Inferring water and carbon exchanges from leaf carbon isotope composition of Quercus serrata and Carpinus laxiflora grown in a forest with a complex landscape in Korea

Using leaf carbon isotope monitoring as an indicator, carbon and water exchanges and their inter-dependencies were examined in the Gwangneung forest on a complex landscape in Korea. Leaf carbon isotope compositions (δ ¹³C) were measured for two dominant tree species, Quercus serrata and Carpinus laxiflora, from 2003 to 2005. Leaf δ ¹³C exhibited a consistent decrease in 2004 compared to that of 2003 and 2005 regardless of its species and growth heights. The decrease in δ ¹³C (and therefore the increase of the ratio between intercellular and ambient CO₂, C_i/C_a) was assumed to be the consequence of reduced productivity of the year, which was supported by complementary leaf nitrogen, biometric,micrometeorological and satellite-basedmeasurements. The estimation ofwater use efficiency (WUE) fromleaf carbon isotope composition was hampered mostly by the uncertainties in vapor pressure deficit of the air, the temperature difference between the air and leaf surface during photosynthesis, and the turnover rate of photosynthates in the leaves.