A Paleoecological Perspective of Vegetation Succession on Raised Bog Microforms

Abstract

Peat cores were taken from eight primary and one secondary raised bog sites throughout the United Kingdom in order to determine the pathways of succession between the microform (hummock, ridge, lawn, hollow, and pool) plant communities of the mid to late Holocene. All of these sites have undergone drainage and/or cutting in the recent past, at least. The plant communities were reconstructed by using plant macrofossil analysis, and they are defined primarily by the dominant species of Sphagnum. While plant macrofossils may be used to infer hydrological conditions, an alternative proxy, using testate amoebae, was utilized. This group of organisms was used to avoid circular arguments when relating the vegetation changes to hydrological events. Consequently, a conceptual model of late Holocene succession on British raised mires is constructed that elucidates succession between the microform plant communities according to changes in the water table depth, its stability, quality, and physical disturbance of the vegetation cover. The general sequence of ombrogenous communities was elucidated to be, with increasing height above the water tables, S. cuspidatum and S. auriculatum Ͼ Sphagnum sect. Cymbifolia taxa Ͼ Sphagnum sect. Acutifolia taxa Ͼ a return of Sphagnum sect. Cymbifolia taxa Ͼ non-Sphagnum mosses.A major pathway toward degradation of the mire is apparent in modern times, and recovery is typically via a phase of dominance by S. tenellum prior to the establishment of either S. magellanicum or S. papillosum. Although this disturbance is of a large magnitude, it was found that equable or more severe perturbations to the water table had occurred in the past, especially at coastal sites where marine regression led to the establishment of Sphagnum-poor communities dominated by Calluna and Eriophorum vaginatum. The longterm persistence of hummock-hollow vegetation communities is demonstrated, but the appearance of persistent, more homogeneous phases suggests that this surface topography is not always well developed.

Testate amoebae analysis in ecological and paleoecological studies of wetlands: past, present and future

“…In these cases, modelling the relationship between testate amoebae and hydrology is only one part of the process. The reconstructions that can be obtained using this approach have been tested against other hydrological proxies such as plant macrofossils and peat humiWcation (Blundell and Barber 2005;Booth and Jackson 2003;Booth et al 2004;Charman et al 2001;Charman et al 1999;Lavoie and Richard 2000;Mauquoy and Barber 2002;McGlone and Wilmshurst 1999;McMullen et al 2004;Mitchell et al 2001;Wilmshurst et al 2002). Blundell and Barber (2005) concluded that testate amoebae provided more consistently reliable reconstructions that the other techniques, but that a multi-proxy approach is nevertheless preferable.…”

“…However, there is a growing recognition that testate amoebae can also be used in shorter-term biomonitoring. For example, testate amoebae are starting to be used in the monitoring of peatland regeneration (Davis and Wilkinson 2004;Jauhiainen 2002;Laggoun-Défarge et al 2004), and peatland management (McMullen et al 2004;Vickery and Charman 2004) (Fig. 6).…”

Comparative ecology of vascular plant, bryophyte and testate amoeba communities in four Sphagnum peatlands along an altitudinal gradient in Switzerland

“…This has led to their use in the study of primary (e.g. palaeoecological records, Chambers et al, 2012;Charman, 2001;McMullen et al, 2004) and secondary succession (Talbot et al, 2010). Testate amoebae are increasingly considered as a useful tool for peatland bio-monitoring and management (Davis and Wilkinson, 2004;Mitchell et al, 2008;Turner and Swindles, 2012).…”

Testate amoebae as proxies for mean annual water‐table depth in Sphagnum‐dominated peatlands of North America

“…These transfer functions have been used to address a wide range of environmental and palaeoenvironmental issues. For example, they have played an important role in understanding temporal relationships between vegetation and hydrology within raised bogs (McMullen et al, 2004), delimiting spatial and temporal patterns of past centennial and sub-centennial scale drought events (Booth et al, 2006), monitoring and informing bog restoration efforts (Buttler et al, 1996;Davis and Wilkinson, 2004), and assessing the responses of terrestrial vegetation to past climate variability and change (Wilmhurst et al, 2002;Booth and Jackson, 2003;Booth et al, 2004).…”