EFFECT OF NITROGEN AND SOIL WATER ON LEAF RESPIRATION OF PINUS KORAIENSIS AND TILIA AMURENSIS SAPLINGS IN A TEMPERATE FOREST

. Leaf respiration drives plant energy use and greatly influences global carbon balance. It is inhibited by light. The climate-driven effects of changes in nitrogen deposition and soil moisture on leaf respiration in light ( R L ) are not well understood. To better understand the response of R L and its inhibition by light, we experimentally determined R L and light inhibition degree, an index of the inhibitory effect of light on leaf respiration with respect to dark leaf respiration, for potted specimens of an evergreen conifer species ( Pinus koraiensis ) and a deciduous broadleaved species ( Tilia amurensis ) in Changbai Mountains forests that were subjected to soil nitrogen and moisture treatments. R L increased as nitrogen deposition increased to a particular level (46 kg/ha/y N), when enzymes and mineral nutrients became imbalanced. R L decreased as soil moisture decreased to a drought level. Light inhibition degree behaved inversely to R L , and the average range for both species combined was 42.0%–78.4% for nitrogen treatments and 58.3%–87.0% for soil moisture treatments. The results are fundamental to accurate modeling of terrestrial carbon budgets and assessment of the carbon economy in forest ecosystems in a rapidly changing climate.