Changes in the sapwood area of Japanese cedar and cypress plantations after thinning

Abstract

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.

Keywords:

• Japanese cedar
• Japanese cypress
• Sapwood area
• Thinning
• Transpiration

Acknowledgments

We acknowledge Dr. Kenji Tsuruta (Kyoto University, Japan) for providing data of the sapwood area at tree scale. Thanks are also due to two anonymous reviewers for their useful comments. This research was supported by a CREST project (Development of Innovative Technologies for Increasing in Watershed Runoff and Improving River Environment by the Management Practice of Devastated Forest Plantation).

Notes

Electronic supplementary material The online version of this article (doi:10.1007/s10310-014-0468-8) contains supplementary material available to authorized users.