Abstract
Peatlands are recognised as an important but vulnerable ecological resource. Understanding the effects of existing damage, in this case erosion, enables more informed land management decisions to be made. Over the growing seasons of 2013 and 2014 photosynthesis and ecosystem respiration were measured using closed chamber techniques within vegetated haggs and erosional peat pans in Dartmoor National Park, southwest England. Below-ground total and heterotrophic respiration were measured and autotrophic respiration estimated from the vegetated haggs. The mean water table was significantly higher in the peat pans than in the vegetated haggs; because of this, and the switching from submerged to dry peat, there were differences in vegetation composition, photosynthesis and ecosystem respiration. In the peat pans photosynthetic CO2 uptake and ecosystem respiration were greater than in the vegetated haggs and strongly dependent on the depth to water table (r2 > 0.78, p < 0.001). Whilst in the vegetated haggs, photosynthesis and ecosystem respiration had the strongest relationships with normalised difference vegetation index (NDVI) (r2 = 0.82, p < 0.001) and soil temperature at 15 cm depth (r2 = 0.77, p = 0.001). Autotrophic and total below-ground respiration in the vegetated haggs varied with soil temperature; heterotrophic respiration increased as water tables fell. An empirically derived net ecosystem model estimated that over the two growing seasons both the vegetated haggs (29 and 20 gC m−2; 95% confidence intervals of − 570 to 762 and − 873 to 1105 gC m−2) and the peat pans (7 and 8 gC m−2; 95% confidence intervals of − 147 to 465 and − 136 to 436 gC m−2) were most likely net CO2 sources. This study suggests that not only the visibly degraded bare peat pans but also the surrounding vegetated haggs are losing carbon to the atmosphere, particularly during warmer and drier conditions, highlighting a need for ecohydrological restoration.
Highlights
Keywords Photosynthesis Á Ecosystem respiration Á Heterotrophic respiration Á Peatland Á Carbon dioxide Á Blanket bog Peatlands are recognised as valuable ecological resources providing a range of ecosystem services including food provision, flood alleviation, drinking water supply, amenity value and carbon sequestration (Grand-Clement et al 2013)
Water tables were on average deeper and less variable in the vegetated haggs; mean of 9.1 ± 5.4 cm and varying from 28 cm below to 1 cm above ground level compared to a mean of 7.1 ± 10.1 cm and varying between 23 cm below to 21 cm above ground level in the peat pans (Fig. 3)
This study aimed to investigate the spatial and temporal controls on CO2 fluxes in a climatically marginal, eroding blanket bog and to quantify CO2 fluxes from these landscape components
Summary
Peatlands are recognised as valuable ecological resources providing a range of ecosystem services including food provision, flood alleviation, drinking water supply, amenity value and carbon sequestration (Grand-Clement et al 2013). Many peatlands are damaged, putting these ecosystem services at risk (Holden et al 2007). Blanket bogs form in cool (\ 15 °C mean summer temperatures) and wet ([ 1000 mm rain annually) conditions (Lindsay et al 1988). They consist of multiple peat-forming conditions (e.g. raised bogs, watershed mires, flushes etc.) which have spread laterally and joined together smothering the underlying topography. As they rise above the influence of groundwater they are dependent on precipitation for both water and nutrients (Moore 1987) resulting in acidic nutrient poor conditions. The UK has 10–15% of the world’s blanket peat resource (Tallis 1997) primarily located in upland areas, they are globally important
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