Net Carbon Balance Research Articles

Future Wetland Loss in Louisiana Threatens the Carbon Sequestration Potential of the Coastal Habitats

Photo 1. Scientists collecting aboveground biomass in a saline wetland (light green is smooth cordgrass, Spartina alterniflora and dark green are black mangroves, Avicennia germinans) located in coastal Louisiana. Aboveground net primary productivity, soil carbon accumulation rates, and greenhouse gas emissions can be used to estimate the net ecosystem carbon balance of coastal habitats like this saline wetland. Our estimates suggest that existing saline wetland habitats are a net sink of greenhouse gases. Photo credit: The Water Institute of the Gulf. Photo 2. Saline wetland habitat (dominated by black mangroves, Avicennia germinans) and saline open water habitat in coastal area of Louisiana. The 2017 Coastal Master Plan model output projects that at year 2050, the highest area of habitat will be the saline open water. Photo credit: The Water Institute of the Gulf. Photo 3. Fresh forested wetlands (dominated by cypress trees, Taxodium distichum) are commonly observed in the Atchafalaya Basin in the Louisiana coast area. Our net ecosystem carbon balance estimates suggest that existing fresh forested wetland habitats are a net sink of greenhouse gases. Photo credit: The Water Institute of the Gulf. These photographs illustrate the article “Climate Change Mitigation Potential of Louisiana's Coastal Area: Current Estimates and Future Projections” by Baustian, Melissa M, Bingqing Liu, Leland Moss, Alyssa Dausman, and James W. Pahl published in Ecological Applications. https://doi.org/10.1002/eap.2847

Climate change mitigation potential of Louisiana's coastal area: Current estimates and future projections.

Coastal habitats can play an important role in climate change mitigation. As Louisiana implements its climate action plan and the restoration and risk reduction projects outlined in its 2017 Louisiana Coastal Master Plan, it is critical to consider potential greenhouse gas (GHG) fluxes in coastal habitats. This study estimated the potential climate mitigation role of existing, converted, and restored coastal habitats for years 2005, 2020, 2025, 2030, and 2050, which align with the Governor of Louisiana's GHG reduction targets. An analytical framework was developed that considered 1) available scientific data on net ecosystem carbon balance fluxes per habitat and 2) habitat areas projected from modeling efforts used for the 2017 Louisiana Coastal Master Plan to estimate the net GHG flux of coastal area. The coastal area was estimated as net GHG sinks of -38.4 ± 10.6 and - 43.2 ± 12.0 Tg CO2 equivalents (CO2 e) in 2005 and 2020, respectively. The coastal area was projected to remain a net GHG sink in 2025 and 2030, both with and without implementation of Coastal Master Plan projects (means ranged from -25.3 to -34.2 Tg CO2 e). By 2050, with model-projected wetland loss and conversion of coastal habitats to open water due to coastal erosion and relative sea level rise, Louisiana's coastal area was projected to become a net source of greenhouse gas emissions both with and without the Coastal Master Plan projects. However, at year 2050, Louisiana Coastal Master Plan project implementation was projected to avoid the release of +8.8 ± 1.3 Tg CO2 e compared to an alternative with no action. Reduction in current and future stressors to coastal habitats, including impacts from sea level rise, as well as the implementation of restoration projects could help to ensure coastal areas remain a natural climate solution.

Above- and Belowground Biomass Carbon Stock and Net Primary Productivity Maps for Tidal Herbaceous Marshes of the United States

