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LTER Key Research Findings

Among the many research results from LTER sites, some findings stand out as being particularly important to achieve the LTER goal of providing information to conserve, protect, and manage the nation's ecosystems. Short descriptions of key findings at each site emphasize the importance of long-term data in understanding the pace and pattern of ecological change.

Arctic Warming (ARC LTER)
Research at the Arctic LTER site is transforming scientific understanding of how the arctic landscape will respond to climate change. Warming of the Arctic is thawing previously frozen ground (permafrost) and in some places, especially where there is buried ice, the thawed soil forms sinks and slumps called thermokarst terrain. In extreme cases this thermokarst terrain leads to complete...
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Cascade Effect (ARC LTER)
The experimental addition of low levels of phosphorus (P) to an arctic stream created a gradual transformation of the tundra stream ecosystem from a cobble-bottom stream covered with diatom-dominated biofilm to a moss-dominated bottom that hosted a different community composition of invertebrates. This transformation was not predicted and was a surprise because for the first seven or eight years...
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Food Sources (ARC LTER)
Arctic Alaska contains hundreds of thousands of lakes, almost all quite shallow. Research at the Arctic LTER on shallow lakes demonstrates that the food webs leading to fish are based mostly on primary production by bottom-dwelling algae rather than on plankton food webs. Yet, arctic fishery biologists continue to emphasize planktonic food webs and recent reviews of climate change in arctic...
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Tracer Techniques (ARC LTER)
A tracer approach to investigation of the nitrogen (N) cycle of streams, first developed at the Arctic LTER, has transformed scientific understanding of the nitrogen cycle and food web structure in flowing waters. By adding a continuous drip of 15N-NH4 (ammonium) or 15N–NO3 (nitrate) to a stream and then sampling the downstream transport, uptake and recycling of nitrogen over distance and...
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Process Discovered (ARC LTER)
In the early 1990s researchers at the Arctic LTER discovered the answer to a long-standing question of why the recently measured and modeled rates of net ecosystem productivity on land were so much higher than the rates of carbon accumulation integrated over time as found in soil and peat cores. The researchers discovered that carbon dioxide and methane dissolved in groundwater in very high...
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Linked Cycles (ARC LTER)
Our understanding of tundra biogeochemistry has been transformed by long term research by the ARC LTER showing that the carbon and nitrogen cycles are strongly linked and interactive at all steps in the cycle of organic matter. Changes in the arctic carbon cycle in response to climate change cannot be understood or predicted without considering carbon-nutrient interactions. The basis for the...
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