TOPOGRAPHIC PATTERNS OF ABOVE‐ AND BELOWGROUND PRODUCTION AND NITROGEN CYCLING IN ALPINE TUNDRA

Topography controls snowpack accumulation and hence growing-season length, soil water availability, and the distribution of plant communities in the Colorado Front Range alpine. Nutrient cycles in such an environment are likely to be regulated by interactions between topographically determined climate and plant species composition. We investigated variation in plant and soil components of internal N cycling across topographic gradients of dry, moist, and wet alpine tundra meadows at Niwot Ridge, Colorado. We expected that plant production and N cycling would increase from dry to wet alpine tundra meadows, but we hypothesized that variation in N turnover would span a proportionately greater range than productivity, because of feedbacks between plants and soil microbial processes that determine N availability. Plant production of foliage and roots increased over topographic sequences from 280 g·m−2·yr−1 in dry meadows to 600 g·m−2·yr−1 in wet meadows and was significantly correlated to soil moisture. Contra...

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