Root chemistry of mature Douglas-fir differs by habitat type in the interior northwestern United States

Carbon compound concentrations in plant tissues depend on the environment i n which plants grow. However, little is known about how these concentration s vary across a range of forest environmental conditions. Our study examine d root tissue (phloem, cambium, phellum, and phelloderm) collected from nat urally regenerated mature Douglas-fir (Pseudotsuga menziesii var. glauca, [ Bessn.] Franco) trees in eight stands on three habitat type series encompas sing a range of temperature and moisture conditions. The objective was to d etermine root chemical composition (sugar, starch, phenol, and tannin) diff erences among the habitat types. Douglas-fir roots collected from dry, warm Douglas fir habitat types had sugar concentrations of 4% compared to 3% fo r roots from cool, moist habitat types. Root samples collected from Douglas -fir habitat types showed tannin concentrations about double those from gra nd fir or western redcedar habitat types. Phenol/tannin ratios for the cool , moist habitat types were about double those from warm, dry Douglas-fir ha bitat types. Roots sampled from western redcedar habitat types had phenol c oncentrations and phenol/ sugar ratios more than 50% higher than those from Douglas-fir and grand fir habitat types. We speculate that root chemistry of Douglas-fir growing on Douglas-fir habitat types could make them more dr ought resistant but less disease resistant, while Douglas-fir growing on we stern redcedar types would be less drought resistant but more disease resis tant. Douglas-fir growing on warm, dry sites allocated more carbon to tanni n production and less to phenols.