Abstract
Salix interior Rowlee (INT), a wide-ranging North American willow from the small taxonomic group Salix sect. Longifoliae, is notable for its ability to form multi-stemmed vegetative stem colonies arising via root sprouts (RS) from a shallow horizontal root network. This study quantifies biomass production for both 1-yr-old coppiced plants and the original 4-yr-old plants, as well as for the RS stems associated with each ortet (original mother plant) using eight selected genotypes established on two distinct site types. Significantly greater coppiced and uncoppiced ortet stem dry mass was recorded on the coarse-textured, shale rock overburden (SO); possibly due to significantly greater fertility, compared to adjacent gravel outwash deposits (GD), which had greater RS stem mass. Significant clonal differences, as well as site type × clone interactions, were found for ortet stem dry mass, especially on SO sites, When expressed as a fraction of total stem dry mass produced on 2 m × 2 m biomass plots, the RS component represented a significant 57% of total stem dry mass per plot on GD sites. The use of colony-forming willows such as INT minimizes the need for periodic replanting, providing a cost advantage over conventional short-rotation, coppice-based woody biomass plantations using species that do not have the ability to reproduce via root sprouting.