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)