Effect of forest management on future carbon pools and fluxes: A model comparison Ste ´phanie Schmid a , Esther Thu ¨rig b , Edgar Kaufmann b , Heike Lischke b , Harald Bugmann a, * a ETH Zu ¨rich, Forest Ecology, Department of Environmental Sciences, Universita ¨tstrasse 16, 8092 Zu ¨rich, Switzerland b Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Zu ¨rcherstrasse 111, 8903 Birmensdorf, Switzerland Received 30 June 2005; received in revised form 7 July 2006; accepted 21 September 2006 Abstract Currently, there is a strong demand for estimates of the current and potential future carbon sequestration in forests, the role of management practices, and the temporal duration of biotic carbon sinks. Different models, however, lead to different projections. Model comparisons allow us to assess the range of potential ecosystem responses, and they facilitate the detection of the strengths and weaknesses of particular models. In this study, the empirical, individual-based forest models MASSIMO, the semi-empirical individual-based forest models SILVA – both combined with the soil model YASSO – and the process-based, biogeochemical model Biome-BGC were used to assess the above- and belowground carbon pools and net fluxes of several forested regions in Switzerland for the next 100 years under four different management scenarios: (1) the current harvest amounts were used, (2) harvest was intensified by reducing the amount of large tree dimensions, (3) harvest was reduced to a minimum by only maintaining the protection function in mountain forests and avoiding pests and diseases, and (4) harvest was adjusted to achieve maximum sustainable growth. The results show that the three models projected similar patterns of net carbon fluxes. The models estimated that in the absence of large-scale disturbances the forest biomass and soil carbon can be increased, particularly under scenario 2, and therefore, forests can be used as carbon sinks. These sinks were estimated to last for a maximum of 100 years. Differences between the management scenarios depend on the time period considered: either net carbon fluxes are maximized at a short term (30–40 years) or at a longer term (100 years or more). In contrast to the similar carbon fluxes, some carbon pools projected by the models differed strongly. These differences in model behaviour can be attributed to model-specific responses to the strongly heterogeneous Swiss climate conditions and to different model assumptions. To find the optimum strategy in terms of not only maximizing carbon sequestration but climate protection, it is essential to account for wood-products and particularly substitution of fossil fuel in the model simulations. # 2006 Elsevier B.V. All rights reserved. Keywords: Carbon budget; Forest management; Biome-BGC; SILVA; YASSO; MASSIMO; Switzerland 1. Introduction Forest management influences the sequestration and release of carbon in forest biomass, soil, and wood products (Houghton, 1996; Harmon and Marks, 2002; Kaipainen et al., 2004). In the framework of the Kyoto Protocol, countries can decide to credit managed forests as carbon sink/source according to Article 3.4 of the Protocol (UNFCCC, 1997). Therefore and for the annual green house gas inventory to the Climate Change secretariat, countries are obliged to assess their carbon pools with a high precision. Models are important to estimate changes of these pools and the associated carbon fluxes. Models can also be applied to assess the influence of different management regimes on long-term carbon sequestra- tion. There is a suite of techniques for predicting carbon pools and fluxes (c.f. Ruimy et al., 1999; Landsberg, 2003). Such approaches include inverse modelling based on a network of atmospheric CO 2 measurements (Gurney et al., 2002), or on detailed measurements of gas exchange above the forest (eddy correlation measurements, Baldocchi, 2003), biogeochemical models (Running and Hunt, 1993), models for the analysis of land-use change (Houghton, 2003a) and for the analysis of forest inventory data (Fang et al., 2001; Goodale et al., 2002; Shvidenko and Nilsson, 2002). All the models used for such purposes are situated somewhere on the gradient between empirically based models and process models (Korzukhin et al., 1996). Process-based www.elsevier.com/locate/foreco Forest Ecology and Management 237 (2006) 65–82 * Corresponding author. Tel.: +41 1 632 32 39; fax: +41 1 632 13 58. E-mail address: harald.bugmann@env.ethz.ch (H. Bugmann). 0378-1127/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2006.09.028