Succession

 

Succession

For instance, in Ohio, a simple description of a sere that would develop on an abandoned field might be:

grass -> shrubs -> trees -> oak-hickory forest

In this sere, the grass is the pioneer community and the oak-hickory forest is the climax community. Each step in the sere (grass, shrubs, trees, oak-hickory forest) is individually known as a seral stage. There are two main types of succession:

1. Primary succession

2. Secondary succession

General trends in succession:

Early seral stages are highly productive but require large inputs of nutrients and also tend to lose nutrients. Biomass increases, but there is low productivity and fluctuations in biomass are common. These seral stages are dominated by "weedy" or "r-adapted" species which reproduce quickly, but often die young. Most of their energy goes into reproduction. There are relatively few species in early seral stages.

Climax seral stages are much more complex, with many species. They create a favorable environment for many species. Biomass does not fluctuate, and decomposition rates are roughly equivalent to new production. Nutrients are cycled efficiently, and rarely leave the ecosystem. Individual organisms are longer-lived, since they invest more resources in themselves and less in producing offspring.

Locally, a recently cleared field is an example of an early seral stage. It is colonized by grasses and other plants that produce many seeds, such as many annuals. These plants may live only one year, set seed, then die. The organisms in the field will not be able to cycle all of the nutrients, and many nutrients will run off with rainfall. On the other hand, the climax forest is characterized by trees, which are long-lived. There are many species, and each provides living space and food resources for other plants and a host of animals. Decomposing materials are recycled; few escape though the waters of the forest streams.

If one farms in a rain forest, the community is moved from a climax community to an artificial community which resembles an early seral stage. The farm field will lose a lot of nutrients, something that tropical soils do not have in abundance. The land will be useless for farming in a few years.

This table summarizes the differences between pioneer and climax communities:


 Pioneer Community                Climax Community                          

 Harsh environment                favorable environment                     

 biomass increasing               biomass stable                            

 energy consumption inefficient   energy consumption efficient              

 some nutrient loss               nutrient cycling                          

 low species diversity            high species diversity                    

 fluctuations common              fluctuations less common                  

 r - adapted                      K - adapted                               

Succession Case Studies

Primary Succession:  These photos show primary succession, the development of a community where none was before.  The images were taken at Acadia National Park in Maine.  Here, you can see a whole sere in one view; first to appear on the bare rock are lichens and algae.  These secrete acids which begin to extract nutrients from the rock and which form tiny cracks which are widened by freezing and thawing.  As the cracks widen they trap enough organic material and moisture for mosses to take hold.  Larger cracks have enough soil to support grasses and small shrubs.  The largest cracks come together to form small basins where trees can take root, although the tree in the photo below didn't make it too long; perhaps a drought exhausted the water in the small basin.  However, in the background the climax coniferous forest is visible where enough soil has accumulated to support the trees.

 

In the photos at the right and below, a similar successional story takes root on the west coast at Mt. Rainier in Washington.  Once again, the lichens are the first to appear (although they are hard to spot here).  More obvious are the mosses, grasses and small plants like flowers.  Each stage accumulates soil and organic material that facilitates the growth of the next stage.  Once again, on this mountainside, the coniferous forest is the climax community.

Secondary Succession - Lake Succession:  In the image above, a former bog in Maine has almost completely filled.  A former lake, formed originally when a large piece of ice broke off a retreating glacier, is now well along the transition to dry land.  These kettlehole lakes often support an extensive mat of floating vegetation.  The bog in the picture above left (from Minnesota) is a good example.  You can still see open water, but a mat of floating vegetation (the material between the foreground and the open water) has developed.  Another nearby Minnesota bog (left) is completely covered with vegetation, although there may be water under that vegetation.  Much of the vegetation is comprised of sphagnum moss (left); the moss secretes acids which prevent decomposition from taking place in the bog.  This accelerates the accumulation of organic material in the bog (since it can't decay), and the lake begins to fill in.

