Mapping the forage nitrogen, phosphorus, and potassium contents of alpine grasslands by integrating Sentinel-2 and Tiangong-2 data

Table 3 All the forage nutrient estimation models based on the spectral bands of the Sentinel-2 MSI

Sentinel-2	N						P						K
	RF			SVM			RF			SVM			RF			SVM
	S2	S2-RFFS	S2- LASSO	S2	S2-RFFS	S2- LASSO	S2	S2-RFFS	S2- LASSO	S2	S2-RFFS	S2- LASSO	S2	S2-RFFS	S2- LASSO	S2	S2-RFFS	S2- LASSO
Number	10	7	4	10	7	4	10	7	2	10	7	2	10	8	2	10	8	2
R²	0.76	0.76	0.76	0.70	0.68	0.69	0.73	0.71	0.67	0.62	0.61	0.64	0.82	0.80	0.77	0.76	0.76	0.74
^{RMSE (%)}	0.29	0.28	0.29	0.32	0.33	0.33	0.03	0.03	0.04	0.04	0.04	0.04	0.37	0.39	0.41	0.43	0.42	0.44
NRMSE	0.20	0.19	0.20	0.22	0.23	0.22	0.27	0.28	0.29	0.32	0.32	0.31	0.26	0.28	0.30	0.30	0.30	0.32
RPD	1.68	1.75	1.70	1.71	1.66	1.67	1.53	1.52	1.49	1.44	1.44	1.52	1.81	1.76	1.70	1.82	1.81	1.76
AIC	− 177.16	− 190.92	− 192	− 180.94	− 180.63	− 187.81	− 579.9	− 584.47	− 591.37	− 568.51	− 574.45	− 593.92	− 124.42	− 123.48	− 129.38	− 125.56	− 129.37	− 135.36
BIC	− 151.94	− 173.26	− 181.91	− 155.72	− 162.98	− 177.73	− 554.69	− 566.82	− 586.33	− 543.29	− 556.8	− 588.88	− 99.2	− 103.31	− 124.33	− 100.35	− 109.2	− 151.94

The values of R², RMSE, NRMSE, RPD, AIC, and BIC are the averages of 50 iterations of a tenfold CV. The R² value is provided by the validation dataset. The number refers to the number of spectral bands used for modeling. S2-LASSO and S2-RFFS denote the set of suitable MSI spectral bands screened based on the LASSO and RFFS algorithms, respectively. N nitrogen, P phosphorus, K potassium, S2 Sentinel-2

ISSN: 1746-4811