Wood nitrogen isotope composition ( delta super(15)N) provides a potential retrospective evaluation of ecosystem N status but refinement of this index is needed. We calibrated current wood delta super(15)N of Douglas-fir (Pseudotsuga menziesii), an ectomycorrhizal tree species, against a productivity gradient of contrasting coastal forests of southern Vancouver Island (Canada). We then examined historical delta super(15)N via increment cores, and tested whether wood delta super(15)N corresponded with climatic fluctuations. Extractable soil N ranged from 11 to 43 kg N ha super(-1) along the productivity gradient, and was characterized by a progressive replacement of N forms (amino acids, NH sub(4) super(+) and NO sub(3) super(-)). Current wood delta super(15)N was significantly less depleted (-5.0 to -2.6 ppt) with increasing productivity, although linear correlations were stronger with Delta delta super(15)N (the difference between wood and soil delta super(15)N) to standardize the extent of isotopic fractionation by ectomycorrhizal fungi. An overall decline in wood delta super(15)N of 0.9 ppt over the years 1900-2009 was detected, but trends diverged widely among plots, including positive, negative and no trend with time. We did not detect significant correlations in detrended wood delta super(15)N with mean annual temperature or precipitation. The contemporary patterns in stand productivity, soil N supply and wood delta super(15)N were moderately strong, but interpreting historical patterns in delta super(15)N was challenging because of potential variations in N uptake related to stand dynamics. The lack of wood delta super(15)N correlations with climate may be partly due to methodological limitations, but might also reflect the relative stability in N supply due to the overriding constraints of soil organic matter quantity and quality.