摘要：Organisms can respond to rapid climatic changes in
three ways: 1) adaptation by evolution, affecting
physiology and morphology), 2) migration and population dynamics including biogeographical changes)
and 3) extinction local or global). Here, the focus is
on examples of the second type. Organisms, whether
algae, trees, or animals, find their ecological niches in a
multi- dimensional space of gradients such as temperature winter, summer, means or extremes), humidity soil or air), pH, various nutrients, light. Presence
or absence of taxa species, genera, families) can be
related to such gradients. With training sets based on
current gradients, they can also be related to environmental changes of the past e. g. summer mean
temperatures or pH). The relationships between
the occurrence of taxa and environmental variables
can also be used to examine the biotic response to
changes based on other proxies, for example, changes
in temperature inferred from oxygen- isotope ratios
in carbonates or from the content in organic matter
of lake sediments. The groups of organisms referred
to here are plants pollen), insects chironomids) and
other aquatic invertebrates. The three Late Glacial
periods with very high rates of change in temperature
estimates are the transition from the Oldest Dryas to
the Bölling from GS- 2 to GI- 1 in the Late Glacial,
ca. 14 670 cal yr BP), and the beginning and the end
of the Younger Dryas ca. 12 600 cal yr BP, 11 500 cal
yr BP respectively).
<br><br>
The « classical » hypothesis was that trees represented
in pollen diagrams) respond more slowly to climatic
change than invertebrates aquatic or terrestrial)
because of differences in life cycles. But it is shown here
that terrestrial vegetation) and aquatic invertebrate)
ecosystems may respond synchronously. Three major
biological processes are involved in the responses to
climatic change:<br>
1) Migration – can be slow if, for example, a longliving tree migrated back from a southern refugium.<br>
2) Build- up of populations – intermediate velocity,
for the process needs time depending on the life
cycles of the organisms.<br>
3) Productivity – can change rapidly, within a year
or a few years e. g. pollen productivity, tree rings).
The first two of these processes occur on the organisational level of populations, the last one on the level of
the individual. These processes develop also in various
combinations.<br>
