Fine-root distribution and morphology in an acidic Norway spruce (Picea abies (L.) Karst.) stand in SW Sweden in relation to granulated wood ash application

Wood ash is recommended as a compensatory fertiliser to counteract the effects of acidic deposition on forest ecosystems. Spatial distribution of biomass,necromass and morphology parameters of the fine roots (diameter classes < 1, 1-2, < 2 mm) of Norway spruce (Picea abies (L.) Karst.) were analysed in response to fertilisation with granulated wood ash (GWA) in a long-term field experiment in SW Sweden. GWA was applied as a single dose of 3200 kg ha(-1) and the fine roots were sampled 9 years later by soil coring. Soil cores were divided into 1-cm strata within the top 0-2.5 cm humus limits, the lower humus below 2.5 cm (with varying thickness) and the mineral soil to 50 cm depth (from ground surface). Total fine-root biomass in the GWA treatment, 256 +/- 20 and 258 +/- 25 g m(-2): respectively, and length 2072 +/- 182 and 1800 +/- 198 m m(-2), respectively, did not differ statistically from each other. Total fine-root necromass in the 1-2 mm fraction was significantly higher in C than in the GWA treatment, 130 +/- 12 and 80 +/- 10 g m(-2), respectively. Fine-root biomass in the < 1 mm fraction was significantly greater in the lower humus in the GWA treatment, but this did not affect the total biomass in the < 1 mm fraction in the whole soil profile. The biomass-to-necromass ratio (1-2 mm) was significantly higher in the GWA treatment in the 0-30 cm soil layer than in the corresponding layer of the control. Specific root length (SRL) was lower in the GWA treatment than in the control in the 0-5 cm soil layer. The lower necromass and SRL were more clearly related to the GWA treatment, whereas the difference in the vertical distribution of biomass may have been related to the thicker humus layer in the GWA plots. (c) 2005 Elsevier B.V. All rights reserved.