FATE of CARBON TRANSPORTED by EROSION Soil Erosions and Carbon Dynamics

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ENR 5268

FATE OF CARBON TRANSPORTED BY EROSION

Soil Erosions and Carbon Dynamics

Dr. Rattan Lal

1 ENR 5268

SOME ANOMALIES AND CONTRADICTIONS

Geomorphologists/Sed Parameter Soil Scientists imentologists

1. Can soils make a Yes No, small if any difference?

2. Is soil erosion a Source Sink source or sink?

3. Can agriculture be No, may not make Of course, it must be a solution? much difference

Geomorphologists/Sed Parameter Soil Scientists imentologists

1. Can soils make a Yes No, small if any difference?

2. Is soil erosion a Source Sink source or sink?

3. Can agriculture be No, may not make Of course, it must be a solution? much difference ENR 5268

THE CAUSES OF CONTRADICTIONS

Major causes of contradictions are:

I. Using different definitions

II. Using different methodologies

III. Using different scales of measurements

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SOIL EROSION

• It is a work, related to transport of soil from one location to another.

Work = F  d  cosΘ

• Thus, energy is involved in performing the erosion-related work.

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SOIL EROSION: A 4-STEP PROCESS

1. Detachment

2. Breakdown

3. Redistribution/Transport

4. Deposition

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ENERGY & EROSION

• Energy may be potential due to position of the soil, or kinetic due to velocity of the agent of soil erosion.

• Agents of soil erosion are sources of energy used to cause erosion.

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Energy Source for Soil Erosion

Water Wind Gravity Chemical Tillage Land slides Dissolution

Raindrop Shallow Concentrated Deep Stream Ocean Ice Flow Ravines Flow Current Splash Flow in Glacial erosion Inter-Rill Channels Gulley Stream Coastal Erosion Erosion Rill Erosion Erosion Bank Erosion Erosion

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RAINDROP EROSION (DETACHMENT)

www.partnershipsforchange.cc

www.soilerosion.net

www.dnr.state.md.us

www.natgeocreative.com 8 ENR 5268

SHEET EROSION (INTER-RILL EROSION) passel.unl.edu

dictionary.reference.com

engineering.purdue.edu 9 ENR 5268

RILL EROSION www.montcalm.org

luirig.altervista.org www.kidcyber.com.au 10 ENR 5268

GULLEY EROSION

www.learner.org www.swac.umn.edu

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RAVINE VS. GULLY EROSION

Gully: • Severe erosion by deep and concentrated flow leading to formation of wide and deep U or V-shaped channels • Slope gradient >5% • Soil loss >10 Mg/ha per year • Gully can be identified by high Stream Power Index signature values (>7) • Gullies are >30 cm deep

Ravine: • Extreme erosion by deep and concentrated flow at extreme velocity (stream flow at high velocity) • Slope >5% • An intricate network of parallel gullies form ravines • Drainage density is high and has multi-directional slopes • Ravines can often be identified by combination of terrain attributes (slope, profile curvature, and flow accumulation)

Both gully and ravine grow by head cutting 12 ENR 5268

GULLY VS. RAVINE EROSION

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mim2006.blogfa.com TUNNEL EROSION www.flickr.com soer.justice.tas.gov.au

14 www.usedrains.org.au www.usedrains.org.au ENR 5268

PEDESTAL EROSION

mavdisk.mnsu.edu

www.panoramio.com 15 ENR 5268

COASTAL EROSION

blogs.agu.org

centerforoceansolutions.org

www.bbc.co.uk 16 ENR 5268

STREAM BANK EROSION

http://en.wikipedia.org/wiki/Bank_erosion

www.greatswamp.org

17 itu205.ut.tu-berlin.de ENR 5268

LANDSLIDES http://landslides.usgs.gov/

http://landslides.usgs.gov/

blogs.agu.org 18 ENR 5268

DUST STORM

oceanworld.tamu.edu http://en.wikipedia.org/wiki/Dust_Bowl

19 www.militec-1.com bitethedust.com.au ENR 5268

SALTATION

commons.wikimedia.org www.cavinguk.co.uk

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SYDNEY OPERA HOUSE SEPTEMBER 23, 2009

www.2ue.com.au

21 www.telegraph.co.uk ENR 5268

SAND DUNES, DEPOSITION

http://www.panoramio.com/photo/61884167

http://journeywithstevenmichael.blogspot.com/2011/01/sand-trapped-in-waldport-oregon.html

Waldport, Oregon Sand Storms (2012)

