| Flaveria bidentis, a new worst weed in China, was firstly found in2001in Tianjin and Hengshuicity of Hebei province. It has now spread quickly and became one of the most dangerous invasive plantsin north China. Ecological stoichiometry was a discipline combining with the basic principles of theecology, chemistry and physics, which studied the balance of energy and chemical elements (C, N and P)in ecology system. In order to provide the reference on the prevention and control of this exotic specie,the invasive mechanism of F. bidentis from physiological and ecological characteristics, energyutilization strategy and leaf element stoichiometric characteristics were investigated in present study.1. To analysis growth restrictive elements of F. bidentis, three habitats (â… : waterside, â…¡: cropland,â…¢: wasteland) were selected to study the stoichiometric characteristics and relationship of plant leaf andinvaded soil. In these habitats, invaded soil C, N, C:P, N:P were â…¢>â… >â…¡, P wasâ… >â…¡>â…¢, and C:Nwas â…¢>â…¡>â… (P<0.05); The leaf C content had no significant difference, â… significantly higher than â…¡and â…¢ in N or P, but â…¡ and â…¢ were significantly higher than â… in C:N, C:P, N:P (P<0.05). The soil P orC:N was significantly positive correlation with the leaf, no significant correlation with the C, C:P, N:P.The soil C was significantly positive correlation with N, no significant correlation with the C-P, N-P.The leaf N was significantly positive correlation with P, while C-N and C-P were no significantcorrelation. The change was synchronous between soil organic matter and N. N was growth restrictiveelement of F. bidentis growing in the â… habitat, while it was P in the â…¡and â…¢habitats.2. Leaf construction cost (CC) is a quantifiable measure of energy demand for leaf construction, andreflects energy utilization strategy of plant. Lower CC is hypothesized to give plant invaders a growthadvantage through efficient energy utilization. In this study, F. bidentis and five co-occurring nativeplants (Xanthium sibiricum, Amaranthus retroflexus, Setaira viridis, Chenopodium glaucum and Vignaradiata) were selected to compare their difference in leaf CC and related characteristics. The resultsshowed leaf CCmassof F. bidentis was the lowest, which represents76.6%of average of fiveco-occurring plants. Likewise, leaf CCareawas notably lower than others except for S. viridis, making74.4%of average of five co-occurring plants. Both leaf carbon and nitrogen concentration of F. bidentiswere significantly lower than that of most of co-occurring plants. However, ash content of F. bidentiswas significantly higher than co-occurring plants, while its leaf Hc was significantly lower thancompared co-occurring plants with exception of C. glaucum. Futhermore, there was a positiverelationship found between the leaf CCmassand carbon concentration or Hc in six species, but notablenegative correlation exist between the leaf CCmassand ash content. In conclusion, the lower leaf CC of F.bidentis was associated with its lower leaf carbon concentration and Hc, higher ash content relative to itsco-occurring plants, which might be partially explained for its successful invasion.3. In a greenhouse, we studied the effect of soil N, P addition on F. bidentis plant growth, N, Pstoichiometry characteristics and plant functional traits (leaf chlorophyll content). The results showedthat the effect of different soil N or P level on leaf N:P was significantly different with equivalent N and P addition, and F. bidentis leaf N:P was decreasing with the increase of soil N, P nutrient content.Compared with CK (1N1P), leaf N:P decreased significantly after soil N, P addition. Furthemore, theN has higher effect on leaf N:P that of soil P element. Leaf chlorophyll content of F. bidentis had asignificant positive correlation with soil N content, leaf N content and leaf P content as well, soil Ncontent has the biggest direct effent on soil N content, and leaf N content has greatest indirect effect.Both F. bidentis leaf N (P) content and aboveground biomass were increasing firstly and falling laterwith the increase of soil N (P) content. In this result, inflection point of soil N element was respectively3.42g/kg and3.76g/kg with a variation range of9.94%, while inflection point of soil P element was1.80g/kg and1.97g/kg, respectively, with a variation range of9.44%. Leaf N:P <20.86was N-restrictive, and leaf N:P>22.88was P-restrictive, and value between this two mount was non-restrictive.Both leaf N:P and aboveground biomass had significantly reduced compared with CK after soil N, Paddition. When leaf N:P>22.88, high leaf N:P corresponding to low plant biomass meaned low rate ofplant growth, which was in line with the growth rate hypothesis. When leaf N:P<22.88, high leaf N:Pcorresponding to high plant biomass meaned low rate of plant growth, thus this predication did not meetthe growth rate hypothesis. |
PDF Full Text Request