Δ13C trends measured for the 6 y before and the 7 y after thinning. Sample size was five at both the CCHF and the C sites. The figure shows the progressive Δ13C increase after the thinning (1995) when compared with Δ13C control site trends. Error bars indicate the standard error of the mean values. The dashed line indicates the date the forest was thinned to convert it to high forest.