Carbon Capture Potential of California s Rangeland Ecosystems The Marin Carbon Project Can Land Management Enhance Carbon Sequestration in Soils? Jeff Creque Carbon Cycle Institute <jcreque@carboncycle.org> Nicasio Native Grass Ranch Projected Atmospheric CO 2 (ppmv) Bad News: reducing emissions alone will not mitigate climate change 46 45 44 43 42 41 4 39 38 37 36 Year
Good News: Plants have a significant effect on global atmospheric CO 2 concentrations Rangelands are geographically extensive 3-5% of global land surface area 3-5 % of US land area
Grasslands store one-third of the world s soil carbon Grasses allocate a large percentage of their photosynthate belowground to roots, exudates and soil biota, including mycorrhizae Study sites: 35 fields on 22 ranches Marin County Soil carbon pools vary widely, due to management history, precipitation, vegetation and soil type. California Literature Survey Regional Sampling Survey (Marin-Sonoma) Soil C to 5 cm depth [Mg C ha -1 ] Ranked soil profiles Ranked soil profiles California rangelands Ranked soil profiles Marin Carbon Project Silver, Ryals & Eviner 21 Ryals and Silver 21
MCP Survey Results: Organic matter (manure) additions correlated with an average soil carbon increase of 5 Mg C ha -1 in the top meter of soil 3 Soil Carbon (Mg C ha -1 ) 2 1 Not amended Amended Analysis of 35 fields (15 samples) from Marin and Sonoma Counties From Silver et al. In prep Soil C from amendments can be stored in soil C pools with long turnover times 1.2 Occluded Light Fraction Control Amended 1.2 Heavy Fraction Fraction modern 1..8.6.4 Fraction modern 1..8.6.4.2.2-1 1-3 3-5 5-1 -1 1-3 3-5 5-1 Depth (cm) Depth (cm) OLF: decades to centuries HF: centuries to millennia Analysis of 14 C in soil carbon fractions Silver et al. in prep. Hypothesis: Organic matter additions to rangelands can measurably increase soil carbon. Question: what happens if we succeed?
Results: Above-ground production (forage) has exceeded controls by 4-7% every year following the single ½ compost application in 28 control compost 1 Aboveground Net Primary Production (g m -2 ) 75 5 25 29 1 21 2 211 3 212 4 Year Ryals and Silver 212 Compost increased soil C Pre-treatment 29 21 211 Ryals and Silver 213 Models suggest that the C increase effect persists for > 1 years Ryals and Silver 213
5 Soil Volumetric Water Content (%) 45 4 35 3 25 2 15 1 5 Compost also increased soil moisture. compost control Jun 9 Aug 9 Oct 9 Dec 9 Feb 1 Apr 1 Jun 1 Sep 1 Nov 1 UCSFREC, Browns Valley, Ryals and Silver 213 Life Cycle Assessment suggests significant GHG mitigation potential statewide Global warming potential (MMT CO 2 e) Applied to 5% of CA Rangeland 3 2 1-1 -2-3 GHG Emissions GHG avoided GHG Sequestered Net Emissions from commercial sector (28) Emissions from Ag and forestry sector (28) -4 Compost Manure Fertilizer Redrawn from DeLonge et al. 213
Units: Mg = Metric ton MMT(Tg)= Million metric tons CO 2 e = CO 2 equivalents California Rangelands Carbon Sequestration Potential (Enhanced Photosynthetic Capture Alone) 23 million hectares (57 million acres) of rangeland in California: 67% (38 million acres) is grasslands and pastures. And there are our forest and Ag lands (Without avoided emissions) At a rate of.5 Mg C ha -1 y -1 = 28 MMT(Tg) CO 2 e y -1 At a rate of 1 Mg C ha -1 y -1 = 56 MMT(Tg) CO 2 e y -1 At a rate of 3 Mg C ha -1 y -1 = 169 MMT (Tg) of CO 2 e y -1 Livestock ~ 15 MMT CO 2 e y 1 Commercial/residential ~ 42 MMT CO 2 e y 1 Electrical generation ~112 MMT CO 2 e y 1 Emissions data: CA GHG Inventory 21 Marin Carbon Project: Carbon Farm Planning and Implementation Implementation Activities Identify demonstration C Farms and conduct farm assessments, including soil sampling (213). Apply compost on rangelands at scale (213) Complete 3 C Farm Action Plans Calibrate GHG accounting models with C Farm data. Confirm roles of project partners and scalability to other counties. Develop list of other carbon beneficial practices; Provide C Farm permit assistance, technical expertise, funding and monitoring assistance. Implement C Farming workshops for farmers and ranchers (215) Scaling Up: Applying compost to Carbon Farm pastures October, 213
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