In the 4 images below you can see a different bog.  This is Singer Lake Bog in Ohio.  The floating mat there is surrounded by a "moat" of open water about 10 feet deep; the only way to get to it is by swimming or use of a fortuitous treefall.  The floating mat supports not only the sphagnum, but a host of other plants, including small trees which wobble as you make waves walking on the mat 30 feet away.

Dune Succession:  In the picture above center, a sand spit extends out into Lake Erie from the southern tip of Pelee Island in Canada.  Tossed by storms, it is unlikely that much of a plant community will ever develop there.  On the southern shore of Lake Michigan, at the Indiana Dunes, however, there is a different story.  Here, sand washed up onto the beach is piled by the wind into tall dunes which slowly move away from the lake (above).  If plants can get root, they slow the wind, encourage it to drop its sand, and stabilize the dune, stopping its motion.  On the other hand, foot traffic down to the beach my kill plants, and without them there the dune begins to move again.  The picture to the right shows such an event; the low spot between the two vegetated areas has been blown over the back of the dune.  The pictures below show what is happening on the back side of the dune; as the dune moves away from the lake it sweeps over trees and kills them.  Even here, however, plants like the Virginia Creeper (below right) struggle to stabilize the sand.  The vines - getting their water from far down the slope - grow over the surface of the sand.  If they get buried they simply draw on their downslope roots for more water and grow back up to the surface.  There the leaves shade and cool the soil, and the buried plant material enriches the organic content of the sand.

Left: A beach dune in Costa Rica being stabilized by plants.

Right:  The back side of the dune shown above.  In Indiana, the climax community would be temperate deciduous forest, here in Costa Rica it is tropical dry forest.

Mangroves help stabilize soils on tropical coasts.  The dense tangle of aerial roots of the red mangrove (left) cushions the impact of waves and protects the shoreline behind the mangroves from the full source of storms.   Black Mangrove roots (in the foreground of the image to lower left, with red mangrove roots behind the trunk of the black mangrove tree) send up pneumatophores to supply the roots with oxygen (necessary in the anoxic soils around the mangroves).  These pneumatophores, however, also contribute to holding the soil in place.

 Thus protected, the beach communities can continue succession.  If the mangroves and beach communities are destroyed by a major storm then succession will be reset.  The red mangrove seedling, below, if it survives and grows will be a vanguard for the beach community, extending it seaward another 10 meters or so.

More on Mangroves Here

deciduous forest sere

Above, the sere for secondary succession in southeastern Ohio. After removal of the plant community - by fire, farming or (as pictured here) surface mining), the plant communities regrow in a stereotypical fashion or sere. The sere consists of individual seral stages, 6 of which are shown here (experts might delineate the seral stages differently). First, the is bare ground, which quickly (less than a year) gives way to grass and herbs. Shrubs invade the grass and herbs seral stage, and set things up for the 4th seral stage, small trees. The tree community is dominated at first by quick-growing species such as aspens, sassafras and the like; eventually a mature forest ecosystem is reached in the last seral stage (which may take several hundred years to achieve). In most cases, this will be an oak-hickory forest, but if fire is suppressed or absent, beeches and maples may come to predominate.

 

Fire and Succession: Fire plays a complex role in succession.  Usually, a fire stops the progression of succession and sets the stage for new, secondary succession as plants take root and grow in the soil enriched by the mineral ashes of their predecessors.   In some cases, however, fire plays an even more important role.  It maintains the climax community by removing competitors that would otherwise move the climax to a different type of community.

fire

Above: A forest fire burns over the ridge from Flathead Lake in Montana. This was a small fire, about 400 acres, apparently started by some farm equipment, and it was put out by the next morning. It would have been embarrassing had it spread, as it was in sight of the National Smokejumpers' School. The relationship between humans, fires and succession is complex. Fire is a natural process, but humans are responsible for starting (and stopping) fires as well.

