水分敏感的反射光谱指数比较研究——以锐齿槲栎为例

doi:10.17521/cjpe.2016.0095

摘要/Abstract

摘要：

利用叶片反射光谱实时、无损地探测植物水分状况是森林干旱评估的新方法, 但是不同光谱指数的水分敏感性存在很大差异, 因此, 确定适用于树木叶片的水分指标与其敏感的光谱指标均非常重要。该研究选取锐齿槲栎(Quercus aliena var. acuteserrata)不同发育阶段和冠层位置上的叶片作为研究对象, 在失水条件下, 测定叶片的水分指标及其同步的反射光谱响应曲线, 探究叶片的光谱反射率变化与水分状况改变的关系, 比较并评估不同叶片发育阶段和冠层位置叶片的水分指标与不同反射光谱指数之间相关关系的优劣。结果表明: (1)在4个不同水分指标中, 与比叶含水量(SWC)和叶片水分鲜质量比(LMP)相比, 相对含水量(RWC)和等效水分厚度(EWT)在不同发育阶段和冠层位置之间的变异性更小, 能稳定地表征树木整体的水分状况; 且RWC和EWT具有更高的光谱敏感性, 适用于遥感探测。(2)光谱反射率差值分析法和光谱反射率敏感性分析法表明: 叶片的光谱敏感性受发育阶段的影响较大; 在短波红外区域, 成熟叶片在失水胁迫初始阶段的光谱变化较小, 而新展叶在整个失水阶段均表现出明显的光谱差异。(3)通过对15个不同光谱指数与水分指标的相关分析, 发现水分指数(WI)-RWC和双差值指数(DD_n_(1530,525))-EWT均具有较高的相关性, 其中, WI-RWC的拟合关系受叶片发育阶段和冠层位置的影响较大; 而DD_n_(1530,525)-EWT的拟合关系更为稳定。

关键词: 反射光谱指数, 锐齿槲栎, 叶片失水, 发育阶段, 冠层位置

Abstract:

Aims Using leaf spectral reflectance to detect plant status in real time and non-destructively is a new method of forest drought assessment, but each spectral index possesses considerable moisture sensitivity. Therefore, determining moisture index applicable to tree leaf and its sensitive spectral index are both very important. Methods This study selected Quercus aliena var. acuteserrata leaves in different growth stages and canopy positions as the research object, and measured leaf moisture index and its synchronous reflectance spectral response curve during the dehydration process, explored the relationship between changes of leaf spectral reflectance and water status, compared and evaluated the advantages and disadvantages of correlation between the moisture indices of leaves in different growth stages and space positions and different spectral reflectance indices. Important findings Results indicated: (1) The variability of relative water content (RWC) and equivalent water thickness (EWT) in different growth stages and canopy positions was smaller than specific leaf water content (SWC) and leaf moisture percentage on fresh quality (LMP) as measured by the four different moisture indices. RWC and EWT could steadily characterize the holistic water status of trees, and they had greater spectral sensitivity. Therefore, they were suitable for application in remote sensing detection. (2) Spectral reflectance difference analysis and spectral reflectance sensitivity analysis showed that the leaf spectral sensitivity is strongly influenced by growth stage. In short wave infrared region, spectral reflectance of mature leaves changed slightly in the initial stage of dehydration stress, but new expended leaves showed obvious spectral differences during the dehydration process. (3) Through the correlation analysis between 15 different spectral indices and moisture indices, we found that water index (WI)-RWC and double difference index (DD_n_(1530,525))-EWT has higher correlation. The fitted relations of WI-RWC are greatly influenced by leaf growth stage and canopy position, while those of DD_n_(1530,525)- EWT are more stable.

Key words: spectral reflectance indices, Quercus aliena var. acuteserrata, leaf dehydration, growth stage, canopy position

刘畅, 孙鹏森, 刘世荣. 水分敏感的反射光谱指数比较研究——以锐齿槲栎为例. 植物生态学报, 2017, 41(8): 850-861. DOI: 10.17521/cjpe.2016.0095

Chang LIU, Peng-Sen SUN, Shi-Rong LIU. A comparison of spectral reflectance indices in response to water: A case study of Quercus aliena var. acuteserrata. Chinese Journal of Plant Ecology, 2017, 41(8): 850-861. DOI: 10.17521/cjpe.2016.0095

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https://www.plant-ecology.com/CN/Y2017/V41/I8/850

