Impact of declining atmospheric deposition on forest soil solution chemistry in Flanders, Belgium
Arne Verstraeten
15th Meeting of the ICP Forests Expert Panel on Deposition, 10–11 April 2013, Ljubljana, Slovenia
I will present :
• National deposition and soil solution trends for Flanders forests (1994-2010) (Verstraeten et al., 2012)
• Some results for soil solution DOC (2002-2012)- trends- seasonality- role of DOC depositionongoing analysis for national data
1. Deposition and soil solution trends
Objectives:•Trend analysis for stand deposition of N, S and base cations (Ca, K, Mg)•Trend analysis for soil solution fluxes of N, S, base cations (Ca, K, Mg) and Altot
•Make an ion budget for N and S•Discuss the results in relation to critical loads and levels
Study area
Data from 5 ICP Forests Level II plots were selected:- 2 coniferous- 3 deciduous
Plot Coordinates Elevation Temperature Precipitation Tree species Age Former land use Basal area Throughfall Stemflow
N E m °C mm years m²/ha % %
Coniferous forests
RAV 51°24'07'
'
05°03'15'
'
35 10.4 887 Pinus nigra subsp. laricio 80 heath 44.9 68.3 -
BRA 51°18'28'
'
04°31'11'
'
14 10.8 882 Pinus sylvestris 81 heath 29.2 78.6 -
Deciduous forests
WIJ 51°04'11'
'
03°02'14'
'
31 11.0 867 Fagus sylvatica 75 arable 36.5 62.0 14.7
GON 50°58'31'
'
03°48'15'
'
26 10.6 786 Quercus robur, Fagus sylvatica 92 old growth 31.9 71.8 3.2
HOE 50°44'45'
'
04°24'47'
'
129 10.7 854 Fagus sylvatica 101 old growth 28.9 70.9 5.8
Sample collection
• 2 times per month• 10 throughfall collectors• 5 stemflow collectors (beech)• lysimeters for soil solution:
- organic layer (zero-tension)- topsoil- subsoil- deeper mineral soil
3 locations, 2-3 collectors per depth
Throughfall collectors
10 m
Chemical analysis
• on 500 ml composite subsamples of each fraction
• pH en conductivity
• concentrations of cations (Ca2+, K+, Mg2+, Na+, NH4+) and anions
(Cl-, SO42-, NO3
-) with ion chromatography
• Altot concentration with emission spectrometry
Data handling
• stand deposition = throughfall + stemflow• soil water fluxes were calculated using Na+ as a “tracer ion”
for each soil depth• trend analysis: Seasonal Mann-Kendall trend test (Hirsch &
Slack, 1984)• cross-site statistics: ANOVA/Tukey’s range test
Results
Deposition trends (1994-2010)
Plot Stand
precipitation
NH4+ NO3
- NH4+/NO3
- ratio
mean slope mean slope change mean slope change mean slope change
Coniferous forests
RAV 636 a ns 1901 d -69*** -45 645 b ns 2.96 c -0.09*** -37
BRA 784 b ns 1576 c -49*** -40 709 b ns 2.24 b -0.05*** -32
Deciduous forests
WIJ 712 ab ns 1370 bc -72*** -57 519 a -7* -17 2.67 bc -0.09*** -39
GON 657 a ns 1155 b -49*** -50 529 a -9* -24 2.18 b -0.06*** -31
HOE 743 b ns 806 a -42*** -59 521 a -12*** -30 1.53 a -0.05*** -38
Stable40-59%
decline of NH4
+
17-30% decline of NO3
- only in deciduous
stands
Decline of NH4
+/NO3- ratio
from 2.44 to 1.90
56-68% decline of
SO42-
19-41%decline of
base cations
45-74%decline of
potentially acidifying deposition
Plot SO42- BC (Ca2+ + K+ + Mg2+) Potentially acidifying
mean slope change mean slope change mean slope change
Coniferous forests
RAV 1229 bc -63*** -56 733 a -11* -23 2995 d -127*** -50
BRA 1380 c -70*** -59 966 b -25*** -35 2593 c -93*** -45
Deciduous forests
WIJ 1021 ab -59*** -64 1209 bc -19* -22 1763 b -120*** -71
