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.