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- Kamble, Pramod, et al.
(författare)
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Bacterial growth and growth-limiting nutrients following chronic nitrogen additions to a hardwood forest soil
- 2013
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 59, s. 32-37
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Tidskriftsartikel (refereegranskat)abstract
- Increasing nitrogen(N) deposition due to anthropogenic activities has become a significant global change threat to N-poor terrestrial ecosystems. We compared bacterial growth and nutrients limiting bacterial growth in one of the longest running experiments on increasing N-deposition to a temperate forest, the Chronic Nitrogen Amendment Study at Harvard Forest, USA. Soil samples were collected in fall 2009 from the organic and mineral horizons of plots treated annually since 1988 with 0 (unfertilized), 50(low N) or 150 (high N) kg N ha(-1) as NH4NO3. In the organic horizon, bacterial growth (leucine incorporation) decreased by 5 times in the high N plots compared to the unfertilized treatment, while no decrease was observed in the mineral horizon. Bacterial growth in all soils was primarily limited by lack of carbon (C), although adding only C (as glucose) resulted in only a minor increase in bacterial growth in the unfertilized soil compared to adding C in combination with N. The bacterial growth induced by adding only C increased with higher level of N fertilization, up to 7-8 times the level without any C addition in the high N treatment, suggesting increased availability of N for the bacteria with increasing N addition. (C) 2013 Elsevier Ltd. All rights reserved.
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| 2. |
- Rousk, Johannes, et al.
(författare)
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Temperature adaptation of bacterial communities in experimentally warmed forest soils
- 2012
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 18:10, s. 3252-3258
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Tidskriftsartikel (refereegranskat)abstract
- A detailed understanding of the influence of temperature on soil microbial activity is critical to predict future atmospheric CO2 concentrations and feedbacks to anthropogenic warming. We investigated soils exposed to 3-4 years of continuous 5 degrees C-warming in a field experiment in a temperate forest. We found that an index for the temperature adaptation of the microbial community, T-min for bacterial growth, increased by 0.19 degrees C per 1 degrees C rise in temperature, showing a community shift towards one adapted to higher temperature with a higher temperature sensitivity (Q(10(5-15 degrees C)) increased by 0.08 units per 1 degrees C). Using continuously measured temperature data from the field experiment we modelled in situ bacterial growth. Assuming that warming did not affect resource availability, bacterial growth was modelled to become 60% higher in warmed compared to the control plots, with the effect of temperature adaptation of the community only having a small effect on overall bacterial growth (<5%). However, 3 years of warming decreased bacterial growth, most likely due to substrate depletion because of the initially higher growth in warmed plots. When this was factored in, the result was similar rates of modelled in situ bacterial growth in warmed and control plots after 3 years, despite the temperature difference. We conclude that although temperature adaptation for bacterial growth to higher temperatures was detectable, its influence on annual bacterial growth was minor, and overshadowed by the direct temperature effect on growth rates.
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