22 http://www.panoramio.com/photo/29703555 ENR 5268

EROSIONAL IMPACTS ON SOIL CARBON BUDGET

I. On-site • Depletion of SOC pool • Disruption/slaking of aggregates • Increase in gaseous emissions • Exposure of calciferous horizon in some soils

II. Off-site • Redistribution of SOC pool • Burial of SOC in depressional sites

• Emission of CH4, N2O under anaerobic conditions

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THE HIGH TASTE OF EROSION

• It likes clay, silt and soil organic matter: the good things in soil • It cares less for gravels and rocks

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TRANSPORT, REDISTRIBUTION AND DEPOSITION OF SOIL ORGANIC CARBON ON AN

ERODED LANDSCAPE (LAL, 2016)

, , N

, , N 2

Top Soil 4

, , CH

CO Gaseous Gaseous Emissions

Stream

Delivery ratio is about 10%. It decreases with increase in distance from the source. 25 ENR 5268

ENRICHMENT RATIO

• Conc. In Sediments : Conc. In Soil

• ER for C can be 1 to 40

• SOC and clay are preferentially removed because of low density

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SOIL EROSION & CARBON DYNAMICS

1. Being a light fraction, and concentrated in the surface layer, SOC is preferentially removed by water and wind, depleting SOC on-site.

2. Truncation of soil profile may expose the calciferous layer to acid rains and weathering

3. Breakdown of aggregates exposes SOC to microbial processes

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EROSION VS. AGGREGATION

Erosion is the opposite of aggregation

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AGGREGATION LEADS TO C SEQUESTRATION

Clay particles Domains Micro-aggregates Aggregates Peds

Slaking leads to release of C and its oxidation by microbial processes

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AGGREGATION AND SOM POOL

[(Cl – P – SOM)x] y

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CARBON Sand or Silt particles SEQUESTRATION IN STABLE MICROAGGREGATES (Williams et al., 1967)

Soil Aggregates

Domain of clay crystals forming part of Microaggregates microaggregate s

X = Organic Molecules 31 ENR 5268

EROSION & AGGREGATION

• Aggregation sequesters SOC

• Dispersion releases SOC

• Erosion causes dispersion

• SOC transported/redistributed over the

landscape releases CO2 into the atmosphere

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GLOBAL SOIL EROSION & DYNAMICS OF SOIL ORGANIC CARBON

1.1 x 1015 g/y r decomposition and emission to the atmosphere 1500x 1 0 15 C 15 In world soil 3.99x 10 g/y r Stored within the terrestrial ecosystem 5.7 x 1015 g/y r C Displaced due to erosion

0.57x 1015 g/y r Transported to the ocean

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SOIL EROSION AS A CARBON SOURCE

World…… 1.1 Pg C/y

USA…….. 15 Tg C/y

Brazil…… 60 Tg C/y

India…….. 4.8 - 7.2 Tg C/y

Iceland…. 0.01-0.02 Tg C/y

(60-250 Tg C/1000 yr)

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SOIL EROSION AS A CARBON SINK (VAN OOST ET AL., 2007; STALLARD, 1998; SMITH ET AL., 2001)

1. Dynamic replacement of SOC at eroding sites and decrease in decomposition at depositional sites.

2. Deep burial of carbon.

3. Estimates of the magnitude of the sink range from 0.1-1 Pg/y

35 ENR 5268 SIMILAR ESTIMATES

Van Oost et al. (2007a) reported that the eroded and transported soil results in a 26% loss over time.

This estimate is in accord with Lal et al. (1998) estimate of 30% lost to water and atmosphere.

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DIFFERENT DEFINITIONS

Olson (2013) and Olson et al. (2014) proposed the definition of SOC sequestration with land unit borders was needed to account for the SOC stock being transported across land units.

Thus, the SOC stock being transported, redistributed or deposited by erosional processes is not being sequestered.

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PROBLEMS WITH THE "DYNAMIC REPLACEMENT" CONCEPT

On-site productivity is adversely affected by:

• Loss of plant nutrients (N, P, S) in runoff and sediments,

• Destruction of soil structure

• Loss of top soil by truncation, and decline in AWC

• Crusting, compaction, and impeded aerations

• Adverse changes in soil moisture and temperature regimes

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STRATEGIES OF MANAGING EROSION-PRONE SOILS

1. Adopt erosion-preventative measures.

1. Restore eroded soils

2. Re-carbonize soil and the ecosystem.

1. Minimize the off-site effects related to gaseous emissions, NPSP, and eutrophication.

2. Education at all levels.

3. Policy interventions

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