Soil carbon mineralization in response to nitrogen enrichment in surface and subsurface layers in two land use types

Atmospheric nitrogen (N) deposition increases N availability in soils, with consequences affecting the decomposition of soil carbon (C). The impacts of increasing N availability on surface soil C dynamics are well studied. However, subsurface soils have been paid less attention although more than 50% soil C stock is present below this depth (below 20 cm). This study was designed to investigate the response of surface (0–20 cm) and subsurface (20–40 cm and 40–60 cm) C dynamics to 0 (0 kg N ha−1), low (70 kg N ha−1) and high (120 kg N ha−1) levels of N enrichment. The soils were sampled from a cropland and a grass lawn and incubated at 25 °C and 60% water holding capacity for 45 days. Results showed that N enrichment significantly decreased soil C mineralization (Rs) in all the three soil layers in the two studied sites (p < 0.05). The mineralization per unit soil organic carbon (SOC) increased with profile depth in both soils, indicating the higher decomposability of soil C down the soil profile. Moreover, high N level exhibited stronger suppression effect on Rs than low N level. Rs was significantly and positively correlated with microbial biomass carbon explaining 80% of variation in Rs. Overall; these results suggest that N enrichment may increase C sequestration both in surface and subsurface layers, by reducing C loss through mineralization.

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Implementation of mycorrhizal mechanism into a soil carbon model improves the prediction of long-term processes of plant litter decomposition

10.5194/egusphere-egu21-277 ◽

2021 ◽

Author(s):

Weilin Huang ◽

Peter van Bodegom ◽

Toni Viskari ◽

Jari Liski ◽

Nadejda Soudzilovskaia

Keyword(s):

Soil Carbon ◽

Litter Decomposition ◽

Arbuscular Mycorrhizae ◽

Plant Litter ◽

Climate Impacts ◽

Microbial Interactions ◽

Soil C ◽

Plant Litter Decomposition ◽

C Dynamics

Mycorrhizae, a plant-fungal symbiosis, is an important contributor to below ground-microbial interactions, and hypothesized to play a paramount role in soil carbon (C) sequestration. Ectomycorrhizae (EM) and arbuscular mycorrhizae (AM) are the two dominant forms of mycorrhizae featured by nearly all Earth plant species. However, the difference in the nature of their contributions to the processes of plant litter decomposition is still understood poorly. Current soil carbon models treat mycorrhizal impacts on the processes of soil carbon transformation as a black box. This retards scientific progress in mechanistic understanding of soil C dynamics.We examined four alternative conceptualizations of the mycorrhizal impact on plant litter C transformations, by integrating AM and EM fungal impacts on litter C pools of different recalcitrance into the soil carbon model Yasso15. The best performing concept featured differential impacts of EM and AM on a combined pool of labile C, being quantitatively distinct from impacts of AM and EM on a pool of recalcitrant C.Analysis of time dynamics of mycorrhizal impacts on soil C transformations demonstrated that these impacts are larger at the long-term (>2.5yrs) litter decomposition processes, compared to the short-term processes. We detected that arbuscular mycorrhizae controls shorter term decomposition of labile carbon compounds, while ectomycorrhizae dominate the long term decomposition processes of highly recalcitrant carbon elements. Overall, adding our mycorrhizal module into the Yasso model greatly improved the accuracy of the temporal dynamics of carbon sequestration.A sensitivity analysis of litter decomposition to climate and mycorrhizal factors indicated that ignoring the mycorrhizal impact on the decomposition leads to an overestimation of climate impacts. This suggests that being co-linear with climate impacts, mycorrhizal impacts could be partly hidden within climate factors in soil carbon models, reducing the capability of such models to mechanistically predict impacts of climate vs vegetation change on soil carbon dynamics.Our results provide a benchmark to mechanistic modelling of microbial impacts on soil C dynamics. This work opens new pathways to examining the impacts of land-use change and climate change on plant-microbial interactions and their role in soil C dynamics, allowing the integration of microbial processes into global vegetation models used for policy decisions on terrestrial carbon monitoring.

