The mycorrhizal status of plants in fragile ecosystems

Many ecosystems, and as a consequence their floral components, are threatened by human impact. The biodiversity of such habitats is decreasing rapidly. However, high diversity environments show higher productivity and CO 2 ; absorption capacity. An important pre-requisite for plant diversity appears to be the diversity of vesicular- arbuscular (VA) mycorrhizal fungi in soil. With increasing number of VA fungal species plant diversity increases as well. Nevertheless, damage to the vegetation or to the soil is disturbing the fungal community in soil and leads to a reduction of inoculum sources. For re-vegetation projects an intact soil microflora, including the mycorrhizal fungi, is essential. Therefore, it is of major importance to be able to replace lost inoculum in restoration projects. One aim of this project is thus to investigate the vesicular-arbuscular mycorrhizal status (root infection intensity, spore density in soil) of 12 endangered plant species and 11 plant species of a rare plant community in the county of Salzburg, including Apium repens, Allium carinatum, Betonica officinalis, Bidens cernuus, Drosera intermedia, D. rotundifolia, D. x obovata, Filipendula vulgaris, Gladiolus palustris, Lycopodiella inundata, Senecio aquaticus and Serratula tinctoria and for the plant community Laserpitium siler, Allium montanum, Calamagrostis varia and Carex humilis as characteristic species as well as Acinos alpinus, Buphthalmum salicifolium, Carduus defloratus, Euphorbia cyparissias, Scabiosa columbaria, Sedum album and Teucrium montanum. Spores have been used for a long time as main morphological identification source. The relationship between the spores found in soil and the fungi colonizing the plant roots is not always clear. Morphological attempts failed to reveal this relationship and were replaced by molecular biological methods (PCR, RFLP, sequencing). These will be used to identify the fungi colonizing the plant roots, which is a major step for inoculum production. This seems to be of utmost importance as plants receive benefits to different extents from different fungi and as introduction of inappropriate inoculum must be avoided. In analogy to VA fungi, attention is also going to be paid to "dark septate endophytes" (DSE) and their infection intensity throughout the year. DSE are considered to be able to provide nutrients for the plant and therefore it is of major concern to include such mutualistic fungal root associates in studies on the mycorrhizal status of plants. Several site parameters like soil pH, total and plant available P content, soil water content, bulk density and plant P content are determined as well in order to provide an overall view over the environment and the P nutrition of the plants investigated.

Almost all plants, including threatened species, live in a symbiosis with fungi and form a structure which is called mycorrhiza. In a study carried out at the University of Salzburg in cooperation with the University of Innsbruck the mycorrhizal status of endangered wetland plants and of a rare plant community developed on a chalk gravel slope in a NATURA 2000 habitat was analysed. All of the plant species investigated are colonized by mycorrhizal fungi, the spores of which were extracted from soil. As plant fitness may depend on their fungal symbionts, this study provides the basis for designing a suitable inoculum which could be needed for re-establishment of threatened species in a suitable environment, in case they would become extinct. The goal of the project was to analyse qualitatively and quantitatively the fungal root symbionts of a range of selected plant species by the use of molecular and microscopical methods. Healthy plant roots are normally colonized by arbuscular mycorrhizal fungi and dark septate endophytes. It is known that both groups of fungi can stimulate plant growth and nutrient uptake. The molecular analyses have revealed that some of the fungal species are specific for single plant species or sites, whereas others are rather unspecific. At least some of the plant roots analysed showed a high colonisation intensity with a great biodiversity of fungal species. Some plant roots are colonized by a range of different fungal species, some of which representing novel, yet undescribed species. It can be anticipated that the mycorrhizal fungi detected can play an important ecological role.