Modeling Experiments for Evaluating the Effects of Trees, Increasing Temperature, and Soil Texture on Carbon Stocks in Agroforestry Systems in Kerala, India

Research Highlights: Agroforestry systems in the humid tropics have the potential for high rates of production and large accumulations of carbon in plant biomass and soils and, thus, may play an important role in the global C cycle. Multiple factors can influence C sequestration, making it difficult to discern the effect of a single factor. We used a modeling approach to evaluate the relative effects of individual factors on C stocks in three agricultural systems in Kerala, India. Background and Objectives: Factors such as plant growth form, management, climate warming, and soil texture can drive differences in C storage among cropping systems, but the relationships among these factors and their effects are complex. Our objective was to use CENTURY, a process-based model of plant–soil nutrient cycling, in an experimental mode to evaluate the effects of individual factors on C stocks in soil and biomass in monocultures (annuals or trees) and agroforestry systems. Materials and Methods: We parameterized the model for this region, then conducted simulations to investigate the effects on C stocks of four experimental scenarios: (1) change in growth form; (2) change in tree species; (3) increase in temperature above 20-year means; and (4) differences in soil texture. We compared the models with measured changes in soil C after eight years. Results: Simulated soil C stocks were influenced by all factors: growth form; lignin in tree tissues; increasing temperature; and soil texture. However, increasing temperature and soil sand content had relatively small effects on biomass C. Conclusions: Inclusion of trees with traits that promoted C sequestration such as lignin content, along with the use of best management practices, resulted in the greatest C storage among the simulated agricultural systems. Greater use and better management of trees with high C-storage potential can thus provide a low-cost means for mitigation of climate warming.

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Reforestation can sequester two petagrams of carbon in US topsoils in a century

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1719685115 ◽

2018 ◽

Vol 115 (11) ◽

pp. 2776-2781 ◽

Cited By ~ 33

Author(s):

Lucas E. Nave ◽

Grant M. Domke ◽

Kathryn L. Hofmeister ◽

Umakant Mishra ◽

Charles H. Perry ◽

...

Keyword(s):

National Level ◽

Mineral Soil ◽

C Sequestration ◽

The United States ◽

Forest Sector ◽

Soil C ◽

C Storage ◽

C Stocks ◽

The Us ◽

Land Use And Management

Soils are Earth’s largest terrestrial carbon (C) pool, and their responsiveness to land use and management make them appealing targets for strategies to enhance C sequestration. Numerous studies have identified practices that increase soil C, but their inferences are often based on limited data extrapolated over large areas. Here, we combine 15,000 observations from two national-level databases with remote sensing information to address the impacts of reforestation on the sequestration of C in topsoils (uppermost mineral soil horizons). We quantify C stocks in cultivated, reforesting, and natural forest topsoils; rates of C accumulation in reforesting topsoils; and their contribution to the US forest C sink. Our results indicate that reforestation increases topsoil C storage, and that reforesting lands, currently occupying >500,000 km2 in the United States, will sequester a cumulative 1.3–2.1 Pg C within a century (13–21 Tg C·y−1). Annually, these C gains constitute 10% of the US forest sector C sink and offset 1% of all US greenhouse gas emissions.

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CARBON STOCKS, LITTERFALL AND PRUNING RESIDUES IN MONOCULTURE AND AGROFORESTRY CACAO PRODUCTION SYSTEMS

Experimental Agriculture ◽

10.1017/s001447971800011x ◽

2018 ◽

Vol 55 (3) ◽

pp. 452-470 ◽

Cited By ~ 4

Author(s):

ULF SCHNEIDEWIND ◽

WIEBKE NIETHER ◽

LAURA ARMENGOT ◽

MONIKA SCHNEIDER ◽

DANIELA SAUER ◽

...

Keyword(s):

