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Environmental controls on seasonal ecosystem evapotranspiration/potential evapotranspiration ratio as determined by the global eddy flux measurements
Copyright policy )The evapotranspiration / potential evapotranspiration (AET / PET) ratio is traditionally termed as the crop coefficient (Kc) and has been generally used as ecosystem evaporative stress index. In the current hydrology literature, Kc has been widely used as a parameter to estimate crop water demand by water managers but has not been well examined for other types of ecosystems such as forests and other perennial vegetation. Understanding the seasonal dynamics of this variable for all ecosystems is important for projecting the ecohydrological responses to climate change and accurately quantifying water use at watershed to global scales. This study aimed at deriving monthly Kc for multiple vegetation cover types and understanding its environmental controls by analyzing the accumulated global eddy flux (FLUXNET) data. We examined monthly Kc data for seven vegetation covers, including open shrubland (OS), cropland (CRO), grassland (GRA), deciduous broad leaf forest (DBF), evergreen needle leaf forest (ENF), evergreen broad leaf forest (EBF), and mixed forest (MF), across 81 sites. We found that, except for evergreen forests (EBF and ENF), Kc values had large seasonal variation across all land covers. The spatial variability of Kc was well explained by latitude, suggesting site factors are a major control on Kc. Seasonally, Kc increased significantly with precipitation in the summer months, except in EBF. Moreover, leaf area index (LAI) significantly influenced monthly Kc in all land covers, except in EBF. During the peak growing season, forests had the highest Kc values, while croplands (CRO) had the lowest. We developed a series of multivariate linear monthly regression models for Kc by land cover type and season using LAI, site latitude, and monthly precipitation as independent variables. The Kc models are useful for understanding water stress in different ecosystems under climate change and variability as well as for estimating seasonal ET for large areas with mixed land covers.
Microsoft Academic Graph classification: Vegetation FluxNet Land cover Evapotranspiration Eddy covariance Environmental science Crop coefficient Leaf area index Evergreen Hydrology
Library of Congress Subject Headings: lcsh:Technology lcsh:T lcsh:Environmental technology. Sanitary engineering lcsh:TD1-1066 lcsh:Geography. Anthropology. Recreation lcsh:G lcsh:Environmental sciences lcsh:GE1-350
Microsoft Academic Graph classification: Vegetation FluxNet Land cover Evapotranspiration Eddy covariance Environmental science Crop coefficient Leaf area index Evergreen Hydrology
Library of Congress Subject Headings: lcsh:Technology lcsh:T lcsh:Environmental technology. Sanitary engineering lcsh:TD1-1066 lcsh:Geography. Anthropology. Recreation lcsh:G lcsh:Environmental sciences lcsh:GE1-350
- US Forest Service United States
- Nanjing University China (People's Republic of)
- North Carolina State University United States
- Nanjing University of Information Science and Technology China (People's Republic of)
- North Carolina Agricultural and Technical State University United States
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Abrisqueta, I., Abrisqueta, J. M., Tapia, L. M., Munguía, J. P., Conejero, W., Vera, J., and Ruiz-Sánchez, M. C.: Basal crop coefficients for early-season peach trees, Agr. Water Manage., 121, 158-163, doi:10.1016/j.agwat.2013.02.001, 2013.
Alberto, M. C. R., Quilty, J. R., Buresh, R. J., Wassmann, R., Haidar, S., Correa, T. Q., and Sandro, J. M.: Actual evapotranspiration and dual crop coefficients for dry-seeded rice and hybrid maize grown with overhead sprinkler irrigation, Agr. Water Manage., 136, 1-12, doi:10.1016/j.agwat.2014.01.005, 2014.
Allen, R. G. and Pereira, L. S.: Estimating crop coefficients from fraction of ground cover and height, Irrigation Sci., 28, 17-34, doi:10.1007/s00271-009-0182-z, 2009. [OpenAIRE]
Allen, R. G., Pereira, L. S., Raes, D., and Smith, M.: Crop evapotranspiration, FAO irrigation and drainage paper, No. 56, 1998.
