A mycorrhizal survey of plants growing on mine wastes in southeast Spain

Five sampling sites with different degree of disturbance were established in an area from the SE coast of Spain severely degraded by mining activities and covered by waste sediment. A mycorrhizal survey was carried out in the sites in relation with seasonal variations. Fifteen plants were sampled every three months during a year to ascertain arbuscular mycorrhizal root colonization and the number of spores in the rhizosphere. The mycorrhizal population level was adversely affected by soil degradation, with the lowest values of mycorrhizal colonization (none in Limonium sp.) and spore numbers (average 10.3 spores per 100 g) occurring in the most disturbed sites. In addition, seasonal differences in the incidence of mycorrhizae were observed. The highest values of average spore numbers of all the plant species sampled were obtained in July (40.3 spores per 100 g) and October (48.2 spores per 100 g), which corresponded to plant fructification and repose. The maximum mycorrhizal colonization for each individual plant was reached during flowering or vegetative growth period of the host plant. No relation between infection and spore density was found. Soil disturbance results in a decrease of mycorrhizal population level, but mycorrhizal propagules do not disappear completely suggesting a certain degree of adaptation to stress.