In Far East Asia, coastal dune forests dominated by the conifer Picea glehnii represent a rare plant community type. A P. glehnii forest and adjacent plant communities on the dunes of the Syunkunitai sand spit, Hokkaido, northern Japan were examined. Using the basal area of P. glehnii and Abies sachalinensis stems measured in a belt transect across a portion of the sand spit, we identified three plant community zones: SALT MARSH, PICEA, and ABIES. The three zones were distributed along a topographic gradient that was associated with differences in water table depth, salinity, and pH of soil pore water. Nearly pure stands of P. glehnii grew on a relatively level portion of the sand dune where the ground-water-table level was shallow (−10.9 to −26.3 cm, without isolated depressions). The salinity of the soil pore water was significantly lower than that in the adjacent salt marsh (Dunnett's T3, P = 0.047). The A. sachalinensis community grew on the upper slope and ridge of the dune where the ground-water-table was significantly lower (P = 0.003) than in the P. glehnii forest. Our results show that the boundary between the P. glehnii forest and the salt marsh community is determined primarily by the salinity of the soil pore water, whereas the boundary between the P. glehnii and A. sachalinensis forests is determined by the ground-water-table depth and the pH of the soil pore water. Because of continual ground subsidence, the salt marsh community and P. glehnii forest will likely be submerged within 50 and 100 years, respectively.