The effect of severe defoliation on the subsequent growth and development of five rangeland pasture grasses of south‐western Queensland

Abstract

AbstractYoung plants of five arid zone grasses. Cenchrus ciliaris, Astrebla lappacea, Artstida armata, Thyridolepis mitchelliana, and Digitaria ammophila, were heavily defoliated and their subsequent regrowth and development monitored and compared with that of intact plants. Defoliation impaired the development of both roots and plant tops in all species. Regrowth was inconsistent with theories of assimilated reserves stored in roots to support regrowth. The species differed in their apportionment of assimilate between competing plant parts. The differences were similar in both intact and defoliated plants. Both C. ciliaris and A. lappacea maintained a large root mass but produced few inflorescences whereas A. armata and D. ammophila did the opposite. T. mitchelliana had an intermediate pattern of allocation. Both D. ammophila and A. armata resumed flowering soon after defoliation. The different reactions to defoliation are discussed in relation to historical deterioration in pasture condition which may be linked with the prolific seeding capacity of A. armata.