QUANTIFYING PEATLAND CARBON DYNAMICS USING MECHANISTICALLY-BASED BIOGEOCHEMISTRY MODELS

This study uses an integrated modeling framework that couples the dynamics of hydrology, soil thermal regime, and ecosystem carbon and nitrogen to quantify the long‐term peat carbon accumulation in Alaska during the Holocene. Modeled hydrology, soil thermal regime, carbon pools and fluxes, and methane emissions are evaluated using observation data at several peatland sites in Minnesota, Alaska, and Canada. The model is then applied for a 10,000 year (15 ka to 5 ka; 1 ka = 1000 cal years before present) simulation at four peatland sites. We find that model simulations match the observed carbon accumulation rates at fen sites during the Holocene (R2 = 0.88, 0.87, 0.38, and −0.05 using comparisons in 500 year bins). The simulated (2.04 m) and observed peat depths (on average 1.98 m) were also compared well (R2 = 0.91). The early Holocene carbon accumulation rates, especially during the Holocene thermal maximum (HTM) (35.9 g C m− 2 yr− 1), are estimated up to 6 times higher than the rest of the Holocene (6.5 g C m− 2 yr− 1). Our analysis suggests that high summer temperature and the lengthened growing season resulted from the elevated insolation seasonality, along with wetter‐than‐before conditions might be major factors causing the rapid carbon accumulation in Alaska during the HTM. Our sensitivity tests indicate that, apart from climate, initial water table depth and vegetation canopy are major drivers to the estimated peat carbon accumulation. When the modeling framework is evaluated for various peatland types in the Arctic, it can quantify peatland carbon accumulation at regional scales.

Sea-level rise enhances carbon accumulation in United States tidal wetlands

Investigations on temporal and spatial variation of slope-scale SOC erosion and deposition

To understand the effects of human activity on accumulation of black carbon in soils, 251 surface soil samples were collected from Zhejiang Province. The soil samples had different land uses, including urban green space, road in urban area, manufacture area, vegetable land in suburban area, upland in countryside, and paddy field in countryside. The contents of black carbon in the samples were characterized by chemical method. The contents of black carbon in the soils ranged from 0 to 15.22 g·kg^-1, and averaged 3.83 g·kg^-1. Most samples (70.92%) had black carbon ranging from 1 to 5 g·kg^-1. Mean contents of black carbon in the soils for different land uses decreased in the sequence of manufacture area > vegetable land in suburban area > road in urban area > upland in countryside area > green space in urban area> paddy field in countryside. Proportion of black carbon in total organic carbon ranged from 0% to 53.20% with mean of 24.83%. The proportion decreased in the sequence of manufacture area > road in urban area > vegetable land in suburban area > urban green space > upland in countryside > paddy field in countryside. Correlation analysis showed that contents of soil black carbon were positively and significantly correlated with its total organic carbon, and the proportions of black carbon in the soil total organic carbon were positively and significantly correlated with their black carbon contents, and insignificantly correlated with the total organic carbon content.

