Nutrient limitations to plant production in two tundra communities

Nitrogen and phosphorus nutrition were investigated as limiting factors to primary production in a lowland wet sedge meadow and an upland birch–willow–heath community.Response to nitrogen fertilization in both communities, including increased protein content and dry weight production, indicates that nitrogen supply limits production in both soils. In the upland community, phosphorus supply does not limit production, but in the lowland sedge meadow, dilution of the soil solution may decrease phosphorus availability and render this element limiting to production.Nitrogen, if available, can be taken up and metabolized into organic compounds despite low soil temperatures. Phosphorus metabolism may be directly limited by low soil temperatures and low available nitrogen levels.Low soil temperature exerts an indirect limitation on plant production through limitation of organic matter decomposition and microbial nitrification, thus limiting the rate of nitrogen cycling.The importance of a low nutrient regime in the Arctic may be seen in the widespread occurrence of xeromorphic characters in many taxa, which thus require minimal mineral nutrition to best use their photosynthetic capacity. The low nutrient regime may partially explain the high proportion of perennial plants in the Arctic, since these species can accumulate a nutrient pool over time from a deficient environment.