Effects of management and topography on the radiometric responses of a tallgrass prairie
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Authors: C. L. Turner, T. R. Seastedt, M. I. Dyer, T. G. F. Kittel, and D. W. Schimel
Date: 1992
Journal: Journal of Geophysical Research
Volume: 97
Number: D17
Pages: 18855-18866
Summary of Methods: Normalized difference vegetation index (NDVI) of experimental plots that were exposed to different intensities (5, 10, or 20 cm stubble height) and frequencies (0, 1, 3, or 6 times during the growing season) of simulated grazing, and pastures that were grazed were compared in this study. Mowing frequency affected NDVI. After each mowing event NDVI decreased and after regrowth NDVI in plots that were mowed 1 or 3 times had similar NDVI to unmowed plots while NDVI was still lower in plots that were mowed 6 times during the growing season. Mowing intensity also affected NDVI, plots that were not mowed had the greatest NDVI while plots that were defoliated most severely had the lowest NDVI. The effects of mowing experimental plots were similar to the effects of grazing in pastures and in both cases, NDVI was not related to biomass but to percent nitrogen of standing crop. The authors conclude that the use of NDVI to estimate plant productivity and vegetation-atmosphere exchange is complicated by changes in plant characteristics induced by grazing or mowing. Grazing tends to homogenize potential landscape-induced difference in vegetation activity. Factors otherwise useful in estimating plant production, such as burning treatment and soil depth, are not strongly correlated with aboveground biomass or NDVI under grazing conditions.
Article Summary / Main Points: None
Vegetation Types:
MLRA Ecoregions:
Agrovoc Control Words: Riparian zones Rangelands Wildlife
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: normalized difference vegetation index, simulated grazing, prescribed burning, grazing frequency, grazing intensity, defoliation, remote sensing measurements
Annotation: To simulate foliage removal by cattle, for the grazing intensity experiment, the canopy was maintained at a height of 5, 10, or 20 cm above the soil surface or was left unmowed. For the grazing frequency experiment, vegetation was mowed to about 2 cm above the soil surface 0, 1, 3, or 6 times during the 1987 growing season.
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