菌根真菌在陆地生态系统碳循环中的作用

陈保冬, 付伟, 伍松林, 朱永官

Involvements of mycorrhizal fungi in terrestrial ecosystem carbon cycling

CHEN Bao-Dong, FU Wei, WU Song-Lin, ZHU Yong-Guan

图1 菌根真菌在陆地生态系统碳循环中的作用。菌根真菌促进植物养分和水分的吸收, 间接促进植物生长和光合作用(A), 同时植物将一部分光合产物通过根系直接输送给菌根真菌(B), 供其增殖生成①真菌生物质和菌丝际分泌物等(如②稳定的土壤糖蛋白球囊霉素和黑色素等), 广泛参与土壤有机质的形成和稳定过程(C); 菌根真菌参与形成的有机质可以被③土壤团聚体包裹(物理保护作用)或与④土壤矿物结合(化学保护作用)被稳定在土壤系统中; 菌根真菌通过⑤分泌胞外酶、与⑥菌丝际微生物互作、驱动菌丝际⑦芬顿反应和⑧激发效应等对土壤有机质进行分解和转化(D), 释放有机质中的氮(N)、磷(P)营养并通过菌丝输送给植物, 缓解植物营养限制(A); 此外, 菌根真菌也会通过自身以及其菌丝际微生物的异养呼吸作用消耗植物提供的光合碳(E), 并最终以CO2的形式释放到大气中。

Fig. 1 Involvements of mycorrhizal fungi in terrestrial ecosystem carbon cycling. Mycorrhizal fungi promote plant acquisition of mineral nutrients and water and thus facilitate plant growth and photosynthetic carbon sequestration (A), while plants transfer a significant portion of photoassimilates to mycorrhizal fungi via plant roots (B). Such plant-derived carbon supply sustains mycorrhizal fungal growth ① and hyphosphere exudates (e.g., stable glycoprotein glomalin and melanin ②) that play key roles in the formation and stabilization of soil organic matter (C). The organic substances formed by mycorrhizal fungi can be stabilized in soil by wrapping into soil aggregates (i.e., physical protection) ③ or by binding to soil minerals (i.e., chemical protection) ④. Mycorrhizal fungi decompose and transform soil organic matter (D) via enzymatic breakdown ⑤, stimulation of hyphosphere microbial communities ⑥, Fenton oxidation ⑦ and hyphosphere priming effect ⑧, and transfer nutrients, particularly nitrogen (N) and phosphorus (P), to plants (A). In addition, mycorrhizal fungi and hyphosphere microbial communities also consume plant-derived photosynthetic carbon through heterotrophic respiration (E) and release CO2 into the atmosphere.