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Succession Saves Time and Money

Let's examine what this word means to roadside environments. Succession is the process of vegetation change overtime. It begins with bare soil and what plants are able to occupy that space first. Before settlement, bare soils were caused by wind, flood, fire, and other natural disturbances. Over time most soils reach a vegetated state that is stable, predictable, and practical for roadside management.

Then came road-building, important to our development as a nation. When we constructed roads, we opened up soils to a new cycle of succession. The first seeds to pioneer into these disturbed soils came from the seed bank of the soils themselves, as well as adjacent lands which had not been greatly disturbed. Thus the first plants into a construction site were native to the area. As a result, some of our oldest roads, now are refuges for remnants of regional plant communities, even endangered species.

Centuries later, we can no longer disturb soils and expect native plants to fill the open niches. Due to human disturbances and inadvertant plant introductions, more competitive and invasive plants are poised to occupy bare soils - the bare soils vegation managers open up through blading, mowing, spraying, and other maintenance activities. Yes, our own actions often unintentionally encourage the spread of invasive plants or weeds. Because we can often predict those consequences, we bare responsibility to make maintenance and management decisions carefully.

The good news is that we can actually work with natural succession to minimize maintenance costs, and reduce management efforts! Inventorying what vegetation exists and where, can help predict what problems and opportunities will arise. We can plan accordingly and estimate budgets more accurately. For example: if we are doing a pavement shoulder addition in the Piedmont of Georgia, our inventory will tell us that the existence and threat of kudzu is great on the project. We will save time and effort if we eradicate the plant long before the project begins; seed native grasses and forbs characteristic of the region into the site after construction, and plan to monitor and spot spray for some years after the project.

On the other hand, if native remnants are about to be disturbed by the project, seed collection and plant selvage could be part of the answer. Bottom line, we should pursue maintenance methods that disturb the soils as little as possible, or be prepared for the predictable weeds. Aiming at stable plant associations along the roadside that are consistent with our safety goals is an objective that will reduce crew effort and cost over time. In other words, managing roadsides for early-successional grasslands avoids costly brushing, hazard tree removal, and crashes. Use of grasslands is ecologically safe, economically smart, and safety wise!

Succession in Forested Areas

In forested regions, where forests are the stable plant community, we can predict the time it takes for vegetation to cover bare soils and reach a forested state. Based on this scientific insight, we might be able to reduce our roadside mowing in rural areas to no more than once every five years. Basic safety mowing only would greatly reduce the annual budget cost!

Three sketches demonstrate succession in New Jersey that was monitored for 50 years to learn how an open field in the Eastern deciduous forest changes over time, much in the way an herbaceous right-of-way will change if left unmowed. The study implies that mowing once every 4-5 years would be enough to discourage forest invasion into the roadside recovery zone. (Robichaud Collins and Anderson, 1994).

chart of years 3, 6 and 12 of succession

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This page last modified on August 4, 2004

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United States Department of Transportation - Federal Highway Administration