Canopy space filling and tree crown morphology in mixed-species stands compared with monocultures

By Hans Pretzsch. 2014

585 citations recorded by the source corpus.

Abstract Mixed-species forest stands are well explored in their favourable ecological, economical, and socio-economical functions and services compared with pure stands, but still poorly understood in their structure and functioning. Canopy structure and tree morphology affect the environmental conditions within the stand, the tree growth, and by this most forest functions and services. Here, I review how canopy structure and crown morphology in mixed stands can differ from pure stands and how this depends on the selection of tree species and interactions between them. The focus is on the macrostructure of canopy and crowns derived from the trees’ positions, their convex crown hulls, and their space filling with branches. In mixed canopies the sum of the crown projection area, but not the ground coverage by crowns, mostly exceeds pure stands due to multiple crown overlaps. The interspecific differences in crown shape and allometric scaling cause a ‘selection effect’ when complementary species are combined. In interspecific environment furthermore ‘true mixing effects’ like intraspecific shifts in size, shape, and inner space filling of crowns may occur. The much denser and more plastic canopy space filling in mixed stands may increase light interception, stand density, productivity, and growth resilience to disturbances. I discuss the relevance of interspecific interactions for forest management, model building, and theory development and draw perspectives of further research into stand canopy and crown structure.

Subfields: Global and Planetary Change, Nature and Landscape Conservation

View Paper: https://www.semanticscholar.org/paper/7f7dcc5494ae23b366f13959d3b50b69a7a9d2aa

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Citations in the corpus

Tree ring wood density of Scots pine and European beech lower in mixed-species stands compared with monocultures (2017, background): “crown morphology (Bayer et al., 2013; Pretzsch, 2014) and root-shoot relationship (Bolte et al.”
Species interactions increase the temporal stability of community productivity in Pinus sylvestris–Fagus sylvatica mixtures across Europe (2017, unknown): “Using these functions may had caused biased estimations of biomass growth as mixing tree species can modify tree allometry (Pretzsch 2014) as well as between-tree growth partitioning (Binkley et al. 2003; Pretzsch & Schütze 2014), suggesting the need of specific functions for mixtures (Forrester &…”
Increasing stand structural heterogeneity reduces productivity in Brazilian Eucalyptus monoclonal stands (2016, background): “…differences in growth and allometry (Kelty, 1992; Forrester et al., 2006), or with the plasticity of a given species that allows it to modify its allometry (or physiology, phenology) when growing in a mixture that is complementary to other species (Bauhus et al., 2004; Pretzsch, 2014).”
Crown size and growing space requirement of common tree species in urban centres, parks, and forests (2015, background): “…stress that overarching scaling factors oversimplify plant llometry (Niklas, 2004) and that allometric exponent and factor ay vary with species (Pretzsch, 2014), competition (Dieler and retzsch, 2013; Price et al., 2010; Purves et al., 2007), and age (Genet t al., 2011). etermining upper,…”
Aboveground carbon storage is driven by functional trait composition and stand structural attributes rather than biodiversity in temperate mixed forests recovering from disturbances (2018, background): “Stand structural attributes are often characterized using stand-level metrics of tree size inequality or diversity based on tree heights or diameters at breast height (DBH) (Pretzsch 2014; Ali et al. 2016).”
Identifying the tree species compositions that maximize ecosystem functioning in European forests (2018, background): “In closed canopy forests, this is primarily due to more efficient light use when species with contrasting canopy traits co-occur (Fichtner et al., 2017; Pretzsch, 2014; Zhang, Chen, & Reich, 2012).”
Diversity and competition influence tree allometric relationships – developing functions for mixed‐species forests (2017, background): “…in some cases the predicted variable can differ by more than 100%, for a given diameter (Getzin & Wiegand 2007; Laclau et al. 2008; Thorpe et al. 2010; Bayer, Seifert & Pretzsch 2013; Metz et al. 2013; Barbeito, Collet & Ningre 2014; Forrester & Albrecht 2014; Jucker et al. 2014; Pretzsch 2014).”
Effects of crown architecture and stand structure on light absorption in mixed and monospecific Fagus sylvatica and Pinus sylvestris forests along a productivity and climate gradient through Europe (2018, background): “Greater absorption of photosynthetically active radiation (APAR) is often proposed as a reason for greater productivity in mixed- species forests than in monocultures (Forrester & Bauhus, 2016; Kelty, 1992; Morin, Fahse, Scherer- Lorenzen, & Bugmann, 2011; Pretzsch, 2014).”
The greater resilience of mixed forests to drought mainly depends on their composition: Analysis along a climate gradient across Europe (2021, background): “This can allow mixed forests to exploit canopy space more efficiently (Morin et al. 2011, Pretzsch 2014; Toïgo et al. 2018), thereby maximizing light interception (Ammer 2019), even under drought conditions.”
Crown plasticity enables trees to optimize canopy packing in mixed-species forests (2015, background): “2), indicating that mixed-species forests are able to make more efficient use of aboveground space compared to monocultures (Morin et al. 2011; Pretzsch 2014).”
Synthesis and future research directions linking tree diversity to growth, survival, and damage in a global network of tree diversity experiments (2018, background): “, 2017) has demonstrated canopy niche differentiation, resulting in a more efficient space use and light interception in mixtures than in monocultures (Pretzsch, 2014).”
Stand growth and structure of mixed-species and monospecific stands of Scots pine (Pinus sylvestris L.) and oak (Q. robur L., Quercus petraea (Matt.) Liebl.) analysed along a productivity gradient through Europe (2019, unknown): “2018; Pretzsch 2014) or below-ground (Augusto et al.”
Response of sugar maple (Acer saccharum, Marsh.) tree crown structure to competition in pure versus mixed stands (2016, background): “However following the theory of higher resource acquisition trait complementarity in diversified environments (Hooper et al., 2002; Pretzsch, 2014; Tilman et al., 2001), one would expect a higher total space occupation in mixed stands due to niche partitioning.”
Functional diversity enhances silver fir growth resilience to an extreme drought (2016, background): “The partition in light resource acquisition results in a more efficient use of above-ground resources and greater ecosystem functionality (Pretzsch 2014).”