Accurate assessments of greenhouse gas emissions and carbon sequestration in natural ecosystems are necessary to develop climate mitigation strategies. Regional and national-level assessments of carbon sequestration require high-resolution data to be available for large areas, increasing the need for remote sensing products that quantify carbon stocks and fluxes. The Intergovernmental Panel on Climate Change (IPCC) provides guidelines on how to quantify carbon flux using land cover land change and biomass carbon stock information. Net primary productivity (NPP), carbon uptake, and storage in vegetation, can also be used to model net carbon sequestration and net carbon export from an ecosystem (net ecosystem carbon balance). While biomass and NPP map products for terrestrial ecosystems are available, there are currently no conterminous United States (CONUS) biomass carbon stock or NPP maps for tidal herbaceous marshes. In this study, we used peak soil adjusted vegetation index (SAVI) values, derived from Landsat 8 composites, and five other vegetation indices, plus a categorical variable for the CONUS region (Pacific Northwest, California, Northeast, Mid-Atlantic, South Atlantic-Gulf, or Everglades), to model spatially explicit aboveground peak biomass stocks in tidal marshes (i.e., tidal palustrine and estuarine herbaceous marshes) for the first time. Tidal marsh carbon conversion factors, root-to-shoot ratios, and vegetation turnover rates, were compiled from the literature and used to convert peak aboveground biomass to peak total (above- and belowground) biomass and NPP. An extensive literature search for aboveground turnover rates produced sparse and variable values; therefore, we used an informed assumption of a turnover rate of one crop per year for all CONUS tidal marshes. Due to the lack of turnover rate data, the NPP map is identical to the peak biomass carbon stock map. In reality, it is probable that turnover rate varies by region, given seasonal length differences; however, the NPP map provides the best available information on spatially explicit CONUS tidal marsh NPP. This study identifies gaps in the scientific knowledge, to support future studies in addressing this lack of turnover data. Across CONUS, average total peak biomass carbon stock in tidal marshes was 848 g C m−2 (871 g C m−2 in palustrine and 838 g C m−2 in estuarine marshes), and based on a median biomass turnover rate of 1, it is expected that the mean NPP annual flux for tidal marshes is similar (e.g., 848 g C m−2 y−1). Peak biomass carbon stocks in tidal marshes were lowest in the Florida Everglades region and highest in the California regions. These are the first fine-scale national maps of biomass carbon and NPP for tidal wetlands, spanning all of CONUS. These estimates of CONUS total peak biomass carbon stocks and NPP rates for tidal marshes can support regional- and national-scale assessments of greenhouse gas emissions, as well as natural resource management of coastal wetlands, as part of nature-based climate solution efforts.

Priming effects induced by degradable microplastics in agricultural soils

Microplastics (MPs) in farmland soils have the potential to cause environmental and human health risks due to their ubiquitous and persistent nature. Degradable MPs may significantly alter the decomposition of soil organic carbon by the so-called priming effect (PE). However, the amplitude and direction of the PE induced by degradable MPs remain uncertain in farmland soils. In this study, a 56-d laboratory incubation experiment was conducted by adding three types of degradable MPs, i.e., poly-hydroxyalkanoates (PHA), polybutylene succinate (PBS), and polylactic acid (PLA) to three farmland soils planted with strawberry, blueberry, and paddy-rape rotation, respectively. The differences in isotopic values (δ 13C) between soils (−25.30−-27.46‰) and MPs (−11.94−-9.99‰) were used to assess the PE and net carbon balance by the natural 13C isotopic tracing method. We found that the stronger the degradability of MPs, the greater the PE induced. Subsequently, PHA-induced PE was the highest, followed by PBS- and PLA-induced PE corresponding to their biodegradability. Moreover, PHA-induced PE reached an impressive 552−1744%, while PBS- and PLA-induced PE achieved 44−179%, and −29−43% across the above three soils, respectively. Overall, PHA resulted in the highest cumulative PE and the lowest net carbon balance relative to PBS and PLA in all three soils. This study, for the first time, demonstrates that the amplitude of PE is dependent on the degradability of MPs, emphasizing that microbial nitrogen mining may play an important role in driving the PE in the long term due to the nitrogen deficiency of MPs.

