Meteorite That Doomed Dinosaurs Remade Forests

Sep 23, 2014

By Daniel Stolte

The meteorite impact that spelled doom for the dinosaurs 66 million years ago decimated the evergreens among the flowering plants to a much greater extent than their deciduous peers, according to a study led by UA researchers. The results are published in the journal PLoS Biology.

Applying biomechanical formulas to a treasure trove of thousands of fossilized leaves of angiosperms  — flowering plants excluding conifers — the team was able to reconstruct the ecology of a diverse plant community thriving during a 2.2 million-year period spanning the cataclysmic impact event, believed to have wiped out more than half of plant species living at the time.

The researchers found evidence that after the event, fast-growing, deciduous angiosperms had replaced their slow-growing, evergreen peers to a large extent. Living examples of evergreen angiosperms, such as holly and ivy, tend to prefer shade, don’t grow very fast and sport dark-colored leaves.

“When you look at forests around the world today, you don’t see many forests dominated by evergreen flowering plants,” said the study’s lead author, Benjamin Blonder, who graduated last year from the lab of UA Professor Brian Enquist with a Ph.D. from the UA’s Department of Ecology and Evolutionary Biology and is now the science coordinator at the UA SkySchool. “Instead, they are dominated by deciduous species, plants that lose their leaves at some point during the year.”

Read more here.

2 comments on “Meteorite That Doomed Dinosaurs Remade Forests

  • @OP link – “Our study provides evidence of a dramatic shift from slow-growing plants to fast-growing species,” he said. “This tells us that the extinction was not random, and the way in which a plant acquires resources predicts how it can respond to a major disturbance. And potentially this also tells us why we find that modern forests are generally deciduous and not evergreen.”

    This is basic ecology.
    When mature forests are cleared, the rapid colonisers move in to fill the void niche, and they start a new succession progressing towards a new stable system with dominant species.

    If there is a rapid succession of disasters/clearances/climate changes, the previously dominant species – adapted to grow from seed in a forest environment will not compete with species (referred to by humans as “weeds”), which invade vacant ground.

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  • The initial colonisation seems to have been by ferns:-

    North American land plants were devastated from Alberta to New Mexico at the K-T boundary. The sediments below the boundary are dominated by angiosperm pollen, but the boundary itself has little or no angiosperm pollen and instead is dominated by fern spores in a spore spike analogous to the iridium spike (Figure 18.7). Normal pollen counts occur immediately after the boundary layer. The spore spike therefore coincides precisely with the iridium spike in time and is equally intense and short-lived.
    The spore spike could be explained by a short but severe crisis for land plants, generated by an impact or an eruption, in which all adult leaves died off for lack of light, or in a prolonged frost, or in acid rain. Perhaps ferns were the first plants to recolonize the debris, and higher plants returned later. This happened after the eruption of Krakatau in 1883. Ferns quickly grew on the devastated island surfaces, presumably from windblown spores, but they in turn were replaced within a few decades by flowering plants as a full flora was reestablished.

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