Wood quality in complex forests versus even-aged monocultures: review and perspectives

Mixing of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) enhances structural heterogeneity, and the effect increases with water availability

“…High ratios indicate a tree's or species' crown plasticity and its capacity spread into vacant canopy space (Assmann, 1970). However, high ratios can also indicate wide crowns and long branches, which mean larger branch diameters and a reduction of wood quality (Pretzsch and Rais, 2016).…”

“…Increases in species diversity and heterogeneity of other structural attributes can, e.g., stabilize and raise the productivity (Bielak et al, 2014;Lei et al, 2009;Liang et al, 2007;Jucker et al, 2014;Pretzsch et al, 2013Pretzsch et al, , 2015aRío and Sterba, 2009), stability (Griess and Knoke, 2011;Jactel and Brockerhoff, 2007), reduced sensitivity to drought (Grossiord et al, 2014;Metz et al, 2013), habitat diversity (Tews et al, 2004), plant and animal richness (Brunet et al, 2010;Ishii et al, 2004;Roth, 1976), and the aesthetic value (Schütz, 2002;Stölb, 2005) of forest stands. On the other hand more heterogeneous structures can have a negative effect on some taxa (Paillet et al, 2010), on the wood quality (Pretzsch and Rais, 2016), on the effort of forest inventory, planning, and management (von Gadow, 1998;von Gadow et al, 2002), and on the costs of opening up the stands to harvest the timber (Keegan et al, 1995;Kellogg et al, 1996).…”

“…Beech has a rather low self-tolerance in monocultures but competes strongly with pine, which is less plastic (Metz et al, 2013). The crown extension means longer and more branches and a reduction of wood quality of beech (Pretzsch and Rais, 2016;Wiedemann, 1951, p. 135). Interference by beech can reduce the number of branches of Scots pine, which can improve timber strength and stiffness (Pretzsch and Rais, 2016).…”

“…The crown extension means longer and more branches and a reduction of wood quality of beech (Pretzsch and Rais, 2016;Wiedemann, 1951, p. 135). Interference by beech can reduce the number of branches of Scots pine, which can improve timber strength and stiffness (Pretzsch and Rais, 2016). However, in older stands the high plasticity of beech can suppress and eliminate pine in individual tree mixtures regardless of whether it is competing laterally or from below by pushing its crowns upwards into the pine crowns (Wiedemann, 1951, p. 134).…”

Toward managing mixed-species stands: from parametrization to prescription

“…3) and thereby wood quality (Metz et al 2013, Zeller et al 2017. Biomass and leaf area allometry of trees are strongly affected by the spatial tree distribution within a stand and it is rather the stand structure than the species identity that is responsible for the difference in allometry of trees between mixed and monospecific stands (Pretzsch and Rais 2016). Mixing often increases crown width (Bayer et al 2013, Juchheim et al 2017, crown length (Pretzsch 2014) and the leaf mass ) of crowns compared with monocultures, but can decrease the root-shoot allometry (Thurm et al 2017), wood density (Zeller et al 2017), and stem slenderness (Wellhausen et al 2017).…”