Table 2.
Mixed effects model results of summertime abundances of the most common arthropods at Zackenberg, as predicted by habitat type and the three principal components summarized in table 1. Higher values of PC1 are indicative of warmer active seasons and fewer winter freeze–thaw events; higher values of PC2 represent warmer non-active seasons, and higher values of PC3 are indicative of longer winters. Interactions between habitat type and each of the composite environmental variables were included in all models as fixed effects, whereas Plot and Year were included as random effects. Arid heath is the reference category for habitat type. Individual models were simplified by removing non-significant predictors one by one. Results shown here are from the most parsimonious models. *p < 0.05, **p < 0.001, ***p < 0.0001.
| fixed effects terms | coeff. | s.e. | d.f. | t | p-value |
|---|---|---|---|---|---|
| Acari | |||||
| intercept | 1.220 | 0.122 | 15.25 | 10.007 | <0.001*** |
| habitat type (reference category: arid heath) | |||||
| mesic heath | −0.499 | 0.110 | 4.23 | −4.543 | 0.009** |
| wet fen | 0.326 | 0.134 | 4.13 | 2.441 | 0.069 |
| PC1 | −0.231 | 0.120 | 30.95 | −1.935 | 0.062 |
| PC2 | — | — | — | — | n.s. |
| PC3 | −0.233 | 0.115 | 26.70 | −2.029 | 0.053 |
| habitat type × PC1 | |||||
| mesic heath | 0.201 | 0.095 | 66.49 | 2.110 | 0.039* |
| wet fen | 0.206 | 0.114 | 65.97 | 1.816 | 0.074 |
| habitat type × PC2 | |||||
| mesic heath | — | — | — | — | n.s. |
| wet fen | — | — | — | — | n.s. |
| habitat type × PC3 | |||||
| mesic heath | 0.116 | 0.089 | 64.86 | 1.302 | 0.198 |
| wet fen | 0.274 | 0.108 | 64.81 | 2.528 | 0.014* |
| Araneae | |||||
| intercept | 0.636 | 0.065 | 8.21 | 9.779 | <0.001*** |
| habitat type (reference category: arid heath) | |||||
| mesic heath | 0.149 | 0.078 | 4.66 | 1.896 | 0.121 |
| wet fen | 0.364 | 0.096 | 4.61 | 3.804 | 0.015* |
| PC1 | — | — | — | — | n.s. |
| PC2 | −0.085 | 0.047 | 33.24 | −1.813 | 0.079 |
| PC3 | 0.052 | 0.047 | 33.48 | 1.104 | 0.277 |
| habitat type × PC1 | |||||
| mesic heath | — | — | — | — | n.s. |
| wet fen | — | — | — | — | n.s. |
| habitat type × PC2 | |||||
| mesic heath | 0.115 | 0.046 | 64.91 | 2.514 | 0.014* |
| wet fen | −0.023 | 0.056 | 64.86 | −0.410 | 0.684 |
| habitat type × PC3 | |||||
| mesic heath | 0.019 | 0.046 | 64.97 | 0.407 | 0.685 |
| wet fen | −0.123 | 0.056 | 64.90 | −2.208 | 0.031* |
| Collembola | |||||
| intercept | 1.268 | 0.222 | 6.17 | 5.721 | 0.001** |
| habitat type (reference category: arid heath) | |||||
| mesic heath | 0.147 | 0.295 | 4.90 | 0.498 | 0.640 |
| wet fen | −0.391 | 0.361 | 4.89 | −1.084 | 0.329 |
| PC1 | −0.181 | 0.084 | 18.07 | −2.151 | 0.045* |
| PC2 | −0.220 | 0.083 | 17.44 | −2.640 | 0.017* |
| PC3 | −0.295 | 0.094 | 27.79 | −3.138 | 0.004** |
| habitat type × PC1 | |||||
| mesic heath | — | — | — | — | n.s. |
| wet fen | — | — | — | — | n.s. |
| habitat type × PC2 | |||||
| mesic heath | — | — | — | — | n.s. |