GON 1212 bc -62*** -58 1741 d -23** -19 1198 a -84*** -72
HOE 869 a -53*** -68 1400 c -47*** -41 816 a -56*** -74
Deposition trends (1994-2010)
Annual deposition
Results
Soil solution trends (1994-2010)
Decline through nearly the entire soil
profile
Plot Period SO42-
mean slope change
Organic layer
RAV 1994-2010 997 ab -36*** -44
BRA 1994-2010 1383 c -64*** -54
WIJ 2003-2010 861 a -53** -36
GON 1994-2010 1268 bc -26* -29
HOE 1994-2010 881 a -21* -32
Topsoil
RAV 1997-2010 1111 a -67*** -54
BRA 2002-2010 1127 ab -47* -26
WIJ 2002-2010 914 a -61** -43
GON 1996-2010 1492 b -77*** -46
HOE 2001-2010 779 a -74*** -54
Subsoil
RAV 2002-2010 874 a ns
BRA 1994-2010 1487 b -76*** -51
WIJ 1998-2010 1105 a -59*** -46
GON 1999-2010 1198 ab ns
HOE 1998-2010 954 a -62*** -50
Deeper mineral soil
RAV 1994-2010 1353 ab ns
BRA 1997-2010 1683 b -82*** -43
WIJ 2002-2010 1178 a -69** -37
GON 1994-2010 1389 ab -71*** -55
HOE 1996-2010 1091 a -60*** -51
SO42-
NH4+
-restricted to the organic layer (nitrification)-only decline in BRA
NH4+ and NO3
-
Plot Period NH4+ NO3
-
mean slope change mean slope change
Organic layer
RAV 1994-2010 709 a ns 1113 ab ns
BRA 1994-2010 722 ab -64*** -88 791 a ns
WIJ 2003-2010 379 c ns 2590 c -192* -41
GON 1994-2010 495 bc ns 1852 d ns
HOE 1994-2010 352 c ns 1373 b -30* -31
Topsoil
RAV 1997-2010 88 a ns 1631 b -89** -51
BRA 2002-2010 10 a ns 949 a ns
WIJ 2002-2010 7 a ns 756 a -160*** -89
GON 1996-2010 30 a +1** +256 2302 c ns
HOE 2001-2010 6 a ns 676 a -104*** -73
Subsoil
RAV 2002-2010 10 a ns 1291 ac -141** -56
BRA 1994-2010 132 b -1** -6 1570 bc -130*** -71
WIJ 1998-2010 9 a ns 1098 ab -167*** -81
GON 1999-2010 10 a +1*** +48 1928 c ns
HOE 1998-2010 33 a ns 615 a -44*** -51
Deeper mineral soil
RAV 1994-2010 4 a ns 1365 b -51* -47
BRA 1997-2010 3 a ns 1120 b -104*** -71
WIJ 2002-2010 1 a -0.2* -56 351 a -64*** -62
GON 1994-2010 6 a ns 1321 b -84*** -63
HOE 1996-2010 3 a ns 504 a -28*** -47
NO3-
-decline through nearly the entire soil profile
Soil solution trends (1994-2010)
Decline in the mineral soil
BC (Ca + K + Mg)
Plot Period BC
mean slope change
Organic layer
RAV 1994-2010 1477 a ns
BRA 1994-2010 1440 a ns
WIJ 2003-2010 2979 b ns
GON 1994-2010 3244 b ns
HOE 1994-2010 2806 b ns
Topsoil
RAV 1997-2010 887 a -80*** -64
BRA 2002-2010 720 a -52* -44
WIJ 2002-2010 828 a ns
GON 1996-2010 3017 b -89*** -33
HOE 2001-2010 1198 a -205*** -83
Subsoil
RAV 2002-2010 372 a -34** -46
BRA 1994-2010 953 b -61*** -64
WIJ 1998-2010 788 ab -105*** -73
GON 1999-2010 2310 c -94** -36
HOE 1998-2010 1202 b -144*** -73
Deeper mineral soil
RAV 1994-2010 480 a -29*** -57
BRA 1997-2010 738 a -68*** -64
WIJ 2002-2010 466 a -47*** -55
GON 1994-2010 2009 c -104*** -54
HOE 1996-2010 1225 b -89*** -64
Soil solution trends (1994-2010)
Decline in the mineral soil
Altot
Plot Period Al
mean slope change
Organic layer
RAV 1994-2010
BRA 1994-2010
WIJ 2003-2010
GON 1994-2010
HOE 1994-2010
Topsoil
RAV 1997-2010 1811 b ns
BRA 2002-2010 1006 a -135*** -60
WIJ 2002-2010 786 a -76** -55
GON 1996-2010 982 a -34* -36
HOE 2001-2010 590 a -46** -56
Subsoil
RAV 2002-2010 2615 d ns
BRA 1994-2010 1398 bc -83*** -61
WIJ 1998-2010 1872 c -140*** -58
GON 1999-2010 961 ab ns
HOE 1998-2010 550 a ns
Deeper mineral soil
RAV 1994-2010 2999 d ns
BRA 1997-2010 2165 c -151*** -60
WIJ 2002-2010 1395 b -118*** -49
GON 1994-2010 899 ab -67*** -71