Estimating Net Carbon and Greenhouse Gas Balances of Potato and Pea Crops on a Conventional Farm in Western Canada

AbstractQuantifying the emissions of the three main biogenic greenhouse gases (GHGs), carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4), from agroecosystems is crucial. In this study continuous measurements of N2O, and CH4 emissions from potato and pea crops in southwest British Columbia, Canada were made using the eddy‐covariance (EC) technique. Flux footprint analysis, coupled with EC and manual nonsteady state chamber measurements, was used to address the spatial heterogeneity resulting from the field edge at the study site. Flux footprint corrections had a larger effect on N2O fluxes than CO2 fluxes because of a more pronounced difference in N2O fluxes between the crop and edge areas. After flux footprint corrections, the potato and pea crops were both weak CO2 sinks with annual net ecosystem exchange values of −57 ± 9 and −97 ± 16 g C m−2 yr−1, respectively. However, after taking carbon (C) export via crop harvest and C import via seeding into account, the potato crop shifted to being a moderate C source of 284 ± 55 g C m−2 yr−1, while the pea crop became near C neutral, sequestering only 30 ± 26 g C m−2 yr−1. Annual GHG balances, quantified by converting N2O and CH4 to CO2 equivalents as pulse emissions using respective global warming potentials on a 100‐year timescale, were 417 ± 88 and 152 ± 106 g CO2e m−2 yr−1 for the potato and pea crops, respectively, with N2O contributing the largest proportion to annual total GHG balances and outweighing the CO2 uptake from the atmosphere.

Effects of nitrogen and phosphorus fertilization on soil organic matter priming and net carbon balance in alpine meadows

AbstractFertilizers‐induced priming effects of soil organic matter (SOM) decomposition influences net carbon balance and nutrient release. We hypothesize that very strong limitation of plant productivity and microbial activities by nitrogen (N) and phosphorus (P), common in Tibetan meadows, retard SOM decomposition and turnover. Consequently, N and/or P fertilization will induce priming effects of SOM and have implications for carbon balance. Soils from a nine‐year fertilization experiment (N alone, P alone, NP together, and control) from a Tibetan alpine meadow were used to investigate priming effect of SOM and carbon balance after addition of 13C labeled glucose. N and/or P fertilization acidified soil by 0.5 pH unit, decreased SOM content, and increased total and available N, total P. Regardless of fertilization, glucose addition accelerated SOM decomposition with priming effects of 30–60 μg C g−1 soil during 78 days. Alleviation of N and P limitation by N and NP fertilization lowered the priming effect by 17% and 14%, respectively, but P fertilization increased priming effect by 67%. The negative correlation of priming effect intensity with SOM, nitrate or total N, and microbial biomass contents indicated that fertilization‐induced differences in soil N and the microbial community are responsible for the priming effects. Positive correlation of carbon balance with total N and ammonium contents suggested that soil N accounts for carbon sequestration. Therefore, long‐term N and/or P fertilization accelerate SOM decomposition and reduce SOM storage in alpine meadows, of which P fertilization induces the highest priming effect and the lowest SOM storage.

High greenhouse gas emissions after grassland renewal on bog peat soil

Drained agriculturally used peatlands are hotspots for greenhouse gas (GHG) emissions, especially carbon dioxide (CO2) and nitrous oxide (N2O). To reduce GHG emissions and simultaneously maintain intensive grassland use, raising water levels by subsurface irrigation (SI) is controversially discussed. Both, intensive grassland use and installations of SI may require grassland renewal. We investigated an experimental intervention site (INT) (SI target water levels: -0.30 m) and a deeply drained reference site (REF), both intensive grassland on deep bog peat. After installation of the SI system, a mechanical grassland renewal took place at INT. At both sites, CO2 (eddy covariance), N2O and methane (manual closed chamber technique) were measured. Additionally, soil water was analyzed for nitrogen species. Here, we report on the initial year of GHG measurements including grassland renewal and rising water levels. Overall, GHG emissions were strongly influenced by grassland renewal at INT. Despite progressively rising water levels, soil moisture in the upper centimeters was low and thus grass growth was slow, resulting in an almost complete loss of harvest. This resulted in a net ecosystem carbon balance (NECB) of 4.64 ± 1.03 t C ha−1 containing only 0.57 ± 0.09 t C ha−1 harvest at INT, while NECB at REF was 6.08 ± 1.74 t C ha−1 including harvest from five grass cuts. Methane fluxes were negligible at both sites. Nitrous oxide emissions dominated the GHG balance at INT. With 144.5 ± 45.5 kg N2O–N ha–1 a–1, they were much higher than at REF (3.9 ± 3.1 kg N2O–N ha–1 a–1) and any other values published so far. Peak fluxes occurred when nitrate concentrations in soil water were extremely high, soil moisture was increased, and vegetation development was struggling. This study highlights the risk of grassland renewals on peat soils regarding yield losses as well as high GHG emissions.

