Potter, C (2020). Snowmelt timing impacts on growing season phenology in the northern range of Yellowstone National Park estimated from MODIS satellite data. LANDSCAPE ECOLOGY, 35(2), 373-388.

Context Trends and geographic patterns of change in vegetation phenology metrics and snowmelt timing from the MODerate resolution Imaging Spectroradiometer (MODIS) satellite data sets were analyzed for the Northern Range of Yellowstone National Park over the period 2001 to 2017. Objectives The main question posed in this analysis was "Where has the growing season length, amplitude, and integrated greenness cover changed over the past two decades on the Northern Range, particularly in relation to vegetation cover types and the timing of spring snowmelt?" Methods Phenology metric patterns derived from the Normalized Difference Vegetation Index (NDVI) time-series at 250-m resolution were used to track changes in the growing season length, amplitude, and integrated greenness cover over the past two decades. Results Trend analysis showed that end of the growing season timing (EOST) and integrated greenness increased significantly over nearly 30% of the Northern Range study area, and NDVI amplitude increased significantly in several large drainages, particularly in shrub-grassland cover types. Significant variation in the start of the growing season (SOST), NDVI amplitude and integrated greenness could be further explained by the timing of spring snow melt. In years with relatively late snowmelt dates (after mid-May), higher plant growth was observed over the ensuing growing season, as captured in the amplitude and integrated greenness metrics, potentially due to elevated snow water inputs that can maintain available soil moisture levels for plant growth into the mid- and late-summer months. Conclusions The ecological implications of an extended period in November-December when grassland and shrub biomass supplies remain relatively snow-free and readily accessible to grazing ungulates will require further assessments.