Subsoils play an important role within the global C cycle, since they have high soil organic carbon (SOC) storage capacity due to generally low SOC contents. However, measures for enhancing SOC storage, such as no-tillage, agroforestry and application of animal manure, commonly focus on topsoils. In this dissertation, the option of actively burying SOC-rich soil material through tillage practices was studied for the first time assessing SOC sequestration in deep ploughed arable and forest soils as well as in fossil ridge and furrow cropland under forest with buried topsoils. Assessed deep-ploughed cropland soils contained on average 42±18% more SOC than the reference plots down to 100 cm. In contrast, total SOC stocks in deep ploughed forest soils were not significantly higher than in their respective reference soils. The ‘newly formed’ topsoil of the deep ploughed soils still contained less SOC than the reference topsoil, 14% and 37% under cropland and under forest, respectively. On average, the fraction of mineralised SOC assessed in one-year laboratory incubations, was 32% lower in incubated buried than in reference topsoils. Sandy cropland buried topsoil stripes and reference topsoils had the lowest mineralisable SOC fraction. Buried SOC was partly to fully preserved, most effectively in sandy cropland soils, but selective preservation of certain, most stabile SOC fractions and preferential decomposition of labile fractions, such as the commonly most easily decomposable free light fraction, could not explain SOC stability. Land use history of many of the studied sandy sites as heath was identified as an important aspect concerning SOC stabilisation. Medieval ridge-and-furrow cultivation led to the burial of former topsoil under ridges. SOC content was 0.4-0.9 g kg-1 higher at ridges than at reference positions, indicating long-term preservation of former topsoil SOC by burial under ridges, although enhanced SOC stocks at ridges due to carbon burial could not be significantly confirmed for all sites. In conclusion, deep ploughing led to enhanced subsoil SOC contents and stocks compared to a reference plot in forests and cropland. Deep ploughing increased the storage space for SOC by mechanically translocating topsoil material into the subsoil. SOC accumulation in the new topsoil horizons additionally determine the effect of deep ploughing on full profile SOC stocks.

Carbonate and elemental accumulation rates in arid soils of mid-to-late Pleistocene outwash terraces, southeastern Wind River Range, Wyoming, USA

To provide a theoretical basis for evaluation of the carbon sequestration status of a soil ecosystem in a Castanopsis fargesii forest and for development of a sustainable forestry management strategy in the study region, soil from C. fargesii in Dagangshan, Jiangxi Province was taken as the research object. Using the method of potassium dichromate volumetric and mineralization with a constant indoor temperature of 28℃ and then fitted with a double exponential equation to get the contents of soil organic carbon, soil active carbon and slow-release carbon respectively. Characteristics of spatial and temporal variation for soil organic carbon (SOC), active carbon, and slow-release carbon content were analyzed using one-way ANOVA and multiple comparisons between data using the LSD method. Results showed that the soil organic carbon, slow-release carbon and active carbon contents had the same profile characteristics and accumulated in 0-20 cm surface soil. Compared to April, June, October and December, the interlayer content in August changed significantly (P < 0.05). For a depth of 0-100 cm, the total SOC, active carbon and slow-release carbon content had the same temporal variation characteristics increasing from April to June, reaching a maximum in August, and then decreasing. Conversion of soil slow-release carbon and active carbon from April to June and August to October was strong; soil slow-release carbon content was changed significantly (P < 0.05) and further lead SOC changed significantly in this stage. There was no significant difference in soil active carbon content between the different time. From April to June, the soil active carbon content for 0-20 cm was the fastest growing stage with a rate of increase of 1.30 g·kg-1·month-1, but there was no significant increase in soil active carbon content because of the conversion of active carbon into slow-release carbon and the plum rain season. In general, temporal and spatial changes of total SOC and slow carbon content were more consistent.

