Sprecher
Beschreibung
The Triassic-Jurassic (T-J) boundary saw global ecological upheaval driven by volcanism, with extremely elevated atmospheric CO2 (>2000 ppm) and temperatures (GMST >24°C). Extensive community turnover and desertification are accompanied by directional changes in heat avoidance leaf traits. We explore the interaction of traits, constrained by fossils (paleo-traits: leaf width (w), maximum stomatal conductance (gs,max) and xylem vulnerability to cavitation-induced embolism (ΨC)) and simulated paleo-climate (HadCM-3B) using a process-based ecosystem model (paleo-BGC). We test whether trait coordination (1) limits forest cover and (2) results in the same pattern of community turnover observed at two well-studied T-J sites.
Simulations reveal that the order of magnitude reduction in leaf size conferred extensive biogeographic and metabolic advantages for taxa with small leaves.
Slowed plant water use due to aridity and changes in stomatal anatomy reinforced the need for other modes of heat avoidance. Simulated maximum T-J leaf temperatures at several CO2 levels are compared to leaf thermal tolerance and acclimation from neo-botany.
Our process-based simulations connect fossil evidence to mechanisms of plant survival known from modern ecosystems to better understand paleo-ecosystems. At the same time the fossil record can increasingly inform better vegetation projections under anthropogenic CO2 emissions scenarios, and clarify our future.