Unusual mid-Holocene abundance of Ulmus in western Ireland-human impact in the absence of a pathogen?

Abstract

A Holocene pollen record from Co. Clare, western Ireland, shows unusually high Ulmus pollen frequencies until about 2500 cal. BP, interrupted by four brief episodes of reduced Ulmus pollen between 6000 and 3000 cal. BR Localized anthropogenic disturbance of the vegetation during this interval is inferred from higher magnetic susceptibility of the sediments, indicating soil erosion, and from increased Poaceae and Plantago pollen. The continued abundance of elm at several sites in Ireland, despite human impact, suggests that disease was a less significant factor in the reduction of Irish elm populations than elsewhere in northwestern Europe. It may be that the pathogen, its dispersal agent, or susceptible elm ecotypes were locally absent near the western range margin of elm, reinforcing the argument that the combined effects of human exploitation and a pathogen were necessary to cause the permanent elm decline at 6000 cal. BP in most of northwestern Europe.

Fresh insights into long‐term changes in flora, vegetation, land use and soil erosion in the karstic environment of the Burren, western Ireland

“…Sediments from Molly’s Lough, however, show elevated magnetic susceptibility values that have been interpreted as indicative of sustained erosion during the Neolithic and Bronze Age ( c. 6000–3000 cal. BP; Lamb & Thompson 2005). The lake, however, may not be typical for the Burren, lying, as it does, near the karst–shale geological divide.…”

Dating Ancient Field Walls in Karst Landscapes Using Differential Bedrock Lowering

“…The subsequent Chalcolithic and Early Bronze Age (c. 2500-1500 B.C.) stands out as a period that seems to have been particularly populous on the Burren (Jones, McVeigh, &Ó Maoldúin, 2015), while in later prehistory population and farming levels may have dropped off before rising again sometime after 400 A.D. and continuing into recent centuries at levels high enough for farming to have had a significant impact on the landscape (Watts, 1984;O'Connell & Jelicic, 1994;Jones, 2004;Lamb & Thompson, 2005;Feeser & O'Connell, 2009;Jones, Carey, & Hennigar, 2011). This ebb and flow of nearly six millennia of farmers across the Burren has left a considerable number of burial monuments and habitation sites and a myriad of ancient stone walls.…”

Drought, disease, defoliation and death: forest pathogens as agents of past vegetation change

“…However, over the last 30 years a broad consensus has emerged that such a widespread and complex event cannot be explained by a single process and that a pathogen is likely to have been a contributory factor (e.g. Birks, ; Girling, ; Peglar, ; Peglar and Birks, ; Parker et al ., ; Rackham, ; Clark and Edwards, ; Lamb and Thompson, ). A number of lines of evidence (Table ) have been cited in support of an attack by a fungal disease (such as Ophiostoma ) spread by the elm bark beetle ( Scolytus scolytus L.).…”

“…A number of lines of evidence (Table ) have been cited in support of an attack by a fungal disease (such as Ophiostoma ) spread by the elm bark beetle ( Scolytus scolytus L.). It is argued that the elm decline may be the first example of anthropogenic disturbance facilitating the spread of a pathogen (Lamb and Thompson, ). Evidence for such activity is often, but not always, associated with the major reduction in Ulmus pollen values and early agriculturists could have been involved directly (by transporting a fungus) or indirectly (e.g.…”

“…The continued abundance of elm at a site in western Ireland through into the late-Holocene, despite evidence of localized disturbance due to human activity in the mid-Holocene. Lamb and Thompson (2005) suggest that the pathogen, vector or the tree was less susceptible near to the margins of the range of elm.…”