 

Two examples of fire and succession are shown here.  The shrubland habitat of southern California is maintained by fire, which eliminates large trees.  The pictures above and to the left show a large fire burning a hillside; any trees that had been growing there would be killed and the shrubs and other plants adapted to fire would spring back quickly and reclaim the habitat.

Below left, an area at the Archbold Biological Station, just a few days after it was burned. The plant in the foreground is a palmetto, after the fire it was able to resprout quickly from the prostrate stalk, which has a thick covering which is able to resist the fire.  The picture below shows an area on the other side of the road which had not burned for a long time, and which is full of small trees such as scrub oaks and scrub hickories.

Animals are often able to avoid fires or survive them in a number of ways.  The ant nest in the photo above was in an area that had burned the day before.  The ants quickly dug themselves out and moved their pupae and young (right) to a new nest about 10 feet away (below right).

In areas not adapted to fire (below), fire resets the successional clock.  The area on the right in this image burned, killing all the shrubs and tree saplings.  The grass will sprout back quickly in the spring, but that side of the small creek will end up reaching the last stages of succession -here a deciduous forest - perhaps 5-10 years later than the unburned area.  Of course, since it will take about 100 years or more to have fairly mature trees on either side, the 5-10 year difference may not be apparent a century from now.

 

In the drought year of 1988, huge fires swept through Yellowstone National Park (above and left).  After years of fire suppression in the park, the forest floor was loaded with potential fuel, and the resulting fire burned hotter than it would have if more frequent, patchy fires had been allowed to take their natural course.  The pictures above were taken in 1999; 11 years after the fires.  The slow regrowth is in part due to the cold temperatures there; average annual temperature in Yellowstone is only about 1° C.  To the left, a pine sapling struggles to regrow after the fire.  In Yellowstone, the fires moved the community away from its climax and set secondary succession into motion.

fire comparison

Above: Further comparison of Yellowstone 11 and 25 years after the 1988 fires. The picture to the left shows how the forest appeared 11 years post-fire; the image to the right 25 years post fire. More of the standing trees left over from the fire have fallen, and the new growth is about 3x as high.

Right: 25 years after the 1988 Yellowstone fire, this area has regenerated to the point where it has 20 foot tall trees. A windstorm in this area also blew down most of the remaining trees killed by the fire. Differences in slope, north vs. south exposure, and differences in elevation all affect the rate at which vegetation recovers after a fire. This is obviously a well-situated site for the pines as compared to the earlier photos where trees were only about 1/2 as tall after 25 years.

 

blowdown

arnica fire

Above and Below: The Arnica fire in Yellowstone occurred in 2009. These pictures from 2013 allow us a glimpse at earlier stages of succession post-fire. In the image above you can see relatively few pine seedlings (below), although other plants are doing well on the ash-enriched soils.

pine seedling

 

Below: an elk herd grazes the ground-level vegetation coming back 4 years after the Arnica fire in Yellowstone. The sudden growth of grasses and other plants on the sunny, enriched post-fire soil can be vital to herbivores like elk, which may find relatively little browse in the shady interior of a mature Ponderosa pine forest.

wapiti (elk)

Bull elk (wapiti)

 

Below: In 2003, large fires burned into Glacier National Park. The Robert fire burned the areas below, stopping only at the shore of Lake MacDonald. The images here show the area 10 years later. Compared to Yellowstone, the area here has a warmer average annual temperature (although Lake MacDonald is hundreds of miles north of Yellowstone Lake, Lake Macdonald is at an elevation of 961 meters while Yellowstone Lake is much higher at 2,376 meters, and it is cooler at higher elevations).

Lake MacDonald Fire

Rober Fire Glacier National Park

succession

The image above shows a group of pines in the middle of a glade in Glacier national Park The living pines were photographed in 1996. The gray area is from an image taken in 2013 after the Robert fire. Below, the scene as it appeared in 2013 10 years after the 2003 Robert fire. Many of the trees alive in 1996 have been killed, but note a few new trees growing to the left of the original trees from the 1996 image. Fire resets and alters succession.

succession

Lake Mary Red Eagle Fire

Another major fire hit Glacier in 2006; this one burned to the edge of Lake Mary on the eastern side of the park. What looks like a snow-covered hillside (above) is actually a mass of dead but still standing pines and other conifers. Below, a closer view of the burned area 7 years after the fire. Aspen seem to be colonizing this slope.

