Plant carbon balance, evolutionary innovation and extinction in land plants

The plant fossil record was reviewed to highlight how consideration of plan t carbon balance strengthens our understanding of various evolutionary inno vation and extinction events. Following a brief physiological primer to car bon acquisition and allocation in C3-plants, specific evolutionary events a re discussed in connection with postulated carbon-based mechanisms. Primary topics include: (i) the evolution of plants with the C4-photosynthetic pat hway; (ii) the surprising lack of plant extinctions during the Pleistocene (1.6 million years ago, Ma); (iii) the trend toward declining plant diversi ty and increasing: rates of herbivory across the Palaeocene/Eocene transiti on (57-52 Ma); and (iv) megaherbivore extinctions at the end of the Pleisto cene (10 thousand years ago, Ka). A framework is presented for testing hypo theses on the cause-effect relationships between global carbon cycling, pla nt carbon dynamics and the evolution of terrestrial ecosystems.