Trench profile techniques and core break methods

This chapter describes methods for root observations made on mapping or counting root intersections with planes of observation in the soil. Normally these planes of observation are either vertical or horizontal. Compared with the methods based on washed root samples discussed in chapter 6, these “profile wall” methods have advantages as well as disadvantages. A major disadvantage of the profile wall methods is that only a small part of a root is visible on such an intersection and it is not easy to distinguish between roots of different species, or between live or dead roots. Even the question of whether a whitish thread like object sticking out of a plane is a root and not an enchytraeid (pot worm) or other soil organism may take some experience to answer ( pot worms move when touched). Creating access to planes of observation via trenches can be a rather destructive activity which is not welcome on small experimental plots, especially those intended for long term experiments. On the positive side, however, profile wall methods can give detailed information on spatial patterns of roots in their interaction with physical, chemical and biological characteristics of the soil profile. If maps are made of root occurrence as well as other readily observable feature, the toolbox of geographical information systems and quantitative map analysis can be used to analyze patterns, be it in two dimensions. In this chapter we will describe practical aspects of preparing profile walls for observations and various methods for recording data (Sect.7.2). In section 7.3 we will focus on the analysis of data obtained, especially for root maps, and discuss the inferences which can be made about three dimensional reality on the basis of two dimensional observations.

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