Cuscuta campestris,a dodder,can parasitize and suppress a scrambling herbaceous to semi-woody perennial vine,Mikania micrantha,one of the most destructive weeds in the world.To assess the effects of the mixed residue of C.campestris and M.micrantha on the subsequent plant community,we conducted a one-year experiment on the germination and seedling growth of subsequent plant community after the application of C.campestris.Seven treatments of varying proportions of C.campestris and M.micrantha residue on 21 subject trees and shrubs,which were commonly found in South China,resulted in a germination rate of 35.3% for all 8 715 seeds from 18 species,ranging from 5.7 to 81.9%;the remaining 3 species failed to germinate.ANOVA analysis showed that the residue did not affect the germination,growth,or mortality of the trees and shrubs.The germinated C.campestris seeds from the residue coiled the seedlings of most of the species,but less than 4% host death caused by C.campestris.In addition,the residue did not affect the germination of the herbaceous seedlings originating from the loam,and the similarity coefficients of the germinated seedlings between the treatments were very high.These results suggested that the residue had no negative impact on the germination and early seedling stages of the tree,shrub and grass species of the subsequent plant community.The use of C.campestris residue had a positive effect on the growth of M.micrantha,but it did not change the trend of M.micrantha being suppressed because re-parasitization occurred soon after the growth restarted.No negative effect was detected on the other species as a result of the parasitization of C.campestris or by the use of the mixed residue.This suggests that C.campestris is likely to be an effective and promising ecologically safe native herbaceous agent for controlling M.micrantha.
LI Feng-lanLI Ming-guangZAN Qi-jieGUO QiangZHANG Wei-yinWU ZhiWANG Yong-jun
Soil microbes contribute to native plant species successful resistance against invasive plant.Three native tree species,Heteropanax fragrans (HF),Cinnamomum burmanii (CB),and Macaranga tanarius (MT) were effective in controlling the notorious invasive vine Mikania micrantha (MM).Biomass production and allocation patterns (shoot/root biomass ratio (shoot/root)) are important indicators of MM climbing coverage and competitive light-capturing capacity.An investigation was conducted to test the role of soil microbes associated with the three native tree species to inhibit MM biomass production and shift MM shoot/root.Rhizosphere soils originating from preculture HF,CB,MT,and MM plots were collected separately for use as inocula.The inocula were mixed with sterilized river sand at a 1:9 (w/w) ratio to grow MM.The fungicide carbendazim (methyl benzimidazol-2-ylcarbamate) was applied to half the treatments to kill pathogenic soil fungi.Two nutrient levels were established based on the natural soil nutrient concentration from a field stand invaded by MM.MM were grown from seeds in a glasshouse,harvested 15 weeks after sowing,and separated into shoot and root portions.Results showed that under interaction of soil origin and nutrient levels,MM biomass production was unchanged,but biomass allocation patterns were significantly different.MM biomass production grown in the three native tree soils under two nutrient levels was similar or higher than MM biomass production in MM conspecific soil,indicating the absence of species-specific pathogens that inhibited MM biomass production in native tree soils.However,in both conspecific and tree soils,MM biomass production was significantly reduced in the presence of pathogenic soil fungi,i.e.MM experienced significant fungal inhibition,demonstrating the pathogenic soil fungi promoted native tree resistence to MM.MM exhibited decreased shoot biomass allocation when cultivated in native tree soil relative to MM conspecific soil under field stand nutrient level conditions.Reduced resou