Red Eagle Fire

 

 

 

Below: since the Yellowstone fires of 1988, the National Park Service has adopted more enlightened fire practices. Among these are prescribed burning.  The Park Service actually sets small fires to approximate the frequency of burning that would occur under natural conditions.  This creates smaller, patchier fires that kill only the species least tolerant of fires, and tend to increase overall diversity as burned and unburned areas are in close proximity.  The pictures below are from Theodore Roosevelt National Park (below left) in North Dakota, and Everglades National Park in Florida (below).  The everglades are a fire-dependent ecosystem; spring rains come in the form of thunderstorms and lightning strikes any trees that are growing there.  The resulting fire kills the trees and allows the native sedges like sawgrass to reclaim the landscape.  Here, fire maintains an unstable climax.

Succession on a small scale:  The gopher tortoise builds a large burrow in the sands of the Florida Scrub.  The burrow itself becomes a refuge for a number of animals other than the tortoise; owls, snakes, frogs, crickets and a host of other animals are known to use the burrows.  The spoils on the edge of the burrow (above) are composed of sand dug from the burrow.  This sand often bears nutrients that heavy summer rains had leached underground, out of reach of the roots of most plants.  The spoil pile, then, represents "new" nutrient rich soil, and plants quickly grow there, beginning the process of secondary succession.

Clear cutting:  When forests are clear-cut, secondary succession begins on the deforested plots.  To speed the process, and to ensure that the resulting forest will be the same age and easy to harvest, timber companies usually replant the forest.  This, however, results in a forest of trees which are often genetically very similar, and of course, of the same age.  This creates a patchwork landscape  as you can see in these pictures.  Because these forests do not retain any of the old trees which provide food and nest sites for many animals, they are not very diverse in terms of wildlife either.  Wildlife depends on a diversity of trees which themselves vary in age from saplings to mature and even dead trees.

Below:  The valley you see in the photo below was created by a retreating glacier (it's camera shy and hiding behind the bend in the valley).  Initially, the steep slopes are subject to slides, and not much will be able to grow there.  As the land stabilizes, however, succession will begin to take hold and, if the climate does not cool and allow the glacier to grow again, the forests will cover the slopes.

Old-field Succession:  The abandoned pasture to the left is slowly reverting to forest.  Grasses are gradually replaced by other perennials such as milkweeds, goldenrod, and shrubs.  Next come small trees adapted to this habitat.  These would include sassafras, hawthorns and the like.  Larger trees such as oaks, maples, hickories and eventually beeches will begin to come into the picture, and eventually a mature forest such as the old-growth forest shown in the remaining pictures will come into being after hundreds of years.  Note the diversity of tree sizes in the mature forest.

More pictures of mature temperate deciduous forest.  The images here are from primary forests which probably were never logged.

Succession on a small and natural scale:  When a tree fell in the tropical rainforest at the La Selva Biological Station in Costa Rica the many vines attached to it dragged down additional trees as well.  This opened up a light gap - an opening in the forest canopy where additional light can enter.  This in turn opens the habitat for plants which can grow quickly but which need a lot of light.  Much of the diversity of tropical rainforests is due in part to this phenomenon; small light gaps allow a number of species to grow which would not be able to get enough light under the closed canopy of the mature rainforest (below).

Slash-and-burn agriculturalists in the rainforests utilize this basic strategy; they either exploit natural light gaps to grow their crops or they create a gap by felling trees.  As the canopy closes back in after a few years (and as the soil loses nutrients to the crops and the heavy rains) the farmers move on to a new patch.

