- Carbon as the key to agricultural productivity and resilience
- Grass Root Systems
- ABC Ranch Field and Practice map
- ABC Ranch Soils
- GHG balance of ABC Ranch agroforestry systems
- GHG balance for ABC Ranch, soil organic carbon (SOC)
- ABC Ranch Soils
- Estimated Annual Forage Production, ABC Ranch
- Recommended RDM values
- Proposed ABC Ranch Agroforestry Systems
- Estimated biomass carbon stocks over time
- CO2e capture by proposed agroforestry systems
- Carbon Beneficial Practices and Estimated Outcomes
- CO2e Reduction/Sequestration Potential, ABC Ranch
ABC Ranch Conceptual C-Farm Plan Map
ABC Ranch Farm Report (CSU 2014)
In response to the rapid pace of global climate change, the Marin Carbon Project (MCP) seeks to engage agricultural producers as ecosystem stewards to provide on-farm ecological benefits, improve agricultural productivity, enhance agroecosystem resilience, and mitigate global climate change through a planning and implementation process known as “Carbon Farming.” MCP’s goal is to develop a countywide agricultural carbon sequestration program with producer outreach, and technical and economic support, to serve as a model for other regions in California, the western US, and the nation.
Carbon can be beneficially stored long-term (decades to centuries or more) in soils and vegetation through biological carbon sequestration. Carbon Farming involves implementing on-farm practices that: 1) decrease the production of green house gases on farm, and/or, 2) increase the rate at which the farm supports photosynthetically-driven transfer of carbon dioxide (CO2) from the atmosphere to plant productivity and/or soil organic matter. Enhancing agroecosystem carbon, whether in plants or soils, results in beneficial changes in other system attributes, including; soil water holding capacity and hydrological function, biodiversity, soil fertility, ecosystem resilience and agricultural productivity.
Carbon is the energy currency of most biological systems, including agricultural ecosystems. Technically, all farming is “carbon farming,” because all agricultural production depends upon plant photosynthesis to move carbon dioxide out of the atmosphere and into the plant, where it is transformed into agricultural products, whether food, flora, fuel or fiber. Carbon entering the farm from the atmosphere can end up in several locations: in the harvested portion of the crop, in the soil as root exudates and soil organic matter, in waste materials such as compost or manure, in standing carbon stocks, such as grassland vegetation or woody perennials (vines, orchards, etc.), or in other permanent woody or herbaceous vegetation such as windbreaks, vegetated filter strips, or riparian buffers, forests and woodlands.
While all farming is completely dependent upon atmospheric carbon dioxide in order to produce its products, different farming practices, and different farm systems, can lead to very different amounts of carbon capture and storage. The CFP process differs from other approaches to agricultural planning by focusing on increasing the capacity of the farm or ranch to capture carbon and to store it beneficially as soil organic matter and/or standing carbon stocks in permanent vegetation.
While agriculture often results in a gradual loss of carbon from the farm system, particularly from agricultural soils, CFP is successful when it leads to a net increase in farm-system carbon. By increasing the amount of photosynthetically captured carbon held, or “sequestered,” in long-term carbon pools on the farm or ranch, including soil organic matter, perennial plant roots and standing woody biomass, carbon farming results in a direct reduction in the amount of carbon dioxide in the atmosphere.
On-farm carbon in all its forms (soil organic matter, perennial and annual herbaceous vegetation, plant roots, root exudates and standing woody biomass), contains the solar energy used during its (photo) synthesis from atmospheric carbon dioxide, water and nutrients. As embodied solar energy, carbon provides the energy needed to drive on-farm processes, including the essential soil ecological processes that determine water and nutrient holding capacity and availability for the growing crop. Consequently, the CFP process views carbon as the single most important element, upon which all other on-farm processes depend (figure 1).
Carbon Farm Planning (CFP) is similar to Natural Resource Conservation Service (NRCS) Conservation Planning, but uses carbon and carbon capture as the organizing principle around which the Plan is constructed. This simplifies the planning process and connects on-farm practices directly with ecosystem processes, including climate change mitigation and increases in on-farm climate resilience, soil health and farm productivity.
Like NRCS Conservation Planning, CFP begins with an overall inventory of natural resource conditions on the farm or ranch, focusing on identification of opportunities for reduction of greenhouse gas (GHG) emissions and enhanced carbon capture and storage by both plants and soils. Building this list of opportunities is a brain-storming process; it should be as extensive as possible, including everything the farmer and planners can think of that could potentially reduce emissions and capture and sequester carbon on the farm.
While proposed actions should reflect the inherent limits of the farm ecosystem, financial considerations should not limit this brainstorming process, as one goal of the CFP process is to identify potential funding sources to realize implementation of the plan. From this process, a map of the ranch is developed, showing existing ranch infrastructure and all potential carbon capture practices and their potential locations on the ranch.
Next, the carbon benefits of each practice, as potentially applied at the farm scale, are quantified using the on-line USDA greenhouse gas model, COMET-Farm (www.comet_farm.com), COMET-Planner (www.comet_planner.com), or similar tool, to estimate tons of carbon that would be 1) avoided or 2) removed from the atmosphere and sequestered on farm, by implementing each practice. A list of potential practices and their on-farm and climate mitigation benefits is then developed.
Finally, practices are prioritized based on needs and goals of the farm. Economic considerations may be used to filter the comprehensive list of options, and funding mechanisms are identified, including; cap and trade, CEQA, or other greenhouse gas mitigation offset credits, USDA and other state and federal programs, and private funding. Projects are implemented as funding, technical assistance and farm scheduling allow. Over time, the CFP is evaluated, updated, and altered as needed to meet changing farm objectives and implementation opportunities, using the fully implemented plan scenario as a goal or point of reference. Where plan implementation is linked to carbon markets or other ecosystem service markets, periodic plan evaluation may be tied to those verification schedules.
