TY - JOUR
T1 - Variations in the influence of diffuse light on gross primary productivity in temperate ecosystems
AU - Cheng, Susan J.
AU - Bohrer, Gil
AU - Steiner, Allison L.
AU - Hollinger, David Y.
AU - Suyker, Andrew
AU - Phillips, Richard P.
AU - Nadelhoffer, Knute J.
N1 - Funding Information:
We thank the FLUXNET community for their dedicated efforts in collecting and providing quality-controlled eddy covariance data for ecosystem research. We also thank the University of Michigan Center for Statistical Consultation and Research (Dr. Corey Powell and Dr. Kerby Shedden) for input on statistical techniques, Dr. Christoph Vogel for providing updated PAR data for UMBS, and Alex Fotis for early discussions and data organization for this paper. Support for SJC was provided in part by the University of Michigan Graham Sustainability Institute. Funding for data collection at UMBS was provided by the National Science Foundation grant DEB-0911461 , the U.S. Department of Energy's (DOE) Office of Science Biological and Environmental Research (BER) project DE-SC0006708 and AmeriFlux National Core Flux Site award through Lawrence Berkeley National Laboratory contract #7096915 , and National Oceanic and Atmospheric Administration Grant NA11OAR4310190 . Research at the Howland Forest is supported by the DOE's Office of Science BER. The Mead US-Ne1, US-Ne2, and US-Ne3 AmeriFlux sites were supported by the DOE Office of Science (BER; Grant Nos. DE-FG03-00ER62996, DE-FG02-03ER63639, and DE-EE0003149 ), DOE-EPSCoR (Grant No. DE-FG02-00ER45827 ), and NASA NACP (Grant No. NNX08AI75G ). The Morgan Monroe team thanks the Indiana Department of Natural Resources for supporting and hosting the UM-MMS AmeriFlux site, and the U.S. DOE for funding operations through the Terrestrial Ecosystem Science program and the AmeriFlux Management Project.
Publisher Copyright:
© 2014 Elsevier B.V.
PY - 2015/2/5
Y1 - 2015/2/5
N2 - The carbon storage potential of terrestrial ecosystems depends in part on how atmospheric conditions influence the type and amount of surface radiation available for photosynthesis. Diffuse light, resulting from interactions between incident solar radiation and atmospheric aerosols and clouds, has been postulated to increase carbon uptake in terrestrial ecosystems. However, the magnitude of the diffuse light effect is unclear because existing studies use different methods to derive above-canopy diffuse light conditions. We used site-based, above-canopy measurements of diffuse light and gross primary productivity (GPP) from 10 temperate ecosystems (including mixed conifer forests, deciduous broadleaf forests, and croplands) to quantify the GPP variation explained by diffuse photosynthetically active radiation (PAR) and to calculate increases in GPP as a function of diffuse light. Our analyses show that diffuse PAR explained up to 41% of variation in GPP in croplands and up to 17% in forests, independent of direct light levels. Carbon enhancement rates in response to diffuse PAR (calculated after accounting for vapor pressure deficit and air temperature) were also higher in croplands (0.011-0.050μmol CO2 per μmol photons of diffuse PAR) than in forests (0.003-0.018μmol CO2 per μmol photons of diffuse PAR). The amount of variation in GPP and carbon enhancement rate both differed with solar zenith angle and across sites for the same plant functional type. At crop sites, diffuse PAR had the strongest influence and the largest carbon enhancement rate during early mornings and late afternoons when zenith angles were large, with greater enhancement in the afternoons. In forests, diffuse PAR had the strongest influence at small zenith angles, but the largest carbon enhancement rate at large zenith angles, with a trend in ecosystem-specific responses. These results highlight the influence of zenith angle and the role of plant community composition in modifying diffuse light enhancement in terrestrial ecosystems, which will be important in scaling this effect from individual sites to the globe.
AB - The carbon storage potential of terrestrial ecosystems depends in part on how atmospheric conditions influence the type and amount of surface radiation available for photosynthesis. Diffuse light, resulting from interactions between incident solar radiation and atmospheric aerosols and clouds, has been postulated to increase carbon uptake in terrestrial ecosystems. However, the magnitude of the diffuse light effect is unclear because existing studies use different methods to derive above-canopy diffuse light conditions. We used site-based, above-canopy measurements of diffuse light and gross primary productivity (GPP) from 10 temperate ecosystems (including mixed conifer forests, deciduous broadleaf forests, and croplands) to quantify the GPP variation explained by diffuse photosynthetically active radiation (PAR) and to calculate increases in GPP as a function of diffuse light. Our analyses show that diffuse PAR explained up to 41% of variation in GPP in croplands and up to 17% in forests, independent of direct light levels. Carbon enhancement rates in response to diffuse PAR (calculated after accounting for vapor pressure deficit and air temperature) were also higher in croplands (0.011-0.050μmol CO2 per μmol photons of diffuse PAR) than in forests (0.003-0.018μmol CO2 per μmol photons of diffuse PAR). The amount of variation in GPP and carbon enhancement rate both differed with solar zenith angle and across sites for the same plant functional type. At crop sites, diffuse PAR had the strongest influence and the largest carbon enhancement rate during early mornings and late afternoons when zenith angles were large, with greater enhancement in the afternoons. In forests, diffuse PAR had the strongest influence at small zenith angles, but the largest carbon enhancement rate at large zenith angles, with a trend in ecosystem-specific responses. These results highlight the influence of zenith angle and the role of plant community composition in modifying diffuse light enhancement in terrestrial ecosystems, which will be important in scaling this effect from individual sites to the globe.
KW - Carbon cycling
KW - Diffuse PAR
KW - Land-atmosphere interactions
KW - Net ecosystem exchange
UR - http://www.scopus.com/inward/record.url?scp=84913589308&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84913589308&partnerID=8YFLogxK
U2 - 10.1016/j.agrformet.2014.11.002
DO - 10.1016/j.agrformet.2014.11.002
M3 - Article
AN - SCOPUS:84913589308
SN - 0168-1923
VL - 201
SP - 98
EP - 110
JO - Agricultural and Forest Meteorology
JF - Agricultural and Forest Meteorology
ER -