Dynamics of Chamerion angustifolium in grassland vegetation over a thirty-nine-year period

The dynamics of the tall perennial Chamerion angustifolium, as a component of neutral grassland vegetation of a roadside verge near Bibury, Gloucester shire, UK, is described for a 39-year period. Observations were made in Jul y annually of its performance (height and above-ground biomass) and of its major co-dominant, the grass Arrhenatherum elatius. The expansion of a sing le colony of C. angustifolium by clonal growth from a small cluster of shoo ts to a substantial highly vigorous stand and its subsequent rapid decline, which was followed by some recovery, are considered especially with respec t to weather data. Shoot biomass and flowering were found to be promoted by warm summers and mild winters. The switch of dominance between C. angustif olium and A. elatius is discussed and possible reasons for the decrease of the former are suggested.