Aboveground Productivity and Floristic Structure of a High Subalpine Herbaceous Meadow

Abstract

The aboveground primary productivity within each of four areas, differing in length of the snow-free season, was determined in a high subalpine (3380 m) herbaceous meadow in Colorado. Net productivity, minus losses to herbivores, ranged from 114 g · m⁻² · yr⁻¹ in the area with the shortest snow-free period, to maximum values of 192 g · m⁻² · yr⁻¹ in areas with snow-free periods of intermediate length. Caltha leptosepala and Senecio crassulus, the only dominant forb species common to all four areas, showed differing patterns of productivity within and between areas. Domestic sheep may have removed up to 38% of the peak standing crop within the study area during 6 h of grazing. Variation in dominance-diversity curves among the four areas suggests that the effect of snow cover in controlling the length of the growing season may be less important than its influence on moisture availability in determining the overall structure of this subalpine community.