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Biology Articles » Zoology » Intrinsic and climatic factors in North-American animal population dynamics » Table 2

Table 2
- Intrinsic and climatic factors in North-American animal population dynamics

Spectral analysis of the two leading components of the four data sets; the periods are given in years. The first column for each PC gives the dominant periodicities, the second one gives the less pronounced peaks; for economy of presentation, the 160–170-year nonlinear trend [5] is also included in the first column for PC-1. The analysis reported in this Table was performed using the median-filter MTM [3,5] with the bandwidth parameter p = 2 and K = 3 tapers. These parameter values give a spectral resolution of 0.04 cycles/year, i.e., they allow us to discriminate between peaks at 2, 2.5, 3 and 3.5 years. The results were checked using Monte Carlo SSA [4,5] with a window width of M = 9 year. The significance level of the main periods is at least 99% against a null hypothesis of red noise; for the secondary periods, the threshold is 95%. Periods in bold are significant in both the MTM and SSA analyses; periods in italics are strongly significant in one of the two methods and marginally significant in the other, while other periods are only significant in one of the two analyses.

  PC-1
PC-2
 
  Main periods
Secondary periods
Main periods
Secondary periods

Furs
170 3
2.5
2.5
40
Furs+NAO
160 3
2.5
3.5
40 2
Furs +ENSO
160 3
2.5
4 2.5 2
30
Furs+temp
170 3
2.5
44 2.5
3.5


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