The extension and structure of functional traits variation in response to different soil factors between invasive and native plants are poorly understood. Functional traits and soil factors of the invasive plant Amaranthus palmeri and its coexisting plant Polygonum orientale are investigated under three heterogeneous habitats: roadside (rs), wasteland (wl), and riverbank (rb) in Tianjin, China. The shoot dry weight (SDW) and leaf nitrogen (LN) of A. palmeri are significantly higher compared with P. orientale, while A. palmeri has significantly lower leaf dry weight (LDW), leaf area (LA), leaf carbon (LC), and leaf C/N ratio under different habitats. The larger phenotypic plasticity of A. palmeri is one of the important reasons for their successful invasion to heterogeneous habitats. Similarly, the soil water content (SWC) of both species shows a significant difference (p < 0.05) with maximum in riverbank habitat to lowest in roadside habitat. Soil N/P ratio, C/N ratio, and C/P ratio of rb habitats are significantly lower compared to wl and rs habitats (p < 0.05). A redundancy analysis indicates that SWC is the dominant soil factor affecting the functional traits of A. palmeri and P. orientale. However, A. palmeri forms an environmental adaptation strategy by changing traits of SDW, LN, and leaf C/N ratio, which is different from P. orientale by changing traits of LA and LDW.

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The impact of A. palmeri invasion on soil bacterial community under different habitats is unclear. In this work, the influence of A. palmeri invasion on soil bacterial diversity and community structure were investigated using full-length 16S rRNA sequencing technology under four typical habitats of riverbank (A), roadside (B), wasteland (C) and farmland (D). A two-way ANOVA analysis showed that habitat, invasion and the interaction of them had little effect on alpha diversity, expect for habitat factor had a significant effect on Simpson indices (P<0.05). NMDS analysis demonstrated that soil bacterial community structures among different invasive habitats were clearly distinguished. In addition, the most abundant phyla in the non-invasive plots were Proteobacteria, Planctomycetes and Gemmatimonadetes. However, the third predominant phyla converted from Bacteroidetes to Gemmatimonadetes with the invasion of A. palmeri. LEfSe analysis revealed that the core microbiome, Burkholderiaceae and Betaproteobacteriales (riverbank habitat), Gemmatimonadetes and Gemmatimonadaceae (wasteland habitat), Sphingomonas_sediminicola (roadside habitat), Nitrosomonadaceae (farmland habitat), which played important roles in facilitating the establishment of A. palmeri to heterogeneous habitats.