VASCULAR PLANT-SPECIES RICHNESS IN GRAZED AND UNGRAZED COASTAL MEADOWS, SW FINLAND

The richness of vascular plant species in four grazed and five ungraze d shore meadow communities was studied on the west coast of Finland, n ear the town of Pori (61 degrees 30'-61 degrees 33'N, 21 degrees 28'-2 1 degrees 41'E). In the transects established, plant species were stud ied in 412 1-m(2) plots and in the adjacent areas. The flora included a total of 183 vascular plant species representing 108 genera. The sho re plant communities were dominated by perennial monocot species, alth ough the number of dicot species was higher. The vascular plant specie s richness (11.5 +/- 4.7) in 1-m(2) sample plots was significantly hig her at the seashore than in the delta of the river Kokemaenjoki. A mod el is constructed of the factors that affect species richness in seash ore meadows. Species richness increased significantly with increasing distance from the waterline, and more importantly (R-2 = 0.26) with el evation above the mean sea level. The linear increase in species richn ess continues up to a certain elevation, the latter being dependent on the amplitude of water level fluctuation. Species richness decreased significantly with an increase in biomass or height of vegetation. The se variables are negatively correlated with elevation and have only se condary importance for species richness. In the delta area no signific ant results were obtained for species richness in general. The vascula r plant species richness was higher in grazed plots than in ungrazed o nes in the delta, but in the transects most exposed by the sea the opp osite was true. The influence of grazing on the species richness seeme d to be scale-dependent.