Vegetation of Exclosures in Southwestern North Dakota

Abstract

A 3-year study of the vegetation in 4 livestock exclosures was begun in 1976 in the mixed grass prairie of southwestern North Dakota. Three of the exclosures were established in 1937 and the fourth in 1938. The exclosures had greater graminoid leaf heights and greater mulch accumulations than the adjacent grazed plots; however, total yield and total belowground biomass were not significantly different between plots in 3 out of the 4 sites. The major difference between the exclosures and the adjacent grazed plots was species composition. The production of blue grama (Bouteloua gracilis (H.B.K.) Griffiths) was lower, and the production of thread-leaf sedge (Carex filifolia Nutt.) and another sedge (Carex heliophila Mack.) was greater in the exclosures than on the adjacent grazed plots. A summary by growth form also showed that the midgrass and tallgrass growth form category was more dominant in only 1 out of 4 exclosures. The interpretation of these data indicates that the potential for changes in growth form dominance and total yield due to management inputs must be evaluated on a site specific basis. Species composition also was a more reliable indicator of successional status than growth form dominance.