The influence of N load and harvest intensity on the risk of P limitation in Swedish forest soils

Sci Total Environ. 2008 Oct 15;404(2-3):284-9. doi: 10.1016/j.scitotenv.2007.11.017. Epub 2007 Dec 26.

Abstract

Nitrogen (N) is often considered to be the major factor limiting tree growth in northern forest ecosystems. An increased N availability, however, increases the demand for other nutrients such as base cations and phosphorous (P) which in turn may change which nutrient is the limiting factor. If P or base cations become limiting, N will start to leach which means a risk of increased eutrophication of surface waters. As many studies focus on base cations, this study instead aims at estimating P budgets on a regional scale for different harvesting scenarios relevant for Swedish conditions. P budget calculations were carried out for 14,550 coniferous sites from the Swedish National Forest Inventory, as weathering+deposition-harvesting-leaching. Three scenarios with different harvest intensities were used: 1) no harvesting, 2) stem harvesting and 3) whole-tree harvesting. The input data were derived from measurements and model results. The P budget estimates indicate that harvesting, especially whole-tree harvesting, result in net losses of P in large parts of Sweden. The highest losses were found in southern Sweden due to high growth rate in this area. In the whole-tree harvesting scenario the losses exceeded 1 kg ha(-1) y(-1) on many sites. N budget calculations on the same sites indicate that N generally accumulates in the whole country and especially in the southern parts. Consequently, the N and P budget calculations indicate that the forests in southern Sweden are in a transition phase from N-to P-limitation to growth. This transition will proceed as long as the accumulation of N continues. These results are important in a sustainable forestry context, as a basis for assessing the risk of future N leaching, and in designing recommendations for abatement strategies of N deposition and for application of wood ash recycling and N fertilization.

MeSH terms

  • Algorithms
  • Ecosystem*
  • Environmental Monitoring*
  • Nitrogen / analysis*
  • Nitrogen / metabolism
  • Phosphorus / analysis*
  • Phosphorus / metabolism
  • Risk Assessment
  • Soil Microbiology
  • Soil Pollutants / analysis*
  • Soil Pollutants / metabolism
  • Sweden
  • Trees*

Substances

  • Soil Pollutants
  • Phosphorus
  • Nitrogen