The mid-Holocene Ulmus fall at Diss Mere, South-East England — disease and human impact?

Abstract

There are five major hypotheses to explain the apparently synchronous, widespread, spectacular, specific, and sudden elm decline in north-west Europe — climatic change, soil change, competition, human impact, and pathogenic attack. The first four hypotheses predict slow declines (ca. 50–250 years), whereas the pathogen hypothesis predicts a rapid decline (ca. 10–20 years). Pollen analyses of annually laminated sediments from Diss Mere across the elm fall show that the Ulmus decline occurred within 7 years but that there was human impact in the surrounding forest for at least 160 years, including local cereal cultivation for at least 120 years, prior to the elm fall. At the time of the elm decline, there is no evidence for particularly warm or cold seasons or for any additional human interference. The magnitude and rate of the elm pollen decline are consistent with O. Rackham's hypothesis of a pathogenic attack taking place within woodland where the elm trees were already damaged as a result of human activity.