Epsilon Open Archive

Abstract

The perennial weed species Rumex crispus L., or curled dock, is a major problem in agriculture in Sweden as well as in many other parts of the world. Its ability to establish quickly from seed, its persistent taproot system, high capacity of regrowth after cutting, and massive production of seed that remain viable in the seed bank for decades all contribute to the success of the weed. It is particularly problematic on dairy farms and in organic agriculture and difficult to control effectively, especially without the use of chemical herbicides. R. crispus and other weedy dock species have been well studied since the early 1900's. However, the constant changes in agricultural practices and policies, affecting both the abundance and performance of the weed and the conditions for its control, call for a continuous renewal of the knowledge of the species. This thesis work was based upon a set of experimental studies dealing with several different processes in the life cycle of R. crispus. I have investigated time and pattern of seedling emergence, the effects of competition on the performance of juvenile plants, vegetative regeneration from underground parts, and population dynamics in an agricultural field. I found that R. crispus seedlings can emerge throughout the growing season and that seeds that remain on the parent plant over winter posses a certain level of dormancy, leading to later and more intermittent emergence compared to seeds dispersed in autumn. Tillage that leads to fragmentation of the root system can stimulate sprouting of new shoots from the regenerative tissue of the taproot. Severed top fragments of roots sprouted faster and produced more shoot biomass than intact rootstocks. Further, it was found that R. crispus seedlings are very sensitive to root competition in its early life stages, while it makes some morphological adaptations in response to shoot competition. To establish successfully in grassland, a large gap in the sward is required. Vegetation density during establishment of R. crispus plants will affect their performance also in the long term. Low frequency cuttings had no effect on population size, but can reduce the rate of seed bank accumulation.