Arbuscular mycorrhizal fungi in tree-based intercropping systems: A review of their abundance and diversity

Arbuscular mycorrhizal (AM) fungi are important components of agroecosystems as they form symbiotic associations with the majority of agricultural crops. The mycorrhizal association is normally mutualistic and can provide a number of benefits to the host plant including increased nutrient uptake, improved water relations, and protection from pathogens. However, conventional agricultural practices have been shown to have a negative impact on the abundance and diversity of AM fungi. The use of more diverse and sustainable land use practices such as tree-based intercropping can have the potential to reduce the negative impact of agricultural practices on AM fungi. This paper reviews the literature to investigate the effect of temperate and tropical tree-based intercropping systems on the abundance and diversity of AM fungi. Evidence from these studies suggests that tree-based intercropping systems support a more abundant and diverse AM fungal community compared to conventionally managed systems. However, there are studies that observed zero or negative significant effects on the AM fungal community as a result of incorporating trees into agricultural systems. The variable effect of tree-based intercropping systems on AM fungi observed may be a function of the different cultivation techniques, climatic variation, or diverse tree-crop combinations used within the different tree-based intercropping systems. To further our understanding of AM fungal dynamics in tree-based intercropping systems, future research should focus on the influence of tree species with varying mycorrhizal associations and the functional role of common mycelial networks in these systems, while utilizing applicable molecular techniques. (C) 2010 Elsevier GmbH. All rights reserved.