Effects of farmyard manure application and grassland renovation on net ecosystem carbon balance in a temperate grassland: analysis of 11-year eddy covariance data

Effects of farmyard manure application and grassland renovation on net ecosystem carbon balance in a temperate grassland: analysis of 11-year eddy covariance data

Presence of Access Roads Results in Reduced Growing Season Carbon Uptake in Adjacent Boreal Peatlands

AbstractWe conducted a 2‐year study to examine the impacts of resource access roads on carbon (C) exchange in two forested boreal peatlands (a bog and a fen). Along six transects (perpendicular to the road), at 2, 6, and 20 m from the edge of the road on both sides of the road (RI areas), we measured understory CO2 fluxes bi‐weekly from May to August 2016 and 2017 and compared this to measurements at reference areas at least 50 m from the road. Furthermore, we estimated aboveground biomass and net primary productivity of overstory shrubs and trees and combined that with understory fluxes to estimate annual net ecosystem carbon balance, and road‐induced C emissions. Overall, at the bog, the RI areas were sources of C in both 2016 (89.9 g C m−2 y−1) and 2017 (108.9 g C m−2 y−1) while reference areas were sinks. However, at the fen, both RI areas (−744.7, −310.9 g C m−2 y−1 in 2016 and 2017, respectively) and reference areas were sinks of C. Averaged across both peatlands, the estimated road‐induced C losses were ∼7.97 and 7.40 Mg C for each km of the road in 2016 and 2017, respectively. However, areas connected by culverts showed lower road‐associated impact on C emissions. Therefore, we suggest that industries and infrastructure developers align the road parallel to the local water flow direction, when possible, consider the hydrogeological setting during road design to reduce hydrologic impacts, and increase hydrological flows between up‐ and downstream by adequate culverts.

Net carbon balance study for selected roads in Tenerife, Canary Islands.

Carbon dioxide emissions linked to the transport sector are particularly relevant to islands. The Canary Islands have high level of tourism, with tourists who generally travel in rented vehicles on arrival in the archipelago. In addition, mobility of the local population in the islands is also always growing. Thus, transport is one of the sectors that emits the greatest amount of greenhouse gases. In this sense, the net carbon balance becomes a pioneering study in the framework of management of high-capacity road transport routes and will help plan new strategies, which pursue the neutrality and climate resilience of the road network. It will therefore be possible to design different future scenarios, according to traffic intensities detected, to mitigate their local effects by increasing green areas, which will contribute to greater absorption. This study calculated the carbon footprint linked to vehicles on the three high-capacity roads on the island of Tenerife, as well as the carbon footprint of the public lighting attached to these roads. The absorption of carbon by vegetation planted by the Road Service and the soil located on the margins of the road have also been calculated to explore the possibility of modifying the vegetation, using other types of local shrubs and trees that have a higher absorption factor. The results demonstrate that conifers have the highest absorption factor, the Canary Island pine being the best option in this case. However, it is not always possible to place trees on the roadside, and it is necessary to resort to smaller species. This study concludes that better mobility planning, an increase in electric vehicles, improved energy production from renewable sources, and the promotion and enhancement of absorption capacity of carbon sinks are key in the face of climate change. Integr Environ Assess Manag 2023;19:1023-1030. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Using atmospheric observations to quantify annual biogenic carbon dioxide fluxes on the Alaska North Slope

