Academic Edi o s: Fe enc Fodo and
Mau izio Badiani
Recei ed: 20 Sep embe 2024
Re ised: 15 Decembe 2024
Accep ed: 26 Decembe 2024
Published: 27 Decembe 2024
Ci a ion: San os, E.S.; Ab eu, M.M.;
Rossini-Oli a, S. Soil–Plan
Cha ac e iza ion in Ag osil opas o al
Sys em Es ablished in a Fe-Mn
Abandoned Mine A e Long-Te m
Closu e. Plan s 2025,14, 60. h ps://
doi.o g/10.3390/plan s14010060
Copy igh : © 2024 by he au ho s.
Licensee MDPI, Basel, Swi ze land.
This a icle is an open access a icle
dis ibu ed unde he e ms and
condi ions o he C ea i e Commons
A ibu ion (CC BY) license
(h ps://c ea i ecommons.o g/
licenses/by/4.0/).
A icle
Soil–Plan Cha ac e iza ion in Ag osil opas o al Sys em
Es ablished in a Fe-Mn Abandoned Mine A e
Long-Te m Closu e
E ika S. San os 1,* , Ma ia Manuela Ab eu 1and Sabina Rossini-Oli a 2
1LEAF—Linking Landscape, En i onmen , Ag icul u e and Food Resea ch Cen e ,
Associa e Labo a o y TERRA, Ins i u o Supe io de Ag onomia, Uni e sidade de Lisboa, Tapada da Ajuda,
1349-017 Lisbon, Po ugal; [email p o ec ed]
2Depa men o Plan Biology and Ecology, Uni e sidad de Se illa, A da. Reina Me cedes S/N,
41080 Se ille, Spain; [email p o ec ed]
*Co espondence: [email p o ec ed]; Tel.: +351-213653446
Abs ac : Small abandoned mining a eas o Fe and Mn oxides loca ed in he Po uguese
sec o o he Ibe ian Py i e Bel (SW o Eu ope) ha e been con e ed in o ag osil opas o al
sys ems wi h e y ew en i onmen al managemen measu es a e hei closu e. Al hough
a he landscape scale, no isible di e ences we e obse ed be ween he o me mining
in e en ion a eas and adjacen a eas, i is essen ial o assess he s a e and en i onmen al
isk o he soil–plan sys em, especially in he he baceous pas u es g azed by domes ic
animals. This was ca ied ou in he Fe agudo mining a ea, whe e an ag osil opas o al
sys em, composed o holm oak and d yland pas u e, had been es ablished a e he closu e
o he mine a
≈
45 yea s. The soils p esen ed neu al pH and a iable e ili y deg ee. The
pseudo- o al soil concen a ions o Cu, Mo, and Zn exceeded he Po uguese limi alues
es ablished o ag icul u e use (>180 mg Cu/kg; >8.2 mg Mo/kg; 349 mg Zn/kg), bu
hei soil a ailable ac ions we e small (<8.4% o he pseudo- o al concen a ions). T ees
and he baceous plan s showed good de elopmen , and he concen a ions o he elemen s
(excep Mn) we e conside ed no mal o su icien . Fo Mn, mos o he plan samples
exceeded phy o oxic Mn alues, bu no isual signs o phy o oxici y we e obse ed. Only
he concen a ions o Fe and K in he shoo s o some he baceous samples exceeded he
maximum ole able le els o ca le and sheep, so he isk o animals can be conside ed
small since o he sou ces a e p esen in animal eed. In gene al, his ag osil opas o al
sys em did no pose a signi ican en i onmen al isk.
Keywo ds: d yland pas u e; he baceous co e ; holm oak; biogeochemical cha ac e iza ion;
en i onmen al isk
1. In oduc ion
Mining ac i i ies a ec app oxima ely 4
×
10
5
km
2
o land wo ldwide [
1
] and can
lea e a deg aded a ea i en i onmen al managemen issues a e no conside ed du ing
and a e closu e. Ancien mining ac i i y in he Po uguese sec o o he Ibe ian Py i e
Bel (PIPB, SW o Eu ope) has led o se e al en i onmen al p oblems due o he exis ence
o e y ew (i any) measu es o manage and minimize en i onmen al o human heal h
isks [
2
,
3
]. In Po ugal, un il he XX h cen u y, he e was no legal obliga ion o ehabili a e
land a e he closu e o mines. Thus, in some small/medium abandoned mines, he
i s pos -closu e ac i i ies we e ocused on he dispe sion o mine was es wi h/wi hou
mixing wi h na u al soils. Some o hese a eas we e econ e ed o ag icul u e, pas o alism,
Plan s 2025,14, 60 h ps://doi.o g/10.3390/plan s14010060
Plan s 2025,14, 60 2 o 13
o es y, o a combina ion o hese (ag osil opas o al sys ems) by he local popula ion and
he na ional en i y esponsible o en i onmen al ehabili a ion (Exmin), as well as le o
na u al plan coloniza ion.
