Nutrient turnover studies in Alpine ecosystems

Summary

• 1. A plot of the Caricetum firmae in the Northern Calcareous Alps (at 2,160 m above sea level) was investigated during the growing season 1973 with regard to dry matter, nitrogen, phosphorus, and potassium content of overground and underground phytomass, including accumulated litter.

• 2. Compared to another habitat of the same community at 2,010 m a.s.l., the overground phytomass in the state of maximum development (ca.250 g per m²) and the store of nutrients (4 g N, 0.25 g P and 2.4 g K per m²) are nealy, the same, but the primary production is less (ca. 100 g as against ca. 160 g per m²).

• 3. The accumulation of litter in relation to the annual overground production is nearly 30:1.

• 4. The content of N, P, and K in the predominant species Carex firma and Dryas octopetala ranks near the inferior limit known for terrestrial plants. The minimum values are attained in the state of maximum development (mid-August).

• 5. The mineralization of N amounts to about 2 g per m² during the growing season and thus exceeds the quantity that enters into the overground production. The maximum mineralization is found 5 to 10 cm under the soil surface. In this layer most of the fine roots are concentrated.

• 6. The lactate-soluble content of P and K in the soil averages ca. 0.3 or 1.5 per m² and decreases from the beginning to the height of the growing season by ca. 0.35 or 0.5 g per m² with a slight increase toward the end. In the field incubation experiments losses of P and K, interpreted as microbial incorporation, prevailed during the growing season. It was hardly possible to determine evident relations between the fluctuations of P and K in the soil and those in the phytomass.

• 7. The Caricetum firmae ranks between the “typical arctic tundra” and the “dwarf-shrub tundra” with regard to the obtained data on phytomass, primary production, and nutrients, except for the underground production which seems to be remarkably higher.