How many plant species would have existed immediately after the K-PG extinction?

Question

Specifically, what is the best estimate for the minimum number of plant species during the aftermath and recovery period following the K-PG extinction event?

Do we have any idea how low that number got?

Answer 1

Good question.

The fossil record post Cretaceous-Paleogene boundary is much less clear than the animal fossil record. It's basically impossible to give a true value, since there's no way to determine the number of plant species either side of the event, due to the sporadic nature of plant fossilisation.

In contrast to the wide-scale extinctions that occurred in the animal Kingdom, no major plant groups became extinct across the boundary, and the damage primarily occurred at the species level. However, there is a very strong bias towards sites in North America as these are the ones which are the most well preserved.

This is a cross sectional map of the palynological diversity across the K-PG boundary from North Dakota (source).

The average extinction proportion of miospore taxa in North America is around 30% (Nichols, 2002, Nichols and Johnson, 2008) and this is synchronous with a significant drop in gross palynological diversity (Fig. 5). An additional 20–30% of the miospore taxa underwent a statistically significant decline in abundanceThe extinction magnitude was apparently lower within New Zealand assemblages where 15% of pollen and spores species disappeared