In September, 2013, the ABC Ranch, located in northwestern Marin County at the head of the San Antonio Creek watershed, was selected as one of three MCP Demonstration Carbon Farms. As a participant in the Carbon Farm program, the Ranch has agreed to an ongoing partnership with the MCP through the three year Carbon Farm Planning Process and beyond.
The ABC Ranch encompasses 856 acres of rolling to steep hills intersected by riparian meadows and ephemeral streams located at the head of San Antonio Creek, in northwest Marin County, CA. The Ranch is dominated by grassland vegetation, but includes roughly 100 acres of oak woodland, predominantly on steeper north facing slopes in the southerly portion of the property. Woodland dominated areas are partially separated from the remainder of the Ranch by an unnamed ephemeral tributary to San Antonio Creek, running west to east to its intersection with the mainstem of San Antonio Creek, near the main entrance to the Ranch. This is the largest of several ephemeral watercourses traversing the property, and includes intact riparian forest vegetation, including buckeye (Aesculus californica), bay (Umbellularia californica) and gallery forests of valley oak (Quercus lobata), along several significant drainage features. The remaining unnamed tributaries all generally trend south to north or west to east, and feature largely grass-dominated channels and banks, except in their steeper upper reaches, which tend to include riparian forest vegetation, and a few massive specimen valley oaks in their lower reaches. Many of these creeks exhibit signs of historical-period incision, but appear largely stable today. Several seasonally wet meadows occur in and around the lower reaches of these small streams, while weed-dominated dry meadows and/or seeded hay or pasture species characterize the floodplain of the incised larger stream channel. Historic-era channel incision appears to have lowered water table levels in some of these wet –or formerly wet- meadow systems, reducing their production potential and driving plant communities toward upland species dominance. Nevertheless, intact stands of perennial grasses typical of regional wet meadow systems, including creeping wild rye (Leymus triticoides) and meadow barley (Hordeum brachyantherum) persist throughout much of the ranch, along with purple needlegrass (Stipa pulchra), which appears in sparse stands on drier sites. Upland benches are dominated by annual Eurasian grasses, including oats (Avena fatua), soft chess (Bromus hordeaceus) and foxtail (Hordeum murinum) and forbs, particularly broadleaf filaree (Erodium botrys). Scattered stands of valley oak occur throughout the grasslands of the ranch, and constitute a significant component of the visual character of the ranch landscape. There is little evidence of new oak recruitment however. Dense and scattered stands of thistles, including Yellow starthistle (Centaurea solstitialis) and purple starthistle (Centaurea calcitrapa), are also present.
The ABC Ranch has been farmed for over a century. Historically a dairy, the last cows were milked on the Ranch in the 1980s. Until 2013, the Ranch was run as a beef operation, with the addition of nearly 50 acres of vineyard in the 1990s. Today, approximately 36 acres of dry-farmed vineyard remain in cultivation, and nearly 70 acres is tilled for silage production, while the remainder of the property is leased for grazing of roughly 150 dairy heifers. The current lessee hopes to eventually revive a working dairy on the Ranch.
The Ranch has limited water resources, with surface water catchments dedicated to livestock and wildlife use only. Active erosion on the Ranch is limited to a few notable slides and gullies, with some evidence of ongoing sheet erosion and minor down-cutting in several stream reaches. The Ranch is in the process of certifying its pasture and silage areas as organic, and, effective May 2014, the current lessee is actively harvesting grasses from permanent pasture areas for silage and balage, while initiating a soil development program based on use of composted manures, intensification of pasture management and seeding of improved annual Eurasian pasture species, including ryegrass (Festuca perennis) and various clovers (Trifolium spp.).
ABC Ranch offers a number of opportunities for enhanced capture of atmospheric carbon consistent with both wildlife habitat improvement and enhancement of agricultural production. The Ranch’s extensive grassland areas are dominated by shallow-rooted Eurasian annual grasses, offering significant potential for expansion of deeper-rooted native perennials, present in scattered stands around the ranch (figure 2). Nearly all of the Ranch riparian areas, including its meadows, show signs of degradation and/or offer substantial riparian forest or silvopasture establishment potential. Degraded stream channels offer a number of opportunities for stabilization and associated plantings of vegetated riparian buffers and riparian forest cover. There are also several opportunities for windbreak and shelterbelt establishment, which can increase carbon capture through enhanced structural diversity, increase in woody species cover and decreased wind speed, resulting in water savings and enhanced net primary productivity in wind-protected areas. The carbon beneficial practices identified for implementation in this plan will also significantly enhance water infiltration and water quality, and increase pasture productivity on the Ranch, while improving aquatic and terrestrial wildlife habitat.
Ecological Site Delineation
Implementation of conservation practices within the Carbon Farm framework is based upon the grouping of land management activities by ecological site. An ecological site is determined by slope class, soil type, and aspect, so that each farm or ranch can be described using just a few ecological sites, which commonly reoccur across the farm landscape. Similar ecological sites can be expected to respond similarly to similar management, and to support similar types of vegetation and ecosystem processes, including carbon sequestration potential, assuming similar management history and similar management in the future. Ecological site delineation helps identify those sites most likely to yield significant carbon benefits given specific practices, and those for which specific practices may not be particularly productive. For example, increasing soil organic carbon with compost applications may be a very productive strategy on a shallow soil on a south-facing slope of 30%, but of limited value on an organic matter-rich meadow site. Trees, such as willow or valley oaks, might thrive on the latter site, while failing to survive on the former.
Ecological site delineation by USDA-NRCS is currently conducted at too coarse a scale to be of practical use in development of a CFP. The MCP CFP team has therefore developed its own ecological site criteria for ABC Ranch planning purposes, using field boundaries and practice variations to define “effective” ecological sites (figure 3).