HOE 1996-2010 492 a -15* -30
Soil solution trends (1994-2010)
Ion budget for SO42-, NO3
- en NH4+
• For each depth soil solution fluxes of N and S (output) were compared to stand depositions (input)
• Ratio: output/input*100 • Differences between input and output were tested with a
paired t-test
Results
Plot Period Organic layer Topsoil Subsoil Deeper mineral soil
SO42- NH4
+ + NO3- SO4
2- NH4+ + NO3
- SO42- NH4
+ + NO3- SO4
2- NH4+ + NO3
-
Coniferous forests
RAV 2002-2010 80(198***) 84(335ns) 93(75*) 67(727**) 84(165***) 57(943**) 124(184ns) 58(882**)
BRA 2002-2010 82(231***) 60(827***) 89(130ns) 47(1103**) 84(207**) 48(1076***) 108(99ns) 41(1214***)
Deciduous forests
WIJ 2003-2010 96(33ns) 199(1505**) 101(19ns) 45(784**) 104(46ns) 27(1066***) 129(263**) 16(1220***)
GON 1999-2010 101(21ns) 146(672***) 108(73ns) 168(924**) 104(24ns) 129(397ns) 102(4ns) 76(376*)
HOE 2001-2010 112(52ns) 142(509**) 100(5ns) 54(454*) 112(76*) 46(573***) 127(179***) 37(640***)
1 • Organic layer of coniferous forest accumulates N, while net losses
were observed in deciduous forests, reflecting differences in litter decomposition rate.
• Highest NO3- leaching was observed in a deciduous plot (GON,
76% of input)
• SO42- leaching >> inputs, indicating SO4
2- desorption delays recovery
Ion budget for SO42-, NO3
- en NH4+
Critical load for lichens in temperate forests: 3.1 kg N ha-1y-1 (Fenn et al., 2008)In 2010 depositions in the 5 plots were still 4-8 times higher
Lichens
Ground vegetation
Critical load for ground vegetation in temperate forests: 10-15 kg N ha-1y-1 (UNECE, 2007).In 2010 only respected in the organic layer of 1 plot, and exceeded with 22-69% elsewhere
Critical loads
increase, but still <0,
except in the organic layer of 1 plot
1) Acid Neutralizing Capacity (ANC)
Plot Period ANC
mean slope
Organic layer
RAV 1994-2010 -1474 a ns
BRA 1994-2010 -1508 a +110***
WIJ 2003-2010 -1158 ab +189**
GON 1994-2010 -573 b ns
HOE 1994-2010 +113 c +43**
Topsoil
RAV 1997-2010 -2020 a ns
BRA 2002-2010 -1548 ab +92*
WIJ 2002-2010 -1105 bc +161***
GON 1996-2010 -901 c ns
HOE 2001-2010 -321 d +24*
Subsoil
RAV 2002-2010 -1874 a +158**
BRA 1994-2010 -2205 a +173***
WIJ 1998-2010 -1580 a +128***
GON 1999-2010 -902 c ns
HOE 1998-2010 -445 c ns
Deeper mineral soil
RAV 1994-2010 -2465 a ns
BRA 1997-2010 -2126 a +133***
WIJ 2002-2010 -1319 b +115***
GON 1994-2010 -821 bc ns
HOE 1996-2010 -433 c +18*
(ANC = Ca2+ + K+ + Mg2+ + Na+ – Cl- – SO42- – NO3
-)
Critical limits
Acidification continues…
Decline of BC/Al ratio at most plots
2) BC/Al ratio
Plot Period BC/Al ratio
mean slope change
Organic layer
RAV 1994-2010
BRA 1994-2010
WIJ 2003-2010
GON 1994-2010
HOE 1994-2010
Topsoil
RAV 1997-2010 0.49 b -0.04*** -59
BRA 2002-2010 0.84 ab +0.07* +81
WIJ 2002-2010 1.05 ab -0.05* -29
GON 1996-2010 3.15 c ns
HOE 2001-2010 1.99 a -0.19*** -60
Subsoil
RAV 2002-2010 0.14 a -0.01*** -64
BRA 1994-2010 0.71 a ns
WIJ 1998-2010 0.37 a -0.03*** -65
GON 1999-2010 2.45 b -0.10*** -36
HOE 1998-2010 2.43 b -0.27*** -63
Deeper mineral soil
RAV 1994-2010 0.15 a -0.01*** -56
BRA 1997-2010 0.35 a -0.02*** -44
WIJ 2002-2010 0.33 a -0.01** -23
GON 1994-2010 2.33 b +0.05** +38
HOE 1996-2010 2.52 b -0.11** -45
(BC/Al = Ca2+ + K+ + Mg2+ / Altot)
Critical limits
Critical limit for root damage / growth reduction
Pinus: BC/Al<1.2exceeded at both locations.
