repetitive, cyclic dynamics, whereas populations from more northerly latitudes
exhibit repetitive cycles or perhaps even chaotic dynamics over time (Fig. 12.14).
Many ecological variables change as one progresses from the Arctic Circle to
more southerly latitudes, including temperature maxima and minima, precipitation,
vegetation cover and composition, primary productivity, mammalian and avian
community diversity, and human population density. Most important amongst these
variables, however, is the transition from a suite of generalist predators (red foxes,CONSUMER–RESOURCE DYNAMICS 213
2.5
2.0
1.5
1.0
0.5(^005101520)
log
Nt
A. Kilpisjarvi
B. Sotkamo
C. Ruotsala
D. Zvenigorod
E. Wytham Wood
Time (years)
2.5
2.0
1.5
1.0
0.5
0
0 5 10 15 20
2.5
2.0
1.5
1.0
0.5
0
0 5 10 15 20
2.5
2.0
1.5
1.0
0.5
0
0 5 10 15 20
2.5
2.0
1.5
1.0
0.5
0
0 5 10 15 20
Fig. 12.14The
latitudinal gradient in
vole dynamics across
northern Europe, with
most northerly sites at
the top of the figure.
(After Turchin and
Hanski 1997.)