First Draft Without Figures and Some Tables

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1


First Draft Without Figures

and Some
Tables

Soil
Geography

and Pedodiversity of the European Biogeographical Regions


Ibáñez, J.J.
(1)
,

Zinck, J.A.
(2)
, Dazzi, C
(3)
.




(1)
Centro de Investigaciones sobre Desertificación: CIDE (CSIC, Universitat de
Valenc
ia, Generalitat Valenciana), Cami de la Marjal
, s/
n; Apartado Oficial,
Spain
. e.mail: choloibanes@.hotmail.com

(2) Faculty of Geo
-
Information Science and Earth Observation

(ITC),

University
of Twente,

P.O. Box

6, 7500 AA
,

Enschede, The Netherlands. e
-
mail:

zincka@itc.nl

(3) Dipartimento dei Sistemi AgroAmbientali; Facoltà di Agraria; Università di

Palermo, Viale delle Scienze, 90128 Palermo (I), Italy

email address:
carmelo.dazzi@unipa.it



Abstract


For

decades
,

soil ge
ography has been
mainly
a qualitative and descriptive

discipline.
There are now

technologies and mathematical tools

available

that
allow formalizing soil geography in more quantitative

terms
. In this paper
,

soil
distribution

a
nd pedodiversity of

Europe

are

analyzed

using GIS tools and
pedodiversity algorithms. Soil data were taken from

t
he
European Soil Database
(V2.0)

and
computed within the spatial framework of
the
Biogeographical

Regions of Europe

(BGRE)

as defined by

the

EEA

on the basis of climate and
vegetation
.
T
he results obtained show the soil assemblages
, including

dominant
soils and endemic
and
non
-
endemic
soil minorities,

and t
heir respective soil
diversity

for each
BGRE
.
Most BGRE

h
ave dominant soils that are in agreement
with previous descripti
ve studies using the concept of soil zonality at small
scales.
Although the definition of the BGRE

lack
s

relevant informatio
n

on

geology, relief and pale
o
geographic evolution, soil assemblages of most

biogeographical region are idiosyncratic and characteri
ze quite well European
soilscapes.
Therefore the old concept of zonal soils seems valid at coarse scales.
Northern
BGRE

(
i.e.
Arctic

and Boreal)
have low

pedotaxa

diversity

in contrast
to the
other BGRE
.
T
he Black Sea region
, the

small
est

one of all
,

has n
o

idiosyncratic soil, suggesting that

it

coul
d be considered as an important

biodiversity
hotspot
of biodiversity
rather

than a genuine biogeographical
2


region. The
use of these results
is relevant
as a base line to a full inventory of
pedodiversity, as an
important part of the European natural heritage
.



Keywords
:

Europe, Soil Geography, Pedodiversity, Biogeographical Regions
,
Soil Minorities, Soil endemisms



3


1.
Introduction


The European soil geography has been studied
for
decades from differe
nt points
of view, at different scales
,

and making use of different

national classification

schemes
(Jones et al.
,

2005)
as well as
the
FAO Keys
(1974, 1990)
and
,

more
recently
,

the
WRB

framework

(
FAO,
1998, 2006
-
2007)
. However
,

a
comprehensive
,
quantitati
ve analysis

of

the

spatial distribution

of the

soil types
(pedotaxa) across the continent

is still lacking
,

whereas

a digitized

georeferenced
soil
database at E
uropean level
permit
s

now to undertake

such

an

analysis.
A
first initiative
was carried

out for
the European Communities
(
CEC
,
1985)
,

resulting in the publication of
a soil map
in
paper format for most of

the

western
countries.
This
map was
subsequently digitized,
improved
,

and expanded
several times until the latest 2004 version on CD
-
ROM
(
E
C
,
2004
)
. Likewise
,

a
Soil Atlas of Europe (ESBN
-
EC, 2005
)

together with
a
monograph

on
“Soils of
European Union” (Tóth et al.
,

2008) has been published recently.
This is mainly
descriptive information. Several

papers

provide a more elaborate vision

on the
spatial

distribution of
the
soil
types across

Europe, showing fractal structures at
least for the most abundant pedotaxa (Ibáñez et al.
,

2009).

Pedodiversity analysis
has been considered to be an interesting mathematical tool in soil geography (e.g.
Ibáñez and Ef
fland
,

2011
). It has been used at

worldwide level (Ibáñez et al.
,

1998) and in

the

United States (Guo et al.
,

2003), but not yet applied to the
European continent.

The objective of this paper is to show the soil assemblages of
most European countries and a
nalyze their pedodiversities in a quantitative way.



2. Material and Methods



2.1
Material


To
analyse soil geography and pedodiversity of Europe
,

the continent

c
a
n be
fragmented

using different geometric supports

such as
administrative
bounda
ries, drainage basins
,

or biogeograp
hical
-
ecological units
. Both

the

country borders and

the

drainage basins

often

cross several environmental units
,

making it difficult to compare the spatial distribution of
pedotaxa and soil
forming factors. In view of

t
he former,

this paper

use
s

the official version of the
European map of biogeographical regions

(BGRE)

at the scale of 1
:
1M

(EEA,
2002
)
, excluding associated areas that
do not belong to

the physical geography of
Europe such as the Anatolian Biogeographical
Region
,
also excluded in
its

last
version
(EEA,

2008).

The definition and delineation of

the

BGRE
are mainly
based on climate and vegetation
, but geologic and geomorphic criteria, together
with land use histories
, w
e
re

also

taken into account for different
iation.

Therefore, the BGRE

can be used as spatial frameworks for th
e analysis of

soil
geography

and pedodiversity

across the European continent.


4




2.2
Procedures using GIS Software


The
European Soil Database (V2.0) (EC
,

2004
)
and the related digital soi
l map at
the scale of
1:
1
M were

used

to show the distribution of the soil types
.

The
European Soil Database collects the information provided by national soil data
centers, which work with different national classification systems and at different
surveyin
g scales. Thus, because of the coarse scale of the maps and cartographic
generalizations, the pedotaxa inventory might be incomplete for some of the
countries.

The s
oil classification

was according to

the World Reference Base for
Soil Resources (WRB)
,

19
98

version

(FAO, 199
8
)
, with 32 units at the first level
and 172 units, including five miscellaneous ones, at the second level.
In the
present

study
,

these units

are
termed
pedotaxa of the first level and

second level
of the WRB
, respectively
.

The soil map
s
were

drawn in the Lambert Azimuthal
Equal
-
Area projection with longitude of origin 20º E and latitude of origin 50º N.
Equal
-
area projections are best suited for area distribution maps.


The
GIS software
s

Geomedia Professional (V6.0) and Geomedia GRID (
V6.0)
were used

for data handling
.
The distribution maps of the
pedotaxa at the first
and second level
were
obtained

following the steps described by Ibáñez et al
.

(2009)
. Thi
s was achieved by disaggregating

the

soil map associations (EC, 2004)
into their
constitutive

pedotaxa
, obtaining 32

and 1
47

vector maps with soil
polygons respectively for the first and second

WRB

level
.

These maps were
subsequently
rasterize
d

with a cell resolution of
25 km
2

(
i.e.
the smalles
t

soil
polygon delineation).

The
technical

procedure

of vector
-
raster conversion is
descr
ibed

by Benito and Suarez (2005).


The
total
extent covered by each pedotax
um at
the first and second level
in the
European Soil Database was split

and

areal

prop
o
rtions recalculated per

biogeographical reg
ions

of occurrence (
i.e. Alpine, Arctic, Atlantic, Black

S
ea,
Boreal, Continental,
Macaronesian,
Mediterranean, Pannonian
,

and

Steppic
).

Additional information on the Macaronesian
b
iogeographical region

at the first
level of the
WRB, which
was

not recorde
d

in the European Soil Database
,

was

also included

(Benito and Suarez, 2005)
.


