Stoichiometric characteristics of two Asteraceae invasive plants at different invasive degrees and its influencing factors
Alien invasive plants are commonly stated to pose a threat to populations of native plants,especially of endangered species.Resource allocation and nutrient strategies are important mechanism of invasion for alien plants.In order to investigate the distribution pattern,uptake and utilization strategies of invasive plants and their invasive,the carbon(C),nitrogen(N)and phosphorus(P)and biomass of the modules of invasive plants Praxelis clematidea and Synedrella nodiflora at different invasive degrees from eastern Guangdong were measured,and further the stoichiometric characteristics,allocation of nitrogen and phosphorus and relationship with soil factors were measured.The results were as follows:(1)Available nitrogen(AN)content in soil declined with increasing of invasive degree for Praxelis clematidea,and the N,P,AN contents in soil declined with increasing of the invasive degree for Synedrella nodiflora.The content of N(0.696-2.701 g·kg-1)in soil of invasive habitat for Praxelis clematidea was greater than that for Synedrella nodiflora(0.189-0.337 g·kg-1),and the mean contents of C,P,available nitrogen(AN),and available phosphorus(AP)for Praxelis clematidea were less than those for Synedrella nodiflora.(2)For two plants with different invasive degrees,the N distribution for leaves was more than that for stems,and than roots.The P for Praxelis clematidea was distributed more to the stems,and for Synedrella nodiflora to the stems and leaves.The roots and stems of Praxelis clematidea,and leaves of Synedrella nodiflora with mild invasion had low C∶P and N∶P values than severe invasive degree,indicating two plants with mild invasion may have fast relative growth rate,and strong expansion potential.The N∶P values in leaves for two plants were greater than those in roots and stems,implicating that roots and stems may have fast relative growth rate to increase the competitiveness of underground and above-ground.(3)The C∶P and N∶P values in roots and stems of Praxelis clematidea at different invasive degrees were less than those of Synedrella nodiflora,while the C∶P and N∶P values in leaves of Synedrella nodiflora were less than that of Praxelis clematidea,showing that although the roots and stems of Praxelis clematidea may have faster relative growth rate,Synedrella nodiflora had faster relative growth rate and stronger invasion potential than Praxelis clematidea.(4)The allocation of nitrogen and phosphorus,and relative growth rate of alien plant Praxelis clematidea were mainly affected by AN,AP contents in soil,that relative growth rate of organs increased with increasing of AN,AP contents in soil.The allocation of nitrogen and phosphorus,and relative growth rate of alien plant Synedrella nodiflora were mainly affected by N,P contents in soil,that relative growth rate of organs increased with increasing of N,P contents in soil.In conclusion,the roots and stems of two Asteraceae alien species have fast relative growth rate,and further to increase the competitiveness of underground and above-ground,but their possible effect on N∶P stoichiometry requires further study.The results of this study have guiding significance for further understanding of resource allocation and utilization strategies and prediction of invasive potential of alien plants.
alien speciesecological stoichiometryallocation of nitrogen and phosphorusnutrition strategyinvasiveness
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