Los Osos-Bonnydoon complex. The vast majority of the ABC ranch soils are classified as Los Osos-Bonnydoon complex, 15-30% slopes, with Los Osos loam (NRCS Range Site and Ecological Site classification, fine loamy claypan) found manly on concave side slopes and Bonnydoon gravelly loam (NRCS Range Site and Ecological Site classification, shallow gravelly loam) found mainly on convex side slopes. These soils are considered suitable for livestock grazing, with forage production limited by shallow depth and available water capacity of the Bonnydoon soils, and susceptibility of the Los Ososo soils to slippage. Both of these limitations are subject to improvement through management, including compost applications and improved grazing management to increase soil organic carbon (SOC) content. Grazing should be delayed until these soils are dry enough to withstand livestock traffic. Sufficient residual dry matter (RDM) must be maintained to provide soil protection and prevent erosion. The soil is classified in soil capability class IVe.
Bonnydoon taxonomic class: Loamy, mixed, superactive, thermic, shallow Entic Haploxerolls.
Los Osos taxonomic class: Fine, smectitic, thermic Typic Argixerolls. Forage production: Above ground production on these soils, if unimproved, ranges from a low of 2,200 pounds per acre in poor years to 3,800 pounds per acre in favorable years.
Blucher-Cole complex. Limited areas of Blucher-Cole complex, 2-5% slopes occur on alluvial flats throughout the Ranch. The unit is suited to livestock grazing but grazing should be delayed until soils have dried enough to withstand livestock impacts. This soil is subject to flooding, and the high water table can limit plant selection. Blue wild rye, Meadow barley, and Creeping wild rye are native grasses found on these soils on ABC Ranch. The soil capability class is IIIw, and the Range Site and NRCS Ecological Site classification are both Clayey Bottomland.
Blucher taxonomic class: Fine-loamy, mixed, superactive, thermic Fluvaquentic Haploxerolls.
Cole taxonomic class: Fine, mixed, superactive, thermic Pachic Argixerolls.
Forage production: Above ground production, if unimproved, ranges from 1,500 to 3,000 pounds
Saurin-Bonnydoon complex. This complex makes up about 45 acres of moderately steep slopes on the Ranch. The soils are derived from sandstone and shale, well drained, with rapid runoff and a high water erosion hazard. These soils are suited to grazing, but grazing should be deferred until the dry season if possible and RDM maintained above 1,200 pounds per acre whenever possible.
Forage Production: 2,200 to 4,000 pounds per acre.
Tocaloma-Saurin complex. This complex makes up about 96 acres of steep to extremely steep soils on the Ranch. These are deep, well-drained soils formed from sandstone and shale. Runoff is rapid an the risk of water erosion is high. These soils are suited to grazing, but grazing should be deferred until the dry season if possible and RDM maintained above 1,200 pounds per acre whenever possible. Tocaloma-Saurin taxonomic class: Fine, loamy, mixed, thermic Typic Haploxerolls.
Forage production: 2,000 to 4,000 pounds per acre.
|Map Unit Symbol||Map Unit Name||Acres||Percent of Area|
|101||Ballard gravelly, loam 2 to 9% slopes||0.5||0.1%|
|105||Blucher-Cole complex, 2 to 5%slopes||95.5||11.1%|
|106||Bonnydoon gravelly loam, 15 to 30% slopes||5.1||0.6%|
|141||Los Osos-Bonnydoon complex, 15 to 30% slopes||451.9||52.8%|
|142||Los Osos-Bonnydoon complex, 30 to 50% slopes||157.9||18.4%|
|163||Saurin-Bonnydoon complex, 30 to 50% slopes||44.7||5.2%|
|184||Tocaloma-Saurin association, very steep||42.2||4.9%|
|185||Tocaloma-Saurin association, extremely steep||54.4||6.4%|
|Soil||acres||low (lbs)||med||high||Total low||Total med||Total high|
NB: 1 AUM (animal unit month) is the amount of forage needed to support a 1,000 lb cow and her calf for one month; here it is assumed to be 900 lbs of dry forage.
1 AUY (animal unit year) is the amount of forage needed to support one animal unit (cow with calf, or equivalent) for one year.
*Data derived from Range Site values, Marin County soil survey, USDA
The Carbon Farm grazing plan combines overall ranch livestock carrying capacity with ecological site potentials and limitations to manage for optimum carbon capture — as forage production and soil carbon — within site-specific management constraints. In general, increasing forage production from permanent pastures on farm will tend to result in an increase in soil carbon, assuming good or excellent pasture management. Practices that reduce or repair soil erosion, reduce area of bare soil, reduce trailing and provide grazed vegetation sufficient rest for recovery and regrowth between grazing periods will tend to result in both more overall forage production and more carbon sequestered in both vegetation and soils.
Grazing management recommendations within this plan, therefore, include recommendations to increase pasture divisions to allow longer rest periods and increase livestock harvest efficiency, restore degraded pasture areas, and increase production through improved pasture rotation, compost applications and nutrient management (CSU 2014). Intensification of pasture management will require development of additional watering points on the ranch, as well as additional fencing, whether permanent or temporary.
Goals and Objectives: maximize forage production, meet National Organic Program pasture requirements, increase soil carbon, protect water quality, improve pasture nutritional profile and maximize length of grazing season.