Independen ly o he high o al concen a ions o po en ially haza dous elemen s in
soils om PIPB mining a eas, he a ailable ac ion is usually low, allowing he de elopmen
o some plan species [
2
,
4
]. In ac , some abandoned mining a eas (e.g., mining a eas o Mn
and Fe oxides) ha e been classi ied as ha ing low/medium en i onmen al isk [
3
,
5
], and
no ob ious landscape-scale di e ences ha e been obse ed be ween he o me mining
in e en ion a ea and adjacen a eas.
Al hough he en i onmen al eco e y p ocesses associa ed wi h plan de elopmen
(na u al a enua ion and phy os abiliza ion) a e slow, especially in con amina ed a eas,
hese can con ibu e o imp o ing soil quali y [
6
,
7
] and minimizing land deg ada ion. The
imp o emen o soil quali y by plan s depends, o example, on he species, he s a a ype
(he baceous, sh ubs, and ees), he ype o oo sys em, and i s de elopmen . In addi ion,
ege a ion de elopmen can imp o e soil s uc u e and e ili y, p omo e biological ac i i y,
and inc ease wa e e en ion capaci y [8].
The ag osil opas o al sys em is a ype o land use ha combines pas u e o odde
p oduc ion wi h a woody componen o sh ubs and ees, wi h di e en li es ock com-
plemen ing each o he in he same a ea [
9
,
10
]. This in eg a ed sys em can con ibu e o
se e al en i onmen al bene i s and ecosys em se ices, such as educing soil deg ada ion
o e en imp o ing some soil p ope ies and inc easing C s ocks, hus ensu ing odde a ail-
abili y a leas du ing he ainy season [
9
–
11
]. Al hough he e ec o seasonali y is mo e
p onounced in d yland sys ems, he combina ion o legume and g ass species, pe ennial
and annual he baceous species, sh ubs, and ees p omo es complemen a i y, sus ainabili y,
and esilience o he sys em.
Acco ding o di e en cha ac e is ics o soils and in insic plan s, plan s g owing in
con amina ed soils may up ake and accumula e di e en le els o po en ially haza dous
elemen s in edible pa s [
12
,
13
]. This can lead o a po en ial isk o human and animal heal h
when he plan s a e consumed; he e o e, an assessmen o he elemen al composi ion o he
plan s is needed be o e making a decision on land use. In his sense, he bioaccumula ion
o elemen s in he soil–plan –animal sys em has been s udied by some au ho s [
14
–
18
]. The
aim o his s udy was o e alua e he gene al s a us and po en ial en i onmen al isk o
he soils and plan s (he baceous shoo s o he d yland pas u e and holm oak lea es) in
an ag osil opas o al sys em es ablished in a Fe-Mn mine om Po ugal a e long- e m
closu e (≈45 yea s ago).
2. Resul s and Discussion
This s udy p esen s a gene al e alua ion o he quali y o soils and plan s g owing
in an ag osil opas o al sys em es ablished
≈
45 yea s a e he closu e o he Fe agudo
mine (Figu e 1A,B). Soils om he holm oak a ea a e unde he in luence o he baceous
and ee hizosphe e sys ems and canopy, while soils om he pas u e a ea ha e only
he baceous oo s.
Independen ly o he a ea sampled (designa ed as holm oak o he baceous pas u e)
and dep h, he soils had neu al pH alues and a sligh ly acid eac ion, indica ed by he
pH in KCl, wi h low elec ical conduc i i y (Table 1) being conside ed non-saline soils.
These pa ame e alues coincide wi h e y low o al acidi y (Table 1), co esponding o
he concen a ion o Al and H
+
in he exchangeable complex o he colloidal ac ion. The
concen a ions o o ganic C and nu ien s (Table 1) showed some a iabili y. Thus, he
concen a ions o o ganic C and ex ac able P a ied om e y small (4.4 g C
o g
/kg and
<10 mg P/kg) o e y high (>60 g C
o g
/kg and >90 mg P/kg), while ex ac able K was
Plan s 2025,14, 60 3 o 13
mainly conside ed as high o e y high [
19
,
20
]. Ca ion exchange capaci y was conside ed
be ween medium o high (10–40 cmol
c
/kg [
15
]) and was co ela ed o o ganic C amoun s
(
≈0.8
,p< 0.05). The exchangeable complex was domina ed by Ca. In soils collec ed
unde holm oak ees, he concen a ions o o ganic C, N o al, and ex ac able K and P
dec eased signi ican ly wi h dep h (Table 1) because mos o he oo s a e loca ed be ween
10 and 20 cm dep h, and mos o he elemen up ake occu s.
