Carbon stock changes in a peaty gley soil profile after afforestation with Sitka spruce (Picea sitchensis)

Abstract

We investigated the changes of carbon (Corg) stocks in the litter (OL), organic (OH) and mineral (A) layer after afforestation and at different stages after clearfelling of the first rotation, in a forest chronosequence of Sitka spruce (Picea sitchensis) on peaty gley soil, in Harwood Forest (N.E. England). The sites chosen were: unplanted natural grassland, 40-yr-old first rotation, 18 months-old clearfelled, and 12, 20 and a 30 yr-old second rotation. A further comparison was carried out in three 40-yr-old stands between unplanted stripes of land (rides) and adjacent forest. Measurements of soil Corg were conducted with two methods, i.e., weight loss on ignition (L.O.I.) and dry combustion by C/N analysis. The results from two methods were linearly related. Afforestation changed both the total amounts and the distribution of the Corg stocks from the unplanted natural grassland. The total stocks of Corg decreased during first rotation and increased during second rotation to values similar to those found in the unplanted grassland. The vertical distribution of Corg also changed, with proportionally more carbon stored in the OL and inside the A layer and less in the organic layer after afforestation and two rotations. © INRA, EDP Sciences, 2005.