Stocking rate. A baseline document prepared for MALT (Bush and Associates 1994) reports a year round stocking rate of approximately 200 animal units on approximately 665 acres, with an additional 130 acres in forage crops. Assuming cattle had access to forage crop acreage after harvest, this represents a total of 795 acres available for grazing for a stocking rate of roughly four acres per animal unit year (AUY), presumably supplemented with conserved forage derived both on and off farm. Based on Range Site average year production, and assuming a desired minimum end of season residual dry matter level of not less than 750 pounds per acre, actual “average year” unsupported and unimproved carrying capacity of the Ranch is conservatively estimated to be 2,250 lbs/acre x 800 acres / 12,000 lbs/ AUY = 150 AUY, assuming no supplemental feeding, no pasture improvements and no intensification of management. Currently, the Ranch is stocked with 150 dairy heifers, which also receive supplemental feed in the form of alfalfa hay. In addition, 2014 production of haylage and baylage on the Ranch, along with swathing of some areas at peak production, has resulted in capturing more grassland production at a nutritionally optimum period in its growth, enabling an increase in overall carrying capacity for the Ranch and a reduction in carbon losses due to oxidation of forage that would otherwise have been allowed to continue to senesce and decay and return a larger percentage of its embodied carbon to the atmosphere.
|Woody cover (%)||Annual Hardwood Rangeland RDM x percent slope (lb/acre)|
|Woody cover (%)||Coastal Prairie RDM x percent slope (lb/acre)|
Note: Metric conversion: 1 lb/acre = 1.12 kg/ha. *Source: Bartolome et al, 2006.
The ABC Ranch is currently divided into multiple large pastures with conventional post and wire fences. The lessee, McClelland Dairy (MC), is highly experienced with pasture management and plans to implement an intensified pasture management program going forward, using both temporary and semi-permanent electric fencing to achieve optimal grazing impacts and lengthen pasture rest periods. During the very dry fall and winter of 2013-14, MC applied compost to over 100 acres of pasture on the Ranch, and plans to continue compost applications as needed going forward. These practices are expected to enhance carbon capture on pastures as both forage and soil organic matter, leading to long-term increases in soil carbon sequestration and Ranch productivity.
As a USDA National Organic Program certified organic pasture-based operation, MC keeps records of pasture production, location of livestock on a daily basis and total percentage of forage consumed by livestock that is derived from pasture. This record forms an excellent basis for monitoring of pasture performance over time and identifying the need for management adjustments as they arise.
Marin Agricultural Land Trust (MALT) has held a conservation easement on the ABC Ranch since 1994, which protects both its agricultural and natural resource values in perpetuity. The Ranch is monitored annually and MALT considers the restoration of the Ranch to be a high priority. This easement provides a robust framework for certification of permanence for carbon sequestration verification and/or other ecosystem service markets, including water quality and wildlife habitat improvements
Potential Carbon Beneficial Practices and Anticipated Outcomes
The following conservation practice list includes all carbon beneficial practices identified as appropriate for ABC Ranch to date. NRCS Practice numbers appear in parentheses. (See Figure, A Conceptual Carbon Plan for the ABC Ranch). Quantification of the carbon capture potential of these practices was derived from a collaborative effort between MCP and Colorado State University Natural Resources and Ecology Laboratory (CSU-NREL, see appendices), and use of the NRCS on-farm carbon sequestration planning tool, COMET-Planner (www.comet-planner.com), or other sources as noted.
1. Compost Application (Interim Practice 777) (initiated Fall, 2013, 19 acres) — Application of ½” of compost to 200 acres of permanent pastures not previously treated. Increase soil organic carbon, water and nutrient holding capacity; improve water quality and forage production. Sequester over 200 tons of C each year for 20- 30 years.
2. Critical Area Planting (342/390/391) — Planting of degraded areas with trees, shrubs and/or permanent herbaceous cover (native species TBD). Total Acres: 17. Increase soil and biomass carbon, stabilize soils, improve water capture and habitat structural and species diversity. Increase wildlife habitat and carbon sequestration in woody vegetation. Increase soil and biomass carbon, improve soil water capture and water quality, reduce sediment delivery to streams, enhance climatic resilience and wildlife habitat structural and species diversity.
3. Fencing or Access Control (328/472) — Temporary electric fence protection for tree, shrub and herbaceous cover establishment on over 3 miles of riparian and critical area plantings. Increase soil and biomass carbon, stabilize soils, improve water capture, water quality and habitat structural and species diversity. This is a supporting practice that does not sequester carbon, but enables agroforestry plantings to establish and sequester carbon.
4. Field Border (386) — Planting of trees and shrubs on field borders (other than riparian and windbreak plantings). Total acres: 10. Increase soil and biomass carbon, stabilize soils, improve water capture, water quality and wildlife habitat structural and species diversity.
5. Hedgerow Planting/Windbreak (422/380/601) — Approximately 7000 lineal feet of windbreaks to increase soil and biomass carbon, stabilize soils, improve water capture, water quality and habitat structural and species diversity, and reduce water demand in vineyard and pasture areas through improved microclimate and climatic resilience.
6. Nutrient Management (590) — Sample soils and develop guidelines for compost, manure and other nutrient applications on approximately 400 acres of pasture to optimize nutrient applications, protect water quality, maximize carbon capture and enhance livestock and wildlife forage value.
7. No-Till System/Tillage Management (329) — Conversion of 70 acres of silage fields permanent pasture. Anticipated benefits include enhanced carbon capture through avoided tillage and equipment use, improved wildlife habitat and improved forage production.
8. Range Planting (550) — Seeding of native perennial grasses on approximately 200 acres for enhanced soil carbon sequestration, pasture productivity, climatic resilience and native species diversity. Estimated enhanced C-capture of over 200 tons per year.
9. Range Management/Prescribed Grazing (528) — Grazing management to favor native perennial grasses on over 400 acres for enhanced soil carbon sequestration, pasture productivity, climatic resilience and native species diversity. Estimated enhanced C-capture of over 400 tons per year.
10. Riparian forest buffer (391) — Planting of native trees and shrubs on approximately 30 acres of degraded riparian areas. Increase soil and biomass carbon, stabilize soils and stream banks and channels, aggrade stream channels, improve water capture and soil moisture and wildlife habitat structural and species diversity.
11. Riparian herbaceous cover (390) — Native herbaceous plantings on approximate 30 acres of riparian forest and non-forest riparian areas and wetlands. Increase soil and biomass carbon, stabilize soils and stream banks and channels, improve water capture and quality and wildlife habitat.
