Ecology of understory and below-ground communities in lodgepole pine forests under changing disturbance regimes
McIntosh, A.C.S. 2013.
Abstract
As climate changes and disturbance regimes shift, there is a need to better
understand and anticipate potential impacts of both natural and anthropogenic disturbance
agents on forest ecosystems. Lodgepole pine forests in western Canada are experiencing
an unprecedented mountain pine beetle (MPB) outbreak, and the ecosystem-level effects
of ongoing expansion of MPB into novel habitats east of the Canadian Rockies are
unknown. Another way ecosystems are being disturbed is through management practices
that are attempting to enhance timber production by using introduced species in
plantations; lodgepole pine has been introduced around the world as an important timber
species, but its invasive potential in some areas, such as Sweden, remains unclear.
To better understand the ecological impacts of disturbance in lodgepole pine
ecosystems I investigated: i) fine-scale patterns in understory plant and microbial
communities in mature lodgepole pine forests; ii) effects of simulated MPB attack and
salvage harvest on above- and below-ground dynamics of these forests; iii) potential for
pine regeneration after MPB attack in newly invaded stands; and iv) effects of the
introduction of lodgepole pine to Sweden on forest floor properties and processes.
In mature undisturbed lodgepole pine forests I identified four fine-scale plant
communities, primarily influenced by below-ground factors; four structural microbial
communities, primarily influenced by the understory composition; and four functional
microbial communities that were not strongly associated with any environmental factors
measured in my study. I found short-term resistance to ecosystem change after simulated
MPB attack, compared with more immediate ecosystem changes in response to salvage
harvest. Regeneration of lodgepole pine seedlings appears unlikely to occur in the short
term after MPB attack without active silvicultural intervention. In northern Sweden,
introduced lodgepole pine had minor ecosystem-level effects compared with the native pine; the impacts of species introductions are likely functions of both regional influences
and ecological differences between the introduced and native species.
Overall, my thesis provides novel insights into the ecology of lodgepole pine
forests in the face of changing disturbance regimes and forest management practices,
demonstrating the important ecological roles that both above- and below-ground
properties and processes play in these forested ecosystems.
