When Is 2+2 ¿ 4? Interactive Priming Of Pyrogenic Organic Matter, Soil Organic Carbon, And Plant Roots In Natural And Managed Ecosystems

WHEN IS 2+2 ! 4? INTERACTIVE PRIMING OF PYROGENIC ORGANIC MATTER, SOIL ORGANIC CARBON, AND PLANT ROOTS IN NATURAL AND MANAGED ECOSYSTEMS Thea Leslie Whitman, Ph. D. Cornell University Soils hold a globally important stock of carbon (C) and can act as both a C source and sink, depending on management and environmental conditions. Pyrogenic organic matter (PyOM) is produced naturally during fires, and contains relatively stable forms of C. Its intentional production has also been proposed as a mechanism for C management (in such cases PyOM is often referred to as "biochar"). However, the impact of natural or anthropogenic PyOM production on soils is complex and depends on many factors. In particular, the effects of PyOM on existing soil organic C (SOC) dynamics is poorly characterized or understood. Understanding the mechanisms behind these interactions, often referred to as "priming", is essential to predict the impact of PyOM additions to soils. In a greenhouse study, PyOM additions counteracted positive priming of SOC by corn plants, almost completely eliminating net C losses either by decreasing SOC decomposition or increasing corn C additions to soil. This highlights the importance of including plants in studies of PyOM-SOC interactions. In an incubation trial, the relative mineralizability of PyOM as compared to SOC predicted priming interactions, where the soil with lower SOC mineralization was more susceptible to short-term increases in SOC mineralization with PyOM additions, which were proportional to the C mineralization in the added PyOM. Soils also experienced net long-term decreases in SOC mineralization with PyOM additions, possibly due to stabilization of SOC on PyOM surfaces, an example of which we imaged using nanoscale secondary ion mass spectrometry. In a field trial, PyOM additions temporarily increased total soil CO2 fluxes, dramatically less than the addition of fresh corn stover, which likely increased SOC mineralization. Three-part stable isotopic partitioning revealed significantly greater root-derived CO2 fluxes with PyOM additions than without, and significantly lower PyOM-C derived CO2 fluxes when plants were present. PyOM additions only resulted in significant changes to the soil microbial community on day 79, while stover additions induced shifts by day 11. This work informs our understanding of PyOM-soil-plant-microbe interactions and contributes to progress toward a comprehensive predictive framework of PyOM effects on C cycling in soils

Farmer Workshop

Sunday afternoon October 13, 2013 from 1:00 to 4pm, at the New England Small Farm Institute in Belchertown MA (275 Jackson Street) Join fellow farmers and gardeners in an interactive, educational, and highly stimulating presentation/workshop about what biochar is (and is not) along with details about how and why biochar can help you achieve your growing goals. Learn about the many benefits of soil conditioning with biochar, application techniques and amounts, carbon stability, and other practical advice. Rachel Hestrin from Cornell University will deliver a hands on technical presentation and field expert David Yarrow will review his extensive SARE grant trials

Microbial community assembly differs across minerals in a rhizosphere microcosm.

Mineral-associated microbes drive many critical soil processes, including mineral weathering, soil aggregation and cycling of mineral-sorbed organic matter. To investigate the interactions between soil minerals and microbes in the rhizosphere, we incubated three types of minerals (ferrihydrite, kaolinite and quartz) and a native soil mineral fraction near roots of a common Californian annual grass, Avena barbata, growing in its resident soil. We followed microbial colonization of these minerals for up to 2.5 months - the plant's lifespan. Bacteria and fungi that colonized mineral surfaces during this experiment differed across mineral types and differed from those in the background soil, implying that microbial colonization was the result of processes in addition to passive movement with water to mineral surfaces. Null model analysis revealed that dispersal limitation was a dominant factor structuring mineral-associated microbial communities for all mineral types. Once bacteria arrived at a mineral surface, capacity for rapid growth appeared important, as ribosomal copy number was significantly correlated with relative enrichment on minerals. Glomeromycota (a phylum associated with arbuscular mycorrhizal fungi) appeared to preferentially associate with ferrihydrite surfaces. The mechanisms enabling the colonization of soil minerals may be foundational in shaping the overall soil microbiome composition and development of persistent organic matter in soils

Biochar As A Carbon Sequestration Mechanism: Decomposition, Modelling, And Policy

