The influence of vegetation composition on peat humification: implications for palaeoclimatic studies

Abstract

Peat humification analysis is a widely used palaeoclimate proxy. However, recent studies combining humification with other proxies of mire surface wetness have identified inconsistencies between the records. We illustrate this inconsistency by comparing humification records with plant macrofossil profiles in three ombrotrophic bogs. Peat humification is a measure for organic decay and reflects changing palaeohydrological conditions and former vegetation composition. The resulting signal is considered to be a derived response to climate. However, even minor changes in the botanical composition of the peat may have a significant influence on humification measurements. The implications of this for palaeoclimate studies are discussed. The assumption that climate has been the major influence on variations in humification rests on the botanical composition being relatively homogeneous throughout the peat profile, and is therefore questionable. Consideration should be given to developing species-specific measures of humification and to testing the assumption that the major influence on peat humification is the surface wetness of the bog (and therefore climate).

A multiproxy climate record from a raised bog in County Fermanagh, Northern Ireland: a critical examination of the link between bog surface wetness and solar variability

“…There have also been several criticisms of humification analysis because it can be influenced by the species composition of the peat (Aaby and Tauber, 1975;Blackford and Chambers, 1993;Yeloff and Mauquoy, 2006). On the other hand it could be argued that directional responses should remain reliable in humification records as the plant species characteristic of dry conditions, e.g.…”

A multiproxy record of late Holocene natural and anthropogenic environmental change from the Sphagnum peat bog Dürres Maar, Germany: implications for quantitative climate reconstructions based on pollen

“…Independently from the bog surface wetness, changes in species composition can alter the humification signal based on bulk peat material (Yeloff and Mauquoy, 2006). Most of the sequence Dü rres Maar is composed of Sphagnum rubellum (Moschen et al, 2009), and a potential species signal has only to be considered for one section.…”

Multiproxy late Holocene peat records from Ireland: towards a regional palaeoclimate curve

“…Dominance of a single macrofossil type with a wide water table tolerance, such as S. imbricatum (Stoneman et al, 1993), evidence of species-led humification changes (Coulson and Butterfield, 1978;Caseldine et al, 2000;Yeloff and Mauquoy, 2006), or low testate diversity due to decomposition with depth (Wilmshurst et al, 2003), are all examples of potential deficiencies in any one single-proxy indicator. To facilitate proxy comparison each proxy has been normalised and plotted on the same axis against age (Fig.…”