Soybean Canopy Development as Affected by Population Density and Intercropping with Corn: Fractal Analysis in Comparison with Other Quantitative Approaches
1999
Foroutan-pour, Kayhan | Dutilleul, Pierre | Smith, Donald L.
To better understand how crops intercept light, the complexity of plant structure needs to be characterized. Fractal analysis provides a novel approach for quantifying the geometric structure of individual plants. The objectives of this study were to determine (i) an appropriate methodology for estimating fractal dimension (FD) two-dimensionally for complex three-dimensional structures of plants such as soybean [Glycine max (L.) Merr.]; (ii) whether the temporal pattern of FD for soybean structure is altered by population density or intercropping with corn (Zea mays L.); and (iii) how the FD for soybean structure compares with other quantitative measures of shoot development. Soybean plants were randomly sampled in monocropped soybean and intercropped corn-soybean plots grown at the same site in three successive years. Sampled plants were cut at the stem base, and leaf blades were immediately detached. Leafless plant structure was photographed from the side which allowed maximum appearance of branches and petioles. The FD was estimated two-dimensionally from the scanned and processed images. Fractal dimension of soybean leafless structure increased with time for all treatments, coincident with the increasing complexity of structure as shoots developed. The rate of linear increase of FD with time varied among treatments. Leaf area per plant, plant height, and number of leaves per plant increased with time for all treatments, indicating a positive correlation with FD. In contrast, light penetration decreased during canopy development, and was negatively correlated with FD. Whereas leaf area evaluates the surface available for light interception, FD characterizes its geometric distribution in space.
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