A Multivariate Approach to the Analysis of Factorial Fertilization Experiments in Alaskan Arctic Tundra

Lechowicz, M; Shaver, G

Canonical analysis was used to analyze the results of factorial NPK fertilization trials on six species growing in arctic tundra at Eagle Creek, Alaska, USA (latitude 6510'N, longitude 14530'W): the graminoids Eriophorum vaginatum and Carex bigelowii, the deciduous shrubs Betula nana and Vaccinium uliginosum, and the evergreen shrubs V. vitis-idaea and Ledum palustre. In an extension of early univariate analyses, multivariate comparisons were made based on shot concentrations of N, P, K, Ca, and Mg as a measure of overall nutrient balance. In the unfertilized controls, the graminoids were richer in K than the other growth forms, deciduous shrubs had higher concentrations of N relative to P and Ca than the evergreen shrubs, and the deciduous-evergreen contrasts were greatest early in the growing season. An NPK fertilization triggered disproportionate increases in K concentration in the graminoids and increased N relative to P and Ca in the evergreen shrubs. The effect of fertilization on nutrient balance of the deciduous shrubs in the spring following fertilization was like that of the evergreen shrubs but by late summer had shifted to the graminoid pattern. Nitrogen and phosphorus consistently produced contrasting shifts in the nutrient balance in all three growth forms. In contrast to the two Vaccinium shrubs, the nutrient balance of the graminoid E. vaginatum was strongly affected by any fertilization involving potassium. In general, factorial combinations of N, P, and/or K produced shifts in the nutrient balance qualitatively intermediate to those resulting from the nutrients added singly. Many differences among growth forms apparent here were not discerned in the earlier univariate analyses of these fertilization trials. Particularly when combined with factorial fertilization experiments, canonical analysis can provide considerable insight into the response of nutrient balance to fertilization and help elucidate the ecological significance of these response patterns.

A Multivariate Approach to the Analysis of Factorial Fertilization Experiments in Alaskan Arctic Tundra

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