Tom's Blog

Wednesday, April 18, 2018

Costs for restoration of savanna and prairie remnants

Restoration of oak savannas and prairie remnants is usually a complicated and expensive process, but real data on costs are hard to find. From time to time during 20 years of restoration work at Pleasant Valley Conservancy I was able to record times involved in various tasks. Since most work involved multiple workers, I have converted the time sheets into person/hours. Areas restored during the same activities were measured either by walking the periphery with a Garmin GPS or by GIS using air photos with ArcMap.

The various work activities shown in the summary table need explaining. Most of the work considered in this post involves removal of woody vegetation, both trees and shrubs. Removal of herbaceous plants, weeding, is a different activity and is not presented. Photos are added to present the context of the restoration activities.

The procedures discussed here have been used on oak savanna or prairie remnants that are “restorable”. That means that they once were “good” remnants but had become seriously degraded because of grazing or lack of fire. They still had some native species and retained small remnant areas.

Basal bark herbicide treatment
One of the most efficient ways of eliminating woody vegetation is basal bark treatment with an oil-soluble herbicide that will penetrate the bark and kill the roots. Since basal bark treatment can be done any time of the year, it is often done in the winter when many other restoration tasks cannot be done. At PVC, 100 foot swaths were marked with flagging tape and workers move along these swaths, treating any target species. The treated plants died during the next growing season and the dead plants were left in place. In a year or two they fell over and slowly decomposed. This works best for scattered plants.

Cut and treat
Denser populations of brush such as honeysuckle, buckthorn, or brambles, were cut with motorized brush cutters, followed by cut stem treatment with herbicide. Depending on the species cut, glyphosate or triclopyr was used to treat the cut stems. This procedure involved a team of people, one operating the brush cutter and three or four following with herbicide spray bottles. This procedure was used primarily on infestations of smaller shrub heights (2-4 feet), and the cut brush was just left on the ground to burn up at the next fire.

Tree work
Many restorations involved the removal of invasive trees such as walnut, elm, cherry, and box elder as well as brush. Often these trees were 10-20 inches in diameter and an experienced crew (contractor) was needed. If the trees were smaller, so that removal was less technical, an experienced chain saw operator could work with a group of less experienced workers. Tree work requires much more time because brush piles must be built, and the cut logs must be removed from the site.

Foliar spray (reprouts after a burn)
A very efficient method of removing brush is to burn the unit (either spring or fall). A properly conducted burn will top-kill the shrubs. In late spring or early summer new shoots will appear and can be sprayed with an herbicide such as aqueous triclopyr. This is a very effective procedure and is less time-consuming than others. There is no cut wood to deal with, and the sprayed plant is usually eradicated.

Foliar spray (fall)
In the fall, buckthorn and honeysuckle retain their green leaves long after all the native vegetation has senesced. Although the timing is variable from year to year, these plants can usually be killed by a foliar spray such as glyphosate or triclopyr. Remember: if it is green, it will be killed. Senesced plants (brown) will not take up herbicide. Glyphosate is preferred because there is no soil residue.

Examples of the techniques  used are given at the end of this post.

The Table
The table is arranged in two ways
  •      By task
  •        By hours per acre from low to high

I used hours per acre to express costs because hourly rates vary widely,. However, I have added a column assuming $25 per hour.

Wooded road bank
Basal bark
Mixed brush
Oak woodland (whole North Woods)
Basal bark
Large buckthorn and honeysuckle
White Oak Savanna (Unit 12A)
Cut and treat
Moderately steep; brambles; honeysuckle; no buckthorn
South slope and basin savanna; 2006
Cut and treat
Mixed small brush; steep terrain
South slope and basin savanna; 2007
Cut and treat
Mixed small brush; steep terrain; snow year
Bur oak open savanna (Unit 11A)
Cut and treat
Brambles and mixed brush
White oak savanna on steep slope
Tree work (contractor)
Many large walnuts to cut
South slope below diagonal trail 1998
Tree work (hourly workers)
Moderate-sized trees and big brush; chipping
Ridge top and basin savanna

Tree work (contractor)
Trees and brush; lots of wood to deal with
East Basin
Tree work (contractor)
Fully closed forest converted to prairie
Bur oak savanna (Unit 8;10)
Foliar spray
Brambles; brush resprouts after spring burn
Bur oak savanna (Unit 10) 2007
Foliar spray
Buckthorn; fall foliar spray
Bur oak savanna (Unit 10) 2008
Foliar spray
Buckthorn; fall foliar spray
East Basin
Foliar spray
Spot spray after clearing and burning

$$ per acre based on $25 hourly rate; other rates are possible, or none, if the work is done by volunteers.

Basal bark is one of the most economical methods of brush control. However, the dead brush is left standing, and one must wait a year or two for the dead stems to disappear. However, it could be used as a preamble to a major tree cutting operation. If it was known that a lot of trees were going to be cut in a unit in a year or two, it would be efficient to basal bark all the woody vegetation. The dead wood could then be used as the base of the brush piles that would be made from the smaller branches of cut trees.

Foliar spray of resprouts after burns is another economical method of brush control. By spraying the resprouts before they get big, one is eradicating the plant and preventing it from getting larger. The principal problem is timing. Not all plants resprout simultaneously, so that it is necessary to canvas each area at least twice, and preferably three times. Also, spraying usually must be done in May when herbaceous weed control is also underway.

Cut and treat on a honeysuckle-infested hillside. One brush cutter and three treaters

Cutting and treating in winter. Light snow is helpful in keeping track of where the brush cutter has been.

Cutting and treating near the Town road makes it easier to deal with the wood.
This is the beginning of the major job to clear the whole South Slope.
Hourly workers were used rather than a contractor

This area had many large trees that had to be cut. Contractor

Bramble resprouts after top-killing from a burn.
This is the ideal stage for foliar spraying

Spraying resprouts. It takes a good eye to locate all the resprouts.
All woody resprouts are sprayed.
A 3-4 person crew is ideal.

Buckthorn green. All the native vegetation has already senesced.
An ideal time for foliar spraying

Four-person crew canvassing a savanna for green buckthorn.
A systematic search of the whole unit is necessary, using marked swaths.


Post a Comment

Subscribe to Post Comments [Atom]

<< Home