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? 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

Answer 1

The K-Pg extinction event led to significant biodiversity loss, including a marked decline in plant species diversity, as shown by fossil pollen analysis.

Step-by-step explanation:

The K-Pg extinction event, also known as the Cretaceous-Paleogene extinction event, is recognized for causing a massive loss of biodiversity, including the extinction of non-avian dinosaurs. This event is estimated to have occurred approximately 66 million years ago, caused by a cataclysmic meteorite impact. While the extinction of animal species, particularly those weighting over 25 kg, is well-documented, the impact on plant diversity is less clear due to the sparse fossil record for plants. However, studies of fossil pollen and spores indicate a significant reduction in plant diversity following the extinction.

Analysis of fossil pollen from sediments located at the K-Pg boundary suggests a marked decline in the number of plant organisms, as evident from the fewer shapes and numbers of pollen grains. The graph indicating this decline points to a reduction in total organisms and a consequent loss of diversity. This is reinforced by research showing that about 30% of miospore taxa in North America underwent extinction, while the extinction magnitude was lower in places like New Zealand, with around 15% loss of pollen and spores species. This information illustrates that although no major plant groups became extinct, there was still a noteworthy species-level decline.

Post-extinction recovery led to environmental changes and the creation of new niches, allowing plant species that survived to adapt and speciate. Thus, a slow recovery and diversification of plant species occurred in the aftermath of the extinction. Overall, such mass extinction events have historically resulted in devastating biodiversity losses, but they have also paved the way for new life forms to evolve and fill the ecological voids left behind.