Forest Ecology is the study of the relationships, in an environment dominated by trees, between the populations of plants, animals and microorganisms that are occupying this area, and the environment itself. Forested Ecosystems are communities of plants, animals and microorganisms, and the physical environment they occupy, in which trees are the dominant life form. This dominance by trees is important because it produces vertical stratification, in terms of livable space and micro-climate of that space. This vertical stratification distinguishes forested ecosystems from other ecosystem classifications. On a time scale, forested ecosystems are an ever-changing assemblage of species, dominated by trees, shaped by climate and other physical processes. On a spatial scale, forested ecosystems can be comparable to the "stand" or group of trees that are reasonably similar in age, structure and species composition, which occupy a contiguous space.