Biogeochemistry

, Volume 107, Issue 1–3, pp 379–391

Plant–microbe interactions and nitrogen dynamics during wetland establishment in a desert stream

Article

DOI: 10.1007/s10533-010-9559-6

Cite this article as:
Heffernan, J.B. & Fisher, S.G. Biogeochemistry (2012) 107: 379. doi:10.1007/s10533-010-9559-6

Abstract

In late-successional steady state ecosystems, plants and microbes compete for nutrients and nutrient retention efficiency is expected to decline when inputs exceed biotic demand. In carbon (C)-poor environments typical of early primary succession, nitrogen (N) uptake by C-limited microbes may be limited by inputs of detritus and exudates derived from contemporaneous plant production. If plants are N-limited in these environments, then this differential limitation may lead to positive relationships between N inputs and N retention efficiency. Further, the mechanisms of N removal may vary as a function of inputs if plant-derived C promotes denitrification. These hypotheses were tested using field surveys and greenhouse microcosms simulating the colonization of desert stream channel sediments by herbaceous vegetation. In field surveys of wetland (ciénega) and gravelbed habitat, plant biomass was positively correlated with nitrate (NO3) concentration. Manipulation of NO3 in flow-through microcosms produced positive relationships among NO3 supply, plant production, and tissue N content, and a negative relationship with root:shoot ratio. These results are consistent with N limitation of herbaceous vegetation in Sycamore Creek and suggest that N availability may influence transitions between and resilience of wetland and gravelbed stable states in desert streams. Increased biomass in high N treatments resulted in elevated rates of denitrification and shifts from co-limitation by C and NO3 to limitation by NO3 alone. Overall NO3 retention efficiency and the relative importance of denitrification increased with increasing N inputs. Thus the coupling of plant growth and microbial processes in low C environments alters the relationship between N inputs and exports due to increased N removal under high input regimes that exceed assimilative demand.

Keywords

Denitrification Uptake Nutrient retention Ciénega Paspalum distichum Regime shift 

Supplementary material

10533_2010_9559_MOESM1_ESM.pdf (231 kb)
Online Resource 1: Chemistry of simulated streamwater used in greenhouse experiment. (PDF 231 kb)
10533_2010_9559_MOESM2_ESM.pdf (293 kb)
Online Resource 2: Temporal patterns of net changes in NO3 and NH4+ in experimental microcosms. (PDF 294 kb)
10533_2010_9559_MOESM3_ESM.pdf (299 kb)
Online Resource 3: Temporal patterns of net changes in DON and DOC in experimental microcosms. (PDF 299 kb)
10533_2010_9559_MOESM4_ESM.pdf (258 kb)
Online Resource 4: Nitrogen budgets for experimental microcosms. (PDF 259 kb)

Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  1. 1.School of Life SciencesArizona State UniversityTempeUSA
  2. 2.Department of Biological SciencesFlorida International UniversityMiamiUSA
  3. 3.Southeast Environmental Research CenterFlorida International UniversityMiamiUSA

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