DIFFERENCES IN RIPARIAN VEGETATION STRUCTURE BETWEEN GRAZED AREAS AND EXCLOSURES

Differences in vegetation structure were examined in a montane riparian zone in N-central Colorado after 30 yr of cattle exclusion and continued, but reduced, grazing pressure. Total vascular vegetation, shrub, and graminoid canopy cover was greater in the exclosures as compared to grazed areas, while forb canopy cover was similar between treatments. Exclosures had nearly 2 times the litter cover, while grazed areas had 4 times more bare ground. Willow canopy coverage was 8.5 times greater in protected areas than in grazed areas. Kentucky bluegrass Poa pratensis cover was 4 times greater in grazed areas than exclosures, while the cover of fowl bluegrass Poa palustris was 6 times greater in the protected sites. Canopy cover of other important riparian species was similar between treatments. Mean peak standing crop was 2410 kg/ha in exclosures and 1217 kg/ha in caged plots within grazed areas. Cattle utilized c65% of the current year's growth of vegetation during the grazing season. -from Authors