Effects of simulated grazing by below-ground herbivores on growth, CO2 exchange, and carbon allocation patterns of Bouteloua gracilis.
A series of root-pruning experiments was performed to simulate the effects of grazing by root-feeding herbivores on B. gracilis. Approx. 37% (c. 22 mg) of the root biomass of hydroponically grown plants was removed by cutting all roots 5 cm below the crown bases. Total biomass of root-cut plants (908 mg) was 20% lower than that of controls (1137 mg) 3 wk after treatment. This biomass reduction was related to a 55% reduction in tiller production of treated plants. The mean rate of net photosynthesis of treated plants was 35% lower than in control plants for the 1st 6 days after treatment. For several days following root-cutting, the proportion of photosynthetically-fixed 14C allocated to roots was lower than in control plants, but this proportion increased until, by 3 wk after treatment, the proportion allocated to roots of treated plants significantly exceeded that of controls. Because of these effects on plant growth and metabolism it is suggested that belowground herbivores may control primary production to a greater extent that would be predicted from their biomass or consumption rates.