Eubacterial community structure and population size within the soil light fraction, rhizosphere, and heavy fraction of several agricultural systems

被引:53
作者
Blackwood, CB
Paul, EA
机构
[1] Michigan State Univ, Ctr Microbial Ecol, E Lansing, MI 48824 USA
[2] Michigan State Univ, Dept Crop & Soil Sci, E Lansing, MI 48824 USA
基金
美国国家科学基金会;
关键词
light fraction; rhizosphere; heavy fraction; shoot residue; soil microbes; microbial community analysis; terminal restriction fragment length polymorphism; agricultural management;
D O I
10.1016/S0038-0717(03)00188-3
中图分类号
S15 [土壤学];
学科分类号
0903 ; 090301 ;
摘要
The hypothesis that soil light fraction and heavy fraction harbor distinct eubacterial communities and have differing numbers and sizes of bacterial cells was tested in three agronomic cropping systems. This hypothesis would imply that these soil fractions are distinct microbial habitats. Shoot residue and rhizosphere soil were also included in the analysis. Terminal restriction fragment length polymorphism (T-RFLP) of 16S ribosomal DNA was used to assay eubacterial community structure. T-RFLP profiles were affected by both soil fraction and cropping system, accounting for 35-50% of the variance in the profiles. T-RFLP profiles separated samples into two distinct eubacterial habitats: soil heavy fraction, which includes the mineral particles and associated humified organic matter, and soil light fraction/shoot residue and rhizosphere, which includes particulate soil organic matter. Differences were not based on organic C content of fractions alone; T-RFLP profiles were also differentiated by cropping system and by rhizosphere versus light fraction/shoot residue. Heavy fraction communities had the least amount of random variability in T-RFLP profiles, resulting in the clearest cropping system effects, while rhizosphere and shoot residue communities were the most variable. Profiles from organically managed corn soil were more variable than for either conventionally managed corn or alfalfa. The log number of bacterial cells per gram fraction was affected by soil fraction but not cropping system, being highest in the light fraction. The percentage of cells >0.18 mum(3) was also greater in the light fraction than in other fractions. While bacterial cell density was generally correlated with C content of the soil fraction, heavy fraction did have a significantly greater number of cells per mug C than other soil fractions. The results show that habitat diversity in soil, related both to the amounts and types of organic matter, as well as other potential factors, are important in maintaining the high soil bacterial species diversity and evenness that is found in soil. (C) 2003 Elsevier Ltd. All rights reserved.
引用
收藏
页码:1245 / 1255
页数:11
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