Controls of dissolved inorganic and organic carbon discharge from permafrost ecosystems

Prokushkin Anatoly S.

V.N. Sukachev Institute of Forest SB RAS, Krasnoyarsk Siberian Federal University [email protected]

ИЛ СО РАН: School of the young scientists on Biogeochemical 1 Matter Cycling In Permafrost Ecosystems Presentation structure:

• Terms • Processes

• Dissolved carbon in watersheds of Siberian rivers : interactions of hydrology, vegetation, permafrost, fires and C fluxes

2 • from Latin dissolvere : dis- + solvere, to release Physicochemical background: Wikipedia: Dissolution is the process by which a solute forms a solution in a solvent. The solute, in the case of solids, has its crystalline structure disintegrated as separate ions, atoms, and molecules form. For liquids and gases, the molecules must be adaptable with those of the solvent for a solution to form. The outcome of the process of dissolution (the amount dissolved at equilibrium, i.e., the solubility) is governed by the thermodynamic energies involved, such as the heat of solution and entropy of solution, but the dissolution itself (a kinetic process) is not. Overall the free energy must be negative for net dissolution to occur. In turn, those energies are controlled by the way in which different chemical bond types interact with those in the solvent.

3 Dissolved carbon species:

• Dissolved inorganic carbon [CO2*] + [HCO3−] + [CO32−] • Dissolved organic carbon Complex mixture of organic volecules • Dissolved gases CO2, CH4

Other portion of C in waters is called particulate C: Particulate organic C

Particulate inorganic C 4 Dissolved carbon: definitions and species Initially in hydrochemistry dissolved matter is operationally defined as matter which is passed through 0.45 um pore-size filter Wikipedia: …The "dissolved" fraction of organic carbon is an operational classification. Many researchers use the term "dissolved" for compounds below 0.45 micrometers, but 0.22 micrometers is also common... A practical definition of dissolved typically used in marine chemistry is all substances that pass through a GF/F filter (0.7 um pore size!). So, to work with dissolved carbon in a sample one need first to filter sample! 5 Advantages and disadvantages of filters:

• 0.22 micrometers: to get rid of microbes… less loss during storage, but may contaminate with C (nitrocellulose, acetate cellulose matrix)

• 0.7 um precombusted glass fiber filters (GF/F): miserable or no contamination by OC, but microbes…

6 How to measure?

• DOC (TOC = TC-IC, NPOC – nonpurgeable OC) - The recommended measure technique is the high temperature catalytic oxidation (IR detection)

- Previous technique (still in use by Roshydromet) Bichromate/permanganate oxidation

7 How to measure? • DIC - The recommended measure technique is acidification with further IR detection

- Potentiometric titration with HCl for alkalinity

+ - H + HCO3 = H2CO3 = H2O + CO2

8 Why it is important?

• DOC loss from terrestrial ecosystems to fresh waters constitutes 1-15% of NEP • DIC and specifically dissolved CO2/CH4 fluxes is not still well counted … • C exported from terrestrial ecosystems to rivers are rarely included in NEP estimates, causing its underestimation • DOM (DOC, DON, DOP etc…) is important driver of foodwebs in both terrestrial and aquatic systems

9 Dissolved organic C

• To be microbially mineralized to CO2/CH4 all organic matter must be dissolved

10 Dissolved inorganic C

Carbonate weathering… H2CO3 + CaCO3 → Ca(HCO3)2

Silicate weathering… 2 KAlSi3O8 + 2 H2CO3 + 9 H2O ⇌ Al2Si2O5(OH)4 + 4 H4SiO4 + 2 K+ + 2 HCO3− Temperature dependent process 11 high potential for sequestration of atmospheric CO2… • Weathering of basalts of may be important factor for atmospheric CO2 sequestration

Illustration of the correlations between weathering fluxes and (A) thermal regimes and (B) hydrological regimes for 22 representative silicate sites around the world (excerpt from Beaulieu et al., 2010).

