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
Contents
• Biological indication: Introduction
• Species responses and indicator values
• Applications of indicator values
• Indicator values and measurements
• Calibration of indicator values
• Conclusions
46th IAVS Symposium 8-14 June 2003, Naples
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)
Grime’s classification of species into habitat and strategy types
(Grime et al. 1988)
46th IAVS Symposium 8-14 June 2003, Naples
Ellenberg values
Example: Reaction – soil or water pH (R)
1
2
3
4
5
6
7
8
9
Indicator of extreme acidity (Andromeda polifolia)
Between 1 and 3
Acidity indicator (Pteridium aquilinum)
Between 3 and 5
Indicator of moderately acid soils (Milium effusum)
Between 5 and 7
Indicator of weakly acid to weakly basic conditions (Hepatica nobilis)
Between 7 and 9
Indicator of calcareous or other high-pH soils (Primula farinosa)
46th IAVS Symposium 8-14 June 2003, Naples
Species responses and indicator values
Criticism: Species have no distinct ecological optima.
Species
response,
e.g. biomass
production
Ecological gradient (e.g. pH)
46th IAVS Symposium 8-14 June 2003, Naples
Gauss
curve
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.
46th IAVS Symposium 8-14 June 2003, Naples
Anemone nemorosa
Anemone ranunculoides
Melica nutans
Actaea spicata
Response curves of forest vascular plants in Sweden
(Diekmann, unpubl.)
46th IAVS Symposium 8-14 June 2003, Naples
Applications of indicator values
Weighted site averages
Site score = (x1y1 + x2y2 + ... + xnyn) / (x1 + x2 + ... + xn)
x1, x2, ..., xn
y1, y2, ..., yn
frequencies of species 1 to n;
indicator values of species 1 to n.
46th IAVS Symposium 8-14 June 2003, Naples
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.
46th IAVS Symposium 8-14 June 2003, Naples
• ... calculate the size of the species pool of communities.
Ruderal
Halophytic
Anthropogenic
heaths and
meadows
Talus and
alpine
meadow
Talus and
alpine
meadow
Ruderal
Deciduous
forest and
scrub
Tall herb
vegetation
Freshwater
and bogs
Deciduous
forest and
scrub
Tall herb
vegetation
Freshwater
and bogs
Halophytic
Anthropogenic
heaths and
meadows
Coniferous
forest
Coniferous
forest
0
100
200
300
400
# species R > 6
46th IAVS Symposium 8-14 June 2003, Naples
(Ewald,
in press)
0
20
40
60
% species R > 6
80
100
• ... predict the occurrence of species.
[based on logistic regression]
46th IAVS Symposium 8-14 June 2003, Naples
(Dupré &
Diekmann
1998)
• examine changes in environmental conditions and reconstruct historical
site conditions on the basis of former species assemblages.
(Diekmann et al. 1999)
46th IAVS Symposium 8-14 June 2003, Naples
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.
46th IAVS Symposium 8-14 June 2003, Naples
Indicator spectra
Elm-ash forest
No. of species
10
5
0
1
2
3
4
5
6
7
8
9
R indicator value
(Diekmann 2003)
46th IAVS Symposium 8-14 June 2003, Naples
9
No. of species
8
7
Basicolous
pine forest
6
5
4
3
2
1
0
1
2
3
4
5
6
7
8
9
R indicator value
(Diekmann 2003)
46th IAVS Symposium 8-14 June 2003, Naples
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:
1) The indicator values for that variable are unreliable.
2) We have measured the wrong variable!
46th IAVS Symposium 8-14 June 2003, Naples
Parameter
Correlation
Soil reaction
pH (H2O), pH (KCl)
or pH (CaCl2)
+
+
+
Base saturation
++
Al/Ca ratio
Ca2+ saturation
Ca2+ amount
Total calcium
++
++
++
++
(Persson 1980, Degorski 1982,
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.)
(Degorski 1982, Seidling & Rohner 1993,
Schaffers & Sýkora 2000)
(Seidling & Rohner 1993)
(Schaffers & Sýkora 2000)
(Degorski 1982, Schaffers & Sýkora 2000)
(Schaffers & Sýkora 2000)
46th IAVS Symposium 8-14 June 2003, Naples
Correlation measured values – weighted site scores
Swedish forests
(Diekmann 2003)
46th IAVS Symposium 8-14 June 2003, Naples
Parameter
Nitrogen
N PARAMETERS
Total N
Total C/Organic matter
C/N ratio
Mineral N (NO3- + NH4+)
Mineral NO3% NO3Total mineralisation
Ammonification rate
Nitrification rate
Nitrification ratio
Correlation
+
+
+
+
+
+
+
+
+
++
(Vevle & Aase 1980, Schaffers & Sýkora 2000)
(Hill & Carey 1997, Ertsen et al. 1998)
(Hill & Carey 1997)
(Diekmann, unpubl.)
(Ellenberg 1992, Schaffers & Sýkora 2000)
(Diekmann, unpubl.)
(Schaffers & Sýkora 2000)
(Lawesson, unpubl.)
(Schaffers & Sýkora 2000)
(Schaffers & Sýkora 2000)
(Rodenkirchen 1982, Ellenberg 1992)
(Schaffers & Sýkora 2000,
(Diekmann, unpubl.)
(Diekmann, unpubl.)
(Diekmann, unpubl.)
46th IAVS Symposium 8-14 June 2003, Naples
Correlation measured values – weighted site scores
Swedish forests
(Diekmann 2003)
46th IAVS Symposium 8-14 June 2003, Naples
Parameter
Nitrogen
OTHER NUTRIENTS
Total P
Available PO43Total K
Available K+
Exchangeable Mg
Correlation
+
+
+
+
-
(Hill & Carey 1997, Ertsen et al. 1998)
(Ertsen et al. 1998, Schaffers & Sýkora 2000)
(Lawesson, unpubl.)
(Ertsen et al. 1998)
(Hill & Carey 1997, Schaffers & Sýkora 2000)
(Lawesson, unpubl.)
(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)
46th IAVS Symposium 8-14 June 2003, Naples
Calibration of indicator values
46th IAVS Symposium 8-14 June 2003, Naples
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.
46th IAVS Symposium 8-14 June 2003, Naples
(Hill et al. 2000)
46th IAVS Symposium 8-14 June 2003, Naples
Calibrated R indicator
values in Great Britain
5
R-squ adj. = 0.850
4
Galium
pumilum
3
2
1
0
-1
-2
-3
-3
-2
-1
0
1
2
3
4
5
Calibrated R indicator
values in The Netherlands
(Diekmann 2003; data from Hill et al. 1999 and Schaffers & Sýkora 2000)
46th IAVS Symposium 8-14 June 2003, Naples
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