Changes in the concentrations of phenolics and photosynthates in Scots pine (Pinus sylvestris L.) seedlings exposed to nickel and copper.

Studies were done on the effects of elevated soil concentrations of copper (Cu) and (Ni) on foliar carbohydrates and phenolics in Scots pine (Pinus sylvestris L.). Four year-old seedlings were planted in pots filled with metal-treated mineral forest soil in early June. The experimental design included all combinations of four levels of Cu (0, 25, 40 and 50 mg kg(-1) soil dw) and Ni (0, 5, 15 and 25 mg kg(-1) soil dw). Current year needles were sampled for soluble sugar, starch and phenolics at the end of September. Ni increased sucrose concentration in the needles, indicating disturbances in carbohydrate metabolism. Trees exposed to Ni had higher concentrations of condensed tannins compared with controls. In contrast, concentrations of several other phenolic compounds decreased when seedlings were exposed to high levels of Cu or to a combination of Ni and Cu. The results suggest that concentrations of phenolics in Scots pine needles vary in their responses to Ni and Cu in the forest soil.

Shift in ectomycorrhizal community composition in Scots pine (Pinus sylvestris L.) seedling roots as a response to nickel deposition and removal of lichen cover.

Scots pine seedlings were exposed to wet-deposited nickel (Ni) and removal of lichen cover in a dry heath Scots pine forest. Ni deposition affected the colonization of roots by indigenous ectomycorrhizal fungi in contrasting ways in intact and skimmed quadrats. Highest frequencies of tubercle morphotypes of ectomycorrhiza were found in quadrats exposed to 100 mg m(-2) year(-1) Ni in lichen covered treatment, while in skimmed quadrats these peaked after the treatment with 10 mg Ni m(-2) year(-1). Removal of the lichen layer increased the value of diversity index (H') of ectomycorrhizal fungal community, probably due to the increase in the evenness of the morphotype distribution. Lichen removal seemed also to improve the condition of the short roots, as the frequencies of poor and senescent short roots were decreased by the removal.

Impact of wet deposited nickel on the cation content of a mat-forming lichen Cladina stellaris.

The impact of experimentally sprayed aqueous nickel solution on the concentrations of potassium, calcium, magnesium and nickel in three horizontal strata (top, 0-20 mm; middle, 20-40 mm; and base, 40-60 mm) of the cushion-forming lichen Cladina stellaris was investigated. The experimental nickel deposition range used corresponded with that from the pristine forests of the Finnish border to polluted industrial sites of Russian Kola Peninsula (0-1000 mg Ni(2+) m(-2) year(-1)). The lichen mat retained ca. 31-66% of the nickel deposited during two growing seasons and the relative retention efficiency was highest at the low deposition end. The concentrations of cations in lichen thalli were significantly reduced only after the highest nickel deposition. Furthermore, the separate horizontal strata responded differently to nickel exposure indicating that the cation exchange sites of the top stratum were not completely saturated by nickel even after the most severe treatment. However, nickel deposited in high doses caused considerable reduction in potassium concentration indicating damage to cell membranes. Episodically deposited high concentrations of nickel can probably affect membrane integrity before detectable changes in total concentrations of cations in the lichen thallus take place. Thus, ratios of total concentrations of cations in the lichen thallus are fairly insensitive to nickel deposition, which reduces the risk of compounding effects when the ratios are used to indicate long-term acid deposition in areas with multiple pollution problems such as Kola Peninsula.