Linkages between extracellular enzyme activities and the carbon and nitrogen content of grassland soils

Published Date

May 2016, Vol.96:198–206, doi:10.1016/j.soilbio.2016.02.015

Title 

Linkages between extracellular enzyme activities and the carbon and nitrogen content of grassland soils

• Author 

• Valeria L. Cenini ^a
• Dario A. Fornara ^b,,
• Geoffrey McMullan ^c
• Nigel Ternan ^c
• Rachael Carolan^b
• Michael J. Crawley ^d
• Jean-Christophe Clément ^e
• Sandra Lavorel ^e

• aEnvironmental Sciences Research Institute, Ulster University, Coleraine BT52 1SA, UK
• bAgri-Food & Biosciences Institute, BT9 5PX Belfast, UK
• cSchool of Biomedical Sciences, Ulster University, Coleraine BT52 1SA, UK
• dDepartment of Life Sciences, Imperial College, Silwood Park, Ascot, Berkshire SL5 7PY, UK
• eLaboratoire d'Ecologie Alpine, UMR CNRS 5553, Université Grenoble Alpes BP53, 38041 Grenoble Cedex 9, France

Received 27 October 2015. Revised 16 February 2016. Accepted 19 February 2016. Available online 3 March 2016.

Highlights

• •
  Positive link between extracellular enzyme activities and soil C and N content.
• •
  Evidence of how grassland management may affect enzyme activity.
• •
  Enzyme activity may not be simply a reflection of SOM concentration.
• •
  Changes in enzyme activity could influence soil C and N in managed grasslands.

Abstract

Important biochemical reactions in soils are catalyzed by extracellular enzymes, which are synthesized by microbes and plant roots. Although enzyme activities can significantly affect the decomposition of soil organic matter and thus influence the storage and cycling of carbon (C) and nitrogen (N), it is not clear how enzyme activities relate to changes in the C and N content of different grassland soils. Here we address whether the activity of C-acquiring (β-1,4-glucosidase, BG) and N-acquiring (l-leucine aminopeptidase (LAP) and β-1,4-N-acetyl-glucosaminidase (NAG)) enzymes is linked to changes in the C and N content of a variety of human-managed grassland soils. We selected soils which have a well-documented management history going back at least 19 years in relation to changes in land use (grazing, mowing, ploughing), nutrient fertilization and lime (CaCO₃) applications. Overall we found a positive relationship between BG activity and soil C content as well as between LAP + NAG activity and soil N. These positive relationships occurred across grasslands with very different soil pH and management history but not in intensively managed grasslands where increases in soil bulk density (i.e. high soil compaction) negatively affected enzyme activity. We also found evidence that chronic nutrient fertilization contributed to increases in soil C content and this was associated with a significant increase in BG activity when compared to unfertilized soils. Our study suggests that while the activities of C- and N-acquiring soil enzymes are positively related to soil C and N content, these activities respond significantly to changes in management (i.e. soil compaction and nutrient fertilization). In particular, the link between BG activity and the C content of long-term fertilized soils deserves further investigation if we wish to improve our understanding of the C sequestration potential of human-managed grassland soils.

Keywords

• Land use
• Nutrient fertilization
• Lime
• pH
• β-1,4-Glucosidase
• Extracellular enzymes

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• ∗ 
  Corresponding author. Tel.: +44 (0)28 90255335.

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http://www.sciencedirect.com/science/article/pii/S0038071716000626