Management Practices ◽

Stand Structure ◽

Production Systems ◽

Plant Biomass ◽

Farming Systems ◽

C Sequestration ◽

Agroforestry Systems ◽

Soil C ◽

C Stocks ◽

Pruning Residues

SUMMARYAgroforestry systems (AFS) can serve to decrease ecosystem carbon (C) losses caused by deforestation and inadequate soil management. Because of their shade tolerance, cacao plants are suitable to be grown in AFS, since they can be combined with other kinds of trees and shrubs. The potential for C sequestration in cacao farming systems depends on various factors, such as management practices, stand structure and plantation age. We compared conventionally and organically managed cacao monoculture systems (MCS) and AFS in Sara Ana (Bolivia) with respect to C stocks in plant biomass and to amounts of litterfall and pruning residues. The total aboveground C stocks of the AFS (26 Mg C ha−1) considerably exceeded those of the MCS (~7 Mg C ha−1), although the biomass of cacao trees was greater in the MCS compared to the AFS. Due to higher tree density, annual litterfall in the AFS (2.2 Mg C ha−1 year−1) substantially exceeded that in the MCS (1.2 Mg C ha−1 year−1). The amounts of C in pruning residues (2.6 Mg C ha−1 year−1 in MCS to 4.3 Mg C ha−1 year−1 in AFS) was more than twice those in the litterfall. Annual nitrogen (N) inputs to the soil through pruning residues of cacao and N-fixing trees were up to 10 times higher than the N inputs through external fertiliser application. We conclude that appropriate management of cacao AFS, involving the pruning of leguminous trees, will lead to increases in biomass, litter quantity and quality as well as soil C and N stocks. Thus, we recommend stimulating the expansion of well-managed AFS to improve soil fertility and enhance C sequestration in soils.

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Higher stand densities can promote soil carbon storage after conversion of temperate mixed natural forests to larch plantations

European Journal of Forest Research ◽

10.1007/s10342-020-01346-9 ◽

2020 ◽

Author(s):

Meng Na ◽

Xiaoyang Sun ◽

Yandong Zhang ◽

Zhihu Sun ◽

Johannes Rousk

Keyword(s):

Forest Management ◽

Soil Carbon ◽

Stand Density ◽

C Sequestration ◽

Tree Density ◽

Natural Forests ◽

Soil C ◽

C Storage ◽

Soil C Storage ◽

Soil C Sequestration

AbstractSoil carbon (C) reservoirs held in forests play a significant role in the global C cycle. However, harvesting natural forests tend to lead to soil C loss, which can be countered by the establishment of plantations after clear cutting. Therefore, there is a need to determine how forest management can affect soil C sequestration. The management of stand density could provide an effective tool to control soil C sequestration, yet how stand density influences soil C remains an open question. To address this question, we investigated soil C storage in 8-year pure hybrid larch (Larix spp.) plantations with three densities (2000 trees ha−1, 3300 trees ha−1 and 4400 trees ha−1), established following the harvesting of secondary mixed natural forest. We found that soil C storage increased with higher tree density, which mainly correlated with increases of dissolved organic C as well as litter and root C input. In addition, soil respiration decreased with higher tree density during the most productive periods of warm and moist conditions. The reduced SOM decomposition suggested by lowered respiration was also corroborated with reduced levels of plant litter decomposition. The stimulated inputs and reduced exports of C from the forest floor resulted in a 40% higher soil C stock in high- compared to low-density forests within 8 years after plantation, providing effective advice for forest management to promote soil C sequestration in ecosystems.

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Carbon stocks in Tasmanian soils

Soil Research ◽

10.1071/sr11211 ◽

2012 ◽

Vol 50 (2) ◽

pp. 83 ◽

Cited By ~ 14

Author(s):

W. E. Cotching

Keyword(s):

Management Practices ◽

Agricultural Soils ◽

C Sequestration ◽

Mean Annual Temperature ◽

Soil C ◽

C Stocks ◽

Initial Soil ◽

If Current ◽

Intensive Cropping ◽

The Difference

Soil carbon (C) stocks were calculated for Tasmanian soil orders to 0.3 and 1.0 m depth from existing datasets. Tasmanian soils have C stocks of 49–117 Mg C/ha in the upper 0.3 m, with Ferrosols having the largest soil C stocks. Mean soil C stocks in agricultural soils were significantly lower under intensive cropping than under irrigated pasture. The range in soil C within soil orders indicates that it is critical to determine initial soil C stocks at individual sites and farms for C accounting and trading purposes, because the initial soil C content will determine if current or changed management practices are likely to result in soil C sequestration or emission. The distribution of C within the profile was significantly different between agricultural and forested land, with agricultural soils having two-thirds of their soil C in the upper 0.3 m, compared with half for forested soils. The difference in this proportion between agricultural and forested land was largest in Dermosols (0.72 v. 0.47). The total amount of soil C in a soil to 1.0 m depth may not change with a change in land use, but the distribution can and any change in soil C deeper in the profile might affect how soil C can be managed for sequestration. Tasmanian soil C stocks are significantly greater than those in mainland states of Australia, reflecting the lower mean annual temperature and higher precipitation in Tasmania, which result in less oxidation of soil organic matter.