Our study shows clear increase of DIC annual yield from 1.04 gC m−2 yr−1 for Tembenchi River (MAAT = −10.9 ◦C) to 2.77 gC m−2 yr−1 for River (MAAT = −7.5 ◦C).

The other basaltic boreal rivers such as Kamchatka River and its tributaries (MAAT = −2.5 ◦C) exhibit significantly higher annual fluxes of DIC: 4.8 gC m−2 yr−1 12 Dissolved organic C: dissolved or colloidal? 8000

7000 450 6000 400 5000 350 4000 300

[Na], ppb [Na], 3000 250 LMW = 1 kDa 2000

[Fe], ppb [Fe], 200 150 (Dialysis) 1000 0 100 18.0 20 um 10 um 5 um 1.2 um 0.22 um 1 kDa 50 LMW 16.0 HMW Pore diamter 0 14.0 20 um 10 um 5 um 1.2 um 0.22 um 1 kDa 700 Pore diamter 12.0 600 300 10.0 8.0 500 250 NPOC [mgC/l]NPOC 6.0 400

200 4.0 [K], ppb [K], 300 2.0 150 200

[Al], ppb [Al], 0.0 100 100 December March April May June July September Month 0 50 20 um 10 um 5 um 1.2 um 0.22 um 1 kDa Pore diamter 30 0 LMW 20 um 10 um 5 um 1.2 um 0.22 um 1 kDa Pore diamter 25 HMW 12000

0.025 20 10000 15 0.02 8000

10 6000 0.015

[Ca], ppb [Ca], NPOC [mgC/L] NPOC 5 4000 [Tb], ppb [Tb], 0.01 0 2000 07.06.2013 07.06.2013 20.06.2013 20.06.2013 05.08.2013 05.08.2013 0.005 NT KO NT KO NT KO 0 20 um 10 um 5 um 1.2 um 0.22 um 1 kDa River/sampling date 0 Pore diamter 20 um 10 um 5 um 1.2 um 0.22 um 1 kDa 13 Pore diamter What is DOC? How to investigate the composition?

• Complex mixture of organic molecules • Fulvic acids (dissolved at pH 2) • Hydrophobic acid (by XAD fractionation)

• Spectral characteristics (e.g. SUVA, spectral slope) • Fluorescence (chromatophoric groups) • Biomarkers (e.g. lignin, sugars etc.) • Isotopic composition (i.e. 13C) • Radiocarbon age (compound specific) • Pyr-GC/MS-IRMS, 13C NMR CP MAS, electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI- FT-ICR-MS) • etc. 14 Dissolved organic carbon in terrestrial systems

Rainfall 0.9-4.5 mgC/l (< 0.5 gC/m2/a)

Throughfall/stemflow 0

6-70 mgC/l 20 (ca 1.0 gC/m2/a) 40

60

Jun

Soil Depth, cm Depth, Soil Jul 80 Aug

Sept O 20-120 mgC/l 100 (2-18 gC/m2/a) 0 10 20 30 40 NPOC, mgC/l Ah 15-40 mgC/l ALT B 5-15 mgC/l C 2-5 mgC/l Time Export to 5-31 mgC/l stream 2-10 gC/m2/a 15 moss

O layer 5 cm 20 cm 40 cm

35

30 5 cm 25 20

15 20 cm NPOC,mgC/l Active layer 10 5

0 1-Jun 15-Jun 29-Jun 13-Jul 27-Jul 10-Aug 24-Aug 7-Sep 21-Sep 40 cm Sampling date 15

60 cm 10

5

Permafrost 0 5.8.09 19.9.09 3.11.09 18.12.09 1.2.10 18.3.10 2.5.10 16.6.10 31.7.10 May September -5