Plan s 2025, 14, 60 3 o 13
<10 mg P/kg) o e y high (>60 g Co g/kg and >90 mg P/kg), while ex ac able K was
mainly conside ed as high o e y high [19,20]. Ca ion exchange capaci y was conside ed
be ween medium o high (10–40 cmolc/kg [15]) and was co ela ed o o ganic C amoun s
( ≈ 0.8, p < 0.05). The exchangeable complex was domina ed by Ca. In soils collec ed
unde holm oak ees, he concen a ions o o ganic C, N o al, and ex ac able K and P
dec eased significan ly wi h dep h (Table 1) because mos o he oo s a e loca ed be-
ween 10 and 20 cm dep h, and mos o he elemen up ake occu s.
Figu e 1. Ag osil opas o al sys em es ablished in Fe agudo mine a ea (A,B) and collec ion o soil
samples (C,D).
The s udied soils p esen ed highe e ili y, e alua ed by he concen a ions o o -
ganic C and NPK, han he Spolic Technosols collec ed in a simila mining a ea (Rosalga )
and he uncon amina ed soils o he egion, bo h na u ally colonized by au och honous
ege a ion [4,21]. This may indica e a di ec posi i e effec o soil managemen , possibly
wi h some e ilize applica ion o he whole su ace and/o he ag osil opas o al sys em
i sel . The imp o emen o soil e ili y in he ag osil opas o al sys ems due o he in-
c ease in nu ien s and o ganic ma e inpu s has been epo ed [22]. The soils unde he
holm oak canopy did no show a simila ichness in o ganic ma e and nu ien s as hose
ou side he canopy (Table 1), which is no usually obse ed [10,23]. In semi-na u al sys-
ems wi h holm oak (dehesa), he ee co e leads o an inc ease in soil e ili y due o he
A B
C D
Figu e 1. Ag osil opas o al sys em es ablished in Fe agudo mine a ea (A,B) and collec ion o soil
samples (C,D).
The s udied soils p esen ed highe e ili y, e alua ed by he concen a ions o o ganic
C and NPK, han he Spolic Technosols collec ed in a simila mining a ea (Rosalga )
and he uncon amina ed soils o he egion, bo h na u ally colonized by au och honous
ege a ion [
4
,
21
]. This may indica e a di ec posi i e e ec o soil managemen , possibly
wi h some e ilize applica ion o he whole su ace and/o he ag osil opas o al sys em
i sel . The imp o emen o soil e ili y in he ag osil opas o al sys ems due o he inc ease
in nu ien s and o ganic ma e inpu s has been epo ed [
22
]. The soils unde he holm oak
canopy did no show a simila ichness in o ganic ma e and nu ien s as hose ou side he
canopy (Table 1), which is no usually obse ed [
10
,
23
]. In semi-na u al sys ems wi h holm
oak (dehesa), he ee co e leads o an inc ease in soil e ili y due o he accumula ion o
some allen lea es and he educed decomposi ion o o ganic ma e in he shaded a ea
unde he ee c owns [10,11,23].
Plan s 2025,14, 60 4 o 13
In gene al, he e was no g ea he e ogenei y in he chemical cha ac e is ics o he soils
om holm oak and he baceous pas u e co e (Table 1), al hough alues ou side he main
ange we e ob ained o some samples (e.g., ex ac able K in a sample om he baceous
co e ; ex ac able P in a supe icial sample om holm oak; o al N in a sample om holm
oak a he second dep h). Al hough a a ia ion in soil pa icle size dis ibu ion associa ed
wi h he i egula disposal o mine was es (e.g., slags) was isually obse ed (Figu e 1C,D),
no he e ogenei y in soil chemical cha ac e is ics was ob ained. This small a ia ion in
he chemical cha ac e is ics can be ela ed o he con inuous soil managemen since he
mine closu e, which allowed he mixing o di e en mine ma e ials (e.g., slags and o he
mine was es, hos ocks) wi h na u al soil and he es ablishmen o a chemical equilib ium
o e ime.
Table 1. Physicochemical cha ac e is ics o he soils, collec ed unde he holm oaks canopy and
he baceous pas u es wi hou ee co e in he ag osil opas o al sys em es ablished in he Fe agudo
mining a ea a e closu e (minimum–maximum; mean
±
SD; n = 8). Fo each pa ame e , alues om
holm oak samples wi h an as e isk indica e signi ican di e ences be ween dep hs.
