自然状态下树木排放N_2O的研究

N_2O Emission by Trees under Natural Condition

大气中主要温室气体之一N2 O的部分来源尚不清楚 ,以前认为只有土壤微生物过程是N2 O的生物源 ,本文则旨在证明自然状态下植物也是N2 O的排放源 .采用同步空气样品采集装置和气相色谱仪观测了长白山阔叶红松林内空气N2 O的垂直分布特征 ,发现林冠或其附近处出现高N2 O浓度 ,高N2 O浓度比同一时刻其他高度处的正常N2 O浓度高 3 0 3%～ 64 9% ,差异显著或极显著 .在林冠高度处的高N2 O浓度和树干高度处的正常N2 O浓度同时存在的现象证明了植物向外排放N2 O ,即植物自身在自然状态下是N2

The sources of N 2O, one of the major greenhouse gases in the atmosphere, are still unclear till now. It was previously thought that only soil microbial process produced N 2O. The aim of this study was to provide evidences that plant can emit N 2O under the natural condition. The measurement of aboveground vertical profiles of N 2O concentrations were conducted within coniferous deciduous mixed forests in Changbai Mountain, China. Significant high N 2O concentrations were found at or near the height of canopy. High concentrations in profiles were 3.03% to 649% higher than the “normal concentrations'. Differences between the high concentrations and the “normal concentrations' were statistically significant. The simultaneous occurrence of high concentrations at/nearby the canopy height and normal concentrations at the trunk space height indicated an efflux of N 2O from foliage to atmosphere. This study afforded evidences supporting that plant per se, besides forest soil, was an important source of atmospheric N 2O in a forest ecosystem.