RESPONSE OF STEPPE RIPARIAN AREAS TO THE EXCLUSION OF CATTLE-GRAZING: COMPARISONS AT DIFFERENT SPATIAL AND TEMPORAL SCALES

摘要

Changes over one grazing season and data from a 5-year study were used to evaluate the impact of cattle-grazing on the structure and composition of plants in steppe riparian areas. For one growing season, comparison of areas exposed to grazing and areas released from grazing indicated that the areas exposed to grazing had a significantly different structure, less aboveground biomass, and greater heterogeneity in soil nutrients than did nongrazed areas. The 5-year study showed that compositions of species between grazed and nongrazed areas were different at the onset. Over time, additional variations in diversity and composition of species between the grazed and nongrazed areas occurred but did not change significantly. This suggested that environmental factors were affecting these areas more than grazing. Impacts on steppe riparian vegetation were minimal at the intensities of grazing investigated.