Ecological Effects Of Arbuscular Mycorrhizal Fungi(AMF) On Common Compositae Invasive Species In Guangzhou

In order to better understand the traits of Compositae invasive species in Guangzhou, the effects of arbuscular mycorrhizal fungi(AMF) on Compositae invasive species were studied. In the field investigation, the AMF colonization rate and spore density of 7 Compositae invasive plant species in 4 habitats, i.e. farmland and orchard, forest surround, artificial green land and coastal area, were studied, and the effects of soil factors, habitats and hosts on AMF were also analyzed. Two pot experiments were conducted to study the effects of AMF on the growth and reproduction of two Bidens species(B. alba L. and B. pilosa Linn. var. radiata) from different origin, and the role AMF play in the competition of the two Bidens species. The main results are as follows:(1) All the 7 invasive species(Bidens pilosa L., Mikania micrantha H.B.K., Wedelia trilobata L., Aster subulatus Michx., Erigeron annuus(L.) Pers., Eupatorium catarium Veldkamp, and Gynura crepidioides Benth.) were colonized by AMF, indicating that the symbiosis between AMF and Compositae species were common. AMF colonization rate was significantly affected by hosts, while AMF spore density was significantly affected by both hosts and habitats. Correlation analysis showed that soil parameters affecting AMF colonization rate and spore density varies among habitats. AMF colonization and spore density were related to soil organic matter, total N, available N and available P.(2) The growth of the two Bidens species from outside Guangzhou origin were not significantly affected comparing to species from Guangzhou origin, but their reproduction ability was significantly influenced, leading to a delay in flowering time and reduction in seed yield. After inoculated with AMF, both B. pilosa and B. alba gained higher plant height and biomass, indicating that AMF have positive effects on the growth and reproducity of both species. The Bidens species improved the availability of soil nitrogen to meet their fast growing demand for nitrogen, meanwhile, soil organic matter content was reduced, while other soil parameters were not affected.(3) Both B. alba and B. pilosa do not rely on AMF, but AMF inoculation could generate positive effects on their growth and reproduction, which is helpful to the invasion of these two species. More nitrogen was allocated to the root of B. alba after inoculated with AMF, which may benefit B. alba in the competition with B. pilosa. Inoculation with AMF may lead to a certain reduction in soil pH and increase in soil nutrient conditions. AMF also showed positive effects on plant root. The increase of growth and reproduction of both Bidens species under sterilization treatment indicated that soil microorganisms might be of great importance for them.