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Organic soil amendments as a tool to increase biological activity and C sequestration in clay soil

10.5194/egusphere-egu21-11965 ◽

2021 ◽

Author(s):

Jussi Heinonsalo ◽

Anna-Reetta Salonen ◽

Rashmi Shrestha ◽

Subin Kalu ◽

Outi-Maaria Sietiö ◽

...

Keyword(s):

Soil Structure ◽

Soil Amendments ◽

C Sequestration ◽

Organic Soil ◽

Plant Production ◽

Soil C ◽

Soil Microbial ◽

Organic Soil Amendments ◽

C Stocks ◽

Soil C Sequestration

Soil C sequestration through improved agricultural management practices has been suggested to be a cost-efficient tool to mitigate climate change as increased soil C storage removes CO2 from the atmosphere. In addition, improved soil organic carbon (SOC) content has positive impacts on farming though better soil structure and resilience against climate extremes through e.g. better water holding capacity. In some parts of the world, low SOC content is highly critical problem for overall cultivability of soils because under certain threshold levels of SOC, soil loses its ability to maintain essential ecosystem services for plant production. Soil organic amendments may increase soil C stocks, improve soil structure and boost soil microbial activities with potential benefits in plant growth and soil C sequestration. Additional organic substrates may stimulate microbial diversity that has been connected to higher SOC content and healthy soils.We performed a two-year field experiment where the aim was to investigate whether different organic soil amendments have an impact on soil microbial parameters, soil structure and C sequestration.The experiment was performed in Parainen in southern Finland on a clay field where oat (Avena sativa) was the cultivated crop. Four different organic soil amendments were used (two wood-based fiber products that were leftover side streams of pulp and paper industry; and two different wood-based biochars). Soil amendments were applied in 2016. Soil C/N analysis was performed in the autumns 2016-2018 and soil aggregate in the summer and autumn 2018, as well as measures to estimate soil microbial activity: microbial biomass, soil respiration, enzymatic assays, microbial community analysis with Biolog &#174;&#160; EcoPlates and litter bag decomposition experiment. The relative share of bacteria and fungi was determined using qPCR from soil samples taken in the autumns 2016, 2017 and 2018.Data on how the studied organic soil amendments influence soil structure and C content, as well as soil microbial parameters will be presented and discussed.

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Site-level simulations of measurable soil fractions with Millennial Version 2

10.5194/ismc2021-19 ◽

2021 ◽

Author(s):

Rose Abramoff ◽

Bertrand Guenet ◽

Haicheng Zhang ◽

Katerina Georgiou ◽

Xiaofeng Xu ◽

...

Keyword(s):

Meta Analysis ◽

C Sequestration ◽

Current Understanding ◽

Century Model ◽

Mineral Association ◽

Microbial Decomposition ◽

Organic C ◽

Soil C ◽

Soil Fractions ◽

C Stocks

Soil carbon (C) models are used to predict C sequestration responses to climate and land use change. Yet, the soil models embedded in Earth system models typically do not represent processes that reflect our current understanding of soil C cycling, such as microbial decomposition, mineral association, and aggregation. Rather, they rely on conceptual pools with turnover times that are fit to bulk C stocks and/or fluxes. As measurements of soil fractions become increasingly available, soil C models that represent these measurable quantities can be evaluated more accurately. Here we present Version 2 (V2) of the Millennial model, a soil model developed to simulate C pools that can be measured by extraction or fractionation, including particulate organic C, mineral-associated organic C, aggregate C, microbial biomass, and dissolved organic C. Model processes have been updated to reflect the current understanding of mineral-association, temperature sensitivity and reaction kinetics, and different model structures were tested within an open-source framework. We evaluated the ability of Millennial V2 to simulate total soil organic C (SOC), as well as the mineral-associated and particulate fractions, using three soil fractionation data sets spanning a range of climate and geochemistry in Australia (N=495), Europe (N=176), and across the globe (N=730). Millennial V2 (RMSE = 1.98 &#8211; 4.76 kg, AIC = 597 &#8211; 1755) generally predicts SOC content better than the widely-used Century model (RMSE = 2.23 &#8211; 4.8 kg, AIC = 584 &#8211; 2271), despite an increase in process complexity and number of parameters. Millennial V2 reproduces between-site variation in SOC across a gradient of plant productivity, and predicts SOC turnover times similar to those of a global meta-analysis. Millennial V2 updates the conceptual Century model pools and processes and represents our current understanding of the roles that microbial activity, mineral association and aggregation play in soil C sequestration.

