Small but active – pool size does not matter for carbon incorporation in below‐ground food webs
Small but active – pool size does not matter for carbon incorporation in below‐ground food webs
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DOI：
10.1111/1365-2435.12512
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发表时间：
2016-03
影响因子：
5.2
通讯作者：
J. Pausch;S. Kramer;Anika Scharroba;Nicole Scheunemann;Olaf Butenschoen;E. Kandeler;S. Marhan;M. Riederer;S. Scheu;Y. Kuzyakov;Liliane Ruess
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文献类型：
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作者：
J. Pausch;S. Kramer;Anika Scharroba;Nicole Scheunemann;Olaf Butenschoen;E. Kandeler;S. Marhan;M. Riederer;S. Scheu;Y. Kuzyakov;Liliane Ruess
摘要1.土壤食物网的复杂性和隐蔽的生境阻碍了对生物体内碳库、碳通量和碳周转率的分析以及对它们之间相互作用的深入了解。稳定同位素分析已越来越多地用于解开土壤食物网结构，但它还没有被应用到定量表征整个土壤食物网水平上的C动态。2.本研究采用13 CO2脉冲标记法，研究了玉米根源碳在耕地土壤中的主要成分和食物网参与者中的作用。散装组织和特定化合物（脂质）的碳同位素比率被用来量化池的大小和13 C掺入细菌和真菌作为主要的分解者，线虫作为微型食物网的关键驱动程序和中型和大型动物中的分解者和捕食者。3.玉米吸收的碳约有20%转移到地下库。13 C主要被纳入根际微生物，而不是在那些散装土壤。磷脂脂肪酸生物标志物中的13 C表明，根源C主要通过腐食真菌而不是通过细菌被纳入土壤食物网。只有少量的13 C被转移到更高的营养级，主要是进入真菌喂养线虫和大型底栖动物分解。4.最重要的是，C池大小和13C掺入并不紧密匹配。虽然真菌的碳储量不到细菌的一半，但碳从真菌转移到真菌能量途径的更高营养级，即以真菌为食的线虫和中型和大型底栖动物的分解者，远远超过细菌的碳。这挑战了以前的观点细菌在根C动力学的优势，并建议腐食真菌作为主要代理商通道最近的光合同化物进入土壤食物网。
Summary 1. The complexity of soil food webs and the cryptic habitat hamper the analyses of pools, fluxes and turnover rates of carbon (C) in organisms and the insight into their interactions. Stable isotope analysis has been increasingly used to disentangle soil food web structure, yet it has not been applied to quantitatively characterize C dynamics at the level of the entire soil food web. 2. The present study employed 13 CO2 pulse labelling to investigate the incorporation of maize root-derived C into major soil compartments and food web players in an arable field for 25 days. Bulk tissue and compound-specific (lipids) C isotope ratios were used to quantify pool sizes and 13 C incorporation in bacteria and fungi as primary decomposers, nematodes as key drivers of the microfood web and decomposers and predators among the meso- and macrofauna. 3. About 20% of the C assimilated by maize was transferred to below-ground pools. 13 C was predominantly incorporated into rhizosphere micro-organisms rather than in those of the bulk soil. 13 C in phospholipid fatty acid biomarkers revealed that root-derived C was incorporated into the soil food web mainly via saprotrophic fungi rather than via bacteria. Only small amounts of 13 C were transferred to higher trophic levels, predominantly into fungal-feeding nematodes and macrofauna decomposers. 4. Most importantly, C pool size and 13 C incorporation did not match closely. Although the fungal C stock was less than half that of bacteria, C transfers from fungi into higher trophic levels of the fungal energy pathway, that is fungal-feeding nematodes and meso- and macrofauna decomposers, by far exceed that of bacterial C. This challenges previous views on the dominance of bacteria in root C dynamics and suggests saprotrophic fungi to function as major agents channelling recent photoassimilates into the soil food web.