| wet fen | — | — | — | — | n.s. |
| habitat type × PC3 | |||||
| mesic heath | 0.070 | 0.078 | 64.99 | 0.891 | 0.376 |
| wet fen | 0.239 | 0.095 | 64.95 | 2.509 | 0.015* |
| Diptera | |||||
| intercept | 1.037 | 0.091 | 33.65 | 11.383 | <0.001*** |
| habitat type (reference category: arid heath) | |||||
| mesic heath | 0.070 | 0.084 | 69.62 | 0.830 | 0.410 |
| wet fen | 0.877 | 0.102 | 69.51 | 8.575 | <0.001*** |
| PC1 | — | — | — | — | n.s. |
| PC2 | — | — | — | — | n.s. |
| PC3 | — | — | — | — | n.s. |
| habitat type × PC1 | |||||
| mesic heath | — | — | — | — | n.s. |
| wet fen | — | — | — | — | n.s. |
| habitat type × PC2 | |||||
| mesic heath | — | — | — | — | n.s. |
| wet fen | — | — | — | — | n.s. |
| habitat type × PC3 | |||||
| mesic heath | — | — | — | — | n.s. |
| wet fen | — | — | — | — | n.s. |
| Hemiptera | |||||
| intercept | 0.212 | 0.039 | 8.28 | 5.372 | 0.001*** |
| habitat type (reference category: arid heath) | |||||
| mesic heath | 0.081 | 0.048 | 5.10 | 1.701 | 0.148 |
| wet fen | −0.148 | 0.058 | 4.97 | −2.555 | 0.051 |
| PC1 | 0.122 | 0.039 | 57.34 | 3.159 | 0.003** |
| PC2 | — | — | — | — | n.s. |
| PC3 | 0.063 | 0.036 | 47.07 | 1.779 | 0.082 |
| habitat type × PC1 | |||||
| mesic heath | −0.100 | 0.044 | 67.36 | −2.257 | 0.027* |
| wet fen | −0.088 | 0.053 | 66.60 | −1.674 | 0.099 |
| habitat type × PC2 | |||||
| mesic heath | — | — | — | — | n.s. |
| wet fen | — | — | — | — | n.s. |
| habitat type × PC3 | |||||
| mesic heath | −0.140 | 0.041 | 65.12 | −3.375 | 0.001** |
| wet fen | −0.093 | 0.051 | 65.01 | −1.831 | 0.072 |
| Hymenoptera | |||||
| intercept | 0.162 | 0.039 | 6.36 | 4.140 | 0.005** |
| habitat type (reference category: arid heath) | |||||
| mesic heath | 0.101 | 0.052 | 5.09 | 1.935 | 0.110 |
| wet fen | 0.027 | 0.064 | 5.04 | 0.421 | 0.691 |
| PC1 | 0.016 | 0.025 | 55.61 | 0.632 | 0.530 |
| PC2 | 0.015 | 0.023 | 44.87 | 0.664 | 0.510 |
| PC3 | — | — | — | — | n.s. |
| habitat type × PC1 | |||||
| mesic heath | 0.090 | 0.028 | 66.84 | 3.216 | 0.002** |
| wet fen | 0.003 | 0.034 | 66.32 | 0.099 | 0.921 |
| habitat type × PC2 | |||||
| mesic heath | 0.069 | 0.026 | 65.30 | 2.638 | 0.010* |
| wet fen | −0.049 | 0.032 | 65.23 | −1.542 | 0.128 |
| habitat type × PC3 | |||||
| mesic heath | — | — | — | — | n.s. |
| wet fen | — | — | — | — | n.s. |
| Lepidoptera | |||||
| intercept | 0.152 | 0.020 | 27.48 | 7.492 | <0.001*** |
| habitat type (reference category: arid heath) | |||||
| mesic heath | −0.010 | 0.016 | 68.84 | −0.644 | 0.522 |
| wet fen | −0.100 | 0.020 | 68.77 | −5.107 | <0.001*** |
| PC1 | — | — | — | — | n.s. |
| PC2 | — | — | — | — | n.s. |
| PC3 | — | — | — | — | n.s. |
| habitat type × PC1 | |||||
| mesic heath | — | — | — | — | n.s. |
| wet fen | — | — | — | — | n.s. |
| habitat type × PC2 | |||||
| mesic heath | — | — | — | — | n.s. |
| wet fen | — | — | — | — | n.s. |
| habitat type × PC3 | |||||
| mesic heath | — | — | — | — | n.s. |
| wet fen | — | — | — | — | n.s. |