Crown plasticity enables trees to optimize canopy packing in mixed‐species forests

Abstract

Summary1. It has been suggested that diverse forests utilize canopy space more efficiently than speciespoor ones, as mixing species with complementary architectural and physiological traits allows trees to pack more densely. However, whether positive canopy packing-diversity relationships are a general feature of forests remains unclear. 2. Using crown allometric data collected for 12 939 trees from permanent forest plots across Europe, we test (i) whether diversity promotes canopy packing across forest types and (ii) whether increased canopy packing occurs primarily through vertical stratification of tree crowns or as a result of intraspecific plasticity in crown morphology. 3. We found that canopy packing efficiency increased markedly in response to species richness across a range of forest types and species combinations. Positive canopy packing-diversity relationships were primarily driven by the fact that trees growing in mixture had sizably larger crowns (38% on average) than those in monoculture. 4. The ability of trees to plastically adapt the shape and size of their crowns in response to changes in local competitive environment is critical in allowing mixed-species forests to optimize the use of canopy space. By promoting the development of denser and more structurally complex canopies, species mixing can strongly impact nutrient cycling and storage in forest ecosystems.

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

“…Most of the structural indices indicate that Scots pine is less variable, plastic, and multi-layered than beech (Table 6, column (4)). The structural differences between the monocultures of pine and beech are consistent with many other studies (Jucker et al, 2015;Kelty, 1992;Pretzsch, 2014). Scots pine represents a light demanding, rather crown-transparent and vertically oriented fast growing species with an early culminating course of growth (early successional species).…”

Functional composition drives ecosystem function through multiple mechanisms in a broadleaved subtropical forest

“…Zhang and Chen (2015) demonstrated that diversity is linked with increased biomass due to increasing tree size inequality in a boreal forest. Similarly, Jucker et al (2015) found that canopy packing was strongly associated with species richness in European permanent forest plots. Our results suggest that canopy packing may influence both AGB and CWP and that both NC and MR effects may contribute to EF indirectly by influencing canopy packing.…”

Automatic Assessment of Crown Projection Area on Single Trees and Stand-Level, Based on Three-Dimensional Point Clouds Derived from Terrestrial Laser-Scanning

“…Due to the fact that the allometric models do not reflect the crown plasticity, estimates of fractional crown cover and related metrics on the stand-level differ remarkably between TLS and allometric models. In mixed-species stands (like the experimental stand) where crown plasticity is pronounced [55,56], TLS is, therefore, clearly the preferable method.…”

“…Instead, a tree's CPA is represented by a circle, i.e., the most compact geometric form in two-dimensional space. Recent studies [55,56] have shown that, especially in mixed-species stands, crown plasticity enables trees to optimize canopy packing, to reduce inter-tree competition, and to maximize the utilization of available photoactive radiation. Obviously, the CPA map ( Figure 5) derived from the TLS data represents a much more efficient usage of the growing space than the maps derived from the allometric models.…”