The water demand for seed germination, plant growth, and reproduction in A. artemisiifolia and A. trifida(Experiment 4)
The seed germination rates of A. artemisiifolia and A. trifida increased with increasing soil moisture. However, no significant difference in seed germination rate was observed when comparing these two species under the same soil moisture content (Table 3).
Under 560 and 840 mm of simulated annual precipitation, A. artemisiifolia and A. trifida both grew better than under 280 mm of annual precipitation during the growing period. The growth ofA. trifida was very poor, with a low seed yield, whereas A. artemisiifolia grew better than A. trifida under 280 mm of annual precipitation. When comparing plants experiencing 840 mm of simulated rainfall and 280 mm of annual precipitation during the growing period, the densities and plant heights of these two species were not significantly different in ES. From the FR to MR, the density, plant height, and seed yield of A. trifida decreased more than those ofA.artemisiifolia . In FR, the density and plant height of A. trifida decreased by 88.5% and 74.5%, respectively, while those ofA. artemisiifolia decreased by 24.5% and 21.6%, respectively (Fig. 6). The seed yield per m2 of A. trifidadecreased from 50,185 to 19, while that of A. artemisiifoliadecreased from 15,579 to 530 (Table 4).