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Stratifying soils into pedogenically similar categories for modeling forest soil carbon

Canadian Journal of Soil Science ◽

10.4141/cjss07099 ◽

2008 ◽

Vol 88 (4) ◽

pp. 501-516 ◽

Cited By ~ 19

Author(s):

C H Shaw ◽

E. Banfield ◽

W A Kurz

Keyword(s):

Soil Carbon ◽

Forest Soil ◽

Scientific Basis ◽

Soil C ◽

Orthogonal Contrasts ◽

Carbon Modeling ◽

Ecosystem Carbon ◽

C Dynamics ◽

C Stocks ◽

Pedogenic Processes

Most forest ecosystem carbon (C) models are designed to estimate total ecosystem C including soil C stocks and fluxes. Stratification by tree species is often used in these models to reduce uncertainty, but the potential of stratification by soil taxon has received little attention. This potential can be realized only if meaningful modeling strata are identified. Therefore, the objectives of this study were: (a) to distinguish strata of soil C modeling cateogories (SCMC) on the basis of soil C stocks of taxonomic categories that are characterized by similar pedogenic processes important to C dynamics, and (b) to review the literature to test the robustness of the SCMC scheme. Carbon stocks of 1383 forest soil pedons were analyzed by multiple means comparisons for soil orders and by orthogonal contrasts between pedologically related sets of subgroups within soil orders. Eleven SCMCs were distinguished with mean total C stocks varying from 325 ± 37.2 t ha-1 for the gleyed Cryosol SCMC to 94 ± 3.9 t ha-1 for the Brunisolic Gray Luvisol SCMC. A review of the literature relevant to each SCMC demonstrated that there is a scientific basis for using these strata to model forest soil C dynamics. Key words: Forest soil, carbon, modeling, pedology, genesis

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Empirical modelling of plant and soil carbon flux drivers under field conditions

10.5194/egusphere-egu2020-11334 ◽

2020 ◽

Author(s):

Chris McCloskey ◽

Guy Kirk ◽

Wilfred Otten ◽

Eric Paterson

Keyword(s):

Soil Moisture ◽

Soil Temperature ◽

Soil Carbon ◽

Field Conditions ◽

Gas Flux ◽

Soil C ◽

C Dynamics ◽

Plant Respiration ◽

Soil Temperature And Moisture

Our understanding of soil carbon (C) dynamics is limited; field measurements necessarily conflate fluxes from plant and soil sources and we therefore lack long-term field-scale data on soil C fluxes to use to test and improve soil C models. Furthermore, it is often unclear whether findings from lab-based studies, such as the presence of rhizosphere priming, apply to soil systems in the field. It is particularly important that we are able to understand the roles of soil temperature and moisture, and plant C inputs, as drivers of soil C dynamics in order to predict how changing climate and plant productivity may affect the net C balance of soils. We have developed a field laboratory with which to generate much-needed long-term C flux data under field conditions, giving near-continuous measurements of plant and soil C fluxes and their drivers.The laboratory contains 24 0.8-m diameter, 1-m deep, naturally-structured soil monoliths of two contrasting C3 soils (a clay-loam and a sandy soil) in lysimeters. These are sown with a C4 grass (Bouteloua dactyloides), providing a large difference in C isotope signature between C4 plant respiration and C3-origin soil organic matter (SOM) decomposition, which enables clear partitioning of the net C flux. This species is used as a pasture grass in the United States, and regular trimming through the growing season simulates low-intensity grazing. The soil monoliths are fitted with gas flux chambers and connected via an automated sampling loop to a cavity ring-down spectrometer, which measures the concentration and 12C:13C isotopic ratio of CO2 during flux chamber closure. Depth-resolved measurements of soil temperature and moisture in each monolith are made near-continuously, along with measurements of incoming solar radiation, rainfall, and air temperature a the field site. The gas flux chambers are fitted with removable reflective backout covers allowing flux measurements both incorporating, and in the absence of, photosynthesis.We have collected net ecosystem respiration data, measurements of photosynthesis, and recorded potential drivers of respiration over two growing seasons through 2018 and 2019. Through partitioning fluxes between plant respiration and SOM mineralisation we have revealed clear diurnal trends in both plant and soil C fluxes, along with overarching seasonal trends which modify both the magnitude of fluxes and their diurnal patterns. Rates of photosynthesis have been interpolated between measurement periods using machine learning to generate a predictive model, which has allowed us to investigate the effect of plant productivity on SOM mineralisation and assess whether rhizosphere priming can be detected in our system. Through regression analyses and linear mixed effects modelling we have evaluated the roles of soil temperature, soil moisture, and soil N content as drivers of variation in plant and soil respiration in our two contrasting soils. This has shown soil temperature to be the most important control on SOM mineralisation, with soil moisture content playing only a minor role. We have also used our empirical models to suggest how the carbon balance of pasture and grassland soils may respond to warming temperatures.

