Effects of toxic plants on soil physicochemical properties and soil microbial abundance in an alpine meadow on the Qinghai-Tibetan Plateau

The fast spread of toxic plants promoted by ongoing grassland degradation has become a serious threat to plant diversity and productivity in alpine meadows on the Qinghai-Tibetan Plateau (QTP) in China. The impacts of toxic plant invasions on plant community characteristics have been well defined, but studies into their effects on belowground organisms and processes are rare. In this study, we investigated the effects of five dominant toxic plants growing in an alpine meadow grassland on the QTP (Oxytropis kansuensis, Stellera chamaejasme, Thermopsis lanceolata, Gentiana straminea, and Ligularia virgaurea) on soil parameters and microbial abundance. We also compared these effects with a non-toxic forage grass Elymus nutans. The results indicated that, compared to E. nutans, all toxic plants tested, except G. straminea, significantly increased total soil carbon, total soil nitrogen, and microbial biomass carbon (P < 0.05). The soil pH was not effected by plant species. The toxic plants tested in this study had significant effects on the abundance of soil bacteria, ammonia oxidizing bacteria, and denitrifying bacteria (P < 0.05), whereas the abundance of fungi was not affected by the toxic plants. These results indicated that the spread of toxic plants on the QTP could be of significant consequence to belowground soil properties, functions, and microorganisms, and they could have a significant effect on grassland productivity.