中国草地N2O通量日变化观测对比研究

研究分析了我国20世纪90年代以来科学工作者利用静态箱-气相色谱法对内蒙古呼伦贝尔草原和锡林郭勒草原、青藏高寒草原等不同草原类型所开展的日变化通量观测数据并进行了对比分析研究.结果表明:我国草地N2O通量的日变化规律明显,日变化形式呈多峰型,我国草地均表现为N2O排放源,日均通量的对比顺序是:贝加尔针茅草甸草原>羊草草甸草原>羊草典型草原>高寒草甸(42.82±15.96)>(29.17±13.03)>(4.91±2.12)>(0.89±0.67)μg/(m2?h)];10:00~14:00和夜间0:00左右所观测的N2O通量均可代表当日平均通量;夜间N2O的排放对整个日通量有重要贡献,其排放量占到全日排放总量的46%以上,草地夜间N2O的排放通量应该受到重视.另外,本文讨论了水分和温度作为主要环境因子对N2O通量日变化的影响,以及不同植被类型和人类活动(放牧和刈割)对N2O通量的日变化的影响.

Comparison of diurnal variation of nitrous oxide fluxes from grassland of China

Diurnal variation characteristics of N2O fluxes from grasslands are compared and discussed in this paper. Measurements of N2O fluxes were curried out by using the static chamber method since 1990’s years of the last century for various types of grasslands in China, such as Hulun Buir meadow steppe, Xilin Gol semi-arid typical steppe in Inner Mongolia, Qinghai-Tibet Alpine meadow steppe. The results show that N2O emission fluxes from grasslands in China vary distinctly during a day and evident multi-peak diurnal variation characteristics have been displayed for N2O emission from all above mentioned steppes. Daily average of N2O fluxes are (42.82±15.96)μg/(m2?h)], (29.17±13.03)μg/(m2?h)], 3.43μg/(m2?h)] and(0.89±0.67)μg/(m2?h)] for S.baicalensis community in the meadow steppe, Leymus chinensis meadow steppe, native Leymus chinensis typical steppe and Alpine meadow steppe, respectively. Detailed analysis shows that N2O fluxes measured both during 10:00-14:00 of the daytime and at 0:00 of the nighttime can be represented as a daily mean value of the N2O flux. Moreover, N2O emission at nighttime accounts for about 46% of whole day’s N2O emission, so more attention should be paid to N2O emission at the nighttime. In addition, effects of various environmental and anthropogenic factors (such as soil water content, soil temperature and grazing , cutting as well ) on N2O emission from grasslands are analysed and discussed in the paper.