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Plant Physiology Forum

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Endangered Plants Persist Under Phosphorus Limitation ... Fens, bogs, marshes to grasslands. Recorded at each site: Species richness of vascular plants ... – PowerPoint PPT presentation

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Title: Plant Physiology Forum


1
Plant Physiology Forum
  • Co-ordinators Phillip Joy
  • Kathy Pickle

2
Endangered Plants Persist Under Phosphorus
Limitation
  • MJ Wassen, HO Venterink, ED Lapshina, F
    Tanneberger
  • Nature
  • 22 September 2005
  • 437 547-550

3
Species Diversity
  • Human alterations
  • Reductions in diversity
  • Affects ecosystem functioning
  • In order to counteract this we need to
  • Uncover the mechanisms responsible

4
Increased Productivity
Major Factor Influencing Species Extinction
5
Grimes Hump-backed Model
6
Nutrient Availability Mechanism
  • Low or moderate
  • Reduces competitive advantage of fast growing,
    tall species compared to smaller ones.
  • Temperate terrestrial ecosystems
  • Considered N-limited
  • N-enrichment is seen as a major cause of plant
    species loss

7
Authors Report New Findings
The type of nutrient limitation has never been
examined for a large number of sites.
P- rather than N- enrichment is more important in
loss of plant species from some ecosystems
8
What They Did
  • Investigated 274 sites with herbaceous vegetation
  • Fens, bogs, marshes to grasslands
  • Recorded at each site
  • Species richness of vascular plants
  • Number of endangered species
  • Above ground standing crop
  • Type of nutrient limitation

9
Netherlands/Belgium to eastern Poland to western
Siberia
Represents a declining gradient of atmospheric N
deposition 40-60 kg N ha-1yr-1 to 5-10 N ha-1yr-1
to lt5 N ha-1yr-1
10
What They Found
  • Conformed 2 well established relationships
  • The classical hump pattern with highest species
    richness at 200-660 gm-2
  • Sites with intermediate tissue NP ratios were
    the most species rich
  • Endangered plants species only occurred at low
    productivity sites

11
What Was Not Expected
  • In Poland and Siberia, endangered species are
    more frequent at P-limited sites than N-limited
    sites
  • Maximum numbers of endangered species are higher
    under P-limitation
  • Percentage of endangered species in the
    vegetation increases with P-limitation
  • Are better able to persist in P-limited sites
    than other nutrient-limited sites

12

13
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14
  • a, b - Frequency distributions of endangered
    species with preference for a certain type of
    nutrient limitation per region

15
Possible Mechanisms
  • 1) wider variation in adaptations to low P than
    to low N
  • 2) low productive N-limited systems have become
    P-limited
  • 3) human impact has impaired P-limited ecosystems
    to a greater extent

16
Authors Suggest Most Plausible
  • First 2 mechanisms discarded
  • Third is most likely
  • Leads to a larger loss of species
  • Various human activities for enhanced
    P-availability in wet and moist ecosystems
  • Increased groundwater extraction, eutrophication,
    sulphate pollution

17
Globally
  • Estimated that human intervention in the P cycle
    has increased the magnitude of P fluxes by 400
  • Much more than N, C, S

18
P - enrichment
  • May have caused productivity increase and species
    lost
  • Competitive exclusion
  • Shift from P- to N- limitation to the
    disadvantage of species adapted to low P

19
Can species richness ever be raised by nutrient
availability???
  • Addition of P may increase total species richness
    of P-limited wetlands BUT would promote common
    species at the expanse of rare ones
  • These findings support this statement
  • Absolute number proportion of endangered
    species greatest in P-limited sites

20
Conclusion
  • Conservation requires the preservation and
    restoration of p-limited ecosystems
  • Re-establishment often fails
  • Policies biased towards reducing N are unlikely
    to protect such species
  • Systems approach is needed

21
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