Two fundamental properties differentiate the ecology of plants and animals: plants are phototrophic and sessile, while animals are heterotrophic and mobile. Individual plant success is dependent upon its arrival as a seed at a suitable location and upon its ability to occupy that site and tolerate the vicissitudes of the environment. Avoidance of predation (herbivory) by plants is dependent upon mechanical, chemical, and life cycle characteristics. Animals, on the other hand, seek their food energy sources, move within and between habitats to maintain a suitable habitat, attract mobile mates, and, in addition to mechanical and chemical deterrence, depend upon behavior for predator avoidance.
Plants have specific requirements of the environment in which they grow. For example, plants require light, nutrients, water, carbon dioxide, and oxygen. Each of these is a resource needed for growth and reproduction. The acquisition of resources and the tolerance range of plants to variation in availability of these resources determine the presence or absence of plants at specific sites. Additionally, environmental variables such as temperature, wind, physical soil properties, soil pH, fire, salinity, atmospheric humidity, and the presence ofherbivores and dispersers are all conditions that affect the ability ofplants to colonize and utilize the resources at a site. Finally, resources are dispersed over time and space, which provides dimensions in which plants are found.
This entry will examine the properties of the principal resources of plants, the factors affecting the availability of resources to plants, and the response of plants to these variations. Finally, how these resources influence the interactions of plants to form dynamic biotic communities will be discussed.
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