Silvicultural prescriptions for mixed-species forest stands. A European review and perspective

Abstract

Compared with far-developed measures and methods for mono-specific forest stands, the silvicultural prescriptions for mixed-species stands are at their early beginning. However, they are essential for the well-conceived establishment, design, and control of mixed-species stands, currently promoted in many countries worldwide. Here, we review the state of the art and we further develop silvicultural prescriptions for mixed-species stands for steering of experiments, stand modeling, and silviculture. We review which aspects of tree species mixing are most relevant for management goal achievement. We found the maintenance of species diversity and structural heterogeneity for ecological purpose, stabilizing productivity, and social-economic performance as main objectives. We give an overview of quantitatively formulated silvicultural prescriptions for steering mixed-species stands for forest practice, long-term experiments, forest stand models. Compared with the sophisticated guidelines for mono-specific stands, prescriptions for mixed stand are often mainly qualitative and vague. Then, we introduce methodological approaches in development for steering mixture: measures for spatial and temporal separation, species-specific growing space requirements for crop trees, coefficients for equivalence and density modification, and basic relationships for steering tree number and area-based mixing proportions. Finally, we draw conclusions for further development of methodological approaches for silvicultural steering of experiments, implementation in stand simulators, and for silvicultural operations. We see the need for improving the quantitative spatially explicit rules based at tree or cohort level, for substantiating the knowledge on species-specific allometry, growing area, tree-to-tree distances, and position-dependent competition indices for steering tree removal. We discuss the prospects and limitations of establishing silvicultural prescriptions for mixed-species stands that inevitably will be more complicated than those for mono-specific stands, and we draw conclusions for next steps in science and practice.

Accounting for forest management in the estimation of forest carbon balance using the dynamic vegetation model LPJ-GUESS (v4.0, r9710): implementation and evaluation of simulations for Europe

“…Forests make up the largest portion of the current land carbon sink and are estimated to have absorbed 20 %-50 % of CO 2 emitted by fossil fuel combustion and industry during the first decade of this century (Pan et al, 2011;Le Quéré et al, 2018;Pugh et al, 2019). The suggested basis for this carbon uptake is the recent history of the drivers increasing productivity mentioned above, especially increased CO 2 , and the recovery of carbon pools in regrowth forests (forests regrowing after natural or anthropogenic stand-destroying disturbances; Pugh et al, 2019).…”

“…Forests make up the largest portion of the current land carbon sink and are estimated to have absorbed 20 %-50 % of CO 2 emitted by fossil fuel combustion and industry during the first decade of this century (Pan et al, 2011;Le Quéré et al, 2018;Pugh et al, 2019). The suggested basis for this carbon uptake is the recent history of the drivers increasing productivity mentioned above, especially increased CO 2 , and the recovery of carbon pools in regrowth forests (forests regrowing after natural or anthropogenic stand-destroying disturbances; Pugh et al, 2019). The size of the forest carbon sink has been estimated by using bookkeeping methods (Pan et al, 2011;Houghton et al, 2012) and global vegetation models (Luyssaert et al, 2008;Shevliakova et al, 2009;Pugh et al, 2019), but this sink is associated with relatively large uncertainties, resulting in differing estimates using different approaches and models.…”

“…The suggested basis for this carbon uptake is the recent history of the drivers increasing productivity mentioned above, especially increased CO 2 , and the recovery of carbon pools in regrowth forests (forests regrowing after natural or anthropogenic stand-destroying disturbances; Pugh et al, 2019). The size of the forest carbon sink has been estimated by using bookkeeping methods (Pan et al, 2011;Houghton et al, 2012) and global vegetation models (Luyssaert et al, 2008;Shevliakova et al, 2009;Pugh et al, 2019), but this sink is associated with relatively large uncertainties, resulting in differing estimates using different approaches and models. Key uncertainties include the magnitude of CO 2 fertilisation -which may be limited by soil availability of nutrients such as N and P (Zaehle and Dalmonech, 2011;Jiang et al, 2020) -and the extent of shifting cultivation in the tropics (Heinimann et al, 2017).…”

“…The carbon sink of European forests in 2000-2007 has been estimated at 0.27 Pg C yr −1 or about 12 % of the global carbon sink of established forests (Pan et al, 2011). Europe has been identified as a region where regrowth forests dominate carbon sequestration (Pugh et al, 2019) and has a history of thousands of years of human impact on forest structure and species composition (Perlin, 2005). Forest management practices of the past few hundred years are relatively well documented (McGrath et al, 2015).…”

“…The model has been shown to represent standlevel vegetation growth and succession successfully (Smith et al, 2014). It has been used to estimate forest vulnerability to climate change (Seiler et al, 2015) and carbon mitigation potential of regrowth forests and forests under alternative management scenarios (Pugh et al, 2019;Krause et al, 2020). Earlier versions of LPJ-GUESS have been modified to enable analysis of clear-cut forest management and the effects of wind damage and insect outbreaks (Lagergren et al, 2012;Jönsson et al, 2012).…”