Zhang Xin, Lee Xuhui, Griffis Timothy J, Baker John M, Erickson Matt D, Hu Ning, Xiao Wei
School of Forestry and Environmental Studies, Yale University, New Haven, CT, USA,
Int J Biometeorol. 2014 Jul;58(5):819-33. doi: 10.1007/s00484-013-0662-y. Epub 2013 Apr 24.
The primary objective of this study was to clarify the influence of crop plants on atmospheric methane (CH4) in an agriculture-dominated landscape in the Upper Midwest of the United States. Measurements were carried out at two contrasting scales. At the plant scale, CH4 fluxes from soybean and corn plants were measured with a laser-based plant chamber system. At the landscape scale, the land surface flux was estimated with a modified Bowen ratio technique using measurements made on a tall tower. The chamber data revealed a diurnal pattern for the plant CH4 flux: it was positive (an emission rate of 0.4±0.1 nmol m(-2) s(-1), average of soybean and corn, in reference to the unit ground area) during the day, and negative (an uptake rate of -0.8±0.8 nmol m(-2) s(-1)) during the night. At the landscape scale, the flux was estimated to be 14.8 nmol m(-2) s(-1) at night and highly uncertain during the day, but the available references and the flux estimates from the equilibrium methods suggested that the CH4 flux during the entire observation period was similar to the estimated nighttime flux. Thus, soybean and corn plants have a negligible role in the landscape-scale CH4 budget.
本研究的主要目的是阐明美国中西部上游以农业为主的景观中农作物对大气甲烷（CH4）的影响。测量在两个不同尺度上进行。在植物尺度上，使用基于激光的植物箱系统测量大豆和玉米植株的CH4通量。在景观尺度上，利用在高塔上进行的测量，采用修正的鲍文比技术估算地表通量。箱室数据揭示了植物CH4通量的日变化模式：白天为正（以单位地面面积计，大豆和玉米的平均排放率为0.4±0.1 nmol m(-2) s(-1)），夜间为负（吸收速率为-0.8±0.8 nmol m(-2) s(-1)）。在景观尺度上，夜间通量估计为14.8 nmol m(-2) s(-1)，白天高度不确定，但现有参考文献和平衡法的通量估计表明，整个观测期的CH4通量与估计的夜间通量相似。因此，大豆和玉米植株在景观尺度的CH4收支中作用可忽略不计。