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Understanding the Complex Interaction Between Soil N Availability and Soil C Dynamics Under Changing Climate Conditions 1

Soil Management and Climate Change ◽

10.1016/b978-0-12-812128-3.00022-7 ◽

2018 ◽

pp. 337-348 ◽

Cited By ~ 3

Author(s):

Pratap Srivastava ◽

Rishikesh Singh ◽

Sachchidanand Tripathi ◽

Hema Singh ◽

Akhilesh Singh Raghubanshi

Keyword(s):

Complex Interaction ◽

N Availability ◽

Soil N ◽

Soil C ◽

Climate Conditions ◽

Soil N Availability ◽

Changing Climate ◽

C Dynamics

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Soil Carbon Mineralization and Microbial Biomass Carbon of In Situ and Exchange-Location Incubation in Forest along Urban-Rural Gradient

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.707.237 ◽

2014 ◽

Vol 707 ◽

pp. 237-242

Author(s):

Rui Lu ◽

Xiao Ying Peng ◽

Ming Quan Yu

Keyword(s):

Microbial Biomass ◽

Soil Carbon ◽

Rural Area ◽

Urban Soils ◽

Microbial Biomass Carbon ◽

Carbon Mineralization ◽

Biomass Carbon ◽

Urban Rural ◽

Soil Carbon Mineralization

Urbanization in high-speed nowadays is changing soil carbon dynamic. Soil carbon mineralization (Cm) and microbial biomass carbon (MBC) of in situ and exchange-location incubation was characterized along urban-rural gradient in Nanchang, China. As a result, soil Cm and MBC of in situ incubation were higher in urban than in suburban, which were significantly higher than those in rural area (P<0.05), at the same time, urban soils incubating in rural area mineralized about 1.8 times the amount of carbon than rural soils incubating in rural area; MBC in soils of exchange-location incubation exhibited a significant decrease tendency with area farther away from urban as well (P<0.05), while there was no significant difference observed in Cm of soils from the same origin incubating in different area between urban, suburban and rural (P>0.05). The result indicated that urban soils have potential for higher losses of carbon than rural soils.

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Contrasting Responses of Soil Respiration Components in Response to Five-Year Nitrogen Addition in a Pinus tabulaeformis Forest in Northern China

Forests ◽

10.3390/f9090544 ◽

2018 ◽

Vol 9 (9) ◽

pp. 544 ◽

Cited By ~ 1

Author(s):

Bo Zhao ◽

Yan Geng ◽

Jing Cao ◽

Lu Yang ◽

Xiuhai Zhao

Keyword(s):

Soil Respiration ◽

Microbial Biomass Carbon ◽

Northern China ◽

Nitrogen Addition ◽

N Deposition ◽

Fine Root Biomass ◽

Pinus Tabulaeformis ◽

N Availability ◽

N Addition ◽

N Enrichment

Increasing atmospheric nitrogen (N) deposition has profound effects on carbon (C) cycling in forest ecosystems. As an important part of belowground C dynamics, soil respiration is potentially affected by changing N availability. However, the responses of total soil respiration (RST) and its three components, soil respiration derived from plant roots (RSR), root-free soil (RSS) and the litter layer (RSL), to such N enrichment remains poorly understood. To assess the effects of N enrichment on soil respiration components, three levels of N addition, namely low (LN, 50 kg N ha−1 year−1), medium (MN, 100 kg N ha−1 year−1) and high (HN, 150 kg N ha−1 year−1), were conducted over five growing seasons from 2011 to 2015 in a temperate Chinese pine (Pinus tabulaeformis) forest in northern China. A control plot without N addition (CK) was also established. The five-year mean annual rate of RST was 2.18 ± 0.43 μmol m−2 s−1, and the contributions of RSR, RSS and RSL were 8.8 ± 3.1%, 82.2 ± 4.5% and 9.0 ± 5.5%, respectively. Compared with CK, RST was significantly increased by 16.5% in the HN plots, but not in the LN or MN treatments. RSS was significantly decreased by 18.1%, 26.6% and 18.4% in the LN, MN and HN plots, respectively, due to the reduction of both microbial biomass carbon (MBC) and enzyme activity. In contrast, RSR was increased by more than twice under the MN treatment, which promoted root growth and activity (higher fine root biomass and N concentration). A significant elevation in RSL was only detected in the HN plots, where the increased litter input enhanced litter decomposition and hence RSL. Our findings clearly demonstrated that N addition of different intensities had different effects on soil components. In particular, the above- and belowground components of heterotrophic respiration, RSL and RSR, showed contrasting responses to high level addition of N. Thus, we highlight that the response of soil respiration components to N addition should be examined individually. Our results may contribute to a better understanding of soil respiration dynamics under future N scenarios, and have important implications in forest management.

