Characteristics of Spring Phenological Changes in China over the Past 50 Years

Table 2

Internal and external validity of optimal model for 92 time series of spring phenophases. Each column shows the mean ± standard deviation.

Species	Phase	𝑁	DOY	Internal validity		External validity
				𝑅^2	RMSE	𝑅^2	RMSE
Fraxinus chinensis	FFD	2	101.9 ± 12.2	0.41 ± 0.18	3.3 ± 0.3	0.31 ± 0.18	4.6 ± 1.6
	FLD	2	100.3 ± 13.9	0.78 ± 0.29	2.4 ± 1.5	0.75 ± 0.28	3.3 ± 1.0
Ailanthus altissima	FFD	5	140.1 ± 9.9	0.69 ± 0.18	2.4 ± 1.2	0.42 ± 0.21	3.6 ± 0.5
	FLD	7	105.9 ± 10.0	0.69 ± 0.15	3.3 ± 1.0	0.77 ± 0.12	3.4 ± 1.5
Melia azedarach	FFD	16	111.2 ± 19.2	0.67 ± 0.28	3.6 ± 1.8	0.66 ± 0.22	4.1 ± 1.6
	FLD	9	89.3 ± 19.7	0.67 ± 0.28	3.9 ± 1.4	0.55 ± 0.28	4.7 ± 1.4
Paulownia tomentosa	FFD	9	89.3 ± 16.7	0.85 ± 0.17	2.3 ± 0.9	0.69 ± 0.18	3.4 ± 1.3
	FLD	12	94.8 ± 15.2	0.74 ± 0.17	4.4 ± 2.3	0.59 ± 0.21	4.6 ± 1.1
Ulmus pumila	FFD	13	82.0 ± 23.8	0.63 ± 0.34	4.2 ± 2.1	0.60 ± 0.17	5.2 ± 1.4
	FLD	17	103.4 ± 19.1	0.59 ± 0.21	4.1 ± 1.1	0.63 ± 0.23	4.1 ± 1.2
Overall		92	N/A	0.67 ± 0.24	3.7 ± 1.7	0.62 ± 0.22	4.2 ± 1.4