2.3
Estimation of

Pedodiversity


A pedodiversity analysis was carried out for the soil assemblages of each
BGRE

using the following indices: richness, Shannon diversity inde
x
,

a
nd Shannon
evenness

(Shannon and Weaver, 1949)
.

A friendly discussion of pros and cons of
these indices can be found in Magurran (1988).

Richness (
S
)
refers to

the

number
of pedotaxa

occurring

in a given

BGRE.

The

Shannon Index (
H’
) is the

most
5


commonly

us
ed diversity index in ecology and pedology
(Shannon and Weaver,
1949;

Ibáñez et a
l
.
,

199
0, 1995
):


i
i
n
i
i
p
p
H
ln
'
1






(1)


where

p
i

is estimated by means of
ni/N

where
n
i

is the area covered by the

i
-
th
pedotaxum
, and
N

the total area of each
BGRE
.
A
ny logarithmic base can be
adopted

to calculate Shannon's Index
. The natural logarithm
was

used in this
article.


Thus, the value of

H
' is the sum of the

areal

proportions cover
ed

by a pedotaxum
in a

given

BGRE multiplied by the negative logarithm of th
e

total

proportion
occupied in the same BGRE
. It ranges from 0 (ln

1)

in

the case a single
pedotaxum covers the

total

area of a

BGRE
(r
ichness = 1)
, to ln

S

in the case

all
pedotaxa cover similar extents

in
a BGRE
. This inde
x is a measure of information
on

a group of objects (species, soil types, etc.) which have different probabilities
of being represented.
M
aximum
information occurs
when the probabilities
(proportional abundance) of all pedotaxa
are

the same
. It is then equal to l
n
S
.
Information is 0 if
there is only one possibility
, meaning that one

pedotaxum
cover
s

the 100% of a hypotheti
cal BGRE
, i.e. diversity is 0.


The relationship between the observed value of
H'
and its maximum value
H
max

(for a given richness
) occurs when the area covered by

all

pedotaxa is
equiprobable in a given BGRE. This

is used as a measure of evenness or
equitability (
E
):


E = H´/H
max

= H´/
ln

S

(2)


where
S

is the richness or number of
classes
categories

and
E

takes values in the
interval (0,1).
E

refers to
the relative ab
undance (
i.e.
evenness or equitability) of
pedotaxa and is the most commo
n index used as a measure of

structural
heterogeneity.


2.4
Endemic
S
oils and Soil Minorities


The analysis highlights the distribution of the dominant soils but also shows the
occurr
ence of
soil minorities and soil

endemism

per

BGRE
.

The concept of soil
endemism is

a

promising

one

for identifying rare, unique, and en
dangered soils
(Bockheim, 2005). Likewise
,

Goryachkin (2004) use
d

the
term “
soil minorities”
more or less for the same p
urpose. In this paper
,

soil minorities

refer
to

pedotaxa
that cover
less than 25,000 k
m
2

at Eu
ropean l
evel
. There are
45

soil types of this
kind

at the second WRB level.

Pedotaxa
that cover l
arger areas
are

considered
to
6


be

zonal soils,
although
some of th
em
may
be endemic
to

a given
BGRE
.

The
areas cove
red by pedotaxa

in the European continent follow the termed Willis
curve (Ibáñez et al.
, 2005a, 2005b), meaning that

many soil types cover sma
ll
areas within of each BGRE, while

only

a few
cover large extent
s
.


Several soil minori
ty types can be distinguished s
uch as follows:
(1)

Endemic
b
iogeographical pedotaxa
are
t
hose soil
minorities that only appear in one

single
BGRE; (2)
Endemic
g
eographical pedotaxa

correspond to soil types that appear in

a
small ar
ea but

cross

the boundaries of two
contiguous BGRE, indicating that
factors other than the bioclimate may explain soil cluster overlapping,
such as

paleogeographic

evolution
, geological

structure
,

and/or

land use histories; (3)
Disjoint soil minorities
are

soil types
of small areas

occurring in

two

or three

geographically separate c
lusters
, as well as more than a single BGRE
;

and (4)
Relatively dispersed or widespread soil minorities

are

pedotaxa that appear in
different BGRE and
are widely distributed ove
r

the continent
, reflecting possibly
specific combinations of soil forming factors that repeat at local scale.


3.
Results
: the biogeographical regions and their soil assemblages


Table 1 lists the
32
pedotaxa

and miscellaneous units
at the
first

WRB

level

per
BGRE
,

while Table 2 lists

the

147 pedotaxa and miscellaneous units
at
the second
level
.

Abbreviations

are the

ones

proposed by the WRB (
FAO,
1998).

Tables 3 and
4 show

the relative importance of dominant, subdominant and inclusion soils

in
each
BGRE

a
t
the first and second level
s

of the WRB (
FAO,
1998)
,

respectively
.
Table 5

highlights the levels of

correlation
between the various
BGRE using
pedotaxa at the second level
.

Figure 1 show
s

the
cluster
ing

of the
BGRE

using

the

WRB pedotaxa at the first leve
l.



3.1
Ar
c
tic Biogeographical Region


In the Arctic region, relief varies from high mountains to low
-
lying plains.
Typical landscape features include rocky terrains and rock outcrops, frost debris,
swamps, glaciers, and meadows (
Schultz
, 2002). Climate i
s characterized by low
temperatures, extreme annual variation in sunlight, and short intensive growing
seasons (
Schultz
, 2002). Most terrestrial ecosystems have developed over the last
10,000 years after the last glacial period. In the circumpolar area, va
st treeless
plains are
covered

by tundra, representing around 55
-
60% of the region
(Condé
and Richard, 2002)
. The ground in the tundra and polar deserts is permanently
frozen below the surface. The soil above the permafrost thaws during the short
summer se
ason but remains waterlogged (FAO, 2001). This allows some fast
-
growing vegetation to develop, conducing to the accumulation of organic
materials and the formation of peatbogs (
Schultz
, 2002
;

EC, 2010
). Permafrost is
7


discontinuous in the transition zone be
tween the tundra in the north and the
boreal forest in the south (RCMC, 2000). Current climate warming causes the
freezing
-
thawing alternations to be more frequent, contributing to soil erosion
(Condé and Richard, 2002). The

formation of surface patterns t
ypical of the arctic
environment (e.g., polygons, circles, sorted and non
-
sorted stripes, and mounds
with ice cores) creates short
-
distance variations in moisture and temperature
which enhance biodiversity (FAO, 2001).


In general, arctic soilscapes are
young and soils

are weakley

developed. Polar
desert
s

are covered by gelifraction debris with only traces of organic material.
Thick layers of
poorly decomposed

fibric organic material are common in the
tundra area. The most developed and fertile soils are
the
C
ryosols

(EC, 2010)
,
that have developed in sheltered, warm, well
-
drained sites (FAO, 2001).


Cryosols are the dominant soils

in the
A
r
c
tic region
, followed by

Histosols,
Podzols
,

and Albeluvisols.
Rocky

terrains
and
rock outcrops
cover
considerable
ar
eas
.
Dominant
pedotaxa at the second level are histic

and

turbic Cryosol
s
,

and
gelic Histosol
s. Soil assemblages comprise 14 and
38 pedotaxa

at the first and
second WRB level
s
, respectively.

Only one
endemic soil minority appear
s

in this
region, correspond
ing to

oxyaquic Cryosol
s
.


3.2
Boreal Biogeographical Region


The Boreal region is the largest biogeographical region of Europe,

covering about
25% of its territory
.
Most of the region lies below 500 m above sea level. Large
undulating plains and rolling h
ills resulting from

the

glacial and post
-
glacial
erosion

of weathered sedimentary rocks and igneous
-
metamorphic bedrocks
, are

the
dominant

landscape features
(Condé and Richard, 2003)
.
There are
innumerable

lakes that have formed during the deglaciation pe
riod

(EEA, 1995).

The climate is cool and mainly continental
, allowing a g
rowing season

of no
more than

fo
ur to
five months
.
It is Europe’s forest region, dominated by
conifers.

