Effect of strip thinning on rainfall interception in a Japanese cypress plantation

- The changes in rainfall partitioning induced by 50% strip thinning were evaluated.
- The changes in interception processes using revised Gash model were quantified.
- Literatures on thinning effects on interception were reviewed.
- The reduction in interception was related to gross rainfall and thinning ratio.

SummaryWe examined the effect of strip thinning on rainfall interception (Ei) in a 32-year-old Japanese cypress plantation in central Japan. Strip thinning was conducted in the catchment in October 2011; that removed 50% of the stems. The gross precipitation (Pg), throughfall (TF) and stemflow (SF) were monitored in a 12-m × 13-m plot before and after thinning. Ei was calculated as the difference between Pg and the sum of TF and SF. The interception processes were illustrated using the revised Gash model with quantifying interception parameters. The results showed that the Gash model successfully predicted Ei on a rainy-season basis in both pre- and post-thinning periods. Thinning altered the interception components whereas the largest part during and after rainfall accounted for similar proportion in both periods. Additionally, after thinning, the annual TF rate was increased from 61.4% to 73.0%, whereas the annual SF rate was decreased from 9.8% to 6.1%, and the annual Ei rate was decreased from 28.7% to 20.8%. The summarized findings of previous studies indicate that the degree of decline in the Ei caused by thinning is related to Pg and the thinning ratio. These results provide useful information for understanding the changes in interception processes induced by thinning, and for acquiring a more accurate forecast of the effects of forest management practices on water resources in the watershed. The response in rainfall partitioning to strip thinning can also help us to acquire an integrated understanding of the changes in canopy water balance under different forest practices.