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 (RL) are not well understood. To better understand the response of RL and its inhibition by light, we experimentally determined RL 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. RL increased as nitrogen deposition increased to a particular level (46 kg/ha/y N), when enzymes and mineral nutrients became imbalanced. RL decreased as soil moisture decreased to a drought level. Light inhibition degree behaved inversely to RL, 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.