NATURAL PROCESSES FOR THE RESTORATION OF DRASTICALLY DISTURBED SITES

Abstract

Abstract. Natural processes have been revegetating naturally disturbed sites (landslides, volcanic explosions, earthquakes, etc.) since the advent of terrestrial vegetation about 400 million years ago. Understanding the way these natural processes operate provides a framework for the design of restoration programs for anthropogenic disturbances (mines, industrial disturbances, etc.). The first step in the design of a natural process based restoration program is to identify what it is that is delaying the natural recovery from occurring (filters). Common abiotic stressors (filters) are adverse texture, nutrient status, adverse chemical properties, soil temperature extremes, compaction, adverse micro-site conditions, and excessive erosion. Biotic filters include herbivory, competition, propagule availability, phytotoxic exudates, facilitation, and adverse species interactions. Once the filters that are preventing recovery are identified and addressed, the natural processes will operate to restore the site. Care must be taken not to solve one problem by creating another. Traditional grass and legume seeding has been used to control erosion on many reclamation sites. However, the seeded cover has been found to restrict the growth of woody species so if a forest is what the restoration program is directed at, then seeding with grasses and legumes may be inconsistent with desired results. Making sites rough and loose can address a number of filters (compaction, excess erosion, lack of micro-sites, soil temperature extremes) and costs about a third of the cost of traditional hydroseeding. In many cases, there are ample seed sources nearby and making a mine site rough and loose with the application of large woody debris at a rate of 100 m/ha (determined from studies in Northern Alberta) can initiate the recovery process. Pioneering species often have effective seed dispersal mechanisms so creating the right habitat can result in the establishment of the pioneering species that are adapted to the local conditions. Practices such as making sites rough and loose (like trees in a forest turning up the soil) and scattering large woody debris on the area can initiate recovery on drastically disturbed sites.