The spatial variability of soil organic carbon (SOC) is one of the reasons leading to uncertainty in the estimation of carbon stocks. Simulation and analysis research of SOC spatial distribution, especially the three-dimensional (3D) spatial distribution characteristics, is of great significance for revealing the soil nutrient and pollutant migration, the precise management of farmland and agricultural sustainable development. The 3D spatial distribution pattern of SOC was estimated using 3D ordinary Kriging with regard to the isotropy (3DOKI), 3D ordinary Kriging and 3D CoKriging coupling Markov with regard to anisotropy (3DOKA and 3DCKMA) in the region. Based on estimation results, the paper revealed 3D distribution pattern of regional SOC content. The mean root mean square error (RMSE), relative improvement (RI), the scatter diagram of SOC simulated and measured value and specific value coverage ratio were used to estimate the accuracy of different approaches, and the mean squared deviation ratio (MSDR) and the 3D variogram were used to evaluate model fitting effect and spatial local uncertainty. The results showed that 3D spatial distribution patterns of SOC content for the 3 kinds of estimation methods were basically the same, and the overall spatial distribution pattern was SOC content of the west and the north was higher, and that of the east and the south was relatively low. SOC contents of 5 layers (0-20, >20-40, >40-60, >60-80 and >80-100 cm) were 11.88±5.76, 10.08±4.89, 8.40±5.49, 7.83±5.89 and 7.17±5.22 g/kg, respectively. With the increase of soil depth, the SOC content of the patch gradually reduced. No matter which kind of method, the spatial distribution of SOC in different soil depth was similar, that was, the distribution characteristics of surface layer of the patch were also the embodiment of the deep soil layer. Compared to 3DOKI, the spatial search strategy and its parameters with regard to anisotropy were able to reduce defect (Bovine and central tendency effect) of Kriging method in a certain extent. The RMSE values for 3DOKI, 3DOKA and 3DCKMA were 3.1645, 2.0523 and 1.6215, respectively, so the RMSE value was the minimum for 3DCKAM, whose RI reached nearly 50%. Specific value coverage ratio for 3DOKI, 3DOKA and 3DCKMA were 33.12%, 57.83% and 76.15%, respectively, which was the largest for 3DCKMA method, whose MSDR value (1.4409) was the most close to 1, and variance was the least. The same position CoKriging method coupling Markov was more accurate, and its model fitting effect was the best, and uncertainty was the smallest, which could better highlight the volatility and reflect the specific value. The related research results of this paper will provide method reference for the regional soil properties, and provide technical guidance for the reasonable and scientific research of the spatial distribution pattern of regional SOC. © 2016, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.

Nitrogen addition alters soil organic carbon (SOC) and total nitrogen (TN) accumulation in forest ecosystems, but the responses of SOC and TN sequestration rates and dynamics to nitrogen addition in forest ecosystems worldwide remain unclear. This study conducted a global analysis to evaluate the effects of the nitrogen application rate, nitrogen addition duration (time), and humidity on the SOC and TN accumulation rates from 257 data points (63 articles). Nitrogen addition increased SOC and TN by 4.48% and 10.18%, respectively. The SOC and TN accumulation rates were 0.65 and 0.11 g kg−1 yr−1, respectively. Moreover, the percentage changes of SOC and TN overall increased with the nitrogen application rate and duration of nitrogen addition; however, the accumulation rates of SOC and TN overall decreased with the nitrogen application rate and the duration of nitrogen addition. In addition, the percentage changes and change rates of SOC and TN increased overall with the humidity index. In conclusion, nitrogen addition promoted SOC and TN accumulation in forest soil, and the nitrogen application rate and nitrogen addition duration increased the percentage changes in SOC and TN; however, they decreased the accumulation rate, whereas humidity increased the accumulation rates of SOC and TN. These results enhance our understanding of soil carbon and nitrogen cycling in forest soils in the context of global nitrogen deposition.

Biochar, compost and biochar-compost: effects on crop performance, soil quality and greenhouse gas emissions in tropical agricultural soils

Peat land has specific character, depends on depth of peat and peat decomposition rale.Earthworms has a role in decomposition,carbon cycle, nutrient redistribution, bioturbation and cycle of nutrient.The aim of the research was to identify the population and diversity of earthworms on peat soil in central Kalimantan and to get species of dominant earthworm in peat land.The research was carried out in several peat land use in Basarang and Kalampangan, Central Kalimantan within dry and rainy season.The collection of earthworms was by using hand sorting method. The result showed that population of earthworms on mulch was higher than the deep peat.Land use influenced population and diversity of earthworm. The population and diversity of earthworms were highest on pineapple (shallow peat soil).The dominant species earthworm in peat land was I'omoscolex corethurus.

