Biology and control of the invasive Fallopia taxa

Abstract

Abstract Fallopia japonica and Fallopia sachalinensis are perennial, rhizomatous plants, native to East Asia, and introduced to Europe in the mid 1800’s. Hybridization between the taxa in the introduced range has given rise to the hybrid F. x bohemica. The taxa reproduce mainly vegetatively in Europe, but sexual reproduction occurs. Disturbance and spread of rhizome and stem fragments by human activities and waterstreams are considered the most important means of spread. The taxa are among the most problematic introduced weeds in Europe and North America, especially in ruderal and riparian habitats. The taxa can greatly reduce native biodiversity and damage roads and constructions. The rhizomes have a high tolerance to both mechanical and chemical control methods, which makes eradication time-demanding and costly. The need for improved control strategies is critical. This thesis aims to increase knowledge 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 Fallopia taxa. Part II consists of four experiments: 1) The distribution of the taxa was assessed in five areas in Norway. Morphological and molecular methods (simple sequence repeats analysis, SSR) were used for taxonomic identification. Ploidy levels were determined by flow cytometry. Sequencing (DNA barcoding) of the matK region and the ITS region was assessed as a tool for identification of the taxa. Results: F. japonica was the most frequent taxon, but F. x bohemica was more frequent than previously recorded in the study area. F. sachalinensis was rare. The taxa could be distinguished by morphological means, and the SSR analysis supported the morphological identification. Sequencing of the matK and ITS region could not be used to distinguish F. japonica and F. x bohemica, but the ITS region appears to be useful for distinguishing F. sachalinensis from the other taxa. Ploidy levels were octoploid F. japonica, tetraploid F. sachalinensis and hexaploid F. x bohemica. 2) The biomass allocation pattern in F. japonica and F. x bohemica was examined through harvests of above- and belowground 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 parts decreased and allocation to belowground parts increased. F. x bohemica had a greater aboveground and belowground biomass than F. japonica. 3.1) Seasonal changes in the shoot regrowth potential of F. x bohemica was examined through single cuttings throughout the growing season. Results: A seasonal decline in sprouting was found from June until September, when little to no regrowth occurred. 3.2) The effect of covering on the shoot regrowth potential was examined through covering stands with thick plastic for different time-lengths. Results: Three years of covering resulted in no new shoot growth.