Biology · Ch 14 — Ecosystems and Energy Flow
Succession of Plants
Succession of Plants
Based on the nature of the habitat in which it occurs, plant succession is termed hydrarch (or hydrosere) when it takes place in wet or wetland areas, and xerarch (or xerosere) when it takes place in dry areas. Hydrarch succession progresses from hydric (very wet) conditions toward mesic (medium-moisture) conditions, while xerarch succession progresses from xeric (very dry) conditions toward the same mesic end-point — so that both pathways, despite starting from opposite extremes, converge on the same kind of intermediate, balanced climax condition.
The species that first invade a completely bare area are called pioneer species. On bare rock, primary succession typically begins with crustose lichens, which are able to secrete acids that dissolve rock, helping to weather it and begin soil formation; these pave the way for bryophytes and mosses, which can take hold in the small amount of soil that has accumulated. Over time these are succeeded by herbaceous plants, and after several further stages a stable climax forest community is finally established, one that persists as long as the surrounding environment stays unchanged. …
What this figure shows. A sequence of stages showing how plant communities develop on bare, dry rock over time, moving from pioneer to climax. It begins with bare rock colonised by lichens, followed by a stage of small annual plants growing alongside the lichens. Next come perennial herbs and grasses, then a stage of grasses, shrubs and shade-intolerant trees as woody vegetation establishes. The sequence culminates in shade-tolerant trees forming a stable climax community. The diagram groups the early lichen and annual-plant stages as pioneer stages, the herb/grass/shrub stages as intermediate stages, and the final tree-dominated stage as the climax community, showing succ …
What this figure shows. A seven-step sequence, numbered 1 to 7, showing how a water body is gradually converted toward land-based climax forest over time. It begins with free-floating phytoplankton as the pioneer stage, followed by submerged rooted plants (such as Hydrilla), then a stage of submerged and free-floating plants together, rooted-floating angiosperms (such as Lotus) and free-floating plants (such as Pistia), a reed-swamp stage (such as Typha), a marsh-meadow stage (such as Cyperus), and a scrub stage (such as Alnus), finally reaching a climax forest (such as Quercus). Each stage adds sediment and organic matter that gradually shallows the water body, allowing the next, more land-adapted community to take hold, illustratin …
What this figure shows. An eight-step sequence showing a forest recovering after a severe fire. It begins with an established forest, which is struck by a severe forest fire leading to total nudation (bareness) of the forest land. Terrestrial plants then begin recolonising the burnt ground, followed by a stage of soil formation together with herbs, then shrubs establishing as a woodland stage develops, and finally the area returns to a forest stage. Because soil and some seed sources already exist at the site — unlike in primary succession on bare rock — this recovery proceeds noticeably faster, tracing the community's retu …