Holm Oak
0–10 cm
Holm Oak
10–20 cm
He baceous Pas u e
0–20 cm
pHH2O 6.4–7.2
6.8 ±0.3
6.2–6.9
6.6 ±0.3
5.7–6.8
6.4 ±0.4
pHKCl 5.3–6.8
5.9 ±0.5 *
4.5–5.7
5.1 ±0.5 *
4.7–6.0
5.5 ±0.4
EC 1(µS/cm) 109–360
211 ±76 *
40.1–174
83.8 ±45 *
114–221
152 ±38
O ganic C (g/kg) 28.2–89.1
45.1 ±20.1 *
4.4–28.2
12.9 ±7.5 *
20.4–87.9
42.4 ±23.0
To al N (g/kg) 2.2–4.8
3.0 ±0.9 *
0.3–2.7
1.2 ±0.7 *
1.4–5.0
2.9 ±1.2
Ex ac able K (mg/kg) 120–523
354 ±122 *
41.5–147
101 ±38 *
4.2–498
297 ±195
Ex ac able P (mg/kg) 8.3–69.9
34.3 ±17.4
1.2–91.7
37.0 ±29.9
13.2–101
50.9 ±42.6
CEC2and exchangeable ca ions (cmolc/kg)
CEC 217.5–49.0
29.2 ±9.4
8.9–25.4
18.3 ±6.2
14.6–30.2
24.0 ±5.7
Ca 10.9–44.1
21.2 ±10.5 *
3.2–15.6
10.3 ±5.1 *
12.8–20.4
17.2 ±3.2
Mg 3.7–8.6
6.8 ±1.8
4.2–9.1
7.1 ±1.9
0.3–9.5
5.7 ±3.1
Na 0.4–0.7
0.5 ±0.1
0.3–0.8
0.6 ±0.2
0.2–0.7
0.4 ±0.2
K0.3–0.9
0.6 ±0.2 *
0.1–0.3
0.2 ±0.1 *
0.3–0.9
0.6 ±0.2
To al acidi y 0.1–0.2
0.1 ±0.1
0.1–0.2
0.1 ±0.1
0.1–0.3
0.2 ±0.1
1Elec ical conduc i i y; 2ca ion exchange capaci y.
Soils om bo h plan sys ems had concen a ions o Cu, Mo, and Zn in he pseudo- o al
ac ion (Table 2) ha exceeded he e e ence alues p oposed by Po uguese legisla ion
o shallow soils and ag icul u al use (180 mg Cu/kg; 6.9 mg Mo/kg; 340 mg Zn/kg [
24
]).
Special a en ion should be paid o Mo, whose concen a ions we e 10 imes highe han he
e e ence alue. Fo B, only e y ew soil samples exceeded he e e ence alue indica ed
in he same legisla ion (120 mg/kg [
24
]). Mo eo e , he pseudo- o al concen a ions o Ca,
Cu, P, Mg, and Mn in he Fe agudo soils we e clea ly highe han hose ound in soils
Plan s 2025,14, 60 5 o 13
collec ed om a simila mining a ea in he Ce cal-Odemi a egion (Rosalga mine), whe e
he o ebody also comp ised ein s uc u es o Fe and Mn oxides, bu he a ea is domina ed
by na u al and au och honous ege a ion [
4
]. Concen a ions o Cu, Mn, and Zn we e also
highe han hose ound in uncon amina ed soils o he egion [
21
]. Concen a ions o Na
in he sampled soils we e somewha high.
Table 2. Pseudo- o al concen a ions o chemical elemen s in soils, collec ed unde holm oaks
canopy and he baceous pas u es wi hou ee co e in he ag osil opas o al sys em es ablished in he
Fe agudo mining a ea a e closu e (minimum–maximum; mean
±
SD; n = 8). Fo each elemen ,
alues om holm oak samples wi h an as e isk indica e signi ican di e ences be ween dep hs.
