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Data for: Long-term drought reduces wildfire severity and promotes invasive species

Kimball, Sarah1

Published Jan 08, 2024 on Dryad. https://doi.org/10.7280/D10M6S

Data files

Jan 08, 2024 version files 43.43 KB

Abstract

Anthropogenic climate change has increased the frequency of extreme drought, wildfires, and invasions of non-native species. Studying interactions amongst these multiple stressors is rarely done at the local scale yet is key to anticipating impacts on vulnerable ecosystems. We leveraged an existing experimental rainfall manipulation to evaluate the relationship between precipitation, fuel load, and fire severity in a Southern California coastal sage scrub system. We asked whether pre-fire rainfall manipulation influenced fuel load and vegetation cover with consequences for fire severity and post-fire community composition. We measured plant biomass and community composition before and after the 2020 Santiago wildfire in experimental plots with three rainfall treatments. After fire, we measured number of branches, diameter of the smallest terminal branch, leaf percent cover, and height on three dominant native shrub species (Malosma laurina, Artemisia californica, and Salvia mellifera) to assess fire severity. Native shrubs had greater pre-fire cover in added water plots compared to reduced water plots. Experimental drought led to less fuel build-up, less native shrub cover, and more invasive grass cover. The decreased biomass led to lower fire severity indicated by smaller branch diameters and more terminal branches after burning. Post-fire shrub cover was low in all plots, and lowest in added and ambient plots compared to reduced water plots. There were fewer native and more invasive species in post-fire droughted plots compared to post-fire irrigated and ambient water plots. Our results demonstrate the importance of fuel load to fire severity and plant community composition on an ecosystem scale. Management strategies should focus on reducing fire frequency to maintain the resilience of coastal sage scrub communities facing drought. Control burns are not recommended for coastal sage scrub communities because they will promote the growth of non-native plants.