On allowing for transient variation in end‐member δ13C values in partitioning soil C fluxes from net ecosystem respiration
On allowing for transient variation in end‐member δ13C values in partitioning soil C fluxes from net ecosystem respiration
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DOI：
10.1111/ejss.13177
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发表时间：
2021-09
影响因子：
4.2
通讯作者：
C. McCloskey;W. Otten;E. Paterson;G. Kirk
中科院分区：
文献类型：
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作者：
C. McCloskey;W. Otten;E. Paterson;G. Kirk
利用稳定同位素分析将生态系统的呼吸分解为植物和土壤成分，取决于终端成员的同位素特征(δ13C)的好坏。一般来说，假定终端成员的值随着时间的推移是恒定的。然而，随着环境条件的变化，终端成员中必然会有日变化和其他瞬时变化。我们利用固定的和昼夜变化的植物和土壤δ13C端元，分析了生长在C3土壤中的C4草的生态系统呼吸及其δ13C的日和季节格局。我们独立地衡量终端成员，并评估预期价值变化的影响。我们发现，在植物生长旺盛时期，末端成员在实际范围内的变化，特别是植物末端成员的日变化，可以导致40%的分配误差。其影响取决于终端部件与测量的净呼吸δ13C的接近程度，即该终端部件的呼吸所占比例。我们发现，植物末端成员的光驱动变化会导致日尺度上分割土壤有机质(SOM)通量模式的严重扭曲，并导致对每日到年度SOM周转量的低估，约为25%。我们的结论是，虽然独立测量终端成员值在一个生长季节的全部时间变化是不可行的，但可以通过使用日变化的δ13C来调整这一误差。
The use of stable isotope analysis to resolve ecosystem respiration into its plant and soil components rests on how well the end‐member isotope signatures (δ13C) are characterised. In general, it is assumed that end‐member values are constant over time. However, there are necessarily diurnal and other transient variations in end‐members with environmental conditions. We analyse diurnal and seasonal patterns of ecosystem respiration and its δ13C in a C4 grass growing in a C3 soil using fixed and diurnally varying plant and soil δ13C end‐members. We measure the end‐members independently, and we assess the effects of expected variation in values. We show that variation in end‐members within realistic ranges, particularly diurnal changes in the plant end‐member, can cause partitioning errors of 40% during periods of high plant growth. The effect depends on how close the end‐member is to the measured net respiration δ13C, that is, the proportion of the respiration due to that end‐member. We show light‐driven variation in plant end‐members can cause substantial distortion of partitioned soil organic matter (SOM) flux patterns on a diurnal scale and cause underestimation of daily to annual SOM turnover of approximately 25%. We conclude that, while it is not practicable to independently measure the full temporal variation in end‐member values over a growing season, this error may be adjusted for by using a diurnally varying δ13Cplant.