Role of arbuscular mycorrhizal fungi in the early growth of rowan (Sorbus aucuparia L.)

Abstract

An extensive literature search indicated that many trees on landscape sites fail to establish because of poor initial plant quality and sub -optimal planting conditions. Arbuscular mycorrhizal fungi (AMF) form a symbiotic association with many landscape plants, with the potential to improve plant establishment through improvements to root structure and enhanced stress tolerance. Several experimental studies were undertaken to determine whether rowan (Sorbus aucuparia L.), a stress - tolerant native tree, formed associations with AMF, and whether this lead to improved early growth and field performance.A field study indicated that rowan did form associations with AMF and that root colonisation levels of 30-40% were typical on nurseries and sites. The use of soil as an inoculum was investigated, and suggested that under poor nutrient conditions, microorganisms including AMF improved growth, but that under higher nutrient levels these same organisms inhibited growth. Under more standardised conditions, inoculation with commercial forms of Glomus intradices Schenk & Smith but not Glomus mosseae (Nicol. & Gerd.) Gerdemann & Trappe was found to improve early growth and winter survival. However when inoculated cell -grown plants of rowan, ash (Fraxinus excelsior L.) and cherry (Prunus avium L.) were transplanted onto a reclaimed oil - shale bing results were not so conclusive. Root mass was increased following inoculation in rowan and ash, but decreased in cherry. Inoculation was also associated with reduced survival in cherry, suggesting that further studies of the field performance of inoculated plants are required. A conceptual decision model to identify situations where inoculation with AMF might be cost -effective and beneficial is presented.