvested sites had more small (<5 cm) and medium (5-25 cm) diameter pieces of down wood than the uncut forest sites. Mean total crown volume index of herbs, shrubs, mosses, and lichens continued to be similar among sites. Crown volume index of trees was highest in patch cut and uncut forest sites. Mean species richness of herbs, shrubs, and total plants also continued to be similar among sites. Mean richness of trees in seed-tree sites was similar to that in uncut forest in most post-harvest years. Mean species diversity of herbs was similar, but that of shrubs and trees was generally lowest in the patch cut sites, and similar among the other sites.
Mean total abundance, species richness, and species diversity of small mammals was similar among sites for these measurements 1996 to 2002. Late successional forest species such as red-backed voles and early successional, but mycophagist, northwestern chipmunks persisted on the group seed-tree harvested sites during the high abundance years of 1997 and 1998. In subsequent years, mean numbers of red-backed voles were highest in uncut forest sites. Relative habitat use by mule deer (Odocoileus hemionus) was highest in the seed-tree sites during summer periods and highest in the group seed-tree, patch cut and uncut sites in winter periods.
This project will be completed in 2003. Our investigation will determine the influence of residual fir density and basal area on stand structure and mammal communities up to 8 years post-harvest. These results will provide guidelines for fir retention levels on harvested fir-pine forest units at a landscape scale.

For further information, please contact Thomas P. Sullivan, Applied Mammal Research Institute (

Updated September 08, 2005 

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