Abstract
The increase of waterlogged environments at forests and urban greenery is of recent concern with the progress of climate change. Under waterlogging, plant roots are exposed to hypoxic conditions, which strongly affect root growth and function. However, its impact is dependent on various factors, such as waterlogging depth. Therefore, our objective is to elucidate effects of different waterlogging depths on Pinus thunbergii Parl., which is widely used for afforestation, especially at coastal forests. We conducted an experiment to examine growth and morphology of fine roots and transpiration using 2-year-old seedlings under three treatments, (1) control (no waterlogging), (2) partial waterlogging (partial-WL, waterlogging depth = 15 cm from the bottom), and (3) full waterlogging (full-WL, waterlogging depth = from the bottom to the soil surface, 26 cm). As a result, fine root growth and transpiration were both significantly decreased at full-WL. However, for partial-WL, fine root growth was significantly increased compared to control and full-WL at the top soil, where it was not waterlogged. Additionally, transpiration which had decreased after 4 weeks of waterlogging showed no significant difference compared to control after 8 weeks of waterlogging. This recovery is to be attributed to the increase in fine root growth at non-waterlogged top soil, which compensated for the damaged roots at the waterlogged bottom soil. In conclusion, this study suggests that P. thunbergii is sensitive to waterlogging; however, it can adapt to waterlogging by plastically changing the distribution of fine root growth.
Highlights
With the progress of climate change, it is predicted that precipitation regimes will change and extreme rainfall events will occur more frequently, increasing waterlogged environments (Kundzewicz et al, 2014)
There is a concern that P. thunbergii is sensitive to waterlogging and information on the effect of waterlogging is of urgent need
This study showed that different depths of waterlogging significantly affect spatial distribution of fine root growth during the waterlogging treatment
Summary
With the progress of climate change, it is predicted that precipitation regimes will change and extreme rainfall events will occur more frequently, increasing waterlogged environments (Kundzewicz et al, 2014). Forests have been gaining attention after the disastrous tsunami which occurred at pacific coast line of northeastern Japan in March 2011 (Sakamoto, 2012; Tanaka et al, 2013) Restoration of these sites is currently undergoing; in some cases, soil layers of the plantation growth base are of poor permeability and drainage due to the use of machinery (Ono et al, 2016), which results in waterlogged conditions after rainfall (Shinomiya et al, 2016). There is a concern that P. thunbergii is sensitive to waterlogging and information on the effect of waterlogging is of urgent need
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