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分析不同氮素水平下夏玉米红边参数特征及其与叶绿素含量、干物质积累之间的相关性,建立基于红边参数的5种函数形式的色素含量、干物质积累估算模型。结果表明,玉米的冠层光谱红边具有“双峰”现象,随生育期推移,“双峰”现象先增强后减弱,开花期达到最大。红边位置随生育期向长波方向移动,呈现“红移”现象;开花后开始减小,呈现“蓝移”现象,且在施氮水平下,开花期至灌浆期之间出现“红边平台”现象。随着氮素水平的增加,红边位置(λred)变化不大,而红边幅值(D red)呈现逐渐增加的趋势。在相关分析中,红边位置与叶绿素a、叶绿素b、类胡萝卜素及叶绿素总量呈显著或极显著相关;红边幅值与干物质、叶绿素b相关性显著。通过建立的5种函数形式的估算模型得知,二项式函数回归模型优于线性、幂函数、指数以及对数回归模型等,估测精度较高,具有较好的预测能力。
The correlations between red edge parameters of summer maize and its relationship with chlorophyll content and dry matter accumulation under different nitrogen levels were analyzed. Five pigment content and dry matter accumulation estimation models based on red edge parameters were established. The results showed that the red edge of the canopy spectrum of maize had “double peak ” phenomenon. With the growth period, the phenomenon of “double peak ” increased and then decreased and the flowering period reached its maximum. The position of red edge shifted to the longwave direction with the growth period, showing the “red shift” phenomenon. After flowering, it began to decrease and presented the phenomenon of “blue shift”. Under the nitrogen application level, there appeared between flowering stage and filling stage “Red edge platform ” phenomenon. With the increase of nitrogen level, the red edge position (λred) did not change much, while the red edge edge (D red) tended to increase gradually. In the correlation analysis, the position of red edge was significantly or very significantly related to the contents of chlorophyll a, chlorophyll b, carotenoid and total chlorophyll. The correlation between the red edge amplitude and dry matter and chlorophyll b was significant. Through the established five kinds of functional form estimation model, we know that the binomial function regression model is better than linear, power function, exponential and logarithmic regression models, which has higher estimation accuracy and better predictive ability.