The root symbioses of Alnus viridis (Chaix) DC

Abstract

The present investigations were initiated because an understanding of the symbioses of Alnus viridis will influence the use of this species in New Zealand. There are extensive areas in New Zealand where vegetation and topsoil have been lost from mountain slopes. The remaining soils or substrata are usually sufficiently deficient in nutrients, especially nitrogen, that without expensive fertiliser applications artificial revegetation has proved to be either impossible or at best extremely slow. Preliminary trials with green alder have shown this species to be capable of impressive growth on climatically as well as edaphically difficult sites. The aim was thus to obtain an insight into the ability of green alder to fix nitrogen and grow under a range of controlled and natural conditions. Studies thus included were:- growth and nitrogen fixation at several sites in the field; ability to nodulate on natural soils; influence of levels of nitrogen, phosphorus and sulphur; influence of pH; effects of root temperature; nitrogen fixation by excised nodules; and phosphate uptake by ectotrophic mycorrhizas.