Biogeochemical impacts of clearfelling and reforestation on blanket peatland streams I. phosphorus
2003; Elsevier BV; Volume: 180; Issue: 1-3 Linguagem: Inglês
10.1016/s0378-1127(02)00648-5
ISSN1872-7042
AutoresThomas Cummins, Edward P. Farrell,
Tópico(s)Aquatic Invertebrate Ecology and Behavior
ResumoForest drains and streams on blanket peatland in western Ireland were sampled weekly, 1996–2000, using continuous, depth-proportional passive sampling, and analysed for molybdate-reactive phosphorus (MRP) by the acid–antimony-molybdate method. The study area was largely clearfelled and partly reforested with wind-rowing, drainage, planting, and aerially applied rock phosphate equivalent to 70 kg P/ha. Further felled areas were not wind-rowed, drained or fertilised for reforestation. Catchment areas were of the following orders: 1 ha (two forest drains); 10–20 ha (two semi-permanent drains, one permanent stream); 1–3 km2 (three permanent streams). Streamwater from three undisturbed closed-canopy-forest catchments had pre-felling median concentrations of MRP (all values are μg MRP l−1) of 9 (catchment approximately 1 km2), 13 (1 ha) and 93 (1 ha). Clearfelling was associated with large increases (maxima 305, 4164 and 3530 μg MRP l−1) in MRP concentrations in each case. Following protracted mechanical operations in four other catchments of ca. 1 km2, 20, 10 and 10 ha, with apparently existing elevated MRP concentrations (medians 41, 328, 102, 214 μg MRP l−1) fertilising gave major rises (maxima 218, 2723, 806, 2323 μg MRP l−1). The three smaller catchments showed subsequent exponential-type declines, while the 1 km2 catchment had sustained high values (median 74 μg MRP l−1) over the remaining study period. The higher values in this one larger stream were seasonally cyclical, with a late summer maximum. Annual median MRP values above 70 μg l−1 represent a seriously polluted state for these streams, which qualify as waterways under relevant statutes, but it is not clear what implications these results have for downstream river-water quality in larger channels.
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