Wider crown shyness between broad‐leaved tree species than between coniferous tree species in a mixed forest of Castanopsis cuspidata and Chamaecyparis obtusa

Abstract

Persistent openings (gaps) between adjacent crowns at similar heights can be found in tall forests. Such openings are called "crown shyness" and are formed through the collision of tree crowns during high winds. While crown shyness has been studied in plantations, much less studied in natural forests despite its importance for light acquisition, competition, and coexistence. In this study, we focused on a mixed forest in Japan, and examined a hypothesis that broadleaved tree species, which often have top-wide crowns, have wider crown shyness than coniferous tree species, which often have narrow cone-shape crowns, because top-wide crowns may be more exposed to wind and more likely to collide with their neighbors. Crown shyness, which was measured by drone imagery, was clearly found between individuals of the broad-leaved tree species Castanopsis cuspidata but not between the coniferous tree species Chamaecyparis obtusa. This interspecific difference may be associated with differences in crown shape; Castanopsis had wider (1.57-fold) and shallower (0.64-fold) crowns than Chamaecyparis. Within Castanopsis, the size of crown shyness tended to negatively correlated with stem diameter and positively correlated with stem slenderness. Our study showed that the difference in crown shape among species is one of the key factors in determining the size of crown shyness. Top-wide crowns of broad-leaved trees compared to conifers may have a competitive advantage in light interception, but it may come at the cost of crown collisions with adjacent crowns and resulting in persistent openings at the canopy layer.

Branch Elongation, Bud Durability, and Wind-Generated Crown Movement Associated with Crown Abrasion in Deciduous Trees

“…This stand development pattern associated with crown abrasion for these two species was present in both natural [22] and planted stands [26]. Similar crown abrasion effects in mixed-species deciduous stands have been reported in Germany [15] and in New England, USA [27], with mixed deciduous species, in mixed conifer stands in the Pacific Northwest, USA [28], and with mixed coniferdeciduous species in Japan [12].…”

“…A loss of horizonal crown size, extended vertical crowns, and reduction of tree leaf area resulted in tall, slender trees that sway more during windy conditions with a greater chance that branches collide with adjacent trees. Recently, Onoda and Bando [12] and van der Zee et al [13] used remote sensing technology to describe horizontal and vertical expressions of crown abrasion. Putz et al [14] observed crown abrasion in Avicennia germinans L. (black mangrove) between branches on the same tree and branches of adjacent trees.…”

Responses of Visual Forms to Neighboring Competition: A Structural Equation Model for Cotinus coggygria var. cinerea Engl.

“…More accurately, sunlight intensity would increase with relative tree height, as a relatively tall tree with taller neighbors would still be shaded. In the broad-leaved forest, crown shyness, which describes the phenomenon whereby tree crowns avoid growing into each other, producing a puzzle-like pattern of complementary tree crowns in the canopy [35], was found between individual trees [36]. As competitions lead to trees growing asymmetrical crowns instead of their ideal symmetrical shape, measurements related to tree size rather than that representative of the ideal symmetrical shape were chosen.…”

Changes in Soil Physico-Chemical and Microbiological Properties During Natural Succession: A Case Study in Lower Subtropical China

“…It was reported that the diversity of species and canopy increased during the development of forest phytocenoses, together with the enhancement of the connection between populations (Bruelheide et al, 2011;Zhang et al, 2021). In addition, those changes in forest vegetation mentioned above also affect the amount of solar radiation reaching the forest floor (Dietz et al, 2020;Onoda and Bando, 2021). The inter-relationship between the vegetation and climate factors forms distinctive microhabitat conditions in different forests, which alters soil properties by affecting the process of litter decomposition and root development, and further impacts the coupling relationship of soil C-N, C-P, and N-P.…”