Table 3.

Standardized Root-Mean-Square Error (SRMSE) of Boosted Regression Tree Predictions Against Training and Testing Data for Diffusive, Ebullitive And Total CH₄ and CO₂ Emission Rates

			Training			Testing
Response variable	Covariates	Optimal trees	isMSE	isSRMSE	R2	osMSE	osSRMSE
Diffusive CH4	national	12,803	0.38	0.40	0.87	0.41	0.42
	national + local	19,976	0.17	0.26	0.90	0.54	0.46
Ebullitive CH4	national	19,987	1.72	0.24	0.98	2.28	0.28
	national + local	16,760	0.52	0.13	0.99	3.42	0.33
Total CH4	national	19,984	0.91	0.15	0.99	0.46	0.11
	national + local	17,190	0.56	0.11	0.99	5.55	0.34
Total CO2	national	14,813	1,565	−4.29	0.73	734	−2.94
	national + local	8,935	730	−1.65	0.91	274	−1.01

Note. Coefficient of determination (R²) of model predictions is reported for testing data. The “national” covariates are predictor variables available from the National Hydrography Dataset (NHDPlusV2) and related data products. The “national + local' covariates include NHD variables and additional measurements made on-site during the field survey (i.e., nutrient chemistry).