Modelling minirhizotron observations to test experimental procedures

In order to help design experiments with minirhizotrons or interpret data from such experiments, a modelling approach is a valuable tool to complement empirical approaches. The general principle of this modelling approach is to calculate and to study the part of a theoretical root system that is intersected by passes through a virtual minirhizotron tube (modelled here as a cylinder). Various outputs can be calculated from this part of the root system, and related to the surrounding root system which is perfectly known, since it has been simulated and stored in a data structure. Therefore, the method involves two levels of modelling that are presented and discussed: the root system architecture of a crop, and the observations that can be achieved with minirhizotron tubes. Illustrations of the method are presented to study the effect of several factors on the rooting depth curves, and to show how images may be calculated to mimic what can actually be viewed from inside the tube. These first results show that the maximum rooting depth curves, as virtually observed in the minirhizotron tube, present large variations and strongly underestimate the maximum rooting depth of the modelled root system (up to 60 cm in average). The underestimation is still more critical when the radius of the tube is lower than 3 cm, and when the tube is close to the vertical (angle lower than 0.2 rad). The use of the 0.9 quantile instead of the average value, for each of the observation dates, leads to a better estimation of the maximum rooting depth.

[1]  H. Berge,et al.  Simulation of Ecophysiological Processes of Growth in Several Annual Crops , 1989 .

[2]  Loïc Pagès,et al.  Evaluation of parameters describing the root system architecture of field grown maize plants (Zea mays L.) , 1994, Plant and Soil.

[3]  H. M. Taylor.  Minirhizotron observation tubes : methods and applications for measuring rhizosphere dynamics , 1987 .

[4]  L. Pagès,et al.  Evaluation of parameters describing the root system architecture of field grown maize plants (Zea mays L.) , 1994, Plant and Soil.

[5]  Loïc Pagès,et al.  Study of differences between vertical root maps observed in a maize crop and simulated maps obtained using a model for the three-dimensional architecture of the root system , 1996, Plant and Soil.

[6]  J. Groenwold,et al.  The Relation between Root Growth along Observation Tubes and in Bulk Soil , 2015 .

[7]  T. Wells.  Methods of studying root systems: By W. Böhm, Ecological Studies No. 33 Springer-Verlag, Berlin, Heidelberg, New York. 1979. 188 pp. Price: DM69, US$38·80 , 1981 .

[8]  G. Berntson.  Modelling root architecture: are there tradeoffs between efficiency and potential of resource acquisition? , 1994 .

[9]  D. R. Upchurch.  Conversion of Minirhizotron-Root Intersections to Root Length Density 1 , 1987 .

[10]  Dr. Wolfgang Böhm.  Methods of Studying Root Systems , 1979, Ecological Studies.

[11]  J. Hopmans,et al.  Simultaneous modeling of transient three-dimensional root growth and soil water flow , 1994, Plant and Soil.

[12]  L. Pagès,et al.  Evaluation in field conditions of a three-dimensional architectural model of the maize root system: Comparison of simulated and observed horizontal root maps , 2004, Plant and Soil.

[13]  A. J. Diggle,et al.  An experimental procedure for obtaining input parameters for the “ROOTMAP” root simulation program for peas (Pisum sativum L.) , 2004, Plant and Soil.

[14]  A. G. Bengough,et al.  Relations between root length densities and root intersections with horizontal and vertical planes using root growth modelling in 3-dimensions , 1992, Plant and Soil.

[15]  Don Kulasiri,et al.  Simulation of Pinus Radiata Root System Structure for Ecosystem Management Applications , 1994, Simul..

[16]  H. M. Taylor,et al.  Ways of Using Endoscopy to Determine Growth and Quality of Root Systems , 1987 .

[17]  Joe T. Ritchie,et al.  Root Observations Using A Video Recording System In Mini‐Rhizotrons1 , 1983 .

[18]  Pavel Grabarnik,et al.  Geometrical properties of simulated maize root systems: consequences for length density and intersection density , 1998, Plant and Soil.

[19]  L. Pagès,et al.  A simulation model of the three-dimensional architecture of the maize root system , 1989, Plant and Soil.

[20]  K. Pregitzer,et al.  Spatial variation in tree root distribution and growth associated with minirhizotrons , 1992, Plant and Soil.

[21]  Loïc Pagès,et al.  Modélisation de l'architecture racinaire , 1995 .

[22]  J. Vos,et al.  Estimation of root densities by observation tubes and endoscope , 1983, Plant and Soil.