11:45 AM - 12:00 PM
[ACG46-10] Understanding the Competition and Coexistence of Conifers and Broadleaf Trees with Different Canopy Morphologies
Keywords:Canopy morphology, Conifers and broadleaf trees, Light niche partitioning, Dynamic vegetation model
Conifers generally have narrow and deep canopies, whereas broadleaf trees have spherical canopies. One proposed reason for this difference is that the solar angle is lower in high-latitude regions where conifers dominate. At the same time, in the low-latitude areas where broadleaf trees are more prevalent, the solar angle is higher. This suggests that their respective canopy morphologies have evolved to maximize sunlight capture. In mixed forests where conifers and broadleaf trees coexist, previous studies indicated differences in canopy structure contribute to niche partitioning of light resources, enabling their coexistence. A field study has reported that forests with diverse canopy morphologies exhibit higher productivity.
However, previous studies have used relatively simple structural models that did not sufficiently consider the mechanisms behind canopy morphology evolution and coexistence conditions. In this study, we used the spatially explicit individual-based Dynamic Global Vegetation Model (SEIB-DGVM) to analyze the impact of canopy morphology differences on competition dynamics and ecosystem productivity in mixed forests. This model incorporates the following novel elements in addition to those considered in conventional models: (1) competition for space with neighboring individuals during canopy expansion, (2) self-pruning of lower branches due to self-shading and shading from surrounding trees, and (3) reduction of the basal cross-sectional area of the canopy due to dieback of the lower canopy as a result of self-shading and shading from surrounding trees, leading to decreases in maximum leaf area and maximum canopy width.
In this study, we planted conifer-type and broadleaf-type saplings with different canopy morphologies in a virtual forest and conducted a 100-year competition simulation. The results showed that the relative advantages of conifer-type and broadleaf-type canopies varied depending on tree density, solar angle, and solar radiation composition (direct vs. diffuse light). However, frequency-dependent selection (adverse frequency-dependent selection), which promotes the coexistence of tree species with different canopy morphologies, was not observed. Additionally, no increase in plant productivity was observed due to the coexistence of tree types with varying canopy shapes.
This study enhances our understanding of the factors contributing to forming mixed forests composed of conifers and broadleaf trees and the mechanisms underlying productivity improvement. These findings are expected to have applications in the management strategies of both natural and planted forests.
However, previous studies have used relatively simple structural models that did not sufficiently consider the mechanisms behind canopy morphology evolution and coexistence conditions. In this study, we used the spatially explicit individual-based Dynamic Global Vegetation Model (SEIB-DGVM) to analyze the impact of canopy morphology differences on competition dynamics and ecosystem productivity in mixed forests. This model incorporates the following novel elements in addition to those considered in conventional models: (1) competition for space with neighboring individuals during canopy expansion, (2) self-pruning of lower branches due to self-shading and shading from surrounding trees, and (3) reduction of the basal cross-sectional area of the canopy due to dieback of the lower canopy as a result of self-shading and shading from surrounding trees, leading to decreases in maximum leaf area and maximum canopy width.
In this study, we planted conifer-type and broadleaf-type saplings with different canopy morphologies in a virtual forest and conducted a 100-year competition simulation. The results showed that the relative advantages of conifer-type and broadleaf-type canopies varied depending on tree density, solar angle, and solar radiation composition (direct vs. diffuse light). However, frequency-dependent selection (adverse frequency-dependent selection), which promotes the coexistence of tree species with different canopy morphologies, was not observed. Additionally, no increase in plant productivity was observed due to the coexistence of tree types with varying canopy shapes.
This study enhances our understanding of the factors contributing to forming mixed forests composed of conifers and broadleaf trees and the mechanisms underlying productivity improvement. These findings are expected to have applications in the management strategies of both natural and planted forests.