Abstract. The continued warming of the Arctic could release vast stores of carbon into the atmosphere from high-latitude ecosystems, especially from thawing permafrost. Increasing uptake of carbon dioxide (CO2) by vegetation during longer growing seasons may partially offset such release of carbon. However, evidence of significant net annual release of carbon from site-level observations and model simulations across tundra ecosystems has been inconclusive. To address this knowledge gap, we combined top-down observations of atmospheric CO2 concentration enhancements from aircraft and a tall tower, which integrate ecosystem exchange over large regions, with bottom-up observed CO2 fluxes from tundra environments and found that the Alaska North Slope is not a consistent net source nor net sink of CO2 to the atmosphere (ranging from −6 to +6 Tg C yr−1 for 2012–2017). Our analysis suggests that significant biogenic CO2 fluxes from unfrozen terrestrial soils, and likely inland waters, during the early cold season (September–December) are major factors in determining the net annual carbon balance of the North Slope, implying strong sensitivity to the rapidly warming freeze-up period. At the regional level, we find no evidence of the previously reported large late-cold-season (January–April) CO2 emissions to the atmosphere during the study period. Despite the importance of the cold-season CO2 emissions to the annual total, the interannual variability in the net CO2 flux is driven by the variability in growing season fluxes. During the growing season, the regional net CO2 flux is also highly sensitive to the distribution of tundra vegetation types throughout the North Slope. This study shows that quantification and characterization of year-round CO2 fluxes from the heterogeneous terrestrial and aquatic ecosystems in the Arctic using both site-level and atmospheric observations are important to accurately project the Earth system response to future warming.

Merging Climate Action with Energy Security through CCS—A Multi-Disciplinary Framework for Assessment

Combining biomass-fired power generation with CO2 capture and storage leads to so-called negative CO2 emissions. Negative CO2 emissions can already be obtained when coal is co-fired with biomass in a power plant with CCS technology. The need for bioenergy with CO2 capture and storage has been identified as one of the key technologies to keep global warming below 2 °C, as this is one of the large-scale technologies that can remove CO2 from the atmosphere. According to the definition of bioenergy with CO2 capture and storage, capturing and storing the CO2 originating from biomass, along with the biomass binding with carbon from the atmosphere as it grows, will result in net removal of CO2 from the atmosphere. Another technology option for CO2 removal from the atmosphere is direct air capture. The idea of a net carbon balance for different systems (including bioenergy with CO2 capture and storage, and direct air capture) has been presented in the literature. This paper gives a background on carbon dioxide removal solutions—with a focus on ecology, economy, and policy-relevant distinctions in technology. As presented in this paper, the bioenergy with CO2 capture and storage is superior to direct air capture for countries like Poland in terms of ecological impact. This is mainly due to the electricity generation mix structure (highly dependent on fossil fuels), which shifts the CO2 emissions to upstream processes, and relatively the low environmental burden for biomass acquisition. Nevertheless, the depletion of non-renewable natural resources for newly built bioenergy power plant with CO2 capture and storage, and direct air capture with surplus wind energy, has a similar impact below 0.5 GJ3x/t of negative CO2 emissions. When the economic factors are a concern, the use of bioenergy with CO2 capture and storage provides an economic justification at current CO2 emission allowance prices of around 90 EUR/t CO2. Conversely, for direct air capture to be viable, the cost would need to be from 3 to 4.5 times higher.