图/表 7

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反射光谱指数 Spectral reflectance index	缩写 Acronym	定义 Definition	参考文献 Reference
水分指数 Water index	WI	R₉₀₀/R₉₇₀	Pe?uelas et al., 1993
水分指数/归一化植被指数 Water index/normalized difference vegetation index	WI/NDVI	(R₉₀₀/R₉₇₀)/[(R₉₀₀-R₆₈₀)/(R₉₀₀+R₆₈₀)]	Pe?uelas & Inoue, 1999
水分胁迫指数 Moisture stress index	MSI	R₈₂₀/R₁₆₀₀	Hunt & Rock, 1989
简单比值指数 Simple ratio index_(760,1650)	SR_(760,1650)	R₇₆₀/R₁₆₅₀	Tian et al., 2006
简单比值指数 Simple ratio index_(1300,1450)	SR_(1300,1450)	R₁₃₀₀/R₁₄₅₀	Seelig et al., 2008
简单比值水分指数 Simple ratio water index	SRWI	R₈₆₀/R₁₂₄₀	Zarco-Tejada et al., 2003
归一化红外指数 Normalized difference infrared index	NDII	(R₈₅₀-R₁₆₅₀)/(R₈₅₀+R₁₆₅₀)	Hardisky et al., 1983
归一化水分指数 Normalized difference water index	NDWI	(R₈₆₀-R₁₂₄₀)/(R₈₆₀+R₁₂₄₀)	Gao, 1996
水分含量反射指数 Water content reflactance index	WCRI	R₁₄₅₅/(R₁₂₇₂-R₁₄₅₅)	Sun et al., 2008
三波段复合指数 Three-band composite index	SR_(610,560)/ND_(810,610)	(R₆₁₀/R₅₆₀)/[(R₈₁₀-R₆₁₀)/(R₈₁₀+R₆₁₀)]	Tian et al., 2004
四波段干旱指数 Four bands drought index	SR_(1640,2130)/ND_(855,555)	(R₁₆₄₀/R₂₁₃₀)/[(R₈₅₅-R₅₅₅)/(R₈₅₅+R₅₅₅)]	Zhang & Guo, 2006
归一化多波段干旱指数 Normalized multi-band drought index	NMDI	[(R₈₆₀-(R₁₆₄₀-R₂₁₃₀)]/[R₈₆₀+(R₁₆₄₀+R₂₁₃₀)]	Wang & Qu , 2007
三波段比值指数 Three-band ratio index₉₇₅	Ratio₉₇₅	2R_960-990/(R_920-940+R_1090-1110)	Pu et al., 2003
三波段比值指数 Three-band ratio index₁₂₀₀	Ratio₁₂₀₀	2R_1180-1220/(R_1090-1110+R_1265-1285)	Pu et al., 2003
双差值指数 Double difference index	DD_n_{(1530, 525)}	2R₁₅₃₀-R₁₀₀₅-R₂₀₅₅	Wang & Li, 2012

反射光谱指数 Spectral reflectance index	缩写 Acronym	定义 Definition	参考文献 Reference
水分指数 Water index	WI	R₉₀₀/R₉₇₀	Pe?uelas et al., 1993
水分指数/归一化植被指数 Water index/normalized difference vegetation index	WI/NDVI	(R₉₀₀/R₉₇₀)/[(R₉₀₀-R₆₈₀)/(R₉₀₀+R₆₈₀)]	Pe?uelas & Inoue, 1999
水分胁迫指数 Moisture stress index	MSI	R₈₂₀/R₁₆₀₀	Hunt & Rock, 1989
简单比值指数 Simple ratio index_(760,1650)	SR_(760,1650)	R₇₆₀/R₁₆₅₀	Tian et al., 2006
简单比值指数 Simple ratio index_(1300,1450)	SR_(1300,1450)	R₁₃₀₀/R₁₄₅₀	Seelig et al., 2008
简单比值水分指数 Simple ratio water index	SRWI	R₈₆₀/R₁₂₄₀	Zarco-Tejada et al., 2003
归一化红外指数 Normalized difference infrared index	NDII	(R₈₅₀-R₁₆₅₀)/(R₈₅₀+R₁₆₅₀)	Hardisky et al., 1983
归一化水分指数 Normalized difference water index	NDWI	(R₈₆₀-R₁₂₄₀)/(R₈₆₀+R₁₂₄₀)	Gao, 1996
水分含量反射指数 Water content reflactance index	WCRI	R₁₄₅₅/(R₁₂₇₂-R₁₄₅₅)	Sun et al., 2008
三波段复合指数 Three-band composite index	SR_(610,560)/ND_(810,610)	(R₆₁₀/R₅₆₀)/[(R₈₁₀-R₆₁₀)/(R₈₁₀+R₆₁₀)]	Tian et al., 2004
四波段干旱指数 Four bands drought index	SR_(1640,2130)/ND_(855,555)	(R₁₆₄₀/R₂₁₃₀)/[(R₈₅₅-R₅₅₅)/(R₈₅₅+R₅₅₅)]	Zhang & Guo, 2006
归一化多波段干旱指数 Normalized multi-band drought index	NMDI	[(R₈₆₀-(R₁₆₄₀-R₂₁₃₀)]/[R₈₆₀+(R₁₆₄₀+R₂₁₃₀)]	Wang & Qu , 2007
三波段比值指数 Three-band ratio index₉₇₅	Ratio₉₇₅	2R_960-990/(R_920-940+R_1090-1110)	Pu et al., 2003
三波段比值指数 Three-band ratio index₁₂₀₀	Ratio₁₂₀₀	2R_1180-1220/(R_1090-1110+R_1265-1285)	Pu et al., 2003
双差值指数 Double difference index	DD_n_{(1530, 525)}	2R₁₅₃₀-R₁₀₀₅-R₂₀₅₅	Wang & Li, 2012

