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

46th IAVS Symposium 8-14 June 2003, Naples 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 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) Biological indication – making use of the specific reactions of organisms to their environment

46th IAVS Symposium 8-14 June 2003, Naples Example: Reaction – soil or water pH (R) 1 Indicator of extreme acidity (Andromeda polifolia) 2 Between 1 and 3 3 Acidity indicator (Pteridium aquilinum) 4 Between 3 and 5 5 Indicator of moderately acid soils (Milium effusum) 6 Between 5 and 7 7 Indicator of weakly acid to weakly basic conditions (Hepatica nobilis) 8 Between 7 and 9 9 Indicator of calcareous or other high-pH soils (Primula farinosa) Ellenberg values

46th IAVS Symposium 8-14 June 2003, Naples Species responses and indicator values Criticism: Species have no distinct ecological optima. Gauss curve Ecological gradient (e.g. pH) Species response, e.g. biomass production

46th IAVS Symposium 8-14 June 2003, Naples 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 Response curves of forest vascular plants in Sweden (Diekmann, unpubl.) Anemone nemorosa Anemone ranunculoides Melica nutans Actaea spicata

46th IAVS Symposium 8-14 June 2003, Naples Weighted site averages Site score = (x 1 y 1 + x 2 y x n y n ) / (x 1 + x x n ) x 1, x 2,..., x n frequencies of species 1 to n; y 1, y 2,..., y n indicator values of species 1 to n. Applications of indicator values

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. (Ewald, in press)

46th IAVS Symposium 8-14 June 2003, Naples... predict the occurrence of species. (Dupré & Diekmann 1998) [based on logistic regression]

46th IAVS Symposium 8-14 June 2003, Naples 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 (Diekmann 2003)

46th IAVS Symposium 8-14 June 2003, Naples (Diekmann 2003)

46th IAVS Symposium 8-14 June 2003, Naples Indicator values and 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! Criticism: Indicator values are not systematically derived from measurements, but mainly inferred from field experience. They may prevent us from conducting measurements!

46th IAVS Symposium 8-14 June 2003, Naples ParameterCorrelation Soil reaction pH (H 2 O), pH (KCl)+ (Persson 1980, Degorski 1982, or pH (CaCl 2 ) 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) Ca 2+ saturation++ (Schaffers & Sýkora 2000) Ca 2+ amount++ (Degorski 1982, Schaffers & Sýkora 2000) Total calcium++ (Schaffers & Sýkora 2000)

46th IAVS Symposium 8-14 June 2003, Naples Correlation measured values – weighted site scores (Diekmann 2003) Swedish forests

46th IAVS Symposium 8-14 June 2003, Naples ParameterCorrelation 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 (NO NH 4 + )+ (Schaffers & Sýkora 2000) - (Lawesson, unpubl.) Mineral NO (Schaffers & Sýkora 2000) % NO (Schaffers & Sýkora 2000) Total mineralisation+ (Rodenkirchen 1982, Ellenberg 1992) - (Schaffers & Sýkora 2000, Ammonification rate+ (Diekmann, unpubl.) Nitrification rate+ (Diekmann, unpubl.) Nitrification ratio++ (Diekmann, unpubl.)

46th IAVS Symposium 8-14 June 2003, Naples Correlation measured values – weighted site scores (Diekmann 2003) Swedish forests

46th IAVS Symposium 8-14 June 2003, Naples ParameterCorrelation Nitrogen OTHER NUTRIENTS Total P+ (Hill & Carey 1997, Ertsen et al. 1998) Available PO (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)

46th IAVS Symposium 8-14 June 2003, Naples Calibration of indicator values

46th IAVS Symposium 8-14 June 2003, Naples Three calibration approaches: 1) Observation of single species. 2) Indirect calibration on the basis of large phytosociological data sets. 3) Measurements of environmental parameters. Criticism: Species may shift in their responses, especially across geographical gradients.

46th IAVS Symposium 8-14 June 2003, Naples (Hill et al. 2000)

46th IAVS Symposium 8-14 June 2003, Naples (Diekmann 2003; data from Hill et al and Schaffers & Sýkora 2000)

46th IAVS Symposium 8-14 June 2003, Naples 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. Conclusions