『Abstract
Critical loads of nitrogen (N) from atmospheric deposition were
determined foe alpine lake ecosystems in the western US using
fossil diatom assemblages in lake sediment cores. Changes in diatom
species over the last century were indicative of N enrichment
in two areas, the eastern Sierra Nevada, starting between 1960
and 1965, and the Greater Yellowstone Ecosystem, starting in 1980.
In contrast, no changes in diatom community structure were apparent
in lakes of Glacier National Park. To determine critical N loads
that elicited these community changes, we modeled wet nitrogen
deposition rates for the period in which diatom shifts first occurred
in each area using deposition data spanning from 1980 to 2007.
We determined a critical load of 1.4 kg N ha-1 year-1
wet N deposition to elicit key nutrient enrichment effects on
diatom communities in both the eastern Sierra Nevada and the Greater
Yellowstone Ecosystem.
Keywords: Critical load; Atmospheric nitrogen deposition; Alpine
lake ecosystems; Diatoms』
1. Introduction
2. Methods
3. Results
4. Discussion
5. Conclusions
Acknowledgments
References