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Revisiting the hypothesis that fungal-to-bacterial dominance characterizes turnover of soil organic matter and nutrients

Rousk, Johannes LU and Frey, Serita D. (2015) In Ecological Monographs 85(3). p.457-472
Abstract
Resolving fungal and bacterial groups within the microbial decomposer community is thought to capture disparate life strategies for soil microbial decomposers, associating bacteria with an r-selected strategy for carbon (C) and nutrient use, and fungi with a K-selected strategy. Additionally, food-web model-based work has established a widely held belief that the bacterial decomposer pathway in soil supports high turnover rates of easily available substrates, while the slower fungal-dominated decomposition pathway supports the decomposition of more complex organic material, thus characterizing the biogeochemistry of the ecosystem. We used a field experiment, the Detritus Input and Removal Treatments, or DIRT, experiment (Harvard Forest... (More)
Resolving fungal and bacterial groups within the microbial decomposer community is thought to capture disparate life strategies for soil microbial decomposers, associating bacteria with an r-selected strategy for carbon (C) and nutrient use, and fungi with a K-selected strategy. Additionally, food-web model-based work has established a widely held belief that the bacterial decomposer pathway in soil supports high turnover rates of easily available substrates, while the slower fungal-dominated decomposition pathway supports the decomposition of more complex organic material, thus characterizing the biogeochemistry of the ecosystem. We used a field experiment, the Detritus Input and Removal Treatments, or DIRT, experiment (Harvard Forest Long-Term Ecological Research Site, USA) where litter and root inputs (control, no litter, double litter, or no tree roots) have been experimentally manipulated during 23 years, generating differences in soil C quality. We hypothesized (1) that delta C-13 enrichment would decrease with higher soil C quality and that a higher C quality would favor bacterial decomposers, (2) that the C mineralized in fungal-dominated treatments would be of lower quality and also depleted in delta C-13 relative to bacterial-dominated high-quality soil C treatments, and (3) that higher C mineralization along with higher gross N mineralization rates would occur in bacterial-dominated treatments compared with more fungal-dominated treatments. The DIRT treatments resulted in a gradient of soil C quality, as shown by up to 4.5-fold differences between the respiration per soil C between treatments. High-quality C benefited fungal dominance, in direct contrast with our hypothesis. Further, there was no difference between the delta(CO2)-C-13 produced by a fungal compared with a bacterial-dominated decomposer community. There were differences in C and N mineralization between DIRT treatments, but these were not related to the relative dominance of fungal and bacterial decomposers. Thus we find no support for the hypothesized differences between detrital food webs dominated by bacteria compared to those dominated by fungi. Rather, an association between high-quality soil C and fungi emerges from our results. Consequently there is a need to revise our basic understanding for microbial communities and the processes they regulate in soil. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
aboveground/belowground, biogeochemistry, carbon sequestration, decomposer ecology, food web, forest ecology, fungal and bacterial, dominance, Harvard Forest Long-Term Ecological Research (LTER), soil C, cycle
in
Ecological Monographs
volume
85
issue
3
pages
457 - 472
publisher
Ecological Society of America
external identifiers
  • wos:000358731100008
  • scopus:84938948326
ISSN
0012-9615
DOI
10.1890/14-1796.1
project
Interaction between fungi and bacteria in soil
Microbial carbon-use efficiency
Effect of environmental factors on fungal and bacterial growth in soil
MICCS - Molecular Interactions Controlling soil Carbon Sequestration
language
English
LU publication?
yes
id
b56441ed-c434-40c7-8731-75ff54d430ec (old id 7767738)
date added to LUP
2015-09-09 14:39:06
date last changed
2017-10-22 04:12:34
@article{b56441ed-c434-40c7-8731-75ff54d430ec,
  abstract     = {Resolving fungal and bacterial groups within the microbial decomposer community is thought to capture disparate life strategies for soil microbial decomposers, associating bacteria with an r-selected strategy for carbon (C) and nutrient use, and fungi with a K-selected strategy. Additionally, food-web model-based work has established a widely held belief that the bacterial decomposer pathway in soil supports high turnover rates of easily available substrates, while the slower fungal-dominated decomposition pathway supports the decomposition of more complex organic material, thus characterizing the biogeochemistry of the ecosystem. We used a field experiment, the Detritus Input and Removal Treatments, or DIRT, experiment (Harvard Forest Long-Term Ecological Research Site, USA) where litter and root inputs (control, no litter, double litter, or no tree roots) have been experimentally manipulated during 23 years, generating differences in soil C quality. We hypothesized (1) that delta C-13 enrichment would decrease with higher soil C quality and that a higher C quality would favor bacterial decomposers, (2) that the C mineralized in fungal-dominated treatments would be of lower quality and also depleted in delta C-13 relative to bacterial-dominated high-quality soil C treatments, and (3) that higher C mineralization along with higher gross N mineralization rates would occur in bacterial-dominated treatments compared with more fungal-dominated treatments. The DIRT treatments resulted in a gradient of soil C quality, as shown by up to 4.5-fold differences between the respiration per soil C between treatments. High-quality C benefited fungal dominance, in direct contrast with our hypothesis. Further, there was no difference between the delta(CO2)-C-13 produced by a fungal compared with a bacterial-dominated decomposer community. There were differences in C and N mineralization between DIRT treatments, but these were not related to the relative dominance of fungal and bacterial decomposers. Thus we find no support for the hypothesized differences between detrital food webs dominated by bacteria compared to those dominated by fungi. Rather, an association between high-quality soil C and fungi emerges from our results. Consequently there is a need to revise our basic understanding for microbial communities and the processes they regulate in soil.},
  author       = {Rousk, Johannes and Frey, Serita D.},
  issn         = {0012-9615},
  keyword      = {aboveground/belowground,biogeochemistry,carbon sequestration,decomposer ecology,food web,forest ecology,fungal and bacterial,dominance,Harvard Forest Long-Term Ecological Research (LTER),soil C,cycle},
  language     = {eng},
  number       = {3},
  pages        = {457--472},
  publisher    = {Ecological Society of America},
  series       = {Ecological Monographs},
  title        = {Revisiting the hypothesis that fungal-to-bacterial dominance characterizes turnover of soil organic matter and nutrients},
  url          = {http://dx.doi.org/10.1890/14-1796.1},
  volume       = {85},
  year         = {2015},
}