Succession - From Sand Dune to Forest

a natural community of plants and animals is dynamic it is continually changing in an orderly and predictable way L Mig the first significant study in America was made of the process of succession as you watch the stages in the succession think about comparable stages in your own Community it's like quite an ordinary forest and so it is but this area wasn't always Forest it was once a Sandy Beach the series of events which reached its climax as this beach Maple Forest is an example of a process of change in nature called ecological succession the process of ecological succession in different forms and at various speeds goes on endlessly throughout the world in the sandune area on the Southeast shores of Lake Michigan can be observed a classic iCal example of one variety the principles involved in this example can be applied to many other situations this succession story sand is brought in by currents from the lake Drift from the surface of the lake is washed ashore the middle Beach is formed the Pioneer grasses get a tow hold then come the cotton woods and in succession the Pines The Oaks and finally in this instance the climax Forest the beach Maples much of the sand in the dunes of the Southern Lake Michigan area has been eroded from the western shore of the lake the sand is carried by currents across the lake to the Dune area on any sunny day especially after a summer storm and if the winds are favorable we can clearly see the drift near the water's edge drift is made up of anything that can be washed or blown ashore animals such as these readily decompose flesh flies lay eggs in the dead carcasses the larv that hatch will feed upon the Flesh in the drift there is evidence of a variety of cycles of Life Death and Decay things that die and Decay later form what is called humus when humus mingles with sand the slow process of biological soil making is underway relationships between living things begin to be established the spotted Sandpiper feeds on maggots that hatch from the eggs of the flesh flies beyond the reach of the Waves lies the middle Beach dry and desert-like only such hearty creatures as The Ant and the tiger beetle can survive the Heat and aridity Pioneer types of vegetation begin to gain a foothold many decades may pass before enough organic matter or humus is mixed with the sand to support even this sparse vegetation only the best adapted plants have roots that will hold in the sand Against the Wind their stems and leaves slow the blowing sand the first small Dunes are forming the for Dunes such creatures as the Grasshopper And The Lizard find here food and some protection from the elements Hardy ants Aid in soil building the color of the wolf spider not only reflects the light and heat but makes it less visible to its intended prey and to its enemies as roots leaves and animals Decay humus accumulates and soil building continues when there is enough moisture and enough soil to hold and nourish larger Roots Cottonwood seeds May develop into seedlings this is the beginning of the Cottonwood stage of the succession other plants also appear the shade and the humus help preserve the moisture in the soil the plants are helping to create a new climate beneath their boughs this new climate makes possible different forms of life in a still Sandy spot a mutillid was more commonly known as a velvet ant may find a home nearby a predator member of the Cottonwood Community a species of tiger beetle has made a hapless fly his prey the ant lion builds traps into which insects may fall this is a digger wasp each stage of an ecological succession is characterized by certain animals as well as by certain plants they are called index plants and animals such an index animal of the Cottonwood stage is the digger wasp in this unusual scene we see a digger wasp actually digging a hole in the sand in which to lay its eggs and bury its prey for its lyy to eat the things they store in their Burrows contribute to the accumulation of debris below the surface this is an important step in soil building the six lined skink commonly called a lizard has caught a grasshopper and darts for the protection of a wild cherry tree one of the characteristic plants of the Cottonwood stage the shade of the cotton Woods has conserved enough moisture and enough soil has now been formed so that the pine seedlings can take root this area is in transition from the Cottonwood to the Pine stage there is a better covering of humus forming and moist You're Building leaves and thatch on the floor the plant and animal community is becoming more complex as we go farther and farther from the lake this community will support some of the larger mammals such as the deer it will also support other animals that are dependent upon flowers and leaves the Bumblebee the caterpillar as the pine trees made their appearance among the cottonwoods so now in turn the Pines die and in succession are replaced by The Oaks the oak seedlings are at first protected by the pines and are nurtured in the soil produced in part by the pines as the transition proceeds The Oaks May entirely replace the Pines the protecting shade of the Oaks helps provide an environment suitable for a host of new plants and animals which through the years have become adapted to more soil moisture higher relative humidity and more humus a fallen log provides a succession story when a tree dies a succession of events begins leading an evitably to the return of the tree to the soil and to the atmosphere from which it came many creatures Aid in the destruction of the log earthworms not only help destroy logs but also take over some of the earth digging activities which Digger wasps performed in earlier stages of the succession centipedes do not feed upon the log but Prey Upon other creatures thereby helping to maintain a balance in nature the log provides a habitat for many cutting boring and chewing creatures which eventually completely destroy their habitat and the log again returns to the soil The increased humus and moisture make possible an increase in the ant population the ant is adapted to a wide variety of environments the oak canopy above provides shade in which fungus plants Thrive the poyra snail has become adapted to a damp environment it moves slowly but is protected by its shell there are many varieties of beetles in the Oak Forest here for example is a lysd beetle a close relative of the Firefly the carabid is another of the many kinds of beetles of the Oak Forest the litter and debris of the oak forest floor provide places where certain reptiles such as the carnivorous Decay snake can search for prey principally earthworms and daddy long legs when he can find them another carnivore is the fox snake it feeds principally on rodents the skunk always moves in a leisurely manner the Oak Forest provides food and shelter for a variety of tree dwellers there are the mammals such as the gray squirrel which often feeds upon the floor even though it nests in the trees another m is the opossum these animals exist in the Oak Forest which is but a short distance from the desert-like middle Beach an earlier stage of the succession the shade and humidity increase as the growth of the trees becomes more dense in time the Oaks die and as conditions become right The Oaks may be replaced in succession by the beaches and Maples the trees in the beach Maple Forest grow tall and straight the forest floor gets scant light so very little underbrush can survive beneath the trees consequently insects dependent upon the underbrush for shelter and breeding places are scarce with decreased wind movement the moisture content of the soil increases and most characteristic is the increase of the true forms of the forest floor those things which must have shade and considerable moisture to survive the millipede is common here it is an index animal of the beach Maple Forest another index animal is this redback salamander which finds the beach Maple Forest an ideal place to lay its eggs the poyra snail is especially abundant in the beach Maple Forest it feeds principally upon molds and vegetation the snail and box turtle are slow movers their shells help protect them from their faster moving predators in the climate of this area the beach and map Community once established continues to reproduce indefinitely hence it is called a climax community it continues to remain essentially the same if nothing occurs to upset it but upset it can be a change in direction of the prevailing wind a heavy rainstorm fire or man's lumbering May sometimes start an erosion cycle in the forest forming what is known as a blowout a blowout such as as this can take place anywhere in a forest with a sand base this area has become desert-like again even though it is just a short distance from the dark humid forest floor a blowout area over a period of many years will again go through an ecological succession there will be the Pioneer plants that hold the shifting sand then cotton Woods will usually appear these again may be followed by Pines Pines in turn may give way to Oaks and the Oaks after many many years again may be succeeded by the beaches and sugar Maples the typical climax forest for this area different climates and soils result in different successions compare the classic story of sand dun's succession with that in your own community