The preference of nitrogen forms may affect the plant community structure and change the nitrogen competition among plants. The increasing nitrogen deposition in the environment will greatly affect the invasion process, and knowing how the plant soil feedback work under different nitrogen forms can help us understand the invasion process more in-depth. Bidens alba has invaded southern China. Although B. alba is a nitrate preference plant, it has the potential to maintain its growth advantage under greater ammonium conditions (i.e. ammonium-to-nitrate ratio is greater than 1). Is it the growth advantage under greater ammonia conditions due to positive plant-soil feedback? And what does the role of ammonia oxidizers play in changing nitrogen forms? In this study, we selected three plant species (nitrate preference invasive species Bidens alba; nitrate preference native species Bidens pilosa, and ammonia preference native species Wedelia chinensis). Different inorganic nitrogen forms (NO3-, NH4+) were simulated through different ratios of ammonium to nitrate, where the plants were grown under monoculture and mixed culture for 5 months with pot experiment. To understand the reason why the nitrate preference plant species has the potential to maintain its growth advantage under greater ammonia conditions, the differences in changes of rhizosphere ammonia-oxidizing flora and soil environment among the three species were compared.
Results/Conclusions
Our results showed that different nitrogen forms (different ratios of ammonia to nitrate) could significantly change soil physico-chemical properties, such as pH, ammonium nitrate-N and the abundance of AOA under certain treatments. Due to the change of soil physical and chemical properties and soil microbial, the biomass, root/shoot ration and specific leaf area can be explained under different degrees. This indicates that ammonia oxidizers may play an important role in invasive process.The changes of soil pH, ammonium nitrogen and nitrate nitrogen and the abundance of ammonia oxidizing aechaea were significantly correlated with plant biomass, root/shoot ratio and specific leaf area.