Modelling applicability of fractal analysis to efficiency of soil exploration by roots.

BACKGROUND AND AIMS Fractal analysis allows calculation of fractal dimension, fractal abundance and lacunarity. Fractal analysis of plant roots has revealed correlations of fractal dimension with age, topology or genotypic variation, while fractal abundance has been associated with root length. Lacunarity is associated with heterogeneity of distribution, and has yet to be utilized in analysis of roots. In this study, fractal analysis was applied to the study of root architecture and acquisition of diffusion-limited nutrients. The hypothesis that soil depletion and root competition are more closely correlated with a combination of fractal parameters than by any one alone was tested. MODEL The geometric simulation model SimRoot was used to dynamically model roots of various architectures growing for up to 16 d in three soil types with contrasting nutrient mobility. Fractal parameters were calculated for whole roots, projections of roots and vertical slices of roots taken at 0, 2.5 and 5 cm from the root origin. Nutrient depletion volumes, competition volumes, and relative competition were regressed against fractal parameters and root length. KEY RESULTS Root length was correlated with depletion volume, competition volume and relative competition at all times. In analysis of three-dimensional, projected roots and 0 cm slices, log(fractal abundance) was highly correlated with log(depletion volume) when times were pooled. Other than this, multiple regression yielded better correlations than regression with single fractal parameters. Correlations decreased with age of roots and distance of vertical slices from the root origin. Field data were also examined to see if fractal dimension, fractal abundance and lacunarity can be used to distinguish common bean genotypes in field situations. There were significant differences in fractal dimension and fractal abundance, but not in lacunarity. CONCLUSIONS These results suggest that applying fractal analysis to research of soil exploration by root systems should include fractal abundance, and possibly lacunarity, along with fractal dimension.

[1]  J. Lynch,et al.  Topsoil Foraging and Its Role in Plant Competitiveness for Phosphorus in Common Bean , 2003, Crop Science.

[2]  Jonathan P Lynch,et al.  The importance of root gravitropism for inter-root competition and phosphorus acquisition efficiency: results from a geometric simulation model , 2004, Plant and Soil.

[3]  K. L. Nielsen,et al.  Fractal geometry of bean root systems: correlations between spatial and fractal dimension. , 1997, American journal of botany.

[4]  W. B. Marks,et al.  Fractal methods and results in cellular morphology — dimensions, lacunarity and multifractals , 1996, Journal of Neuroscience Methods.

[5]  J. Neter,et al.  Applied Linear Regression Models , 1983 .

[6]  Akira Yamauchi,et al.  Fractal Analysis of Plant Root Systems , 1989 .

[7]  K. L. Nielsen,et al.  Fractal geometry of root systems: Field observations of contrasting genotypes of common bean (Phaseolus vulgaris L.) grown under different phosphorus regimes , 1999, Plant and Soil.

[8]  Robert D. Davis,et al.  SimRoot: Modelling and visualization of root systems , 2004, Plant and Soil.

[9]  J. W. Maranville,et al.  Evaluation of sorghum root branching using fractals , 1998, The Journal of Agricultural Science.

[10]  J. Lynch,et al.  Topsoil foraging – an architectural adaptation of plants to low phosphorus availability , 2001, Plant and Soil.

[11]  Alastair H. Fitter,et al.  Fractal Characterization of Root System Architecture , 1992 .

[12]  S. A. Barber,et al.  Phosphate Uptake by Corn as Affected by Soil Characteristics and Root Morphology 1 , 1979 .

[13]  A. Eshel,et al.  On the fractal dimensions of a root system , 1998 .

[14]  J. Lynch,et al.  Growth and architecture of seedling roots of common bean genotypes , 1993 .

[15]  Anne M. Parkhurst,et al.  Fractal Analysis for Morphological Description of Corn Roots under Nitrogen Stress , 1993 .

[16]  Application of Fractal Analysis for Tunnel Systems of Subterranean Termites (Isoptera: Rhinotermitidae) Under Laboratory Conditions , 2001 .

[17]  J. Lynch,et al.  Root Gravitropism and Below-ground Competition among Neighbouring Plants: A Modelling Approach , 2001 .