Foliar and soil nutrients in tundra on glacial landscapes of contrasting ages in northern Alaska

Abstract

We compared foliar and soil nutrients in tundra between two different landscapes in the foothills of the Brooks Range, Alaska, that were deglaciated >50,000 and >11,500 years ago, respectively. Our goal was to determine whether foliar nutrients reflect differences in soil nutrient availability, or whether species and/or growth forms have characteristic foliar nutrient concentrations regardless of soil nutrient availability. Sites are located less than 2 km from one another, and both are dominated by moist tussock tundra. However, forbs are less common and deciduous and evergreen shrubs more common at the older site. Soils at the older site had higher net nitrogen (N) mineralization rates, but lower pH, cation exchange capacity, percent base saturation, exchangeable calcium (Ca) and magnesium, total Ca, and inorganic N and phosphorus than the younger site. Foliar nutrients generally reflected differences in soil net N mineralization rates and exchangeable base cations, with higher foliar N at the older site, and higher foliar Ca at the younger site. However, large differences in foliar nutrients also occurred among growth forms, and the magnitude of the site differences in foliar nutrients between sites was growth form-dependent. In general, species with short leaf lifespans (deciduous shrubs, sedges, and forbs) had higher foliar nutrient concentrations than evergreen species. Thus, foliar nutrients were a function both of underlying variation in soil nutrient availability and of species and growth form composition.