[A-HW26] Hydrological processes of surface-groundwater interactions

[AHW26-P02] The effect of stand age on evapotranspiration of Japanese cypress forest

*Saumya Prasadi Abeysinghe¹、Tomohiro Egusa¹ (1.Shizuoka University)

キーワード：Hinoki, Chamaecyparis obtusa, Transpiration, Canopy interception, Soil water balance method

Artificial forests in Japan have continued to age, with many stands now well over 50 years old. Aging forests face unique challenges related to forest management due to their changing structural and physiological characteristics over time, which have implications for the use of water, carbon sequestration, and ecosystem function in general. Understanding the water cycle in aging forests, especially evapotranspiration, is crucial for dealing with these challenges. Our Research objective was to clarify the effect of stand age on the evapotranspiration characteristics of Japanese cypress forest. We targeted adjacent 50-year-old and 100-year-old Japanese cypress stands in Tenryu Experimental Field, Shizuoka University. Stand density was 2400 and 1000 stems per hectare for 50 year-old and 100-year-old Japanese cypress stands, respectively. We quantified the sum of transpiration and forest floor evaporation (Tr) rates using the soil water balance method. Soil water contents were measured at three depths up to 80 cm with 3–5 repetitions. We calculated soil water storage up to 80 cm and subtracted estimated infiltration rates from the temporal changes in soil water storage to quantify Tr rates. We quantified the interception (Ic) rate by measuring precipitation, throughfall, and stem flow. We set up 9–10 plastic bottles and 3–4 tipping-bucket rain gages for throughfall and stem flow, respectively. The 100-year-old stand had a slightly higher Tr rate than the 50-year-old stand. Conversely, the 100-year-old stand had a lower Ic rate than the 50-year-old stand. The difference in stand density and leaf area index between the two plots will explain the difference in evapotranspiration.