Stepwise regression and partial correlation for wildlife census time series

Dear List;

We are doing a time series analysis of wildlife census data. We use a
stepwise regression of the annual per capita rate of increase against
pervious years population size (log transformed) as suggested by Berryman &
Turchin (2001, Oikos 92:265-270). 

How can we obtain the partial correlation coefficients in R to make a plot
of them against the lag as in a standard PACF?

Yours Sincerely

Tomas Willebrand