基于红边参数的水浇地与旱地春小麦各生育期叶绿素最佳估测模型比较研究

Comparison of red-edge parameters for spring wheat chlorophyll content at different growth stages in irrigated and dry-land regions

  • 摘要: 通过分析水浇地与不同类型旱地春小麦红边参数变化规律, 利用与春小麦叶绿素含量相关性最好的红边位置, 分别建立水浇地与旱地春小麦叶绿素含量最佳估测模型。结果表明: 春小麦的红边位置表现出水浇地>阴坡旱地>半阴/阳坡旱地>阳坡旱地的特点。起身期到扬花期, 各地类春小麦红边位置均偏向长波方向, 扬花至乳熟期, 又偏向短波。水浇地与阴坡旱地春小麦的红边在起身期和乳熟期存在"单峰"现象, 而在其他各期均为"双峰"; 半阴/阳坡旱地在抽穗和扬花期"双峰"明显, 在起身、拔节和乳熟期表现出"单峰"现象; 阳坡地在各生育期均为"单峰"现象。整个生育期, 水浇地春小麦的红边面积最大, 阳坡地的最小。起身期至乳熟期, 水浇地与旱地春小麦叶绿素含量线性模型的拟合R2和检验R2均大于0.81, RMSE均小于1.70, 说明可以利用红边位置预测各地春小麦叶绿素含量。

     

    Abstract: Red edge parameters were used to estimate chlorophyll content of spring wheat in irrigated land and dry land regions. The study analyzed the determination processes of canopy spectral, chlorophyll content, leaf width and seedling height of spring wheat in different regions, irrigated land and dry land regions. Then the strongest correlation between red edge position and chlorophyll content of spring wheat in different regions was used to establish optimally efficient models for simulating chlorophyll content in irrigated and dry lands. The results showed that red edge position of irrigated land was highest, followed by dry land in shady slope, then dry land in half shady/sunny slope and dry land in sunny slope. The red edge positions of spring wheat grown at different lands were deviated to long wave from setting to flowering stages, and to short wave from flowering to milking stages. The peak value of red edge of spring wheat in irrigated land and dry land in shady slope followed a "unimodal" curve at setting and milking stages, and a "dimodal" curve at other stages. The peak value of red edge of spring wheat grown at dry land in half shady/sunny slope also followed a "dimodal" curve at heading and flowering stages, and "unimodal" curve at setting, joining and milking stages. "Unimodal" curve was outstandingly a unique feature of dry land in sunny slope for all the growth stages of spring wheat. The red edge area of spring wheat was largest at irrigated land, and smallest at dry land in sunny slope. Irrespective of the stage, a significant correlation was noted between chlorophyll content and red edge position of spring wheat. From setting stage to milking stage, the estimated determination coefficient of regression (R2) for irrigated land exceeded 0.82 with a root mean square error (RMSE) of less than 1.26. Then R2 for dry land spring wheat exceeded 0.81 (all correlation coefficients highly positive) with RMSE of less than 1.70. Thus it was possible to use red edge position to estimate chlorophyll content of spring wheat. The results provided new insights into the methods to using hyper-spectral information to monitor wheat growth and yield.

     

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