Elemen s Holm Oak
0–10 cm
Holm Oak
10–20 cm
He baceous Pas u e
0–20 cm
g/kg
Ca 4.2–14.3
7.1 ±3.2 *
0.8–5.9
3.9 ±1.8 *
3.2–7.1
5.7 ±1.4
K2.0–3.8
3.0 ±0.6 *
1.1–2.6
2.1 ±0.5 *
1.9–3.8
3.0 ±0.7
Mg 4.1–6.1
5.1 ±0.8
3.8–7.2
5.3 ±1.4
3.5–9.2
5.2 ±1.9
P0.5–1.2
0.7 ±0.2
0.3–1.2
0.6 ±0.3
0.5–1.3
0.8 ±0.3
S0.6–0.8
0.7 ±0.1 *
0.1–0.6
0.4 ±0.2 *
0.6–0.8
0.7 ±0.1
Fe 35.0–82.9
48.5 ±16.5
35.0–93.2
56.9 ±20.1
34.5–80.1
47.6 ±16.9
Mn 27.9–115
88.4 ±28.4
15.2–110
68.8 ±31.3
36.7–124
86.1 ±29.2
mg/kg
B66.4–149
91.6 ±28.9
59.1–157
101 ±32.6
59.5–141
88.7 ±29.4
Cu 121–462
302 ±106
124–572
315 ±179
106–446
246 ±116
Mo 35.7–126
92.9 ±27.3
8.2–127
73.3 ±40.9
21.9–177
87.4 ±47.7
Na 364–1730
1207 ±443
294–1421
861 ±374
372–2093
1132 ±576
Zn 162–734
433 ±168
189–941
497 ±276
157–982
409 ±266
Al hough he high concen a ions o some o hese elemen s in he pseudo- o al
ac ion can be associa ed wi h he mine was es inco po a ed in na u al soils (e.g., Mn and
Cu), amoun s o nu ien s such as Ca, P, and Mg (Table 2) can sugges he applica ion o
amendmen s o p omo e pas u e de elopmen . In ac , hese concen a ions, as well as he
con en s o exchangeable Ca and Mg, o al N, and ex ac able P de e mined in he s udied
soils (Table 1), we e much highe compa ed o hose in uncon amina ed soils om he
egion and no used o ag icul u al pu poses [21].
E en i he pseudo- o al concen a ions o he elemen s in he Fe agudo soils we e
high (Table 2), he soil a ailable ac ions o he same elemen s, co esponding o he
elemen s in soil solu ion and e ained in he exchangeable complex o colloidal ac ions,
we e gene ally low (<8.4% o he pseudo- o al concen a ions; Table 3). Excep ions we e
ob ained o Ca in all soils and Na in some soil samples unde oak ees (Ca 11–35%
and Na 9.7–22% o pseudo- o al concen a ions; Table 3). The a ailable ac ion o hese
elemen s, as well as Mg, was co ela ed wi h hei pseudo- o al concen a ions ( > 0.80, p
< 0.05). The a ailabili y o Ca in holm oak soils also seems o be ela ed o he o ganic C
con en (
≈
0.86, p< 0.05). Fo he o he elemen s, no co ela ions we e ound be ween

Plan s 2025,14, 60 6 o 13
he concen a ions in he soil a ailable ac ion and pH, o ganic C concen a ions, and
pseudo- o al concen a ions.
Table 3. Concen a ions o chemical elemen s in he a ailable ac ion o soils, collec ed unde
holm oaks canopy and he baceous pas u es wi hou ee co e , in he ag osil opas o al sys em
es ablished in he Fe agudo mining a ea a e closu e (minimum–maximum; mean
±
SD; n = 8).
Fo each elemen , alues om holm oak samples wi h an as e isk indica e signi ican di e ences
be ween dep hs.
Elemen s
mg/kg
Holm Oak
0–10 cm
Holm Oak
10–20 cm
He baceous Pas u e
0–20 cm
Ca 455–2025
1031 ±445 *
266–903
602 ±256 *
730–960
840 ±83.1
K15.8–54.9
34.0 ±12.8 *
8.9–46.9
18.4 ±13.09 *
8.4–73.2
44.0 ±22.7
Mg 268–430
370 ±65.5
266–431
352 ±66.5
204–478
326 ±86.8
P3.5–8.1
5.6 ±1.5
2.2–14.1
5.3 ±4.4
1.0–18.8
7.5 ±7.2
S12.1–19.3
16.1 ±2.4 *
6.3–15.0
10.1 ±3.0 *
10.1–16.7
12.4 ±2.1
Fe 6.7–37.2
17.2 ±11.4
7.5–136
41.6 ±44.2
3.6–57.2
18.0 ±18.8
Mn 25.9–554
398 ±169 *
493–791
619 ±103 *
297–573
442 ±93.5
B0.5–1.4
1.1 ±0.3 *
0.2–1.1
0.6 ±0.3 *
0.2–0.5
0.4 ±0.1
Cu 0.1–0.7
0.4 ±0.2 *
0.1–3.6
1.3 ±1.2 *
0.1–0.6
0.3 ±0.2
Na 64.4–142
92.6 ±23.6
43.1–140
101 ±34.6
30.5–150
66.8 ±40.5
Zn 0.2–3.6
1.9 ±1.0
0.8–5.1
3.0 ±1.4
0.9–4.4
2.0 ±1.3
In soils unde holm oak ees, he a ailable ac ion o K, S, and B dec eased signi i-
can ly wi h dep h (Table 3), simila o elemen s shown in Table 2, jus i ying he dec ease in
he EC in he same pa e n. Howe e , he concen a ions o Cu and Mn in he same ac ion
inc eased wi h dep h.
