Dataset Information

Tundra microbial community taxa and traits predict decomposition parameters of stable, old soil organic carbon.

ABSTRACT: The susceptibility of soil organic carbon (SOC) in tundra to microbial decomposition under warmer climate scenarios potentially threatens a massive positive feedback to climate change, but the underlying mechanisms of stable SOC decomposition remain elusive. Herein, Alaskan tundra soils from three depths (a fibric O horizon with litter and course roots, an O horizon with decomposing litter and roots, and a mineral-organic mix, laying just above the permafrost) were incubated. Resulting respiration data were assimilated into a 3-pool model to derive decomposition kinetic parameters for fast, slow, and passive SOC pools. Bacterial, archaeal, and fungal taxa and microbial functional genes were profiled throughout the 3-year incubation. Correlation analyses and a Random Forest approach revealed associations between model parameters and microbial community profiles, taxa, and traits. There were more associations between the microbial community data and the SOC decomposition parameters of slow and passive SOC pools than those of the fast SOC pool. Also, microbial community profiles were better predictors of model parameters in deeper soils, which had higher mineral contents and relatively greater quantities of old SOC than in surface soils. Overall, our analyses revealed the functional potential of microbial communities to decompose tundra SOC through a suite of specialized genes and taxa. These results portray divergent strategies by which microbial communities access SOC pools across varying depths, lending mechanistic insights into the vulnerability of what is considered stable SOC in tundra regions.

SUBMITTER: Hale L

PROVIDER: S-EPMC6863828 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Tundra microbial community taxa and traits predict decomposition parameters of stable, old soil organic carbon.

Hale Lauren L Feng Wenting W Yin Huaqun H Guo Xue X Zhou Xishu X Bracho Rosvel R Pegoraro Elaine E Penton C Ryan CR Wu Liyou L Cole James J Konstantinidis Konstantinos T KT Luo Yiqi Y Tiedje James M JM Schuur Edward A G EAG Zhou Jizhong J

The ISME journal 20190805 12

The susceptibility of soil organic carbon (SOC) in tundra to microbial decomposition under warmer climate scenarios potentially threatens a massive positive feedback to climate change, but the underlying mechanisms of stable SOC decomposition remain elusive. Herein, Alaskan tundra soils from three depths (a fibric O horizon with litter and course roots, an O horizon with decomposing litter and roots, and a mineral-organic mix, laying just above the permafrost) were incubated. Resulting respirati ...[more]

PMID: 31384013

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Project description:Soil organic carbon (SOC) is a major component in the global carbon cycle. Yet how input of plant litter may influence the loss of SOC through a phenomenon called priming effect remains highly uncertain. Most published results about the priming effect came from short-term investigations for a few weeks or at the most for a few months in duration. The priming effect has not been studied at the annual time scale. In this study for 815 days, we investigated the priming effect of added maize leaves on SOC decomposition of two soil types and two treatments (bare fallow for 23 years, and adjacent old-field, represent stable and relatively labile SOC, respectively) of SOC stabilities within each soil type, using a natural 13C-isotope method. Results showed that the variation of the priming effect through time had three distinctive phases for all soils: (1) a strong negative priming phase during the first period (?0-90 days); (2) a pulse of positive priming phase in the middle (?70-160 and 140-350 days for soils from Hailun and Shenyang stations, respectively); and (3) a relatively stabilized phase of priming during the last stage of the incubation (>160 days and >350 days for soils from Hailun and Shenyang stations, respectively). Because of major differences in soil properties, the two soil types produced different cumulative priming effects at the end of the experiment, a positive priming effect of 3-7% for the Mollisol and a negative priming effect of 4-8% for the Alfisol. Although soil types and measurement times modulated most of the variability of the priming effect, relative SOC stabilities also influenced the priming effect for a particular soil type and at a particular dynamic phase. The stable SOC from the bare fallow treatment tended to produce a narrower variability during the first phase of negative priming and also during the second phase of positive priming. Averaged over the entire experiment, the stable SOC (i.e., the bare fallow) was at least as responsive to priming as the relatively labile SOC (i.e., the old-field) if not more responsive. The annual time scale of our experiment allowed us to demonstrate the three distinctive phases of the priming effect. Our results highlight the importance of studying the priming effect by investigating the temporal dynamics over longer time scales.

Project description:Decomposition of vertebrate remains is a dynamic process that creates localized soil enrichment zones. A growing body of literature has documented effects of vertebrate decomposition on soil pH, electrical conductivity, oxygen levels, nitrogen and carbon speciation, microbial biomass, and microbial successional patterns. However, relatively few studies have examined the microfaunal members of the soil food web that function as secondary consumers, specifically nematodes. Nematodes are often used as indicators of enrichment in other systems, and initial observations from vertebrate decomposition zones have indicated there is an effect on nematode communities. Our goal was to catalog decomposition-induced nematode succession and changes to alpha, beta, and functional diversity, and identify potential indicator taxa associated with decomposition progression. Six adult beaver (Castor canadensis) carcasses were allowed to decompose in a forest ecosystem for one year. During this period soil temperature, moisture, and electrical conductivity were monitored. Soils samples were taken at two depths in order to assess nematode community dynamics: 30-cm cores and 1-cm interface samples. Nematode abundance, alpha, beta, and functional diversity all responded to soil enrichment at the onset of active decay, and impacts persisted through skeletonization. After one year, nematode abundances and alpha diversity had recovered to original levels, however both community membership and functional diversity remained significantly altered. We identified seven indicator taxa that marked major transitions in decomposition progression. Enrichment of Rhabditidae (B1) and Diplogasteridae (B1) coupled with depletion in Filenchus (F2) characterized active and advanced decay prior to skeletonization in both cores and interface soils. Enrichment of Acrobeloides (B2), Aphelenchoides (F2), Tylencholaimidae (F4) and Seinura (P2) occurred during a narrow period in mid-skeletonization (day 153). Our study has revealed soil nematode successional patterns during vertebrate decomposition and has identified organisms that may function as indicator taxa for certain periods during decomposition.

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Dataset Information

Tundra microbial community taxa and traits predict decomposition parameters of stable, old soil organic carbon.

Publications

Tundra microbial community taxa and traits predict decomposition parameters of stable, old soil organic carbon.

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