Biologists and Vegetation Managers Should Work Together

June 28, 2013
Sometimes it seems like environmental rules and the biologists that implement them were created specifically to prevent vegetation managers from getting their work done.

Sometimes it seems like environmental rules and the biologists that implement them were created specifically to prevent vegetation managers from getting their work done.  Sometimes it can seem like biologists have goals that run contrary to those of vegetation managers – the first focused on never touching any vegetation anywhere; the second intending to remove or prune vegetation in and near every power delivery lines and corridors. 

Removing vegetation incompatible with or hazardous to power lines in riparian corridors has been the source of some of the most challenging discussions between vegetation managers and biologists. However, most involved in those discussions (whether vegetation managers or biologists) understand that intelligent, collaborative prescriptions can preserve both goals: 

  • Implementing biological and environmental values
  • Meet the needs of vegetation managers to ensure the safety and reliability of the power delivery system. 

The traditional way of managing vegetation under power lines and along transmission corridors in many parts of the country has been to “clear cut” all offending vegetation in the region.  But “clear cutting” can have several undesirable side effects, such as introducing and spreading exotic and invasive weeds resulting in habitat degradation and greater maintenance requirements or rapid regrowth of mowed vegetation resulting in  greater needs for and frequency of maintenance.  Each of these problems can be managed with a more collaborative approach using Integrated Vegetation Management. 

Measures to prevent and minimize exotic and invasive weeds may include timing vegetation removals to avoid creating perfect seeding conditions for invasive weeds, maintaining and enforcing clean equipment and vehicles to effectively quarantine the area from introduced weeds, specifically planting a post-management crop to reduce the suitability for invasive weeds, or selective weed control and herbicide use to minimize successful establishment of invasive weeds. 

Rapid regrowth of the existing vegetation is a natural adaptive response to disturbance, which allows a series of forest plants to become established, grow quickly and replace the lost trees with new trees.  Vegetation managers have known for decades that technicians  can selectively remove or inhibit the fast-growing tall species such as Douglas-fir (Pseudotsuga Menziesii), while preserving or enhancing slower-growing shorter species such as coyote bush (Baccharis sp.) toyon (Heteromeles sp.) manzanita (Arctostaphylos sp.),or elderberry (Sambucus sp.) where appropriate.  Another tool is to promote smaller shrubs that will shade out and slow the growth of taller species that would otherwise require more aggressive maintenance.

Another opportunity for biological enhancement in vegetation management concerns the fate of downed wood.  Urban arborists and tree removal companies are accustomed to leave a “clean” site.  On a golf course, this means all the downed wood, tree trimmings, and cut logs need to be removed from the site. It has become typical practice to chip pruned and downed wood, and either spread it onsite or remove and sell the material as biomass fuel.  Both approaches can be beneficial in certain circumstances, and both can be damaging to wildlife and natural habitat in others.  Often in either instance, it is often a missed opportunity for biological enhancement. 

Tree swallows, woodpeckers, owls, bluebirds, and kestrels are all dependent on holes in trees to nest and raise their young.  Acorn woodpeckers use soft tree trunks as granaries to store acorns.  Squirrels, raccoons, opossums and bats all depend on the soft cavity and elevated bark for refuge and protection.  Recognizing this, vegetation managers have recently begun leaving (often at the request of fish and game officials) selected trees when required to do line clearing, in order to provide a source of new snags and soft wood for wildlife. 

Rather than remove a dead tree at the ground level, vegetation managers can top the tree at 20-30 feet, to ensure that the standing trunk is below the transmission line, but still provides an elevated site suitable to support wildlife needs.  The standing trunk also can maintain and contribute some riparian shading to the stream; a resource important for fish and frogs.  In this case, if and when the snag eventually degrades and falls, it does so without compromising transmission reliability while continuing to contribute to the biological environment.

Today, the Integrated Vegetation Management Program at PG&E benefits from the expert advice of experienced biologists by:

  1. Identifying and implementing measures to meet vegetation removal goals, while protecting or enhancing biological values such as snags.
  2. Selectively removing or enhancing species that will maintain a stable community that requires less maintenance, and supports greater biological diversity and abundance.
  3. Managing noxious and invasive weeds to prevent transmission corridors from degrading adjacent habitats.
  4. Carefully considering the potential benefits and values of leaving downed wood on site, either as chips or logs and boughs.
  5. Identifying opportunities to provide mitigation and improve biological values in the course of managing transmission line safety and reliability.

Biologists and vegetation managers should work together to meet multiple objectives of safety, biological preservation and enhancement.

EJ Koford is a senior terrestrial biologist at PG&E.

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