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Modelling the potential for soil carbon sequestration using biochar from sugarcane residues in Brazil

Scientific Reports ◽

10.1038/s41598-020-76470-y ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

David Lefebvre ◽

Adrian Williams ◽

Jeroen Meersmans ◽

Guy J. D. Kirk ◽

Saran Sohi ◽

...

Keyword(s):

Greenhouse Gas ◽

Field Experiments ◽

C Sequestration ◽

Saccharum Officinarum ◽

The State ◽

Greenhouse Gas Mitigation ◽

Future Research ◽

Soil C ◽

Full Life Cycle ◽

C Stocks

Abstract Sugarcane (Saccharum officinarum L.) cultivation leaves behind around 20 t ha−1 of biomass residue after harvest and processing. We investigated the potential for sequestering carbon (C) in soil with these residues by partially converting them into biochar (recalcitrant carbon-rich material). First, we modified the RothC model to allow changes in soil C arising from additions of sugarcane-derived biochar. Second, we evaluated the modified model against published field data, and found satisfactory agreement between observed and predicted soil C accumulation. Third, we used the model to explore the potential for soil C sequestration with sugarcane biochar in São Paulo State, Brazil. The results show a potential increase in soil C stocks by 2.35 ± 0.4 t C ha−1 year−1 in sugarcane fields across the State at application rates of 4.2 t biochar ha−1 year−1. Scaling to the total sugarcane area of the State, this would be 50 Mt of CO2 equivalent year−1, which is 31% of the CO2 equivalent emissions attributed to the State in 2016. Future research should (a) further validate the model with field experiments; (b) make a full life cycle assessment of the potential for greenhouse gas mitigation, including additional effects of biochar applications on greenhouse gas balances.

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Continuous and discontinuous variation in ecosystem carbon stocks with elevation across a treeline ecotone

Biogeosciences ◽

10.5194/bg-12-1615-2015 ◽

2015 ◽

Vol 12 (5) ◽

pp. 1615-1627 ◽

Cited By ~ 10

Author(s):

J. D. M. Speed ◽

V. Martinsen ◽

A. J. Hester ◽

Ø. Holand ◽

J. Mulder ◽

...

Keyword(s):

Large Scale ◽

Mineral Soil ◽

Livestock Grazing ◽

Treeline Ecotone ◽

Soil C ◽

C Storage ◽

C Stocks ◽

C Stock ◽

The Impact ◽

Forest Line

Abstract. Treelines differentiate vastly contrasting ecosystems: open tundra from closed forest. Treeline advance has implications for the climate system due to the impact of the transition from tundra to forest ecosystem on carbon (C) storage and albedo. Treeline advance has been seen to increase above-ground C stocks as low vegetation is replaced with trees but decrease organic soil C stocks as old carbon is decomposed. However, studies comparing across the treeline typically do not account for elevational variation within the ecotone. Here we sample ecosystem C stocks along an elevational gradient (970 to 1300 m), incorporating a large-scale and long-term livestock grazing experiment, in the southern Norwegian mountains. We investigate whether there are continuous or discontinuous changes in C storage across the treeline ecotone, and whether these are modulated by grazing. We find that vegetation C stock decreases with elevation, with a clear breakpoint between the forest line and treeline above which the vegetation C stock is constant. C stocks in organic surface horizons of the soil were higher above the treeline than in the forest, whereas C stocks in mineral soil horizons are unrelated to elevation. Total ecosystem C stocks also showed a discontinuous elevational pattern, increasing with elevation above the treeline (8 g m−2 per metre increase in elevation), but decreasing with elevation below the forest line (−15 g m−2 per metre increase in elevation), such that ecosystem C storage reaches a minimum between the forest line and treeline. We did not find any effect of short-term (12 years) grazing on the elevational patterns. Our findings demonstrate that patterns of C storage across the treeline are complex, and should be taken account of when estimating ecosystem C storage with shifting treelines.

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Changes in carbon storage of broadcast burn plantations over 20 years

Canadian Journal of Soil Science ◽

10.4141/s06-012 ◽

2007 ◽

Vol 87 (1) ◽

pp. 93-102 ◽

Cited By ~ 6

Author(s):

J M Kranabetter ◽

A M Macadam

Keyword(s):

