Impacts of Coastal Scrub Canopy Cover on Drought Resilience in Perennial Grass, Stipa Pulchra

California's coastal grasslands host roughly 90% of the state's rare and endangered life, and 40% of the state's native vegetation. These systems are both an important carbon sink, and a valuable natural and cultural resource. Over the past 150 years, native grasslands have waned in an absence of historic disturbances such as herbivory and fire. Disturbance was essential to preserving and creating these habitats, by reducing encroachment by woody plants, primarily Baccharis pilularis (coyote scrub-brush). Today, added pressure from invasive species only aggravated native grassland decline. To maintain open grasslands, state land managers regularly employ mechanical methods to prevent conversion of grasslands into scrub-brush and forest dominant systems. While attention has focused on scrub-brush's impact on the physical dimension of meadows, limited attention has been paid to the impact of these woody plants on abundance and richness of native and introduced grasses and forbs. In fact, native components of these grasslands—the bunchgrass and forbs—occur in far greater abundance at the interface with woody plant communities, where native grasses often outnumbered invasive competitors by as much as 30%. I characterized the physiological effects of B. pilularis canopy on native perennial grass, Stipa pulchra, by monitoring Leaf Water Content in 70 individuals across 2021-2022. I also investigated how scrub canopies could alter microclimates to facilitate drought relief for native grassland species, by monitoring average wind-speeds, humidity and temperature at each plant. Soil temperature was used as a proxy for daily irradiation. During the driest part of the year, plants in scrub understory grew in soil on average 40°C cooler than grasses growing in exposed regions. These sheltered grasses also showed 60% higher LWC. Tracking the rate of water-loss and greenness (via NDVI) in S. pulchra, we find a correlation between canopy cover and retention of photosynthetically active tissue year-round. This data suggests the benefits of woody plants in moderating drought stress among native species and possible resiliency for these species in a warmer, drier California.