Using the Landsat Archive to Understand and Assess Changes in Mountain Meadow Vegetation

Mountain meadow ecosystems are highly productive and have unique hydrologic, vegetative, and soil characteristics. The mountain meadow ecosystems of the Sierra Nevada have been impacted by drought, climate change, and local and regional development, in some cases leading to conifer encroachment and degradation of riparian habitat. Understanding and addressing this degradation presents management challenges on a regional scale. With recent advances in cloud computing, it is now possible to access and analyze remotely sensed data at high spatial and temporal resolution. Here we use the Landsat archive to develop a robust and repeatable analysis to identify trends in meadow vegetation throughout the Lake Tahoe Basin. We use spatially and temporally averaged normalized difference vegetation index (NDVI) as an annual indicator of the state of the meadow for the duration of the Landsat archive (1985 - 2018). Using a multi-variate regression, we develop a basin-wide relationship between meteorological data, geomorphic characteristics, and other remotely sensed data. The basin-wide data set, which comprises 353 different meadows, minimizes the impacts of transient signals like wildfires or restoration work. After controlling for the natural variability across the basin, we examine the residuals of this regression on a meadow-by-meadow basis to identify both long-term trends in meadow condition and transient impacts, such as fire or restoration work.