Written by John Birks, Professor Emeritus in quantitative palaeoecology and ecology at the Bjerknes Centre and the Department of Biological Sciences at the University of Bergen.
What is Quaternary botany?
Quaternary (last 2.6 million years) botany involves studying plant megafossils (e.g. tree stumps), macrofossils (e.g. seeds, leaves), and microfossils (e.g. pollen, spores) preserved in peat bogs and lake sediments. Although megafossils and macrofossils have been studied since the late 18th century, Quaternary botany today is largely dominated by pollen analysis.
Pollen analysis as we know it today began in July 1916 when the Swedish geologist Lennart von Post gave his classic lecture on forest tree pollen in south Swedish peat deposits at the 16th Scandinavian Meeting of Natural Scientists in Kristiania (now Oslo). The use of the technique spread rapidly and was primarily used as a geological tool for correlation, reconstructing forest and climate history, and relative dating of archaeological finds, sea-level changes, and peat stratigraphical changes.
A major turning point in the development of Quaternary botany was the Baltic Course on pollen analysis led by von Post. Nearly all the participants were young geologists from the Baltic countries, except for two botanists – Knut Fægri from Bergen and Johannes Iversen from Copenhagen. They had recently defended their doctoral theses on dynamics and functional plant ecology, respectively. Despite very different personalities, they became life-long friends.
During the 1933 course they decided to write a short monograph about pollen analysis not as a geological relative dating tool, but on how it could become an ecological tool for studying long-term vegetation dynamics and human impact on vegetation and for providing a factual basis for plant geography. Their monograph, Text-book of Modern Pollen Analysis, appeared in 1950 and it led to a shift towards more ecologically based research in Quaternary botany.
Quaternary botany today is a combination of pollen analysis and related techniques, some macrofossil analyses, and a few megafossil studies. It is currently expanding to include ancient-DNA and other biomarker approaches.
What is the paper about?
This large paper (124 pages of text, 77 pages of references, 28 figures, 27 tables, 6 supplementary text boxes) attempts to review some of the contributions Quaternary botany has made to modern plant ecology and biogeography. It does not provide reviews about Quaternary floristic and vegetational history as there are already many such reviews ranging from global, equatorial, continental, to country studies. The aim of my paper is to provide a coherent and up-to-date review of several contributions Quaternary botany is making to ecology and biogeography. These fall into four general parts:
- Ecological aspects of interglacial glacial stages such as tree glacial-stage refugia and long-term soil development
- Biotic responses to environmental change (extinction, adaptation, persistence, spreading) in the Quaternary
- Ecological concepts and topics that have developed directly as a result of Quaternary botanical studies such as potential niches, realised environmental spaces, no-analogue assemblages, the nature of vegetation, and long-term tree and forest dynamics
- The application of Quaternary botany to topics such as the extent of human impact on tropical systems, conservation in a changing world, island palaeoecology, plant–animal interactions and megafaunal extinctions, and biodiversity studies.
It concludes with speculations about future directions and present 10 suggestions to help strengthen links with modern ecology and biogeography.
What is a Grubb Review?
This paper is the ninth Grubb Review published in Plant Ecology & Diversity. Professor Emeritus Peter Grubb, doyen of British plant ecology, has had a global impact on critical thinking about plant ecology, and on how to turn ecology into a more exact and less simplistic subject.
Grubb Reviews were launched in 2016 and each aims to make substantial contributions to critical and analytical thinking. They often go beyond general syntheses and contribute to debating ecological theory, exploring links between different ecological topics, and evaluating the evidence (or lack of it) that empirical studies may or may not provide to test ecological hypotheses.
I am the first author of a Grubb Review to have been taught by Peter Grubb. He taught me when I was an undergraduate in Cambridge 1963-66. As a graduate student and junior staff member (1966-69; 1971-75) I helped run the first-year botany practical classes (three 2-hour classes a week) in conjunction with Peter. I learnt much from him about world botany and the many different approaches to ecology and to scientific research and about always questioning ecological truths.
H. John B. Birks (2019) Contributions of Quaternary botany to modern ecology and biogeography. Plant Ecology and Diversity 12: 189-385. 10.1080/17550874.2019.1646831