Distribution differences between A. artemisiifolia andA. trifida (Experiment 1)
Ambrosia artemisiifolia and A. trifida invaded the Yili Valley starting in 2010. Since 2014, the areas occupied by these two species have increased rapidly, although A. artemisiifolia is distributed over a larger area than A. trifida . By 2017, these two species had occupied 1322 and 311 km2, respectively; thus, the former occupied 4.25 times the area inhabited byA. trifida (Fig. 1).
The species abundances were measured in the 25 plots in each habitat. From 2010 to 2017, the abundance of A. artemisiifolia was higher than that of A. trifida and increased rapidly in farmland ecotone, residential area, and roadside habitats. By 2017, total abundance of A. artemisiifolia and A. trifida were 57% and 39%, respectively, so that A. artemisiifolia was 1.46 times more abundant than A. trifida . However, the abundance of A. artemisiifolia in grassland was less than that of A. trifida , where the latter was 3.5 times more abundant than the former (Fig. 2).