Carbon budget recovery and role of coarse woody debris in post-logging forest ecosystems of Southern Siberia

Abstract

Forest harvesting is a major human-caused disturbance affecting carbon budgets in forest ecosystems. This study was concerned with post-logging carbon pool changes in Scots pine (Pinus sylvestris) and Siberian fir (Abies sibirica) stands. To understand carbon budget recovery trends following logging, carbon stock and fluxes were measured in stands differing in time since logging. In both Scots pine and fir stands disturbed by logging, the tree phytomass contribution to the carbon budget decreased drastically, whereas the coarse woody debris (CWD) carbon pool exhibited a marked increase. Sixty years following logging, the Scots pine stand carbon storage was almost 70 % of that prior to logging and the ratio between the phytomass and soil organic matter was the same as before the disturbance. While the phytomass carbon showed a similar trend in the fir stand of the same age, it was less than on the control stand. In a 50-55-year-old fir stand, 26 years since harvesting, the phytomass carbon recovered only by 15 %. Siberian fir and Scots pine logging sites differed in CWD loading and decomposition rate. The phytomass dynamics and CWD loading values obtained suggest that Scots pine stands which have experienced logging are most likely carbon sinks, as was clear from the phytomass production exceeding organic matter decomposition-caused fluxes. Conversely, logged fir ecosystems are likely to be sources of carbon to the atmosphere due to a large CWD loading, faster rate of its decomposition, and slow phytomass increment.