Dehyd ogenase ac i i y is an impo an indica o o he unc ionali y o he o e all
soil mic obial communi y, as i is an in acellula enzyme p esen in all li ing o ganisms
and o ganic ma e decomposi ion [
25
]. The s udy soils showed g ea he e ogenei y in
he dehyd ogenase ac i i y, independen ly o plan sys em and dep h (Table 4). In soils
unde holm oak ees, he enzyma ic ac i i y dec eased signi ican ly wi h he dep h. The
lowes dehyd ogenase ac i i y (0.2
µ
g TPF. g .16 h
−1
) was ob ained in a soil sample
collec ed be ween 10 and 20 cm dep h unde holm oak plan s, which also p esen ed
he lowes N concen a ion (0.3 g/kg). Al hough soil dep h may con ibu e o a dec ease in
dehyd ogenase ac i i y due o a possible dec ease in ae a ion, o he soil physicochemical
cha ac e is ics may in luence dehyd ogenase ac i i y [
26
]. In ac , he enzyma ic ac i i y in
soils unde holm oaks was ela ed o wo impo an nu ien s in he soil sys em, o al N
( ≈0.85
,p< 0.01) and a ailable S (
≈
0.93, p< 0.01), as well as o ganic C con en (
≈
0.79
p< 0.01).
Plan s 2025,14, 60 7 o 13
Table 4. Ac i i y o dehyd ogenase in soils collec ed unde holm oaks ees canopy and he baceous
pas u es wi hou ee co e in he ag osil opas o al sys em es ablished in he Fe agudo mining
a ea a e closu e (minimum–maximum; mean
±
SD; n = 8). Values om holm oak samples wi h an
as e isk indica e signi ican di e ences be ween dep hs.
µg TPF. g .16 h−1
Holm Oak
0–10 cm
Holm Oak
10–20 cm
He baceous Pas u e
0–20 cm
29.2–172
93.8 ±51.0 *
0.2–85.6
22.6 ±28.7 *
36.1–216
90.4 ±71.5
Dehyd ogenase ac i i ies in soils om he baceous oo sys ems (Table 4) we e in he
same ange as hose in he su ace laye o holm oak soils and also co ela ed wi h o al N
concen a ion in he soils ( = 0.89, p< 0.01).
The ag osil opas o al sys em included a low densi y o holm oak (Que cus ilex L.),
wi h good de elopmen and a con inuous he baceous co e o signi ican densi y. This
he baceous co e was mainly composed o species o he gene a T i olium,Silene,Plan ago,
An hemis,O ni hopus, and di e en species o he amily Poaceae. No isual di e ences
we e obse ed in he composi ion o he baceous di e si y and plan co e depending on
soil cha ac e is ics. A he landscape scale, he e we e some small a eas, andomly sca e ed,
wi h au och honous sh ub species belonging mainly o he genus Cis us. In gene al, no
signi ican changes we e obse ed in he landscape o he mine a ea, which is simila o he
adjacen a eas and o he ag osil opas o al sys ems in he egion.
Al hough he a ailabili y o elemen s in soil a ec s hei concen a ions in plan s,
o he p ocesses can occu in he soil-plan sys em (e.g., an agonism o syne gism be ween
elemen s, limi a ion o oo up ake, wa e a ailabili y, and plan species [
12
,
13
]). Mo eo e ,
in mode n pas u e sys ems, he elemen al composi ion o plan s, especially mac onu ien s,
can be mo e ela ed o e ilize applica ion [27] han o hei a ailabili y in he soil.
In he s udy a ea, independen ly o he concen a ion o he elemen s in he a ailable
ac ion o he soil, di e en accumula ion pa e ns we e ob ained acco ding o he elemen
and he plan sys em (Table 5). The shoo s om he he baceous pas u e showed he highes
concen a ions o elemen s, excep Mn, compa ed o he lea es o he holm oak. In ac ,
he accumula ion o elemen s in shoo s/lea es depends on he species, being a combined
esponse o he up ake and ansloca ion capaci y o he plan s and he concen a ion o
elemen s in he a ailable ac ion o he soil [
12
]. Mo eo e , o Mn, in e ac ions be ween
elemen s a he oo le el and an agonis ic eac ions wi h Cu, Zn, and/o Fe can occu [
13
].