In 1980, Mt. St. Helens in Washington erupted, essentially destroying all life in a large blast zone (above right).  Trees were killed (above left) and the ground was covered with ash (left).  In some places, such as the protected side of a knob (below left), while the mature trees were killed the soil was not sterilized as it was in other places.  This meant that seeds could germinate and begin to replace the forest more rapidly than was possible in areas where no seeds survived (below right).

More pictures of the destruction at Mt. St. Helens.

The photo to the left shows a lava flow from Volcán Arenal in Costa Rica.  This lava was deposited during an eruption in 1992, 15 years before the picture was taken.  As you can see, plant life is trying to re-establish itself on the lava flow, which is a very inhospitable environment as it is hot and dry, with little soil.  On the other hand, the soil that is present is rich in nutrients.  Because the existing community and the soil are so thoroughly destroyed by volcanic eruptions the succession that proceeds is called Primary Succession (as opposed to the secondary succession occurring after a forest fire). 

Below Left:  Orchids are actually among the plants best adapted to live in such extreme environments as lava flows.  Below Right:  Two peaks of the Arenal Volcano; the one in the background was active when this image was taken and has little to no vegetation.  The peak in the foreground was active less than 2 years earlier and already has green vegetation on it.  Long growing seasons and plenty of rain help accelerate succession in Costa Rica.

More on Volcán Arenal here!

Arenal Volcano Growth

Above: Growth of the Arenal Volcano from 2005 to 2012

 

Pacaya

Above: In 2009, an expedition from Marietta College visited the active volcano, Pacaya, in Guatemala. New land produced by volcanic activity, including lava flows (below) and cinder and ash falls is then colonized by plants and animals in Primary Succession.

lava flow

Below: The volcano Rincon de la Vieja in Costa Rica is still active. Plant communities are beginning to cover the ash slopes in the process of primary succession.

In the image below, different seral stages are shown from left to right, with bare ground on the left and elfin and moist rainforest towards the right.

Rincon de la Vieja

kipuka

lava succession

 

glacier

Glaciers, such as the one pictured above, are another agent responsible for primary succession.

Glaciers scrape rock bare of any residual plant community, and when they retreat, open up new habitats, such as bare rock, unconsolidated "soil" on the moraines, and even aquatic habitats such as bogs (see above) and cirque lakes.

glacial valleys

Above: glaciers typically scour out U-shaped valleys.

glacial valley

In addition to a u-shaped valley, a glacier typically pushes a mass of material ahead of it. If this material is left in a pile as the glacier retreats, the pile is called a moraine.

Moraines, since they are closer to soil than bare rock, often move through succession much more rapidly than bare rock. In Ohio, extensive moraines from the

continental glaciers about 12,000 years ago stretch from southwest to northeast across the state where they are mined for sand and gravel.

overlord

Above, the Overlord Glacier in British Columbia is retreating. Its moraine is trapping water (arrow) to form a cirque lake.

Below: a small cirque lake and its moraine, both formed by a glacier which has retreated off the left side of the image.

cirque

 

 

   
   
   

Above:  A nurse log in a temperate rainforest shows many of the stages of succession, with mosses and other plants taking roots.  Tree seedlings will also grow here, and eventually the nurse log may give rise to 2 or 3 full-size trees.  

The remaining pictures here show strip-mining in Ohio.  Strip mining completely eliminates the natural community.  Former practices in mining often buried the topsoil under piles of the deeper mineral rock overburden.  This killed any seeds, bacteria, fungi, etc. needed to sustain a healthy community.  Even if the land is returned to its pre-mining contours the resulting mineral soil will be barren, and succession will take a very long time to return to the normal climax community (deciduous forest here).  More modern practices set the topsoil aside separately and return it to the surface where it can support at least some growth.

American Electric Power (AEP) mined extensive areas in southeastern Ohio, much of it using the giant dragline Big Muskie (below).  After reclamation, over 10,000 acres was donated to create a unique conservation facility, The Wilds, which is now home to endangered wildlife from around the world (giraffes).

Updated 10/14/2013

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