Quercus/Fagus: BC/Al<0.6 exceeded in the mineral soil of 1 plot.
• Potentially acidifying depositions declined substantially in the 5 plots between 1994 and 2010
• Forest soils continue to acidify• Recovery is delayed by simultaneous decline of base cation
depositions and long-term buffer processes in the soil (e.g. SO4
2- desorption)
Conclusions
2. Dissolved Organic Carbon (DOC)
Ongoing analysis for national data
• 5 Level II plots• trends / seasonal patterns soil solution DOC (2002-2012)• role of DOC delivered by deposition
DOC concentrations (mg l-1)
2002 2004 2006 2008 2010 20120
1
2
3
4
5
6
Me
an
an
nu
al c
on
cen
tra
tion
of D
OC
(m
g l-1
)
RAVBRAWIJGONHOEmean
a
2002 2004 2006 2008 2010 20120
10
20
30
40
50
60
b
2002 2004 2006 2008 2010 20120
10
20
30
40
50
60
d
2002 2004 2006 2008 2010 20120
10
20
30
40
50
60
e
2002 2004 2006 2008 2010 20120
10
20
30
40
50
60
f
• increased nearly through the whole soil profile• increased in precipitation (open field)• remained stable in stand precipitation
2002 2004 2006 2008 2010 20120
10
20
30
40
50
60
c
DOC fluxes (kg ha-1 y-1)
• soil solution fluxes showed few significant changes• precipitation fluxes increased• stand deposition fluxes remained stable
2002 2004 2006 2008 2010 20120
10
20
30
40RAVBRAWIJGONHOEmean
Ye
arl
y flu
x o
f DO
C (
kg h
a-1
y-1
)
a
2002 2004 2006 2008 2010 20120
40
80
120
b
2002 2004 2006 2008 2010 20120
100
200
300
c
2002 2004 2006 2008 2010 20120
100
200
300
d
2002 2004 2006 2008 2010 20120
100
200
300
e
2002 2004 2006 2008 2010 20120
100
200
300
f
Coniferous forest plots showed higher carbon losses (51–56 kg ha-1 y-1) than deciduous forest plots (19–30 kg ha-1 y-1)
TrendsPlot Depth (cm) Water fluxes DOC concentrations DOC fluxes Mean Slope Mean Slope Mean Slope Precipitation RAV 923a 2.2a +0.1*** 20.2a +0.8* BRA 960a 2.4a +0.1* 19.0a WIJ 929a 2.2a +0.1** 19.0a +0.7* GON 838a 2.0a +0.1*** 15.0a +0.6* HOE 971a 1.9a +0.1*** 17.0a +0.8** Stand precipitation RAV 649ab 17.5a 106.2a BRA 770a 14.9a 102.8a WIJ 718ab 7.9c 49.0b GON 621b 11.2b 60.0b HOE 766a 7.8c 49.6b Organic layer
RAV 490b 42.8 a +0.9* 213.5a BRA 560a 35.0 b +1.8*** 199.2a WIJ 633a 27.8 c +1.2** 177.3a +17.8* GON 420b 35.4 b +0.8* 149.5a HOE 548ab 33.6 b 184.5a Topsoil
RAV 10-25 374a 46.0 a +1.2*** 173.7a BRA 15-25 323a 38.1 b +1.1*** 120.4b WIJ 10-20 330a 34.8 b +1.5*** 114.7bc GON 10-20 326a 25.8 c +0.5* 83.7c HOE 10-15 400a -13.3* 22.6 c +0.8*** 89.7bc Subsoil
RAV 30-45 278b 42.3 a 117.2a +4.5* BRA 30-55 258b 30.8 b 79.5b WIJ 45-70 230b 19.2 c +0.6*** 44.2c GON 25-40 314ab 19.0 c +0.5** 59.3bc HOE 20-30 366a 7.9 d +0.6*** 28.7c Deeper mineral soil RAV 70-95 260b 20.5 a 50.6a BRA 70-90 272ab 21.0 a +0.8*** 55.5a WIJ 75-110 185b 10.4 c +0.4*** 19.1b GON 45-55 212b 13.2 b +0.5*** 27.5b HOE 35-55 363a 8.3 d +0.7*** 29.8b +2.4**
Coniferous forest plots showed higher carbon losses (51–56 kg ha-1 y-1) than deciduous forest plots (19–30 kg ha-1 y-1)
Seasonal patterns – depositions vs. soil solution concentrations
• characteristic peak for soil solution near end of growing season• preceded by a peak of deposition fluxes during summer
