Hyperspectral characteristics and leaf area index (LAI) and SPAD value inversion of winter wheat under elevated CO2 concentration

doi:10.3969/j.issn.1004-1524.2022.03.19

Acta Agriculturae Zhejiangensis ›› 2022, Vol. 34 ›› Issue (3): 582-589.DOI: 10.3969/j.issn.1004-1524.2022.03.19

• Environmental Science • Previous Articles Next Articles

Hyperspectral characteristics and leaf area index (LAI) and SPAD value inversion of winter wheat under elevated CO₂ concentration

CAI Yao(), MIAO Yuxuan, WU Hao, WANG Dan()

School of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China

Received:2021-02-19 Online:2022-03-25 Published:2022-03-30
Contact: WANG Dan

Abstract

Abstract:

In the present study, winter wheat was selected as the research object, and an open-top chamber experiment was carried out with ambient CO₂ as control (CK) and plus 200 μmol·mol^-1CO₂ on the basis of CK as treatment (T). The canopy spectral reflectance, leaf area index(LAI) and SPAD value of winter wheat at main growth stages were measured. The correlation within LAI, SPAD value, original spectral reflectance and spectral characteristic parameters were analyzed, and the optimal estimation models were established. The results showed that the elevated CO₂ concentration increased LAI and SPAD value of winter wheat at booting-heading stage and filling stage.The elevated CO₂ concentration did not change the spectral reflectance curve, but changed the reflectance. The elevated CO₂ concentration induced the red edge position red shift first and then blue shift.Red and yellow edge area ratio (x) was the most suitable spectral parameter to estimate LAI(y) of wheat, and the regression equation was y=3.96×10^-3x²-8.60×10^-2x+1.93, of which the coefficient of determination (R²) and the root mean square error (RMSE) on validation set were 0.66 and 0.42, respectively. Red edge amplitude (x) was the most suitable spectral parameter to estimate SPAD value (y) of wheat, and the regression equation was y=-5.151×10⁴x²+2.883×10³x+33.83, of which the R² and RMSE on validation set were 0.63 and 4.61, respectively.

Key words: elevated CO₂, hyperspectral, chlorophyll content, leaf area index, winter wheat

CLC Number:

TP79
S512.11

CAI Yao, MIAO Yuxuan, WU Hao, WANG Dan. Hyperspectral characteristics and leaf area index (LAI) and SPAD value inversion of winter wheat under elevated CO₂ concentration[J]. Acta Agriculturae Zhejiangensis, 2022, 34(3): 582-589.

Figures/Tables 7

References 30

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处理 Treatment	LAI				SPAD
处理 Treatment	拔节期 Jointing stage	孕穗-抽穗期 Booting-heading stage	灌浆期 Filling stage	乳熟期 Milk-ripening stage	拔节期 Jointing stage	孕穗-抽穗期 Booting-heading stage	灌浆期 Filling stage	乳熟期 Milk-ripening stage
CK	2.09±0.11 b	2.89±0.46 a	3.23±0.55 b	2.15±0.14 a	48.13±2.72 a	55.61±2.45 a	57.31±2.77 b	49.08±3.45 a
T	2.30±0.21 a	3.05±0.29 a	3.73±0.34 a	1.99±0.31 a	47.65±3.71 a	58.29±4.34 a	61.06±3.53 a	42.73±2.70 b

处理 Treatment	LAI				SPAD
处理 Treatment	拔节期 Jointing stage	孕穗-抽穗期 Booting-heading stage	灌浆期 Filling stage	乳熟期 Milk-ripening stage	拔节期 Jointing stage	孕穗-抽穗期 Booting-heading stage	灌浆期 Filling stage	乳熟期 Milk-ripening stage
CK	2.09±0.11 b	2.89±0.46 a	3.23±0.55 b	2.15±0.14 a	48.13±2.72 a	55.61±2.45 a	57.31±2.77 b	49.08±3.45 a
T	2.30±0.21 a	3.05±0.29 a	3.73±0.34 a	1.99±0.31 a	47.65±3.71 a	58.29±4.34 a	61.06±3.53 a	42.73±2.70 b

生育期 Growing stage	λr/nm		Dr/10^-2		SDr/10^-2
生育期 Growing stage	CK	T	CK	T	CK	T
拔节期Jointing stage	732	732	0.74	0.69	31.06	28.87
孕穗-抽穗期Booting-heading stage	736	736	0.97	0.95	38.45	37.21
灌浆期Filling stage	735	736	0.94	0.83	38.36	33.47
乳熟期Milk-ripening stage	718	709	0.50	0.41	25.31	20.81

