Springtime photoinhibition constrains regeneration of forest floor seedlings of Abies sachalinensis after a removal of canopy trees during winter

Mitsutoshi Kitao,Satoshi Ishibashi,Hisanori Harayama,Qingmin Han,Evgenios Agathokleous,Naoyuki Furuya,Akira Uemura

doi:10.1038/s41598-018-24711-6

Mitsutoshi Kitao, Satoshi Ishibashi + Show 5 more

Open Access

https://doi.org/10.1038/s41598-018-24711-6

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Abstract

A clear-cutting of canopy trees during winter often causes severe foliar damage during the following spring in forest floor seedlings of Abies sachalinensis, a typical shade-tolerant evergreen coniferous species. The maximum photochemical efficiency of photosystem II after an overnight dark adaptation showed a temporary decrease immediately before budbreak in 1-year-old shoots of A. sachalinensis seedlings grown under full sunlight in a nursery, suggesting “springtime photoinhibition” related to the phenology of evergreen coniferous species. In the field, a greater rate of canopy tree cutting during winter was associated with more severe photoinhibition in the following spring, immediately before budbreak, which subsequently resulted in a reduction in carbon gain in 1-year-old shoots, and consequently suppressed the growth of current-year shoots. Although photoinhibition under low temperature is a well-known factor to determine the survival rate of tree seedlings during winter in cool regions, the present study additionally proposes that the temporary increase in the susceptibility to photoinhibition in springtime i.e. “springtime photoinhibition” would be a constraint for the regeneration of coniferous seedlings especially when the canopy trees are removed during winter.

Highlights

Evergreen conifers are known to develop new shoots by utilizing photosynthates recently assimilated by pre-existing shoots in spring[1,2,3]
Multiple regression analysis was conducted to investigate the effects of day of year (DOY), Tmin, and integrated Photosynthetic photon flux density (PPFD) during the morning from sunrise to noon (PPFDint) on the seasonal change in Fv/Fm
The seasonal change in Fv/Fm around budbreak was well predicted by the former model, except for the apparently lower value of Fv/Fm observed on DOY 122 (Fig. 2)

Summary

Introduction

Evergreen conifers are known to develop new shoots by utilizing photosynthates recently assimilated by pre-existing shoots in spring[1,2,3]. A clear-cutting of canopy trees, commonly conducted during winter, results in severe foliar damage in the shade-acclimated forest floor seedlings of A. sachalinensis during the following spring, sometimes leading to plant death. This suggests that an increase in the irradiance during springtime would not necessarily produce a positive effect on the growth and survival of forest floor seedlings of A. sachalinensis[8,9]. A temporary increase in the susceptibility to freezing temperature (−5.5 °C, artificially imposed for simulating late frost) has been reported for 1-year-old shoots of Sakhalin spruce (Picea glehnii), an evergreen conifer species native to northern Japan, before the budbreak[10].

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