Relationships between spruce plantation age, solute and soil chemistry in Hafren forest P. A. Stevens, B. Reynolds, S. Hughes, D. A. Norris, and A. L. Dickinson* Institute of Terrestrial Ecology, Bangor Research Unit, University of Wales, Bangor, Deiniol Road, Bangor, Gwynedd, LL57 2UP *Institute of Terrestrial Ecology, Merlewood Research Station, Windermere Road, Grange-over-Sands, Cumbria LA11 6JU
Abstract. Rain, throughfall, soil waters from surface peaty O
horizon and deeper mineral B horizon, and stream water, were collected every four weeks for one year in a moorland
catchment, and in four forested catchments. The four forested catchments represented an age
sequence of first rotation Sitka spruce plantations, aged 14, 28, 37 and 53 years. All water samples
were analysed for all major solutes, including dissolved organic nitrogen (DON-N); stream
water and B horizon soil waters were also subjected to aluminium speciation. In each catchment,
soil samples were collected on one occasion and pH was measured.
Concentrations of most solutes were substantially
higher in the 37 year old forest stand than in the moorland catchment, with intermediate concentrations in the two
younger stands and 53 year old stand. In particular, higher nitrate-N concentrations were found
in the soils and streams of the older forests, although these concentrations tended to be highest
in the 37 year old stand.
Acid neutralizing capacity (ANC) of soil waters was lower in the B
horizon of the forest stands than in the moorland, and tended to decline with increasing forest
age. Soil water from both O and B horizons was most acid in the 37 year old stand, and the water
from the soil O horizon in all four forest stands was more acid than that in moorland sites. The
pH of the soil itself (as measured in a deionised water slurry) was lower in the forest stands
than in moorland, although trends with forest age were complex.
Citation: Stevens, P. A., Reynolds, B., Hughes, S., Norris, D. A., and Dickinson, A. L.: Relationships between spruce plantation age, solute and soil chemistry in Hafren forest, Hydrol. Earth Syst. Sci., 1, 627-637, doi:10.5194/hess-1-627-1997, 1997.