Biology and control of the invasive Fallopia taxa

M-PV

2016-12-31

anglais. AbstractFallopia japonica and Fallopia sachalinensis are perennial, rhizomatous plants, native toEast Asia, and introduced to Europe in the mid 1800’s. Hybridization between the taxa in theintroduced range has given rise to the hybrid F. x bohemica. The taxa reproduce mainlyvegetatively in Europe, but sexual reproduction occurs. Disturbance and spread of rhizomeand stem fragments by human activities and waterstreams are considered the most importantmeans of spread. The taxa are among the most problematic introduced weeds in Europe andNorth America, especially in ruderal and riparian habitats. The taxa can greatly reduce nativebiodiversity and damage roads and constructions. The rhizomes have a high tolerance to bothmechanical and chemical control methods, which makes eradication time-demanding andcostly. The need for improved control strategies is critical. This thesis aims to increaseknowledge about the biology of the taxa, and contribute to more effective control methods.Part I of the thesis is a literature study of the biology and control of the invasive Fallopiataxa. Part II consists of four experiments: 1) The distribution of the taxa was assessed in fiveareas in Norway. Morphological and molecular methods (simple sequence repeats analysis,SSR) were used for taxonomic identification. Ploidy levels were determined by flowcytometry. Sequencing (DNA barcoding) of the matK region and the ITS region was assessedas a tool for identification of the taxa. Results: F. japonica was the most frequent taxon, butF. x bohemica was more frequent than previously recorded in the study area. F. sachalinensiswas rare. The taxa could be distinguished by morphological means, and the SSR analysissupported the morphological identification. Sequencing of the matK and ITS region could notbe used to distinguish F. japonica and F. x bohemica, but the ITS region appears to be usefulfor distinguishing F. sachalinensis from the other taxa. Ploidy levels were octoploid F.japonica, tetraploid F. sachalinensis and hexaploid F. x bohemica. 2) The biomass allocationpattern in F. japonica and F. x bohemica was examined through harvests of above- andbelowground biomass of experimental plants at different times of the growing season.Results: A shift in the allocation was found in June, when allocation to aboveground partsdecreased and allocation to belowground parts increased. F. x bohemica had a greateraboveground and belowground biomass than F. japonica. 3.1) Seasonal changes in the shootregrowth potential of F. x bohemica was examined through single cuttings throughout thegrowing season. Results: A seasonal decline in sprouting was found from June untilSeptember, when little to no regrowth occurred. 3.2) The effect of covering on the shootregrowth potential was examined through covering stands with thick plastic for differenttime-lengths. Results: Three years of covering resulted in no new shoot growth.

anglais. The Norwegian Public Roads Administration