Estimating Biomass in California's Chaparral and Coastal Sage Scrub Shrublands

Despite being one of the most extensive vegetation types in the North American Mediterranean Climate Zone, information on the amount of biomass and carbon stock associated with shrubland vegetation is still largely unknown. Efforts to quantify shrubland biomass through fieldwork consist of either direct measurement using destructive vegetation sampling or indirect measurement through the combined use of stem measurements and allometric equations. Both methods have their own benefits and shortcomings, resulting in substantial variation in how shrubland biomass is reported. Here we aim to provide a comprehensive review and synthesis of available shrubland biomass data from studies based in California to provide a concise and reliable source for natural resource managers. We conducted a literature review of 37 studies published over a span of 72 yrs to compile estimates of aboveground biomass (live, dead, and total), leaf biomass, stem biomass (live, dead, and total), litter biomass, and belowground biomass for three prominent shrubland communities and four shrubland species in the California Floristic Province. Overall aboveground biomass in shrub communities was greatest in mixed chaparral (3461 g/m2), followed by chamise chaparral (2114 g/m2), and coastal sage scrub (1583 g/m2). In each community total aboveground biomass increased with the age of the stand. Leaf, stem, and litter biomass estimates were also highest for mixed chaparral compared to the other communities. Of the four shrub species we summarized biomass data for, Ceanothus greggii A. Gray (Rhamnaceae) had the highest average aboveground biomass, followed by Adenostoma fasciculatum Hook. & Arn. (Rosaceae), Quercus berberidifolia Liebm. (Fagaceae), and C. cuneatus (Hook.) Nutt. By compiling these studies and summarizing the biomass data reported in them, we provide a single resource to characterize the amount of biomass of three different shrublands and four species over their life cycle. This is an essential resource for land managers and practitioners who need field-based biomass and carbon stock figures for monitoring and reporting purposes.