12. Silvopasture; tree establishment within permanent pastures (381/612) — Establish diffuse native tree cover (maximum 40% canopy cover) on approximately 30 acres of degraded floodplain pasture and intermittent native tree cover (approximately 5% canopy cover) on 100 acres of upland pasture. Increase soil and biomass carbon, provide shade for livestock and wildlife, improve soil water capture and water quality and enhance wildlife habitat structural and species diversity.
13. Stream crossings — Repair 5 degraded stream crossings to permit safe access for management purposes and limit concentrated livestock impacts. Improve water quality, reduce soil erosion, allow plant establishment and bank stabilization, improve overall riparian habitat quality, climatic resilience and landscape carbon and water capture capacity. Supporting practice.
14. Water Development (516, 614) — Install tanks, pipeline and wildlife-friendly water troughs for plant establishment, livestock distribution and wildlife use. Improved wildlife habitat, improved pasture management capacity, soil and biomass carbon capture from woody vegetation establishment and pasture improvement. Supporting practice.
15. Weed Management (315) — Improve native species diversity on approximately 10 acres of degraded pasture. Improve wildlife and livestock forage, stabilize soils and improve carbon and water capture by vegetation and soils. Supporting practice.
|Low (1-row) Windbreak -L||(1,395 m) One-row Windbreak, low vegetation class|
|Medium (1-row) + Low (1-row) Windbreak -ML||(221 m) Two-row Windbreak, one row with low vegetation class, one row with medium vegetation class|
|Tall (1-row) + Medium (1-row) + Low (1-row) Windbreak -TML||(580 m) Three-row Windbreak, one row with low vegetation class, one row with medium vegetation class, one row with tall vegetation class|
|Silvopasture||(23.6 ha) Silvopasture consisting of a mixture of native trees and shrubs in widely- spaced plantings|
|Riparian Buffer||(21.3 ha) Planting of Riparian Buffer consisting of a mixture of native trees and shrubs of the typical species composition and density as is found in coastal forest riparian areas|
Table 5. Estimated biomass carbon stocks over time for various Carbon Farm agroforestry systems. Estimates include above and belowground carbon stocks, but do not include soil C, which was not estimated for agroforestry practices (CSU 2014). All units are in metric tonnes (Mg) CO2e.
|Years since establishment||20||40||60||80|
|System||Biomass Carbon Stock (Mg CO2e/100 meters)|
|Low (1 row) + Medium (1 row) + Tall (1 row) Windbreak||8.0||15.7||22||26.4|
|Medium (1 row) + Tall (1 row) Windbreak||6.7||13.4||19.7||23.8|
|Medium (1 row) + Medium (1 row) Windbreak||5.4||10.7||15.3||15.3|
|Low (1 row) + Medium (1 row) Windbreak||4.0||7.7||10||10|
|System||Biomass Carbon Stock (Mg CO2e/ha)|
Table 6. Metric tonnes of CO2e capture by proposed agroforestry systems at ABC Ranch, at 20 years and maturity. Values shown are per 100 meters for each windbreak type, based on planned windbreak length, and by hectare for silvopasture and riparian forest buffer systems. See appendix, ABC Carbon Farm Report, for details.
|Hedgerow/Windbreak Description||Mg/CO2e/100m (ha)/20 years||Mg/CO2e/100m (ha)/maturity|
|(1,395 m) One-row Windbreak, one row low vegetation class||13.95 x 1.3 = 18.14||13.95 x 2.3 = 32.09|
|(221 m) Two-row Windbreak, one row low, one row medium vegetation class||2.21x 4 = 8.84||2.21 x 10 = 22.10|
|(580 m) Three-row windbreak, one row low, one row medium, one row tall vegetation class||5.8 x 8 = 46.40||5.8 x 26.4 = 153.12|
|(23.6 ha/58.3 acres) Silvopasture: a mixture of native trees and shrubs in widely- spaced plantings||23.6 x 42 = 991.20||23.6 x 169 = 3988.40|
|(21.3 ha/52.6 acres) Riparian Forest Buffer: a mixture of native trees and shrubs||21.3 x 73 = 1554.90||21.3 x 293 = 6240.90|
Figure 6. Projected GHG balance for ABC Ranch based on SOC changes and trace gas emissions only (CSU 2014). SOC changes include carbon added with compost, but do not include additional photosynthetic carbon resulting from enhanced plant growth in response to soil quality improvement from compost application.
