长白山阔叶红松林树木N_2O排放及总量初步估算

N_2O emission and preliminary estimation of annual N_2O emission from trees in mixed broad-leaved and Korean pine forest of Changbai Mountain

大气中主要温室气体N2 O的部分来源尚不清楚。以往国内外对森林生态系统N2 O排放通量的测定中 ,只测土壤通量而把树木排除在外。如果树木在自然状态下能排放N2 O ,那么森林生态系统的N2 O排放可能被低估。本文旨在证明自然状态下森林生态系统中树木也是N2 O的主要排放源。采用封闭罩法 ,在树木生长的主要季节 (7～ 9月 )对长白山阔叶红松林的几个主要树种———水曲柳、红松和椴树的连体枝叶释放N2 O的速率进行了原位测定。并在此基础上 ,初步估算出森林树木N2 O年排放量是土壤N2 O年排放量的 0 8～ 1 0 3倍 ,相当于甚至超过了土壤的N2 O排放量。

The sources of N 2O,one of the major greenhouse gases in the atmosphere,are still unclear till now. It was previously considered that only soil microbial process produced N 2O. In previous studies on N 2O emission from forest ecosystems,only measurements of N 2O emission from soil were conducted. The total N 2O emission from forest ecosystem may be underestimated if plants can emit N 2O 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 N 2O in a forest ecosystem. Using the closed bag technique,the in situ measurements of N 2O 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 N 2O emission from trees in forest ecosystems was firstly estimated based on N 2O emission rates from these three tree species and soil in mixed broad-leaved Korean pine forest. The annual average of N 2O emissions from trees in mixed broad-leaved Korean pine forest was 0.8～1.03 times of that from soil. It was found that N 2O emission from trees were equal to or higher than N 2O emission from forest soil.