Selective Herbicide Use Supports Restoration of Natural Ecosystem

A project at the Salt Lick Rehabilitation Site in Hells Canyon, south of Lewiston, Idaho, has demonstrated how herbicide use can be greatly reduced or discontinued once desirable vegetation stands have re-established. 

Prior to BLM acquisition the area had previously experienced high-intensity use as winter feeding grounds and livestock pasture, leaving a lack of desirable plant cover and in turn, allowing scotch thistle, fiddleneck, tumble mustard and other noxious weeds to invade.  A travel corridor running through the site allowed weeds to be spread by passing vehicles. 

The plant community consisted mainly of annuals that could not compete with the weeds.  Herbicides used preventatively to keep travelways clear had to be re-applied on a yearly basis.  Establishing desirable, competitive perennials that could eventually beat back the weeds on their own would not only restore the site's natural ecology but could also reduce the need for repeated herbicide use.  Site managers decided to spot-treat the weeds in support of a fall seeding of perennial grasses.

In late 1998, six acres were spot-treated with herbicide prior to re-seeding.  A second round of spot treatments the following spring removed competition for the sprouting perennials.  As re-seeded species subsequently grew and matured in the stand, fewer acres required herbicide treatment.  By 2006, there was an 87 percent reduction in herbicide use at the project site.

At left is a photo taken in the spring of 1999, after the re-seeding and second spot treatment. 
Thistle is especially evident.

Immediately prior to BLM acquisition, the area was used primarily for livestock
grazing.  Pre-settlement, wildlife used the area for feeding.  Disturbed vegetation became vulnerable
to invasive species, whose seeds were spread by livestock and vehicular
traffic.

 

This photo shows the same site in 2003.

Once a stand of desirable vegetation is re-established, the need for herbicides is greatly reduced or even eliminated in favor of other, non-chemical means of control.

"Returning the site to a perennial ecological system has shown numerous other benefits,"
says Lynn Danly, BLM Natural Resource Specialist. "The perennials stay green longer, reducing
early season fire danger. They also are not as flammable when they dry out in late summer,
reducing the chance for a passing vehicle to cause a fire. Wildlife — big game species as well
as upland game and non-game — now use the area more because the plants stay green longer
and also green up in the fall providing fresh forage."

BLM Natural Resource Specialist Lynn Danly says now that the site has been transformed from into an ecosystem that more closely resembles cycles that are natural for the area, the next step will be to remove some non-native grasses introduced in the intermediate re-seeding and replace them with native grasses and forbs.  "The site we were faced with at the beginning was so far removed from what was there originally, we could not have successfully leaped back to a native plant system without this intermediate step."