Nfs 5 cm -10 Soil solution sampling and Nfs 20 cm Nfs 4016 cm temperature monitoring -15 Terrestrial C links to aquatic

moss

O layer 0 10

20

30

40

Depth, cm Depth,

50 Sfs 60 Nfs

70 0 20 40 60 80 Active layer DOC

Permafrost

17 Dissolved organic carbon in aquatic systems

• Authochtonous low C:N, high 15N, LMW, specific biomarkers • Allochtonous (terrigenic) High C:N, low 15N, low 13C, HMW, specific

18.0 LMW 16.0 biomarkers HMW 14.0

12.0

10.0

8.0

NPOC [mgC/l]NPOC 6.0

4.0

2.0

0.0 18 December March April May June July September Month DOC production

• Biological - Exudates - Cell lysis - Microbial breakdown of SOM DOM

• Physical Freeze-thaw cycles SOM DOM

19 Terrestrial controls over C export: soil C stocks and C:N ratio

Frey and Smith 2005, GRL

20 DOC “consumption”

• Microbial mineralization

20 DOC = CO2/CH4 + H2O y = 0.6295x - 5.5604 10

-1

0 y = 0.6365x - 18.041

y = 0.6484x - 19.44 -10 y = 0.612x - 26.517

-20

• Sorption to mineral matrix y = 0.5812x - 32.144 -30

DOC released or retained, mmol kg mmol retained, or DOCreleased -40 Ah (05CP) Ah (05BP) B (05CP) B (05BP) Bf (05BP)

-50 0 10 20 30 40 50 DOC added, mmol kg-1

0.80 0.80 50 • Precipitation y = 0.0138x + 0.3777 y = 0.0466x - 0.2044 0.70 0.70 2 y = 5.8368x + 5.4781 2 R = 0.9391 R = 0.8213 R2 = 0.7657 0.60 0.60 40

0.50 0.50 30 0.40 0.40

0.30 0.30 20

b, mmol DOC/kg 0.20 0.20 10

partition coefficient (m) partition coefficient 0.10 (m) partition coefficient 0.10

0.00 0.00 0 0 5 10 15 20 0 10 20 30 0.0 2.0 4.0 6.0 8.0

Fe(d) SSA, m2/g OC, mol C/kg soil 21 Permafrost and dissolved C:

A

Органический

слой

СТС СТС Periodic forest fires ?

мерзлота мерзлота Июнь Октябрь Июнь Октябрь Пожар Послепожарная восстановительная сукцессия

B

Органический слой

СТС

мерзлота Permafrost degradation

СТС мерзлота

Деградация мерзлоты

DOC DIC 22 and ecosystems: why dissolved carbon is important • Largest amount of carbon (of which 1-2% is dissolved) locked in soils and particularly conserved within the frozen ground (SOC = 1672 PgC, Tarnocai et al 2009)

• Dissolved carbon is most labile and indicative component of soil C reservoir

• Highest rates of warming and permafrost degradation

• Highest sensitivity of ecosystem processes to ongoing climate change

• Little is known about behavior of dissolved carbon in arctic and subarctic watersheds 23 Global change: permafrost degradation and an increase of active layer thickness

Monitoring sites

Positive trend in ALT depth By 2091-2100, permafrost extent will be decreased 30- 75% and active layer thickness increased about 55-125 cm, compared to 1991-2010 (Park and Walsh 2013, EGU General Assembly)

Implications for C export: Higher retention times in soil (DOC negative) Negative trend in freezing depth Higher mineralization rates (DIC, pCO2 positive) IPCC 2007, 24 Higher weathering rates (DIC positive) from Frauenfeld et al 2004 Global change: hydrology

Eurasian river annual runoff to the Arctic tends to increase for ca. 2.0 km3/year/year (Peterson et al 2002, Science)

Implications for C export: causes are debatable, but C export is considered to be increased 25 (e.g. Gordeev and Kravchishina 2009) Global change: vegetation

