Comparison of Reclamation Techniques to Re-establish Western White Pine on Smelter-impacted Hillsides in Idaho

Abstract

In the spring of 1991, a study was initiated to identify techniques that could be used to reclaim steep hillsides at the Bunker Hill Superfund site with low pH soils and elevated concentrations of heavy metals near an old smelter site. Treatments included fertilizer to alleviate nutrient deficiencies, lime to raise soil pH, wood chips to increase organic matter content, and mulching to improve plant establishment and reduce erosion. Plots were planted to Pinus monticola (western white pine) seedlings alone and in combination with four species of shrubs. A mixture of eight grasses was also seeded on some plots planted to trees and shrubs to provide ground cover for erosion control. Overall, white pine survival averaged 60-80% in the best treatments after five growing seasons. The height of white pine transplants ranged between 37.1 and 69.5 cm after five years of growth across all treatments and sites which are comparable to growth rates reported elsewhere for this species. White pine survival and growth was greatest on the control, phosphorus, and lime treatments and lowest on treatments that received organic matter as an amendment primarily due to the competitive influence of herbaceous plants as opposed to any particular soil amendment. Treatments that supported high amounts of grass cover had poor white pine survival and growth, while treatments with low amounts of grass cover had high white pine survival. A combination of lime and N, P, and K fertilizer is recommended as the appropriate treatment to restore white pine in this type of environment. © 2010 Society for Ecological Restoration International.