TABLE 1.
Summary of a generalized linear model analysis comparing the effect sizes of forest structure, composition, and physiography on (a) resistance (dNPPmax) and (b) resilience (αNPP) of Engelmann spruce forest to a regional spruce beetle outbreak (n = 103 sample locations).
| Metric and parameter | Estimate (β) | SE | t | p |
|---|---|---|---|---|
| (a) dNPPmax | ||||
| (Intercept) | 1.479 | 0.451 | 3.277 | 0.001 |
| Tree density (stems/ha−1) | −0.025 | 0.118 | −0.216 | 0.829 |
| QMD (cm) | −0.158 | 0.130 | −1.213 | 0.228 |
| Transformed aspect | −0.323 | 0.263 | −1.225 | 0.224 |
| Slope (%) | −0.087 | 0.127 | −0.688 | 0.493 |
| Elevation (m) | −0.309 | 0.107 | −2.892 | 0.005 |
| HLI (MJ/cm2/year) | −0.110 | 0.139 | −0.787 | 0.433 |
| Spruce basal area (%) | −0.016 | 0.005 | −3.110 | 0.002 |
| Pre‐disturbance NPP mean | −0.258 | 0.088 | −2.945 | 0.004 |
| Pre‐disturbance NPP variance | 0.088 | 0.085 | 1.038 | 0.302 |
| (b) αNPP | ||||
| (Intercept) | −0.234 | 0.113 | −2.080 | 0.040 |
| Tree density (stems/ha−1) | 0.076 | 0.094 | 0.806 | 0.422 |
| QMD (cm) | 0.050 | 0.129 | 0.386 | 0.701 |
| Transformed aspect | 0.595 | 0.227 | 2.622 | 0.010 |
| Slope (%) | −0.015 | 0.108 | −0.143 | 0.887 |
| Elevation (m) | 0.162 | 0.096 | 1.683 | 0.096 |
| HLI (MJ/cm2/year) | −0.018 | 0.116 | −0.158 | 0.875 |
| Spruce basal area (%) | 0.110 | 0.137 | 0.804 | 0.424 |
| Pre‐disturbance NPP mean | 0.035 | 0.076 | 0.457 | 0.649 |
| Pre‐disturbance NPP variance | 0.072 | 0.076 | 0.941 | 0.349 |
Note: Significant (p < 0.05) and marginally significant (p < 0.10) effects are denoted in boldface text.
Abbreviations: HLI, heat‐load index; NPP, net primary productivity; QMD, quadratic mean diameter.