  We show that valuations on the ring R of holomorphic germs in dimension 2 may
be naturally evaluated on plurisubharmonic functions, giving rise to
generalized Lelong numbers in the sense of Demailly. Any plurisubharmonic
function thus defines a real-valued function on the set V of valuations on R
and--by way of a natural Laplace operator defined in terms of the tree
structure on V--a positive measure on V. This measure contains a great deal of
information on the singularity at the origin. Under mild regularity
assumptions, it yields an exact formula for the mixed Monge-Ampere mass of two
plurisubharmonic functions. As a consequence, any generalized Lelong number can
be interpreted as an average of valuations. Using our machinery we also show
that the singularity of any positive closed (1,1) current T can be attenuated
in the following sense: there exists a finite composition of blowups such that
the pull-back of T decomposes into two parts, the first associated to a divisor
with normal crossing support, the second having small Lelong numbers.
