College of Forestry, Sichuan Agricultural University, Chengdu, China.
National Forestry and Grassland Administration Key Laboratory of Forest Resources Conservation and Ecological Safety on the Upper Reaches of the Yangtze River, College of Forestry, Sichuan Agricultural University, Chengdu, China.
Glob Chang Biol. 2022 Aug;28(16):4977-4988. doi: 10.1111/gcb.16226. Epub 2022 May 26.
The carbon use efficiency (CUE) of soil microorganisms is a critical parameter for the first step of organic carbon (C) transformation by and incorporation into microbial biomass and shapes C cycling in terrestrial ecosystems. As C and nitrogen (N) cycles interact closely and N availability affects microbial metabolism, N addition to soil may shift the microbial CUE. We conducted a meta-analysis (100 data pairs) to generalize information about the microbial CUE response to N addition in soil based on the two most common CUE estimation approaches: (i) C-labelled substrate addition ( C-substrate) and (ii) O-labelled water addition ( O-H O). The mean microbial CUE in soils across all biomes and approaches was 0.37. The effects of N addition on CUE, however, were depended on the approach: CUE decreased by 12% if measured by the C-substrate approach, while CUE increased by 11% if measured by the O-H O approach. These differences in the microbial CUE response depending on the estimation approach are explained by the divergent reactions of microbial growth to N addition: N addition decreases the C incorporation into microbial biomass (this parameter is in the numerator by CUE calculation based on the C-substrate approach). In contrast, N addition slightly increases (although statistically insignificant) the microbial growth rate (in the numerator of the CUE calculation when assessed by the O-H O approach), significantly raising the CUE. We explained these N addition effects based on CUE regulation mechanisms at the metabolic, cell, community, and ecosystem levels. Consequently, the differences in the microbial responses (microbial growth, respiration, C incorporation, community composition, and dormant or active states) between the C-substrate and O-H O approaches need to be considered. Thus, these two CUE estimation approaches should be compared to understand microbially mediated C and nutrient dynamics under increasing anthropogenic N input and other global change effects.
土壤微生物的碳利用效率（CUE）是有机碳（C）转化为微生物生物量并影响陆地生态系统碳循环的第一步的关键参数。由于 C 和氮（N）循环密切相关，且 N 供应影响微生物代谢，因此向土壤中添加 N 可能会改变微生物的 CUE。我们进行了一项荟萃分析（100 对数据），根据最常用的两种 CUE 估计方法（i）13C 标记底物添加（C-substrate）和（ii）18O 标记水添加（O-H O），概括了土壤中微生物 CUE 对 N 添加的响应信息。所有生物群落和方法的土壤微生物平均 CUE 为 0.37。然而，N 添加对 CUE 的影响取决于方法：如果通过 C-substrate 方法测量，CUE 降低 12%，而如果通过 O-H O 方法测量，CUE 增加 11%。这种基于不同估计方法的微生物 CUE 响应差异是由微生物对 N 添加的不同反应引起的：N 添加会降低 13C 掺入微生物生物量的量（根据 C-substrate 方法计算 CUE 时，该参数在分子中）。相反，N 添加略微增加（尽管统计上不显著）微生物生长速率（通过 O-H O 方法评估时 CUE 计算的分子），显著提高 CUE。我们基于代谢、细胞、群落和生态系统水平的 CUE 调节机制解释了这些 N 添加效应。因此，需要考虑 C-substrate 和 O-H O 方法之间的微生物响应（微生物生长、呼吸、13C 掺入、群落组成和休眠或活跃状态）差异。因此，应该比较这两种 CUE 估计方法，以了解在人为 N 输入增加和其他全球变化影响下微生物介导的 C 和养分动态。