|1. Compost Application (Interim Practice 777) (initiated Fall, 2013)||Application of ½” of compost to 200 acres of permanent pastures. Increase soil organic carbon, water and nutrient holding capacity;||At a rate of 1.09 tonnes of CO2e per hectare (0.44 tonnes per acre) per year, sequester 88 tonnes of CO2e on 200 acres each year and 1760 tonnes over 20 years.||Improved water holding capacity, soil quality and fertility, net primary productivity.||Ryals and Silver 2013,CSU 2014|
|2. Fencing or Access Control (328/ 472)||Temporary electric or permanent fence protection for tree and shrub cover establishment for three miles of windbreak and shelterbelt plantings.||Increase soil and biomass carbon capture on protected sites||Stabilize soils, improve water capture, water quality and habitat structural and species diversity.||Supporting practice.|
|3. Hedgerow/Windbreak (422/380/601)||2196 meters (7,027) feet) of windbreaks and shelterbelts to increase soil and biomass carbon.||Sequester 73 tonnes CO2e over 20 years,406 tonnes CO2e at maturity.||Sequester C, improve microclimate stabilize soils, improve water quality, and habitat diversity, reduce water loss.||COMET-Planner, COMET-Farm, CSU 2014.|
|4. Nutrient Management (590)||Sample soils and develop guidelines for compost, manure and other nutrient applications on approximately 400 acres of pasture.||Supporting practice||Optimize nutrient applications, protect water quality, enhance forage value. Enables evaluation of strategies for application of compost and other organic amendments, N budgeting and identification of nutrient limitations to plant carbon capture.||COMET-Farm; COMET-Planner, CSU, 2014.|
|5. Range Planting (550)||No-till seeding of native perennial grasses on approximately 200 acres.||Estimated enhanced CO2e capture of 0.22 tonnes per year, 44 tonnes per year on 200 acres or 880 tonnes on 200 acres over 20 years||Enhanced pasture productivity and native plant biodiversity.||COMET-Planner|
|6. Range Management/ Prescribed Grazing (528)||Grazing management to favor perennial grasses and ecosystem integrity on 400 acres||Estimated enhanced CO2e-capture of over 0.14 tonnes per acre per year, 56 tonnes per year on 400 acres; 1,120 tonnes over 20 years.||Enhanced pasture productivity, climatic resilience and species diversity.||COMET-Planner|
|7. Riparian forest buffer (391)||Planting of native trees and shrubs on approximately (21.3 ha/52.6 acres) of riparian area.||Sequester over 77 tonnes CO2e per year, 1,555 tonnes of CO2e over 20 years and 6,241 tonnes CO2e at maturity.||Stabilize soils and stream banks and channels, aggrade stream channels, improve water capture and soil moisture and wildlife habitat structural and species diversity.||(COMET-Farm), CSU 2014.|
|8. Water Development (516, 614)||Install tanks, pipeline and wildlife-friendly water troughs for plant establishment, livestock distribution and wildlife use.||Soil and biomass carbon capture from woody vegetation establishment and pasture improvement.||Improved wildlife habitat, improved pasture management capacity.||Supporting practice.|
|9. Critical Area Planting (342/390/391)||Stabilize 17 acres of degraded stream banks and hillside areas.||Sequester 1.1 tonnes CO2e per acre per year (2.72 tonnes/hectare/yr) for an estimated 18.7 tonnes/yr and 374 tonnes over 20 years.||Wildlife habitat, soil conservation on approximately 176 acres of eroding stream banks and hillsides.||COMET-Planner.|
|10. No-till system-Tillage Manage-ment (329).||Conversion of tilled silage fields to permanent pasture; 70 acres.||Sequester 0.35 tonnes CO2e/acre/year (0.86 tonnes CO2e/ha/yr), or 24.5 tonnes CO2e/year on 70 acres, or 490 tonnes on 70 acres over 20 years.||Permits establishment of perennial species/enhanced biodiversity, increased capture of soil C.||COMET-Planner|
|11. Stream Crossings||Repair 5 degraded stream crossings to permit safe access for management purposes and limit concentrated livestock impacts.||Supporting practice.||Improve water quality, reduce soil erosion, allow plant establishment and bank stabilization, improve overall riparian habitat quality, climatic resilience and landscape carbon and water capture capacity.||Supporting practice.|
|12. Silvopasture (381/612)||Establish trees within approximately 23.6 ha (58.3 acres) of pasture.||Sequester 2.1 tonnes CO2e/ha/year, or 49 tonnes per year, 991 tonnes at 20 years and 3988 tonnes at maturity.||Increase soil and biomass carbon, provide shade for livestock and wildlife, improve soil water capture and water quality and enhance wildlife habitat structural and species diversity.||COMET-Farm,|
|13. Weed Management (315)||Improve native species diversity on approximately 10 acres||Supporting practice.||Improve wildlife and livestock forage, stabilize soils and improve carbon and water capture by vegetation and soils.||Supporting practice|
|14. Field Border (386)||Planting of 10 acres of trees and shrubs on field borders .||Sequester 1.2 tonnes CO2e per acre per year, or 12 tonnes per year, 240 tonnes at 20 years and 966 tonnes at maturity||Increase soil and biomass carbon, stabilize soils, improve water capture, water quality and wildlife habitat structural and species diversity.||COMET-Planner|
|15. Riparian Herbaceous Vegetation Cover (390)||Woody and herbaceous vegetation plantings on approximately 30 acres of degraded wetland areas with exclusionary fencing and controlled livestock access.||1.2 tonnes per acre per year, based on riparian herbaceous vegetation. 36 tonnes/yr, and 720 tonnes over 20 years.||Improved wildlife habitat, improved soil and biomass carbon capture from vegetation establishment, improved water quality and water capture, improved forage production.||COMET-Planner, pending values for wetland restoration, see USDA 2014.|
Summary: Carbon Capture Potential
Table 8 shows overall potential for terrestrial sequestration/avoided GHG emissions on ABC Ranch through implementation of a suite of conservation practices as outlined above.
|Practice||Average Annual CO2e Reduction||20 yr CO2e Reduction||CO2e Reduction at Maturity|
|Rangeland Compost (Interim Practice 777)||88 Mg||1,760 Mg||1760 Mg|
|Range Planting (550)||44Mg||880 Mg||880 Mg|
|Windbreaks (380)||3.65 Mg||73 Mg||406 Mg|
|Prescribed Grazing (528)||56 Mg||1,120 Mg||1,120 Mg|
|Riparian Forest Buffer (391)||77 Mg||1,555 Mg||6,241 Mg|
|Riparian Herbaceous Cover (390)||36 Mg||720 Mg||720 Mg|
|No Till (329)||24.5 Mg||490 Mg||490 Mg|
|Critical Area Planting (342/390)||18.7 Mg||374 Mg||374 Mg|
|Field Border (386)||12 Mg||240 Mg||966 Mg|
|Silvopasture (381/612)||49 Mg||991 Mg||3988 Mg|
|Totals||408 Mg||8,203 Mg||16,945 Mg|
Average annual CO2e reduction values are provided in table 9, above, for illustrative purposes only. Actual sequestration of CO2 in response to management interventions and conservation practices is not expected to be linear over time, and thus will vary annually. Length of time during which a given practice will sequester carbon varies with each practice. For example, see tables 5 and 6 and figure 5 above for variable ages of maturity for different agroforestry practices. Accumulation of terrestrial carbon in response to each practice tends to increase cumulatively to maturity and then tends to decline, though remaining net GHG negative, relative to baseline conditions, for many years. This suggests the value of periodic renovation of windbreaks, shelterbelts, etc., to maintain high levels of carbon accumulation in these systems.