Figure from Dolman et al 2012, Biogeosciences

Changes and their effects on C export: Net ecosystem productivity (likely +) Northward shift of vegetation zones (likely +) Desertification in Eastern and Central (-) Shortened Fire Return Interval (-) 26 Studies of projected changes on riverine C export • Long-term monitoring data • Space-for-time approach

Central Siberian Plateau: RFBR-CRDF RUG1-2980-KR- Circum-polar studies: River basin: 10 “Megaprojects”, RSF Arctic-GRO (PARTNERS), “Megaprojects”, RSF project Rosgydromet data project 27 (Gordeev et al 1996) 2010-2012, 2013-2015… 2005 -… Long-term monitoring: Rosgydromet

R-ArcticNet - A Database of Pan-Arctic River Discharge

http://www.r-arcticnet.sr.unh.edu/v4.0/main.html 28 General characteristics of Arctic rivers

11% of global freshwater input to the world ocean >10% of global C export to the world ocean

Siberian sector:

% of 6 major % of total Ob’ Yenisey sum Arctic rivers to the AO Q, km3/a 427 636 581 111 1755 77.6 35.1 DOC, Tg/a 4.12 4.65 5.68 0.82 15.3 84.3 44.8 DIC, Tg/a 6.15 6.66 5.43 0.70 18.9 67.0

Source: Gordeev et al 1996, 2009, Raymond et al 2007, Striegl et al 2007, Cai et al 2008, Cooper et al 2008, McGuire et al 2009, Holmes et al 2011, Prokushkin 29et al 12 Tg = 10 g 2011, Amon et al 2011 Recent estimates of carbon in rivers…

Dolman et al. 2013 Biogeosciences (based on Meybeck et al., 2006)

West Kara (Ob) East (Yenisey) West (lena) East Laptev sea (Kolyma)

13% 17% 19% ! 28% 35% DIC flux 39% DIC flux DIC flux DIC flux DOC flux DOC flux DOC flux DOC flux POC flux POC flux POC flux POC flux

31% 56% 22% 61%

42% 37% 7.7 TgC/a 9.6 TgC/a 11.1 TgC/a 2.4 TgC/a

McGuire et al. 2009, Ecol Monogr (based on numerous sources)

Lena Kolyma Ob Yenisey 1% 6% 4% ! 16% 33% 29%

41% 35%

58% 59%

67%

51% 30 9.9 TgC/a 12.8 TgC/a 9.9 TgC/a 2.3 TgC/a Basin characteristics

Amon et al 2011, GCA

31 Seasonality of Hydrology and C fluxes in major Siberian Rivers

60 freshet 90000 summer-fall Ob' 80000 50 R-ArcticNet Yenisey winter 70000 Lena Kolyma 40 60000

/month

3 50000 30

40000

20 30000 annualof % runoff

Discharge,km

20000 10 10000

0 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ob' Yenisey Lena Kolyma

70 spring summer-fall 60 winter

50

40

30

% of annualof % DOC flux 20

10

0 Ob’ Yenisey Lena Kolyma Freshet (May-June) water flux: 30-50% C flux: 30-60% Welp et al 2005, GRL Holmes et al 2011 Estuaries and Coasts 32 Major Arctic Rivers Dissolved C: annual values Gordeev et al 1996, 2009, Raymond et al 2007, Striegl et al 2007, Cai et al 2008, Cooper et al 2008, McGuire et al 2009, Holmes et al 2011, Prokushkin et al 2011, Amon et al 2011

30 8 b) а) 25 DIC DOC 6

) 20

)

