河西走廊典型荒漠植物抗旱结构及其光谱特征研究

The spectroradiometer characteristic curve of plant is a key foundation of hyperspectral remote sensing classification and evaluation,which is an effective means when make a macro-survey research of plant spatial distribution,the vegetation species composition and its growth status. Desert vegetation that growth sparse and distribute in remote space plays an absolutely important role in the desert ecosystem of the Hexi Corridor. its spectral curve is not yet complete system measurement, the typical characteristics database of plant surface reflectance spectral has been established which lack the desert plants spectral curve.Compared with the non-desert plants, Desert plants have a lot of drought-resistant leaf structural deformation in the morphology, water storage methods and content of biochemical substances,which has been selected by the the harsh natural situation. The deformation makes obvious differences with others no-desert plant spectral curve in the spectral features. Hexi Corridor stretches more than 1,000 kilometers, to the west extreme drought area less than 10mm from the arid areas of eastern rainfall 220mm, where widely distributed in various types of desert plants cope with drought strategies. This project plans to measure all the reflectance spectra curve of the canopy and leaf types, plant morphology, drought organizational structure, drought-tolerant biochemical substance content　of variety plant with different response to drought policy type in the Hexi Corridor,then analyze the differences ofthem and Find the Special characteristic spectrum of each type of classic desert plant that different from non-desert plants and that different with each other. it will Analysis the relationship between the spectral characteristics and the special deformation structure, it also establishment a reflectance spectrum curve database of typical desert plants in Hexi Corridor, then it will Provide a basis judgment key of desert plant species for the remote monitoring identify of desert vegetation,so it will fill the blank that the typical desert plants spectral curves are missed in the database of reflectance spectra characteristic curve.

地物反射光谱特征曲线是高光谱遥感地物识别与评估的基础，但已建立的典型地物光谱数据库缺乏有关荒漠植物的光谱特征曲线。荒漠植物为适应严酷自然条件在叶片结构、生化物质含量等方面具有特殊的耐旱结构变形，这些变形导致其反射光谱曲线在特定波段具有相应的独特特征参量变化。河西走廊从东部降水220mm的干旱气候到西部不足10mm的极端干旱区绵延千余公里，在不同地段广泛分布有各种不同应对干旱策略类型的荒漠植物。项目系统选择测定河西走廊逃避型、耗水型和节水型等不同应对干旱策略类型典型荒漠植物种冠层光谱曲线、叶片类型、植株形态、耐旱组织结构、耐旱生化物质含量，分析耐旱物质、耐旱结构及其反射光谱曲线的差异性，筛选能用于精细分类各策略类型典型荒漠植物差异性光谱特征参量，建立典型荒漠植物光谱特征数据库，为荒漠植被遥感监测提供典型荒漠植物种分类识别的判断基础，填补目前典型地物光谱数据库中缺乏荒漠植物光谱特征曲线的遗憾。

地物反射光谱特征曲线是高光谱遥感地物识别与评估的基础，但已建立的典型地物光谱数据库缺乏有关荒漠植物的光谱特征曲线。荒漠植物为适应严酷自然条件在叶片结构、生化物质含量等方面具有特殊的耐旱结构变形，这些变形导致其反射光谱曲线在特定波段具有相应的独特特征参量变化。项目测定河西走廊典型荒漠植物冠层光谱曲线、耐旱生化物质含量，筛选能用于精细分类各策略类型典型荒漠植物差异性光谱特征参量，建立典型荒漠植物光谱特征数据库，取得了以下主要结果：1）荒漠植物反射光谱“绿峰”特征和“红边效应”明显，多浆植物红边区域、卷叶植物绿峰区域特征尤为明显，“红边”和“绿峰”可用为荒漠植被识别的主要辅助参数；在植被叶片含水量控制的叶片反射率波段范围1250-2300nm，荒漠植被光谱特征区分性相对较好，水分含量可提高荒漠植被的识别精度。2）水波段指数、归一化水指数、归一化红外指数和水分胁迫指数4个冠层水分含量指数与植物含水率之间存在显著的相关关系，可以用荒漠植物观测水分含量指数特征来反演它含水率的大小。3）不同退化阶段植物冠层光谱反射率在1390-2500nm随着植物衰退程度的增加而增加，在植被衰退和严重衰退的区域，沙地的光谱曲线和裸地的基本重合。4）植物光谱的季相变化与植物本身的物候规律相吻合，与外界环境的变化密切相关。5）阴影端元对提高植被盖度估算的准确性非常重要，尤其是对非光合植被盖度估算的影响尤为重要，白刺灌丛样地采用线性混合模型，梭梭样地非线性混合模型的效果更明显。S2影像较高的空间、光谱分辨率和较多的红边波段，使其在光合/非光合植被盖度的估算精度方面优于L8和 GF1影像。6）荒漠植物脯氨酸含量差异很大，含量较高的植物有：白刺、泡泡刺、红砂、多枝柽柳、树锦鸡儿、霸王、中麻黄、木贼麻黄、骆驼蓬、沙枣等，植物叶片叶绿素的含量与叶片的形状有密切的关系，卷叶类植物叶绿素含量最高，其次为薄叶。