生育期 Growing stage	λr/nm		Dr/10^-2		SDr/10^-2
生育期 Growing stage	CK	T	CK	T	CK	T
拔节期Jointing stage	732	732	0.74	0.69	31.06	28.87
孕穗-抽穗期Booting-heading stage	736	736	0.97	0.95	38.45	37.21
灌浆期Filling stage	735	736	0.94	0.83	38.36	33.47
乳熟期Milk-ripening stage	718	709	0.50	0.41	25.31	20.81

x	r	回归方程 Regression equation	建模集Modeling set		验证集Validation set
x	r	回归方程 Regression equation	R²	RMSE	R²	RMSE
R₇₇₇	0.63^**	y=4.964+0.458 5ln x^4.964	0.43^**	0.51	0.32^**	0.59
Dr	0.70^**	y=910.1x²+192.3x+1.16	0.52^**	0.46	0.40^**	0.56
SDr	0.65^**	y=5.748x+0.850 4	0.46^**	0.50	0.35^**	0.58
SDr/SDy	0.81^**	y=3.96×10^-3x²-8.60×10^-2x+1.93	0.78^**	0.32	0.66^**	0.42
SDr/SDb	0.68^**	y=7.90×10^-4x²+5.20×10^-2x+1.52	0.52^**	0.47	0.37^**	0.57
SDr-SDy	0.64^**	y=1.150x²+4.600x+1.042	0.45^**	0.50	0.35^**	0.58
SDr-SDb	0.62^**	y=1.610x²+4.800x+1.092	0.48^**	0.49	0.37^**	0.57
(SDr-SDb)/(SDr+SDb)	-0.60^**	y=18.90x²-51.08x+36.30	0.47^**	0.49	0.34^**	0.59

Hyperspectral characteristics and leaf area index (LAI) and SPAD value inversion of winter wheat under elevated CO₂ concentration

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x	r	回归方程 Regression equation	建模集Modeling set		验证集Validation set
x	r	回归方程 Regression equation	R²	RMSE	R²	RMSE
R₇₇₀	0.71^**	y=-191.7x²+213.0x+0.813 0	0.56^**	4.37	0.47^**	5.56
λr	0.62^**	y=2.030×10^-2x²-28.76x+1.024×10⁴	0.52^**	4.61	0.47^**	5.55
Dr	0.78^**	y=-5.151×10⁴x²+2.883×10³x+33.83	0.60^**	4.21	0.63^**	4.61
SDr	0.76^**	y=62.16x+32.72	0.56^**	4.40	0.59^**	4.86
SDr/SDy	0.70^**	y=2.07×10^-2x²-1.17×10^-1x+39.28	0.50^**	4.67	0.58^**	4.95
SDr/SDb	0.67^**	y=-9.720×10^-3x²+1.003x+38.48	0.45^**	4.93	0.42^**	5.80
SDr-SDy	0.76^**	y=57.81x+33.61	0.56^**	4.38	0.60^**	4.80
SDr-SDb	0.76^**	y=60.93x+34.34	0.57^**	4.31	0.61^**	4.77
(SDr-SDb)/(SDr+SDb)	-0.60^**	y=170.6x²-462.8x+357.9	0.43^**	5.00	0.45^**	5.63

x	r	回归方程 Regression equation	建模集Modeling set		验证集Validation set
x	r	回归方程 Regression equation	R²	RMSE	R²	RMSE
R₇₇₀	0.71^**	y=-191.7x²+213.0x+0.813 0	0.56^**	4.37	0.47^**	5.56
λr	0.62^**	y=2.030×10^-2x²-28.76x+1.024×10⁴	0.52^**	4.61	0.47^**	5.55
Dr	0.78^**	y=-5.151×10⁴x²+2.883×10³x+33.83	0.60^**	4.21	0.63^**	4.61
SDr	0.76^**	y=62.16x+32.72	0.56^**	4.40	0.59^**	4.86
SDr/SDy	0.70^**	y=2.07×10^-2x²-1.17×10^-1x+39.28	0.50^**	4.67	0.58^**	4.95
SDr/SDb	0.67^**	y=-9.720×10^-3x²+1.003x+38.48	0.45^**	4.93	0.42^**	5.80
SDr-SDy	0.76^**	y=57.81x+33.61	0.56^**	4.38	0.60^**	4.80
SDr-SDb	0.76^**	y=60.93x+34.34	0.57^**	4.31	0.61^**	4.77
(SDr-SDb)/(SDr+SDb)	-0.60^**	y=170.6x²-462.8x+357.9	0.43^**	5.00	0.45^**	5.63