Search

Recognition of peatlands as a key natural store of terrestrial carbon has led to new initiatives to protect and restore them. Some afforested bogs are being clear-felled and restored (forest-to-bog restoration) to recover pre-afforestation ecosystem function. However, little is known about differences in the peat properties between intact, afforested and restored bogs. A stratified random sampling procedure was used to take 122 peat cores from three separate microforms associated with intact (hollows; hummocks; lawns), afforested and restored bogs (furrows; original surface; ridges) at two raised and two blanket bog locations in Scotland. Common physical and chemical peat properties at eight depths were measured in the laboratory. Differences in bulk density, moisture and carbon content between the afforested (mean = 0.103 g cm−3, 87.8% and 50.9%, respectively), intact (mean = 0.091 g cm−3, 90.3% and 51.3%, respectively) and restored bogs (mean = 0.095 g cm−3, 89.7% and 51.1%, respectively) were small despite their statistical significance. The pH was significantly lower in the afforested (mean = 4.26) and restored bogs (mean = 4.29) than the intact bogs (mean = 4.39), whereas electrical conductivity was significantly higher (mean: afforested = 34.2, restored = 38.0, intact = 25.3 μS cm−1). While significant differences were found between treatments, effect sizes were mainly small, and greater differences in pH, electrical conductivity, specific yield and hydraulic conductivity existed between the different intact bogs. Therefore, interactions between geographic location and land management need to be considered when interpreting the impacts of land-use change on peatland properties and functioning.

The carbon sequestration potential of peatlands has led to increasing interest in the restoration of bogs previously subjected to plantation forestry. However, little information exists about the effects on hydrological processes of what has become known as forest-to-bog restoration. The hydrological functioning of three afforested, two intact and four forest-to-bog restoration sites was compared at a raised bog and blanket bog location. For the raised bog location, the annual runoff/rainfall coefficient was 59.7% for the intact site, 41.0% for the afforested site and 53.1% for the oldest restoration site (9 years post-felling). At the blanket bog location, the coefficient was 80.6% for the intact site, 63.0% for the afforested site and 71.6% for the oldest restoration site (17 years post-felling). Compared with intact bog, median peak storm discharge was significantly greater in the restoration sites for the raised bog location but not for the blanket bog location. Water-table peak lag times were greatest, and water-table depths deepest in the afforested sites and the most recent raised bog restoration site and least in the oldest blanket bog restoration site. The estimated contribution of overland flow in the afforested sites was 2.9% for the raised bog and 11.9% for the blanket bog, increasing to 8.7% and 32.2% at the oldest restoration sites for the raised bog and blanket bog, respectively. Overall, hydrological functioning of the raised bog and blanket bog restoration sites was different from the intact sites but was most similar to intact bog in the oldest restoration sites.

How rainfall infiltration rate and soil hydrological characteristics develop over time under forests of different ages in temperate regions is poorly understood. In this study, infiltration rate and soil hydrological characteristics were investigated under forests of different ages and under grassland. Soil hydraulic characteristics were measured at different scales under a 250-year-old grazed grassland (GL), 6-year-old (6yr) and 48-year-old (48yr) Scots pine (Pinus sylvestris) plantations, remnant 300-year-old individual Scots pine (OT) and a 4000-year-old Caledonian Forest (AF). In situ field-saturated hydraulic conductivity (Kfs) was measured, and visible root:soil area was estimated from soil pits. Macroporosity, pore structure and macropore connectivity were estimated from X-ray tomography of soil cores, and from water-release characteristics. At all scales, the median values for Kfs, root fraction, macroporosity and connectivity values tended to AF > OT > 48yr > GL > 6yr, indicating that infiltration rates and water storage increased with forest age. The remnant Caledonian Forest had a huge range of Kfs (12 to >4922 mm h−1), with maximum Kfs values 7 to 15 times larger than those of 48-year-old Scots pine plantation, suggesting that undisturbed old forests, with high rainfall and minimal evapotranspiration in winter, may act as important areas for water storage and sinks for storm rainfall to infiltrate and transport to deeper soil layers via preferential flow. The importance of the development of soil hydrological characteristics under different aged forests is discussed.