According to
Schultz

(2002)
, the main

plant communities
include

(i)
evergreen
conife
rous forest
s

(dark taiga) and some deciduous coniferous
stands
(
light taiga)
,

and

(ii)
wetlands such as mires, bogs
,

and fens
. These ecosystems
together with the numerous lakes and
rivers

form the characteristic mosaic
landscape
s

of the Boreal region

(Condé and Richard, 2003)
.

Forestry is currently
the main productive activity of the region;
intensive agriculture and animal
husbandry are
practiced

in the south
ern parts on

the

most s
u
itable soils and
accessible land
s; r
eindeer
-
based settlements and nom
adic herding are widely
spread in the north

(Condé and Richard, 2003)
.


F
ormed after the last glaciation
, soils are weakly

developed and shallow.

At
global scale
,

this biome
has the largest extent
s
of

Podzols,
Cambisols,
Hitosols
,

8


and
Umbrisols (
Schultz
, 2
002)
.

However, in the Boreal region of Europe, the
Albeluvisols

are the most extensive (EC, 2003, 2010).
Sporadic or
discontinuous

permafrost appear
s

in the northern areas

(
Schultz
, 2002)
.
The leaching of organic
acids from the conifer litter has led to th
e development of s
trongly layered,
acidic
, nutrient
-
poor

Albeluvisols and

P
odzols
.

M
ost boreal forest ecosystems

recycle the

nutrients

directly

from the deco
m
posing
litter
.

In the southern part,
especially near the Baltic Sea coast, nutrient richer soils,
mainly Cambisols, have
developed under

broadleaved deciduous
forest

(Condé and Richard, 2003)
.

Dystrophic peat deposits have filled in many of the small glacial lakes associated
with forests or mires.


Albeluvisols are the dominant soils

in the
B
oreal

reg
ion
, followed

by Podzols
and Histosols
, covering together
75% of the

region
. Water bodies

represent

3
%

of
the
area.

Dominant p
edotaxa at the second level
are
umbric Albeluvisol
s
,

followed by

haplic
,

r
ustic
and
entic Podzol
s
, histic Albeluvisol
s
,

and

dystri
c and
gelic Histosol
s
.
In total, 20 and
68 pedotaxa
occur in this
region

at the two levels,
respectively
.
The only
endemic soil minority
,

located

in
Russia
, corresponds to

gleyic Cryosol
s
.


3.3
Continental Biogeographical Region


The Continental region
is

a land

belt
that crosses most of middle Europe from
east to west
.

It is the largest biogeographical region

of the continen
t,
cove
ring
about 25% of its territory

(Condé and Richard, 2003)
.
The landscape is generally
flat in the north and hilly in the south,

including

mountains interspersed w
ith
lowland plains and plateaus (Condé and Richard, 2003).

The
region

is

drain
ed by
some of the mos
t

important rivers of Europe
,

the
floodplains

of which

are
conspicuous

territorial

elements
that have played

an important
role in
biodiversity

and settlement distribution

(FAO, 2001)
.

The norther
n

area is rich

in
lakes and wetlands (EEA, 1995)
.

T
he
climate
increases

in continentality

from
west to east, with warm

summers and
cold winters
.
The region is a main crop
-
producing ar
ea,
combini
n
g

intensive agriculture

and

alternative farming

(

Ostergren and Rice, 2004).

Permanent grasslands are decreasing, while forested
areas are increasing

(
Condé and Richard, 2003)
. The natural forest cover
is
dominated by
deciduous

trees
, but conif
ers are increasing mainly through

re
foresta
t
ion

in
several countries.
Sprawling

urban

areas and dense
infrastructural networks are causing

important
habitat fragmentation (
Condé
and Richard, 2003)
.


Soils
patterns
show a
gradation from
northwest

to
southea
st

(EC, 2001)
.
With
decreasing

rainfall,

P
odzols
are progressively
re
placed

by

less acidic and more
fertile

Luvisols and Cambisols

(EC, 2001)
.

Histosols and

Gleysols

are important
in the northern lake area and

in poorly drained valleys

(EC, 2005)
.

The most

9


fertile soils have formed on loess, a wind
-
blown fine
-
grained earth.
Black earth
chernozems, widespread in the eastern part of the region, are among the most
fertile soils in the world
(FAO, 2001)
.


Cambisols dominate

in the
C
ontinental
region
, followed

b
y Phaeozems,
Chernozems, Albeluvisols, Luvisols
,

and Fluvisols
, covering together
more
than
75% of this territory.
A
t the second level
,

albic Phaeozem
s are the most extensive
soils. U
mbric
A
lbeluvisols, dystric
and
eutric Cambisols, chermic and luvic
Chern
ozems

are also representative pedotaxa in this region
, each covering

more
than
10% of the territory
.

This is the region with the largest variety of pedotaxa at
the second level (108), together with

28

pedotaxa

at the first level
.

T
wo

endemic
soil minorit
ie
s

are present, corresponding to

salic Histosol
s

and
yermic Cryosol
s
.



3.4
Steppic Biogeographical Region


The Steppic region stretches from Romania in the west, across the lower section
of the floodplain of the Danube, along the north of the Black Sea and

the foothills
of the Caucasus
.

The topography consists of low
-
lying plains and, in the
northwest, undulating high plateaus with maximum elevation of 375 m in the
Volga Hills

(Condé and Richard, 2003)
.
A large proportion of the region
corresponds to the Ca
spian depression, with bottom areas lying as a low as 30 m
below sea level
(Bridges, 1990)
. The rivers

have weak bedslopes causing them to
overflow

frequently into bordering mars
hes and other wetlands.

Large saline
lakes
appear both
in coastal and inland a
reas

(EEA, 1995)
.
T
hick loess layers
deposited during the Pleistocene

form the substratum of the area
.

C
limat
e is
temperate continental
with

severe winter

frosts
and
low precipitation

that

favo
r
s
grassland at the expense of forest

(
Schultz
, 2002)
.

Steppes
are tree
-
less areas, with
vegetation dominated by Stipa and other turf grasses growing on black soils
,
mainly

Chernozems
.
For centuries, the steppes have provided a favourable
environment for nomadic pastoral activities, but nowadays 75% of the area has
be
en converted into arable land, particularly in the west
(
Condé and Richard,
2003)
.


Typically,
steppe

soils

are black earth
termed
C
hernozems.

These are deep,
h
umus
-
rich, fertile soils (FAO, 2
001). They have high biological activity that
contributes to dec
omposing the important biomass of the grass roots (EC, 2005).
The most fertile Chernozems
are found

in the north, along the border with the
contiguous Continental region
(Condé and Richard, 2003)
. Towards the south,

with increasing aridity, C
hernozems beco
me

progressively shallower and poorer
in humus and give way to chestnut
K
astanozem soils in the Black Sea area.
Intensive cultivation has led to widespread soil erosion on steep slopes and
strong salinization in the south

(EC, 2005).


10




Chernozems occupy a
bout 50% of
the Steppe

region.

Kastanozems, Fluvisols,
Calcisols, Phaeozems
,

and Solonetz
s

are subdominant
.

A
t the second level
,

the
calcic Chernozem
s dominate, followed by

chernic Chernozems, haplic
and

luvic
Kastanozems, endosalic Calcisols
,

and haplic S
olonetz
e
s.
In total, 20 and
65
pedotaxa

occur in this region at the two levels, respectively

E
ndemic soil
minorities

include

mollic Planosol
s
, haplic and salic Calcisols
,

and
calcic
Gleysol
s
.


3.5
Atlantic Biogeographical Region


The Atlantic

regio
n

closel
y interacts

with the bordering northeast Atlantic Ocean
and the North Sea
, extending from Portugal in the south to Norway in the north.

In general, coasts are rocky and heavely dissected, with numerous inlets, fjords,
rias, bays, peninsulas and islands, ex
posed to large tidal movements, while
sandy beaches with dunes, marshes and fenlands are particularly extensive along
the North Sea
(Condé and Richard, 2003)
.

