Age-Related Patterns of Nutrient Allocation in Lycopodium Annotinum from Swedish Lapland: Strategies of Growth and Population Dynamics of Tundra Plants 5

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Abstract
The sporophyte of L. annotinum L. consists of a series of annually produced segments organized into branches which can be aged. Each segment follows 1 of 3 basic life cycles contributing to either branches (which support roots, colonize new ground and reproduce vegetatively), aerial branches (which photosynthesize and support strobili) or strobili (which produce spores). Longevity varies from 25 yr in horizontal segments to 1 yr in strobili and photosynthesis is restricted to segments less than 7 yr old. Dry weight and the nutrient status of a segment varies according to its particular life cycle and age. Concentrations of N, P, Mg and soluble carbohydrates in young segments are highest where the life span is shortest and the physiological activity most intense. However, the rate of decrease in concentration is greatest where the initial concentrations are highest. Strobili, e.g., show a decrease of 64% of the initial concentration of P (0.3% of dry weight) in 3 yr whereas horizontal segments show this decrease from an initial 0.2% of dry weight over 19 yr. Energy is stored in fats and soluble carbohydrates which occur in great amounts suggesting that L. annotinum is very efficient at capturing energy in the severe climate of the subarctic birch forest. In contrast, mineral nutrients appear to be limiting and they are conserved in L. annotinum which can grow with extremely low concentrations of some elements (e.g., K) while recycling N, P and K within the plant. The plant forms an almost closed perennating system of indefinite growth.
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