Comparative Studies Of Nitrogen Transformation In Rhizosphere Soil Of The Invasive Plant Xanthium Strumarium And Its Native Congener X.sibiricum

With the acceleration of globalization,alien plant invasion has become one of the ecological problems that could not be ignored.However,most of the studies on invasive plants are focused on the aboveground ecosystems,while little effort has been made to study underground ecosystems,especially soil nitrogen transformation.Nitrogen is one of the indispensable elements for plants.Soil nitrogen transformation directly determines the availability of soil nitrogen,and then affects plant growth and development.With the progress of the researches on alien plant invasions,it is recognized that the influence of alien plants on soil nitrogen transformation may be one of the important mechanisms to promote successful invasions.In this study,the invasive species Xanthium strumarium L.and its native vongener X.sibiricum Patrin ex Widder were used as experimental materials.We studied the effects of soil organic matter contents and activated carbon addition on the differences in growth and soil nitrogen transformation between the two plants at vegetative and reproductive stages.The main conclusions are as follows:The accumulation of aboveground,underground and total biomass of X.strumarium was better than X.sibiricum at different stages.The root-shoot ratio of X.strumarium increased under low nutrient conditions.Generally speaking,the addition of activated carbon decreased the nitrogen conversion rate in the rhizosphere soil of the two plants at different stages;the increase of organic matter increased the nitrogen transformation rate in the rhizosphere soil of the two plants at different stages,and X.strumarium was less affected than X.sibiricum.Under high organic matter,the transformation rate of soil around the root of X.sibiricum was higher than that of X.strumarium on the whole;under low organic matter,especially during reproductive growth stage,the transformation rate of rhizosphere soil of X.strumarium was higher than that of X.sibiricum on the whole.X.strumarium and X.sibiricum reduced the content of soil ammonium,increased the ratio of soil nitrate to ammonium,and increased the proportion of soil nitrate nitrogen.During reproductive growth stage,urease activity in soil of X.strumarium was significantly higher than X.sibiricum.In conclusion,X.strumarium is superior to X.sibiricum in growth.The advantage of urease activity and nitrogen transformation under low organic matter in X.strumarium soil during reproductive growth stage may be the reason for promoting invasion of X.strumarium.