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Simulating Grassland Carbon Dynamics in Gansu for the Past Fifty (50) Years (1968–2018) Using the Century Model

Sustainability ◽

10.3390/su13169434 ◽

2021 ◽

Vol 13 (16) ◽

pp. 9434

Author(s):

Meiling Zhang ◽

Stephen Nazieh ◽

Teddy Nkrumah ◽

Xingyu Wang

Keyword(s):

Soil Carbon ◽

Management Practices ◽

Correlation Coefficients ◽

Gansu Province ◽

Century Model ◽

Soil C ◽

Soil Carbon Stock ◽

C Dynamics ◽

Sequestration Rate ◽

Soc Density

China is one of the countries most impacted by desertification, with Gansu Province in the northwest being one of the most affected areas. Efforts have been made in recent decades to restore the natural vegetation, while also producing food. This has implications for the soil carbon sequestration and, as a result, the country’s carbon budget. Studies of carbon (C) dynamics in this region would help to understand the effect of management practices on soil organic carbon (SOC) as well as aboveground biomass (ABVG), and to aid informed decision-making and policy implementation to alleviate the rate of global warming. It would also help to understand the region’s contribution to the national C inventory of China. The CENTURY model, a process-based model that is capable of simulating C dynamics over a long period, has not been calibrated to suit Gansu Province, despite being an effective model for soil C estimation. Using the soil and grassland maps of Gansu, together with weather, soil, and reliable historical data on management practices in the province, we calibrated the CENTURY model for the province’s grasslands. The calibrated model was then used to simulate the C dynamics between 1968 and 2018. The results show that the model is capable of simulating C with significant accuracy. Our measured and observed SOC density (SOCD) and ABVG had correlation coefficients of 0.76 and 0.50, respectively, at p < 0.01. Precipitation correlated with SOCD and ABVG with correlation coefficients of 0.57 and 0.89, respectively, at p < 0.01. The total SOC storage (SOCS) was 436.098 × 106 t C (approximately 0.4356% of the national average) and the average SOCD was 15.75 t C/ha. There was a high ABVG in the southeast and it decreased towards the northwest. The same phenomenon was observed in the spatial distribution of SOCD. Among the soils studied, Hostosols had the highest SOC sequestration rate (25.6 t C/ha) with Gypsisols having the least (7.8 t C/ha). Between 1968 and 2018, the soil carbon stock gradually increased, with the southeast experiencing the greatest increase.

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Short-Term Effect of Nitrogen Fertilization on Carbon Mineralization during Corn Residue Decomposition in Soil

Nitrogen ◽

10.3390/nitrogen2040030 ◽

2021 ◽

Vol 2 (4) ◽

pp. 444-460

Author(s):

Tanjila Jesmin ◽

Dakota T. Mitchell ◽

Richard L. Mulvaney

Keyword(s):

Microbial Biomass ◽

C:N Ratio ◽

Carbon Mineralization ◽

N Fertilization ◽

Co2 Production ◽

Microbial Biomass C ◽

N Availability ◽

Soil C ◽

Residue Decomposition ◽

C And N

The effect of N fertilization on residue decomposition has been studied extensively; however, contrasting results reflect differences in residue quality, the form of N applied, and the type of soil studied. A 60 d laboratory incubation experiment was conducted to ascertain the effect of synthetic N addition on the decomposition of two corn (Zea mays L.) stover mixtures differing in C:N ratio by continuous monitoring of CO2 emissions and periodic measurement of microbial biomass and enzyme activities involved in C and N cycling. Cumulative CO2 production was greater for the high than low N residue treatment, and was significantly increased by the addition of exogenous N. The latter effect was prominent during the first month of incubation, whereas N-treated soils produced less CO2 in the second month, as would be expected due to more rapid substrate depletion from microbial C utilization previously enhanced by greater N availability. The stimulatory effect of exogenous N was verified with respect to active biomass, microbial biomass C and N, and cellulase and protease activities, all of which were significantly correlated with cumulative CO2 production. Intensive N fertilization in modern corn production increases the input of residues but is not conducive to soil C sequestration.

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Long-Term Nitrogen Addition Decreases Soil Carbon Mineralization in an N-Rich Primary Tropical Forest

Forests ◽

10.3390/f12060734 ◽

2021 ◽

Vol 12 (6) ◽

pp. 734

Author(s):

Xiankai Lu ◽

Qinggong Mao ◽

Zhuohang Wang ◽

Taiki Mori ◽

Jiangming Mo ◽

...

