| Community Response to Environment |
Communities change in composition and structure over time in response to changing environmental conditions. This change is orderly, sequential, and leads to a climax community, which is in near equilibrium with the environment. |
| Ecological Succession |
The gradual and predictable change in species composition of a given area over time. During succession, some species colonize and become more abundant while others decline or disappear. |
| Sere |
The entire sequence of communities that change successively in a given area during ecological succession. |
| Seral Stages (Seral Communities) |
The individual transitional communities in a sere. There is a change in species diversity, the number of organisms, and total biomass through successive seral stages. |
| Climax Community |
The final, stable community that remains in equilibrium with the environment as long as it is unchanged. |
| Primary Succession |
Succession that begins in areas where no living organisms previously existed (e.g., bare rock, newly cooled lava). It is a slow process since soil formation is required for plant growth. |
| Secondary Succession |
Succession that occurs in areas where the natural biotic community has been destroyed, but soil or sediment remains (e.g., abandoned farmlands, burned forests). This process is faster than primary succession. |
| Factors Influencing Succession |
Succession is influenced by the presence of soil, water availability, environmental conditions, and propagules (seeds or other forms of reproduction). |
| Pioneer Species |
The first species to colonize a bare area during primary succession. In terrestrial environments, these are often lichens, which help in soil formation. In aquatic environments, phytoplanktons serve as pioneers. |
| Hydrarch Succession |
Succession that occurs in wet areas. The series progress from hydric (very wet) conditions to mesic (moderate) conditions. |
| Xerarch Succession |
Succession that occurs in dry areas. The series progress from xeric (very dry) conditions to mesic (moderate) conditions. |
| Mesic Conditions |
Medium water conditions that result from both hydrarch and xerarch successions, neither too dry nor too wet. |
| Human and Natural Disturbances |
Disturbances such as fire and deforestation can reset a seral stage to an earlier one, creating new conditions that favor some species while discouraging others. |
| Succession of Plants (On Rocks) |
Pioneer species like lichens colonize bare rocks, followed by bryophytes, then higher plants, eventually leading to a climax forest community. |
| Succession of Plants (In Water) |
Pioneer species like phytoplankton are replaced by rooted-submerged plants, followed by rooted-floating angiosperms, reed-swamps, marshes, and finally trees, resulting in a climax forest as the water body becomes land. |
| Rate of Succession |
Primary succession is a slow process, taking thousands of years to reach a climax community. Secondary succession is faster due to the presence of soil. |
| End Point of Succession |
Regardless of whether succession occurs on land or in water, the end point of the process is a stable mesic climax community. |
