B. Reynolds et al., Cycling of nutrient base cations in a twelve year old Sitka spruce plantation in upland mid-Wales, HYDROL E S, 4(2), 2000, pp. 311-321
The effects of the early growth of plantation forestry on the biogeochemica
l cycling of potassium, calcium and magnesium have been investigated in a s
tand of 12 year old Sitka spruce and adjacent moorland growing on acid peat
y podzol soils in mid Wales. Element budgets have been calculated for both
systems using measurements of soil and vegetation base cation pools and flu
xes. In the moorland, the magnesium budget is approximately at steady-state
with no net change to the soil store whilst the soil is accumulating potas
sium. The calcium budget is approximately balanced but contains significant
uncertainties due to between plot variability in calcium leaching losses.
Afforestation has greatly increased the above-ground living biomass which h
olds 7 to 15 times more nutrients compared to the living aerial biomass in
the moorland. With the exception of magnesium, the base cation stores withi
n the forest soil are being depleted as the increase in atmospheric deposit
ion due to the forest canopy provides only a small offset to the much large
r accumulation of base cations within the trees. The current net rate of ch
ange in the soil store of calcium is sustainable for only 65 years. However
, as the trees mature, their demand for calcium will be reduced and they sh
ould be able to 'tap' deeper sources of calcium in the soil profile as well
as in the drift and regolith material.