Eleven LTER Sites Compared for ANPP Study
In this study, Konza Researchers compared LTER rainfall and annual aboveground productivity data at forest, grassland and desert sites (see figure blow) to see how one affects the other. The results allow Knapp and Smith to speculate about the influences global climate changes might be manifested in various biomes. The study is an example of one of the first to utilize LTER data to examine processes on a continental scale.
Konza Prairie LTER principal investigators Melinda Smith and Alan Knapp recently published a study in Science (291: 481-484) comparing rainfall and annual net primary productivity (ANPP) data at 11 LTER sites. The data sets ranged from 6 to 23 years. The article illustrates the variations in ANPP across a broad spectrum of biome types. Gathering and comparing the data has allowed the authors to identify means for detecting the biotic impacts of global change phenomena. The study is a result of an exercise in synthesizing LTER data and illustrates the value of the availability of long-term broad-spectrum data for examining ecologically significant phenomena at increasingly larger scales.
As experimental research platforms rather than monitoring stations, not all the LTER sites are collecting exactly the same data the exact same way, making synthesis studies such as this an exercise in patience. "We chose the 11 sites for this study based primarily on the length of their ANPP and precipitation data sets," say Knapp and Smith. "We omitted aquatic sites because our interests were focused on terrestrial systems."
This type of study yields important information about large-scale ecosystem phenomenon, as well as lessons in utilizing a large network of research sites. "The cooperation of the information managers and PIs at each site we contacted was invaluable, as well as critical for the success of this project. Their willingness to participate in this synthesis truly facilitated our efforts."
Despite the broad scale of the data and information gathering, the researchers say they encountered few difficulties. "Clearly our lack of familiarity with several of the sites could have been a difficulty," say Knapp and Smith. "but again, local site investigators answered all our questions and provided advice on those data that would be most appropriate for achieving our goals." KNZ researchers Knapp and Smith believe that frequent contact with the site Information Managers and PIs before and during cross-site research projects is essential. "We found the experience rewarding and would strongly encourage others to consider initiating cross-site synthetic studies. Such studies exemplify the value of the LTER network."
"Variation Among Biomes in Temporal Dynamics of Aboveground Primary Production." Knapp, Alan K. and Melinda D. Smith. Science. 921: 481-484.
The article is available on the Science magazine web site. http://www.sciencemag.org/ The dataset is available online at the LTER web site http://www.lternet.edu/anpp/
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