Study on Nutrient Content of Bothriochloa Ischaemum Community in the Loess Hilly-Gully Region Based on Spectral Characteristics
WANG Shao-yan1, CHEN Zhi-fei2, LUO Yang1, JIAN Chun-xia1, ZHOU Jun-jie3, JIN Yuan1, XU Pei-dan3, LEI Si-yue3, XU Bing-cheng1, 4*
1. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling 712100, China
2. College of Life Sciences, Guizhou University, Guiyang 550025, China
3. College of Grassland Agriculture, Northwest A&F University, Yangling 712100, China
4. Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling 712100, China
摘要： 探讨草地群落光谱特征与养分含量的关系，可为采用高光谱技术诊断草地群落营养状况，对推进快速无损检测技术应用于草地施肥管理具有重要意义。以黄土丘陵区典型草地群落，白羊草（Bothriochloa ischaemum）群落为研究对象，设置4个氮添加（0、25、50和100 kg N·ha-1·yr-1）和4个磷添加(0、20、40和80 kg P2O5·ha-1·yr-1)处理。基于群落冠层光谱和群落氮磷养分含量测定，结合红边区域内一阶导数处理，在植被指数、特征波段和红边参数组成的18个光谱特征参数中，采用逐步回归方法（SWR）筛选出对白羊草群落氮磷含量及氮磷比敏感的光谱特征参数，并建立反演模型对草地群落地上部分全氮含量和地上部分全磷含量及其比值进行估测。结果表明：白羊草群落氮磷含量随施氮量增加而增加，氮磷比随施磷量增加而减少；氮磷添加下光谱反射率在可见光波段与施肥量成反比，近红外波段与施肥量成正比，红边区域内一阶导数的“双峰现象”受氮磷添加影响显著；一些对草地群落氮磷含量较敏感的光谱特征对氮磷含量及氮磷比估测起重要作用，其中三波段光谱指数(TBSI), R910和红边幅值(AMP)对氮含量的估测模型有极大贡献（R2=0.87, F=18.8***），而磷含量估测中差值植被指数(DVI), 修正红边简比率指数(mSR705), R430, R660和AMP对模型贡献明显（R2=0.91, F=20.51***），Slope725对氮磷比的估测模型贡献最大（R2=0.54, F=5.14***）。该研究运用高光谱技术实现对白羊草群落养分含量的快速精准估测，在氮磷含量及其比值与光谱特征参数存在显著相关性的基础上，成功筛选出建立模型精度最高的参数组合，为大面积监测氮磷添加后草地养分含量方法和参数选择奠定了基础。
关键词：一阶导数；红边参数；植被指数；逐步回归；氮磷添加
Abstract：Exploring the relationship between spectral characteristics and nutrient content of the grassland communities is of great significance for promoting the application of rapid non-destructive testing technology in grassland fertilization management, which can be used to diagnose the nutritional status of the grassland communities by hyperspectral technology. A typical grassland community in the Loess Hilly-gully region on the Loess Plateau, Bothriochloa ischaemum community, was investigated with treatments of four nitrogen (N) addition (0, 25, 50, and 100 kg·N·ha-1·yr-1) and four phosphorus (P) addition treatments (0, 20, 40, and 80 P2O5·kg·ha-1·yr-1). Based on hyperspectral and community N and P nutrient content measurements, combined with the first derivative treatment in the red-edge region, 18 characteristicspectral parameters consisting of vegetation indexes, characteristic bands and red-edge parameters, the characteristicspectral parameters sensitive to the N and P content and N∶P ratio of B. ischaemum community were screened by multiple linear stepwise regression (SWR) methods, and an inverse model was established to estimate the aboveground total N content and total P content and N∶P ratio in the community. Results showed that the N and P content of the B. ischaemum community increased with N application, and the N∶P ratio decreased with P application; the spectral reflectance under N and P addition is inversely proportional to fertilizer application in the visible band and positively proportional to fertilizer application in the near-infrared band, and the “double-peak phenomenon” of the first derivative in the red-edge region was significantly affected by N and P addition. Among them, TBSI, R910 and AMP contributed significantly to the model for N estimation (R2=0.87, F=18.8***), while DVI, mSR705, R430, R660 and AMP contributed significantly to the model for P estimation (R2=0.91, F=20.51***), and Slope725 contributed the most to the model for the estimation of N∶P ratio (R2=0.54, F=5.14***). This study used hyperspectral technology to achieve a rapid estimation of the N and P content of the B. ischaemum community, and based on the significant correlation between N and P content and N∶P ratio and spectral feature parameters, the parameter combination with the highest accuracy was selected, which laid a foundation for the method and parameter selection of monitoring grassland nutrient content after N and P addition at large scale.
Key words：First derivative; Red edge parameters; Vegetation index; Stepwise regression; N and P addition
王绍妍，陈志飞，罗 杨，简春霞，周俊杰，靳 媛，许培丹，雷斯越，徐炳成. 基于光谱特征的黄土丘陵区白羊草群落养分含量研究[J]. 光谱学与光谱分析, 2023, 43(05): 1612-1621.
WANG Shao-yan, CHEN Zhi-fei, LUO Yang, JIAN Chun-xia, ZHOU Jun-jie, JIN Yuan, XU Pei-dan, LEI Si-yue, XU Bing-cheng. Study on Nutrient Content of Bothriochloa Ischaemum Community in the Loess Hilly-Gully Region Based on Spectral Characteristics. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2023, 43(05): 1612-1621.
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