The inland landscapes
are constituted
by

hilly uplands

alternating with

low
-
lying plains.
Volcani
c rocks occur in the

northern and western mountains
,

crystalline rocks

in

the

central mountains
, and

sedimentary

rocks

in
the
plains and low
-
lying hills
, frequently topped by loose
clastic deposits

(Condé and Richard, 2003)
. The climate is
temperate, with
oceanic influence
and

heavy westerly winds that
induce

mild

temperatures

and
relatively high rainfall

(
Schultz
, 2002)
.

After the last ice age, a land bridge
allowed species to move for some time from the present day continental Europe
to the British Isles,

but the number of indigenous species as well as of endemics
is relatively low compared to that of other regions

(Condé and Richard, 2003)
.
The region is densely

populated and some
of the largest urban areas of Europe
are found
near of the Atlantic

littora
l

(Ostergren and

Rice, 2004)
.


The Atlantic climate, with sustained rainfall throughout the year, provides
favorable conditions for soil development under deciduous natural

forest

(
Schultz
, 2002).

This allows the formation of deep
, humus
-
rich

soil
s.
Very
a
cid
soils

su
c
h as
podzols

are extensive in the north, in contact with the Boreal region;
elsewhere

Cambisols,

Luvisols
, and Fluvisols

are the dominant soils

(EC, 2005)
.
P
eat deposits

are frequent

in the most humid territories such as

in

Ireland and
Scotla
nd.
Shallow ranker soils occur

in the southernmost areas
, mainly in hilly
and mountainous landscapes

(EC, 2005)
.


Cambisols cover approximately 25% of
the
Atlantic
region
.

Luvisols
,

Gleysols,
Podzols, Leptosols,
and
Fluvisols

are less extensive
.

Urban

are
as
cover about
1
.
5% of the territory
,
and
water bodies are also abundant.
A
t the second level
,

haplic Luvisol
s are the dominant soils
,

followed by

eutric

and

dystric Cambisols,
haplic Podzols, dystric Histosols
,

and gley
i
c Luvisols.
Anthrosols
are also
11


idi
osyncratic of this territory.
In total, 22 and

69
pedotaxa

occur in the

region at
the two levels, respectively.

E
ndemic
soil minorities

include

plaggic Anthrosol
s
,

takyric Gleysol
s
,

h
aplic

Fluvisol
s,

and
haplic Planosol
s,

t
he

latter

two

appear
ing
only

in

t
he

UK
.

Placic Podzol
s are
idiosyncratic of Ireland and

the

UK and do

not
occur

in
the

c
ontinental part of this

region.


3.6
Alpine Biogeographical Region


The Alpine region includes some of the oldest

as well as

some of the

most recent
mountains of the wor
ld from the Mediterranean to western Siberia: the Alps, the
Scandes, the Pyrenees, the Carpathians, the Rhodopes, the Urals, the Caucasia
n
Alps
,

and the Dinaric Alps. Although different by origin and st
r
ucture
, they

have
in

common strong relief variations,

contrasted climatic belts
,

and varied
lithologies that heavely influence the distribution and diverstity of fauna,
vegetation
,

and soils

(
Schultz
, 2002)
.
A large proportion of the ecosystems and
habitat types is still

natural or semi
-
natural, with 40% for
est cover

and

25%

grassland

(Condé and Richard, 2003)
.

The region is rich in

plant
species

(Ozenda,
1994).

R
elief fragmentation

provides refuges for plants and animals and

favors

endemism
.

For generations
,

the Alpine region has bee
n

multi
-
functional,
com
bi
ning forestry and agriculture,
animal husbandry,
human settlements
,

and
outdoor/leisure activities.
This

e
quilibriu
m

is bein
g

threat
ened

by

changes in
land
-
use
practices
, abandonment of
traditional
small
-
scale agriculture,
construction of transport network
s, urban development, and mass tourism

(
Ostergren and Rice, 2004)
.
These changes cause fragmentation of habitats,
damage biotopes, disturb wildlife,

and induce soil erosion
(Condé and Richard,
2003)
.


Soil

formation
, horizonation
,

and profile

thickening

a
re
chara
cteristically

low in
alpine

environment

because of low temperatures and soil erosion

(
Schultz
, 2002)
.
Litter decomposes slowly, causing organic matter to accumulate on the soil
surface.
Soils are generally acid,

even
on limestone
s
.

Leptosols and
, t
o a

lesser

extent,

Cambisols are
typical

mountain
soils
,

but these soils are more dominant
in the
Europe
an mountains than elsewhere

(Ibáñez et al.
,

1998).


Cambisols
and Leptosols
are the most representative soils of

the Alpine region
.

Podzols, Regosols,
Phaeozems
,

and Albeluvisols

also cover large extents
.
Rock
outcrops
and glaciers are very idiosyncratic among miscellaneous areas.

A
t the
second level
,

haplic Podzol
s dominate
,

together with subordinate

dystric
Cambisols, dystric Regosols, alpic Phaeozems,

ren
d
zinic Leptosols, and
e
utric
Cambisols.
This is the region with the

second

largest variety

of

pedotaxa at the
second level

(105)
, together with 26 pedotaxa at the first level.

The only
endemic

soil minority
corresponds to

humic Cambisol
s that occur

in

the

Caucasian
range
s
.


12



3.7
Mediterranean Biogeographical Region


The Mediterranean region
has a varied

and contrasted

relief
,

with

a mosaic of

hill
ands,

mountains
,

plateaus
,

inland and coastal plains
, together with several
characteristic peninsular confi
gurations and a large number of islands. This
region, located

between the two continental plates of Africa and Eurasia,

has a
complex geologic history with strong

tectonic and volcanic activity
(Ibáñez et al.,
1996, 1998)
.
The
summer

season is

generally ho
t and dry, while the rest of the
year is

rather

mild
. Rainy seasons vary in different areas, appearing in
several

combinations (e.g. spring/autumn
, autumn
/winter, etc.)
(
Ibáñez et al.
,

1997)
.

The short spring and autumn seasons are critical periods for pla
nt growth.
Semi
-
arid areas are extensive
,

and human
-
induced desertification tends to increase
arid land conditions

via soil erosion

(Ibáñez et al., 1997)
.
Fire is a major problem,
together with erosion caused by
millenary

agriculture, overgrazing,
deforest
ation, and surface disturbances
(Ibáñez et al., 1997)
. The region
constitutes a frontier zone
and a center
of species

dispersion between Europe,
Asia
,

and Africa

(Blondel

and Aronson
, 1999). The flora of

flowering plants

is
very diverse
,

being

the third ri
chest in the world

with a high proportion of
endemic plants
.

The

Mediterranean basin at large concentrates
80% of all
European plant endemics
(Condé and Richard, 2003)
.
Because m
any areas were
free

of

glaciers

during the last glaciation, the region became
a species

refuge
and
an

important reservoir of plant diversity for the European Continent (Ibáñez et
al. 1997)
.


In Europe
Planosols and Calcisols
are not as common
in the Mediterranean Basin
inn contrast that occurs

in other areas belonging to the
Mediter
ranean b
iome

(Ibáñez et al., 1998)
.
Red calcar
eous soils on limestone
s

are
frequent (Ibáñez
e
t al.
,

1995).
F
erruginous ‘terra rossa’ soils

that have been correlated with saharian dust
deposition, are relatively common (Yaalon and Ganor, 1973
)
.

Andosols
onl
y
appear in small areas of Italy and some
volcanic Aegean

Islands
.

Shallow and
weakly developed

soils, including
R
endzinas,
R
egosols, and
Leptosols
,

are
extensive

as

a

consequence of past soil erosion.
The most fertile land for
agriculture is on
alluvial s
oils in coastal plains

(Ibáñez et al., 1995)
.


Cambisols dominate

in the Mediterranean
r
egion
, followed

by Leptosols,
Luvisols, Regosols
,

and Fluvisols,

that together

cover around 90% of this
territory.
A
t the second level
,

the most

widespread unit corresp
onds to

calcaric
Cambisol
s
, being also representative eutric
and
chromic Cambisols, calcaric
Leptosols, and calcaric Regosols.
In total, 25 and
74 pedotaxa

occur in this region
at the two levels, respectively.

