GCB | 土壤微生物碳泵：从概念认识到实证评估

文献信息：

Zhu Xuefeng, Jackson Randall D, DeLucia Evan H, Tiedje James M, Liang Chao*. The soil microbial carbon pump: from conceptual insights to empirical assessments. Global Change Biology, 2020, 26(11): 6032-6039. DOI: 10.1111/gcb.15319

摘  要：全球土壤储碳量巨大，因此有机碳收支的微小变化都会显著影响大气碳含量和全球气候变化。最近提出的土壤微生物碳泵（soil microbial carbon pump, MCP）强调了土壤微生物在有机碳固存中的正效应，其将活性有机碳转化为较为稳定的合成代谢形式。然而，这一概念尚未得到数据支撑、评估及验证。本研究利用美国两大生物质能源研究项目进行的两个长期田间试验平台上微生物残体生物标志物氨基糖和有机碳的数据集，通过研究土壤微生物残体与土壤有机碳（SOC）对土地利用方式的非同步响应来验证土壤MCP概念。微生物残体在土壤中优先累积，是多种多年生生物能源作物有机碳累积的主要贡献者。具体来说，相比于多样性较低的能源作物，多样性较高的能源作物能够提高SOC储量，且增加的SOC中约有92%来自于微生物残体；当土地利用方式从一年生能源作物转变为多年生能源作物种植时，增加的SOC中约有76%来自于微生物残体。上述结果表明，地上多样性较高的多年生能源作物种植能够刺激土壤MCP周转。鉴于土壤微生物残体与SOC的结果可以评价微生物同化代谢产物的积累及其对土壤固碳贡献，本文进而提出了土壤MCP转化能力（capacity）和效率（efficacy）这两个概念参数，以期在全球变化背景下，更有效地作为评估土地管理对土壤SOC储量影响的表征指标。

Figure 1 Brief illustration of soil organic carbon (C) formation paradigms that demonstrate microbial activity to “process” C, in which the evolved understanding highlights microbial ability to produce long‐lasting compounds that accumulate in soil. Arrows represent fluxes among pools. Traditional knowledge of soil C formation focused on partial degradation of plant detritus by microbial catabolism (black lines), as shown in the left‐hand panel. However, there is mounting evidence that microbial anabolism (red lines) also plays an important role—microorganisms can directly transform C into persistent forms via necromass depositions, as shown in the right‐hand panel. The thickness of the arrow representing pathways may vary depending on the ecosystems

Figure 2 Illustration of the changes in microbial necromass carbon (C) and soil organic carbon (SOC). Changes to 100 cm depth under restored perennial grassland communities sown with two levels of plant species richness at the Wisconsin Integrated Cropping Systems Trial (WICST), where the “additional SOC” pool under high diversity prairie was comprised of ~92% microbial necromass C (a); after 6 years of alternative bioenergy cropping systems in the University of Illinois Energy Farm (UIEF), where the “additional SOC” pool under swichgrass was comprised of ~76% microbial necromass C and under mixed prairie was ~93% (b)

Figure 3 Relative changes in amino sugars (AS) and soil organic carbon (SOC). Relative changes in AS and SOC to 100 cm depth under restored perennial grassland communities sown with two levels of plant species richness at the Wisconsin Integrated Cropping Systems Trial (WICST; a), and alternative bioenergy cropping systems in the University of Illinois Energy Farm (UIEF) after 6 years (b), where the WICST calculates the relative changes between diversity treatments and the UIEF calculates the relative changes between years within each cropping system (see Supplementary File S3 for specific calculations). In (a), HD and LD mean high and low diversity plantings, respectively. In (b), MMS means maize–maize–soybean rotation