Advance of Trees and Krummholz Into Alpine Tundra
* Malanson, G P (george-malanson@uiowa.edu) , University of Iowa, Department of Geography,
Iowa City, IA 52242 United States
Zeng, Y (yu-zeng@uiowa.edu) , University of Iowa, Department of Geography, Iowa City, IA
52242 United States
Butler, D R (db25@txstate.edu) , Texas State University, Department of Geography, San Marcos,
TX 78666 United States
Resler, L M (resler@vt.edu) , Virginia Tech, Department of Geography, Blacksburg, VA 24061
United States
Invasion of alpine tundra by trees is an expected outcome of climatic change, but observed
responses are equivocal. To examine the invasibility of tundra we consider what might limit or
facilitate seedling establishment and subsequent development into krummholz or trees. At the
seed stage barriers to success include landing on an impenetrable surface. Many tundra sites are
underlain by active or relict solifluction, however, and data show that these sites present
opportunities for the exposure of fine soil through turf exfoliation on tread-riser boundaries. At
the seedling stage negative and positive feedbacks are both present. A simulation with negative
feedback in dense trees and positive feedback with fewer trees produces an advance of trees into
tundra in which the rates vary in correlation with a fractal spatial pattern, not climatic change.
Because the spatiotemporal patterns of tree advance into tundra will be related to climatic change
nonlinearly and will, to some degree, be controlled by geomorphic conditions, places may
respond individualistically.