The Climax Forest Process

Getting to the Climax of Forest Succession

Canadian forest with pedestrian bridge
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A plant community that is dominated by trees representing the last stage of natural succession for that specific locality and environmentally should be considered a climax forest. To be a climax forest, trees growing within a particular geographic region should remain essentially unchanged in terms of species composition for as long as the site "remains undisturbed".

Foresters have adopted a practical silvicultural approach when managing large stable communities of climax tree species. They use and name a "climax" forest as the final stage in terms of the stabilization of the major tree species. These conditions are observed on a human timescale and can maintain specific tree species and other plants over hundreds of years.

This definition is honored by some but not by all. In contrast, speculative ecologists conclude that there can never be a climax forest. Their claim is because cyclical disturbance (both natural and human-caused) will always be a constant in North American forests.

A climax community by a more accepted definition is a relatively stable and undisturbed plant community that has evolved through major stages and adapted to its environment. A climax species is a plant species that will remain essentially unchanged in terms of species composition for as long as the site remains undisturbed.

How Forests Are Created and Mature

Forests are always in some evolving process that takes place in several major defined steps or stages and until completion and each stage is called a "sere". A sere can also be called a seral community and are the multiple stages found during forest succession in a forest ecosystem advancing towards its climax community. In many cases, more than one seral stage evolves until climax conditions are attained

The major phases of forest succession in a post-glacial, temperate world leading to climax follow a certain mechanical pattern of development.

Ecologists have created terms and most agree that initial forest establishment starts from some disturbance that creates a bare site which they call Nudism. With the introduction of living regenerative plant material to that bare site from certain sexual and asexual processes and along with seed transportation, succession begins with the process of plant movement called Migration.

This migrating of plant-produced genetic material toward more advantageous living and growing conditions that then encourage the establishment of vegetative growth which is called Ecesis. In this state of expanding plant growth, pioneer or early seeding plant species pave the way toward the succession of more stable plants and trees.

So, plants (including trees) that make a desperate attempt to quickly capture space, light, and nutrients are now in Competition with all other vegetative organisms that demand the same elements for life. This plant community then makes a significant change from the effects of competition and is called the Reaction stage in a forest ecosystem. This reaction to competition slowly but surely creates a calming symbiosis of existing species in a long path toward stabilization.

The long-term and final development of a forest climax community is called Stabilization and creates a forest that lasts until the next inevitable disturbance or change in the climate.

100,000 Year Cycles Change Climax Tree Species

A plausible theory of advancing and retreating ice suggests that the climax forest of today will not be the stable forests of the far future. So even the climax oaks and beeches of today may be transient on the geological timescale in the northern latitudes.

In tropical latitudes, forests seem to withstand global cooling to the point where they may vastly expand and contract. It is thought that this changing of rainforests creates "patches" which encourages astonishingly diverse assemblages of the kind we see in the Amazon.

Colin Tudge digs deeply into this theory and other fascinating tree facts in his book called The Tree: A Natural History of What Trees Are, How They Live, and Why They Matter.