Models and macrofossils: integrating Rancho La Brea's plant collection with dynamic vegetation modeling during Marine Isotope Stage 3

The La Brea Food Webs project aims to understand the community structure and species interactions before the Last Glacial Maximum (LGM) at Rancho La Brea, Southern California. Historically, excavation and research have focused on extinct mega-carnivore remains, and thus the upper trophic levels. Project 23 excavations now allow careful study of plant and small mammal remains to better develop a picture of community structure during Marine Isotope Stage 3 (MIS 3). These fossil data are integrated with two models that aim to 1) develop vegetation cover scenarios for the Los Angeles Basin, and 2) investigate food web structure, response and resilience.

LPJ-GUESS models plant community process and function, using paleoclimate data and plant functional types (PFT) as inputs. Taxa identified in the fossil record inform PFT parameterization. Outputs include plants' relative abundance on the landscape, leaf area index, and net primary productivity in the Los Angeles Basin from 50 - 35 ka. Macrofossil identification to date suggests an open juniper-oak woodland from 43 - 35 ka, with diverse herbaceous cover and possible no-analog communities. These plant community data inform the dynamic food web models, and offer insight to local climate conditions. Fossil pollen data from other Southern California records show that MIS 3 - MIS 2 plant communities strongly reflect regional hydroclimate, a phenomenon observed in Mediterranean ecoregions across space and time.

This project will assess how communities responded to baseline climate variability before the major perturbations that impacted Southern California during the LGM. It also offers insight to how well food web structure can predict extinction risk.