Rangeland Soil Carbon: State of Knowledge Justin D. Derner and Jack A. Morgan

Road Map Carbon cycle Terrestrial carbon sequestration Carbon credits Definition Importance of rangelands Influenced by… Experimental results Gaps Carbon credits Offset project Key points

Carbon Cycle

Carbon Sequestration - Terrestrial Photosynthesis Respiration Storage of atmospheric carbon dioxide (CO2) in plant biomass and soil organic matter

Importance Mitigate rise in atmospheric CO2 Ecosystem co-benefits Greater soil water holding capacity Better soil structure Improved soil quality Enhanced nutrient cycling

Importance Rangelands occupy >50% of earth’s land area 830 million acres in US 15% of US soil potential for C sequestration Contain 10-30% of global soil organic carbon Could be released back to atmosphere with improper management

Influenced by… Climate Biome type Management Environmental conditions Derner et al. (2006) Plant and Soil Biome type Conant et al. (2001) Ecological Applications Management Derner and Schuman (2007) Journal of Soil and Water Conservation Environmental conditions Ingram et al. (2008) Soil Science Society of America Journal

Influenced by drivers of… Long-term changes in production and quality of above- and below-ground biomass Long-term changes in global environment (temperatures, precipitation patterns, rising CO2) that affect plant community composition and forage quality Drought effects on net C exchange

Experimental Results Grazing X Climate Grazing X Environment Adding a legume Different rangelands

Experimental Results: Grazing and Climate Derner and Schuman 2007

Experimental Results: Grazing x Environment Derner et al., in prep

Experimental Results: Adding a Legume Derner and Schuman 2007

Experimental Results: NW rangelands Svejcar et al. 2008

Experimental Results: Northern Plains rangelands Svejcar et al. 2008

Experimental Results: SW rangelands Svejcar et al. 2008

Experimental Results: Summary of different rangelands Location Vegetation Mean (and range) annual net ecosystem exchange (g C/m2/yr) Las Cruces, NM Desert grassland -160 (-254 to 94) Lucky Hills, AZ Desert shrub -93 (-162 to 55) Burns, OR Sagebrush steppe 73 (-61 to 229) Dubois, ID 83 (-47 to 260) Mandan, ND Northern mixed prairie 53 (-27 to 119) Nunn, CO Shortgrass steppe 107 (4 to 227) Svejcar et al. 2008

Gaps Lack of soil carbon information for western shrublands Accounting for total greenhouse gas budgets Understanding management by environment interactions Modeling capacity to temporally and spatially scale from site-specific findings to larger scales

Carbon credits – offset projects Chicago Climate Exchange (CCX) developed sustainably managed rangeland soil carbon sequestration offsets in early 2007 (updated August 2009) Scientific panel convened to determine sequestration rates with practices in land resource regions (expert input)

Benefits of offset projects New income source Reward sustainable ranching Improved environmental quality

Land Resource Regions B F E G C H J I

(metric tons CO2/acre/year Offset Rates LRR Region Offset Rate (metric tons CO2/acre/year Northwestern Wheat and Range Region (LRR B) 0.12 California Subtropical Fruit, Truck, and Specialty Crop Region (LRR C) 0.16 Rocky Mountain Range and Forest Region (LRR E) Northern Great Plains Spring Wheat Region (LRR F) Western Great Plains Range and Irrigated Region (LRR G) 0.27 Central Great Plains Winter Wheat and Range Region (LRR H) 0.20 Southwest Plateaus and Plains Range and Cotton Region (LRR I) 0.13 Southwestern Prairies Region (LRR J) 0.32

Economics – trade trends http://www.chicagoclimatex.com/market/data/summary.jsf

Key Points Carbon sequestration rates on rangelands are relatively low (0.07 to 0.30 Mg C ha/yr), but large land area available Large soil carbon pools with about 15% of US potential for additional C sequestration Improper management could release C stocks Soil carbon sequestration characterized by short periods (2-3 months) of high C uptake and long periods of C balance or small losses

More Key Points Sustainably managed rangeland soil carbon offsets available through CCX for many land resource regions Western sagebrush dominated lands are a large gap in our knowledge Uncertainty with greenhouse gas caps and regulations

Questions?