ENGLISH ABSTRACT: A subset X ⊆ V of the vertex set V of a graph G = (V,E) is an independent set in G if no two
vertices of V are adjacent in G. The cardinality of a largest independent set in G is called
the independence number of G and is denoted by α(G). A non-empty graph G is p-stable if p
is the largest number of arbitrary edges that can be removed from G without changing the
independence number of the resulting graph, and q-critical if q is the smallest number of
arbitrary edges that have be removed from G in order necessarily to change the independence
number of the resulting graph. The classes of p-stable and q-critical forests (acyclic graphs) of
order n are characterised in this paper for all permissible values of p, q and n.