2. MÉTODOS GENERALES
2.3. Caracterización de las estructuras
Rannveig Guicharnaud
4.1 Pedological hypothesis tested
A pedological data quality control was conducted on the LUCAS soil dataset as to assess expected trends in soils systems in terms of the soils pedology. These included;
(1) Correlations between soil organic carbon (OC) and nitrogen (N) as soil organic matter is composed of both, carbon (C) and N in a relatively fixed ratio of 12:1 in mineral soils to around 30:1 in organic soils. Soil samples exhibiting ratio in excess of 40:1 need further consideration.
(2) Correlation between the soil cation exchange capacity (CEC) and clay with soil OC, as both are important players in the soil CEC. The soil organic fraction is believed to account for 50-90 % for the soil CEC due to the large amount of negatively charged surface sites available to bind cations.
Furthermore, clays are also an important contributor for cation exchange capacity due to isomorphic substitution where Si+4 and Al+3 in clay crystal lattices are replaced with cations of lower positive charge or by deprotonation of hydroxyl groups on clay surfaces leading to excess negative charge available to bind cations from soil solution.
Additionally assumptions where made towards the fact that;
(1) Greater OC concentrations should be expected in forest/grassland soils compared to cropped soils, as ploughing, which often is associated with cropped systems, increases soil organic matter decomposition;
(2) Greater phosphorous (P) and potassium (K) where present in cropped soils compared to other forest soils due to fertilizer application of cultivated soils;
(3) Higher pH was expected in cropped soils compared to organic soils (such as forest soils, wetland soils, ≥20% OC), due to liming which is often associated with cultivation increasing the soil pH.
Moreover cultivated soils often have higher pH due to lower soil OC content and therefore lower supply of organic acids;
(4) Calcium carbonate (CaCO3) was not expected at sites with low pH as its solubility is pH dependent and it does not form under acidic conditions;
(5) Principal component analyses (PCA) was conducted on the LUCAS topsoil dataset to assess which measured soil parameters (pH, CaCO3, CEC, clay, C%, N%, K, P, sand, silt, coarse) differentiated soils from different land cover groups.
4
4.2 Results Figure 4.1 g LUCAS-Topso obvious outl dataset is m more detaile relationships
Figure 4.1 Ov N% vs OC%
CaCl2, P mg
gives an ove oil Survey. I liers may ea more conven
ed study ma s.
verview of se
%, CaCO3 vs p g kg-1 vs clay
LUCASTOP
erview of se In addition asily be det iently sorted ay be condu
lected relatio tected from d according
cted to iden
nships of soil g kg-1 vs clay ples collected bland, grasslan
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tionships of ng the range this figure.
to land use ntify outliers
l properties (C
% , CEC meq d in the LUCAS
nd, bare land,
ology,dataa S project in al , peat and ma
ndresults
ties in all sa arameters in e large num on and/or co les not disp
mg kg-1 vs p CEC meq kg-1 ll land cover g arsh).
amples colle n the survey mber of data
ountries of o playing logica
H CaCl2, C:N v
1 vs clay %, O groups (cropla
ected in the y, the most a points the origin and a al pedologic
vs P mg kg-1, OC % vs pH
and, forest, e
t e a c
As expected groups (cro Figure 4.2 d agreement present in a
N% N%
Black =
d, strong po p, forest, gra displays corr
with the as a relatively f
Figur
= Cropland, Re
LUCASTO
sitive correla assland).
relations bet ssumptions fixed ratio of
re 4.2 Relatio ed = Forest, G
OPSOILSURV
ations where
tween C % a made, that f around 12:
nship betwee Green = Scrub
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e found bet
nd N % in d soil organic 1 and above
en N% and C%
land, Purple =
dology,data
ween N % a
ifferent land c matter is e.
% in different
= Grassland, B
andresults
and OC % in
d cover syste composed
land cover sy Blue= Bare lan
n all soils an
ems (Fig. 4.2 of both C a
ystems.
nd, Orange = W
nd land cove
2). This was i and N and
Wetlands.
er
in is
CNCN
The C:N r other wo
C:N C:N
Black = C
ratios of soil ords the soils
Figure 4 Cropland, Red
LUCASTOP
ls were gene s became inc
4.3 Relationsh = Forest, Gre
PSOILSURVE
erally betwee creasingly N
hip between C een = Scrubla
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en 10:1 and depleted (Fi
:N ratio and C nd, Purple = G
ology,dataa
20:1 and we ig. 4.3).
