Ecosystem Types: Part 1 Ecological Succession Patterns “To do science is to search for repeated patterns, not simply to accumulate facts, and to do the science of geographical ecology is to search for patterns of plant and animal life that can be put on a map.” - Robert H. MacArthur

Ecological Succession = a gradual change in the species composition of an area (change in community members) over time 2 Types of Ecological Succession: 1) Primary: starts with no soil or sediment Ex. rock exposed by glaciers, cooled lava, new pond 2) Secondary: soil is present Ex. Abandoned corn field, mine or logging site

Which type? Why? Heavily Polluted Stream? Abandoned Parking Lot?

Primary Succession First species to arrive = Pioneers = lichens, then moss Lichen (sounds like “liken”) = mutualistic combo. algae (makes food) + fungus ( structure) = lichen

Lichens and Moss at work

Primary Succession Lichen can grow on bare rock, produce acids to break down the rock and begin soil creation Mosses can grow with minimal soil, trap dust and detritus to add to new soil Mosses and Lichens build a thin soil for next stage

Primary Succession Stage 2: Smaller plants take root Each stage facilitates the next by adding detritus to the soil, accumulating dust and retaining moisture The stages proceed toward a Climax Community Each of the following increase as succession progresses toward the climax: 1.Rate of decomposition & nutrient cycling 2.Soil richness & depth 3.Species diversity 4.Specialized niches

Primary Succession

Secondary Succession in Ohio Begins with a disturbed site = soil / sediment present Pioneers on a disturbed site are annual grasses and weeds (annual = live one year, leave some seeds and die) Disturbed site is generally replaced in 1-2 years by an “Old Field” community – perennial grasses and weeds (perennial = individuals can over-winter and regrow the next year)

Secondary Succession in Ohio “Old Field” is replaced in 5-10 years by scrub/shrub stage = perennial shrubs, brambles Shrub Scrub is replaced by Immature Forest Shade-intolerant trees Climax Community is a Mature Forest Shade-tolerant trees

Complete your secondary succession diagram! Shade Intolerant Trees Shade Tolerant Trees

Some characteristics of old growth (mature) forest 1) Lots of very large trees and saplings, few middle sized trees 2) Lots of large, downed logs in various stages of decomposition 3) More open understory 4) Canopy 80’-150’ high 5) Pit & mound topo created by upturned root wads of large trees 6) Canopy viewed from above shows varying heights of trees with scattered dead snags

How should forests be managed? Mohican State Forest is 4500 acres of mostly mature forest near Mansfield, OH. It was one of the state’s largest mature forests If you were in charge of managing Mohican State Forest, what rules or guidelines would you apply?

How should forests be managed? Traditional of Succession and Habitat Management: Succession = An unstoppable process that always concludes in a predictable Climax Community Plants in late stages should completely out-compete previous species The biggest enemies of Healthy forests are logging and forest fires

Intermediate Disturbance Hypothesis Use models to test our traditional views of forest management P. 99 in binder – experiment! Complete the worksheet as a guide and record of what you did

Not always the same story… New View of Succession: Disturbances are common Ecosystems are generally a patchwork of various stages of succession Tolerance – Trees do not completely out-compete plants from earlier stages A new disturbance allows the early stage plants to restart the process in that area Ex – Large tree falls down – small patch of succession opens

Role of fire in succession Small, periodic fires are sometimes necessary for maintaining dynamic ecosystems and preventing Climax Communities Prairies & Savanna Pine forests in SE US, Jack Pine Forests in Northern US Small fires also aid in decomposition Small, periodic fires prevent the big catastrophic fire

Yellowstone prior to 1988 Fire

Yellowstone After 1988 Fire

Yellowstone before and after big fire of 1988

Using prescribed burns… prescribed burn for prairies purpose of controlled burning of forest managing private forest with burn

What is Inhibition? The opposite of tolerance…. Plants from earlier stages release toxins into the soil to prevent other plants from growing near them Ex. – black walnut trees (shade intolerant) Inhibition can slow or halt succession