样本 Sample	水分相关变量 Variables related to water	样本数 Number of sample	最大值 Maximum value	最小值 Minimum value	平均值 Mean value	标准偏差 Standard deviation	变异系数 Coefficient of variation (%)
顶部新展叶 Top new expended leaf	SWC	12	2.24	2.06	2.15	0.07	3.11
	LMP	12	0.69	0.67	0.68	0.01	0.99
	RWC	12	0.94	0.90	0.92	0.01	1.12
	EWT	12	93.40	87.40	90.60	1.81	2.00
下部新展叶 Bottom new expended leaf	SWC	12	2.49	2.31	2.39	0.07	3.11
	LMP	12	0.73	0.71	0.72	0.01	0.99
	RWC	12	0.94	0.90	0.92	0.01	1.22
	EWT	12	97.80	91.60	94.90	1.90	2.00
顶部成熟叶 Top mature leaf	SWC	12	1.36	1.20	1.28	0.05	4.21
	LMP	12	0.58	0.55	0.56	0.01	1.85
	RWC	12	0.96	0.93	0.94	0.01	0.87
	EWT	12	88.00	82.20	85.00	2.02	2.38
下部成熟叶 Bottom mature leaf	SWC	12	1.76	1.52	1.65	0.07	4.46
	LMP	12	0.65	0.62	0.63	0.01	1.73
	RWC	12	0.96	0.93	0.95	0.01	0.91
	EWT	12	98.30	93.10	95.50	1.92	2.01

样本 Sample	水分相关变量 Variables related to water	样本数 Number of sample	最大值 Maximum value	最小值 Minimum value	平均值 Mean value	标准偏差 Standard deviation	变异系数 Coefficient of variation (%)
顶部新展叶 Top new expended leaf	SWC	12	2.24	2.06	2.15	0.07	3.11
	LMP	12	0.69	0.67	0.68	0.01	0.99
	RWC	12	0.94	0.90	0.92	0.01	1.12
	EWT	12	93.40	87.40	90.60	1.81	2.00
下部新展叶 Bottom new expended leaf	SWC	12	2.49	2.31	2.39	0.07	3.11
	LMP	12	0.73	0.71	0.72	0.01	0.99
	RWC	12	0.94	0.90	0.92	0.01	1.22
	EWT	12	97.80	91.60	94.90	1.90	2.00
顶部成熟叶 Top mature leaf	SWC	12	1.36	1.20	1.28	0.05	4.21
	LMP	12	0.58	0.55	0.56	0.01	1.85
	RWC	12	0.96	0.93	0.94	0.01	0.87
	EWT	12	88.00	82.20	85.00	2.02	2.38
下部成熟叶 Bottom mature leaf	SWC	12	1.76	1.52	1.65	0.07	4.46
	LMP	12	0.65	0.62	0.63	0.01	1.73
	RWC	12	0.96	0.93	0.95	0.01	0.91
	EWT	12	98.30	93.10	95.50	1.92	2.01

