PowerPointPrsentation

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Species indicator values as an important tool in
applied plant ecology Session Databases and
information systems 46th IAVS Symposium 8-14
June 2003 Naples (Napoli), Italy Martin Diekmann
Vegetation Ecology and Nature Conservation
Biology, IFOE
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Contents

• Biological indication Introduction
• Species responses and indicator values
• Applications of indicator values
• Indicator values and measurements
• Calibration of indicator values
• Conclusions

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Biological indication making use of the
specific reactions of organisms to their
environment
Examples Indicator values for climatic and soil
variables (Ellenberg et al. 1992)   Indicators of
habitat continuity (e.g. ancient forests) (Wulf
1997) Indicators of management (e.g. mowing
sensitivity) (Briemle Ellenberg 1994) Grimes
classification of species into habitat and
strategy types (Grime et al. 1988)
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Ellenberg values
Example Reaction soil or water pH (R) 1
Indicator of extreme acidity (Andromeda
polifolia) 2 Between 1 and 33 Acidity
indicator (Pteridium aquilinum) 4 Between 3 and
55 Indicator of moderately acid soils (Milium
effusum) 6 Between 5 and 77 Indicator of
weakly acid to weakly basic conditions (Hepatica
nobilis) 8 Between 7 and 99 Indicator of
calcareous or other high-pH soils (Primula
farinosa)
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Species responses and indicator values
Criticism Species have no distinct ecological
optima.
Species response, e.g. biomass production
Gauss curve
Ecological gradient (e.g. pH)
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• A Gaussian response is preferable, but it is
  sufficient that the
• response is unimodal or linearly
  increasing/decreasing (skewed).
• Most species response curves look that way, if
• The environmental variable in question is
  important.
• The total variation is large enough.
• The distribution of measured values along a
  gradient is more or less
• regular.

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Anemone nemorosa
Anemone ranunculoides
Melica nutans
Actaea spicata
Response curves of forest vascular plants in
Sweden (Diekmann, unpubl.)
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Applications of indicator values
Weighted site averages Site score (x1y1 x2y2
... xnyn) / (x1 x2 ... xn)     x1, x2,
..., xn frequencies of species 1 to n y1, y2,
..., yn indicator values of species 1 to n.
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• Weighted site averages serve to
• Obtain information about the environment of
  relevés, habitat patches,
• grid squares, etc., and to make
  environmental comparisons between sites.
• Interpret ordination diagrams, by correlating
  the axis scores of sites with
• the corresponding values of measurements.

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• ... calculate the size of the species pool of
  communities.

(Ewald, in press)
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• ... predict the occurrence of species.

(Dupré Diekmann 1998)
based on logistic regression
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• examine changes in environmental conditions
  and reconstruct historical
• site conditions on the basis of former
  species assemblages.

(Diekmann et al. 1999)
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• Weighted averages may be unreliable, if
• The plots studied are spatially highly
  heterogeneous.
• The environmental gradient is too short.
• The habitat is strongly affected by management
  
• (e.g. heavy grazing).
• There is a sudden environmental shift.
• The vegetation mainly responds to extremes and
  not to mean values.

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Indicator spectra
(Diekmann 2003)
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(Diekmann 2003)
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Indicator values and measurements
Criticism Indicator values are not
systematically derived from measurements, but
mainly inferred from field experience. They may
prevent us from conducting measurements!

• If weighted averages and measurements are
• - highly correlated,
• We conclude that the indicator values for the
  variable in question work well.
• - weakly correlated, there are two possible
  conclusions
• The indicator values for that variable are
  unreliable.
• 2) We have measured the wrong variable!

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Parameter Correlation   Soil reaction pH (H2O),
pH (KCl) (Persson 1980, Degorski 1982, or
pH (CaCl2) Lawesson Mark 2000,
Wamelink et al. 2002)
(Rodenkirchen 1982) (Ellenberg 1992,
Herzberger Karrer 1992,
Seidling Rohner 1993, Diekmann 1995,
Hill Carey 1997, Ertsen et al. 1998,
Schaffers Sýkora 2000, Diekmann,
unpubl.) Base saturation
(Degorski 1982, Seidling Rohner 1993,
Schaffers Sýkora 2000) Al/Ca ratio
(Seidling Rohner 1993) Ca2 saturation
(Schaffers Sýkora 2000) Ca2 amount
(Degorski 1982, Schaffers Sýkora 2000) Total
calcium (Schaffers Sýkora 2000)
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Correlation measured values weighted site scores
Swedish forests
(Diekmann 2003)
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Parameter Correlation Nitrogen N
PARAMETERS Total N (Vevle Aase 1980,
Schaffers Sýkora 2000) - (Hill Carey
1997, Ertsen et al. 1998) Total C/Organic
matter - (Hill Carey 1997)
(Diekmann, unpubl.) C/N ratio (Ellenberg
1992, Schaffers Sýkora 2000) -
(Diekmann, unpubl.) Mineral N (NO3- NH4)
(Schaffers Sýkora 2000) - (Lawesson,
unpubl.) Mineral NO3- (Schaffers Sýkora
2000) NO3- (Schaffers Sýkora
2000) Total mineralisation (Rodenkirchen
1982, Ellenberg 1992) -     (Schaffers
Sýkora 2000, Ammonification rate
(Diekmann, unpubl.) Nitrification rate
(Diekmann, unpubl.) Nitrification ratio
(Diekmann, unpubl.)
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Correlation measured values weighted site scores
Swedish forests
(Diekmann 2003)
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Parameter Correlation Nitrogen OTHER
NUTRIENTS Total P (Hill Carey 1997,
Ertsen et al. 1998) Available PO43-
(Ertsen et al. 1998, Schaffers Sýkora
2000) - (Lawesson, unpubl.) Total K
(Ertsen et al. 1998) Available K (Hill
Carey 1997, Schaffers Sýkora 2000) -
(Lawesson, unpubl.) Exchangeable Mg -
(Lawesson, unpubl.) VEGETATION-DERIVED
PARAMETERS Biomass/standing crop
(Boller-Elmer 1977, Briemle 1986) (Melman
et al. 1988, Hill Carey 1997,
Ertsen et al. 1998, Schaffers Sýkora 2000) N
accumulation of plants (Ertsen et al. 1998,
Schaffers Sýkora 2000) Foliar N
concentration (Thompson et al. 1993) Tissue
N concentration (Schaffers Sýkora 2000)
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Calibration of indicator values
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Criticism Species may shift in their responses,
especially across geographical gradients.
Three calibration approaches 1) Observation of
single species. 2) Indirect calibration on the
basis of large phytosociological data sets. 3)
Measurements of environmental parameters.
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(Hill et al. 2000)
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(Diekmann 2003 data from Hill et al. 1999 and
Schaffers Sýkora 2000)
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Conclusions

• Indicator values are subjective, but if they
  coincide with the ecological
• optima of species, they are very useful for
  many applications.
• Indicator values need to be verified by
  measurements and calibrated.
• Whenever possible, the use of indicator values
  should be accompanied
• by measurements.

46th IAVS Symposium 8-14 June 2003, Naples