Interactions of plant productivity and phenology in Arctic ecosystems

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Interactions of plant productivity and phenology
in Arctic ecosystems

• Mathew Williams
• School of GeoSciences, University of Edinburgh

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Arctic tundra
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Modelling C exchange in tundra
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A simple model of phenology
Van Wijk et al. 2003
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Phenology and productivity

• What controls phenology in Arctic ecosystems?
• Initiation
• Termination
• What are the implications of phenology for
  production?

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Hypotheses

• 3 hypotheses for start of growing season
• Temperature sum
• Forcing units
• Soil thaw at 10 cm
• 3 hypotheses for determining the end of the
  growing season
• H1 photoperiod
• H2 finite period
• H3 frost end

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Parameter values for the phenology model
Parameterised from 95 96 data
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20 cm
Van Wijk et al 2003
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Van Wijk et al 2003
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Simulated start dates
Calibration year for FU and ST

Van Wijk et al 2003
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Start of growing season Betula nana
Data from Pop et al. (2000)
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Change to simulated start dates w/ 2oC
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Snow depth and soil temperature
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Soil thaw profiles
Black nominal Dark gray 1oC Light gray
2/4 oC
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Simulated GPP for end-of-season hypotheses
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GPP start date, end date
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Temperature, phenology and GPP
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(No Transcript)
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Conclusions

• Empirical models of budburst cannot always
  resolve snow-thaw interactions correctly
• Productivity is sensitive to end of season
  controls, especially in high latitudes
• The balance between periodic and aperiodic
  species is critical in the response of Arctic
  vegetation
• Interannual variation in LAI is another important
  factor that needs to be resolved

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Acknowledgements

• Mark Van Wijk
• Gus Shaver
• Jim Laundre

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Current work

• Phenology of miombo (tropical deciduous)
  woodlands in Mozambique

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Phenology

• the study of the timing of recurring biological
  phases, the causes of their timing with regard to
  biotic and abiotic forces, and the interrelation
  among phases of the same or different species.