Data for: Understanding post-fire vegetation recovery in Southern California ecosystems with the aid of pre-fire observations from long term monitoring

Aims Post-fire vegetation recovery is often determined by the similarity
of post-burn with unburned sites due to a lack of in
situ information on pre-fire communities. The inclusion of
pre-fire data can help account for pre-existing differences and explore
recovery also in terms of return to pre-fire conditions. We used long-term
monitoring data in coastal sage scrub and grasslands to: (1) examine
vegetation cover recovery of different functional groups and (2) determine
whether vegetation composition in burned areas has recovered in four years
after fire with burned to unburned and pre- to post-fire comparisons.
Location Orange County, California, USA Methods We analyzed long-term
vegetation monitoring (2007-2021) data from 39 grassland and 58 coastal
sage scrub transects in southern California, including observations before
and after the 2017 Canyon 2 fire. Linear mixed effect models were used to
determine whether forb, grass, and shrub covers differed between burned
and unburned sites while considering the effects of year and repeated
monitoring. We used Canonical Analysis of Principal coordinates (CAP) to
analyze vegetation composition based on burn status and time of sampling.
Results While vegetation cover in grassland recovered quickly, native
vegetation cover in burned coastal sage scrub remained lowered four years
after fire, though forb and non-native grass cover were higher in some
post-fire years. Community composition in burned coastal sage scrub was
still in recovery four years after fire when compared with unburned or
pre-fire composition. Although burned and unburned grassland differed
post-fire in dominant grass species, inclusion of pre-fire data showed
that this was a pre-existing difference. Conclusions Coastal sage scrub
had not recovered pre-fire vegetation cover and composition by four years
after fire, while grassland cover rebounded quickly, albeit with shifts in
composition over time; patterns that were detected only by having pre- and
post-fire data from long-term monitoring efforts.