Tamm Review: On the strength of evidence when comparing ecosystem functions of mixtures with monocultures

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

“…1), not only of monocultures but especially of mixed-species stands (Forrester and Pretzsch, 2015;Forrester and Bauhus, 2016;Pretzsch, 2014). A deeper insight into stand structure and its dependency on site conditions is also important for the further development of silvicultural guidelines for the management of mixed stands which may address multiple services (Río et al, 2016).…”

“…but more continuously and later culminating course of growth (late successional species). As a result of those species-specific traits, the mixed stands of both species differ significantly from both monocultures, i.e., they show strong additive effects (Forrester and Pretzsch, 2015). Other common mixtures of early and late successional or shade intolerant and tolerant species such as Scots pine and lime tree (Tilia cordata), Scots pine and red oak (Quercus rubra), or European larch (Larix decidua) and beech, larch and Norway spruce (Picea abies), silver birch (Betula pendula) and spruce, silver birch and silver fir (Abies alba), or red alder (Alnus rubra) and Douglas-fir (Pseudotsuga menziesii) may behave similarly.…”

“…An interesting question is to what extent any differences between mixture and monoculture are just a weighted average of the monocultures, also referred to as an additive effect, or whether the mixture characteristics depart from the weighted average of the monocultures, sometimes referred to as non-linear or multiplicative effects (Kelty, 1992;Forrester and Pretzsch, 2015). The term ''additive effect" underlines that this kind of mixing effect results from nothing more than selecting the species and adding up the characteristics of the monocultures (Forrester, 2014;Kelty, 1992).…”

Forest Carbon Sequestration: The Impact of Forest Management

“…Similarly, the productivity by space occupancy of many species is frequently higher when admixed with other species due to facilitation and/or complementarity, often resulting in over-yielding or even transgressive over-yielding compared to corresponding monospecific stands (e.g. Río and Sterba, 2009;Condés et al, 2013;Pretzsch et al, 2015). Forest productivity is generally evaluated based on volume or aboveground biomass per unit area, calculated via tree volume or tree biomass allometric equations.…”

“…Forest productivity is generally evaluated based on volume or aboveground biomass per unit area, calculated via tree volume or tree biomass allometric equations. These were often developed using sample data from monospecific stands, resulting in less accurate biomass estimates (Forrester and Pretzsch, 2015). Carbon content per unit of biomass may also vary, depending on whether stands are mixed or monospecific.…”