## 1 Introduction
The Moderate Resolution Imaging Spectroradiometer (MODIS) provides great opportunities to monitor vegetation changes in shrubland/grassland ecosystems. Although MODIS has coarser spatial resolution (two bands at 250 m resolution in addition to other coarser resolution bands) than Landsat (multiple bands at 30 m resolution), it has daily monitoring capability and a suite of products available for use. These MODIS products have had atmospheric corrections and cloud screening applied [9], and the data can be used to monitor changes in near-real time. Although many studies have used MODIS products to monitor various vegetation dynamics such as the changes in vegetation phenology, biomass, and fuel moisture [10, 11, 12, 13, 14], only few of them have investigated the use of MODIS products forassessing fuel loads [15; 16; 17]. Live fuel is defined as the live vegetative biomass above the ground in which the seasonal moisture content cycle is controlled largely by internal physiological mechanisms, rather than by external weather influences [8]. Given the close correlations between live fuel loads and live vegetation biomass, it is reasonable that we can estimate the changes in live fuel load using MODIS products. Compared to LANDFIRE fuel data that lacks temporal resolution, MODIS offers the advantages of a harmonized, long-term, and spatially extensive record to observe dynamic living fuel loads. Recent advances in remote sensing applications and meta-analyses allow development of dynamic live fuel loads at broad spatial and temporal scales. One challenge of using remote sensing data for fuel load studies is the estimation of the dynamics of dead fuel loads. Dead fuel loads include the dead leaves and branches on the ground or standing within the live vegetation and contribute significantly to fire behavior and hazards. No existing remote sensing products directly estimate these dead components. With certain information of ecological processes such as mortality, turnover, and decomposition, it should be possible to assess the changes in dead fuel loads separately from the changes in live fuel loads. Ecological models, which have been developed to describe these ecological processes, can be used with remote sensing observations to produce estimates of the dynamics of dead fuel loads. In this study, we first used the weekly composited Normalized Difference Vegetation Index (NDVI) data from an \"expedited\" MODIS (eMODIS) that [18] processed to demonstrate the degree that aboveground live fuel loads change within and between years for a typical sagebrush-dominated shrubland/grassland ecosystem in the western United States. We also used the MODIS Net Primary Production (NPP) product to estimate the changes in live and dead fuel loads for multiple years. Finally, we simulated the fire behavior changes based on the estimates of live and dead fuel loads from MODIS NPP. Our goals include quantifying the range of intra- and interannual variability in the fuel loads of the shrubland/grassland ecosystem, and assessing how the variability in fuel loads affects fire spread simulations. In this study we will use the terms \"fuel load\" and \"biomass\" largely synonymously, with \"fuel load\" mostly in the discussion of fire models and fire risk, and \"biomass\" mostly in the discussion of mapping results and vegetation growth.