Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 6 1 2009 10.5194/bg-6-129-2009 http://www.biogeosciences.net/6/129/2009/ http://www.biogeosciences.net/6/129/2009/bg-6-129-2009.html http://www.biogeosciences.net/6/129/2009/bg-6-129-2009.pdf 129 138 2009-01-29 Evaluation of satellite based indices for gross primary production estimates in a sparse savanna in the Sudan M. Sjöström martin.sjostrom@nateko.lu.se J. Ardö L. Eklundh B. A. El-Tahir H. A. M. El-Khidir M. Hellström P. Pilesjö J. Seaquist Department of Physical Geography and Ecosystem Analysis, Lund, Sweden Agricultural Research Corporation, El Obeid, Sudan One of the more frequently applied methods for integrating controls on primary production through satellite data is the Light Use Efficiency (LUE) approach. Satellite indices such as the Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI) and the Shortwave Infrared Water Stress Index (SIWSI) have previously shown promise as predictors of primary production in several different environments. In this study, we evaluate NDVI, EVI and SIWSI derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite sensor against in-situ measurements from central Sudan in order to asses their applicability in LUE-based primary production modeling within a water limited environment. Results show a strong correlation between vegetation indices and gross primary production (GPP), demonstrating the significance of vegetation indices for deriving information on primary production with relatively high accuracy at similar areas. Evaluation of SIWSI however, reveal that the fraction of vegetation apparently is to low for the index to provide accurate information on canopy water content, indicating that the use of SIWSI as a predictor of water stress in satellite data-driven primary production modeling in similar semi-arid ecosystems is limited. Asrar, G., Fuchs, M., Kanemasu, E. T., and Hatfield, J. L.: Estimating Absorbed Photosynthetic Radiation and Leaf Area Index from Spectral Reflectance in Wheat, Agron. J., 76, 300–306, 1984. Aubinet, M., Grelle, G., Ibrom, A., Rannik, U., Moncrie, J., Foken, T., Kowalski, A. S., Martin, P. H., Berbigier, P., Bernhofer, C., Clement, R., Elbers, J., Granier, A., Grunwald, T., Morgenstern, K., Pilegaard, K., Rebmann, C., Snijders, W., and Valentini, T. R. V.: Estimates of the annual net carbon and water exchange of European forests: the EUROFLUX methodology, Adv. Ecol. Res., 30, 113–175, 2000. Ceccato, P., Flasse, S., Tarantola, S., Jacquemoud, S., and Gregoire, J. M.: Detecting vegetation leaf water content using reflectance in the optical domain, Remote Sens. Environ., 77, 22–33, 2001. Ceccato, P. and Flasse, S.: Designing a spectral index to estimate vegetation water content from remote sensing data – Part 2. Validation and applications, Remote Sens. Environ., 82, 198–207, 2002. Ceccato, P., Gobron, N., Flasse, S., Pinty, B., and Tarantola, S.: Designing a spectral index to estimate vegetation water content from remote sensing data: Part 1 – Theoretical approach, Remote Sens. Environ., 82, 188–197, 2002. Cheng, Y. B., Zarco-Tejada, P. J., Riano, D., Rueda, C. A., and Ustin, S. L.: Estimating vegetation water content with hyperspectral data for different canopy scenarios: relationships between AVIRIS and MODIS indexes, Remote Sens. Environ., 105, 354–366, doi:10.1016/j.rse.2006.07.005, 2006. Daughtry, C. S. T., Gallo, K. P., and Bauer, M. E.: Spectral estimates of solar radiation intercepted by corn canopies, Agron. J., 75, 527–531, 1983. Eck, T. F. and Dye, D. G.: Satellite estimation of incident photosynthetically active radiation using ultraviolet