期刊
SOIL BIOLOGY & BIOCHEMISTRY
卷 43, 期 1, 页码 20-30出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.soilbio.2010.09.005
关键词
C-13-Phospholipid fatty acid; Cropping systems; Root-C; Soil microenvironments
类别
资金
- Kearney Foundation of Soil Science
- University of California
- Western Sustainable Agriculture Research and Education Program
- National Institute of Environmental Health Sciences, NIH [5 P42 ES04699]
- NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES [P42ES004699] Funding Source: NIH RePORTER
This study coupled stable isotope probing with phospholipid fatty acid analysis (C-13-PLFA) to describe the role of microbial community composition in the short-term processing (i.e., C incorporation into microbial biomass and/or deposition or respiration of C) of root- versus residue-C and, ultimately, in long-term C sequestration in conventional (annual synthetic fertilizer applications), low-input (synthetic fertilizer and cover crop applied in alternating years), and organic (annual composted manure and cover crop additions) maize-tomato (Zea mays - Lycopersicum esculentum) cropping systems. During the maize growing season, we traced C-13-labeled hairy vetch (Vicia dasycatpa) roots and residues into PLFAs extracted from soil microaggregates (53-250 mu m) and silt-and-clay (<53 mu m) particles. Total PLFA biomass was greatest in the organic (41.4 nmol g(-1) soil) and similar between the conventional and low-input systems (31.0 and 30.1 nmol g-1 soil, respectively), with Gram-positive bacterial PLFA dominating the microbial communities in all systems. Although total PLFA-C derived from roots was over four times greater than from residues, relative distributions (mol%) of root- and residue-derived C into the microbial communities were not different among the three cropping systems. Additionally, neither the PLFA profiles nor the amount of root- and residue-C incorporation into the PLFAs of the microaggregates were consistently different when compared with the silt-and-clay particles. More fungal PLFA-C was measured, however, in microaggregates compared with silt-and-clay. The lack of differences between the mol% within the microbial communities of the cropping systems and between the PLFA-C in the microaggregates and the silt-and-clay may have been due to (i) insufficient differences in quality between roots and residues and/or (ii) the high N availability in these N-fertilized cropping systems that augmented the abilities of the microbial communities to process a wide range of substrate qualities. The main implications of this study are that (i) the greater short-term microbial processing of root- than residue-C can be a mechanistic explanation for the higher relative retention of root- over residue-C, but microbial community composition did not influence long-term C sequestration trends in the three cropping systems and (ii) in spite of the similarity between the microbial community profiles of the microaggregates and the silt-and-clay, more C was processed in the microaggregates by fungi, suggesting that the microaggregate is a relatively unique microenvironment for fungal activity. (C) 2010 Elsevier Ltd. All rights reserved.
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