E
utric and calcareous parent materials and soi
ls
are

most

representative

in
this territory
, related to the
marine sediments

that
have deposited

in the collision

fringe
between African and European plates.

This
13


region
, especially the Iberian Peninsula,

contains a large variety of
endemic

soil

minoritie
s
, including

plinthic
,

ferric and
gleyic Acrisol
s,

ferric Luvisol
s,

aridic
Gypsisol
s,

aridic Calcisol
s, and

tyonic Solonchack
s.

Andosol
s occur in

Sardinia
and
in several Aegean Islands
, but

many of them are not recorded

in the
European Soil Database
.

The
M
editerranean

r
egion is the only
continental area

that
has

one

idiosyncratic
pedotaxum

at the first WRB

level
,

i.e.

Gypsisols
.



3.8
Pannonian Biogeographical Region


The Pannonia
n

region
corresponds

to

the central Danubian

basin
, with the Great
Hungarian p
lain

as core

physiographic feature (Ostergren and

Rice, 2004).

R
elief
is
monotonous, mainly

alluvial plains

with shallow

water table
, spattered by low
hills and
surrounded

by

mountain ranges

(Condé and Richard, 2003)
.

The region
is
located at

the crossroa
ds of the climates
dominating
in the surrounding
biogeographical
regions:
A
tlantic
-
A
lpine to the west,
Mediterranean

to the south,
and
C
ontinental to the east.
It
represents a boundar
y

area

between
the domain of
the

deciduous forests and

that of

forest
-
ste
ppes

(Polunin and Walters, 1985)
.

Former extensive forests are nowadays replaced

by human
-
induced
grasslands
and steppes

(Csorba, 1995)
. Sandy

grassland
, i.e. the Hungarian Puszta, is now
the dominating type of habitat

(Polunin and Walters, 1985)
. A few la
rge lakes are
heavily influenced by eutrophication and tourist activities, while smaller lakes
are drying out or being salinized

(
EEA, 1995)
.


Most of the region is covered by deep dark soils, rich in organic matter and
nutrients, corresponding to
C
hernoze
ms

on windblown loess

in the plains

and
Phaeozems

in

dryer
flood
plain areas
.

Fluvisols have developed on recent alluvial
deposits on riversides.
The presence of

shallow ground
water and its evaporation
have caused the formation
of salty
S
olonchaks and
S
olon
etz
e
s

(
ESBN
-
EC
,

2005)
.
L
uvisols and
C
ambisols

are

frequent in
highlands
, while

A
ndosols and
C
ambisols

are
common

in volcanic mountains
.

Europe

is the continent
that has

the largest extent of

Chernozems
,

whereas

North America has the largest extent
of Phaeo
zems
(Ibáñez et al.,
1998
)
.



Steppe soils such as
Phaeozems
and Chernozems
occupy about
3
5% of
the
Pannonian
r
egion
,

being also representative

the

Luvisols, Cambisols, Fluvisols
,

and Gleysols.
A
t the second level
,

calcaric Phaeozem
s dominate, followed by

calcic Chernozems, gleyic Phaeozems, haplic Luvisols, and haplic Phaeozems
,
with each one of these covering

more than 10% of the territory.

Together, 18 and

60
pedotaxa

occur in this region at the two levels, respectively.
Whether
P
ha
eozems

and

Cher
nozems

were the representative soils of the original
deciduous forest landscape is matter of debate
. It is
likely that the current steppe
and grassland vegetation
and
associated
soil
s
capes are the cultural product of
longlasting

traditional land use.

14



3.9
Black

Sea

Biogeographical Region


The Black Sea region consists of

the

c
oastal
land that surrounds

the southern half
of the Black Sea
and includes a variety of landscapes from lowlands to highlands.
T
he most emblematic feature is the Danube delta,

the second la
rgest wetland of
Europe after the Volga
delta (
EEA, 1995;

Richard, 2003)
. The delta is a swampy
area forming a unique mosaic of t
errestrial and aquatic habitats

with a rich flora
and fauna

(Gastescu, 1993)
.

It

expands
seaward at the rate of approximately 3
0 m
per year

(
Condé and Richard, 2003)
. Limestone plateaus covered by loess
deposits surround the lowlands. South of the Black Sea
,

folded

mountain ridges
increase

in elevation toward the east

(Ager, 1980)
.

Climate is

Mediterranean
-
like
,
with moist

spring
and autumn
,
and

warm and relatively dry summer.
At higher
elevation, the
climate
shifts to

continental

with

moist

summer.
The original

forest

cover has been largely decimated to about 30% of the area
(
Gastescu, 1993)
.
The
alpine biome extends above 2000 m
elevation

(
Condé and Richard, 2003)
.

In the
EEA publications on BGRE, this area has been segregated from the surrounding
regions (i.e. Continental, Pannonian
,

and Mediterranean) because of its particular
setting. From a climatic and botanical point of view
, the territory could be
considered a hotspot of biodiversity containing a mix of Asiatic and European
plant assemblag
es, rather than a truly distinctive

biogeographical region
.


Weakly

developed alluvial soils
occur associated with flooded

wetlands
in the

Danube delta. Elsewhere
,

varied soil geography includes Chernozems

especially
in Romania,

b
rown forest soils
(
C
ambisols)
in
the southern part of the region,
and

a
cidic brown soils, rendzina
s,

and alluvial soils in the Turkish

area

(
Condé
and Richard, 2003
)
.


Chernozems a
nd Luvisols are the dominant pedotaxa

in the Black Sea
re
gion
,
together with subordinate

Chernozem
s,

Luvisol
s,

Regosols, Fluvisols, Leptosols,
and Vertisols.
A
t the second level
,

chromic Luvisol
s dominate
, being also
representative calcic

a
nd

haplic Chernozem
s
, calcaric Fluvisol
s,

and pellic
Vertisol
s
.
L
agoons, marshes
,

and other water bodies cover more than 12% of this
territory.
In total, 19 and
36 pedotaxa
occur in this region at the two levels,
respectively.
T
here are n
ot pedotaxa or soi
l assemblages

idiosyncratic of this
biogeographical region.


3.10
Macaronesian Biogeographical Region


The Macaronesian region refers to a group of

volcanic islands in the Atlantic
Ocean, including the

archipelagos of the Azores, Madeira, and the Canary
I
slands.

Past and present
-
time
volcanic activity

is a main factor of

contrasted

relief formation
, from steep cone slopes to gentle

lava flows

(Ferná
ndez
-
Palac
ios,
15


2001
)
. Landscapes range from xerophytic scrubs in
rocky areas of

the eastern
Canary Islands to

evergreen broadleaf forests in

the mountains of

Madeira and
the Azores

(Santos
-
Guerra, 1989)
. The climate is heavily influenced by the ocean

and, together with strong reli
e
f variations, creates l
arge differences in habitats
and species diversity among isl
ands and groups of islands

(Ibáñez and Effland,
2011)
.
There
is

a

considerable number o
f

endemics
,
many of them being
ancient
relict endemics with great affinity with
the European continent
Tertiary flora
(Santos
-
Guerra, 1989)
.

P
lant
endemism is

here

the h
ighest of

Europe

(Condé and
Richard, 2003)
.

The laurel forest is a unique formation and habitat that develops
on mountain slopes with reduced solar radiation, moderate temperatures, high
precipitation
,

and presence of fog

(Ibáñez and Effland, 2011)
.
The Ma
caronesian
region is a singular floral region within the Holarctic Kingdom i
n spite of its
small size (Fernán
dez
-
Palacios, 2001).

The rich volcanic soils and a favourable
climate allowed a rapid expansion of agricultural production for export.



