Arbuscular mycorrhiza in relation to management history, soil nutrientsand plant species diversity

摘要

The low nutrient status of semi-natural grasslands, pastures and meadows, reflects a continuity of nutrient reduction by grazing and hay-making. It has been hypothesized that the nutrient depletion itself may reduce competition between individuals, and that mycorrhiza smooths out differences in nutrient uptake and competitive ability, so that competition for nutrients is even further reduced. This interaction between site history, nutrient status and mycorrhiza could thus be one explanation for a high species diversity usually found in semi-natural grasslands. To determine variation in colonization of arbuscular mycorrhizal fungi (AM), three species (Achillea millefolium L., Ranunculus acris L. and Anthriscus sylvestris L.) were sampled at sites with different management history. All three species had mycorrhizal colonization. Correlations between species diversity patterns at different spatial scales (0.04m(2), 1m(2) and total species number in the site) and mycorrhizal colonization were examined. In addition, soil samples were analysed concerning P, K, N and pH. When combining measures for the three species together there were significantly higher AM colonization at sites with a long continuous management regime, compared to sites with short or interrupted management regime. A significantly positive correlation was also found between plant species diversity and colonization of mycorrhiza. Soil nutrient status and root weight density did not differ among the sites with different management regime. This indicates that increasing nutrient status, or root competition, are not likely causal mechanisms behind a reduced AM colonization rate at sites with short or interrupted management regime. The correlation with species diversity is more likely a result of management continuity itself. A long continuous management is associated with an increasing likelihood of successful dispersal of plant species as well as of fungal species.