Tactic TR-7: Enhancing Natural Revegetation
Natural revegetation occurs when plants re-establish on a disturbed or spill-affected site without seeding or planting. Enhancing natural revegetation, rather than applying plant cultivation treatments, is appropriate under any of the following conditions:
• The effects of the spill and cleanup were minor, so that adequate recovery of surviving vegetation is likely to occur within an accept-able period of time.
• Seeding or planting would interfere with eventual re-establishment of native tundra plants.
Enhancing natural revegetation is generally pre-ferred when the long-term goal is to rehabilitate tundra plant communities with indigenous vegetation. Natural revegetation also increases the probability that the site eventually will resemble the surrounding tundra. Long-term observations have shown that seeding can provide ground cover quickly (1–3 years), however, these grasses are eventually replaced by indigenous species better adapted to the tundra growing conditions. Although restoring the ecological functions and plant communities is possible at a spill site, the goal at most sites is rehabilitation. Rehabilitation is the promotion of native tundra vegetation to reestablish a plant community similar to the one that grew there previously (Figs. 88–91).
The following tactics may be used to enhance natural revegetation:
- Apply fertilizer (Tactic TR-8) to the perimeter of a spill site to increase the seed production and vegetative growth of the surrounding plant community. The wind and wildlife can spread the seeds onto the site.
- Extend the growing season (Tactic TR-2).
- Watering (Tactic TR-4) or dewatering (Tactic TR-1)
Considerations and Limitations
- Analyze soil properties (Tactic AM-5) to evaluate whether natural revegetation is feasible. If the spill residual has created excessively acidic, alkaline, or saline conditions in the soil, plants may not be able to re-establish.
- Concentration of spilled substance in soils cannot be phytotoxic (lethal to plants).
- Monitor the site (Tactic AM-6) for several growing seasons to evaluate revegetation trends.
- Natural revegetation typically requires 15 to 30 years to rehabilitate the plant cover and diversity to pre-disturbance values. The restoration of the original ecosystem functions and values, if possible, will take much longer.