Oecologia

, Volume 170, Issue 3, pp 799–808

Nitrogen cycling and water pulses in semiarid grasslands: are microbial and plant processes temporally asynchronous?

  • Feike A. Dijkstra
  • David J. Augustine
  • Paul Brewer
  • Joseph C. von Fischer
Ecosystem ecology - Original research

DOI: 10.1007/s00442-012-2336-6

Cite this article as:
Dijkstra, F.A., Augustine, D.J., Brewer, P. et al. Oecologia (2012) 170: 799. doi:10.1007/s00442-012-2336-6

Abstract

Precipitation pulses in arid ecosystems can lead to temporal asynchrony in microbial and plant processing of nitrogen (N) during drying/wetting cycles causing increased N loss. In contrast, more consistent availability of soil moisture in mesic ecosystems can synchronize microbial and plant processes during the growing season, thus minimizing N loss. We tested whether microbial N cycling is asynchronous with plant N uptake in a semiarid grassland. Using 15N tracers, we compared rates of N cycling by microbes and N uptake by plants after water pulses of 1 and 2 cm to rates in control plots without a water pulse. Microbial N immobilization, gross N mineralization, and nitrification dramatically increased 1–3 days after the water pulses, with greatest responses after the 2-cm pulse. In contrast, plant N uptake increased more after the 1-cm than after the 2-cm pulse. Both microbial and plant responses reverted to control levels within 10 days, indicating that both microbial and plant responses were short lived. Thus, microbial and plant processes were temporally synchronous following a water pulse in this semiarid grassland, but the magnitude of the pulse substantially influenced whether plants or microbes were more effective in acquiring N. Furthermore, N loss increased after both small and large water pulses (as shown by a decrease in total 15N recovery), indicating that changes in precipitation event sizes with future climate change could exacerbate N losses from semiarid ecosystems.

Keywords

15N tracerNitrogen cyclingPlant-microbial interactionsTemporal effectsWater addition

Supplementary material

442_2012_2336_MOESM1_ESM.doc (48 kb)
Supplementary material 1 (DOC 48 kb)

Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  • Feike A. Dijkstra
    • 1
  • David J. Augustine
    • 2
  • Paul Brewer
    • 3
  • Joseph C. von Fischer
    • 3
  1. 1.Department of Environmental SciencesThe University of SydneyEveleighAustralia
  2. 2.USDA-ARS, Rangeland Resources Research UnitFort CollinsUSA
  3. 3.Department of Biology and Graduate Degree Program in EcologyColorado State UniversityFort CollinsUSA