Reading forest history from sediments
Davis studied pollen analysis in Denmark in 1953–1954 and earned her Harvard doctorate in 1957. Sediment layers supplied evidence of vegetation long before modern plot observations.
She connected these records with ecological questions: when particular trees arrived, when their abundance changed and whether different species changed together.
Pollen percentages and vegetation
Plants differ in pollen production and dispersal, so a taxon’s share of sedimentary pollen is not simply its share of the surrounding forest.
Davis compared modern pollen with vegetation and investigated their quantitative relationship. Work on accumulation rates and sediment redistribution also examined how the fossil record itself was formed.
References: [3]
Species followed different pathways
Comparing pollen sequences across sites showed that postglacial forests did not move north as fixed packages of species. Trees differed in arrival times, routes and rates of change.
Later work in Michigan and Wisconsin compared the expansion of hemlock and beech, grounding forest history in particular species and places.
Revisiting a historical decline
A marked hemlock decline around five thousand years ago became another research problem. In 1981 Davis proposed that an outbreak of a specialized pathogen or herbivore could have contributed.
This was a historical explanation rather than an established sole cause. Later evidence also implicated climatic changes, requiring comparison among mechanisms rather than identification of the decline alone.
References: [3]