-1

-1

a 15 -2 4

(mgС l (mgС

10 m (gC Annual C export C Annual 2 5

Mean annual C concentrations concentrations C annual Mean 0 0

Ob

Ob

Lena Yana

Lena Yana

Yukon

Nidym

Anabar Olenek

Yukon

Nidym

Kolyma

Yenisey

Anabar Olenek

Indigirka

Kolyma

Yenisey

Khatanga

Indigirka

Аmguema Mackenzie

Khatanga

Tembenchi

Аmguema Mackenzie

Kochechum

P.Tunguska*

Tembenchi

Kochechum Rivers of basin

N. Tunguska** N.

P.Tunguska* N. Tunguska** N. Rivers of Arctic Ocean basin Decreasing trend of concentrations and annual fluxes from West to East, specifically for DIC Limitation for response prediction: -Data quality -Different parent materials 33 -Disturbances Case study in : Ob’ basin (Frey and Smith 2005, GRL)

Projected “2.7–4.4 Tg yr-1 increase in terrestrial DOC flux (from 9.2 Tg yr-1 to 11.9–13.5 Tg yr-1) from West Siberia to the Arctic Ocean by 2100.

These estimates are in fact conservative if DOC concentrations peak during spring flood. Furthermore, if the recently observed increases in Siberian precipitation [Serreze et al., 2000; Frey and Smith, 2003] and river discharge [Peterson et al., 2002; et al., 2005] continue, even larger increases are likely.” 34 Central Siberian River basins and study goals Yenisey River basin Stream basins within Central Siberian Plateau Nizhnyaya Tunguska river basins river watershed

Gradients: Fire history (burned 0, 4, 20, 50 and >100 years), Gradients: permafrost, vegetation, size, Climate, permafrost, SIMILAR: climate, parent Gradients: vegetation, rocks (Siberian basalts) Climate, permafrost, SIMILAR parent rocks 35 vegetation, parent rocks (Siberian basalts) Yenisey River basin characteristics

36 Yenisey basin: DOC and DIC

100 5 permafrost 80 Total C flux 4

60 3

40 2

TC flux g/m2/June

Continuous permafrost, % 20 1

0 0 -12 -10 -8 -6 -4 -2 0

MAAT, oC

Cryohydromorphic landscapes of 61-65oN latitude zone produce elevated C fluxes

40

35

30

25 20 DIC 15

10 Dissolved carbon[mgC/l] Dissolved DOC 5

0

51o42'

51o26' 51o26'

58о01'01.3'' 60о54'18.1'' 63о15'09.7'' 65о36'04.6'' 66о25'7.41'' 69о45'30.6'' Енисей Енисей Енисей Енисей Енисей Енисей Енисей Енисей sampling stations 37 Total C flux in Yenisey River from South to North shows substitution of IC to OC Yenisey basin: dissolved gases

4000

3500

3000

2500

2000

pCO2 [ppm] 1500

1000

500

0

Кас Кемь Сым Бахта Елогуй Комса Летняя Ангара Гаревка Дубчес Турухан Фокина Енисей 3 Енисей 4 ЕрачимоСеверная КурейкаЕнисей 5 ГравийкаХантайка Дудинка Енисей 6 Енисей е1 Вороговка Мироедиха Малая Хета Большой Пит Большая Хета Сухая Тунгуска Сухая Дудинка Нижняя Тунгуска Енисей е2 (Зотино) р. Игарка (Старая) 1000 Подкаменная Тунгуска

100

10

pCH4 [ppm]

1

0.1

Кас Кемь Сым Бахта Елогуй Комса Летняя Ангара Гаревка Дубчес Турухан Фокина Енисей 3 Енисей 4 ЕрачимоСеверная КурейкаЕнисейр. 5 ИгаркаГравийкаХантайка Дудинка Енисей 6 Енисей е1 Вороговка Енисей е2 Мироедиха Малая Хета Большой Пит Большая Хета Сухая Тунгуска Сухая Дудинка Нижняя Тунгуска

Подкаменная Тунгуска River flows showed supersaturation by GHG (relative to atmospheric levels), reflecting large flux of C to the Arctic Ocean in gaseous form 38 River basins of Central Siberian Plateau