Leptosols,

Cambisols, and Calcisols are the most widespread pedotaxa

in the
Macaronesian region
, followed

by Andosols and Solonchack
s
.
A
t the first level
,

20 pedotaxa

appear in this region

which constitutes

an intraplate hotspot
.

There
are n
o

soil

data available at

the second

WRB

l
evel

for this region

(Ibáñez and
Effland, 2011)
.



4. Discussion


4.1 Soil geography


At worldwide level
,

there
are clear

positive
relationship
s

between pedodiversity
and

the number of biomes

and

tectonic segments

of each continent

(Canieg
o et
al., 2007). Similarly,

the

number of pedotaxa or soil richness is positively
correlated

and increases

with
the

surface

area
of the

continents

(Ibáñez et al.,
1998)
.

The mountain biome has the

highest pedorichness

at global as well as at
Europe
a
n level
.

The
b
iomes

closest to the poles have lower

pedo
diversity, and
this trend occurs also on

the European continent

(Ibáñez et al., 1998)
.


With exception of the Black Sea and Pannonian regions, m
ost
BGRE have

idiosyncratic soil assemblages
, although

the cor
respondence between
BGRE

and
their respective soil assemblages is

somewhat

fuzzy
.
This corroborates that the
classical zonal

soil

concept
applies well

at a coarse scale of soil geography
analysis
at both

WRB

levels

but especially at the level of

Major
Soil

G
roups
(Tables 1 and 2).


In general
, soil assemblages

are more simi
lar between contiguous BGRE than
between

disjoint ones
, because the ecotones between neighboring regions are
more than often gradual (Ibáñez

et al.,

1998). Other factors may also have pla
yed
16


a role, such as for instance

inaccuracies

in
BGRE delineation

and/or

the

effect of

Holocene
climate changes

on modifying the boundaries

of the environmental
units after the last glaciation
(Ibáñez

et al.
, 1998).



From the dendrogram of Figure 1, t
hree

main

BGRE

clusters

can be
distinguished on the basis of

the

pedotaxa at the first WRB level

that constitute
th
eir respective soil assemblages
.

One
cluster
links the cold soilscapes of the
Ar
c
tic and Boreal regions
, although
their respective soil assemblag
es show
significant
differences. The second

cluster
shows

the

affinity between

the

Atlantic and

the

Mediterranean regions

that

have relative
ly

similar soil
assemblages
.

The
Alpine

region

relate
s
also to this cluster

because of its varied

soil
assemblage
s

a
nd the abundance of Cambisols.
All
t
h
ree regions have
, in
general,

pedotaxa

with

weakly

developed horizonation (Cambisols)
and
pedotaxa
with Bt horizons

under forest conditions

(Luvisols)
.

The

third
group
includes
the rest of the BGRE

that are characteriz
ed by

typical

grassland soils
(Chernozems, Kastanozems
,

and Phaeozems) mixed with forest

soils

(….).

T
he
dendrogram

highlights

the relationship between the Continental and the
Pannonian
r
egions.
The latter
is

in fact

a patch

within the

matrix

of the former
,

with an idiosyncratic pale
o
geographic

evolution

and land use
histor
y

that
determine

its current climate

and soil

assemblages

(EEA, 2002). Likewise
,

the

soil
assemblages of

the

Steppic and Black
S
ea regions are related

because the latter
can be considered

a variant of the

former

and/or a frontier
area with

the
Anatolian Asiatic
r
egion.




Table 5 show the matrix of correlation between
BGRE
using the pedotaxa at th
e
first WRB

level

(
FAO,
1998). From a pedological point of view, the most
idiosyncratic is

the Artic
region that

is not positi
vely correlated with the other

BGRE. The secon
d one is the Boreal region whose

soil assemblage

is

only

weakly
related
to

the continental one
, mainly along its

south
ern

boundary. The third one
correspond
s

to the Steppic r
egion whose soil

composition
shows affinity
only
w
ith the bordering

Black Sea and Continental

BGRE
. This reiterates

th
e

similarity

between
regions

with steppe environment

(
i.e. the Steppic, Pannonian
,

and Black
S
ea BGRE).

The

soilscapes of the

Macaronesia
n archipelagos are mainly related
with the soil assemblages of the Mediterranean

and Alpine regions and, to a
lesser extent, with those of the Atlantic

region
.
This resemblance is

because

the
larger isles (
e.g.
Canaries) have a mild Mediterranean climate a
nd most of the
m
are mountainous, while the

Azores and Madeira archipelagos
enjoy

a very mild
Atlantic climate. The
remaining

BGRE have soil assemblages related with

those
of

their neighbouring

regions.


4.2. Soil Minorities


17


T
he scale of the European Soil

Database (V2.0) (EC
,

2003) is too small to carry out
a fine anal
ysis of the soil cover
. However, at the date it is the only source of
harmonized soil inventory information at continental level. Because of map
generalization procedures or variable soil sa
m
pling densities in the contributing

countries, the pedotaxa population
s

might be incomplete in some areas
,
especially concerning soil minorities

and endemic soil
s.

On the basis of the
definitions provided in section 2.4, the following soil minorities and e
ndemic
soils were identified.


(1) Endemic
b
iogeographical pedotaxa.
There are

20 soil types
of this class that are
described together with the main soil assemblages of each BGRE.




(2)
Endemic g
eographical pedotaxa
.

They

include the following pedotaxa.



1.




P
laggic Anthrosol
s
: Atlantic and Mediterranean
BGRE

(Iberian Peninsula)



Plaggic Anthrosols: Atlantic and Mediterranean
BGRE (Iberian Peninsula)



G
leyic Chernozem
s
:
Alpine and Steppic BGRE (Caucasian ranges)



G
elic Regosol
s
: Alpine and Ar
ctic BGRE (nort
hern Scandinavian
shoreline)



Y
ermic Cryosol
s
:

Boreal and Continental BGRE (east of Central Europe)



G
leyic Chernozem
s:

Continental

and

Atlantic BGRE

(north of Central
Europe)



L
uvic Planosol
s:

Alpine and

Steppic BGRE

(northeast of the Black Sea)



A
renic Umbri
sol
s
:

Atlantic and Mediterranean BGRE

(shoreline in
Portugal)



M
ollic Fluvisol
s:

Pan
n
oni
an in contact with Continental and Alpine BGRE



H
aplic Cambisol
s: Atlantic and Continental BGRE

(several
adjacent

patches
)



G
leyic Vertisol
s:

Mediterranean and Alpine BGRE

(s
mall area
s

in the
Balkan
s)



(3)
Disjoint soil minorities
.

They include the following pedotaxa.






U
mbric Leptosol
s:

m
ainly Steppic but also Alpine BGRE

(Central Europe)



M
ollic Andosol
s
:

Mediterranean and Continental BGRE
Italy and
Central
Massif of Fr
ance



D
ystric Andosol
s:

Mediterranean, Alpine, and Continental BGRE (
Central
Massif in France;

continental

Greece and Aegean

i
slands
;

and Carpathian
ranges)

18




U
mbric Andosols
:

Mediterranean, Alpine, and Continental BGRE (
Central
Massif in France; continental
Greece and Aegean islands; and Carpathian
ranges)


(4)
Relatively dispersed or widespread soil minorities
.

They include the following
pedotaxa.





