Changes in Vegetation Associated with Recent Climate Trends in Southern California: A Remote Sensing Approach

Abstract:

California is home to an array of unique ecosystems that act as biodiversity hotspots, habitat, carbon sinks, and natural resources that have been put at risk as a result of climate changes. Ecosystems in Southern California have experienced warming and become more variable in their seasonal precipitation, which has led to vegetation composition shifts.The vegetation communities at Deep Canyon have been studied with intensive field measurements along transects spanning an elevation range of 240 meters to 2570 meters. Such studies identified an up slope vegetation shift and changes in vegetation functional types from 1977 to 2007 that have been attributed to recent climate behavior. We used Landsat Remote Sensing data from 1984-2018 to analyze the structural changes occurring in Southern California mountain vegetation communities at Deep Canyon. For this, we analyzed trends with an array of Remote Sensing indices such as Normalized Difference Moisture Index(NDMI), Normalized Difference Vegetation Index (NDVI), and Near-Infrared Reflectance of vegetation (NIRv). All three indices have shown significant decreases throughout the elevation range during the studied time period. These decreases indicate most communities are suffering from die off and a few at the lower elevations are experiencing compositional changes. It is also evident that vegetation across the whole elevation range has been reacting to a warming trend and droughts that affected the area over the studied time. Elevation seems to be affecting how different groups of vegetation are reacting to recent climatic shifts, and with further analysis we may be able to see if different vegetation groups are behaving uniquely to these changes. If previously documented vegetation shifts continue, the biodiversity and services provided by California’s unique ecosystem will likely decrease.