Edaphic Variables Affecting Vegetation Pattern

The soils under four small plant communities were studied to determine the cause of vegetation heterogeneity within a designed Buchloe-Bouteloua community. Sixteen replicate stands, four each of big bluestem (Andropogon gerardi), western wheatgrass (Agropyron smithii), blue grama (Bouteloua gracilis), and buffalograss (Buchloe dactyloides), were within 4.8 hectare of a loamy upland area in the Mixed Prairie of western Kansas. Each replicate’s soil was profiled four times and twelve separate soil factors were analyzed on the A and B-horizons of each of the 64 profiles. All soil factors studied, except nitrogen, played a part in the soil differences found under the four communities and were considered to constitute environmental differences. Mature soil profiles produced short grass communities and immature soil profiles produced tall and mid-grass communities. Depth of A-horizons increased significantly from buffalograss to blue grama to western wheatgrass to big bluestem. Available water and mean weight diameter determinations contradict hypotheses of a moisture gradient but were considered to be greatly affected by accumulation of mulch. Soil texture influence was the greatest in the B-horizons of the mature soils. Cation exchange capacity was noted mainly as being limited in the A-horizons of blue grama profiles. Available phosphorus and potassium were inversely related and significantly different in the A-horizons of each community. The vegetation heterogeneity was definitely separated by soil heterogeneity.