Surface peat and its dynamics following drainage - do they facilitate estimation of carbon losses with the C/ash method?

Abstract

Peatlands are under pressure, and information about the impacts of land use and climate change on their carbon (C) balance is needed. Quick and inexpensive methods that rely on changes in the ash and C contents of surface peat have been suggested, on the basis of consistent changes observed from repeated measurements in peatlands under agricultural use. More general applicability has been claimed for such methods; however, their application requires a thorough understanding of the processes that shape the ash and C contents following drainage. In this article, we review the characteristics and dynamics of the surface peat following drainage in cases where the sites remain vegetated and follow the secondary succession induced by drainage. We conclude that methods which merely examine the ash and C contents of surface peat samples will generally not lead to reliable information about the C balances of the sites but, rather, to arbitrary values incorporating unknown proportions of several non-random errors. The main challenges are to find truly appropriate reference samples, and to ensure that the samples from the site of interest have not been modified by processes other than decomposition. These challenges arise from several physical, chemical and biological processes that shape the surface peat following drainage, in addition to the decomposition process. Even though the theoretical basis of C/ash methods may be sound, it is virtually impossible to find vegetated sites where decomposition-induced changes in the C/ash quotient would not be masked by the outcomes of the other processes. Thus, in most cases, the C/ash method involves not only estimable random errors but also serious non-random errors that cannot be taken into account.

Keywords

• C/ash method
• carbon balance
• drainage
• surface peat