Eddy covariance measurements of the surface energy balance and carbon dioxide exchange above high-elevation (3,480 m above sea level) alpine tundra located near Niwot Ridge, Colorado, were compared to simultaneous measurements made over an adjacent subalpine forest over two summers and one winter, from June 9, 2007 to July 3, 2008. …
Journal: Biogeochemistry, Volume 95 (1): 61-76 (2009). DOI: 10.1007/s10533-009-9325-9 Sites: US-NR1
The construction and deployment of a portable trace-gas measurement system (TGaMS) is described. The air-collection system (dubbed HYDRA) collects air samples from 18 different locations and was connected to either one or two LI-COR LI-7000 gas analyzers to measure CO2. An in situ “field calibration” method, that uses four calibration …
Journal: Journal Of Atmospheric And Oceanic Technology, Volume 26 (2): 291-316 (2009). DOI: 10.1175/2008JTECHA1080.1 Sites: US-NR1, US-NR2
Considerable research has recently been devoted to understanding biogeochemical processes under winter snow cover, leading to enhanced appreciation of the importance of many winter ecological processes. In this study, a comprehensive investigation of the stable carbon isotope composition (δ13C) of CO2 within a high-elevation subalpine …
Journal: Biogeochemistry, Volume 95 (1): 37-59 (2009). DOI: 10.1007/s10533-008-9233-4 Sites: US-NR1
This study evaluates the potential impact of clouds on ecosystem CO2 and CO2 isotope fluxes (“isofluxes”) in two contrasting ecosystems (a broadleaf deciduous forest and a C4 grassland) in a region for which cloud cover, meteorological, and isotope data are available for driving the isotope‐enabled land surface model (ISOLSM). …
Journal: Journal Of Geophysical Research, Volume 114 (G1): (2009). DOI: http://doi.org/10.1029/2007JG000675 Sites: US-ARM
Characterizing net ecosystem exchanges (NEE) of CO2 and sensible and latent heat fluxes in heterogeneous landscapes is difficult, yet critical given expected changes in climate and land use. We report here a measurement and modeling study designed to improve our understanding of surface to atmosphere gas exchanges under very heterogeneous …
Journal: Journal Of Geophysical Research, Volume 114 (G4): (2009). DOI: http://doi.org/10.1029/2009JG001003 Sites: US-ARM
Journal: Water Resources Research, Volume 45 (4): (2009). DOI: 10.1029/2008WR007045 Sites: US-Rwe
Journal: Agricultural And Forest Meteorology, Volume 149 (9): 1531-1540 (2009). DOI: 10.1016/j.agrformet.2009.04.006 Sites: US-UMB
Journal: Biogeochemistry, Volume 95 (1): 61-76 (2009). DOI: 10.1007/s10533-009-9325-9 Sites: US-NR1, US-NR3, US-NR4
Recent studies have illuminated the process of hydraulic redistribution, defined as the translocation of soil moisture via plant root systems, but the long-term ecohydrologic significance of this process is poorly understood. We investigated hydraulic redistribution (HR) by Prosopis velutina Woot. (velvet mesquite) in an …
Journal: Water Resources Research, Volume 44 (W02440): n/a-n/a (2008). DOI: 10.1029/2007wr006149 Sites: US-SRM
Tundra-atmosphere exchanges of carbon dioxide (CO2) and water vapour were measured near Daring Lake, Northwest Territories in the Canadian Low Arctic for 3 years, 2004–2006. The measurement period spanned late-winter until the end of the growing period. Mean temperatures during the measurement period varied from about …
Journal: Global Change Biology, Volume 14 (4): 740-756 (2008). DOI: 10.1111/j.1365-2486.2007.01529.x Sites: CA-DL1