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 2 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 3 ENR 5268 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. 4 ENR 5268 SOIL EROSION: A 4-STEP PROCESS 1. Detachment 2. Breakdown 3. Redistribution/Transport 4. Deposition 5 ENR 5268 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. 6 ENR 5268 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 7 ENR 5268 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 11 ENR 5268 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 13 ENR 5268 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 20 ENR 5268 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 23 ENR 5268 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 24 ENR 5268 TRANSPORT, REDISTRIBUTION AND DEPOSITION OF SOIL ORGANIC CARBON ON AN ERODED LANDSCAPE AL (L , 2016) O O 2 2 , N , N 2 Top Soil 4 CO , CH 2 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 26 ENR 5268 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 27 ENR 5268 EROSION VS. AGGREGATION Erosion is the opposite of aggregation 28 ENR 5268 AGGREGATION LEADS TO C SEQUESTRATION Clay particles Domains Micro-aggregates Aggregates Peds Clay particles Domains Micro-aggregates Aggregates Peds Slaking leads to release of C and its oxidation by microbial processes 29 ENR 5268 AGGREGATION AND SOM POOL [(Cl – P – SOM)x] y 30 ENR 5268 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 32 ENR 5268 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 33 ENR 5268 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) 34 ENR 5268 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. 36 ENR 5268 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. 37 ENR 5268 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 38 ENR 5268 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 39 ENR 5268 40 .