Forests cover approximately 30% of total land area and function as habitats for organisms, hydrologic flow modulators, and soil conservers, constituting one of the most important aspects of the Earth’s biosphere. The canopy is one of the uppermost levels of a forest, below the emergent layer, formed by the tree crowns. The canopy is home to unique flora and fauna not found in other layers of a forest. Trees in the canopy are able to photosynthesise very rapidly thanks to the large amount of light, so it supports the widest diversity of plant as well as animal life in most rainforests. This book presents a wide variety of topics on the ecosystem in forest canopies. Included is a study on light distribution patterns and how it effects the daily photosynthesis of herbaceous vegetation. Recent progress, concerns, and future directions in simulations of vegetation processes are presented as well, in the terrestrial biosphere model that is coupled to a climate system model.