C% in differen Grassland, Blu
ndresults
ere increase
nt land cover c ue = Bare land
d with eleva
classes.
d, Orange = W
ated C%, in
Wetlands
Genera croplan contribu
CEC (meq kg-1) CEC (meq kg-1)
Clay vs CEC
Figure
Black
lly, there wa d, forest an utor for soil
4.4 Relations
k = Cropland,
LUCASTO
as a strong nd grassland CEC due to t
ships between
Red = Forest,
OPSOILSURV
positive rela d systems (F their reactive
n soil cation ex
Green = Scru
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ationship be Fig. 4.4), sup
e surfaces.
xchange capa systems ubland, Purple
dology,data
etween the s pporting the
acity CEC and s.
e = Grassland,
andresults
soil CEC and e theory that
soil clay cont
, Blue = Bare
d the soil cla t clays are
tent in differe
land, Orange
ay content i an importan
ent land cover
= Wetlands in nt
r
CEC(Cl)CEC(Cl)
There wa is in agre
CEC (Cmol) CEC (Cmol)
Figure 4
Black
Moreove soils (Fig
Figu Grey do
as likewise g eement with
4.5 Relationsh
= Cropland, R
r, the soil CE gure 4.6).
ure 4.6 Soil CE ots represent
LUCASTOP
generally a p OC organic
hips between
Red = Forest, G
EC was the g
EC dependenc cropland, red
PSOILSURVE
positive corre matter bein
soil cation ex
Green = Scrub
greatest whe
ce on organic dots represe dots
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elation betw g negatively
xchange capac systems.
bland, Purple
en both high
C % and clay nt forests and is proportiona
ology,dataa
ween the soil y charged inc
city CEC and s
= Grassland,
clay concen
y % in a select d purple dots al to CEC.
ndresults
l CEC and th creasing the
soil OC conten
Blue = Barela
tration and
ted member s represent gra
he soil OC (F soil CEC.
nt in different
and, Orange =
C % where m
state country asslands. The
ig. 4.5). This
t land cover
Wetlands.
measured in
(Spain).
size of the s
Althoug ls than cropp
dense root
re 4.7 Soil OC re
nd soils disp e exhibited
d in minera attributed to andard devia ot been remo
LUCASTO
y was high in ped soils (Fi system. In fo
C %. Black col epresent gras
played the h lower P lev al-organic co o lack of fert ations of me oved yet (Fig
OPSOILSURV
n all land use gure 4.7). H orest soils, h
lumns represe sland. Error b
highest pH vels (Figure omplexes. It tilization and eans for P an gures 4.9 an
VEYMethod
e classes, gr High OC leve high OC are r
ent cropland, ars represent
values of a 4.9). This i
was assum d cation leach nd K in grass d 4.10).
dology,data
rassland and els are a cha related to hu
red columns r t one standard
all land cov s commonly med that low
hing which is sland soils a
andresults
d forest soils aracteristic o umus rich to
represent fore d deviation of
er groups ( y observed wer K conce s prominent are due to ou
s, demonstra of grassland psoil layers.
ests and purp f means.
Figure 4.8).
in forest so entrations in at the low p utliers in the
ated greater ds mainly du
ple columns
Forest soil oils due to n forest soi pH (Fig. 4.10 e dataset tha
C
Figure 4
Figure 4
4.9 Soil P mg
.10 Soil K mg
LUCASTOP
kg-1.Black col
Error
g kg-1. Black co
Error
PSOILSURVE
lumns represe re bars represen
olumns repres re bars represen
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ent cropland, epresent grass nt one standa
sent cropland epresent grass nt one standa
ology,dataa
red columns sland.
ard deviation o
, red columns sland.
ard deviation o
ndresults
represent fore
of means.
s represent fo
of means.
ests and purp
rests and pur
ple columns
rple columns
In the LUCA above (Figu
CaCO3 (mg kg-1) CaCO3 (mg kg-1)
F Bl
AS dataset, c ure 5.11) wh
Figure 4.11 Re ack = Cropland
LUCASTO
calcium carb ich was expe
elationships b d, Red = Forest,
OPSOILSURV
bonate (CaCO ected as CaC
between soil C Green = Scrub
VEYMethod
O3) notable c CO3 is highly
CaCO3 and soi bland, Purple =
dology,data
concentratio soluble und
l pH (CaCl2) in Grassland, Blue
andresults
onswere only er acidic con
n different lan e = Bare land, O
y observed a nditions.
nd cover class Orange = Wetla
at pH 6.5 an
ses.
ands
nd
P f
Principal com from other s
Figure select
Conclus From a between than diff
mponent ana oils within th
4.12 Principa ed member s LU
ions pedological
the land co ferent geoch
LUCASTOP
alyses revea he LUCAS so
al component tate country ( CAS soil data
point of vie over groups
emical relat
PSOILSURVE
led that the oil dataset (F
analyses plot (Hungary). Th set (sand, silt
ew, the LUCA were obser tionships.
EYMethodo
soil texture Figure 4.12).
t showing gro e vectors incl t, clay %, OC%
AS topsoil d rved as cont
ology,dataa
was a stron
uping of soil f uded are all m
%, P mg kg-1, K
data displaye trasting abu
ndresults
ng factor dif
from differen measured soil K mg kg-1, pH
ed expected undance of t
fferentiating
nt land cover g l parameters
CaCl2).
d behaviour.
the measure
g forest soils
groups in a within the
Differences ed variables s
s s