S
alic Fluvisol
s
:

Continental and Steppic BGRE
(small patches along

the

southeaster
n border of
the continent)



Gleyic Solonchak
s:

Several

BGRE
(southern
halft

of the continent)



Calcic Kastanozem
s: Mediterranean, Black Sea, and Steppic BGRE

(
southeast

of Europe)



A
lbic Arenosol
s:

Atlantic, Boreal, and Continental BGRE (
shorelines of
northern
Europe)



U
mbric Fluvisol
s
: Boreal and Steppic BGRE

(
few areas in

the north and
southeast of the continent)



L
ithic Leptosol
s:

Artic and Alpine BGRE (few areas on the northern
shoreline of Russia and in the northern Caucasian range, with very cold
climate
)



G
leyic Umbrisol
s:

Boreal a
nd Continental BGRE

(disperse
d

small patches)



H
umic Acrisols
:

Alpine, Boreal, and Continental BGRE

(
disperse
d

small
patches)



T
hionic Fluvisol
s: Several BGRE

(
dispersed

small patches
,

mainly in
shoreline localities)



D
ystric Luvisols
:

Continental, Pannonian,

and Alpine BGRE (
Central
Massif in France and Central Europe around

the

Pannonian region)



H
aplic Regosol
s: Several BGRE

(dispersed
small
patches
)


Some BGRE are richer than others in soil minorities and endemic soils
. This is

because of their complex geol
ogic history and structure, geomorphic evolution,
and physiographic configuration that create a variety of local conditions and

ecological

niches

where soils departing from the idiosyncratic zonal soils form.
The Mediterranean region, for instance, contain
s more endemic soil minorities
than any other

BGRE
, with most of them in the Iberian Peninsula. The west side
of this territory corresponds to an old craton with Palaeozoic rocks partly
covered by a Pliocene weathering mantle. In the southern parts that ha
ve not
been exposed to glacial erosion during the Pleistocene, there are endemic soil
minorities with old, nutrient
-
depleted soils such as plinthic, ferric and gleyic
Acrisols, and ferric Luvisols. The eastern side of the Iberian Peninsula has two
areas wi
th the most arid climate of Western Europe and contains large extents of
Miocene inland
-
sea evaporates. Three endemic soil minorities result from these
conditions, including aridic Calcisols, takyric Solonchaks, and aridic Gypsisols.
Half of the endemic so
il minorities of the Atlantic region, including haplic
19


Fluviols, haplic Planosols, and placic Podzols, only appear in the British Isles,
reflecting the particular geographical history of this archipelago as compared to
the Atlantic part of the continent. F
urthermore
, some endemic soil minorities
occur exclusively in the southeaster
n

part of the continent, in small

adjacent
areas of different BGR
E, reflecting distinctive geographical histories.



4.
3
.

Pedodiversity

and pedorichness



Tables 6 and 7 show the

results of the pedodiversity analysis for each BGRE.
Richness values

(
S
),

or number of pedotaxa
,

both for the first and second level of
the WRB (
FAO,
1998) vary according to the size of the BGRE and the latitude.
Thus, the BGRE with less pedotaxa are smal
l ones and/or located nearest to the
North Pole (
i.e.
Arctic and Boreal BGRE).

This pattern is similar to the
fragmentation of the global pedosphere in
to

climate zones or biomes (Ibáñez et
al., 1998).


T
he number
s

of soil types
(
i.e.
pedorichness)
of
th
e
BGRE increase with their
respective

surface

areas conforming to a power
law
, as

it

also occu
r
s

in
all
pedodiversity analys
e
s
,

independently of the scales and areas under study
(Ibáñez et al., 2009)
.
Table
s

6 and 7 show

that
pedorichness at
the
first and
second

WRB

level
s

follow
similar
patter
n
s

for
all BGRE
. This

trend is true
whether pedorichness is
analyse
d using

absolute values

or
in relation
to
the area
of each

BGRE

(density

estimate
d

as

S
/Area
)
,
with only minor differences
.
Therefore
,

the richness in

pedotaxa

at

the

f
irst

WRB

level is a suitable indicator of

that of

the second one.

However,

when the pedorichness per area of each BGRE
is considered (density)
,

the small
regions have

the

highest values

but

without

endemic

soil

minorities
. It is a rule th
at bio
diversity values of

small land
tracts

in
a given study (e.g. small islands of an archipelago) are the mo
s
t difficult to
predict. This deviation from the theory is

not

yet

well understood and is know
n

in the ecological literature as the “small
-
island
effect
” (e.g. Burns

et al.,

2009
)
.
Ibáñez et al.
(
2005a,b) recognized

th
e same

pattern in pedodiversity analysis
,

as
well as the lack of id
ios
yncratic and endemi
c

soils

in
small
island
pedogeography
, and proposed

an explanation

thereof

in pedological terms

(Ibáñez and Effland, 2011)
.

The deviation from

the theory could be a sampling
artefact of power law
distributions
(
e.g.
Ibáñez et al.
,

2005a,b).
Th
is sampling bias

seems logic in view t
hat richness
-
area curves follow

power law
s: as the area
increases,

mor
e objects (pedotaxa, species) can be found on it, but not in a linear
way because these object
s

(classes, taxa) are not infinite in number and they are
not everywhere.
Furthermore,

the exponent of the power law of

the

pedorichness
-
area relationship is less

tha
n

1

irrespective of the scale
, both in
pedodiversity and biodiversity
studies (Ibáñez et al.
, 2005
, 2009)
.



20


As a consequence of the former
,

s
mall
territories

(e.g.

the

Black Se
a
,
Macaronesian,

and Pannonian
r
egions) have higher diversities when the
de
nsity

is
taking

into account. However
,

in absolute terms
,

the driving force of the area
effect act
s

in the
opposite

direction

to the

small
-
island

effect

.
In other words
,
when

the are
a

increase
s
, the

pedorichness increase
s

more or less depending
on
the ha
bitat heterogeneity of the territory studied

(Ibáñez et al.
,

2005a,b)
.

However
,

a phenomenological
explanation

is also feasible. The
Pannonian

r
egion
consist
s

of

an association

of the Pannonian plains
and

the
surrounding
mountains. The latter have soil ass
emblages

similar to those

of the
C
ontinental

BGRE, including

steppe

and for
est

soils. Th
e

Macaronesian region

consists of
archipelagos

some of which have Atlantic climate

and others

have

Mediterranean
climate
. In the

latter,

volcano

slopes exposed to the t
rade winds
are
moist
,
while

the opposite
slopes are arid
.
These contrasting conditions repeat

over small territories

(see values in Tables 6 and

7). Finally, the Black
Sea region

is a heterogeneous region that
includes a variety of

climate conditions (
i.e
.
Mediterranean, Continental
,

and Steppic)
and

soilscapes.



I
n absolute
terms,
t
he Alpine
region

is the
richest

in habitat heterogeneity
over

short distances (e.g.
soil
and vegetation catenas,
altitudinal

climate belts
).
Environmental heterogeneity
is compounded by the fact that the region is
spatially fragmented and
spread across

the continent, with reliefs of different
origin, age,

and
lithology
.
Therefore
,
the Alpine

r
egion

is
highly

diverse in soils
,

coming just

after the Continental
and
the Medi
terranean

regions
.
The same
trend
can be observed

in

mountainous and Mediterranean
biom
es

at global level
(Ibáñez et al.
,

1998
; Minasny et al., 2010
)
.
In general, area and relief are correlated
via power laws
,

and both of them

are correlated

with pedorichn
ess and
pedodiversity (Ibáñez et al., 2005a,b
;

Ibáñez and Effland, 2011).

This could
explain why the Continenta
l region has high

pedorichness and pedodiversity
.

Likewise
,

the high

values of the Alpine and the mountainous Mediterranean

regions

seem to

corre
spond to the relief effect
.


Pedodiversity as shown by

the

Shannon Index (
H
’) follows different patterns
because of differences in equitability (
E
). In the small BGRE, equitability values
are higher and thus also their respective pedodiversities. This mea
ns that the
areas covered by the pedotaxa are more equitably distributed in smaller than in
larger biogeographical regions where zonal taxa are in general dominant. The
only exception to this patte
rn is the Alpine

region where there are no zonal soils
but
idiosyncratic soils according to climatic altitudinal belts.

It is rather intuitive
that

in

regions

with high soil

zonality and

only a few dominant

pedotaxa
,

equitability (
E
) values are lower

that in others,
decreasing the relation between
pedorichness and

pedodiversity
.



21


5. Conclusions


The analysis of

the

soil assemblages and pedodiversity of

the

Europe
an continent
support
s

the concept of soil zonality
.

