CLONAL ARCHITECTURE OF SALIX-SETCHELLIANA (GRAVEL BAR WILLOW) IN ALASKA

Clones of Salix setchelliana were excavated to describe the architecture of this prostrate clonal species and to determine if there are architectural parameters or clonal growth forms that vary with clonal age. The species' gravel-bar habitat, a mosaic of previous river channels, is unpredictable in time and variable in space. Clones are composed of vertical shoots connected by horizontal roots. Because clones expand by peripheral growth of their root systems, the six studied clones could be placed in order of apparent increasing age, primarily on the basis of size. Substrate was removed by hand and the horizontal root systems mapped. Data on shoots, root branch angles, and root peripheral growing points were recorded. Several density parameters were calculated and examined for trends along the sequence of apparent increasing clonal age. Most measures of shoot density increased along this sequence, as did horizontal root system density and the linear density of horizontal root system branching points. Clones appear to change in time from a "guerrilla" growth form of environmental exploration to more of a "battalion" growth form with increased branching of the underground system.