Indirect effects of N and S deposition on a Norway spruce ecosystem. An update of findings within the Skogaby project
✍ Scribed by Lars-Owe Nilsson; Karin Wiklund
- Publisher
- Springer Netherlands
- Year
- 1995
- Tongue
- English
- Weight
- 606 KB
- Volume
- 85
- Category
- Article
- ISSN
- 0049-6979
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✦ Synopsis
In this paper we try to interpret results from different investigations where an ecosystem with Norway spruce was manipulated with increased N and S deposition via the soil system. The site, in Skogaby in Southwest Sweden, had 1989-93 an annual deposition of 9 kg NHa-N; 7 kg NO3-N and 20 kg SO4-S ha q. The stand was treated during 6 years with 100 kg N and 114 kg S ha-ry -1 in the form of ammonium sulphate (NS treatment). The stand reacted with increased above ground production of 31% after 3 years of treatment. The uptake above ground of N was 155 kg ha 1 higher than in the control. Those trends were even stronger after 6 years of treatment. There were no decreases in the uptake of P, K, Ca or Mg (but for B) after 3 or 6 years of NS-treatment. Needle macro nutrient concentrations in relation to N decreased for several nutrients due to dilution effects. As result of the NS treatment pH increased markedly in the litter layer, and less, but significantly, in the humus layer. A decrease in pH value by about 0.3 units was found in the rest of the soil profile down to 50 cm. Dry mass of needle litter fall and litter layer both increased as a result of 6 years of NS-treatment. After three years of treatment 77-80% of all living fine roots in both control and NS treatment were found in the humus layer and the upper 10 cm of the mineral soil. The amount of living fine roots in the humus layer of NS-treated trees decreased to about one third of the control, and the amount of dead fine roots increased by 150% compared with untreated trees after 6 years of treatment. It is argued that the decreased amount of living and increased amount of dead fine roots not necessarily are indications of decreased root vitality. It can also be explained by increased root turnover rate and decreased decomposition rates of N rich new and old fine root litter. No inorganic N was leached from the control plots whereas the NS treated plots started to leach NO 3 the second year of treatment. During 1989-1993 a total of 44 kg NO3-N and 30 kg NH4-N per ha was lost from the system which means that 88% of the N supplied was retained by the ecosystem. At first SO 4 was adsorbed in the soil, but after five years of treatment the output was almost equal to the input.