A silvopastoral system using a Douglas-fir
(Pseudotsuga menziesii) tree crop and subclover (Trifolium subterraneum) as a nitrogen-fixing forage crop was
investigated near Corvallis, Oregon, during 1983-1985.
Treatments included all possible combinations of three
planting patterns (no trees, trees planted 2.5 m apart in a
grid, and clusters of five trees...