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Long term ecological research sites within the U.S. date to 1911 when the Priest River Experimental Forest was set aside as a research center. By 1980 when the Long Tenn Ecological Research program was established, 78 experimental forests and> 10 rangeland research stations had been conducting research, in most cases for > 40 years. Cmrently this large suite of USDA and NSF supported sites, including 26 LTER sites, represents a wide range of ecosystem types, from forests to grasslands and shrub lands, freshwater lakes and streams, near coastal marine and estuaries as well as urban areas and systems in Antarctica. A variety of different kinds of data have been collected from these sites through time, ranging from primarily climatic and demographic data since the 1800 s to more recent quantitative assessments of plant, animal, and microbial populations and communities, hydrological and biogeochemical cycles, biodiversity, and disturbance regimes. 1n addition, pollen records and tree-ring data can be used to push data availability back even further. Long term data are invaluable in both understanding the properties and dynamics of ecological systems as well as in forecasting future system dynamics.

Trends in long term data are critical to the ability to:

  1. distinguish temporal variability from directional changes,
  2. relate changes in response variables to changes in drivers or other response variables,
  3. relate changes in ecological dynamics with changes in socio-economic systems,
  4. forecast future dynamics under changing climatic, disturbance, and landuse.