Comparative study of nitrogenase activity in different types of biological soil crusts in the Gurbantunggut Desert, Northwestern China

  • Wu N
  • Zhang Y
  • Downing A
  • 1

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Abstract

Biological soil crusts cover large areas of the Gurbantunggut Desert in northwestern China where they make a significant contribution to soil stability and fertility. The aim of this study was to quantify the potential nitrogen-fixing activity (NA) of different types of biological soil crusts in the Gurbantunggut Desert. The results suggest that NA (nmol C
2H
4 m
-2 h
-1) for each type of crusts was highly variable. Seasonal variation was also important, with all three types of crusts responding in a similar way to changes in environmental conditions. From March to May, NA was relatively low for all crust types. During this season, NA was 2.26 × 10
3 for cyanobacterial crust followed by lichen crust (6.54 × 10
2) and moss crust (6.38 × 10
2). From June to October, all crust types reached their highest level of NA, especially lichen crust and moss crust (p < 0.01). The NA of cyanobacterial crust (9.81 × 10
3) was higher than that of lichen crust (9.06 × 10
3) and moss crust (2.03 × 10
3). From November to February, when temperatures were consistently low ( 2) and moss crust (5.43 × 10
2) (p < 0.01). Our results indicate that species composition is critical when estimating N inputs in desert ecosystems. In addition, all three types of crusts generally responded in a similar way to environmental conditions. The presence of N fixation activity in all crusts may contribute to the maintenance of fertility in sparsely vegetated areas and provide surrounding vascular plant with fixed nitrogen. © 2009 Elsevier Ltd. All rights reserved.

Author-supplied keywords

  • Acetylene reduction
  • Ecological function
  • Lichen-dominated crust
  • Nitrogen fixation

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Authors

  • N. Wu

  • Y.M. M. Zhang

  • A. Downing

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