Effects of disturbance on tree community dynamics in whitebark pine (Pinus albicaulis Engelm.) ecosystems

Jeremy T. Amberson, Megan P. Keville, Cara R. Nelson

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Whitebark pine (Pinus albicaulis Engelm.), an ecologically important tree species in high-elevation ecosystems of western North America, is threatened by white pine blister rust (Cronartium ribicola Fischer) and increased pressure from mountain pine beetle (Dendroctonus ponderosae Hopkins) due to climate warming. In addition, there is concern that fire suppression may be leading to successional replacement of whitebark by late-seral trees. Despite widespread knowledge that the tree is in decline, there is limited understanding of its successional dynamics, particularly in forests disturbed by white pine blister rust and mountain pine beetle. Our objective was to examine how disturbances have affected forest composition, structure, and seedling regeneration over a 22-year period (1990-2012) at 19 sites in the CascadeMountains ofWashington State (USA). Over that time, 13 sites (68%) were infected by white pine blister rust, 11 (58%) were disturbed by mountain pine beetle, and 5 (26%) experienced wildfire. Tree community composition changed significantly during the study period, primarily due to significant mortality of mature (≥20-cm diameter at breast height) whitebark pine. Despite loss of mature whitebark trees, we found little evidence of successional replacement by other tree species. Whitebark seedling density was unrelated to basal area of mature whitebark pine, but positively correlated with the presence of herb and shrub cover. Our results demonstrate the value of long-term repeated measurements for elucidating successional dynamics.

    Original languageEnglish
    Article number566
    JournalForests
    Volume9
    Issue number9
    DOIs
    StatePublished - Sep 13 2018

    Keywords

    • Cronartium ribicola
    • Dendroctonus ponderosae
    • Forest succession
    • Microsites
    • Mountain pine beetle
    • Pinus albicaulis
    • Regeneration
    • Seedling
    • White pine blister rust
    • Whitebark pine
    • Wildfire

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