39 Prokushkin et al 2011, ERL Hydrology of rivers of Central Siberian Plateau

25000 Freshet (May-June) water flux: >60%

20000

15000

10000

Dailydischarge, m3/s

5000

0

01.01.06 01.04.06 01.07.06 01.10.06 01.01.07 01.04.07 01.07.07 01.10.07 01.01.08 01.04.08 01.07.08 01.10.08 01.01.09 01.04.09 01.07.09 01.10.09 01.01.10 01.04.10 01.07.10 01.10.10 01.01.11 01.04.11 01.07.11 01.10.11 01.01.12 01.04.12 01.07.12 01.10.12

-12,0 NT KO -14,0

-16,0

-18,0 d18O -20,0 1% a year

-22,0

-24,0

-26,0 1.10.05 29.5.06 24.1.07 21.9.07 18.5.08 13.1.09 10.9.09 8.5.10 3.1.11 31.8.11 Date Prokushkin et al 2011, ERL 40 Dissolved carbon in Central Siberia

25000 50 Discharge DOC 45 20000 DIC 40

35

15000 30

25

10000 20

Discharge [m3/s] Discharge 15

Concentrations [mgC/l] Concentrations 5000 10

5

0 0 28.05.2005 10.10.2006 22.02.2008 06.07.2009 18.11.2010 01.04.2012 14.08.2013

Freshet (May-June) 55–71% for water runoff 64–82% for DOC 37–41% for DIC

Temporal and Spatial variation of DOC, DIC: Dominance of snowmelt season and increased flux in wet years Large differences in amounts of DIC and DOC among rivers (for DIC causes are still questionable) 41 Dissolved carbon in rivers of Central Siberian Plateau

30 8 b) а) 25 DIC DOC 6

) 20

)

-1

-1

a 15 -2 4

(mgС l (mgС

10 m (gC Annual C export C Annual 2 5

Mean annual C concentrations concentrations C annual Mean 0 0

Ob

Ob

Lena Yana

Lena Yana

Yukon

Nidym

Anabar Olenek

Yukon

Nidym

Kolyma

Yenisey

Anabar Olenek

Indigirka

Kolyma

Yenisey

Khatanga

Indigirka

Аmguema Mackenzie

Khatanga

Tembenchi

Аmguema Mackenzie

Kochechum

P.Tunguska*

Tembenchi

Kochechum Rivers of Arctic Ocean basin

N. Tunguska** N.

P.Tunguska* N. Tunguska** N. Rivers of Arctic Ocean basin

25 25 y = 4.2629e0.0132x A 2 B DOC R = 0.7721 Decreasing trend of concentrations and 20 20 y = 1.8607x + 29.371 R2 = 0.6577 annual fluxes from South to North 15 15 y = 1.5256x + 20.032 R2 = 0.89 10 10 Positive correlation with MAAT, forested DIC 5 mgC/l DOCconcentrtions, 5 areas (Prokushkin et al 2011, ERL) mgC/l DOC/DICconcentrations,

0 0 -12 -10 -8 -6 -4 -2 0 0 20 40 60 80 100 120 MAAT, oC forest coverage, % 42

Coniferous forests are the major source of DOC!

1000

100

NT

Lignin S8 Lignin [ug/L] 10 KO Ob' Yenisey Lena Kolyma

120000 300 1 Q 4.0 0 5 10 15 20 25 lignin NPOC [mgC/L] 100000 250

3.0 Data: 80000 200 ArcticGRO, PARTNERS

60000 150 (http://www.arcticgreatrivers.org/data.html) 2.0

Sig8. ng/l

SUVA(m/l/mgC) Prokushkin et al unpublished

Discharge, m3/s 40000 100

1.0 NT KO 20000 50

0 0 0.0 10.12.02 28.6.03 14.1.04 1.8.04 17.2.05 5.9.05 24.3.06 10.10.06 28.4.07 0.01 0.1 1 10 100 Discharge (m3/s) Date 43 DOC composition (unexplained patterns): Pyr-GC/MS-IRMS, 13C NMR CP MAS data