Allen, R. G., Pruitt, W. O., Wright, J. L., Howell, T. A., Ventura, F., Snyder, R., Itenfisu, D., Steduto, P., Berengena, J., Yrisarry, J. B., Smith, M., Pereira, L. S., Raes, D., Perrier, A., Alves, I., Walter, I., and Elliott, R.: A recommendation on standardized surface resistance for hourly calculation of reference ETo by the FAO56 Penman-Monteith method, Agr. Water Manage., 81, 1- 22, doi:10.1016/j.agwat.2005.03.007, 2006.
Allen, R. G., Pereira, L. S., Howell, T. A., and Jensen, M. E.: Evapotranspiration information reporting: I. Factors governing measurement accuracy, Agr. Water Manage., 98, 899-920, doi:10.1016/j.agwat.2010.12.015, 2011.
Anda, A., Silva, J. A. T. D., and Soos, G.: Evapotranspiration and crop coefficient of common reed at the surroundings of Lake Balaton, Hungary, Aquat. Botany, 116, 53-59, doi:10.1016/j.aquabot.2014.01.008, 2014.
Anderson, M. C., Allen, R. G., Morse, A., and Kustas, W. P.: Use of Landsat thermal imagery in monitoring evapotranspiration and managing water resources, Remote Sens. Environ., 122, 50-65, 2012.
Baldocchi, D., Falge, E., Gu, L., Olson, R., Hollinger, D., Running, S., Anthoni, P., Bernhofer, C., Davis, K., and Evans, R.: FLUXNET: A new tool to study the temporal and spatial variability of ecosystem-scale carbon dioxide, water vapor, and energy flux densities, B. Am. Meteorol. Soc., 82, 2415-2434, 2001.
Baldocchi, D. D. and Ryu, Y.: A synthesis of forest evaporation fluxes - from days to years - as measured with eddy covariance, in: Forest Hydrology and Biogeochemistry, Springer, 101-116, 2011.
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- US Forest Service United States
- Nanjing University China (People's Republic of)
- North Carolina State University United States
- Nanjing University of Information Science and Technology China (People's Republic of)
- North Carolina Agricultural and Technical State University United States
- South Carolina State University United States
The evapotranspiration / potential evapotranspiration (AET / PET) ratio is traditionally termed as the crop coefficient (Kc) and has been generally used as ecosystem evaporative stress index. In the current hydrology literature, Kc has been widely used as a parameter to estimate crop water demand by water managers but has not been well examined for other types of ecosystems such as forests and other perennial vegetation. Understanding the seasonal dynamics of this variable for all ecosystems is important for projecting the ecohydrological responses to climate change and accurately quantifying water use at watershed to global scales. This study aimed at deriving monthly Kc for multiple vegetation cover types and understanding its environmental controls by analyzing the accumulated global eddy flux (FLUXNET) data. We examined monthly Kc data for seven vegetation covers, including open shrubland (OS), cropland (CRO), grassland (GRA), deciduous broad leaf forest (DBF), evergreen needle leaf forest (ENF), evergreen broad leaf forest (EBF), and mixed forest (MF), across 81 sites. We found that, except for evergreen forests (EBF and ENF), Kc values had large seasonal variation across all land covers. The spatial variability of Kc was well explained by latitude, suggesting site factors are a major control on Kc. Seasonally, Kc increased significantly with precipitation in the summer months, except in EBF. Moreover, leaf area index (LAI) significantly influenced monthly Kc in all land covers, except in EBF. During the peak growing season, forests had the highest Kc values, while croplands (CRO) had the lowest. We developed a series of multivariate linear monthly regression models for Kc by land cover type and season using LAI, site latitude, and monthly precipitation as independent variables. The Kc models are useful for understanding water stress in different ecosystems under climate change and variability as well as for estimating seasonal ET for large areas with mixed land covers.