Invasive root growth into disturbed soil of two tussock grasses that differ in competitive effectiveness

When soil gaps were created by removing a neighbouring tussock, the rate of root invasion into this space was more rapid for the grass of greater competitive ability, Agropyron desertorum than for Agropyron spicatum. Both species invaded gaps created later in the spring more rapidly than those created soon after snow melt. Acquisition of ³²P placed in a soil gap varied greatly among individual tussocks of the same species that bordered the gap, even though the shoots of the tussocks were approximately the same distance from the radio-active soil and were of similar biomass. Total ³²P acquisition from the gap was similar for the 2 grass species when the gap was created soon after the snow melted. Radiophosphorus acquisition tended to be greater for A. desertorum when the gap was created later in the spring. Rapid root growth into soil gaps can allow a plant to occupy a greater soil volume and soil microsites richer in resources, but greater resource acquisition due to this rapid root growth may not be immediately apparent. -from Authors