Spatial legume composition and diversity across seeded landscapes
2001
Pastures typically have diverse landscapes, and resulting soil conditions and plant composition can vary within small area units. This study was performed to quantify the spatial variation in legume contribution to the plant community when seeded into established perennial cool-season grass pastures. Pastures were interseeded with an 11-legume mixture and divided into three stocking methods (continuous, rotational, and nongrazed), with each stocking method containing five landscape positions (summit, backslope, toeslope, opposite backslope, and opposite summit). Grass and legume components were sampled three times annually between 1996 and 1998. Backslopes had greater legume dry matter (DM) composition (161 g kg(-1)) than either summit (62 g kg(-1)) or toeslope positions (7 g kg(-1)), and total legume concentrations increased over years. Legume composition consisted mostly of red clover (Trifolium pratense L.), birdsfoot trefoil (Lotus corniculatus L.), and white clover (T. repens L.). Species richness and Shannon-Weiner diversity index (H'(dm)) for the legume functional group were also greatest on backslope landscape positions, especially in continuously and rotationally stocked pastures. Legume DM composition showed a positive linear relationship with legume species richness in continuous, rotational, and nongrazed pastures (r2 = 0.76). The H'(dm) showed a positive linear relationship with legume DM composition in only rotationally stocked paddocks (r2 = 0.88). The legume component at grazed backslope sites filled a niche left unoccupied by the grass component. Species and site recommendations for pasture improvement and management should be made based on landscape position and stocking method.
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