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Microbial community composition explains soil respiration responses to changing carbon inputs along an Andes-to-Amazon elevation gradient.

Whitaker J, Ostle N, Nottingham AT, Ccahuana A, Salinas N, Bardgett RD, Meir P, McNamara NP, Austin A - J. Ecol. (2014)

Bottom Line: We also found that RH increased with added C substrate quality and quantity and was positively related to microbial biomass and fungal abundance. 4.Synthesis.Although we do not make an experimental test of the effects of climate change on soil, these results challenge the assumption that different soil microbial communities will be 'functionally equivalent' as climate change progresses, and they emphasize the need for better ecological metrics of soil microbial communities to help predict C cycle responses to climate change in tropical biomes.

View Article: PubMed Central - PubMed

Affiliation: Centre for Ecology and Hydrology, Lancaster Environment Centre Library Avenue, Lancaster, LA1 4AP, UK.

ABSTRACT

1. The Andes are predicted to warm by 3-5 °C this century with the potential to alter the processes regulating carbon (C) cycling in these tropical forest soils. This rapid warming is expected to stimulate soil microbial respiration and change plant species distributions, thereby affecting the quantity and quality of C inputs to the soil and influencing the quantity of soil-derived CO2 released to the atmosphere. 2. We studied tropical lowland, premontane and montane forest soils taken from along a 3200-m elevation gradient located in south-east Andean Peru. We determined how soil microbial communities and abiotic soil properties differed with elevation. We then examined how these differences in microbial composition and soil abiotic properties affected soil C-cycling processes, by amending soils with C substrates varying in complexity and measuring soil heterotrophic respiration (RH). 3. Our results show that there were consistent patterns of change in soil biotic and abiotic properties with elevation. Microbial biomass and the abundance of fungi relative to bacteria increased significantly with elevation, and these differences in microbial community composition were strongly correlated with greater soil C content and C:N (nitrogen) ratios. We also found that RH increased with added C substrate quality and quantity and was positively related to microbial biomass and fungal abundance. 4. Statistical modelling revealed that RH responses to changing C inputs were best predicted by soil pH and microbial community composition, with the abundance of fungi relative to bacteria, and abundance of gram-positive relative to gram-negative bacteria explaining much of the model variance. 5. Synthesis. Our results show that the relative abundance of microbial functional groups is an important determinant of RH responses to changing C inputs along an extensive tropical elevation gradient in Andean Peru. Although we do not make an experimental test of the effects of climate change on soil, these results challenge the assumption that different soil microbial communities will be 'functionally equivalent' as climate change progresses, and they emphasize the need for better ecological metrics of soil microbial communities to help predict C cycle responses to climate change in tropical biomes.

No MeSH data available.


Soil respiration responses to nine C substrates over a range of concentrations (0.002–2.0 mg C g−1 soil f. wt.) in tropical forest soils from four elevations. Data represent mean ± SE (n = 3) of the additional CO2 flux (SIR-BR). SIR, substrate-induced respiration; BR, basal respiration.
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fig03: Soil respiration responses to nine C substrates over a range of concentrations (0.002–2.0 mg C g−1 soil f. wt.) in tropical forest soils from four elevations. Data represent mean ± SE (n = 3) of the additional CO2 flux (SIR-BR). SIR, substrate-induced respiration; BR, basal respiration.

Mentions: Responses of RH to C substrates grouped by their complexity were relatively consistent between soils, with simple compounds generating the greatest additional fluxes (i.e. fluxes after 2 mg C addition: glycine, xylose, cellobiose, glucose, N-acetyl glucosamine > vanillin > hemicellulose, cellulose, lignin; Fig.3). Additional CO2 fluxes increased with substrate concentration for most substrate/soil combinations. The exception was lignin, which generated minimal fluxes at all substrate concentrations and in all soils (Fig.3). Comparing the four soils, RH responses to the simple and intermediate C substrates at 2 mg addition were greatest in soils from higher elevations, with a similar trend observed in the 0.2 mg treatments for some simple and intermediate compounds (glycine, N-acetyl glucosamine and vanillin). For the complex substrates, there was no difference in additional CO2 flux with elevation, although the response to hemicellulose in the mid-elevation soils (1500 and 1750 m) was greater than in the low- and high-elevation soils (Fig.3). It is likely that the short incubation time used in these experiments limited substrate response to these more complex compounds as reported in other studies (Rinnan & Bååth 2009).


