Study GuidePlant Biology–Ecosystem Structure and Function1. Ecosystem Structure: Plant CommunitiesPlants usually make up the most visible and important part of an ecosystem. In fact, ecosystems andplant communities are often named after thedominant plants—the plants that are most abundant orthe largest. These dominant plants shape the environment around them. They influence things likelight, temperature, soil conditions, and even which other organisms can live there.A plant community isnot random. It is made up of populations of plants that can survive the specificconditions of that area. Each plant species has atolerance range, which is the range ofenvironmental conditions (such as temperature, moisture, and soil type) in which it can grow andsurvive. Only plants whose tolerance ranges match the conditions of the site can become part of thatcommunity.1.1Succession: How Plant Communities Change Over TimeEven ecosystems that seem stable are always changing. One of the easiest ways to see this changeis throughecological succession. Succession is the gradual change in plant species living in anarea over time.There aretwo main types of succession:1.1.1. Primary SuccessionPrimary succession happens onnewly exposed landwhere no soil exists. This can occur afterevents like volcanic eruptions or landslides. Because there is no soil at first, plants and soil developatthe same time. Early plants help break down rock and add organic matter, slowly forming soil.1.1.2. Secondary SuccessionSecondary succession occurs when plants are removed from an area, butsoil is already present.This can happen after forest fires, floods, farming, or logging. Plants grow back more quickly than inprimary succession because the soil already contains nutrients. Over time, both the plant communityand the soil continue to change as new species growabove ground and roots develop below ground.Preview Mode
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