Black carbon, or biochar (BC), has a strong but complex potential as a tool for climate change mitigation, due to its high carbon (C) stability, through its application within specific biomass management systems, and depending on the policy tools necessary to establish it effectively within climate change mitigation projects. The term "black carbon" encompasses a spectrum of materials produced during incomplete combustion, including soot and charcoal, while "biochar" is used to distinguish the material from charcoal created for fuel, and to denote its particular application in C sequestration and emission-reducing projects as a soil amendment. Understanding the influence of production temperature, feedstock, and other initial properties on BC stability is critical for evaluating or managing terrestrial C stocks. This thesis quantifies C loss in BCs produced at 7 different temperatures from 6 different feedstocks as well as the original materials through a 3-year microbial incubation in sand matrices. Carbon losses are interpreted using a number of properties, including Fourier-transformed infra-red spectra. High temperature BCs were characterized by lower volatile and higher fixed C contents and the increasing dominance of aromatic C compounds in increasingly condensed forms. 300°C BCs lost 17.8% more C than 600°C BCs, which did not show significant C losses. It was found that production temperature has a greater influence on 3-year C stability than feedstock, likely due to the different temperature ranges at which different organic compounds are modified by heating. However, the C debt or credit ratio, which takes into account the C losses from the original feedstock that are incurred upon charring, is highly sensitive to feedstock type. Corn BCs attained ratios of 2.29-2.81, while no oak or pine chars reached the "break-even ratio" of 1 after 3 years. The introduction of cook stoves that produce BC as well as heat for cooking into small farm households in western Kenya is an example of a specific system in which BC production could be applied. System dynamics modelling was used to: (i) investigate the climate change impact of prototype and refined BC-producing pyrolytic cook stoves and improved combustion cook stoves in comparison to conventional cook stoves; (ii) assess the relative sensitivity of the stoves to key parameters; (iii) quantify the effects of different climate change impact accounting decisions. Simulated reductions in greenhouse gas (GHG) impact from a traditional 3stone cook stove baseline range between 2.56-4.63 tCO2e/household/year for an improved combustion stove and 2.58-5.80 tCO2e/household/year for the pyrolytic stoves, of which BC directly accounts for 14-50%. The magnitude of these reductions is about twice as sensitive to baseline wood fuel use and the fraction of non-renewable biomass (fNRB) of off-farm wood that is used as fuel as to farm age/soil degradation status or stability of biochar. Reductions in GHG impact decrease if a household must access non-renewable fuel sources. Stoves with higher wood demand are less sensitive to changes in baseline fuel use and rely on biochar for a greater proportion of their reductions. This thesis investigates policy and methodology aspects of BC systems used for carbon management, including the criteria for establishing additionality, baselines, permanence, leakage, system drivers, measurement, verification, economics, and development for successful stand-alone projects and carbon offsets. Findings include that applying baselines of biomass decomposition rather than total soil carbon is effective and supports a longer crediting period than is currently standard. Explicitly designing a BC system around "true wastes" as feedstocks combined with safe system drivers could minimize unwanted land-use impacts and leakage With biochar production introduced into bioenergy systems, under a renewable biomass scenario, the change in emissions increases with higher fuel use, rather than decreasing. Integrating these findings with system-specific analysis and an increased understanding of C stability in BCs should inform the design of effective applied BC systems

Global Climate Change & Biochar

Biochar and Biofuels, Getting the Balance Right - Doris Hamil, NASA Recent studies have confirmed that converting biomass to biochar can have net advantages to the global environment over converting the same biomass to biofuels. This presentation will summarize the conclusions of recent papers describing the situations in which maximizing biochar production is favored over conversion to biofuels. When coproduction of biochar and biofuels is indicated by local conditions, an approach is described to determining the optimum biofuels, production parameters, and fuel-char mix. Biochar and the Priming Effect on SOC – T. Whitman, Cornell University Biochar (BC) plays a critical but poorly understood role in the global carbon cycle. Because it is a highly stable form of carbon compared to the original biomass from which it is produced, its production and management has been proposed as a technology for reducing atmospheric CO2 stocks, which contribute to climate change. However, uncertainties remain regarding the effect of its application on the decomposition rate of existing soil organic carbon (SOC) stocks. BC additions may cause SOC to decompose at a different rate than it would without the BC application – an effect termed “priming”. We aim to determine whether the relative amounts of labile SOC and dissolved BC (DBC) can be used to predict the magnitude and direction of “priming” in a soil system. This study will investigate potential mechanisms for short-term priming in a 5-week incubation study. The BC is produced at 325°C from 13C-labelled maple twigs, which will facilitate distinguishing the source of soil CO2 emissions using an isotopic partitioning approach. “Labile” SOC levels will be adjusted by incubating soils for varying durations. DBC levels will be adjusted by extracting DBC from bulk BC and then returning it to the bulk BC at varying rates. We predict that the greatest negative priming effects will be seen where there is low SOC and high DBC, as DBC may be used preferentially as a substrate by microbes in SOC-limited soils. This research will further understanding of the critical interactions between BC and SOC while also informing policy decisions regarding BC production and application to soils for carbon sequestration. Biochar Impact on Soil related GHG emissions– R. Fidel, Iowa State This research is focused on the relationship between biochar’s properties and biochar’s effect on GHG emissions. Specifically, the biochar chemical properties relevant to biochar-soil interactions will be quantified, and then these properties will be related to changes in GHG emissions that occur following the application of biochar to soil in laboratory incubations and under field conditions. The goals of this project are to (1) quantify the organic and inorganic properties of different biochars and relate these properties to biochar production conditions, (2) quantify the impact of biochar properties on GHG emissions from diverse soils, (3) identify mechanisms by which biochar properties influence GHG emissions from soils, and (4) quantify the effects of biochar amendments, agro-ecosystem diversity and soil type on GHG emissions from soils in the field. This research project will be conducted in three phases: an analysis of biochar properties, a laboratory incubation experiment, and a field study

Contents lists available at ScienceDirect Soil Biology & Biochemistry

journal homepage: www.elsevier.com/locate/soilbio Pyrogenic carbon additions to soil counteract positive priming of soi

1 Supplementary Information

Pyrogenic carbon additions to soil counteract positive priming of soil carbon mineralization by plant