Previous studies have revealed that the sapwood area at stand scale (A) is an important factor determining changes in transpiration by canopy trees (E). This study examined changes in A for four to six years after thinning of two Japanese cedar and two cypress plantation sites, each having three or four plots with different thinning intensities and one control plot. We focused on whether there was a difference in A (δA) between a thinned plot and a control plot during the experimental period. We observed increased radial stem growth for plots with low stem density (N) due to intensive thinning. However, δA did not decrease to zero during the experimental period for any plot. The increased radial stem growth was not large enough to cancel the effect of low N due to thinning. These results imply that a lower E for thinned plantations as compared to non-thinned plantationsis remains for several years (more than 10 years, according to our results) after thinning and that thinning could be an effective method of reducing water consumption by canopy trees.
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