The Long Term Ecological Research (LTER) Network was created by the National Science Foundation (NSF) in 1980 to conduct research on ecological issues that can last decades and span huge geographical areas. For more than three decades, the Network has generated rigorous, site-based scientific research that has led to important findings on regional and continental scales. Each site develops individual research programs in five core areas Pattern and control of primary production; Spatial and temporal distribution of populations selected to represent trophic structure; Pattern and control of organic matter accumulation in surface layers and sediments; Patterns of inorganic inputs and movements of nutrients through soils, groundwater and surface waters; and Patterns and frequency of site disturbances.