Size and spatial structure of the soil and lacustrine charcoal pool across a boreal forest watershed

Abstract

Forest fires convert a proportion of the burning vegetation into charcoal that is stored in forest soils and lake sediments. In this paper we use a geostatistical approach to present a detailed analysis of the size of the charcoal pool and its spatial variation in a boreal forest watershed including its lake sediment. The amount of soil charcoal averaged 179g/m2 and ranged from 0 to 3600g/m2 in the watershed. There was an extreme variation in the size of the charcoal pool over fine (cm) spatial scales. For example, the amount of charcoal in the soil could range from 34 to 1646g/m2 within a distance of 10cm. Individually dated soil charcoal particles had radiocarbon ages that varied from 630 to 2930calyr BP. The lake sediment began accumulating at 10,600calyr BP and charcoal accumulation has been practically continuous ever since then, with the largest peak occurring at 6900calyr BP. The lake sediment contained more charcoal, 360g/m2, than the average for forest soil. We interpret this as an indication of a relatively rapid degradation of charcoal in boreal forest soils.