| Popis: |
(1) A series of root-pruning experiments was performed to simulate the effects of grazing by root-feeding herbivores on Bouteloua gracilis. Approximately 37% (% 22 mg) of the root biomass of hydroponically grown plants was removed by clipping all roots 5 cm below the crown bases. (2) Total biomass of root-clipped plants (908 mg) was 20% lower than that of controls (1137 mg) 3 weeks 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 first six days after treatment. For several days following root-clipping, the proportion of photosynthetically-fixed 14C allocated to roots was lower than in control plants, but this proportion increased until, by 3 weeks after treatment, the proportion allocated to roots of treated plants significantly exceeded that of controls. (3) Because of these effects on plant growth and metabolism, we suggest that below-ground herbivores may control primary production to a greater extent than would be predicted from their biomass or consumption rates. |
