Table 3.
Effects of vole density in adjacent habitats
| Source | Model parameters (SE) | R2, % | |||
|---|---|---|---|---|---|
| Site A | −0.63Xv(t − 1) | −0.69Xcr(t − 2) | −0.13Ya(t − 1) | 0.00Ya(t − 2) | 53.1 |
| (0.11) | (0.13) | (0.12) | (0.13) | ||
| Site B | −0.64Xv(t − 1) | −0.59Xcr(t − 2) | −0.14Yb(t − 1) | −0.11Yb(t − 2) | 54.0 |
| (0.14) | (0.15) | (0.14) | (0.16) | ||
| Site C | −0.50Xv(t − 1) | −0.61Xcr(t − 2) | −0.27Yc(t − 1) | 0.03Yc(t − 2) | 55.2 |
| (0.17) | (0.15) | (0.14) | (0.13) | ||
| Total L. lemmus | −0.60Xv(t − 1) | −0.66Xcr(t − 2) | −0.15Yll(t − 1) | 0.04Yll(t − 2) | 56.4 |
| (0.11) | (0.11) | (0.07) | (0.07) | ||
| Total M. oeconomus | −0.62Xv(t − 1) | −0.66Xcr(t − 2) | −0.05Ymo(t − 1) | 0.00Ymo(t − 2) | 52.8 |
| (0.14) | (0.15) | (0.06) | (0.07) | ||
| Total M. agrestis | −0.56Xv(t − 1) | −0.72Xcr(t − 2) | −0.26Yma(t − 1) | 0.00Yma(t − 2) | 57.8 |
| (0.11) | (0.11) | (0.10) | (0.10) | ||
| Total C. rufocanus | −0.62Xv(t − 1) | −0.64Xcr(t − 2) | −0.11Ycr(t − 1) | −0.01Ycr(t − 2) | 53.1 |
| (0.13) | (0.16) | (0.10) | (0.11) | ||
Direct and delayed effects, Y(t − 1) and Y(t − 2), of total vole density in three adjacent study areas are added as explanatory variables in the optimal model corresponding to hypothesis 3b. Site A is a highly productive peatland area totally dominated by the root vole; site B is a less productive peatland area; and site C is an alpine area. Additionally, the separate effects of lemmings, root voles, filed voles, and gray-sided voles averaged over the three sites are shown (startnig in 1959). Addition of a 2-year delayed effect can never improve the AIC, but a direct effect of total lemmings (ΔAIC = 2.28; P = 0.04), total field voles (ΔAIC = 4.22; P = 0.02), or site C (ΔAIC = 1.28; P = 0.07) may be included. All available data back to 1949 are used in this analysis. Restricting the range of years to only those where all variables are represented did not alter the results very much. An exception is site B, where a second-year delayed effect of −0.40 will be included by AIC if only data after 1967 are used. SE values are given in parentheses.