reflectance, Remote Sens. Environ., 135–146, 1991. Eklundh, L. and Olsson, L.: Vegetation index trends for the African Sahel 1982–1999, Geophys. Res. Lett., 30, 1430, doi:10.1029/2002gl016772, 2003. Fensholt, R. and Sandholt, I.: Derivation of a shortwave infrared water stress index from MODIS near- and shortwave infrared data in a semiarid environment, Remote Sens. Environ., 87, 111–121, doi:10.1016/j.rse.2003.07.002, 2003. Fensholt, R., Sandholt, I., Rasmussen, M. S., Stisen, S., and Diouf, A.: Evaluation of satellite based primary production modelling in the semi-arid Sahel, Remote Sens. Environ., 105, 173–188, doi:10.1016/j.rse.2006.06.011, 2006. Field, C. B., Randerson, J. T., and Malmstrom, C. M.: Global net primary production: combining ecology and remote sensing, Remote Sens. Environ., 51, 74–88, 1995. Friborg, T., Boegh, E., and Soegaard, H.: Carbon dioxide flux, transpiration and light response of millet in the Sahel, J. Hydrol., 188-189, 633–650, 1997. Gao, B. C.: NDWI – A normalized difference water index for remote sensing of vegetation liquid water from space, Remote Sens. Environ., 58, 257–266, 1996. Giles, J.: How to survive a warming world, Nature, 446, 716–717, doi:10.1038/446716a, 2007. Goward, S. N. and Huemmrich, K. F.: Vegetation canopy PAR absorptance and the normalized difference vegetation index: an assessment using the SAIL model, Remote Sens. Environ., 39, 119–140, 1992. Hanan, N. P. and Prince, S. D.: Stomatal conductance of west-central supersite vegetation in HAPEX-Sahel: Measurements and empirical models, J. Hydrol., 189, 536–562, 1997. Hanan, N. P., Kabat, P., Dolman, J. A., and Elbers, J. A.: Photosynthesis and carbon balance of a Sahelian fallow savanna, Global Change Biol., 4, 523–538, 1998. Herrmann, S. M., Anyamba, A., and Tucker, C. J.: Recent trends in vegetation dynamics in the African Sahel and their relationship to climate, Global Environ. Chang., 15, 394–404, doi:10.1016/j.gloenvcha.2005.08.004, 2005. Hickler, T., Eklundh, L., Seaquist, J. W., Smith, B., Ardö, J., Olsson, L., Sykes, M. T., and Sjöström, M.: Precipitation controls Sahel greening trend, Geophys. Res. Lett., 32, doi:10.1029/2005GL024370, 2005. Hilker, T., Coops, N. C., Wulder, M. A., Black, T. A., and Guy, R. D.: The use of remote sensing in light use efficiency based models of gross primary production: A review of current status and future requirements, Sci. Total Environ., 404, 411–423, doi:10.1016/j.scitotenv.2007.11.007, 2008. Houghton, R. A.: Why are estimates of the terrestrial carbon balance so different?, Global Change Biol., 9, 500–509, 2003. Huete, A., Liu, H. Q., and van Leeuwen, W. J. D.: The use of vegetation indices in forested regions: issues of linearity and saturation, Geoscience and Remote Sensing, 1997. IGARSS '97. "Remote Sensing – A Scientific Vision for Sustainable Development", 1997 IEEE International, 4, 1966–1968, 1997. Huete, A., Didan, K., Miura, T., Rodriguez, E. P., Gao, X., and Ferreira, L. G.: Overview of the radiometric and biophysical performance of the MODIS vegetation indices, Remote Sens. Environ., 83, 195–213, 2002. Hulme, M.: Climatic perspectives on Sahelian desiccation: 1973–1998, Global Environ. Chang., 11, 19–29, 2001. IPCC: Summary for policymakers, in: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by: Solomon, S., Qin, D. Manning,, M., Chen, Z., Marquis, M., Averyt, K. B., Tignor, M., and Miller, H. L., Cambridge, UK and New York, NY, USA, 2007. Jönsson, P. and Eklundh, L.: Seasonality extraction by function fitting to time-series of satellite sensor data, IEEE T. Geosci. Remote, 40, 1824–1832, doi:10.1109/TGRS.2002.802519, 2002. Jönsson, P. and