Effects of atmospheric deposition on Scottish upland moorland podzols
Soil samples were collected from the major horizons of Scottish upland Calluna moorland podzols derived from quartzite, Devonian and Torridonian sandstone, or granite or granitic tills. All soil was subjected to routine chemical analysis and the soil derived from granite was also mineralogically analysed. The results were studied in relation to finding evidence for potential acidification effects of atmospheric deposition. Strong relationships were observed between acid deposition parameters, particularly the mobile anion concentrations, and soil pH measured in water and soil extractable Al in all the horizons from podzols derived from sandstones and quartzites. These are discussed in Chapter 2. When looking for ameliorative effects, less clear trends were observed between atmospheric base cation inputs and soil "damage" parameters, possibly due to the distribution of the data. Soils derived from granite or granitic till showed relationships between soil pH in water or in CaCl2 pastes and H+ deposition, and between soil extractable Al and H+ deposition (Chapter 3). In addition, atmospheric inputs of base cations showed strong acid ameliorative properties in these soils. The relative importance of marine- and non-marine base cations in the calculation of critical loads for soil is examined in Chapter 4. The accumulation of N in the surface horizons along a pollution gradient is discussed in Chapter 5. At low to moderate total and NH4+ deposition (i.e., 10 and 5 kg ha-1 yr-1 respectively), soil total N and soil C:N ratio increased linearly with atmospheric N deposition. In spite of the N accumulation, C accumulated relatively faster than N, to increase the C:N ratio at sites with low to moderate N deposition. At total N or NH4+ deposition values above 8.8 and 4.0 kg ha-1 yr-1 respectively, the C:N ratio declined with increasing N deposition.