Microbial carbon dynamics in nitrogen amended Arctic tundra soil: measurement and model testing

We examined the responses of grazers (protozoa and nematodes) and their main food sources to low levels of nitrogen (N) fertilisation andapplied carbon (C) flux models to our data. Replicate plots of tundra soil adjacent to the Kongsfjorden (Svalbard 788N) were amended withammonium and nitrate at co...

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Bibliographic Details
Published in:Soil Biology and Biochemistry
Main Authors: Stapleton, LM, Crout, NMJ, Sawstrom, C, Marshall, WA, Poulton, PR, Tye, AM, Laybourn-Parry, J
Format: Article in Journal/Newspaper
Language:English
Published: Pergamon 2005
Subjects:
Biological Sciences
Microbiology
Microbial Ecology
Arctic
Svalbard
Kongsfjord*
Kongsfjorden
Tundra
Online Access:http://www.sciencedirect.com
https://doi.org/10.1016/j.soilbio.2005.03.016
http://ecite.utas.edu.au/49096
Description
Summary:We examined the responses of grazers (protozoa and nematodes) and their main food sources to low levels of nitrogen (N) fertilisation andapplied carbon (C) flux models to our data. Replicate plots of tundra soil adjacent to the Kongsfjorden (Svalbard 788N) were amended withammonium and nitrate at concentrations of 1 and 5 kg N haK1 to assess the impact of anthropogenic N deposition over three summers.Bacterial abundance as determined using the fluorochrome SYBR Green and epifluorescence microscopy ranged between 9.73!108 and102.49!108 cells/g dry wt of soil, with a significant response to N addition occurring only during the second sampling in 2001. Despite littlechange in bacterial biomass, bacterial production (measured by the incorporation of 3H thymidine into DNA) during the second sampling in2002, increased in NH4 enriched plots compared to control and NO3 amended plots, indicating that NH4 was the preferred source of inorganicN. The main bacterial predators were heterotrophic flagellates (HNAN) and naked amoebae, which showed no significant response to the Naddition. HNAN showed a correlation with bacterial abundance suggesting a dependence on bacteria as a food source. The inability of amicrobial C flux model to fit our data (RWSS/dataZ18.6, r2Z0.088) was at least partly due to insufficient bacterial production to meet the Cdemands of predator taxa, and high variability in the data over time. This is reflected in the performance statistics for model variants whereselect microbial taxa and data were removed. The optimal model in terms of predictive utility was a model with data from 2002 only, minusnaked amoebae (RWSS/dataZ2.45, r2Z0.806).

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