Nitrogen Fixation: A Biotechnological Opportunity for Canadian Forestry

Abstract

Intensive harvesting and forest management systems will increase nitrogen and organic matter losses from forest soils, and there will be a need to manage the soils using both fertilizers and nitrogen-fixing techniques to maintain site productivity. Legumes and non-legumes with nitrogen-fixing symbioses can fix up to 300 kg ha−1 year−1 of nitrogen and provide soil organic matter, but poor soils will need fertilization to maintain the nitrogen-fixing process. There are many species and cultural techniques the forester can use, including green manuring and mixed stands, but carefully designed field trials are needed to solve cultural problems. In addition, there are many opportunities for genetic selection of both the trees and shrubs and the bacteria (actinomycetes) involved. Before the systems can be used effectively the operational foresters will need to be better informed about the soil biota and the interaction with site and vegetation. The development of nitrogen-fixing systems offers a biotechnological opportunity for Canadian foresters to increase tree yield while maintaining site productivity.