Succession in Plant Communities and Soils
Succession is a relatively predictable process of change that occurs in plant communities and soils. It is an important concept when managing native plant communities for wildlife, livestock grazing, timber production or other goals. Plant communities are not static. They change in response to disturbances such as tillage, burning, mowing, grazing and herbicide treatments. Just as importantly, they change with the absence of disturbances (rest). Understanding these changes lets managers direct or allow change to facilitate their goals.
An example of succession is the progressive change that occurs in a fallow field when it is rested for a long period of time (see figure). Initially, bare tilled soil becomes dominated by annual forbs and grasses. With time, perennial grasses and forbs begin to dominate the site. With more time, especially in areas with more than 30 inches of rainfall, shrubs and small trees become common or abundant on the site. With additional time, many sites continue to evolve until they become forests. With even more time, especially in riparian* sites and higher rainfall areas, species composition of the forest continues to change until a climax plant community develops.
Disturbances generally move succession backward toward simpler, earlier stages. Rest generally moves succession forward toward more complex, later stages. More advanced stages of prairie succession usually provide more forage and support more cattle, but appropriate rest is necessary to maintain this productivity when prairie is grazed.
Plant species composition of the various stages depends upon previous plant communities on a site, soil type, rainfall, climate and disturbances that occur. People who pay attention to and study plant ecology in a particular region can learn to understand and predict the changes.
Following are some examples of managing succession to accomplish goals:
Rest can be used to develop additional woody cover for wildlife, livestock or a windbreak. It is usually easier, more successful, faster and less costly to allow natural succession to develop woody cover than by planting woody seedlings when a site has a tendency to grow woody plants. Sites with this tendency are ones that previously grew timber or brush at some point in their history or those where current managers have to control brush or woody sprouts to prevent woody plants from growing in open areas.
Periodic prescribed fire is commonly used to set back succession to prevent woody plants, especially eastern red cedar, from dominating open areas. Fire also tends to encourage the growth of herbaceous legumes during the growing season immediately following a fire. Several of these legumes are very desirable for wildlife and cattle.
Properly timed tillage or heavy grazing can be used to increase mourning dove food and attract mourning dove when plant species such as woolly croton or common sunflower are present or have grown on a site in the past.
There are many examples of understanding and allowing nature to accomplish desired goals. A range or wildlife consultant should be able to help you learn how to work with nature to accomplish your goals.
*Riparian sites are areas adjacent to streams or impoundments with distinct soils and plant communities that are influenced or created by occasional flooding or shallow ground water.