Keyword(s):

Microbial Biomass ◽

Organic Carbon ◽

Tropical Forest ◽

Soil Carbon ◽

Tropical Forests ◽

Carbon Mineralization ◽

N Deposition ◽

Soil Carbon Mineralization ◽

N Additions

Anthropogenic elevated nitrogen (N) deposition has an accelerated terrestrial N cycle, shaping soil carbon dynamics and storage through altering soil organic carbon mineralization processes. However, it remains unclear how long-term high N deposition affects soil carbon mineralization in tropical forests. To address this question, we established a long-term N deposition experiment in an N-rich lowland tropical forest of Southern China with N additions such as NH4NO3 of 0 (Control), 50 (Low-N), 100 (Medium-N) and 150 (High-N) kg N ha−1 yr−1, and laboratory incubation experiment, used to explore the response of soil carbon mineralization to the N additions therein. The results showed that 15 years of N additions significantly decreased soil carbon mineralization rates. During the incubation period from the 14th day to 56th day, the average decreases in soil CO2 emission rates were 18%, 33% and 47% in the low-N, medium-N and high-N treatments, respectively, compared with the Control. These negative effects were primarily aroused by the reduced soil microbial biomass and modified microbial functions (e.g., a decrease in bacteria relative abundance), which could be attributed to N-addition-induced soil acidification and potential phosphorus limitation in this forest. We further found that N additions greatly increased soil-dissolved organic carbon (DOC), and there were significantly negative relationships between microbial biomass and soil DOC, indicating that microbial consumption on soil-soluble carbon pool may decrease. These results suggests that long-term N deposition can increase soil carbon stability and benefit carbon sequestration through decreased carbon mineralization in N-rich tropical forests. This study can help us understand how microbes control soil carbon cycling and carbon sink in the tropics under both elevated N deposition and carbon dioxide in the future.

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Soil Carbon Regulating Ecosystem Services in the State of South Carolina, USA

Land ◽

10.3390/land10030309 ◽

2021 ◽

Vol 10 (3) ◽

pp. 309

Author(s):

Elena A. Mikhailova ◽

Hamdi A. Zurqani ◽

Christopher J. Post ◽

Mark A. Schlautman ◽

Gregory C. Post ◽

...

Keyword(s):

South Carolina ◽

Ecosystem Services ◽

Soil Carbon ◽

Soil Depth ◽

State Level ◽

The United States ◽

The State ◽

Soil C ◽

Low Country ◽

Pee Dee

Sustainable management of soil carbon (C) at the state level requires valuation of soil C regulating ecosystem services (ES) and disservices (ED). The objective of this study was to assess the value of regulating ES from soil organic carbon (SOC), soil inorganic carbon (SIC), and total soil carbon (TSC) stocks, based on the concept of the avoided social cost of carbon dioxide (CO2) emissions for the state of South Carolina (SC) in the United States of America (U.S.A.) by soil order, soil depth (0–200 cm), region and county using information from the State Soil Geographic (STATSGO) database. The total estimated monetary mid-point value for TSC in the state of South Carolina was $124.36B (i.e., $124.36 billion U.S. dollars, where B = billion = 109), $107.14B for SOC, and $17.22B for SIC. Soil orders with the highest midpoint value for SOC were: Ultisols ($64.35B), Histosols ($11.22B), and Inceptisols ($10.31B). Soil orders with the highest midpoint value for SIC were: Inceptisols ($5.91B), Entisols ($5.53B), and Alfisols ($5.0B). Soil orders with the highest midpoint value for TSC were: Ultisols ($64.35B), Inceptisols ($16.22B), and Entisols ($14.65B). The regions with the highest midpoint SOC values were: Pee Dee ($34.24B), Low Country ($32.17B), and Midlands ($29.24B). The regions with the highest midpoint SIC values were: Low Country ($5.69B), Midlands ($5.55B), and Pee Dee ($4.67B). The regions with the highest midpoint TSC values were: Low Country ($37.86B), Pee Dee ($36.91B), and Midlands ($34.79B). The counties with the highest midpoint SOC values were Colleton ($5.44B), Horry ($5.37B), and Berkeley ($4.12B). The counties with the highest midpoint SIC values were Charleston ($1.46B), Georgetown ($852.81M, where M = million = 106), and Horry ($843.18M). The counties with the highest midpoint TSC values were Horry ($6.22B), Colleton ($6.02B), and Georgetown ($4.87B). Administrative areas (e.g., counties, regions) combined with pedodiversity concepts can provide useful information to design cost-efficient policies to manage soil carbon regulating ES at the state level.

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