M
ost of
the
BGRE

are characterized by
dominant soils. However
,

driving forces

other than climate must
be taken into
account to explain the

soil assemblages
, as for instance
geology and relief

in the
case of

the
Iberian Peninsula and

the

British Isles
, or

pale
o
geographic evolution

and land use history

in the
case of the Pannonian

region which
seems

to be

a
patch
within
the Continental

region.

Although
the Black Sea

area is not a soil
region on its own, it is an interesting and very special hotspot

from
a

bio
diversity
point of view.

S
oil assembl
ag
es of the north
ern

cold regions are clearly
different
from thos
e of the other regions. The
Atlantic and Mediterranean regions
and, to
some extent,
the Alpine

region
are

mutually

related. Finally
,

most continental
soilscapes constitute a mix of typic
al

s
teppe and forest soils.


E
ndemic
soil
minoriti
es have been identi
fied

in m
any BGRE
, with varying
patterns from region
-
specific to transcontinental and for adjacent to disjoint.


Equitability is highe
r in the BGRE

with less dominant idiosyncratic pedotaxa. In
the more homogeneous northern regions
,

there may be an indirec
t relation
between area, relief
,

and pedodiversity.
Although soil assemblages do not match
exactly the biogeographical regions
, they

could be used to detect past climate
changes.

However, the European Soil Database may be too coarse to fully
characterize a
nd evaluate the pedodiversity of the European continent.



Soils are part of our natural heritage and should be preserved as natural as
possible in selected critical areas (Ibáñez et al., 2008). The design and
implementation of a Pan
-
European network of
natural soil reserves would allow
using pristine or only slightly disturbed pedotaxa as benchmark soils for future
soil monitoring purposes (Ibáñez et al.
,

2008).


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Table 1

Soil assemblages at the first level of the WRB (FAO, 1998) in percentage
respect to the area of each of each Biogeographical Re
gion


Table 2

Soil assemblages at the second level of the WRB (FAO, 1998) in
percentage respect to the area of each of each Biogeographical Region


26


Table 3
.

Dominant and the second most dominant soil type at the first
l
evel of the
WRB (FAO 1998). Data in p
ercentage respect
to the area of each of each
Biogeographical Region

Peotaxa 1
st

level
of
t
he WRB

Dominant pe
dotaxa

Subdominant pe
dotaxa

BIOGEOREGIÓN

Pedotaxa

Area %

Pedotaxa

Area %

Arctic

CR

26,3

HS

9,2

Boreal

AB

36,5

PZ

27,
9

Continental

CM

17,1

PH

15,9

Atlantic

CM

24,6

LV

15,8

Steppic

CH

47,7

KS

15,1

Pannonian

PH

24,
1

LV

13,
7

Black Sea

CH

23,
1

LV

21,7

Mediterranean

CM

36,8

LP

19,2

Alpine

CM

23
,
0

LP

21,9

Macaronesian

LP

25,3

CM

17,4


Table 4
. Dominant and the second most dominant soil type
at the second level of
the WRB (FAO 1998). Data in percentage respect
to the area of each of each
Biogeographical Region



Peotaxa 2
nd

level
of the WRB

Dominant pedotaxa

Subdominant pedotaxa

BIOGEOREGION

Pedotaxa

Area
%

Pedotaxa

Area
%

Arctic

CRhi

11,7

CRtu

10,
3

Boreal

ABum

19,7

PZha

14,
6

Continental

PHab

9,5

ABum

8,
2

Atlantic

LVha

9,7

CMdy/CMeu

8,
3

Stepp
ic

CHcc

23,6

CHch

20,9

Pannonian

PHca

9,8

PHgl

7,8

Black Sea

LVcr

19,
6

CHcc

12,
2

Mediterranean

CMca

15,2

CMeu

9,4

Alpine

Pzha

13,1

CMdy

11,9






27


Table
6
. Pedodiversity
a
nalysis
a
t the
first

WRB

level (
FAO,
1998) for the Biogeographical
Regions of Europe


BGRE

S

H’

E

S/Area x1M

Area

Area %

Boreal

20

2.49

0.72

7.02

2.845.246,65

28,42

Continental

28

2.55

0.74

10.8

2.589.669,71

25,87

Steppic

20

2.52

0.73

17.5

1.142.031,76

11,41

Mediterranean

25

2.42

0.70

27.0

926.225,60

9,25

Alpine

26

2.72

0.78

29.7

875.461,40

8,75

Atlantic

22

2.41

0.69

26.1

842.181,75

8,41

Arctic

14

2.17

0.63

23.1

605.273,22

6,05

Pannonian

18

2.61

0.75

110

163.632,68

1,63

Macaronesian

20

2.65

0.77

1835.2

10.898,16

0,11

Black Sea

19

2.57

0.74

2001.9

9.491,71

0,09

S =
r
ichness; H’ = Shannon Index (Shannon and Weaver
I
=
ㄹ1
9
);=䔠==
equátabálá瑹t=䅲敡
=

a
r敡
=
of=each=扩ogeographácal=r敧áo渠
=
á渠
k
m
2




Table 7.
P
edod
iversity Analysis
at the second

WRB

level (
FAO,
1998
) for the Biogeographical
Regions

of Europe





BGRE

S

H’

E

S/Area x1M

Area

A
rea %

Boreal

68

3.27

0.66

2.39

2.845.246,65

28,42

Continental

107

3.67

0.74

41.31

2.589.669,71

25,87

Steppic

65

3.34

0,67

56.91

1.142.031,76

11,41

Mediterranean

74

3.35

0.67

79.89

926.225,60

9,25

Alpine

105

3.62

0.73

119.94

875.461,40

8,75

Atlantic

69

3.49

0.70

81.93

842.181,75

8,41

Arctic

38

3.03

0.61

62.78

605.273,22

6,05

Pannonian

60

3.49

0.70

366.67

163.632,68

1,63

Black Sea

36

3.03

0.61

3792.67

9.491,71

0,09

S =
r
ichness; H’ = Shannon Index (Shannon and Weaver
,

194
9
); E = equitability; Area
=
a
rea

of
each biogeographical region

in
k
m
2

28


Table 5. Correlation
m
atrix between

the

B
iogeographical
R
egions

of Europe

using

the pedotaxa
at
the first
l
evel of the WRB (
FAO,
1998)



Alpine

Arctic

Boreal

Atlantic

Mediterranean

Black Sea

Continental

Steppic

Pannonian

Macaronesian

Alpine

1

0,04

0,40
*

0,72
*

0,79
*

0,1

0,60
*

-
0,01

0,32

0,58
*

Arctic

0,04

1

0,2

0,01

-
0,09

-
0,16

-
0,09

-
0,13

-
0
,16

-
0,15

Boreal

0,40
*

0,205

1

0,28

-
0,04

-
0,12

0,31

-
0,1

-
0,06

-
0,14

Atlantic

0,72
*

0,015

0,28

1

0,80
*

0,2

0,62
*

-
0,1

0,41
*

0,47
*

Mediterranean

0,79
*

-
0,09

-
0,04

0,80
*

1

0,22

0,53
*

-
0,07

0,34

0,71
*

Black Sea

0,1

-
0,16

-
0,12

0,2

0,22

1

0,42
*

0,57
*

0,
43
*

0,02

Continental

0,60
*

-
0,087

0,31

0,62
*

0,53
*

0,42
*

1

0,37
*

0,83
*

0,2

Steppic

-
0,01

-
0,128

-
0,1

-
0,1

-
0,07

0,57
*

0,37
*

1

0,3

-
0,08

Pannonian

0,32

-
0,157

-
0,06

0,41
*

0,34

0,43
*

0,83
*

0,3

1

0,08

Macaronesian

0,58
*

-
0,152

-
0,14

0,47
*

0,71
*

0,02

0,2

-
0,08

0,08

1


(*)
corr
elations are significant at p <

0
.
5




Figure 1: Cluster
a
nalysis of the Biogeographical
R
egions of Europe using
pedotaxa at the
first

le
vel of the WRB (
FAO,
1998) (
using complete


l
inkage
)