The plant fossil record and models of the effects of the Chicxulub impact provide strong evidence for the devastation of forest communities at the K-Pg boundary. Initial disruption came from energy dissipated by the impact blast, leveling trees within a radius of ∼1,500 km, and as intense radiated heat, which may have ignited wildfires on a global scale [29, 30, 31]. This was most likely followed by acid rain resulting from the emission of sulfate-rich vapor [32] and ejection of a large quantity of soot into the atmosphere [33], potentially blocking photosynthetic activity for several years and most likely inducing limited global climate cooling [34, 35, 36, 37]. This phase of suppressed sunlight, notoriously difficult to reconstruct, is supported by the proliferation of saprotrophs thriving on decomposing organic matter [38].
The post-impact recovery of terrestrial plant communities occurred in two phases. The first is marked by the dominance of fern spores in an ∼1-cm-thick interval [39] (Figure 3). Ferns are pioneer re-colonizers of devastated landscapes, and their proliferation represents a classic example of a “disaster flora” composed of taxa capable of rapidly germinating from spores and rhizomes and/or roots. ... The K-Pg fern spike has been identified worldwide and is an indicator of global canopy loss ([14] and references therein). Sedimentation rates based on recent high-resolution radiometric dating of K-Pg bentonites from Montana [40] and the Denver Basin [15] show that establishment of the fern spike occurred within a century of the Chicxulub impact and that the fern spike disaster flora persisted on the order of 1,000 years. This general timescale is corroborated by estimated sedimentation rates from New Zealand (Figure S1). Terrestrial floras were most likely devoid of extensive closed-canopy forests during this phase.
The second phase is marked by the re-establishment of canopy vegetation: the earliest Paleocene marks a change in forest community structure compared to the Cretaceous. Typical earliest Paleocene plant assemblages are characterized by low taxonomic diversity [41, 42, 43] and by a shift of dominance toward new angiosperms and conifers (the disappearance of diverse Cretaceous taxa [K-taxa] and proliferation of Ulmipollenites krempii, Kurtzipites spp., palms [Arecipites spp.], Taxodiaceae, and Pinaceae; Figure 3), long-lived plants that are indicative of modern climax communities [14, 44]. This low-diversity flora persists until the appearance of diversity hotspots ∼1.4 Ma after the K-Pg [45].
Lilliput effect - after mass extinctions, the surviving species are often much smaller that many of their close relatives before the extinction.