Mineral diversity in wild plants: benefits and bane for moose

We studied the mineral nutrition ecology of moose, Alces alces, by a compre hensive examination of concentration levels of IS elements in browsing plan ts, and in rumen and distal colon contents, respectively. The plants, in to tal 14 species, included deciduous and evergreen trees, shrubs, herbs, gras ses and aquatic macrophytes. Our study was done in four sites in southern N orway and the plants were sampled in spring, summer, autumn and winter to d ocument seasonal trends. The plants were generally characterized by low con centrations of major elements, very low phosphorus: calcium ratios, and the willow Salix aurita - a preferred browse - had high cadmium concentrations , up to 9 ppm (dry mass). Sodium concentrations in terrestrial plants were significantly under the dietary requirement, while levels were sufficient i n aquatic plants, which, however, had high concentrations of toxic heavy me tals. We suggest that the moose experience a nutritional dilemma as a stron g physiological need for sodium results in an overintake of heavy metals. A selective intake of plants rich in heavy metals was corroborated by high h eavy metal concentrations in rumen and distal colon. Over all, the plants w ere characterized by a marked mineral diversity due to element concentratio n levels that were highly variable between species and sites. Thus, there i s a strong link between plant species diversity and mineral diversity, whic h has a pivotal role for herbivores. It is concluded that a diversity of pl ant species is a prerequisite for the mineral diversity that the moose need s to obtain essential minerals, not only in sufficient amounts, but also in physiologically balanced proportions.