Cutting peatland CO2 emissions with water management practices

Abstract. Peat decomposition in managed peatlands is responsible for a decrease of 0.52 GtC yr−1 in global carbon stock and is strongly linked to drainage to improve the agricultural bearing capacity, which increases aeration of the soil. Microbial aerobic decomposition is responsible for the bulk of the net CO2 emission from the soil and could be reduced by wetting efforts or minimizing drainage. However, the effects of rewetting efforts on microbial respiration rate are largely unknown. In this study, we aimed to obtain more process-based understanding of these rewetting effects on peat decomposition by integrating high-quality field measurements and literature relationships with an advanced hydrological modelling approach where soil moisture and temperature are centralized as the main drivers for peat decomposition. In 2020 and 2021, two dairy farming peatlands, where subsoil irrigation and drainage (SSI) was tested against a control situation, were continuously monitored for CO2 fluxes, groundwater table, soil moisture and soil temperature. After successfully representing field hydrology and carbon dynamic measurements within our process-based model, we further explored the effects of rewetting under different weather conditions, water management strategies (raising ditchwater levels and SSI) and hydrological seepage settings. To represent peat carbon dynamics we introduced a methodology to estimate potential aerobic microbial respiration rate, based on potential respiration rate curves for soil temperature and water-filled pore space (WFPS). Measurements show that rewetting with SSI resulted in higher summer groundwater levels, soil temperatures and WFPS. SSI reduced the net ecosystem carbon balance (NECB) by 1.58 ± 0.56 kg CO2 m−2 yr−1 (83 ± 25 %) and 0.66 ± 0.62 kg CO2 m−2 yr−1 (28 ± 15 %) for Assendelft and Vlist respectively in 2020. SSI had a negligible effect in 2021 for both research locations, due to more precipitation, lower temperatures and different SSI management (in Assendelft) as compared to 2020. Simulated rewetting effects were in agreement with measured rewetting effects. Model simulations indicate that raising ditchwater levels always reduces peat respiration rates. Furthermore, we found that the application of SSI (i) reduces yearly peat respiration rates in a dry year and/or with downward hydrological fluxes and (ii) increases peat respiration rates in a wet year and/or when upward groundwater seepage is present. Moreover, combining SSI with high ditchwater levels or pressurizing SSI systems will further reduce peat respiration rates. We show that our process-based approach based on temperature and WFPS soil conditions to determine NECB represents observed variance to a greater extent than empirical relationships that involve average groundwater level observations or simulations. Therefore, we recommend using this kind of approach to estimate the effectiveness of rewetting. When this is not possible, we recommend using mean summer groundwater level instead of mean annual groundwater level as a proxy to estimate NECB. Such relations between mean groundwater levels and NECB are prone to underestimating NECB for SSI parcels.

Effects of Combined Use of Olive Mill Waste Compost and Sprinkler Irrigation on GHG Emissions and Net Ecosystem Carbon Budget under Different Tillage Systems.

Traditional rice (Oryza sativa L.) production by flooding is a source of greenhouse gases (GHG), especially methane. The high consumption of water, as well as the chemical and physical degradation caused by these traditional practices in rice soils, is promoting a decrease in rice production in the Mediterranean area. The aim of this study was to monitor GHG emissions and the net ecosystem carbon balance (NECB) from rice produced with sprinkler irrigation techniques and also assess the impact of olive mill waste compost (C-OW) application and tillage on GHG emissions and the NECB. A field experiment for irrigated rice production was implemented by considering four different treatments: (1) tillage (T); (2) no tillage-direct seeding techniques (DS); (3) application of C-OW followed by tillage (TC); and (4) application of C-OW followed by direct seeding (DSC). The C-OW was only applied in the first year at a dose of 80 Mg ha-1. GHG emissions were monitored over three years in these four treatments in order to estimate the direct (first year) and residual (third year) effects of such practices. The application of C-OW caused an increase of 1.85 times the emission of CO2-C in the TC-DSC compared to the T-DS in the first year. It is noteworthy that the TC treatment was the only one that maintained an emission of CO2-C that was 42% higher than T in the third year. Regardless of the treatments and year of the study, negative values for the cumulative CH4 were found, suggesting that under sprinkler irrigation, CH4 oxidation was the dominant process. A decrease in N2O emissions was observed under direct seeding relative to the tillage treatments, although without significant differences. Tillage resulted in an increase in the global warming potential (GWP) of up to 31% with respect to direct seeding management in the third year, as a consequence of the greater carbon oxidation caused by intensive tillage. DS presented a positive NECB in the accumulation of C in the soil; therefore, it provided a greater ecological benefit to the environment. Thus, under Mediterranean conditions, rice production through a sprinkler irrigation system in combination with direct seeding techniques may be a sustainable alternative for rice crops, reducing their GWP and resulting in a lower carbon footprint. However, the use of C-OW as an organic amendment could increase the GHG emissions from rice fields irrigated by sprinklers, especially under tillage conditions.

Site characteristics determine the effectiveness of tillage and cover crops on the net ecosystem carbon balance in California vineyard agroecosystems.

