Retention of absorbed fog by Pinus thunbergii saplings under different soil drought conditions

Abstract Aim Efficient fog water utilization under soil drought conditions is important for improving the water status and growth of forest trees. However, the importance of fog water retention in tree species during drought is yet to be completely examined. The aim of this study was to examine changes in fog water retention in different organs of Japanese black pine (Pinus thunbergii) saplings in different drought conditions. Methods P. thunbergii saplings were grown under different watering conditions in a glasshouse for 19 days and exposed to 2H-enriched water vapor under a high relative humidity (~ 95%) for 1 h in a growth chamber with lighting. The exposed trees were harvested 48 h after the fog exposure experiment and the 2H concentration of water in current needles, old needles, current branches, old branches, roots, and soil was determined. Results Absorbed fog water was observed in the needles, branches, and roots 48 h after exposure to fog. The amount of water in the current needles, old needles, and current branches contributed by fog water was significantly higher in drought-stressed trees than in well-irrigated trees. Small amount of absorbed fog water was redistributed to the soil in well-irrigated and drought-stressed trees. Conclusion The findings of the study indicated that more absorbed fog water is retained in drought-stressed trees than that in well-watered trees, which may improve plant water status under drought. Our results also suggest that hydraulic redistribution from the roots to the soil may occur irrespective of soil drought conditions.