2014-15 Call for Data
for Nitrogen and Sulphur
Critical Load Functions
(N & S CLFs)
Coordination Centre for Effects (CCE)
of the
ICP Modelling & Mapping (ICP M&M)
of the
Working Group on Effects (WGE)
J-P Hettelingh, M Posch, J Slootweg
CCE WS and ICP M&M TF, 7-10 April 2014, Rome
Reasons for a Call for Data:
1. Change in EMEP deposition grid
2. Requests for update by some NFCs
(e.g. due to improved national knowledge)
3. New (policy-driven) emphasis on biodiversity
CCE WS and ICP M&M TF, 7-10 April 2014, Rome
Ad 1:
EMEP N and S depositions now on a longitude-latitude grid:
Grid cells of size ½⁰ × ¼⁰, i.e. ~28 km (at 60⁰N) × ~28km
 the “28 km grid”
Size of grid cell as
function of latitude:
Ad 2:
Inter alia, opportunity to provide (better) CLs for
Natura2000 (and other protected) areas
CCE WS and ICP M&M TF, 7-10 April 2014, Rome
Reasons 1 and 2 sufficient for a Call for Data
(to maintain up-to-date CL-DB for policy support)
However, biodiversity aspects ever more relevant
Thus, biodiv-related CLs are encouraged
In the following: sketch of a possible way to derive
biodiv-related N & S critical load functions
CCE WS and ICP M&M TF, 7-10 April 2014, Rome
Level 0:
- CLnutN is determined from a critical [N] (or empirical CL)
related to (be avoided) biodiv-change
- Acidity CL function is derived for a (e.g.) critical pH
related to (be avoided) biodiv-change
CLs for acidity and nutrient N combined into a
CL function of N and S (dark grey area)
CCE WS and ICP M&M TF, 7-10 April 2014, Rome
New Level:
Derive N and S CL function from (your favourite)
biodiversity model …
e.g. PROPS, MultiMOVE, BERN, Veg, …, empirical, …
… e.g., along the following lines (using PROPS) …
CCE WS and ICP M&M TF, 7-10 April 2014, Rome
PROPS model summary:
Probability y for occurrence of a plant modelled as:
y
z  logit( y )  log
 a0 
1 y
n
n
n
 a  x   a
i
i 1
i
i, j
 xi  x j
i 1 j 1
with ai,j = aj,i for all i,j.
Number of variables xi is n = 4 (normalized/log-transformed):
soil solution pH and [N], precipitation, temperature.
Probability y obtained as:
y
1
1  exp(  z )
The 15 coefficients for many plant species are derived from relevés with
both biotic and abiotic observations and extrapolated …
CCE WS and ICP M&M TF, 7-10 April 2014, Rome
PROPS DataBase: Isolines of occurrence probability
for single species (in [N]-pH plane):
Temp and Precip fixed
.. However, single
plants rarely used …
CCE WS and ICP M&M TF, 7-10 April 2014, Rome
Example for an EVM vegetation unit
Scaled prob. to
get all species
... But we need
relationship with
Ndep and Sdep 
CCE WS and ICP M&M TF, 7-10 April 2014, Rome
The same as function of N and S deposition:
Computed from
physico-chemical
site characteristics
and steady-state
model (here: SMB)
Chose a “critical”
(“optimal”?)
Ndep-Sdep range 
CCE WS and ICP M&M TF, 7-10 April 2014, Rome
Apply limiting/critical/acceptable value of prob/poss/index, e.g.:
CCE WS and ICP M&M TF, 7-10 April 2014, Rome
N & S Critical Load Function:
… or … 
[can there by too little
S and/or N deposition?]
N & S Critical Load Function:
Entire grey area
(dark+light) defines
N & S CLF, i.e.
area of non-exceedance
… simplify … 
Simplify to polygon with a few (<10) nodes, e.g.:
Polygons need not be convex, but must be monotonous!
[ N1 ≤ N2 ≤ N3 ≤ … and S1 ≤ S2 ≤ S3 …]
CCE WS and ICP M&M TF, 7-10 April 2014, Rome
Not allowed:
No!
i.e. deposition increase may not lead to non-exceedance!
CCE WS and ICP M&M TF, 7-10 April 2014, Rome
Summary for Call4Data:
1. Cheap version:
Convert existing CLs to 0.10⁰×0.05⁰ Lon-Lat-grid and
CLaci+CLnut to 4-point N & S CLFunction
2. Better version:
Revisit/update existing CLs, consider biodiv criteria and
follow step 1
3. Ambitious version:
Use (steady-state or dynamic) biodiv model to derive N & S CLF
and follow step 1
CCE WS and ICP M&M TF, 7-10 April 2014, Rome
Thank You! 
…
Comments? 
Questions? 
CCE WS and ICP M&M TF, 7-10 April 2014, Rome
CCE WS and ICP M&M TF, 7-10 April 2014, Rome
Choice of probability/indicator:
Product of probs. (geometric mean):
Arithmetic mean:
CCE WS and ICP M&M TF, 7-10 April 2014, Rome