The effect of site fertility and climate on current weathering in Finnish forest soils: Results of a 10–16 year study using buried crushed test-rock material

Knowledge of the weathering rates in forest soils is needed when nutrient balances and the sustainability of silvicultural practices are estimated. The effects of site fertility and climate on weathering rates were studied in boreal coniferous forest soils in Finland by following transformations in crushed rock (Spectrolite, a dark, anorthosite feldspar dominated gabbro) confined in porous bags inserted into E-, B- and C-horizons along fertility and climate gradients, and left to weather for 10, 11 or 16 years. Organic carbon (OC) was accumulated in E-horizon incubated crushed test-rock material and it was more acidified and weathered than that deeper in the soil. There was a tendency for faster weathering of the C-horizon bags in the fertile sites than in the poor sites. Multivariate analyses indicated that more OC was accumulated in the bags in fertile sites than in poor sites, and that the crushed rock was more weathered in north than in south Finland although temperature sum and precipitation decreased northwards. The results suggest that humidity is an important climatic factor determining weathering rates and that fertile sites have greater potential to release base cations through weathering and sequester C to mineral surfaces than do poor sites.