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LECTURE OVERVIEW

Basic statement:

The open growth system of trees permits a variety of branching patterns, leaf placements and overall crown shapes. The geometric forms of some trees is so distinctive that they can be identified by their silhouettes alone. Different tree forms have been addressed by several models that seek to explain the adaptive value of branching patterns.

Key ideas:

Henry Horn developed a model to explain the differences in branching pattern and leaf placement of angiosperm trees. Light and heat are the primary selective agents in this model. The model suggests that leaf-size and leaf-placement patterns are strategies to maximize photosynthesis and minimize heat stress at different stages of forest succession. Other models by Leopold and by Stevens provide conceptual frameworks to explain stem form and branching pattern. All models stress the adaptive nature of tree architecture.

Important terms:

monolayer	deliquescent
multilayer	excurrent

LECTURE OUTLINE (powerpoint version)

Introduction

• light can limit tree growth/performance
• leaves cast shadows that disappear with distance beneath leave
• photosynthesis is light saturated at fairly low light intensities
• leaf temperature is proportional to light intensity

PREDICTIONS FROM CONCEPTS OF ADAPTIVE GEOMETRY

What is the logic behind these predictions?

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