Project Summary
To determine the practical usefulness of MODIS products, we sought to establish a relationship between MODIS leaf area index (LAI), enhanced vegetation index (EVI), and NDVI and the above-ground herbaceous green biomass in a semi-arid grassland ecosystem. This study focuses on relating the MODIS 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 a methodology for converting plot level biomass measurements to a regional scale; and 2) characterize the relationship between selected MODIS land products and spatially scaled - field observations of grassland vegetation productivity. Field data were collected in the Little Missouri National Grasslands (LMNG) of western North Dakota. This 809,380 ha area is managed primarily by the USDA Forest Service for cattle grazing, oil and gas leasing, wildlife habitat, and recreational uses (Jensen et al. 2001). Due to their large geographic expanse and the dominance of federal ownership, the LMNG provided an excellent opportunity for collecting field data and therefore relating MODIS - derived land products to grassland vegetation. 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 National Grasslands (LMNG) of western North Dakota.
Results
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.
Publications
Reeves, M. C., Moreno A. L., Bagne K. E., and Running S. W. 2014. Estimating climate change 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.