Influence of Management on the Biodiversity and Carbon Flux of Blanket Bog

PhD project by Alan Gray

Supervisors: John Grace, Colin Legg, Keith Smith, The University of Edinburgh School of GeoSciences; and Neil Cowie, RSPB Scotland

Proposal

OBJECTIVES: This study will establish functional relationships between blanket bog species composition, carbon flux and management. The study will estimate productivity and decay rates for a range of blanket bog species. A carbon accumulation potential (CAP) value will be determined for the major peat forming species that will be scaled up to the landscape level. The effects of grazing and burning on the spatial distribution and abundance of bog species will be assessed, identifying management options for the optimisation of carbon sequestration and biodiversity conservation.

BACKGROUND: Biodiversity conservation and management of carbon balance are of both global and local importance. Peatland ecosystems represent a vast carbon store and a unique biodiversity. They are estimated to store 3.0 - 4.6 x 1017 g C within 350 million ha (O'Neill 2000). Blanket bog is the most important peat-forming habitat in the UK. Scotland has over 1 million ha, 23% of the land area (source SNH, Lindsay 1995). With the uncertainties of ecosystem response to global climate change, the importance of conserving this carbon store cannot be overstated. Active blanket bogs have a high conservation value, designated as Natura 2000 sites (source JNCC). The conservation of active blanket bogs in the UK is primarily focused on protection of bog species diversity (source JNCC). Grazing and burning are important factors in Scotland's carbon flux because they are major determinants of bog species distributions, but their influence on the carbon dynamics is at present unclear. Spatial, temporal and between-species variability exists in the carbon dynamics of bogs, due to climate, phenology, and physiology (which cannot be controlled), but also due to water table depth, grazing, burning and the distribution and abundance of primary peat-forming species and communities (which are susceptible to management). The most important peat-forming vegetation includes Sphagnum spp and members of the Cyperaceae and Ericaceae. Variability exists in the contribution to peat formation between and within these groups. Species response to management can be predicted through their functional traits (e.g. Grime et al. 1988). Species have also been characterised using indicator values for light, moisture, pH, soil and fertility (e.g. Hill 2000, Bunce et al. 1999), but to date no carbon accumulation indicator value has been devised for bog species. The distribution of bog species can be a useful indicator of carbon flux e.g. bryophyte distribution can predict CH₄ flux (Bubier et al. 1994). However, the variability in rates of peat formation under different types of bog vegetation has yet to be quantified.

METHODS: Fieldwork at two Natura 2000 sites; Moor House in Upper Teesdale and Forsinard, part of the Caithness and Sutherland Peatlands. Moor House has existing grazing and burning experimental plots whilst Forsinard has many restoration projects allowing a wide range of study conditions. CAP will be determined for the major peat forming species experimentally and using static chambers. A pilot study will establish the time to equilibrate flux after disturbance by fieldworker. In years 1 and 2 day and night CO2 and CH4 fluxes will be quantified. In year 3 collection of gas samples will be radiocarbon dated to determine the age of the carbon emanating from the peatland. Functional traits will be identified using existing information where appropriate. Patterns of vegetation composition across a range of sites with different management conditions, will be mapped using GPS and GIS. The results will then be scaled-up to estimate the CAP of bog systems under different management conditions, based on the relative abundance and CAP of the dominant peat forming species and a spatial GIS model will be produced. As water table depth is an important controlling factor this will be measured and the relationship between water table, carbon flux and species composition will be examined.