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Dryad

Oak woodland health assessment in Orange County metrics

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Jun 20, 2021 version files 376.74 KB

Abstract

Oak woodlands are declining in Orange County (OC) due to habitat destruction and climate change, along with increased drought and weather extremes, fire frequency, and the recent invasion by goldspotted oak borers (GSOB). The Center for Environmental Biology (CEB) has been conducting a long-term oak woodland health monitoring program in OC for the goals of restoration. In this project, we analyzed oak monitoring data on demographics and pathogens collected from 2010 to 2020 and incorporated fire frequency and GSOB data to create a health-based oak woodland ranking system to make recommendations for restoration. Here we show our three-level recommendations of restoration priority: 1) Level 1: Blind Canyon (BLI) and Boy Scout Camp (BSC); 2) Level 2: Limestone Canyon (LSC) and Oak Flat (OF); 3) Level 3: Fremont Canyon (FMC), Gypsum Canyon (GYP), and Irvine Mesa (IRM). Increased fire frequency was positively correlated with declining health. We also assessed remote sensing data (Normalized Difference Vegetation Index, NDVI) against on the ground data for its potential to identify declining oak woodlands. NDVI was an imperfect indicator of declining oak woodland health, but may be useful for larger woodlands or with improved imagery resolution. Our work will inform local stakeholders in future restoration projects of OC oak woodlands.