Influence of forest management activities on soil organic carbon stocks: A knowledge synthesis

Almost half of the total organic carbon (C) in terrestrial ecosystems is stored in forest soils. By altering rates of input or release of C from soils, forest management activities can influence soil C stocks in forests. In this review, we synthesize current evidence regarding the influences of 13 common forest management practices on forest soil C stocks. Afforestation of former croplands generally increases soil C stocks, whereas on former grasslands and peatlands, soil C stocks are unchanged or even reduced following afforestation. The conversion of primary forests to secondary forests generally reduces soil C stocks, particularly if the land is converted to an agricultural land-use prior to reforestation. Harvesting, particularly clear-cut harvesting, generally results in a reduction in soil C stocks, particularly in the forest floor and upper mineral soil. Removal of residues by harvesting whole-trees and stumps negatively affects soil C stocks. Soil disturbance from site preparation decreases soil C stocks, particularly in the organic top soil, however improved growth of tree seedlings may outweigh soil C losses over a rotation. Nitrogen (N) addition has an overall positive effect on soil C stocks across a wide range of forest ecosystems. Likewise, higher stocks and faster accumulation of soil C occur under tree species with N-fixing associates. Stocks and accumulation rates of soil C also differ under different tree species, with coniferous species accumulating more C in the forest floor and broadleaved species tending to store more C in the mineral soil. There is some evidence that increased tree species diversity could positively affect soil C stocks in temperate and subtropical forests, but tree species identity, particularly N-fixing species, seems to have a stronger impact on soil C stocks than tree species diversity. Management of stand density and thinning have small effects on forest soil C stocks. In forests with high populations of ungulate herbivores, reduction in herbivory levels can increase soil C stocks. Removal of plant biomass for fodder and fuel is related to a reduction in the soil C stocks. Fire management practices such as prescribed burning reduce soil C stocks, but less so than wildfires which are more intense. For each practice, we identify existing gaps in knowledge and suggest research to address the gaps. https://doi.org/10.1016/j.foreco. 2020.118127 Received 6 January 2020; Received in revised form 26 March 2020; Accepted 31 March 2020 ⁎ Corresponding author. E-mail addresses: mathias_mayer@gmx.at, mathias.mayer@boku.ac. at (M. Mayer), Cindy.Prescott@ubc.ca (C.E. Prescott), laurent.augusto@inra.fr (L. Augusto), lauric.cecillon@inrae.fr (L. Cécillon), gferreira@uga.edu (G.W.D. Ferreira), jamesj@exponent.com (J. James), robert.jandl@bfw.gv. at (R. Jandl), klaus.katzensteiner@boku.ac. at (K. Katzensteiner), jean-paul.laclau@cirad.fr (J.-P. Laclau), jerome.laganiere@canada.ca (J. Laganière), yann.nouvellon@cirad.fr (Y. Nouvellon), david.pare@canada.ca (D. Paré), johnalvin.stanturf@emu.ee (J.A. Stanturf), elena.vanguelova@forestresearch.gov. uk (E.I. Vanguelova), lv@ign.ku. dk (L. Vesterdal). Forest Ecology and Management 466 (2020) 118127 0378-1127/ Crown Copyright © 2020 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/). T