Temporal changes in soil pore space CO2 concentration and storage under permanent grassland
Temporal changes in soil pore space CO2 concentration and storage under permanent grassland
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DOI：
10.1016/j.agrformet.2006.11.006
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发表时间：
2007-01-15
影响因子：
6.2
通讯作者：
Fuhrer, J.
中科院分区：
文献类型：
--
作者：
Flechard, C. R.;Neftel, A.;Fuhrer, J.
利用埋在土壤不同深度的透气膜管，对永久性草地下土壤孔隙中的CO2浓度进行了为期3年的半连续测量，试图量化土壤CO2储量的时间变化。通过土壤剖面系统地观察到CO2浓度的日波动，下降到50厘米，平均日波动的模式和幅度取决于土壤和环境条件。对于中度到高土壤水分含量（SWC），土壤CO2浓度与土壤温度在昼夜的基础上，从土壤呼吸与温度的指数增加和移动的热力学气/水相平衡的结果呈正相关。在干燥条件下，然而，充满空气的孔隙CO2浓度往往是最低的下午晚些时候和最高的清晨，因此与土壤温度呈负相关。利用亨利定律和碳酸盐化学计算了土壤中充空气孔隙和充水孔隙的CO2储存量。存储估计是非常敏感的土壤pH值和土壤pH值作为土壤含水量的函数的参数化来自实地测量和存储计算方案中使用。土壤CO2储量随时间变化的瞬时速率与大气摩擦速度在干燥和中等潮湿的条件下呈负相关，但在非常潮湿的条件下，存储的变化主要是由土壤水分的垂直运动。这些数据表明，CO2可以在夜间积累在土壤中时，运输仅限于通过土壤层的分子扩散，风引起的压力泵送的结果在白天逐渐冲洗出来。这些发现可能有助于解释经常报道的u（*）依赖夜间涡动相关呼吸通量。(c)2006 Elsevier B. V.保留所有权利。
Carbon dioxide concentrations were measured semi-continuously in soil pore space under permanent grassland for a 3-year period, using gas-permeable membrane tubes buried at various depths in the soil, in an attempt to quantify temporal variations of Soil CO2 storage. Diurnal wavelike variations in CO2 concentration were observed systematically through the soil profile down to 50 cm, and the patterns and amplitude of mean diurnal waves depended on soil- and environmental conditions. For moderate to high soil water contents (SWC), Soil CO2 concentrations were positively correlated with soil temperature on a diurnal basis, resulting from an exponential increase of soil respiration with temperature and a shift in thermodynamic gaseous/aqueous phase equilibria. In dry conditions, however, air-filled porosity CO2 concentrations tended to be lowest in the late afternoon and highest in the early morning, and thus negatively correlated with soil temperature. The storage Of CO2 in soil was calculated in the air-filled and in the water-filled pore fractions using Henry's law and carbonate chemistry. Storage estimates were extremely sensitive to soil pH and a parametrisation of soil pH as a function of soil water content was derived from field measurements and used in the storage calculation scheme. Instantaneous rates of soil CO2 storage change with time were negatively correlated with atmospheric friction velocity in dry and moderately wet conditions, though in very wet conditions storage changes were dominated by vertical movements of soil water. The data suggest that CO2 can accumulate in the soil during the night when transport is restricted to molecular diffusion through soil layers, and that wind-induced pressure pumping results in a gradual daytime flushing out. These findings may help account for the oft-reported u(*)-dependence of night-time eddy covariance respiration fluxes. (c) 2006 Elsevier B.V. All rights reserved.