Identifying Drivers of Shrubland Biomass in Southern California

Abstract

Aim

The drivers of shrubland biomass in the Mediterranean-Climate Region of southern California are not well understood. We aim to fill a critical information gap for resource managers of shrub-dominated landscapes who need to estimate shrub recovery post-fire, track and monitor carbon storage and sequestration, and determine the tradeoff in restoration goals between prioritising carbon storage and species richness.

Location

Southern California, USA.

Methods

Using data from 143 field plots located in 11 fire scars (ranging from 1 to 12 years old), we used Linear Mixed Models to assess the contribution of temporal and environmental variables, along with post-fire regeneration strategies of shrub species to explain patterns of aboveground shrub biomass.

Results

We identified four key findings: (1) shrub biomass increased with time since last fire and the proportion of resprouting species, and decreased with distance to coast and solar radiation; (2) species with the ability to resprout (obligate resprouter and facultative seeders) contributed greater biomass at all post-fire time periods and locations when compared with obligate seeders; (3) we found higher average biomass contributed by both obligate seeder and obligate resprouter species in plots closer to the coast than interior plots; and (4) fourth, we found a significant positive relationship between woody shrub species richness and biomass.

Conclusions

The findings of this study of biomass at a regional scale and using shrublands of multiple stand ages can help support natural resource management decision-making for shrub-dominated landscapes—including estimating biomass recovery post-fire, quantifying carbon storage and setting goals for shrubland restoration.