Succession Ecological Succession Natural ecological restoration Primary succession

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 bodies Hundreds 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