Title: Plant Physiology Forum
1Plant Physiology Forum
- Co-ordinators Phillip Joy
-
- Kathy Pickle
2Endangered Plants Persist Under Phosphorus
Limitation
- MJ Wassen, HO Venterink, ED Lapshina, F
Tanneberger - Nature
- 22 September 2005
- 437 547-550
3Species Diversity
- Human alterations
- Reductions in diversity
- Affects ecosystem functioning
- In order to counteract this we need to
- Uncover the mechanisms responsible
-
4Increased Productivity
Major Factor Influencing Species Extinction
5Grimes Hump-backed Model
6Nutrient 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
7Authors 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
8What 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
9Netherlands/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
10What 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
11What 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(No Transcript)
14- a, b - Frequency distributions of endangered
species with preference for a certain type of
nutrient limitation per region
15Possible 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
16Authors 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
17Globally
- Estimated that human intervention in the P cycle
has increased the magnitude of P fluxes by 400 - Much more than N, C, S
18P - 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
19Can 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
20Conclusion
- 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
21Questions comments