Eklundh, L.: TIMESAT – a program for analyzing time-series of satellite sensor data, Comput. Geosci., 833–845, doi:10.1016/j.cageo.2004.05.006, 2004. Justice, C. O., Townshend, J. R. G., Vermote, E. F., Masuoka, E., Wolfe, R. E., Saleous, N., Roy, D. P., and Morisette, J. T.: An overview of MODIS Land data processing and product status, Remote Sens. Environ., 83, 3–15, 2002. Liang, S. L., Zheng, T., Liu, R. G., Fang, H. L., Tsay, S. C., and Running, S.: Estimation of incident photosynthetically active radiation from Moderate Resolution Imaging Spectrometer data, J. Geophys. Res.-Atmos., 111, D15208, doi:10.1029/2005jd006730, 2006. Lloyd, J. and Taylor, J. A.: On the temperature dependence of soil respiration, Funct. Ecol., 8, 315-323, 1994. Miura, T., Huete, A. R., Yoshioka, H., and Holben, B. N.: An error and sensitivity analysis of atmospheric resistant vegetation indices derived from dark target-based atmospheric correction, Remote Sens. Environ., 78, 284–298, 2001. Monteith, J. L.: Solar radiation and productivity in tropical ecosystems, J. Appl. Ecol., 9, 747–766, 1972. Monteith, J. L.: Climate and the efficiency of crop production in Britain, Philosophical Transactions of the Royal Society of London, Series B, Biol. Sci., 281, 277–294, 1977. Nemani, R. R. and Running, S. W.: Estimation of regional surface resistance to evapotranspiration from NDVI and thermal-IR AVHRR data, J. Appl. Meteorol., 28, 276–284, 1989. Olofsson, P., Eklundh, L., Lagergren, F., Jönsson, P., and Lindroth, A.: Estimating net primary production for Scandinavian forests using data from Terra/MODIS, Adv. Space Res., 39, 125–130, doi:10.1016/j.asr.2006.02.031, 2007a. Olofsson, P., Van Laake, P. E., and Eklundh, L.: Estimation of absorbed PAR across Scandinavia from satellite measurements Part I: Incident PAR, Remote Sens. Environ., 110, 252–261, doi:10.1016/j.rse.2007.02.021, 2007b. Olofsson, P., Lagergren, F., Lindroth, A., Lindström, J., Klemedtsson, L., Kutsch, W., and Eklundh, L.: Towards operational remote sensing of forest carbon balance across Northern Europe, Biogeosciences, 5, 817–838, 2008. Prince, S. D. and Goward, S. N.: Global primary production: A remote sensing approach, J. Biogeogr., 22, 815–835, 1995. Rahman, A. F., Sims, D. A., Cordova, V. D., and El-Masri, B. Z.: Potential of MODIS EVI and surface temperature for directly estimating per-pixel ecosystem C fluxes, Geophys. Res. Lett., 32, L19404, doi:10.1029/2005GL024127, 2005. Reichstein, M., Falge, E., Baldocchi, D., Papale, D., Aubinet, M., Berbigier, P., Bernhofer, C., Buchmann, N., Gilmanov, T., Granier, A., Grunwald, T., Havrankova, K., Ilvesniemi, H., Janous, D., Knohl, A., Laurila, T., Lohila, A., Loustau, D., Matteucci, G., Meyers, T., Miglietta, F., Ourcival, J.-M., Pumpanen, J., Rambal, S., Rotenberg, E., Sanz, M., Tenhunen, J., Seufert, G., Vaccari, F., Vesala, T., Yakir, D., and Valentini, R.: On the separation of net ecosystem exchange into assimilation and ecosystem respiration: review and improved algorithm, Global Change Biol., 11, 1424–1439, doi:10.1111/j.1365-2486.2005.001002.x, 2005. Schmid, H. P.: Source areas for scalars and scalar fluxes, Bound.