**Kohei Koyama 1,2,\*,**†**, Hiroyuki Shirakawa 2,**†**,**‡ **and Kihachiro Kikuzawa <sup>2</sup>**


Received: 16 August 2020; Accepted: 30 November 2020; Published: 3 December 2020

**Abstract:** Research Highlights: We demonstrate the first quantitative evidence that the shoot shedding of fast-growing species growing in a high-light environment is part of the process of shoot redeployment into better-lit outer parts of the crown. Background and Objectives: Light foraging by redeploying organs from shaded regions of a tree crown into better-lit regions is considered to apply to both leaves and shoots. To date, however, this hypothesis has never been tested for shoots. Materials and Methods: We investigated the shoot dynamics of saplings of five deciduous woody species. We included fast-growing and slow-growing species (*Alnus sieboldiana* Matsum., *Castanea crenata* Siebold & Zucc., *Betula ermanii* Cham., *Acer distylum* Siebold & Zucc., and *Fagus crenata* Blume). Results: Shoots in the shaded regions of the crowns of the fast-growing trees showed higher mortality rates than those at better-lit positions. Because of the selective shedding of the shaded shoots, at the end of the growth period the light environment experienced by the shoots that survived until the following spring was similar to that at the early stage of the same growth period. By contrast, the slow-growing trees displayed slow and determinate growth, with a very low mortality rate of shoots at all positions in the crown. Conclusions: The rapid shoot turnover of the fast-growing species resulted in the redeployment of shoots into better-lit positions within the tree crown in a manner similar to the redeployment of leaves.

**Keywords:** branch lifespan; shoot lifespan; stem lifespan; branch shedding; shoot shedding; stem shedding; canopy; crown development; tree architecture; light foraging
