H Väre | PubMed Health

PubMed2002

Seasonality of root fungal colonization in low-alpine herbs.

Arbuscular mycorrhizal (AM) and dark septate endophytic (DSE) fungal colonization of Alchemilla glomerulans, Carex vaginata, Ranunculus acris ssp. pumilus and Trollius europaeus growing in low-alpine meadows in the Finnish subarctic were studied at different times during the growing season. Fungal colonization was correlated to soil soluble phosphorus (P) concentration. The influence of flower bud removal on fungal colonization was investigated in A. glomerulans, C. vaginata and R. acris and the correlation between AM and DSE colonization was studied. The fungal colonization patterns were found to be species-specific. R. acris maintained a relatively high rate of fungal colonization throughout the summer, while the rates of colonization of T. europaeus were lower and decreased towards the end of the season. A. glomerulans had constant arbuscular and vesicular colonization throughout the summer, but hyphal and DSE colonization declined towards the end of the season. C. vaginata did not form arbuscular mycorrhiza, but was colonized by DSE fungi and hyaline septate hyphae throughout the season. The soil soluble P concentration showed some seasonal variation, but was also highly variable between the study sites. Bud removal decreased arbuscular colonization of R. acris, but no unique effects were seen in any other parameters or the other species studied. The root fungal parameters correlated with soil P in some species at some sites, but no consistent trend was found. DSE colonization was positively correlated with root vesicular and hyphal colonization in some cases. The differences in fungal colonization parameters may be related to species-specific phenologies.

Alchemilla↗

PubMed1998

Vegetation Composition Determines Microbial Activities in a Boreal Forest Soil.

Abstract Forest soil ecology was studied in Fennoscandinavian dry Scots pine forests grazed by reindeer to varying extents (ungrazed, lichen-dominated-sites; grazed sites; and bryophyte-dominated sites). We hypothesized that the productivity parameters of the site (i.e., tree growth and soil nutrient concentrations), the vegetation composition, and the microbial activities are directly correlated. Since the productivity of the lichen-dominated ecosystem is low, microbial activities are assumed to be naturally low. Grazing was expected to decrease both the amount of Scots pine fine roots and the soil microbial activities. Several variables on the characteristics of the soil microbial community, Scots pine fine roots, soil nutrients, and tree growth were studied in relation to vegetation composition by using non-metric multidimensional scaling (NMDS). Basal respiration (Bas), metabolic quotient of the microbial community (qCO2), and pine fine root parameters increased toward the ungrazed, nutrient-poor, lichen-dominated sites, which were grouped at one end of the first axis in the NMDS ordination. Soil nutrient and tree growth parameters and thickness of the humus layer increased toward bryophyte-dominated sites, which were grouped at the other end of the first axis in the ordination. The grazed sites fell between them. These were characterized by lower Bas and qCO2 values and longer lag, compared to ungrazed lichen- or bryophyte-dominated sites, probably due to decreased carbon input and microclimatic change (the soil without lichen carpet is exposed to direct sunlight and wind). Microbial biomass (Cmic), fungal biomass (ergosterol concentration), and the specific growth rate (µCO2) were not related to vegetation ordination. The high fine root production is the most plausible explanation for the high microbial activities at nutrient-poor, lichen-dominated sites, which produce qualitatively poor and slowly decomposing litter, as fine roots secrete considerable amounts of organic substances. At bryophyte-dominated sites, the higher soil nutrient concentrations and the higher production of easily decomposable substrates are likely to maintain the microbial activities.

Journal Article↗