Observation and Modeling of Net Ecosystem Carbon Exchange Over Canopy

Abstract

A plant canopy, a collection of leaves, is an ecosystem-level unit of photosynthesis that assimilates carbon dioxide and exchanges other gases and energy with the atmosphere in a manner highly sensitive to ambient conditions including atmospheric carbon dioxide and water vapor concentrations, light and temperature, and soil resource availability. In addition to providing carbon skeletons and chemical energy for most of the living organisms, these key canopy functions affect global climate through modification of atmospheric carbon dioxide concentration and through altering surface albedo. This interaction, the climate-carbon cycle feedback, is one of the most uncertain processes for projection of future global climate. This book describes our current knowledge of canopy photosynthesis that has accumulated over the last hundred years since the pioneering study of P. Boysen Jensen. The book provides a comprehensive analysis of plant canopy physiology, ecology and physics with emphasis on predictive modeling techniques. The book is divided into five parts covering hierarchy of canopy processes in time and space. Two chapters in Part 1 discuss the basic physical processes on light attenuation and energy transfer in plant canopies, while three chapters in Part 2 deal with the principle mechanisms of leaf gas-exchange regulation and the patterns and mechanisms of variations in leaf traits. Three chapters in Part 3 focus on whole-plant processes in plant canopies. Part 4 (in four chapters) describes how vegetation functions are assessed by modeling, eddy-covariance techniques, and remote sensing and forest inventory. Finally, three chapters in Part 5 discuss the relationships between canopy photosynthesis and other vegetation processes in plant stands. From the Series Editors; Series Editors; Contents; Preface; The Editors; Contributors; Author Index; Part I: Physical Processes in Leaf Canopies; Chapter 1: Light Distribution; I. Incoming Radiation; A. Its Total Value; B. Spectral Energy Distribution; C. Directional Distribution; Box 1.1: Solar Coordinates; D. Radiance and Irradiance; II. Modelling Radiation in Leaf Canopies; A. Black Horizontal Leaves; B. Non-horizontal Leaves; C. Leaf Angle Distribution; D. Leaf Scattering and Canopy Reflection; 1. The Reflection Coefficient of a Leaf Canopy with a Large Leaf Area Index. 2. Extinction of Radiation Within the Leaf CanopyIII. Absorption of Radiation in Row Crops; A. Directional Distribution of Incoming Radiation; B. Row Crops; 1. Infinite LAI, Black Leaves; 2. Non-infinite LAI, Black Leaves; 3. Loss of Radiation due to Plant Arrangement in Rows; IV. Direct and Diffuse Light in Photosynthesis Modeling; Box 1.2: Example of Calculation of Photosynthesis When There Is only Diffuse Radiation; Box 1.3: Example of Calculation of Canopy Photosynthesis When There Is also Direct Radiation; V. Conclusions and Prospects; References. Chapter 2: Leaf Energy Balance: Basics, and Modeling from Leaves to CanopiesI. Introduction: Why Leaf Energy Balance is Important to Model; Box 2.1 Inferring Water Stress and Water Use from Leaf Temperature; II. Calculations of Leaf Energy Balance: Basic Processes in the Steady State; A. Energy Balance Equation in the Steady State; 1. Chief Components of Leaf Energy Balance; 2. Role of Energy Flows in Transient Heating, Photosynthesis, and Respiration; B. Defining the Individual Terms of the Energy Balance Equation; 1. Shortwave Energy Input; 2. Thermal Infrared Input. 3. Thermal Infra-Red Losses4. Latent Heat Loss; 5. Convective Heat Exchange; 6. Solving the Leaf Energy Balance Equation; Box 2.2 Iterative Solution of the Leaf Energy Balance Equation; C. Leaves in Artificial Environments: Growth Chambers, Greenhouses, and Warming Experiments; D. Detection of Leaf Temperature and of Energy-Balance Components; E. Meeting the Challenges of Measurement and Theory; III. Physiological Feedbacks Affecting Leaf Energy Balance; A. Dependence of Stomatal Conductance on Environmental Drivers; B. Biochemical Limitations of Photosynthesis. C. Solving a Combined Stomata-Photosynthesis ModelD. Advanced Problems; IV. Transients in Energy Balance and in Processes Dependent on Temperature; A. Independence of Different Leaf Regions; B. Dynamics in Leaf Temperature After Changes in Energy Balance Components; 1. Time-Dependent Changes in Temperature After Modifications in Radiation Input; 2. Changes in Temperature After Modifications in Convective Heat Exchange; 3. Importance of Temperature Transients for Photosynthesis; V. Leaves in Canopies; A. General Principles.