What is the basis of a bibliometric study and how can this kind of study be applied to the analysis of a scholarly journal.

in a few words:
Bibliometrics is a research method used in library and information science. It utilizes quantitative analysis and statistics to describe patterns of publication within a given field or body of literature.
Researchers may use bibliometric methods of evaluation to determine the influence of a single writer, for example, or to describe the relationship between two or more writers or works.
One common way of conducting bibliometric research is to use the Social Science Citation Index, the Science Citation Index or the Arts and Humanities Citation Index to trace citations.
Useful links and hints can be found at:
http://www.gslis.utexas.edu/~palmquis/courses/biblio.html