17/01/2006 1

J.C. Gégout, C. Piedallu, I. Seynave, J.C. HervéAgroParisTech - INRA - IFN

Large scale mapping of soil pH by plant presence/absence

bioindication

49th Annual Conference of the IAVS

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Plant distribution models are built with climatic variables and sometimes with proxies of soil resources (soil types, geology)

Nutritional variables are of major importance to plant growth and distribution

Measures of soil variables are expensive. Thus, it is difficult to gather enough measurements to make accurate maps

Is plant species bioindication useful to map nutritional soil resources ?

The need of nutritional direct variables for plant distribution modelling

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Data

French National Forest Inventory (IFN)Systematic sampling in forests88 004 floristic relevés without pH measures

EcoPlant3 835 floristic relevés with pH measures

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Response curve

Ecological variable

1

0

Pres/abs

Ecological variable

1

0

Response curve

Indicator value

IV

EcoPlant Indicator values

IV for 568 frequent plant species

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Predicted value : mean of species IVEllenberg (1974), ter Braak & Barendregt (1986)

5.7 3.0

6.2

8.3

6.5

Predicted pH : 6.0

0

0.1

0.2

0.3

pH4.0 4.9 5.9 6.9 7.9

Dryopteris filix-mas

Melica uniflora

Sambucus nigra

Bioindication with IV

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Mean of IV on each plot

88 004 IFN plots + pH_IV

88 004 IFN plots

with floristic inventory

pH prediction on IFN plots

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3.0 - 3.53.5 - 4.04.0 - 4.54.5 - 5.05.0 - 5.55.5 - 6.06.0 - 6.56.5 - 7.07.0 - 7.57.5 - 8.08.0 - 8.5lack of data

pH classes

0 500 kms

IDW Interpolation

pH mapping

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Map validation

261 validation plots on a grid of 16 x 16 kmsRepresentative of French Forest

R2 = 0.56, REQM = 0.82

3 4 5 6 7 8Mapped pH

3

4

5

6

7

8

Mea

sure

d pH

Measure of prediction errorsR2

REQM = (1/N * (X - X2)^

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Plots variables Sampling Plots nbStep

PrincipleA few expensive relevés with measures of variables to establish plant IVA lot of cheap relevés without measures to map variables

Plant species & measured variables

Stratified according to x

fewIndicator value

Plant species Systematic largeMapping

Variables mapping by bioindication

Systematic fewMap quality Plant species & measured variables

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The databases « IV », « mapping » and « quality » are constructed Acidity (pH)

Nitrogen avail.(C/N)

It is now easy to build up new maps of resources with other EcoPlant IV

IFN establish 7 000 - 10 000 new plots/year-> Increase of map resolution-> Possibility of monitoring by comparing maps of different periods

A generalisable method

Towards new distribution models integrating both climate and soil direct variables

17/01/2006 11

Thank you !

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Comparison of pH and C/N Maps

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PrésenceAbsence

Validation data (88 004 plots)

Map of the potential distribution of Acer campestre

Nutritional and climatic model

Climatic model

Climatic model, success: 54 %Nutritional and climatic model, success: 73 %

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Map of the Beech potential productivity