There is growing recognition that classifying terrestrial plant species on the basis of their function (into 'functional types') rather than their higher taxonomic identity, is a promising way forward for tackling important ecological questions at the scale of ecosystems, landscapes or biomes. These questions include those on vegetation responses to and vegetation effects on, environmental changes (e.g. changes in climate, atmospheric chemistry, land use or other disturbances). There is also growing consensus about a shortlist of plant traits that should underlie such functional plant classifications, because they have strong predictive power of important ecosystem responses to environmental change and/or they themselves have strong impacts on ecosystem processes. The most favoured traits are those that are also relatively easy and inexpensive to measure for large numbers of plant species. Large international research efforts, promoted by the IGBP–GCTE Programme, are underway to screen predominant plant species in various ecosystems and biomes worldwide for such traits. This paper provides an international methodological protocol aimed at standardising this research effort, based on consensus among a broad group of scientists in this field. It features a practical handbook with step-by-step recipes, with relatively brief information about the ecological context, for 28 functional traits recognised as critical for tackling large-scale ecological questions.

/pdf/a-handbook-of-protocols-for-standardised-and-easy-2uo4112zhh.pdf

A handbook of protocols for standardised and easy measurement of plant functional traits worldwide

A great diversity of plants and fungi engage in mycorrhizal associations. In natural habitats, and in an ecologically meaningful time span, these associations have evolved to improve the fitness of both plant and fungal symbionts. In systems managed by humans, mycorrhizal associations often improve plant productivity, but this is not always the case. Mycorrhizal fungi might be considered to be parasitic on plants when net cost of the symbiosis exceeds net benefits. Parasitism can be developmentally induced, environmentally induced, or possibly genotypically induced. Morphological, phenological, and physiological characteristics of the symbionts influence the functioning of mycorrhizas at an individual scale. Biotic and abiotic factors at the rhizosphere, community, and ecosystem scales further mediate mycorrhizal functioning. Despite the complexity of mycorrhizal associations, it might be possible to construct predictive models of mycorrhizal functioning. These models will need to incorporate variables and parameters that account for differences in plant responses to, and control of, mycorrhizal fungi, and differences in fungal effects on, and responses to, the plant. Developing and testing quantitative models of mycorrhizal functioning in the real world requires creative experimental manipulations and measurements. This work will be facilitated by recent advances in molecular and biochemical techniques. A greater understanding of how mycorrhizas function in complex natural systems is a prerequisite to managing them in agriculture, forestry, and restoration.

http://max2.ese.u-psud.fr/epc/conservation/PDFs/HIPE/Johnson1997.pdf

Functioning of mycorrhizal associations along the mutualism–parasitism continuum*

The role of mycorrhizal fungi in acquisition of mineral nutrients by host plants is examined for three groups of mycorrhizas. These are; the ectomycorrhizas (ECM), the ericoid mycorrhizas (EM), and the vesicular-arbuscular mycorrhizas (VAM). Mycorrhizal infection may affect the mineral nutrition of the host plant directly by enhancing plant growth through nutrient acquisition by the fungus, or indirectly by modifying transpiration rates and the composition of rhizosphere microflora.

Nutrient uptake in mycorrhizal symbiosis

Biodiversity and Ecosystem Function

Summary Here, the coevolution of mycorrhizal fungi and roots is assessed in the light of evidence now available, from palaeobotanical and morphological studies and the analysis of DNA-based phylogenies. The first bryophyte-like land plants, in the early Devonian (400 million years ago), had endophytic associations resembling vesicular‐ arbuscular mycorrhizas (VAM) even before roots evolved. Mycorrhizal evolution would have progressed from endophytic hyphae towards balanced associations where partners were interdependent due to the exchange of limiting energy and nutrient resources. Most mycorrhizas are mutualistic, but in some cases the trend for increasing plant control of fungi culminates in the exploitative mycorrhizas of achlorophyllous, mycoheterotrophic plants. Ectomycorrhizal, ericoid and orchid mycorrhizas, as well as nonmycorrhizal roots, evolved during the period of rapid angiosperm radiation in the Cretaceous. It is hypothesised that roots gradually evolved from rhizomes to provide more suitable habitats for mycorrhizal fungi and provide plants with complex branching and leaves with water and nutrients. Selection pressures have caused the morphological divergence of roots with different types of mycorrizas. Root cortex thickness and exodermis suberization are greatest in obligately mycorrhizal plants, while nonmycorrhizal plants tend to have fine roots, with more roots hairs and relatively advanced chemical defences. Major coevolutionary trends and the relative success of plants with different root types are discussed.