反射光谱指数 Reflectance spectral index	下部新展叶 Bottom new expended leaf				顶部新展叶 Top new expended leaf				下部成熟叶 Bottom mature leaf				顶部成熟叶 Top mature leaf
反射光谱指数 Reflectance spectral index	SWC	LMP	RWC	EWT	SWC	LMP	RWC	EWT	SWC	LMP	RWC	EWT	SWC	LMP	RWC	EWT
水分指数 Water index	0.751^**	0.751^**	0.836^**	0.801^**	0.831^**	0.830^**	0.894^**	0.867^**	0.678^**	0.685^**	0.876^**	0.806^**	0.708^**	0.713^**	0.818^**	0.776^**
水分指数/归一化植被指数 Water index/ normalized difference vegetation index	0.400^**	0.401^**	0.439^**	0.432^**	0.413^**	0.415^**	0.457^**	0.465^**	0.372^**	0.376^**	0.626^**	0.634^*	0.553^**	0.556^**	0.594^**	0.602^**
水分胁迫指数 Moisture stress index	0.411^**	0.412^**	0.493^**	0.336^**	0.401^**	0.403^**	0.483^**	0.330^**	0.251^*	0.253^*	0.633^**	0.471^**	0.338^**	0.340^**	0.603^**	0.475^**
简单比值指数 Simple ratio index_(760,1650)	0.491^**	0.494^**	0.565^**	0.463^**	0.462^**	0.465^**	0.505^**	0.393^**	0.283^*	0.285^*	0.682^**	0.550^**	0.404^**	0.406^**	0.655^**	0.536^**
简单比值指数 Simple ratio index_(1300,1450)	0.366^**	0.364^**	0.601^**	0.726^**	0.385^**	0.386^**	0.612^**	0.732^**	0.421^**	0.426^**	0.716^**	0.811^**	0.488^**	0.495^**	0.708^**	0.808^**
简单比值水分指数 Simple ratio water index	0.722^**	0.722^**	0.798^**	0.736^**	0.771^**	0.773^**	0.829^**	0.786^**	0.619^**	0.617^**	0.801^**	0.695^**	0.663^**	0.665^**	0.756^**	0.732^**
归一化红外指数 Normalized difference infrared index	-0.363^**	-0.363^**	-0.477^**	-0.373^**	-0.377^**	-0.37^5**	-0.472^**	-0.395^**	-0.217^*	-0.219^*	-0.631^**	-0.465^**	-0.317^**	-0.319^**	-0.577^**	-0.452^**
归一化水分指数 Normalized difference water index	0.715^**	0.717^**	0.787^**	0.726^**	0.763^**	0.764^**	0.824^**	0.777^**	0.621^**	0.623^**	0.808^**	0.697^**	0.664^**	0.667^**	0.758^**	0.733^**
水分含量反射指数 Water content reflectance index	-0.312^**	-0.315^**	-0.510^**	-0.485^**	-0.306^**	-0.308^**	-0.503^**	-0.465^**	-0.356^**	-0.359^**	-0.600^**	-0.468^**	-0.331^**	-0.336^**	-0.584^**	-0.461^**
三波段复合指数 Three-band composite index	-0.426^**	-0428^**	-0.469^**	-0.485^**	-0.422^**	-0423^**	-0.466^**	-0.473^**	-0.486^**	-0.505^**	-0.529^**	-0.535^**	-0.568^**	-0.577^**	-0.578^**	-0.592^**
四波段干旱指数 Four bands drought index	0.463^**	0.466^**	0.496^**	0.382^**	0.456^**	0.459^**	0.485^**	0.367^**	0.163	0.164	0.414^**	0.193	0.023	0.024	0.364^**	0.176
归一化多波段干旱指数 Normalized multi-band drought index	0.571^**	0.574^**	0.793^**	0.796^**	0.553^**	0.550^**	0.807^**	0.811^**	0.531^**	0.533^**	0.788^**	0.797^**	0.536^**	0.536^**	0.781^**	0.783^**
三波段比值指数 Three-band ratio index₉₇₅	-0.127	-0.129	-0.398^**	-0.309^**	-0.143	-0.145	-0.421^**	-0.316^**	-0.182^*	-0.185^*	-0.600^**	-0.416^**	-0.302^**	-0.305^**	-0.585^**	-0.431^**
三波段比值指数 Three-band ratio index₁₂₀₀	-0.093	-0.096	-0.355^**	-0.202^*	-0.085	-0.088	-0.322^**	-0.182	-0.103	-0.106	-0.565^**	-0.382^**	-0.233^*	-0.236^*	-0.537^**	-0.379^**
双差值指数 Double difference index	0.636^**	0.634^**	0.734^**	0.835^**	0.650^**	0.651^**	0.728^**	0.857^**	0.621^**	0.625^**	0.727^**	0.852^**	0.608^**	0.609^**	0.736^**	0.821^**