Network of networks: Time series clustering of ameriflux sites

Environmental observation networks, such as AmeriFlux, are foundational for monitoring ecosystem response to climate change, management practices, and natural disturbances; however, their effectiveness depends on their representativeness for the regions or continents. We proposed an empirical, time series approach to quantify the similarity of ecosystem fluxes across AmeriFlux sites. We extracted the diel and seasonal characteristics (i.e., amplitudes, phases) from carbon dioxide, water vapor, energy, and momentum fluxes, which reflect the effects of climate, plant phenology, and ecophysiology on the observations, and explored the potential aggregations of AmeriFlux sites through hierarchical clustering. While net radiation and temperature showed latitudinal clus­ tering as expected, flux variables revealed a more uneven clustering with many small (number of sites < 5), unique groups and a few large (> 100) to intermediate (15–70) groups, highlighting the significant ecological regulations of ecosystem fluxes. Many identified unique groups were from under-sampled ecoregions and biome types of the International Geosphere-Biosphere Programme (IGBP), with distinct flux dynamics compared to the rest of the network. At the finer spatial scale, local topography, disturbance, management, edaphic, and hy­ drological regimes further enlarge the difference in flux dynamics within the groups. Nonetheless, our clustering approach is a data-driven method to interpret the AmeriFlux network, informing future cross-site syntheses, upscaling, and model-data benchmarking research. Finally, we highlighted the unique and underrepresented sites in the AmeriFlux network, which were found mainly in Hawaii and Latin America, mountains, and at undersampled IGBP types (e.g., urban, open water), motivating the incorporation of new/unregistered sites from these groups.

Instituto de Clima y Agua

Fil: Reed, David E. Yale University. Yale School of the Environment; Estados Unidos. University of Science and Arts of Oklahoma. Division of Science & Physical Education; Estados Unidos. Michigan State University. Department of Geography, Environment & Spatial Sciences; Estados Unidos

Fil: Chun, Housen. Climate and Ecosystem Sciences Division. Lawrence Berkeley National Lab; Estados Unidos

Fil: Peter, Brad G. University of Arkansas. Department of Geosciences; Estados Unidos

Fil: Chen, Jiquan. Michigan State University. Department of Geography, Environment & Spatial Sciences; Estados Unidos. Michigan State University. Center for Global Change and Earth Observations; Estados Unidos

Fil: Abraha, Michael. Michigan State University. Center for Global Change and Earth Observations; Estados Unidos.

Fil: Amiro, Brian. University of Manitoba. Department of Soil Science; Canadá

Fil: Anderson, Ray G.USDA-Agricultural Research Service. US Salinity Laboratory. Agricultural Water Efficiency and Salinity Research Unit; Estados Unidos

Fil: Arain, M. Altaf. McMaster University. School of Earth, Environment and Society; Canadá

Fil: Arruda, Paulo. Universidade Federal de Mato Grosso. Programa de Pos-Graduaçao em Física Ambiental; Brasil

Fil: Barron - Gafford, Greg A. University of Arizona. School of Geography, Development, & Environment; Estados Unidos

Fil: Bernacchi, Carl. USDA Agricultural Research Service. Global Change and Photosynthesis Research Unit; Estados Unidos

Fil: Beverly, Daniel P. University of Indiana. Paul O’Neill School of Public and Environmental Affairs; Estados Unidos

Fil: Biraud, Sebastien C. Climate and Ecosystem Sciences Division. Lawrence Berkeley National Lab; Estados Unidos

Fil: Black, T. Andrew. University of British Columbia. Faculty of Land and Food Systems; Canadá

Fil: Blanken, Peter D. Univesity of Colorado. Department of Geography; Estados Unidos

Fil: Bohrer, Gil. The Ohio State University. Department of Civil, Environmental & Geodetic Engineering; Estados Unidos

Fil: Bowler, Rebecca. British Columbia Ministry of Forests; Canadá

Fil: Bowling, David R. The University of Utah. School of Biological Sciences; Estados Unidos

Fil: Forsythe, Brandon R. Yale University. Yale School of the Environment; Estados Unidos. University of Arkansas. Department of Geosciences; Estados Unidos

Fil: Posse Beaulieu, Gabriela. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Clima y Agua; Argentina

Fil: Zona, Donatella. San Diego State University. Department of Biology; Estados Unidos