Latvia is a country with abundant peat resources and intensive peat production. Therefore restoration of more than 17,000 ha abandoned and excavated high bogs are an important issue. Scientific researches are necessary to choose the best way for renovation of peatlands after peat cutting. Along with sufficient freshwater supply this specific nutrient-poor and acid growing environment provides the possibilities for commercial cultivation of American cranberry (Vaccinium macrocarpon) which was successfully started during last 15 years. Today with more than 100 ha of plantings Latvia is fourth major cranberries producing country. In contrast with North America little is known regarding the fertilizing systems of cranberries planted on bare sphagnum peat. Being a native wetland plant, cranberries are nutrients low requiring culture; however, balanced mineral nutrition is vitally essential in producing high and qualitative yield. On the other hand, excessive or inadequate fertilization is potentially detrimental to the environmentally sensitive cranberry growing medium. Investigations were done to find out the actual status and main tendencies in mineral nutrition of American cranberries in Latvia during 2001–2009. Peat samples from 60 different cranberry producing sites established on extracted high bogs were collected over two periods: 2001–2004 and 2005–2009. Additional 20 samples from cutover and natural bogs were analyzed for background level to assess the changes in peat nutrient content during cranberry cultivation. Soil (peat) testing was used to evaluate the cranberry supply with nutrients (N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, Mo, B). Peat analysis revealed serious imbalance in cranberry providing with essential mineral elements. Deficiency of N P, S, Fe, Mn, Zn, Cu, Mo, and B were stated in the majority of samples. Positive tendencies in nutrient status of cranberry peat were found from 2001-2004 to 2005-2009. Mean concentrations increased for P, K, Ca, Mg, Fe, Mn, Cu, B, and become more corresponding to soil standards. Our results revealed significantly higher mean concentrations of P, K, Ca, Mg, S, Fe, and Mn in cultivated cranberry peat to compare with background level, although only P, Ca and Mg contents exceeded maximal levels of these nutrients stated in cutover peatlands. Lack of seriously increased nutrient concentrations in peat samples (only 3% of indices in high levels) indicated that cranberry fertilization practices in Latvia are likely not detrimental to the environment. The present investigation forms the basis for development of on scientific knowledge based cranberry fertilization guidelines in Latvia.

Grasslands in the alpine and subalpine tracts of the Australian southeast occupy a small area but store substantial quantities of soil carbon, which is likely to be affected as climate change shifts the balance between processes of ecosystem carbon import and export. In order to investigate the effects of differences in climate on carbon balance in subalpine grassland ecosystems, eddy covariance instrumentation was established at two climatologically contrasting sites during 2007/08: a cooler, wetter site that sustains winter snow cover (Dargo), and a warmer, drier site that does not (Nimmo). Both were substantial carbon sinks in 2007 and 2008; 93.0 and 111.4gC m ⁻² a ⁻¹ for Dargo, respectively, and 203.8 and 322.0gC m ⁻² a ⁻¹ for Nimmo. Differences in annual carbon uptake were mainly contributed by photosynthetic rather than respiratory fluxes, largely in association with temperature differences, which had two main effects. First, the retention of snow (and associated cessation of photosynthesis) reduced winter gross primary production (GPP) at Dargo. Second, since both sites showed effectively the same temperature-normalised bulk canopy photosynthetic response, GPP was generally lower at the cooler Dargo. Both sites were also subject to drought (severe regional drought conditions during 2006 continued into early 2007), resulting in the observed lower carbon uptake in 2007. The cross-year NEE difference was reduced at Dargo because increased GPP during the wetter summer of 2008 (also observed at Nimmo) was offset by decreased GPP during the cooler winter – and associated longer, later-lying snow season - of 2008. Since the co-occurrence of warm, dry or cool, wet conditions are characteristic of the dominant mode of regional climate variability, ENSO, this suggests that snow cover may moderate the interannual amplitude of NEE variability in these ecosystems. Superimposed on this, however, are expected longer-term changes in carbon storage. Consistent with globally observed soil carbon / climate relationships, soil carbon storage was almost 50% higher at Dargo (19.4kgC m ⁻² ) relative to Nimmo (13.4kgC m ⁻² ). On the basis of such relationships, warming and drying would be expected to result in reductions in soil carbon, particularly at Dargo, where the cool, moist conditions presently limit decomposition and thus maximise storage of labile soil carbon. While losses of soil carbon may be partially offset by the effects of warming on plant growth, both structural limitations on carbon sequestration in grassland vegetation and the slow expected rate of succession towards woody functional plant groups suggest that net carbon losses are likely in coming decades.