Globally, wine grape vineyards cover approximately 7.4 M ha. The potential for carbon (C) storage in vineyards is of great interest to offset greenhouse gas emissions and mitigate the effects of climate change. Sustainable soil management practices such as cover crop adoption and reduced tillage may contribute to soil organic carbon (SOC) sequestration. However, site-specific factors such as soil texture, other soil physicochemical properties, and climate largely influence the range and rate to which SOC may be stored. To measure the potential for C storage in vineyards under varying sustainable soil management practices, we calculated the net ecosystem carbon balance (NECB) of three cover crops [perennial grass (Poa bulbosa hybrid cv. Oakville Blue); annual grass (barley, Hordeum vulgare); resident vegetation (natural weed population)] under conventional tillage (CT) and no-till (NT) management. Results provided evidence that vineyards served as C sinks. In sandy soils, the type of cover crop and tillage may be of little influence on the NECB. While in finer-textured soils, tillage reduced the NECB and higher biomass-producing cover crops enhanced the overall C storage potential of the vineyard agroecosystem. Overall, our results revealed that site characteristics, namely, soil texture and climate, were key determinants of the C storage potential of vineyards in Mediterranean climates such as those found in coastal and inland California wine grape production regions.

MASS BALANCE APPROACH AT PALM CARBON CYCLE

Development of Indonesian palm oil industry, not only contributes positively to economic sector. Biggest challenge lies in the negative issues of oil palm development, namely environmental issues. Land use change, forest clearing, deforestation, peat land for palm plantation expansion are environmental issues because they are considered to disturb the balance of greenhouse gases. The use of non-standard fertilizers and POME processing can also increase CO2 emissions, which in turn will reduce carbon storage in vegetation and soil. Soil is the most potent organic carbon sink compared to plants. Soil is an organic carbon pool (reservoir) that accumulates organic carbon in and organic carbon out. The accumulated carbon is influenced by aboveground biomass, belowground biomass, necromass, litter and soil organic matter. So that the development of oil palm is accused of being one of the factors that play a role in soil organic carbon (SOC), soil carbon loss (SCL), net carbon balance (NCB), or greenhouse gasses (GHG) emissions. Where this is a very important component in the palm carbon cycle that has an impact on the global climate. The mass balance approach to the palm carbon cycle obeys the law of conservation of mass. The mass of palm carbon before and after processing is constant. This means that the total mass of palm carbon during the process does not change, only a phase change occurs, namely solid, liquid, and gas.

Relationship between intra-parcel variability and carbon allocation and sequestration in a mature Barbera (Vitis vinifera L.) vineyard ecosystem

In this three year study (2018–2020) we wanted to assess the degree of spatial variability of a small sized (1.2 ha) mature cv. Barbera vineyard managed as alternate permanent native grass and tillage and how such variability interacts, at either single vine and whole vineyard level, with net primary productivity (NPP) and net carbon balance (NCB). Pre-trial an NDVI based vigor map was derived from a satellite image taken at 5 m spatial resolution, and levels of high vigor (HV) and low vigor (LV) were located. Each year ground truthing was performed on test vines chosen within each vigor zone for assessment of vegetative growth, yield components and main compositional parameters at harvest. Samples of each above ground vine organ (leaves, shoot clipping, canes, clusters) and clippings derived from grass mowing were dried in an oven to allow dry biomass assessment. Soil respiration (SR) was also measured at fixed positions each year a few times during the season using a portable gas exchange system and assuring representativeness of either tilled and grassed areas.Vine vigor given as pruning weight vine−1 was 33% higher in HV plots; yet, most of the measured parameters revealed a significant vigor x year interaction which, however, showed a spreading nature meaning that HV vines consistently had higher yield components and malic acid concentration in juice as well as lower total soluble solids (TSS), pH, total anthocyanins and phenols than LV and such differences just varied in magnitude depending on the season. Within a common range of 2.5 to 5.5 kg m − 1 of yield, LV achieved superior quality likely due to reduced vegetative competition, better cluster microclimate and much more constrained berry size.On a per vine basis, NCB confirmed a C sink function with 1.06 kgC vine−1 yr−1, whereas the LV reached only 0.594kgC vine−1 yr−1. These values almost halved at 0.522 and 0.312 kgC vine−1 yr−1 for HV and LV, respectively, when C stored in clusters was subtracted. However, upgrading the NCB to the whole vineyard ecosystem, therefore including the SR contribution, turned the balance into a source mode (i.e. net C release) amounting at 455 and 512 gC m − 2 yr−1 for HV and LV, respectively.Under the specific trial conditions, SR demonstrated to be an overwhelming factor at directing the vineyard NCB into a source mode; the high vigor is indeed more conducive to better C performance as vine and grass biomass is increased. However, it should be taken into account that there is a superior limit beyond which such parameters cannot go if optimal grape maturity parameters need to be assured.