In some cases, rates of accumulation of CO2e drop below emission rates, resulting in net increases of GHG (see appendix, ABC Carbon Farm Report, CSU 2014, table 5). For example, figure 6 (above) shows net sequestration values associated with compost application to grazed grassland declining on ABC Ranch pasture soils over time, with soil N2O emissions gradually overtaking reductions in both soil organic carbon (SOC) and methane (CH4) associated with this practice, some three decades after initial compost application. This suggests reapplication of compost sometime during the third decade after initial application may be warranted for sustained GHG reduction benefits from this practice in this system.
Figure 6 shows the modeled GHG balance for ABC Ranch soils based on SOC changes and trace gas emissions from compost application to grazed grassland (ABC Carbon Farm Report, CSU 2014). Modeled SOC includes carbon added with compost, but does not include additional soil-sequestered photosynthetic carbon resulting from enhanced plant growth in response to improved soil quality due to compost application. This is because the model used in this analysis is not currently capable of quantifying the impact of compost application on system photosynthetic capture of CO2, except as influenced by the available N content of the compost. Because available N in compost is typically very low, the model does not generate a significant increase in plant growth from compost application, despite significant increases measured in the field (Ryals and Silver 2013). Improved hydrologic status, improved porosity, improved micronutrient status and other soil quality enhancements typically resulting from compost amendment are also not currently accounted for in the model. The ecosystem carbon team at CSU-NREL is in the process of updating the model to account for these important soil quality factors, shown by MCP research to be subject to positive influence by compost applications (Ryals and Silver 2013).
There is significant potential for additional GHG reduction and terrestrial carbon capture at ABC Ranch. Through implementation of a suite of NRCS conservation practices, described above, a conservatively estimated 408 Mg CO2e could be avoided or sequestered, both in soils and above and below ground biomass each year. Over 20 years this figure is 8,203 Mg CO2e. At maturity (20-80 years, depending upon conservation practice), these projects are projected to have sequestered 16,945 Mg CO2e.
The vast majority of GHG reduction potential on ABC Ranch, some 12,000 Mg of additional CO2 capture, results from 20 to 80 years of tree growth on field borders, silvopastoral systems and riparian forest buffers. Over 20 years, compost application to pasture is the single largest carbon-beneficial practice, at 1,760 Mg. In combination, a suite of enhanced pasture management practices also contribute significantly to overall CO2 capture on the Ranch, totaling roughly 3,200 Mg of CO2e over 20 years. There is also potential for additional on-farm carbon capture over time through the reapplication of compost on grazed grasslands at 20-30 year intervals, through the renovation of windbreaks or other agroforestry systems at maturity, and through the implementation of other carbon-beneficial practices not currently included in this Carbon Farm Plan. By stacking all of these practices, the greatest potential for capture and sequestration of GHG on ABC Ranch can be realized.
Practice monitoring (plant survival, pasture management, RDM monitoring, compost applications, etc.) should be carried out in coordination with annual inspections by MALT stewardship staff and/or project managers from the Marin RCD or others involved in project implementation. Soil C and other ecosystem services should be monitored in accordance with market or voluntary protocol requirements (if applicable). Baseline data and records of implementation activities, including locations, spatial extent of project(s), dates of implementation, etc. should all be included in plan implementation documentation. This plan should be viewed as a living document. It should evolve as practices are implemented and new information and new tools become available. Additional carbon-beneficial practices may be considered for inclusion in the plan in the future. GHG values presented here as associated with specific practices are considered to be both conservative and based upon the best available information at the time of this plan’s preparation (December, 2014).
US EPA 2011. Market Opportunities for Biogas Recovery Systems at U.S. Livestock Facilities. U.S. Environmental Protection Agency, Washington, DC.
Myhre, G., D. Shindell, F.M. Breon., 2013. Anthropogenic and natural radiative forcing. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group 1 to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK and New York, NY, USA.
Eve, M., Pape, D., Fluge, M. Steele, R. Mn, D. Riley-Gilbert, M. Biggars, S., (Eds.), 2014. Quantifying greenhouse gas fluxes in agriculture and forestry: methods for entity-scale inventory. USDA Technical Bulletin 1939. Office of the Chief Economist, USDA, Wa. DC. 606 pp. July 2014.
Five types of agroforestry systems are proposed for the initial MCP demonstration carbon farms. These systems are designed to meet diverse conservation and restoration goals, of which carbon sequestration in woody vegetation is just one part. They differ from the NRCS agroforestry prescriptions for the region in two key ways: 1) the systems are composed entirely of shrubs and trees native to the region, and 2) the systems have up to four times more species diversity than those in contemporary agroforestry plantings (NRCS 2004).
Rather than modeling potential growth and biomass carbon stocks of individual trees/shrubs and applying these predictions to the number of stems predicted for the carbon farm systems, we estimated the potential growth and carbon stocks of comparable native shrublands and forests. A literature review yielded area- based measurements for shrublands and forests in Marin, Sonoma, and Mendocino counties. We calculated the above- and belowground biomass carbon stocks for these comparable native systems, and then ascribed these area-based measurements to the area the agroforestry systems represent in the different farms. For linear systems we used the width of the rows estimated by MCP staff and calculated the area those systems represent in 100 meter increments, and applied the area-based biomass carbon stock and accumulation rates to those systems.