This study aimed to elucidate the effects of different fertilization on the accumulation of soil organic carbon (SOC) and the community structure of carbon fixation bacteria in farmland, as well as their carbon sink mechanisms. Four field-based treatments were set up: no fertilizer (CK), organic fertilizer (OF), inorganic fertilizer (CF), and organic-inorganic compound fertilizer (OCF). Differences in soil cbbL bacterial communities, SOC and its component contents, and carbon pool management indices were analyzed using methods such as NMDS, Anosim, and metagenomeSeq tests. The aim was to identify the key differential species under different fertilization treatments, analyze the response relationship between cbbL bacteria communities and SOC and its component content, and clarify the important carbon fixation functional genes. The main findings were as follows: 1) CF and OCF significantly reduced soil cbbL bacterial diversity (p 0.05). Short-term fertilization differences had no significant effect on the carbon pool management index (p>0.05). 3) Compared with cbbL bacterial diversity, the differentially abundant species had a higher contribution to SOC accumulation (83.90%). Among them, Chromatiales significantly affected the active components of SOC and the carbon pool management index (p=0.04). Thiodictyon was a major functional genus under this order that had a significant positive effect on SOC (p=0.034), with the application of organic fertilizer exhibiting a targeted effect, promoting its abundance. The research results have revealed the key pathways for regulating microbial carbon fixation through fertilization, providing a novel theoretical basis and practical targets for carbon fixation and emission reduction in farmland ecosystems. Key words: fertilization type; soil organic carbon; cbbLbacterial community; response relationship; carbon fixation functional genes DOI: 10.25165/j.ijabe.20251806.9970 Citation: Kong C C, Ye H C, Zhang S W, Wang S. Effects of inorganic-organic fertilization schemes on the soil carbon fixation microbial communities and organic carbon accumulation. Int J Agric & Biol Eng, 2025; 18(6): 158–167.

Peatland restoration attempts have been carried out in Indonesia since the early 2000's in response to widespread peatland degradation. Despite the large number of Indonesian peatland restoration projects, little is known about the success of these restoration efforts. Restoration aims to halt soil carbon loss and thus quantification of soil properties is required to assess restoration progress. Mid-infrared (MIR) spectroscopy provides information on carbon functional groups in soil organic matter and when combined with Partial Least Squares Regression (PLSR) analysis, it has been found to offer a more cost-effective method, relative to traditional laboratory methods, to predict a wide range of soil properties in mineral and temperate peat soils. This study aimed to assess the potential of MIR-PLSR to characterise peat soil carbon composition and to develop prediction models of properties of tropical peat soils. Peat samples were collected from five different land uses along a degradation/restoration continuum in Pedamaran peatland, South Sumatra, Indonesia. MIR spectra showed different intensity of signal associated with specific carbon functional groups at different land uses and depths. PLSR analysis revealed reliable predictive models for carbon (R2=0.78, RMSE=2.04, LCCC=0.88, and RPIQ=1.78), nitrogen (R2=0.90, RMSE=0.10, LCCC=0.95, and RPIQ=0.07) and C/N ratio (R2=0.84, RMSE=6.23, LCCC=0.92, RPIQ=3.64). This rapid, low cost spectroscopy method could be appropriate for analysing the large numbers of samples that will be required for large-scale monitoring of soil properties that can indicate the success or progress of Indonesia's peatland restoration interventions.