Spatial and temporal patterns of C:N:P stoichiometry in the riparian zone of a semi arid river

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Spatial and temporal patterns of CNP
stoichiometry in the riparian zone of a semi
arid river
Teresa M. Tibbets
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Connectivity of river and riparian zone in arid
and semi-arid systems
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Nutrients Carbon Nitrogen Phosphorus Organic
matter from riparian vegetation provides direct
and indirect support of river-riparian
ecosystem. Turnover and cycling of nutrients is
influenced by quality of organic matter. Plants
are plastic in uptake and storage of
nutrients.
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Middle Rio Grande
Today

• Regulation of timing and flow of river by dams
  and levees.
• Riparian area disconnected from river.
• Exotic species saltcedar Russian olive.

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Invasion of exotic vegetation e.g.
Tamarix (Saltcedar)
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Invasion of exotic vegetation y Elaeagnus
(Russian Olive)
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Objectives

• Research Focus
• Describe spatial and temporal patterns of CNP
  of the main autotroph (leaf) and detrital
  (litter) inputs along the middle Rio Grande.
• Identify factors influencing leaf litter
  quality.

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What is the temporal and spatial variation in
cottonwood CN, CP NP?
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Methods

• CNP Cottonwood
• (Populus deltoides)
• Leaves late May and mid-August
• Litter after senescence
• Sampled 2001, 2002 2003
• CNP of salt-cedar (Tamarix)
• and russian olive (Eleagnus)

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Results
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Coefficient of Variation of leaf and litter CNP
N Non-flood F Flood
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Exotic Species Nutrient inputs
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Is the CNP of riparian leaves and litter
variable?
Yes.
Significant variation in Leaf CNP between study
sites. Significant temporal changes in N and P
over season. Flood sites more variable-especially
for P. Anthropogenic effects Low leaf and
litter CN downstream wastewater treatment
plant. Exotic speices high in N.
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Conclusions

• Flooding likely influences nutrient content of
  riparian trees-mechanisms complex.
• Anthropogenic inputs are reaching riparian zone
  through ground water.
• N-rich exotic species likely enriching riparian
  zone.
• Riparian nutrient dynamics could be affected by
  changes in hydrologic regime and nutrient inputs.

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FIRE
DROUGHT
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Acknowledgements
UNM Hydrogeoecology Group Summer Sling Shot
Crew Middle Rio Grande Conservancy
District Bosque del Apache National Wildlife
Refuge City of Albuquerque Open Space
Division New Mexico State Land Office Rio Grande
Nature Center NASA-SHARP
Funding was provided by NSF Conservation and
Restoration Award (DEB-9903973) NSF IGERT
Freshwater Sciences Interdisciplinary Doctoral
Program (DGE-9972810) Sigma Xi Grants-in-Aid of
Research UNM Department of Biology Grove
Scholarship Graduate Research Allocation
Committee UNM GPSA Student Research Allocation
Committee UNM OGS Research, Project, Travel
Grant
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What is the CN, CP, NP for riparian
invertebrates?
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a
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a
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Results Research Focus I
Does the CN of cottonwood leaves vary?
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Results Research Focus I
Does the CP of cottonwood leaves vary?
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Results Research Focus I
Does the NP of cottonwood leaves vary?
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Results Research Focus I
2002
?
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Ecological stoichiometry offers a framework to
integrate energy, material, and trophic linkages
within stream-riparian ecosystems by focusing on
the imbalance between multiple elemental
requirements of organisms and their food sources
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The Rio Grande riparian ecosystem in
stress......