Concen a ions o Cu, Fe, and Zn in bo h plan sys ems we e conside ed no mal o
su icien o plan s in gene al, while mos o he plan samples exceeded phy o oxic le els
(400 mg Mn/kg [
13
]) o Mn. Howe e , no isual signs o Mn phy o oxici y we e obse ed
(e.g., chlo osis and nec o ic pa s in old lea es, blackish-b own o ed nec o ic pa s, and
c ying lea ips [
13
]). In gene al, ees o he genus Que cus a e epo ed o be accumula o s
o Mn in lea es [
28
], al hough he speci ic concen a ion depends on he species and
eda oclima ic condi ions. In s udies ca ied ou on holm oaks g owing in na u al a eas
and u ban pa ks in he egions o Campania and Flo ence (I aly), Mn concen a ions in he
lea es we e lowe han hose ob ained in he p esen s udy [
29
,
30
]. The highe ole ance o
plan s o Mn in Fe agudo, since no isual phy o oxic signs we e obse ed, can be ela ed o
his plan popula ion. In ac , popula ions o se e al plan species (e.g., Cis us and La andula
genus) g owing in mining a eas o he Ibe ian Py i e Bel show highe concen a ions o
elemen s in plan issues compa ed o hose om uncon amina ed a eas, wi hou any
phy o oxic e ec , due o e icien ole ance and an ioxidan mechanisms [21,31–33].
Plan s 2025,14, 60 8 o 13
Table 5. Concen a ions o chemical elemen s in oak lea es and shoo s o he baceous pas u e collec ed
in he ag osil opas o al sys em es ablished in he Fe agudo mining a ea a e closu e (minimum–
maximum; mean
±
SD; n = 8). Values o he same elemen wi h an as e isk indica e signi ican
di e ences be ween plan s.
Elemen s Holm Oak Lea es He baceous Pas u e
g/kg
Ca 3.9–5.9
4.7 ±0.6 *
3.8–9.8
6.7 ±1.9 *
K4.2–6.8
5.3 ±0.9 *
13.5–24.0
20.0 ±0.4 *
Mg 1.4–1.9
1.6 ±0.2 *
2.4–4.0
3.3 ±0.5 *
N14.9–19.6
17.1 ±1.7 *
19.9–28.4
23.4 ±2.7 *
P1.0–1.5
1.3 ±0.2 *
2.5–4.0
3.4 ±0.6 *
mg/kg
Fe 149–251
183 ±33 *
154–767
384 ±222 *
Mn 197–2273
1429 ±677 *
197–755
469 ±197 *
Cu 8.2–20.5
11.7 ±4.4
7.6–14.0
10.6 ±2.2
Na 78.9–272
189 ±67.6 *
1611–7732
3892 ±1939 *
Zn 24.6–33.4
28.0 ±2.8 *
35.6–55.8
43.1 ±7.6 *
Al hough no s ong co ela ion be ween Mn concen a ion in he a ailable soil ac ion
(o pseudo- o al ac ion) and plan s was ob ained, i is e iden ha he a ailabili y o his
elemen in soil is high (Table 3) and should ha e some ela ionship wi h Mn plan amoun s.
Concen a ions o o he elemen s (N, P, K, Mg, Cu, Fe, and Zn) in holm oak lea es we e
in he same ange as hose collec ed in di e en loca ions, land uses, and soils ([
29
,
30
,
34
]
and e e ences he ein). Acco ding o he same au ho s, he N:P a io in lea es, conside ed a
use ul nu i ional indica o o plan s, is e y a iable. The alues calcula ed in he p esen
s udy a ied be ween 10 and 16, which a e in he same ange as hose epo ed by he
p e ious au ho s o he same species. Howe e , hese a ios may indica e N o P nu ien
limi a ion depending on he sample (in gene al, N:P < 14 indica es N limi a ion, and N:P
a io > 16 indica es P limi a ion [35]).
The s udied a ea is an ag osil opas o al sys em whe e he soils had inco po a ed
mine was es, so i is impo an o assess he isk o consump ion o he baceous ege a ion
by domes ic animals. Acco ding o Mine al Tole ances o Animals [
36
], he shoo s o
he he baceous pas u e g owing in some o he sampled a eas had concen a ions o Fe
(660.5 and 767.3 mg/kg) and K (21.1–24.0 g/kg) ha exceeded he maximum ole able
le els (MTL) based on indices o animal heal h o ca le and sheep (500 mg Fe/kg and
20 g K/kg
). Al hough he absolu e alues o hese samples may indica e some cau ion, he
mean alues o all he baceous pas u es sampled we e below (384 mg Fe/kg) o a he limi
(20 g K/kg) o he MTL. Fu he mo e, Fe and K a e elemen s ha a e conside ed o cause
mode a e ad e se e ec s in animals when o e ed o long pe iods o ime [
37
]. Thus, i
was conside ed ha he heal h conce n may also be low due o he exis ence o dilu ion
ac o wi h shoo s consumed in adjacen a eas and o he ood sou ces p o ided o he
animals. In ac , he die o ca le is no limi ed o he baceous ma e ial om he s udy a ea.
