Effects of sulphur pollution on rates of litter decomposition in a pine forest

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Abstract
Litter decomposition was measured at three "ecologically analogous" pine (Pinus contorta × Pinus banksiana) stands located 2.8 (site 1), 6.0 (site 2), and 9.6 km (site 3) from a sour gas plant in west-central Alberta which has been emitting sulphur dioxide since 1959 and elemental sulphur dust since 1979. Respiration of intact forest floor cores and separated forest floor layers was consistently lowest at site 1 and highest at site 3. Rates of mass loss and respiration of pine needles decomposing in litterbags for 17 months also increased with distance from the gas plant. Decomposition of needles in exchanged litterbags was related primarily to the site of origin during the first few months of decomposition and to the site of placement thereafter. Litter fall rates did not bear any relation to sulphur loading; however, litter accumulation and residence times were greatest at the site nearest the gas plant. These findings indicate that an inhibition of decomposition has occurred in response to elevated levels of sulphur pollution near the gas plant.