Effects of biochar and litter on water relations of Japanese black pine (Pinus thunbergii) seedlings

ABSTRACT

Biochar is gaining increasing attention in the fields of forest rehabilitation, agriculture, etc. For evaluating biochar application to improve the rhizosphere environment of Japanese black pine (Pinus thunbergii) at harsh coastal environments, a pot experiment was carried out with a focus on ectomycorrhizal (ECM) symbiosis and water relations of seedlings. Another characteristic recently observed at coastal forests is the invasion of the locust (Robinia pseudoacacia), which can potentially increase soil nitrogen. In this study, four treatments were examined (biochar addition, litter addition, biochar and litter addition, and no addition [control]) to determine the effects of biochar and/or nitrogen-rich locust (Robinia pseudoacacia) litter application. Although effects of biochar and litter addition were not observed on ECM symbiosis rate and species composition, treatments with biochar addition, maintained xylem water potential (XWP) of needles for up to 2 weeks without irrigation, independent of litter addition. As biochar increased relative fine root biomass (fine root biomass/total root biomass), it can be considered that biochar was able to maintain needle XWP through increasing the relative amount of fine roots that can obtain water. Overall, these findings suggest that biochar application can help to maintain water relations of Japanese black pine by enhancing fine root growth.

KEYWORDS:

• Robinia pseudoacacia
• xylem water potential
• ectomycorrhizal symbiosis
• fine roots
• biochar

Acknowledgments

This research was financially supported in part by JSPS (Type A: 23255009 to FS). Prof. emeritus T. Kamitani (Niigata University) kindly offered information on forest decline with pine wilt disease and showed us the study sites of pine plantations along seacoast in Niigata prefecture, central Japan. We are grateful for his support. The field survey was done with the help of Mr. Don-Gyu Kam (Hokkaido University, present address: University of Helsinki). Statistics analyses were guided by Prof. E. Agathokleous (Hokkaido University, present address: Nanjing University of Information Science and Technology). English proofread was made by the Enago Academy. We are also very grateful to the anonymous reviewers who gave us fruitful comments.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Japan Society for the Promotion of Science [23255009].