Biomass Accumulation Rates and Stock Values at Maturity
The agroforestry systems planned for the carbon farms are designed to mimic in structure and composition some of the native plant communities found in the region, as follows:
|Agroforestry System||Native Plant Community||Total Above and Belowground Biomass C (Mg/ha)|
|Medium Windbreak||Shrubland and Woodland||57.1|
|Tall Windbreak||Upland Forest||80|
|Riparian Buffer||Riparian Forest||80|
Low Windbreaks: The structure and composition approximates those of coastal shrublands (J. Creque, pers. communication). Strithold and Tutak (2009) cataloged shrublands in Marin and Sonoma Counties containing aboveground biomass carbon stocks of 21.4 Mg/ha. Estimated root biomass is 12.8 Mg/ha (Kummerow et al. 1977, Nabuurs et al. 2007). The FIA database contains information for only two of the genera found in the low windbreak species composition, and these data are roughly comparable to the published data. We applied an overall width of 1.8m (6 ft) to a single row of the low windbreak when calculating the area represented by a single row of this system (J. Creque, pers. communication).
Tall Windbreaks: The structure and composition of these systems approximates those of a native upland mixed conifer/deciduous forest (J. Creque, pers. communication). Hudiburg et al. (2007) described mature, upland forests in Marin county containing biomass carbon stocks with mean total above- and belowground biomass of 80 Mg/ha, including coarse woody debris, achieving peak biomass in 100-120 years. The FIA database contains useful information on four of the seven species described for tall windbreaks, with approximate biomass accumulation rates at the proposed planting densities of approximately 1.5 Mg C/ha. Based on these data we assume the windbreak would reach peak biomass in 80 years. We applied an overall width of 5.5 m (18 ft) to a single row of the tall windbreak when calculating the area represented by a single row of this system (J. Creque, pers. communication).
Medium Windbreaks: The structure and composition of these systems have characteristics of both native woodlands and shrublands (J. Creque, pers. communication), with plantings at a higher density than woodlands in order to achieve a closed canopy. We estimated the total above- and belowground biomass carbon of medium windbreaks to be the average of the low and tall windbreaks (57.1 Mg/ha). The FIA database contains useful information on one-third of the species described in the medium windbreaks. These limited FIA carbon stock data for the species utilized in these systems are comparable to the average biomass carbon of the low and tall windbreaks. We applied an overall width of 3.6m (12 ft) to a single row of the medium windbreak when calculating the area represented by a single row of this system (J. Creque, pers. communication).
Riparian Buffers: We estimate biomass accumulation and stock values at maturity for riparian buffers to be comparable to those for tall windbreaks. In our professional judgment and that of MCP staff (J. Creque, pers. communication), the stock values for riparian buffer plantings are likely to be higher than the mean measurements for native forests, however we have no measured data with which we can confirm that prediction.
Silvopasture: The structure and composition of these systems approximates those of native woodlands (J. Creque, pers. communication). Williams et al. (2011) measured mean aboveground biomass carbon in Mendocino county to be 34 Mg C/ha. Nabuurs et al. (2007) published root:shoot ratios for oak woodlands of 0.35. Based on this we estimate silvopasture biomass carbon stocks at maturity of 46 Mg C/ha. We estimate these systems will achieve peak biomass in approximately 80 years. The FIA database contains useful information on one-third of the silvopasture species, with biomass accumulation rates roughly comparable to published data.
Low Windbreak (6-8’)
Sample planting; double staggered line, where space permits, or single line where space is limited (10’ vs 6’ width). Plants on 6’ centers, double staggered line 3’ apart (preferred). If single line, plant on 3’ centers for rapid closure (limited space conditions). Percentages are illustrative only and should be adjusted per site conditions prior to planting.
Baccharis pilularis 35%
Corylus cornuta californica 10%
Heteromeles arbutifolia 15%
Holodiscus discolor 5%
Lonicera involucrata 5%
Rhamnus californica 10%
Ribes sanguineum 5%
Rubus parviflorus/velutinus/spectabilis/franciscanus 5%
Sambucus nigra cerulea 5%
Vaccinium ovatum 5%
Medium Windbreak (8-20’)
Sample planting: 1st line: low windbreak; 2nd line, 6’ back, medium windbreak, 6’ centers. 3rd line, if desired, staggered, 6’ back.
Acer circinatum 5%
Amelanchier alnifolia 5%
Ceanothus thyrsiflorus 10%
Corylus cornuta californica 5%
Crataegus douglasii/C. suksdorfii 5%
Garrya elliptica 5%
Heteromeles arbutifolia 5%
Myrica californica 35%
Prunus lyonii or Prunus ilicifolia 5%
Rhamnus californica 5%
Sambucus nigra cerulea 5%
Sambucus racemosa 5%
Vaccinium ovatum 5%
Tall Windbreak (20-50’+)
Sample planting: 1st line: low windbreak; 2nd line, 6’ back, medium windbreak, 6’ centers. 3rd line, 10’ back, tall windbreak; 4th line, if desired, medium or 2nd tall windbreak at 10’. Not all of these species will be appropriate on each site; a subset of these is expected to form the basis of each tall windbreak. Note potential use of willow and poplar species as forage.
Cupressus macrocarpa (single line, temporary)
Populus fremontii (forage) (moist sites)
Populus lombardii (forage) (moist sites)
Salix spp. (forage) (moist sites)
Field Borders, Riparian Forest Buffers and Silvopastures. * Indicates field border and silvopastoral species.
Not all of these species will be appropriate on each site; a subset of these is expected to form the basis of each site planting. Field borders will typically be approximately 40 wide; length to be determined by site. Riparian forest buffers will typically cover a 30’ width from top of bank on both sides of the riparian corridor, for a total width of 60 feet or more, depending upon planting within the stream channel. Silvopasture density will not exceed 60% canopy cover at maturity, and will vary by site.
Corylus cornuta californica