安吉毛竹林生长季CO_2浓度的时空特征

Spatiotemporal characteristics of CO_2 concentration in Phyllostachys edulis forest in Anji during growing season

试验采用7层CO2廓线系统对安吉毛竹林生长季(5—10月)CO2浓度进行连续监测,同时结合同步CO2通量和气象资料,分析安吉毛竹林CO2浓度的时空动态和CO2储存通量的变化特征。结果表明:安吉毛竹林生长季CO2浓度表现出明显的日变化、季节变化和垂直梯度。日尺度上,CO2浓度在日出前后达到最大,随后出现一段快速释放过程,午后达到全天最低值;整个生长季尺度上,7月份林间CO2浓度最低(368.1μmol·mol-1),10月份最高(402.6μmol·mol-1);垂直梯度方面,林冠上层CO2垂直梯度明显小于林冠层和林冠下层;林冠层和林冠上层垂直梯度变化趋势较为一致,白天均为正值,呈现为碳汇,夜间为负值,呈现为碳源,林冠下层CO2梯度全天均为负值。利用廓线系统计算毛竹林CO2储存通量,半小时和日尺度上,CO2储存通量分别占净生态系统CO2交换量(NEE)的25.5%和8.9%,而在月尺度上仅占NEE的0.22%。因此,在半小时及日尺度上计算NEE时不可忽略CO2储存通量,而在计算月尺度及更长时间尺度NEE时可以忽略CO2储存通量。

The C02 concentration of Phyllostachys edulis forest ecosystem during the growing sea- son （from May to October） was continuously measured using a 7-layer profile system in Anji, Zhejiang Province in 2011. The synchronized CO2 flux and meteorological data were applied to explore the temporal and spatial variations in the CO2 concentration and CO2 storage flux. The re- sults showed that the CO2 concentration of P. edulis forest during the growing season exhibited ob- vious diurnal and seasonal variations, as well as vertical variations. In a single day, the CO2 con- centration reached the maximum value at the daybreak, and decreased to the minimum value in the afternoon after a rapid emission process. In the entire growing season, the minimum CO2 con- centration of the forest appeared in July （368. I p, mol ~ tool-~ ）, and the maximum one emerged in October （402.6 p, mol ~ tool-X）. What＇s more, the CO2 vertical gradients above the canopy were lower than those in and below the canopy. The vertical gradients in and above the canopy showed a consistent variation trend： positive in the daytime （carbon sink） and negative at night （ carbon source）. However, the CO2 vertical gradients below the canopy were negative throughout the day. We found the proportion of the CO2 storage flux obtained from the profile system to net ecosystem CO2 exchange （NEE） was 25.5% and 8.9% at a half-hour and daily scale, respective-ly, but was only 0.22% at a monthly scale. be neglected when NEE was estimated at a monthly or longer time scale. The results suggested that CO= storage flux could not half-hour or daily scale, but could be ignored at a