Sensitivity of forest-floor mosses in boreal forests to nitrogen and sulphur deposition
- Cite this article as:
- Mäkipää, R. Water Air Soil Pollut (1995) 85: 1239. doi:10.1007/BF00477151
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The response of forest-floor mosses to deposition of nitrogen (N) and sulphur (S) was examined in field conditions in a 60-year-old Norway spruce (Picea abies Karst.) stand in southern Finland. The experimental plots received nitrogen (25 kg N ha−1) and sulphur (30 kg S ha−1) as ammonium sulphate once a year for 4 years.
The dominant moss species on the site were Pleurozium schreberi (Mitt.) and Dicranum polysetum (Sw.). The biomass of the dominant moss species was decreased significantly by N and S deposition during the study period. Due to the addition of N and S, the biomass of Pleurozium schreberi was decreased by 60% and the biomass of Dicranum polysetum by 78%.
The forest-floor mosses seemed to be more sensitive to nitrogen and sulphur deposition than vascular plants were. Since bryophytes lack a cuticle and absorb water very rapidly after rain episodes, they are more exposed to the direct effects of acid deposition. Thus, mosses may indicate changes in forest vegetation due to acidic deposition. Boreal coniferous forests are characterised by a thick moss layer, which has low thermal conductivity and high water-absorbing capacity. Loss of the moss layer may expose the underlying soil ecosystem to desiccation and to greater variation in temperature. On the other hand, destruction of the moss layer may improve the regeneration of vascular plants.