TABLE 2.

Random‐forest model performance predicting abundance or richness of wild bees. Response variables were z‐score normalized prior to analysis. The R‐squared, root mean squared error (RMSE), and mean absolute error (MAE) were calculated using 10‐fold cross validation performed three times and are presented as mean ± standard deviation. Parameters mtry and ntree are the optimal values (for number of variables and number of trees, respectively) for each random‐forest model as determined by grid‐search parameter tuning

Wild‐bee taxa	Season	Response variable	RMSE	R 2	MAE	mtry	ntrees
All species	Spring	Abundance day−1 trap−1	0.89 ± 0.33	0.17 ± 0.10	0.59 ± 0.13	15	5000
	Summer/fall		0.90 ± 0.32	0.13 ± 0.09	0.59 ± 0.09	25	1000
	Spring	Richness	0.88 ± 0.16	0.25 ± 0.17	0.67 ± 0.09	35	5000
	Summer/fall		0.86 ± 0.08	0.27 ± 0.08	0.66 ± 0.05	35	2000
Andrena	Spring	Abundance day−1 trap−1	0.76 ± 0.56	0.28 ± 0.20	0.37 ± 0.14	35	2000
Nomada			0.93 ± 0.28	0.10 ± 0.10	0.59 ± 0.12	15	1000
Osmia			0.89 ± 0.28	0.21 ± 0.15	0.54 ± 0.11	15	5000
Cavity/stem nesters	Summer/fall		0.85 ± 0.36	0.23 ± 0.15	0.45 ± 0.09	55	2000
Ground nesters			0.87 ± 0.40	0.17 ± 0.11	0.53 ± 0.10	50	3000
Eusocial species			0.89 ± 0.15	0.22 ± 0.10	0.57 ± 0.06	40	3000
Solitary species			0.89 ± 0.27	0.17 ± 0.08	0.51 ± 0.09	35	5000
Native species			0.90 ± 0.33	0.13 ± 0.08	0.57 ± 0.08	30	5000
Non‐native species			0.83 ± 0.40	0.23 ± 0.17	0.42 ± 0.09	55	3000