Coevolution of roots and mycorrhizas of land plants

This manual is the result of an ACIAR-sponsored workshop to promote the use of mycorrhizal fungi for eucalypt plantation forestry in China. The manual explains procedures used by scientists who work with mycorrhizal fungi and roots in the laboratory, nursery, or natural and managed ecosystems. Forest nursery and plantation managers, horticulturists, agronomists, students and researchers will find it useful with many of the techniques used requiring readily obtainable and relatively inexpensive equipment and chemicals.

/pdf/working-with-mycorrhizas-in-forestry-and-agriculture-3bm30xow0h.pdf

Working with mycorrhizas in forestry and agriculture.

Working with Mycorrhizas in Forestry and Agriculture

Ectomycorrhizal formation in Eucalyptus. I. Pure culture synthesis, host specificity and mycorrhizal compatibility with Pinus radiata

Growth and phosphorus acquisition of pot-grown seedlings of karri (Eucalyptus diversicolor F. Muell.) were examined following inoculation with four ectomycorrhizal fungi -Descolea maculata Bougher (two isolates), Pisolithus tinctorius (Pers.) Coker & Couch, and Laccaria laccata (Scop, ex Fr.) Berk. & Br. Seedlings were raised in steam-sterilized sand to which 13 rates of phosphorus (0.100 mg P kg-1 soil) were applied. All fungi except P. tinctorius produced a plant growth response. L. laccata produced the largest growth response. Responses were greatest at low rates of application of P to soil. There was no effect of the fungi on growth at levels of P application above 28 mg P kg-1 soil. A threshold effect (no increase in growth with increasing additions of P) characteristic of non-mycorrhizal seedlings was eliminated by mycorrhizal infection. Mycorrhizal inoculation increased P content of plant tissues at sub-optimal levels of P supply. The effect of mycorrhizas on seedling P status diminished with increasing soil P. One isolate of D. maculata often had greater rates of P accumulation and produced higher concentrations of P in plant tissues than L. laccata, but did not produce greater plant biomass. Frequency of infection for all fungi was low in soils with no additional P, and greatest with the addition of 2 mg P kg-1 soil (L. laccata and D. maculata isolate A), or 4 mg P kg-1 soil (D. maculata isolate B). Infection was reduced with increasing soil P, and not evident at 36 mg P kg-1 soil or higher levels of soil P. L. laccata had higher infection frequency and mycorrhizal root length at all levels of soil P than the D. maculata isolates. Two fungi produced basidiomes. This occurred at levels of soil P application ranging from 4 to 28 mg P kg-1 soil for D. maculata (isolate B), and at 4 to 28 mg P kg-1 soil for L. laccata.

https://nph.onlinelibrary.wiley.com/doi/epdf/10.1111/j.1469-8137.1990.tb00376.x

Growth and phosphorus acquisition of karri (Eucalyptus diversicolor F. Muell.) seedlings inoculated with ectomycorrhizal fungi in relation to phosphorus supply.

SUMMARY
Experiments were carried out to investigate the possibility that vesicular-arbuscular (VA) mycorrhizal infection of grass (Lolium perenne L.) and clover (Trifolium repens L.) roots can enhance the exchange of nitrogen between the root systems of nitrogen-fixing pasture legumes and associated grasses.

The results showed higher rates of transfer of 15N applied as (15NH4)2SO4 to the clover plants to companion grass plants when the roots were mycorrhizal. In some cases but not all the grass grew better in the mycorrhizal treatments.

An experiment in which the clover and grass roots were separated by a 60 μm (mean pore size) nylon mesh screen showed that translocation of the nitrogen was probably along the mycorrhizal hyphae. It was not clear from the data whether transfer was mediated by a common hyphal net or some other less direct means.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.1988.tb04182.x

Nicholas Malajczuk

Papers

Working with mycorrhizas in forestry and agriculture.

Working with Mycorrhizas in Forestry and Agriculture

Ectomycorrhizal formation in Eucalyptus. I. Pure culture synthesis, host specificity and mycorrhizal compatibility with Pinus radiata

Growth and phosphorus acquisition of karri (Eucalyptus diversicolor F. Muell.) seedlings inoculated with ectomycorrhizal fungi in relation to phosphorus supply.

Underground transfer of nitrogen between pasture plants infected with vesicular-arbuscular mycorrhizal fungi