Succession and Zonation What is the difference? Succession: How an ecosystem changes in time Zonation: How an ecosystem in changing in space (along an environmental gradient like altitude)

Zonation Every niche has limits, outside of which, the species cannot survive The most important factors that influence these limits (Limiting Factors) Temperature Precipitation Solar Insolation Soil Type Species Interactions Human Activities Alter zonation through road building etc. Kite Diagram

Succession Succession Primary Succession Secondary Succession Bare land doesn’t stay bare for long The change is directional resulting in a natural increase in complexity Primary Succession Occurs on a bare inorganic surface Occurs when new land is created or uncovered Volcanoes River Deltas Sand Dunes Glacial Retreat Secondary Succession When an already established community is suddenly destroyed Fire Flood Humans (agriculture) Occurs on soils that are already developed Results in a quicker version of succession

Succession Changes During Succession Primary Succession Secondary Succession Changes During Succession Size of organisms increases Simple food chains become complex food webs Soil depth/quality increases Biodiversity increases as niche structure develops NPP and GPP rise and then fall

Productivity Changes in Succession Primary Productivity (Varies with time) Low at first (few plants) Rises throughout intermediate stages Levels off during climax stages because respiration rates are starting to equal the rate at which energy is fixed by producers Early Stages Gross productivity is low…but Respiration rates are low too so net productivity is high ***The system is growing*** Later Stages P:R ratio approaches 1

K and R Strategists K-Strategist r-Strategist K is carrying capacity r-Strategist r is biotic potential (exponential) Many species show a mixture

Survivorship Curves Type 1 (Late Loss) Type II (Constant Loss) Typical for K-selected species Most likely to die later in life Type II (Constant Loss) Relatively rare Equal chance of dying at any time Types III (Early Loss) Typical for r-selected species Most mortality occurs in early life stages