干旱胁迫下雷竹叶片叶绿素的高光谱响应特征及含量估算

植物叶片的反射光谱特征与叶绿素含量密切相关。以重要的笋用竹种雷竹(Phyllostachys violascens)为研究对象,采用盆栽及控水试验方法研究了2年生雷竹在干旱胁迫条件下冠层叶片反射光谱的响应特征,分析了叶片叶绿素含量与不同波段光谱反射率一阶微分值以及光谱特征参数之间的相关关系,并以雷竹叶绿素含量敏感波段及构建的植被指数与叶绿素含量进行了拟合。结果表明,重度缺水处理后雷竹叶片叶绿素含量显著降低,在可见光区叶片光谱反射率随叶绿素含量的降低而增加,以波长493、639、693、756 nm等处的光谱反射率一阶微分值与叶绿素含量的相关性较高。雷竹叶片叶绿素含量与光谱特征参数如绿峰反射率、红谷反射率、蓝边面积、绿峰面积之间的相关性较高。与已有的植被指数相比基于雷竹叶绿素含量敏感波段修正后的植被指数与叶绿素含量相关性优于原植被指数。基于反射率一阶微分值构建的多元回归方程以及修正的绿色归一化植被指数(m GNDVI)构建的回归方程拟合效果较好,为雷竹叶绿素含量的较优估算方程。研究结果可以为雷竹叶绿素含量的快速无损测定以及季节性干旱条件下雷竹林的科学经营及灾后评估提供依据。

Hyperspectral response characteristics and chlorophyll content estimation of Phyllostachys violascens leaves under drought stress

Plant leaf spectral reflectance is closely related to leaf chlorophyll content (LCC). The present study investigated the canopy leaf reflectance spectrum characteristics of Phyllostachys violascens under drought stress with 2 a potted plants and water control methods. The correlation between LCC and first derivative of spectral reflectance together with spectral characteristics parameters were calculated and analyzed. The regression equation of vegetation index and LCC was build based on the reflectance spectrum sensitive wavelengths of LCC. The results indicated that:the LCC in P. violascens leaves was significantly reduced under severe drought stress conditions. In the visible region, the spectral reflectance of leaves increased with the decrease of LCC. The correlation with LCC and first derivative of spectral reflectance at wavelengths of 493 nm, 639 nm, 693 nm and 756 nm was higher. The correlation coefficients between LCC and spectral characteristic parameters such as green peak reflectance, red valley reflectivity, blue edge area and green peak area was higher than other parameters. The correlation between the modified vegetation index and LCC was better than that of original vegetation index. The regression equation based on spectral reflectance and first derivative of spectral reflectance at four wavelengths (493 nm, 639 nm, 693 nm, and 756 nm) together with the modified green normalized vegetation index (mGNDVI) were optimal equation for estimation LCC of P. violascens. The results can provide a basis for the rapid and nondestructive determination of LCC. Furthermore, it can provide guidance for scientific management and post-disaster evaluation of bamboo forests under seasonal drought conditions.