Responses of Ammonia-Oxidising Bacterial Communities to Nitrogen, Lime, and Plant Species in Upland Grassland Soil

Deirdre C Rooney,Nicholas J W Clipson,Nabla M Kennedy,Deirdre B Gleeson

doi:10.1155/2010/319721

Abstract

Agricultural improvement of seminatural grasslands has been shown to result in changes to plant and microbial diversity, with consequences for ecosystem functioning. A microcosm approach was used to elucidate the effects of two key components of agricultural improvement (nitrogen addition and liming) on ammonia-oxidising bacterial (AOB) communities in an upland grassland soil. Plant species characteristic of unimproved and improved pastures (A. capillarisandL. perenne) were planted in microcosms, and lime, nitrogen (NH4NO3), or lime plus nitrogen added. The AOB community was profiled using terminal restriction fragment length polymorphism (TRFLP) of theamoAgene. AOB community structure was largely altered byNH4NO3addition, rather than liming, although interactions between nitrogen addition and plant species were also evident. Results indicate that nitrogen addition drives shifts in the structure of key microbial communities in upland grassland soils, and that plant species may play a significant role in determining AOB community structure.

Highlights

The impact of anthropogenic activities on soil biodiversity is central to our understanding of the links between soil functional diversity, species diversity, and overall ecosystem functioning
The main finding of this study was that nitrogen addition to upland grassland soil significantly influenced ammonia-oxidising bacterial (AOB) community structure, and that the response was dependent on which plant species was present
This study has shown that nitrogen status and plant species type, plus their interactions, play major roles in the determination of AOB community structure in upland acidic pastures

Summary

Introduction

The impact of anthropogenic activities on soil biodiversity is central to our understanding of the links between soil functional diversity, species diversity, and overall ecosystem functioning. Agricultural improvement of natural upland pastures is widespread in NW Europe, with increased fertilisation, liming, and grazing producing a shift in the floristic composition of acidic upland grasslands [1, 2]. Such intensification practices result in a gradual shift from a plant species-rich Agrostis capillaris pasture to a species-poor grassland dominated by Lolium perenne [3], with concurrent changes in soil physicochemical properties [1, 4, 5], most notably soil nutrient status. Exploitation of the amoA gene as a molecular marker and the application of community fingerprinting techniques have revealed considerable AOB diversity [8]

Methods

Results

Discussion

Conclusion