-Layer Meteor., 67, 293–318, 1994. Seaquist, J. W. and Olsson, L.: Rapid estimation of photosynthetically active radiation over the West African Sahel using the Pathfinder Land Data Set, Int. J. Appl. Earth Obs., 1, 205–213, 1999. Seaquist, J. W., Olsson, L., and Ardo, J.: A remote sensing-based primary production model for grassland biomes, Ecol. Model., 169, 131–155, doi:10.1016/S0304-3800(03)00267-9, 2003. Seaquist, J. W., Olsson, L., and Eklundh, L.: Broad-scale increase in NPP quantified for the African Sahel, 1982–1999, Int. J. Remote Sens., 5115–5122, doi:10.1080/01431160600868458, 2006. Sellers, S. J., Tucker, C. J., Collatz, G. J., Los, S. O., Justice, C. O., Dazlich, D. A., and Randall, D. A.: A global 1-degrees by 1-degrees NDVI data set for climate studies. Part 2: The generation of global fields of terrestrial biophysical parameters from the NDVI, Int. J. Remote Sens., 15, 3519–3545, doi:10.1016/j.rse.2005.01.020, 1994. Sims, D. A., Luo, H. Y., Hastings, S., Oechel, W. C., Rahman, A. F., and Gamon, J. A.: Parallel adjustments in vegetation greenness and ecosystem CO₂ exchange in response to drought in a Southern California chaparral ecosystem, Remote Sens. Environ., 103, 289–303, doi:10.1016/j.rse.2005.01.020, 2006a. Sims, D. A., Rahman, A. F., Cordova, V. D., El-Masri, B. Z., Baldocchi, D. D., Flanagan, L. B., Goldstein, A. H., Hollinger, D. Y., Misson, L., Monson, R. K., Oechel, W. C., Schmid, H. P., Wofsy, S. C., and Xu, L. K.: On the use of MODIS EVI to assess gross primary productivity of North American ecosystems, J. Geophys. Res. (G. Biogeosci.), 111, G04015, doi:10.1029/2006JG000162as, 2006b. Sims, D. A., Rahman, A. F., Cordova, V. D., El-Masri, B. Z., Baldocchi, D. D., Bolstad, P. V., Flanagan, L. B., Goldstein, A. H., Hollinger, D. Y., Misson, L., Monson, R. K., Oechel, W. C., Schmid, H. P., Wofsy, S. C., and Xu, L.: A new model of gross primary productivity for North American ecosystems based solely on the enhanced vegetation index and land surface temperature from MODIS, Remote Sens. Environ., 112, 1633–1646, doi:10.1016/j.rse.2007.08.004, 2008. Sitch, S., Smith, B., Prentice, I. C., Arneth, A., Bondeau, A., Cramer, W., Kaplan, J. O., Levis, S., Lucht, W., Sykes, M. T., Thonicke, K., and Venevsky, S.: Evaluation of ecosystem dynamics, plant geography and terrestrial carbon cycling in the LPJ dynamic global vegetation model, Global Change Biol., 9, 161–185, 2003. Tucker, C. J.: Red and photographic infrared linear combinations for monitoring vegetation, Remote Sens. Environ., 8, 127–150, 1979. Tucker, C. J., Vanpraet, C., Boerwinkel, E., and Gaston, A.: Satellite remote sensing of total dry matter production in the Senegalese Sahel, Remote Sens. Environ., 13, 461–474, 1983. Tucker, C. J., Vanpraet, C. L., Sharman, M. J., and Van Ittersum, G.: Satellite remote sensing of total herbaceous biomass production in the Senegalese Sahel: 1980–1984, Remote Sens. Environ., 17, 233–249, 1985. Van Laake, P. E. and Sanchez-Azofeifa, G. A.: Mapping PAR using MODIS atmosphere products, Remote Sens. Environ., 94, 554–563, doi:10.1016/j.rse.2004.11.011, 2005. Vermote, E. F., El Saleous, N. Z., and Justice, C. O.: Atmospheric correction of MODIS data in the visible to middle infrared: first results, Remote Sens. Environ., 83, 97–111, 2002. Wang, Y.-P. and Leuning, R.: A two-leaf model for canopy conductance, photosynthesis and partitioning of available energy I: Model description and comparison with a multi-layered model, Agr. Forest. Meteorol., 91, 89–111, 1998. Wieringa, J.: Representative roughness parameters for homogeneous terrain, Bound.-Layer Meteor., 63, 323–363, 1993. Xiao, X. M., Braswell, B., Zhang, Q., Boles, S., Frolking, S., and Moore, B.: Sensitivity of vegetation indices to atmospheric aerosols: continental-scale observations in Northern Asia, Remote Sens. Environ., 84, 385–392, 2003. Xiao, X. M., Hollinger, D., Aber, J., Goltz, M., Davidson, E. A., Zhang, Q., and Moore, B.: Satellite-based modeling of gross primary production in an evergreen needleleaf forest, Remote Sens. Environ., 89, 519–534, doi:10.1016/j.rse.2003.11.008, 2004.