Impact of arbuscular mycorrhizal fungi on N and P cycling in the root zone

Abstract

Hamel, C. 2004. Impact of arbuscular mycorrhizal fungi on N and P cycling in the root zone. Can. J. Soil Sci. 84: 383-395. The influence of arbuscular mycorrhizal fungi (AMF) on soil processes is difficult to define, in part because it varies with the plant and fungal genotypes as well as with environmental conditions. The influence of AMF on N cycling is just being discovered. This short review examines areas of knowledge related to the nature of the mycorrhizosphere, AMF-microbe interactions, and N and P mobilization in the root zone. The role AMF could play in the root zone in N and P dynamics is presented. The spatial organization of roots and hyphae in soil suggests that AMF may enhance the reabsorption of nutrients lost through root exudation. These fungi influence soil microorganisms and, hence, they may influence biochemical reactions in soil including mineralization of organic matter and nitrification. AMF seem to improve the capacity of their host plant to use organic sources of P and N. AMF might improve the ability of plants to compete with saprotrophs for the uptake of P and N. The impact from this latter effect of AMF could exceed that stemming from their possible direct use of amino-acid-N, their production of phosphatase enzymes and possibly of organic anions. Better competitive ability of mycorrhizal plants under conditions of low soil P and N levels could reduce saprotrophic populations and, if this occurs, regulate soil organic matter turnover rate. The management of biological soil resources, in truly sustainable cropping systems, may be the largest challenge in crop production. Il est difficile d'établir avec précision l'incidence des mycorhizes à arbuscules (MA) sur les processus du sol, parce qu'elle varie, d'une part, avec la plante et le génotype des champignons, mais aussi avec les conditions environnementales. On commence à peine à décou-vrir l'influence des MA sur le cycle de l'azote. Ce court article fait le point sur ce qu'on sait de la nature de la myco-rhizosphère, des interactions entre les MA et les microorganismes et de la mobilisation du N et du P dans la rhizosphère. Suit une description du rôle que les MA pourraient jouer dans la dynamique du N et du P au niveau de la rhizosphère. L'organisation spatiale des racines et des hyphes dans le sol laisse croire que les MA pourraient faciliter la réabsorption des éléments nutritifs que les racines perdent par exsudation. Les champignons influent sur la microflore tellurique, donc pourraient modifier les réactions biochimiques dans le sol, y compris la minéral-isation et la nitrification de la matière organique. Les MA semblent accroître la capacité de la plante hôte à exploiter les sources de P et de N organiques. Ils pourraient aussi amener les plantes à mieux concurrencer les saprophytes pour l'absorption du P et du N. Cette dernière propriété pourrait avoir une plus grande incidence que celle issue de l'utilisation directe éventuelle du N des acides aminés, de la synthèse de phosphatase et peut-être de la libération d'anions or...

Microbial inoculation influences arbuscular mycorrhizal fungi community structure and nutrient dynamics in temperate tree restoration

“…We failed to find a significant influence of inoculation on general fungal and bacterial communities, which are traditionally thought of as the most important functional groups in N cycling. However, differences in AMF communities may have altered the function of both general fungi and bacteria, as complex interactions between these functional groups are likely (Burke et al ; Hamel ). It is also possible that AMF played a more critical role in rhizosphere N cycling in our study than has been traditionally described (Read & Perez‐Moreno ).…”

Grain Legumes in Northern Great Plains: Impacts on Selected Biological Soil Processes

“…The beneficial relationship between the two can increase the uptake of nutrients and water in plants, and can influence N 2 fixation in legumes by improving host nutrition (Ocampo, 1986). Hamel (2004) has reviewed the impact of mycorrhizae on crop N and P nutrition. This relationship in turn can also influence other microorganisms in the community by altering nutrient status and other interactions (Johnson et al, 1992).…”

Seasonal analyses of arbuscular mycorrhizae, nitrogen-fixing bacteria and growth performance of the salt marsh grass Spartina patens

“…The importance of biotic interactions for plant success often increases with the severity of the abiotic environment (Walker and Chapin 1987), and in such cases, mycorrhizal root networks have often been shown to enhance plant growth and acquisition of increasingly limited soil resources (Allen 1991;Hamel 2004;Rozema et al 1986;Smith and Read 1997). High salt marsh systems are an excellent example of this phenomenon, since they rely on unpredictable tidally-imported nitrogen (N) to reduce N-limitations, affecting the degree to which the dominant grasses such as Spartina patens and Distichlis spicata form associations with arbuscular mycorrhizal fungi (AMF) within their roots (Cooke et al 1993;Hoefnagels et al 1993;Patriquin and Keddy 1978).…”