Assessment of post-beetle impacts on natural regeneration of Lodgepole Pine

Egger, Keith N and Arocena, Joselito and Green, Scott and Kennedy, Nabla and Massicotte, Hugues and Scholefield, Scott (2009) Assessment of post-beetle impacts on natural regeneration of Lodgepole Pine. Working Paper. Her Majesty the Queen in Right of Canada, Canadian Forest Service, Pacific Forestry Centre, Victoria, BC.

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Abstract

The ecological disturbance from wildfire (2004) on ~ 10,000 hectares of forests near the Kenny Dam presented a unique opportunity to study the natural and artificial regeneration in burned mountain pine beetle (Dendroctonus ponderosae Hopkins) infested stands in north-central British Columbia. Mountain pine beetle (MPB) has been documented as a natural disturbance agent that may precede wildfire in lodgepole pine forests (Pinus contorta var. latifolia). The objectives of this study were to i) characterize lodgepole pine regeneration and related micro-site conditions associated with wildfire, ii) identify limitations for germination, survival and recruitment of natural and artificial regeneration in relation to site moisture, fire severity, and vegetative competition, iii) determine if regeneration was limited by belowground factors (soil characteristics, ectomycorrhizal inoculum, nitrogen-cycling bacterial communities), and iv) provide guidance on local operational management of MPB-killed stands. The germination, survival and recruitment of lodgepole pine seedlings over two growing seasons were compared on 18 disturbance plots (replicated three times) with three fire severity classes (high, moderate, low), two moisture regimes (dry and wet), two seed provenances (wild and improved Class-A), and two seedbed types (disturbed and undisturbed). In the growing seasons following the fire (2005 and 2006), seeded plots experienced bursts of spring germination followed by continuous minor waves of new germination (that ended by August 2006). Results showed that natural regeneration was highest on wet sites and seedling density increased with declining fire severity. On dry sites, new germinants were rare and limited by microsite conditions associated with high and moderate fire severity, with highest germination rates experienced on low fire severity. Seed provenance did not influence germination and survival rates. In contrast to the germination, survival and recruitment results, growth rates were highest on the dry sites and increased with increasing fire severity. Thus, although recruitment on dry sites is unlikely to sufficiently restock these stands with lodgepole pine, the recruits show the highest growth rates. Conversely, recruitment on the wet sites will fully sufficient to fully restock these stands, but the growth rates of the seedlings will likely be impeded by competition with other vegetation. Although we documented adverse impacts of MPB and burning on soil properties, and lower diversity of ectomycorrhizal communities and nitrogen-cycling bacterial communities on the dry sites, there is no evidence that these factors are limiting growth of recruits on these dry sites. We are reviewing these results and preparing publications, and will make final management recommendations once the data are completely analyzed.

Item Type: Monograph (Working Paper)
Additional Information: ISBN: 978-1-100-13145-0
Departments or Groups: *NONE OF THESE*
Divisions: School of Science > Department of Chemical and Life Sciences
Depositing User: Nabla Kennedy
Date Deposited: 10 Sep 2014 19:09
Last Modified: 22 Aug 2016 10:27
URI: http://repository.wit.ie/id/eprint/2891

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