A Study of High Elevational Grassland Com- munities in Western Montana'

Grassy balds in the Bitterroot Mountains of western Montana were studied to document their occurrence, to establish their present distributional patterns and to determine the stability of these grasslands within the subalpine forest zone. Daubenmire's (1959) canopy-coverage method was used in sampling the vegetation of the balds. Weekly soil moisture and temperature readings were recorded for the duration of the study, and chemical and mechanical analyses were done on the soils. The inability of tree seedlings to become established on the balds is related to annual summer drought. In areas of low annual precipitation, the limited moisture is not adequate for seedling development on the coarse soils of southern exposures. Even where an- nual precipitation is adequate, the grasslands are dry, because they are underlain by rock which creates characteristic drainage patterns and sharp ecotones and limits the vegetation of these areas to a grassland climax.