Microbial community composition explains soil respiration responses to changing carbon inputs along an Andes-to-Amazon elevation gradient.

Whitaker J, Ostle N, Nottingham AT, Ccahuana A, Salinas N, Bardgett RD, Meir P, McNamara NP, Austin A - J. Ecol. (2014)

Soil respiration responses to nine C substrates over a range of concentrations (0.002–2.0 mg C g−1 soil f. wt.) in tropical forest soils from four elevations. Data represent mean ± SE (n = 3) of the additional CO2 flux (SIR-BR). SIR, substrate-induced respiration; BR, basal respiration.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4263258&req=5

fig03: Soil respiration responses to nine C substrates over a range of concentrations (0.002–2.0 mg C g−1 soil f. wt.) in tropical forest soils from four elevations. Data represent mean ± SE (n = 3) of the additional CO2 flux (SIR-BR). SIR, substrate-induced respiration; BR, basal respiration.
Mentions: Responses of RH to C substrates grouped by their complexity were relatively consistent between soils, with simple compounds generating the greatest additional fluxes (i.e. fluxes after 2 mg C addition: glycine, xylose, cellobiose, glucose, N-acetyl glucosamine > vanillin > hemicellulose, cellulose, lignin; Fig.3). Additional CO2 fluxes increased with substrate concentration for most substrate/soil combinations. The exception was lignin, which generated minimal fluxes at all substrate concentrations and in all soils (Fig.3). Comparing the four soils, RH responses to the simple and intermediate C substrates at 2 mg addition were greatest in soils from higher elevations, with a similar trend observed in the 0.2 mg treatments for some simple and intermediate compounds (glycine, N-acetyl glucosamine and vanillin). For the complex substrates, there was no difference in additional CO2 flux with elevation, although the response to hemicellulose in the mid-elevation soils (1500 and 1750 m) was greater than in the low- and high-elevation soils (Fig.3). It is likely that the short incubation time used in these experiments limited substrate response to these more complex compounds as reported in other studies (Rinnan & Bååth 2009).

Bottom Line: We also found that RH increased with added C substrate quality and quantity and was positively related to microbial biomass and fungal abundance. 4.Synthesis.Although we do not make an experimental test of the effects of climate change on soil, these results challenge the assumption that different soil microbial communities will be 'functionally equivalent' as climate change progresses, and they emphasize the need for better ecological metrics of soil microbial communities to help predict C cycle responses to climate change in tropical biomes.

View Article: PubMed Central - PubMed

Affiliation: Centre for Ecology and Hydrology, Lancaster Environment Centre Library Avenue, Lancaster, LA1 4AP, UK.

ABSTRACT

1. The Andes are predicted to warm by 3-5 °C this century with the potential to alter the processes regulating carbon (C) cycling in these tropical forest soils. This rapid warming is expected to stimulate soil microbial respiration and change plant species distributions, thereby affecting the quantity and quality of C inputs to the soil and influencing the quantity of soil-derived CO2 released to the atmosphere. 2. We studied tropical lowland, premontane and montane forest soils taken from along a 3200-m elevation gradient located in south-east Andean Peru. We determined how soil microbial communities and abiotic soil properties differed with elevation. We then examined how these differences in microbial composition and soil abiotic properties affected soil C-cycling processes, by amending soils with C substrates varying in complexity and measuring soil heterotrophic respiration (RH). 3. Our results show that there were consistent patterns of change in soil biotic and abiotic properties with elevation. Microbial biomass and the abundance of fungi relative to bacteria increased significantly with elevation, and these differences in microbial community composition were strongly correlated with greater soil C content and C:N (nitrogen) ratios. We also found that RH increased with added C substrate quality and quantity and was positively related to microbial biomass and fungal abundance. 4. Statistical modelling revealed that RH responses to changing C inputs were best predicted by soil pH and microbial community composition, with the abundance of fungi relative to bacteria, and abundance of gram-positive relative to gram-negative bacteria explaining much of the model variance. 5. Synthesis. Our results show that the relative abundance of microbial functional groups is an important determinant of RH responses to changing C inputs along an extensive tropical elevation gradient in Andean Peru. Although we do not make an experimental test of the effects of climate change on soil, these results challenge the assumption that different soil microbial communities will be 'functionally equivalent' as climate change progresses, and they emphasize the need for better ecological metrics of soil microbial communities to help predict C cycle responses to climate change in tropical biomes.

No MeSH data available.