Geoscience Reference
In-Depth Information
Quaternary Geography: Sensitivity and Thresholds
Figure 13.10 shows how the tree populations in the three areas of Greece shown in
fi gure 13.6b might have responded to environmental stresses such as the drying and
cooling associated with Heinrich Events. The response to such a stress is very dif-
ferent between the three regions and this is a function of local environmental condi-
tions. A key point here is that we should not expect the same response to rapid
climate change events in all parts of the landscape as some populations already lie
close to their tolerance limit. The schematic representation of temperate tree abun-
dance shown in the lower part of fi gure 13.10 shows the variable response between
each region to climatically induced stress. Tzedakis et al. (2004) use the example
of temperate tree abundance, but the variable response could equally be glacier mass
balance, karst spring discharge, river sediment yield, or the availability of a key
plant or animal resource for a group of Middle Palaeolithic foragers. Some systems
may have switched on and off while others showed fl uctuations in some measure
of abundance or yield. This fi gure could even represent the population shifts in
Neanderthal groups in their refuges in southern Europe before their fi nal demise
(see Gamble et al., 2004).
Figure 13.10
A schematic representation of (a) variations of environmental stress
encountered by tree populations and (b) the response of the local temperate tree
population at the three sites under discussion (modifi ed after Tzedakis et al., 2004).
Additional data on each of the three sites are given in table 13.2.
