Phase- and density-dependent population dynamics in Norwegian lemmings: interaction between deterministic and stochastic processes
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Published on: July 4, 2007
N C Stenseth1, K S Chan, E Framstad
1Centre for Advanced Study, Norwegian Academy of Science and Letters, Oslo, Norway. n.c.stenseth@bio.uio.no
Abstract:
We analysed two 26-year long (1970-1995) time-series on annual population growth rates of Norwegian lemmings (Lemmus lemmus) from Finse, south Norway, using a threshold autoregressive (TAR) approach. We demonstrate that the population dynamics is both phase- and density-dependent. The phase-dependence accounts for the observed nonlinearity. We used the deduced stochastic model structure as a basis for evaluating the dynamic properties of this system. The dynamics is characterized either by limit cycles or chaos (the latter with a strong semi-periodic component). Stochasticity is seen to play an important role in the determination of the periodicity. The ecological implications of these statistical and mathematical results are discussed.
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