60 Carbohydrates Anaheim lake 50 Phenolics (USA) Proteinaceous

40 Alkylaromatics NT 03.08.2008

30

NT 28.08.2009 Relativeamount [%]

20

NT 03.06.2010 10

NT 19.07.2010 0 21-May 11-Jun 2-Jul 23-Jul 13-Aug 3-Sep NT 16.08.2010 Date NT 15.09.2010

350 300 250 200 150 100 50 0 -50 -100-150 chemical shift (ppm) -25 African -26 swamp -27 KO 01.06.2008 -28 KO 28.08.2009

-29

C [‰] C 13

 -30

-31 KO 09.06.2010 -32 2-Methoxy-phenol KO 19.07.2010 -33 Ethybenzen 2,4-Pentadienal -34 KO 16.08.2010 20-May 17-Jun 15-Jul 12-Aug 9-Sep

Date KO 15.09.2010

300 250 200 150 100 50 0 -50 -100-150 chemical shift (ppm) • Surprisingly little seasonal and geographic variation in riverine DOM composition 44 • Large temporal changes in 13C signature of individual compounds Dissolved GHG

3500 [CO2] ugC/l

3000

2500

2000

1500

1000

500

0 31.05.125 20.06.12 10.07.12 30.07.12 19.08.12 08.09.12 28.09.12 [CH4] ugC/l

4

3

2

Kochechum 1 N Tunguska

0 31.05.12 20.06.12 10.07.12 30.07.12 19.08.12 08.09.12 28.09.12

River waters are supersaturated with GHG Dissolved GHG is important portion in total C flux (10% of total DC) 45 Future of C export from Central Siberian Plateau

N Tunguska River: the Southern part of Central Siberian Plateau

Kochechum River: the Northern part of Central Siberian Plateau

Only projected increase in water flux to 2100 (e.g. 0.33 km3/year/year for N Tunguska River) may almost double terrestrial C export to rivers Together with an increase in NEP/terrestrial C accumulation of Northern territories it may increase total C flux up to 700% of current values (e.g. Gordeev and Kravchishina, 2009, Frey and Smith, 2005) Prokushkin et al 2011, Doklady Sciences 46 DOC behavior concept: latitude

Boreal deciduous conifer forests Evergreen taiga and mixed boreal forests Forest-tundra, tundra

High labile C Hydromorhism Permafrost

DOC concentration [mgC/l] DOCconcentration Climate change Retention in soil Low productivity Mineralization Low labile C Mineralization

50 55 60 65 70 75 Latitude [oN]

Gymnosperm vegetation (the middle of boreal belt) is the primary source of DOC in Arctic rivers (A. Myers-Pigg et al submitted). 47 DOC/DIC/pCO2 behavior

100%

90% DIC 80%

70%

60% Climate change

50% [mgC/l]

2

40% CO

p

DIC/DOCproportion 30% DOC DIC/ 20%

10%

0% Seasonal changes: Freshet Summer-fall Winter 50 55 60 65 70 75 Latitude [oN]

Retention in soil, DOC mineralization and rock weathering rates tend to increase

Result: substitution of DOC for DIC in total carbon flux

(TC changes might be negligible (Striegl et al., 2005, 2007)) 48 Wildfire effects ca. 1% of territory burned annually

MODIS (modeled GPP)

Major Siberian Rivers: Central Siberian streams Fire year of 2003 burned 4, 20, 65 and >100 years ago Central Siberian Rivers

Fire scars demonstrate low NPP: territories have potentially higher DOC production at no fire scenario 49 2013…

