Forest soil carbon is threatened by intensive biomass harvesting

Abstract

Forests play a key role in the carbon cycle as they store huge quantities of organic carbon, most of which is stored in soils, with a smaller part being held in vegetation. While the carbon storage capacity of forests is influenced by forestry, the long-term impacts of forest managers’ decisions on soil organic carbon (SOC) remain unclear. Using a meta-analysis approach, we showed that conventional biomass harvests preserved the SOC of forests, unlike intensive harvests where logging residues were harvested to produce fuelwood. Conventional harvests caused a decrease in carbon storage in the forest floor, but when the whole soil profile was taken into account, we found that this loss in the forest floor was compensated by an accumulation of SOC in deeper soil layers. Conversely, we found that intensive harvests led to SOC losses in all layers of forest soils. We assessed the potential impact of intensive harvests on the carbon budget, focusing on managed European forests. Estimated carbon losses from forest soils suggested that intensive biomass harvests could constitute an important source of carbon transfer from forests to the atmosphere (142–497 Tg-C), partly neutralizing the role of a carbon sink played by forest soils.

Soil labile organic carbon and carbon-cycle enzyme activities under different thinning intensities in Chinese fir plantations

“…Thinning reduced the SOC concentrations except for in October, which was partially consistent with our hypothesis, and the thinning effect was more pronounced in the upper soil layer than in the lower. An average SOC loss of 32.5% SOC in thinned sites was also found by Boerner et al (2006), whereas Achat et al (2015) found an SOC decrease of approximately 7% by tree removal in a meta-analysis. The decrease in SOC following the partial removal of canopy trees has been attributed to the reduction in the supply of substrate that enters the soil (Piene and Cleve, 1978;Jandl et al, 2007).…”

“…A major focus in forest management is to promote the increase of this sink (Jandl et al, 2007;Achat et al, 2015;Moreno-Fernandez et al, 2015). Soil organic carbon (SOC) can be divided into labile and recalcitrant fractions based on the mean residence times in the soil.…”

Forest management and carbon sequestration in the Mediterranean region: A review

“…Johnson & Curtis (2001) reported that whole-tree harvesting resulted in slight decreases in soil organic carbon stock (-6%) while sawlog harvesting increases (18%) the soil carbon stock in the A horizon. Achat et al (2015) stated that conventional harvesting of tree stems (sawlog) reduced the forest floor carbon stock by 22% in comparison to unharvested stands, but no effects were found in the mineral soil organic carbon stock. When intensive harvesting was considered (whole-tree harvesting), the forest floor carbon stock was reduced by 37% and mineral soil carbon stock was mainly affected in the deeper layers (-7%).…”

The Carbon Sequestration Potential of Degraded Agricultural Land in the Amhara Region of Ethiopia

“…The highest proportion of terrestrial carbon is stored in forest ecosystems [1]. Thus forests are important to balance global carbon dioxide (CO 2 ) [2][3][4]. Human activities are important considerations because land use change and forest management directly affect the forest conditions and thus the carbon cycle.…”