Lodgepole Pine ◽

Woody Debris ◽

Mineral Soil ◽

Biomass Accumulation ◽

Prescribed Burn ◽

Soil C ◽

C Storage ◽

C Stocks ◽

Mineral Soils ◽

Forest Floors

The extent of carbon (C) storage in forests and the change in C stocks after harvesting are important considerations in the management of greenhouse gases. We measured changes in C storage over time (from postharvest, postburn, year 5, year 10 and year 20) in logging slash, forest floors, mineral soils and planted lodgepole pine (Pinus contorta var. latifolia) trees from six prescribed-burn plantations in north central British Columbia. After harvest, site C in these pools averaged 139 Mg ha-1, with approximately equal contributions from mineral soils (0–30 cm), forest floors and logging slash. Together these detrital pools declined by 71 Mg C ha-1, or 51% (28% directly from the broadcast burn, and a further 23% postburn), in the subsequent 20 yr. Postburn decay in logging slash was inferred by reductions in wood density (from 0.40 to 0.34 g cm-3), equal to an average k rate of 0.011 yr-1. Losses in forest floor C, amounting to more than 60% of the initial mass, were immediate and continued to year 5, with no reaccumulation evident by year 20. Mineral soil C concentrations initially fluctuated before declining by 25% through years 10 and 20. Overall, the reductions in C storage were offset by biomass accumulation of lodgepole pine, and we estimate these plantations had become a net sink for C before year 20, although total C storage was still less than postharvest levels. Key words: C sequestration, forest floors; coarse woody debris; soil organic matter

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Biochar from sugarcane residues: An overview of its sequestration potential in Sao Paulo, Brazil

10.5194/egusphere-egu2020-2880 ◽

2020 ◽

Author(s):

David Lefebvre ◽

Jeroen Meersmans ◽

Guy Kirk ◽

Adrian Williams

Keyword(s):

Soil Carbon ◽

C Sequestration ◽

Sao Paulo ◽

São Paulo ◽

Soil C ◽

Paulo State ◽

Sequestration Potential ◽

C Stocks ◽

C Stock ◽

Soil C Stock

Harvesting sugarcane (Saccharum officinarum) produces large quantities of biomass residues. We investigated the potential for converting these residues into biochar (recalcitrant carbon rich material) for soil carbon (C) sequestration. We modified a version of the RothC soil carbon model to follow changes in soil C stocks considering different amounts of fresh sugarcane residues and biochar (including recalcitrant and labile biochar fractions). We used Sao Paulo State (Brazil) as a case study due to its large sugarcane production and associated soil C sequestration potential.Mechanical harvesting of sugarcane fields leaves behind > 10 t dry matter of trash (leaves) ha-1 year-1. Although trash blanketing increases soil fertility, an excessive amount is detrimental and reduces the subsequent crop yield. After the optimal trash blanketing amount, sugarcane cultivation still produces 5.9 t C ha-1 year-1 of excess trash and bagasse (processing residues) which are available for subsequent use.The available residues could produce 2.5 t of slow-pyrolysis (550&#176;C) biochar C ha-1 year-1. The model predicts this could increase sugarcane field soil C stock on average by 2.4 &#177; 0.4 t C ha&#8209;1 year&#8209;1, after accounting for the climate and soil type variability across the State. Comparing different scenarios, we found that applying fresh residues into the field results in a smaller increase in soil C stock compared to the biochar because the soil C approaches a new equilibrium. For instance, adding 1.2 t of biochar C ha&#8209;1 year&#8209;1 along with 3.2 t of fresh residue C ha&#8209;1 year&#8209;1 increased the soil C stock by 1.8 t C ha&#8209;1 year&#8209;1 after 10 years of repeated applications. In contrast, adding 0.62 t of biochar C ha&#8209;1 year&#8209;1 with 4.5 t of fresh sugarcane residues C ha&#8209;1 year&#8209;1 increased the soil carbon soil stock by 1.4 t C ha&#8209;1 year&#8209;1 after 10 years of application. These are reductions 25% and 40% of the potential soil C accumulation rates compared with applying available residues as biochar.&#160; &#160;We also tested the sensitivity of the model to biochar-induced positive priming (i.e. increased mineralization of soil organic C) using published values. This showed that the C sequestration balance remains positive over the long term, even considering an extremely high positive-priming factor. Upscaling our results to the total 5 Mha of sugarcane in Sao Paulo State, biochar application could sequester up to 50 Mt of CO2 equivalent per year, representing 31% of the emissions attributed to the State in 2016.This study provides first insights into the sequestration potential of biochar application on sugarcane fields. Measurements of changes in soil C stocks in sugarcane field experiments are needed to further validate the model, and the emissions to implement the practice at large scale need to be taken into account. As the climate crisis grows, the need for greenhouse gas removal technologies becomes crucial. Assessing the net effectiveness of readily available technologies is essential to guide policy makers.&#160;&#160;

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