Increased nitrogen deposition increased the competitive effects of the invasive plant Aegilops tauschii on wheat

Abstract

Based on an external nitrogen source NH4NO3, the impacts of different nitrogen deposition treatments (i.e., CK, N5, N10, and N15) on the growth of the A. tauschii and its competition with wheat were investigated. This experiment was conducted in pots using simulated N deposition tests. The results showed that: (1) the plant height, leaf area, and tiller number of both monocultured and mixed planted A. tauschii and wheat increased gradually with increasing nitrogen deposition. In the same nitrogen deposition treatment, the tiller number of A. tauschii was significantly higher than that of wheat. (2) In both monoculture and mixed planting pots, the root biomass and root–crown ratios of A. tauschii to wheat decreased with increasing nitrogen deposition. However, the leaf–biomass ratio of the former showed a gradual increasing trend with increasing nitrogen deposition. (3) Under monoculture and mixed planting modes, the chlorophyll content of A. tauschii increased consistently with increasing nitrogen deposition, but the chlorophyll content of wheat first increased and then decreased. Moreover, the SOD activity, relative conductivity, and MDA content of A. tauschii and wheat constantly increased with increasing nitrogen deposition. (4) In the mixed planting pots, the relative yield of A. tauschii was > 1. The competition balance index of this plant was > 0 and increased with increasing nitrogen deposition. In a nutshell, the ability of A. tauschii to compete with wheat is gradually enhanced with increasing nitrogen deposition; and its adaptability to high nitrogen stress surpasses that of the latter.