Intellectual Merit:  The arctic region has warmed significantly over the past 30 years and arctic lands and freshwaters are already changing in response.  Satellite views show a general “greening” of the arctic landscape as the tundra vegetation changes.  Measurements on the ground show increases in plant abundance and changes in animal abundance.  There are also changes in amounts of greenhouse gases released from the tundra over large regions such as the North Slope of Alaska.  Working at one site in northern Alaska since 1975, the Arctic LTER project and its predecessors have followed the effects of climate change by measuring such things as plant and animal abundances in tundra and freshwater ecosystems.  The project has also carried out experiments by making small changes in temperature and the nutrients reaching tundra, lake, and stream ecosystems.  With these experiments, that in many ways anticipate the future, the project scientists gain understanding of the long-term changes that may happen at this research site.  The goal of the project for 2004-2010 was: “To understand changes in the arctic system in river-basins and large landscapes through knowledge of the linkages and interactions among ecosystems.”

Major findings include:

1. The discovery that high concentrations of the greenhouse gases, carbon dioxide and methane, dissolve in groundwater and are transported to streams and rivers and then are released to the atmosphere.  This key process was missing from our previous carbon budgets in arctic landscapes.  This finding has led to similar discoveries in ecosystems around the world.
2. Continuous addition of a rare type of nitrogen to streams, a method for measurement of nitrogen cycling in flowing waters, was first developed at the Arctic LTER and is now used throughout the world to find out about what happens to pollutant nitrogen released to streams from farms and cities. 
3. Because photosynthesis by tiny algae in surface water is low in arctic lakes, the fish that are a major food for native peoples must depend on the photosynthesis by algae living on the bottom of shallow lakes. 
4. Small amounts of phosphate added to streams to raise the concentration by 300 parts per billion revealed an unexpected sensitivity of the species diversity of arctic streams.  Even tiny changes in nutrients change the whole ecosystem from one based on algae attached to rocks in the stream to one based on a thick cover of moss.
5. Arctic plant ecology in the 20^th century focused on plant adaptation to the physical environment: cold temperatures, light, and soil moisture.  Our discovery that only low levels of nutrients were available in soil and that plants competed for nutrients, water, and light has transformed our approach to arctic plant ecology..
6. The discovery that tundra plants derive much of their N supply from a beneficial relationship (symbiosis) between plant roots and fungi (mushrooms) has transformed our understanding of nutrient cycling and nutrient limitation for tundras and forests, worldwide.
7. Warming of the Arctic is causing increasing thawing of permanently frozen ground; the result is the creation of sinks and slumps in the land surface that are hot spots of erosion, of release of nutrients into rivers, and of decomposition of ancient organic carbon.

Broader Impacts: The scientific impacts of this research are much broader than improvement of our ability to predict the future of arctic ecosystems in Northern Alaska.  First, long-term change is of broad theoretical and empirical int...

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