Abstract: The sources of N₂O ,one of the major greenhouse gases in the atmosphere,are still unclear till now. It was previously considered that only soil microbial process produced N₂O . In previous studies on N₂O emission from forest ecosystems,only measurements of N₂O emission from soil were conducted. The total N₂O emission from forest ecosystem may be underestimated if plants can emit N₂O under natural condition. The aim of this study was to provide evidences that plant per se,besides forest soil,is also an important source of the atmospheric N₂O in a forest ecosystem. Using the closed bag technique,the in situ measurements of N₂O emissions from branches and leaves of Fraxinus mandshurica,Pinnus koraiensis and Tilia amurrensis were conducted in a mixed broad-leaved Korean pine forest. The contribution of N₂O emission from trees in forest ecosystems was firstly estimated based on N₂O emission rates from these three tree species and soil in mixed broad-leaved Korean pine forest. The annual average of N₂O emissions from trees in mixed broad-leaved Korean pine forest was 0.8～1.03 times of that from soil. It was found that N₂O emission from trees were equal to or higher than N₂O emission from forest soil.

Key words: Pig manure, Composting, Microbial agent, NH₃