Conclusions

Ecosystems at the Arctic LTER site at Toolik Lake, Alaska, respond to variations in climate at a number of temporal scales. At the scale of a single season, changes in PAR directly affect NEP, whereas rainfall events change stream flow and associ ated lake stratification and ecosystems. At the scale of year-to-year variation, warming lake temperatures may reduce the habitat suitable for lake trout, and the growth of grayling is positively correlated with wet and cold summers. For land plants, soil warming caused by early snow melt or by warm summers causes the synchronous flowering across northern Alaska of arctic cotton grass and an increase in leaf area. Finally, at the scale of multiyear variation in air temperatures, the alkalinity in lakes and steams near the Toolik Lake Field Station has doubled in the last decade. The exact reasons for this change are unknown, but they are likely related to long-term trends in climate.

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