Succession. Ecological Succession Natural ecological restoration –Primary succession – gradual...
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Transcript of Succession. Ecological Succession Natural ecological restoration –Primary succession – gradual...
Succession
Ecological Succession
• Natural ecological restoration– Primary succession – gradual
establishment of biotic communities in lifeless areas where there is no soil or sediment
– Secondary succession – series of communities with different species develop in places containing only soil or bottom sediment
Primary Succession
• In the beginning…– No soil = no
nutrients– Over time rock
weathers
Hundreds and thousands of years later…
Primary Succession
• Early pioneer plant species– Species arrive and
attach themselves to inhospitable patches of weathered rock• Lichens, mosses
– Help form soil by trapping wind-blown soil particles and detritus• Add waste and dead
bodiesHundreds and thousands of years later…
Primary Succession
• Mid-successional plant species– Soil becomes deep
and fertile enough to hold moisture
– Supports the growth of herbs, grasses, and low shrubs
– Creates shade which causes mosses and lichens to die
– Trees replace grasses and shrubs
Primary Succession
• Late successional plant species– Species that can
tolerate shade– Bare rock ultimately
becomes a complex forest
Aquatic Primary Succession
• Newly created small pond• Influx of nutrients via runoff
Secondary Succession
• Some soil remains in a terrestrial system or sediment in an aquatic system
• Ecosystem has been– Disturbed– Removed– Destroyed
Secondary Succession
• New vegetation can germinate usually within a few weeks – Seeds already in
the soil or imported by wind, birds, and other animals
• Climax community – stability
Similarities• Primary and secondary succession– Tend to increase biodiversity– Increase species richness and interactions
among species
• Primary and secondary succession can be interrupted by– Fires– Hurricanes– Clear-cutting of forests– Plowing of grasslands– Invasion by nonnative species
Species Replacement
• Facilitation – one set of species makes an area suitable for species with different niche requirements– Less suitable for itself (mosses and lichens)
• Inhibition – some early species hinder the establishment and growth of other species– Pine needles make soil acidic
• Tolerance – late succession plants are largely unaffected by plants at earlier stages of succession
Succession Doesn’t Follow a
Predictable Path• Traditional view – Balance of nature and a climax
community
• Current view – Ever-changing mosaic of patches of
vegetation–Mature late-successional ecosystems • State of continual disturbance and change
Living Systems Are Sustained through Constant Change
• Inertia, persistence– Ability of a living system to survive
moderate disturbances
• Resilience – Ability of a living system to be restored
through secondary succession after a moderate disturbance
• Tipping point – Any additional stress can cause the system
to change in an abrupt and usually irreversible way that often involves collapse