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Abstract: Inoculation experiments were performed to compare the growth of snow blight (Phacidium infestans Karst.) mycelium on Scots pine (Pinus sylvestris L.) seedlings on sites with or without undergrowth and green logging slash. Inoculations were performed on Scots pine seedlings planted within undergrowth of Scots pine, Norway spruce (Picea abies (L.) Karst.) and birch (Betula sp.). Snow depth and temperature were recorded in uncleaned and cleaned environments. No significant effect of retained undergrowth was found. However, snow blight growth was enhanced by artificially added birch stems, mimicking an uncleaned environment. There were no differences in snow depth between cleaned and uncleaned areas. Mean daily snow temperature did not differ between treatments. However, the snow temperature variation was significantly higher in an uncleaned area. Occasions with temperatures above 0°C were equally frequent in uncleaned and cleaned environments. Temperatures above the lower limit for mycelial growth (−5°C) were more frequent in the cleaned environment. Fresh logging slash of Scots pine enhanced snow blight infection. It is concluded that the practice to leave 1–3m high undergrowth after harvest (in order to increase biodiversity) will probably not result in dramatically enhanced snow blight growth in Scots pine regenerations. [Copyright &y& Elsevier]

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The possible use of the understorey vegetation as a biomonitor for atmospheric deposition of acid and nutrients was explored by analyzingthe vegetation of two pine forest stands in central and northern Sweden. Percentage cover of vascular plants, bryophytes and lichens was estimated in four factorial experiments with a total of 122 plots. Inthese experiments N, P, K, lime and sulphuric acid had been regularly added over a period of ca. 15 years. Redundancy analysis (RDA) was used to detect treatment effects on the composition of the vegetation, and was compared to analysis of variance (ANOVA) on Ellenberg's indicator values. Of all treatments nitrogen addition had by far the strongest effect, causing a shift in dominance from cryptogams and Ericaceae towards Deschampsia flexuosa and ruderal species. Acidification caused a decrease in the cover of most species, while liming increased the dominance of Ericaceae. There was a fairly good correspondence among the N fertilization, acidification and liming treatments and the indicator scores for nitrogen and acidity. Although the indicator method was not as sensitive as RDA in discriminating between the treatments, it may have a wider applicability in biomonitoring because it yields information on possible causal factors behind differences in vegetation. (c) 1999 Elsevier Science B.V. [ABSTRACT FROM AUTHOR]