To determine the practical usefulness of MODIS products, we sought to establish a relationship betweenMODIS leaf area index (LAI), enhanced vegetation index (EVI), and NDVI and the above-groundherbaceous green biomass in a semi-arid grassland ecosystem. This study focuses on relating theMODIS eight - day composite LAI, and 16 - day composite EVI and NDVI, to direct measures of above -ground biomass generated within the growing season during four time periods in two steps: 1) establish amethodology for converting plot level biomass measurements to a regional scale; and 2) characterize therelationship between selected MODIS land products and spatially scaled - field observations of grasslandvegetation productivity. Field data were collected in the Little Missouri National Grasslands (LMNG) ofwestern North Dakota. This 809,380 ha area is managed primarily by the USDA Forest Service for cattlegrazing, oil and gas leasing, wildlife habitat, and recreational uses (Jensen et al. 2001). Due to their largegeographic expanse and the dominance of federal ownership, the LMNG provided an excellentopportunity for collecting field data and therefore relating MODIS - derived land products to grasslandvegetation. Biomass observations were made during the 2001 growing season at 2,200 plots (473transects) across four time periods, each five days in length, in the LMNG Little Missouri NationalGrasslands (LMNG) of western North Dakota.
MODIS LAI, EVI and NDVI were all closely related to observed biomass. The results of this studypresent a framework for linking small-scale field observations to MODIS LAI, EVI and NDVI while simultaneously providing much needed insight to the relationship between MODIS land products and vegetation productivity. The high correlation between MODIS land products and observed above - ground green biomass proved that MODIS land products are suitable for monitoring grassland vegetation dynamics in northern mixed grass prairie and appear to offer improved capabilities compared with the AVHRR NDVI relationships presented in previous work.
Reeves, M. C., Moreno A. L., Bagne K. E., and Running S. W. 2014. Estimating climatechange effects on net primary production of rangelands in the United States, ClimaticChange , Volume 126, Issue 3--4
Reeves, M. C., Zhao M., and Running S. W. 2006. Applying improved estimates ofMODIS productivity to characterize grassland vegetation dynamics Rangeland Ecology& Management, Volume 59, Number 1, p.1-10
Reeves, M. C., Winslow J. C., and Running S. W. 2001, Mapping Weekly RangelandVegetation Productivity Using MODIS Algorithms Journal of Range Management,Volume 54, p.A90-A105.