Net Carbon Balance between Priming and Replenishment of Soil Organic Carbon with Biochar Addition Regulated by N Addition Differing in Contrasting Forest Ecosystems

The replenishment and priming effect (PE) are two decisive processes that determine the carbon (C) sequestration potential of biochar. However, how increased nitrogen (N) availability affect these two processes and the consequent net C balance remains poorly understood. By collecting soils from three forest ecosystems (deciduous broad-leaf forest (DBF), evergreen coniferous forest (ECF), and evergreen broad-leaf forest (EBF)), we conducted a 365-day incubation experiment by adding 13C-labelled biochar plus five rates of inorganic N (0 to 15% N of soil total N). The -results showed that N addition significantly stimulated the early period (0–48 days) but did not affect the late period (49–365 days) of biochar decomposition. The effect of N addition on PE varied largely with the forest type and decomposition period; N addition significantly enhanced the negative PE -in both periods in DBF and at the late period in EBF, whereas it stimulated positive PE in the early period in EBF and ECF. At the end of incubation, the addition of biochar caused net C accumulation across all treatments due to the huge proportion of biochar (98.1%–98.9% of added biochar) retained in soils and the negative or neutral cumulative PE (−11.25–0.35 g C kg−1 SOC), and the magnitude of net C balance increased linearly with the N addition rate in DBF and EBF. Collectively, the results of this study indicate that biochar input can contribute to soil C sequestration and that N addition can enhance the C sequestration potential of biochar.

Unraveling the effects of management and climate on carbon fluxes of U.S. croplands using the USDA Long-Term Agroecosystem (LTAR) network

Understanding the carbon fluxes and dynamics from a broad range of agricultural systems has the potential to improve our ability to increase carbon sequestration while maintaining crop yields. Short-term, single-location studies have limited applicability, but long-term data from a network of many locations can provide a broader understanding across gradients of climate and management choices. Here we examine eddy covariance measured carbon dioxide (CO2) fluxes from cropland sites across the United States Department of Agriculture's Long-Term Agroecosystem Research (LTAR) network. The dataset was collected between 2001 and 2020, spanning 13 sites for a total of 182 site-years. Average seasonal patterns of net ecosystem CO2 exchange (NEE), gross primary productivity (GPP), and ecosystem respiration (Reco) were determined, and subsequent regression analysis on these “flux climatologies” was used to identify relationships to mean annual temperature (MAT), mean annual precipitation (MAP), cropping systems, and management practices. At rainfed sites, carbon fluxes were better correlated with MAP (r2 ≤ 0.5) than MAT (r2 ≤ 0.22). Net carbon balance was different among cropping systems (p < 0.001), with the greatest net carbon uptake occurring in sugarcane (Saccharum spp. hybrids) and the least in soybean (Glycine max) fields. Crop type had a greater effect on carbon balance than irrigation management at a Nebraska site. Across cropping systems, grain crops often had higher GPP and were more likely to have net uptake when compared to legume crops. This multi-site analysis highlights the potential of the LTAR network to further carbon flux research using eddy covariance measurements.

Net carbon balance between priming and replenishment of soil organic carbon with biochar addition regulated by N addition differed in contrasting forest ecosystems

Net carbon balance between priming and replenishment of soil organic carbon with biochar addition regulated by N addition differed in contrasting forest ecosystems