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751.
Using data from 46 sites in southern Finland and ordination methods, we examined plant-environment relationships in boreal
mesic semi-natural grasslands at two spatial scales (grain sizes), using plots of 0.25 ha and 1 × 1 m. We applied the variation
partitioning approach to determine the pure fractions of environmental variable groups and their joint effects on plant species
compositional variation in the studied grasslands. The variables related to land-use intensity and high nutrient level (especially
phosphorus) had a major role in explaining the species composition at both scales, although soil heterogeneity and habitat
characteristics also accounted for a notable amount of the species compositional variation at the 0.25 ha grain size. At the
1 × 1 m grain size, the majority of the species compositional variation was related to the “pure” spatial differences between
the studied grasslands (i.e. the site identity (dummy 0/1) variable), whereas the impacts of within-site variation of local
environmental factors were considerably smaller. High nutrient levels and variables related to low land-use intensity, e.g.
litter accumulation, were also significantly correlated with floristic variation at the 1 × 1 m grain size. Rare and declining
grassland species are associated with low-nutrient grassland sites and patches. The main recommendation for the management
planning of boreal semi-natural grasslands is that the first restoration attempts should be targeted to areas where nutrient
levels, particularly that of phosphorus, are relatively low. Soil properties and plant species composition can provide useful
guidelines for defining the correct management procedures for different sites. 相似文献
752.
753.
Acidocillin levels were determined in the middle ear exudates and serum of patients with acute exudative otitis media after oral administration of the drug. Acidocillin rapidly diffused exudate into the ear and its level in the exudate in 1 hour was 0-1.7 gamma/ml. At the same time the serum levels ranges within 4 to 25 gamma/ml. acidocillin remained longer in the ear exudate than in the serum. In 12 hours 0.2 to 1.3 gamma/ml of acidocillin was still found in the exudates, while there was no antibiotic in the serum. 相似文献