Spatial connectivity and revegetation dynamics in fallowed agricultural land, Kern County, CA Background/Question/Methods Abandoned agricultural land is an increasingly common land cover in developed and developing countries. Yet, whether abandoned land acts as a benefit to biodiversity and ecosystem services is largely unknown and likely dependent on the succession trajectory of revegetation. Here I leverage a combination of satellite and survey data to first map revegetation trajectories for a wide range of fallowed fields in Kern County, CA, over the period 2000-present, and second to determine the drivers of revegetation on recently (~10y) abandoned agriculture. This analysis incorporates farmer-reported fallowed status, crop type, pesticide use reports, and crop-averaged fertilizer use, and explores potential relationships between environmental and anthropogenic predictors and revegetation outcomes. I also use evapotranspiration models, including from the novel ECOSTRESS sensor, to explore impacts on the surface energy balance and water cycle. I examine spatiotemporal patterns of fallowing associated with the historic 2011-2017 drought in particular detail, in the context of anticipated fallowing due to upcoming implementation of groundwater pumping restrictions. Results/Conclusions I observe a minor uptick in total annual fallowed field area, coinciding with the 2014 passage of SGMA. An unambiguous, statistically significant trend of increasing total fallowed area precedes the drought, dating back to at least 2007. 2012-2016, the most severe drought years, unexpectedly deviate from the decadal trend by having anomalously low total fallowed area. This anomaly terminates in a large (~7500 ha) increase in fallowed area from 2016 to 2017. Change distributions in clusters of fallowed fields of different areas are quantified. The 2000-2011-2017 increase in fallowed area was strongly skewed toward low (5 to 50 ha) and moderate (50 to 200 ha) cluster sizes, with minimal change observed in sizes of the largest clusters. Small to moderate sized clusters were skewed toward the eastern and the largest clusters were skewed toward the western portion of the study area, consistent with land ownership patterns. Fallowed fields showed increases in radiometric temperature and decreases in ET relative to cultivated fields. In some cases, these differences were observed to extend into “neighbor effects” on adjacent cultivated land. Fields previously hosting perennial (orchard/grape) crops were observed to show greater vegetation abundance and more complex phenology than fields which previously hosted annual row crops. These results provide context for potential impacts of >750,000 acres expected to be fallowed across the California Central Valley to meet SMGA requirements.
