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

Abstract

Canonical analysis was used to analyze the results of factorial NPK fertilization trials on size species growing in arctic tundra at Eagel Creek, Alaska, USA (latitude 65°10'N, longitude 145°30'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 comparisions were made based on shoot 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 NKP fertilization triggered disproportionate increases in K concentration in the graminoids and increases 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 contrasing 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.

Nutrient Stoichiometry in Pinguicula Vulgaris: Nutrient Availability, Plant Size, and Reproductive Status

“…Interspecific differences in nutrient stoichiometry have been interpreted as a reflection of the habitat characteristics in which the species or growth forms occur (Garten 1978, Marrs 1978. They also have been related to contrasting strategies of resource uptake and allocation (Lechowicz and Shaver 1982, Shaver and Lechowicz 1985, Grimshaw and Allen 1987, Thompson et al 1997). Within species, several studies have found a correlation between nutrient stoichiometry and natural (Orgeas et al 2002) or experimental (Lechowicz Dots represent the centroids of each group.…”

Individualistic Growth Response of Tundra Plant Species to Environmental Manipulations in the Field

“…First, a uniform response (or no response) might mean that the experiment did not include the factors responsible for species differentiation, as in the factorial fertilization experiments at Eagle Creek, Alaska, which showed no species differences in response to nitrogen vs. phosphorus vs. potassium fertilization (Shaver and Chapin 1980, but see Lechowicz and Shaver 1982). First, a uniform response (or no response) might mean that the experiment did not include the factors responsible for species differentiation, as in the factorial fertilization experiments at Eagle Creek, Alaska, which showed no species differences in response to nitrogen vs. phosphorus vs. potassium fertilization (Shaver and Chapin 1980, but see Lechowicz and Shaver 1982).…”

Biomass N:p Ratios as Indicators of Nutrient Limitation for Plant Populations in Wetlands

“…Thus, McJannet et al (1995) found considerable variation in the biomass N:P ratios of 41 wetland species grown at exactly the same nutrient supply. Lechowicz and Shaver (1982) suggested that the effects of nutrient availability on biomass nutrient contents involve growth-form specific patterns.…”