Table 3. Climate change causal associations. Regression coefficients and test statistics for linear mixed models examining changes in three community attributes and their association with changes in annual temperature after controlling for survey effort for 404 North American CBC circles from 1975 to 2001 containing a total of 227 species. The mixed models are based on a longitudinal study design with year representing the temporal component. The models include longitudinal effects for temperature (*T*) and survey effort (*E*) and cross-sectional effects for temperature (*T*_{1975}) and survey effort (*E*_{1975}). Coefficients with *p* ≤ 0.05 are shown in bold.