Carbon Sequestration in California s Rangeland Soils Nicasio Native Grass Ranch Whendee L. Silver Department of Environmental Science, Policy, and Management University of California, Berkeley CAL-CAN March 31 2011
Plants and soil microbes have a significant effect on global atmospheric CO 2 concentrations Atmospheric CO 2 ( ppmv ) 390 380 370 360 350 340 330 320 310 Year
Projected Atmospheric CO 2 (ppmv) 450 440 430 420 410 400 390 380 370 360 350 Reducing emissions alone will not mitigate climate change Hypothetical emissions reduction scenario Year
Carbon comes into ecosystems via Photosynthesis CO 2 CO 2 via photosynthesis+nutrients+water = Plants
Carbon leaves ecosystems via Respiration from soil microbes CO 2
CO2 Photosynthesis CO2 Respiration DOC
Carbon Inputs > Carbon Outputs = Terrestrial Carbon Sequestration Soil Carbon
Grasses allocate a high propor/on of their photosynthate belowground to roots greater soil carbon pools
Grasslands cover a significant por/on of the Earth s land surface *30% of global land surface *Over half of the global land use *33% of the US land area *56% of California land area
Conant et al. (2001) showed that management can increase soil C stocks
Soil carbon pools tend to increase with improved grazing practices Change in Soil C Stock (Mg C ha -1 y -1 ) 2 1 0-1 30 40 50 60 Latitude ( o N) 35 case studies Redrawn from Conant et al. 2001
California Grasslands and Carbon Sequestra/on 23 million hectares of rangeland statewide Assume 50% available for C sequestra/on Units: MT = Metric ton MMT= Million metric tons CO 2 e = CO 2 equivalents MT=Mg=Metric ton
California Grasslands and Carbon Sequestra/on 23 million hectares of rangeland statewide Assume 50% available for C sequestra/on At a rate of 0.5 MT C ha - 1 y - 1 = 21 MMT CO 2 e/y At a rate of 1 MT C ha - 1 y - 1 = 42 MMT CO 2 e/y Units: MT = Metric ton MMT= Million metric tons CO 2 e = CO 2 equivalents MT=Mg=Metric ton
California Grasslands and Carbon Sequestra/on 23 million hectares of rangeland statewide Assume 50% available for C sequestra/on At a rate of 0.5 MT C ha - 1 y - 1 = 21 MMT CO 2 e/y At a rate of 1 MT C ha - 1 y - 1 = 42 MMT CO 2 e/y Livestock ~ 15 MMT CO 2 e/y Commercial/residen/al ~ 42 MMT CO 2 e/y Units: MT = Metric ton MMT= Million metric tons CO 2 e = CO 2 equivalents MT=Mg=Metric ton Electrical genera/on ~112 MMT CO 2 e/ y Emissions data: CA GHG Inventory ARB 2010
Managing grasslands for increased carbon content has many co-benefits Carbon sequestration in pastures and rangelands increases: Fertility Water holding capacity Soil stability Sustainability Productivity
Marin Carbon Project (UC Berkeley and Davis, Stakeholders, Resource Conservation District, UC Extension, Marin Agricultural Land Trust, Marin Organic, County Agricultural Commissioner, USDA-NRCS) 1. Do soil carbon stocks vary in California s rangelands? 2. Can we detect an effect of management on soil carbon stocks?
Large range in soil carbon pool size Considerable soil C storage capacity Soil Carbon to 50 cm depth (Mg C ha - 1 ) 150 100 50 0 Profile From Silver et al. 2010
We can detect changes in rangeland soil carbon pools with management Soils Carbon (Mg/ha) to 1 m depth 400 300 200 100 0 Soils sampled from 35 grazed rangeland sites in Marin and Sonoma Counties Fields (ranked) From Silver et al. In prep
Organic amendments increased soil carbon by 50 Mg C ha -1 in the top meter of soil Soil Carbon (Mg/ha) to 1 m depth 300 200 100 0 Extensive Intensive From Silver et al. In prep
Redirecting the waste stream and reducing greenhouse gas emissions Jepson Prairie Organics Livermore Landfill
Organic ma[er amendments (compost) to grazed rangelands (Nicasio and Browns Valley) Followed CO 2, N 2 O, and CH 4 fluxes and aboveground net primary produc/on
Compost increased soil moisture. Soil Volumetric Water Content (%) 50 45 40 35 30 25 20 15 10 5 compost control 0 Jun 09 Aug 09 Oct 09 Dec 09 Feb 10 Apr 10 Jun 10 Sep 10 Nov 10 Browns Valley, Ryals and Silver in prep
...and soil respiration Soil respiration (g C/m 2 /d) 18 16 14 12 10 8 6 4 2 Pretreatment Compost Control 0 Oct Dec Feb Apr Jun Aug Oct Dec Feb Apr Jun Aug 2008 2009 2010 Browns Valley, Ryals and Silver in prep
Compost increased plant and forage production by 50% Aboveground Production (Mg C ha -1 y -1 ) 4 3 2 1 0 Compost Control 2009 2010 Ryals and Silver in prep
We detected an increase in soil C pools after one year 1450 Valley Grassland Coastal Grassland 1250 Soil organic carbon (g/m 2 ) compost - control 1050 850 650 450 250 50-150
Composting added 12-15 Mg C ha -1 No significant increase in N 2 O or CH 4 emissions Ryals and Silver in prep
Carbon sequestration in California rangelands Next steps: 1. Test promising management approaches and mechanisms of C sequestration and long-term storage 2. Calibrate models to account for key drivers of change 3. Identify the relationships between climate (change) and management
Marin Carbon Project Nicasio Native Grass Ranch Support provided by: The Marin Community Foundation The Rathmann Family Foundation The Lia Foundation The Kearney Foundation for Soil Science USDA
Soil carbon increased detectably in the composted plots Wick Ranch 60 50 Compost Compost + Plow Control Plow 60 50 SFREC Soil Carbon (Mg ha -1 ) 40 30 20 Soil Carbon (Mg ha -1 ) 40 30 20 10 10 0 Dec 2008 Sep 2009 0
Subsoiling appears to lead to losses of soil C over year 1 4 Wick Ranch Carbon Concentration (%) 3 2 1 0 WR5 WR6 WR7 Block Compost Compost Plow Control Plow
Compost significantly increased plant and forage production Aboveground biomass (Mt C ha -2 ) 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 Control Compost Control 2009 2010 Compost Browns Valley, Ryals and Silver in prep
Organic amendments increase carbon gain by over 10 Mg C/ha in year 1 1500 Net Change (g C m -2 t -1 ) 1000 500 0 Assumptions: Heterotrophic respiration = 50% of total Root biomass = shoot biomass No difference in grazed biomass -500 Compost Control Nicasio, Ryals and Silver in prep
In Progress 1. Life Cycle Analysis: what is the full greenhouse gas accoun/ng of these management ac/vi/es? 2. Grazing Management: can grazing management alone increase soil carbon storage? 3. Plant Community: What happens to it and can we encourage na/ve perennial grasses through carbon farming?
Composting emitted approximate 12.6 Mg CO 2 eq over 16 weeks (~ 4.2 Dairy cow s worth over 1 yr ) Corn-heavy compost Manure-heavy compost Manure
Our new field sites incorporate some of the variability in the region
Questions