July 20, August 6, 2013 2013

35 30 NPOC SO4 30 25

25 20

20 15

15 SO4, mg/l

NPOC, mgC/l NPOC, 10 10

5 5

0 0 6.5.13 26.5.13 15.6.13 5.7.13 25.7.13 14.8.13 3.9.13 23.9.13 13.10.13 Date

50 Stream C fluxes in post fire chronosequence

Changes in DOC, SUVA, DIC and specific conductivity (SC) of streams draining watersheds of different fire history. Note log scale for SC. Parham et al, 2013, submitted to Biogeochemistry Fires combusting OM and deepening the ALT - decrease DOC release from basins, - increase the release of DIC and other inorganic solutes - change in DOM composition (e.g. lower aromaticity of released DOC)

Recovery of ecosystem structure in ca. 50 years after a fire coincides with the 51 recovery of stream C fluxes Pyrogenic carbon (dissolved black carbon, DBC) is intrinsic component of Siberian riverine DOC

Nizhnyaya Tunguska River 25 1000 a 20 800

/s)

3

15 600 gC/l)

m

10 400

BC-BPCA ( BC-BPCA

Discharge (1000 m (1000 Discharge 5 200

0 0 J F M A M J J A S O N D 2006 Kochechum River 16 1000

14 b Q BC 800

/s) 12

3

10 gC/l) 600 m DBC versus DOC concentrations of global rivers. 8 Jaffé et al 2013, Science 6 400

BC-BPCA ( BC-BPCA

Discharge (1000 m (1000 Discharge 4 200 0.5 2 y = 0.0229x - 0.1757 0 0 R2 = 0.8601 0.4 J F M A M J J A S O N D 2006 0.3 DBC concentrations in rivers of Central Siberian 0.2 Plateau.

BC-BPCA[mgC/l] Prokushkin et al, unpublished 0.1

0.0 DBC versus DOC concentrations of Siberian rivers. 0 5 10 15 20 25 30 Myers-Pigg et al 2013, ASLO meeting 52 NPOC [mgC/l] Indicators of permafrost degradation

1000

N2 100 N10

10 N15

(mg/l)

-

Cl 1

N13 N9 N14 0.1

0.01 1 10 100 1000 10000 100000 1000000 Basin area (km2)

Evaporite signal as NaCl/CaCl2 appeared in river/stream waters through “through taliks” and wildfires may accelerate this process Parham et al, 2013, Biogeochemistry 53 Wildfire effect Implication for C export:

• Combustion products of terrestrial OM constitutes up 8% of DOC in Siberian rivers

• Combustion of C source leads to decreased DOC production in terrestrial ecosystems and lower release to rivers

• Deepen active layer leads to higher retention of DOC in soils and lower DOC release, but higher mineralization and weathering rates cause elevated DIC flux

• DOC flux from large Siberian rivers can be potentially larger with no fire scenario 54 Conclusions • Rivers draining Siberia demonstrate significant potential to increase the release of terrestrial carbon to the Arctic Ocean. Increased hydrological C losses are projected through:

(i) enhancement of temperature-controlled DOC, DIC, POC and CO2 production processes within watersheds; (ii) raised precipitation, thereby increasing C mobilization from organic-rich layers; (iii) introduction of a new source of C as NEP increases/vegetation shifts northward and (iv) release of old C from degrading permafrost Increased DOM (C,N and P) input may significantly change NPP in river, estuarine and ocean ecosystems

Dry scenario of warming in high latitudes undoubtedly leads to decreased terrestrial C export due to: • inhibition of DOC production in terrestrial ecosystems and less DIC and pCO2/pCH4 transport • shorten fire return interval, removing the source of OC in terrestrial ecosystems 55 Thank you for attention!

Acknowledgements Thanks all colleagues from IF SB RAS, GET-CNRS, MPI-BGC, TAMUG, Uni Hannover, FFPRI and others for joint field and laboratory works and constructive 56 discussions. Themes for working groups

• 1. Compare C concentrations and fluxes by major Siberian rivers: spatial patterns and different estimates... • 2. Calculate flow-weighted mean annual C concentrations for Siberian rivers. • 3. Analyze elements bound to DOC • 4. Calculate seasonal C fluxes

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