Being a d yland pas u e, he amoun o pas u e p oduced is no su icien a any ime o
he yea , and a me s need o buy pas u e o silage om o he o igins.
Plan s 2025,14, 60 9 o 13
Mo eo e , i is epo ed by [
36
] ha K and Fe concen a ions in some o ages can each
highe alues (>50 g K/kg and 700–800 mg Fe/kg). Simila o he o he ypes o plan s,
elemen concen a ions in o ages can a y wi h species and a ie y, g ow h s age, c op
managemen p ac ices, and seasons [
12
,
27
,
38
,
39
]. The e o e, he isk o consump ion by
domes ic animals can be conside ed low. Simila esul s ha e been ob ained in pas u es
g own on eco e ed mining was es om high moun ain a eas [40].
3. Ma e ials and Me hods
3.1. Si e Desc ip ion
Fe agudo is an abandoned mine (
≈
38 ha) loca ed in he Beja dis ic (37
◦
38
′
9
′′
no h,
8
◦
3
′
58
′′
wes ), which is pa o he Po uguese sec o o he Ibe ian Py i e Bel [
3
]. The
o ebody, which o ms s a i o m and ein s uc u es (small o medium dimension), consis s
o Fe and Mn oxides (py olusi e) and Mn ca bona es ( hodoch osi e and hodoni e) and
was in ensi ely exploi ed in he o ies and i ies o he wen ie h-cen u y, bo h in wells and
galle ies up o 40 m dep h and in open pi . The exploi a ion o he o ebody began in 1875
and ended in 1970, mainly due o he closu e o he o e p ocessing company. The Mn-oxides
and ca bona es p oduced concen a es wi h 50 and 38–48% Mn, espec i ely [41,42].
The en i onmen al haza d impac o he Fe agudo mining a ea was conside ed
in e media e (le el h ee, whe e le el i e is conside ed wi h ex eme impac ) due o he
small olume o mine was es wi h ela i ely low o al concen a ions o po en ially oxic
elemen s, excep o Mn [
3
]. A e he closu e, he in e en ions in he a ea esul ing
om he mining ac i i y led o he sp ead o mine was es o e he opog aphic su ace,
which con ibu ed o he al e a ion o pedogenesis p ocesses in soils de eloped on di e en
ma e ials, depending on he a ea (e.g., mine was es o a mix u e o mine was es, hos
ocks, and na u al o me soils), and sowing o he baceous plan s. The land use o he a ea
included g azing and o es y [3].
In ecen decades, Fe agudo mining a ea has been an ag osil opas o al sys em ex en-
si ely managed, which includes holm oak (Que cus ilex L.), wi h low densi y, spaced by a
homogeneous and dense co e age o a biodi e se pas u e composed mainly o species om
amilies Poaceae and As e aceae (Figu e 1A,B). Al hough some spon aneous species can ex-
is in he pas u e land, mos o hem we e sown. In e y limi ed a eas, especially wi h high
s oniness, he e a e pa ches o au och honous sh ubs wi h Cis us and La andula species.
Soils om some a eas wi hin he s udy a ea a e classi ied as Spolic Technosols [
43
]. The
na u al soils in he a ea adjacen o he mine a e classi ied as Lep osols ([
43
], co esponding
o “Li ossolos” in he Po uguese soil classi ica ion [44]).
Acco ding o he Köppen classi ica ion, he egion has a Medi e anean clima e (Csa),
wi h ho (a e age 23
◦
C) and d y summe s ( he d ies mon h wi h an a e age o 3 mm
ain all) and mode a ely cold (a e age 10.8
◦
C) and we win e s. The annual ain all
(a e age 572 mm) occu s mos ly in win e wi h an i egula pa e n (Clima ogical no mal
1971–2000, Beja s a ion [45]).
3.2. Sample Collec ion and Analysis
Due o he unclea de ini ion o he bounda ies o he old mining a ea, he p esen
s udy selec ed wo zones a ound he all open-pi whe e he con amina ion le el may be
highe . The zones we e pas u e a ound holm oaks whe e he e was a s ong in luence
o ee canopy and oo s (he ea e e e ed o as holm oak a ea) and he baceous pas u e
wi hou ee co e whe e he e was no in luence o holm oaks (he ea e e e ed o as
pas u e a ea). Eigh plo s we e selec ed in each zone (n = 16 plo s in he o al s udy a ea).
In he sp ing, composi e soil samples (composed o i e subsamples; Figu e 1C,D) and he
co esponding plan samples we e collec ed in each plo .