model for tree-ring analysis

Dear Listusers,

i had some difficulties in finding a proper model in R for my work in a 
tree-ring analysis. Still working on statistical basics I'am asking here 
for some hints or tipps which will help me on my way to find a model I 
could use in R.

My data sample is a time-series of annual tree-ring widths as the 
response. Explanatory variables are three 2-Level factors 
(species,age,soil) and as continuous variables temperature, 
precipitation and an element input into the ecosystem.

At the end I want to find out, if there is an effect on the tree-ring 
width based on the interaction of the climate-data and the element input.

Best regards
Carsten