文獻信息：
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：全球土壤儲碳量巨大，因此有機碳收支的微小變化都會顯著影響大氣碳含量和全球氣候變化。最近提出的土壤微生物碳泵（soil microbial carbon pump, MCP）強調了土壤微生物在有機碳固存中的正效應，其將活性有機碳轉化為較為穩定的合成代謝形式。然而，這一概念尚未得到數據支撐、評估及驗證。本研究利用美國兩大生物質能源研究項目進行的兩個長期田間試驗平臺上微生物殘體生物標誌物氨基糖和有機碳的數據集，通過研究土壤微生物殘體與土壤有機碳（SOC）對土地利用方式的非同步響應來驗證土壤MCP概念。微生物殘體在土壤中優先累積，是多種多年生生物能源作物有機碳累積的主要貢獻者。具體來說，相比於多樣性較低的能源作物，多樣性較高的能源作物能夠提高SOC儲量，且增加的SOC中約有92%來自於微生物殘體；當土地利用方式從一年生能源作物轉變為多年生能源作物種植時，增加的SOC中約有76%來自於微生物殘體。上述結果表明，地上多樣性較高的多年生能源作物種植能夠刺激土壤MCP周轉。鑑於土壤微生物殘體與SOC的結果可以評價微生物同化代謝產物的積累及其對土壤固碳貢獻，本文進而提出了土壤MCP轉化能力（capacity）和效率（efficacy）這兩個概念參數，以期在全球變化背景下，更有效地作為評估土地管理對土壤SOC儲量影響的表徵指標。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