1 2 3 4 5 6 7 8 9 10 11 12Month
0
1
2
3
4
Me
an
mon
thly
DO
C d
ep
osi
tion
(kg
ha
-1)
RAVBRAWIJGONHOEmean
a
1 2 3 4 5 6 7 8 9 10 11 120
4
8
12
16b
1 2 3 4 5 6 7 8 9 10 11 120
10
20
30
40
50
60
70 c
Me
an
mo
nth
ly D
OC
co
nce
ntr
atio
n (
mg
l-1)
1 2 3 4 5 6 7 8 9 10 11 120
10
20
30
40
50
60
70 d
1 2 3 4 5 6 7 8 9 10 11 120
10
20
30
40
50
60
70 e
1 2 3 4 5 6 7 8 9 10 11 120
10
20
30
40
50
60
70 f
Correlation between DOC fluxes (Spearman)
• mean annual soil solution fluxes and deposition fluxes of DOC were correlated, except in the mineral topsoil
Stand precipitation Organic layer Topsoil Subsoil Deeper mineral soil
Rainfall 0.684*** 0.731*** 0.204 0.795*** 0.280* Stand precipitation
0.490*** 0.120 0.604*** 0.491***
Organic layer
0.251 0.670*** 0.263 Topsoil
0.234 0.300*
Subsoil
0.385**
Soil solution vs. deposition fluxes of DOC
• ± linear relationship between deposition of DOC and soil solution flux of DOC
• may reflect difference in forest type or acid deposition load ?
0 50 100 150 200 2500
50
100
150
200
250
RAVa
BRAHOE
WIJ
GON
0 50 100 150 200 2500
50
100
150
200
250
RAV
BRA
HOE
WIJ
GON
b
0 50 100 150 200 2500
50
100
150
200
250
RAV
c
BRA
HOE
WIJ
GON
0 50 100 150 200 2500
50
100
150
200
250
RAV
d
BRA
HOE
WIJGON
Fluxes of DOC in relation to organic layer DOC flux (100%)
• stand deposition delivered 50-52% and 27-40% of organic layer DOC flux in coniferous and deciduous forest stands respectively
• may reflect difference in forest type or acid deposition load ?
Conclusions
• soil solution DOC concentrations increased (2002-2012)
• soil solution DOC fluxes showed less marked trends (due to variation in annual precipitation surplus?)
• coniferous forest plots showed higher carbon losses (51–56 kg ha-1 y-1) than deciduous forest plots (19–30 kg ha-1 y-1)
• concentrations and fluxes of DOC decreased from the organic layer towards the deeper mineral soil, but in plots on poor sandy soils DOC concentrations were highest in the topsoil
• soil solution DOC concentrations and fluxes seem to be strongly influenced by stand depositions of DOC:
1. mean annual soil solution fluxes and deposition fluxes of DOC were correlated, except in the mineral topsoil
2. stand deposition delivered 50-52% and 27-40% of organic layer DOC flux in coniferous and deciduous forest stands respectively
3. seasonal patterns of deposition and soil solution DOC were related, with the peak of soil solution concentrations near the end of the growing season (August–November) being preceded by a peak of DOC depositions (May–August)
Any questions / remarks ?
Thanks for your attention !
2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012
Year
0
200
400
600
800
1000
1200
mm
RainfallStand precipitationOrganic layerTopsoilSubsoilDeeper mineral soil
Annual water fluxes
Jaarlijkse bodemwaterfluxen in de 5 proefvlakken in de humuslaag
Jaarlijkse bodemwaterfluxen in de 5 proefvlakken in de topsoil (A-horizont)
Jaarlijkse bodemwaterfluxen in de 5 proefvlakken in de subsoil (B-horizont)
Jaarlijkse bodemwaterfluxen in de 5 proefvlakken in de deeper mineral soil (C-horizont)