I have downloaded the attached MS Excel table and noticed that the information about the researcher names is missing. Since the Google Scholar data is public anyway, I find it a pity that we can not validate the results the authors got.
The principle used to select the representative soil scientists is of course crucial for the representation of soil science as scientific field. It appears that, in this article, the 340 representative researchers were selected randomly by the authors (I would have taken the whole IUSS list and then subset using some objective criteria, but this could be a lot of work).
Otherwise, I like the bibliometrics plot that reveal clear relationships between h-index and citation stats / age etc. Such models should be used to derive adjusted citation stats and h-index and get more relative, filtered measures of impact.