Landscape Ecology

, Volume 27, Issue 8, pp 1197–1212 | Cite as

Climatic, landform, microtopographic, and overstory canopy controls of tree invasion in a subalpine meadow landscape, Oregon Cascades, USA

  • Harold S. J. ZaldEmail author
  • Thomas A. Spies
  • Manuela Huso
  • Demetrios Gatziolis
Research Article


Tree invasions have been documented throughout Northern Hemisphere high elevation meadows, as well as globally in many grass and forb-dominated ecosystems. Tree invasions are often associated with large-scale changes in climate or disturbance regimes, but are fundamentally driven by regeneration processes influenced by interactions between climatic, topographic, and biotic factors at multiple spatial scales. The purpose of this research was to quantify spatiotemporal patterns of meadow invasion; and how climate, larger landforms, topography, and overstory trees have interactively influenced tree invasion. We combined airborne Light Detection and Ranging (LiDAR) characterizations of landforms, topography, and overstory vegetation with historical climate, field measurements of snow depth, tree abundance, and tree ages to reconstruct spatial and temporal patterns of tree invasion over five decades in a subalpine meadow complex in the Oregon Cascade Range, USA. Proportion of meadow occupied by trees increased from 8 % in 1950 to 35 % in 2007. Larger landforms, topography, and tree canopies interactively mediated regional climatic controls of tree invasion by modifying depth and persistence of snow pack, while tree canopies also influenced seed source availability. Landscape context played an important role mediating snow depth and tree invasion; on glacial landforms tree invasion was negatively associated with spring snowfall, but on debris flows tree invasion was not associated with snow fall. The importance of snow, uncertain climate change impacts on snow, and mediation of snow by interacting and context dependent factors in complex mountain terrain poses substantial hurdles for understanding how these ecotones may respond to future climate conditions.


Topography Oregon Cascades Snow Subalpine meadow Tree invasion LiDAR 



Funding was provided by: the USDA Forest Service, Pacific Northwest Research Station, Forest Inventory and Analysis Program; The Native Plant Society of Oregon, and the Hoener Memorial Fellowship program at Oregon State University. Special thanks to A. Gonsiewski for field data collection, K. Olsen for GIS assistance, and the Willamette National Forest. We thank C. Halpern, B. McCune, A. Gray, M. Wing, and two anonymous reviewers for providing helpful suggestions to improve this manuscript.

Supplementary material

10980_2012_9774_MOESM1_ESM.docx (1.5 mb)
Supplementary Material 1 (DOCX 1521 kb)
10980_2012_9774_MOESM2_ESM.doc (180 kb)
Supplementary Material 2 (DOC 180 kb)
10980_2012_9774_MOESM3_ESM.docx (26 kb)
Supplementary Material 3 (DOCX 25 kb)


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Copyright information

© Springer Science+Business Media B.V. (outside the USA) 2012

Authors and Affiliations

  • Harold S. J. Zald
    • 1
    Email author
  • Thomas A. Spies
    • 2
  • Manuela Huso
    • 3
  • Demetrios Gatziolis
    • 4
  1. 1.College of ForestryOregon State UniversityCorvallisUSA
  2. 2.Pacific Northwest Research StationU.S. Forest ServiceCorvallisUSA
  3. 3.Forest and Rangeland Ecosystem Science CenterU.S. Geological SurveyCorvallisUSA
  4. 4.Pacific Northwest Research StationU.S. Forest ServicePortlandUSA

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