Effects of defoliation and competition on the post-fire response of Poa ligularis Ness. in semi-arid central Argentina

The objectives of the study were to evaluate the effects of defoliation on tiller growth of Poa ligularis Ness. at two different intervals after fire as well as how recovery is affected by different levels of herbaceous interspecific competition during the subsequent growing season. Early post-fire defoliation (6 months after burning) reduced (P < 0.05) the height, number of green leaves and total green length of tillers on P. ligularis in comparison to Control plants. Late post-fire defoliation (12 months after burning) did not affect any of these growth attributes. Burnt plants of P. ligularis exposed to the no competition treatment (NC) had a higher number of green tillers per plant than plants exposed to the total competition treatment (TC). Moreover, the burnt plants exposed to the NC were significantly taller (P < 0.05) than plants exposed to TC. The highest (P < 0.05) above-and belowground biomass was recorded in those burnt P. ligularis plants growing in the NC treatment. Our results provide some evidence to show that early defoliation and interspecific competition after fire reduce the tiller growth and also the above-and belowground biomass of P. ligularis plants.