Crown responses to neighbor density and species identity in a young mixed deciduous stand

Abstract

Key message Density was more important in shaping crown structure than neighbor species identity. Both species showed high crown plasticity at alternative levels, which may explain species coexistence in mixed broadleaved forests with functionally similar species. Abstract Understanding crown response to local competition is essential to predicting stand development in mixed stands. We analyzed data from an 8-year-old field experimental plantation mixing two species according to a crossed gradient of density and species proportion to quantify the effect of a broad range of local neighborhood conditions on the development of young trees at multiple crown levels. We used Fagus sylvatica and Acer pseudoplatanus, as two model deciduous species. They are considered functionally equivalent at the young stages, but with contrasting architectural patterns. For both species: (1) changes in density explained more of the variation on crown development than species proportion (2) much of the effect of competition was accounted for by variables at the stem level, while branch and leaf development within crowns were not directly altered by competition. Both species were able to modify their crowns at the stem level to compete with intra-and inter-specific neighbors: Acer and Fagus were taller with a highest proportion of Fagus as neighbors; Fagus displayed a lower crown base when the proportion of Fagus decreased, while Acer had a lower crown base when the proportion of Fagus around it increased. Both species showed common shapes in allometric relationships but contrasting responses at alternative crown levels. Acer exhibited broader intra-specific variation in its height-diameter relationship and in its crown length, while Fagus displayed higher individual variation of branch development and leaf area than Acer. This study demonstrates that differences in crown development strategy of each species in response to changes in local neighborhood conditions are an important factor in maintaining species coexistence in broadleaved forests and designing mixtures that persist over time.

Growth and yield of mixed versus pure stands of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) analysed along a productivity gradient through Europe

“…Furthermore, canopy filling-diversity relationships when growing in mixtures have found to be constant despite differences in species composition and climate among sites (Jucker et al 2015). However, canopy space filling seems more affected by architectural properties of the species in the mixture rather than by species richness itself Barbeito et al 2014).…”

Forest management and carbon sequestration in the Mediterranean region: A review

“…Most of the tree biomass models developed to estimate forest carbon have been fitted as species-specific models. However, tree allometry depends on several factors such as site conditions or species composition (e.g., Barbeito et al, 2014;Pretzsch, 2014). The applicability of species-specific biomass models developed in pure stands should be tested in mixed stands, and specific models for mixed stands or generalized equations for admixtures should also be developed in order to obtain accurate carbon estimations.…”

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

“…These differences in crown morphology, as well as inter-specific differences in height, can result in a more efficient packing of tree crowns within the canopy space and an increased light absorption by individual tree crowns of a given species and size in mixtures compared with monocultures (Bauhus et al, 2004;Forrester and Albrecht, 2014). However, canopy space filling seems more affected by morphological properties of the species in the mixture rather than by species richness itself (Barbeito et al, 2014;Seidel et al, 2013).…”