It would be a project report conducte by Dobbertin M, Jüngling E (2009) Totholzverwitterung und C-Gehalt. Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, 3 p which is currently not available in the internet anymore.
if you are not the/a (co-)author of a piece of research, it is not possible for you to add this piece to the RG site of a third party - even if this is a "scientific contributions by ..."-page of the author. However, you may, of course, reference or link this paper in your own publications or on your own website.
to my knowledge, the "Scientific contributions by x [while affiliated with y]"-pages are created automatically, i.e., by the RG algorithms. Of course, the system can only pick up publications which are available or at least fully referenced somewhere on the web. So, as always, the AI is only as good as the data it is fed with...