Impact of nitrogen input from biosolids application on carbon sequestration in a Pinus radiata forest

Background:Forest management practices(e.g.choice of stand density,fertilisation)are just as important in carbon(C)forestry as in other types of forestry and will affect the level of C sequestration and profitability.Because C stored in wood is approximately proportional to the product of its volume and density,it is necessary to account for both volume growth and wood density when assessing the effects of fertilisation on C sequestration in pine forests.Methods:The effects of nitrogen(N)input from biosolids application on forest C sequestration were quantified from an intensively monitored biosolids field trial in a Pinus radiata plantation on a sandy soil in New Zealand.The field trial tested the application of three biosolids rates:Control(no application),Standard(300 kg N⋅ha^(-1) applied every three years),and High(600 kg N⋅ha^(-1) applied every three years),across three levels of stand density:300,450,and 600 stems⋅ha^(-1).Carbon sequestration was estimated using the C-Change model from annual plot measurements of stand density,stem height and diameter,and annual breast height wood densities obtained from increment cores.Results:By age 24 years,N-fertilised trees had sequestered 40 t C⋅ha^(-1) more than unfertilised trees,an increase of 18%.Fertilisation increased stem volume by 23%but reduced stem wood density by 2.5%.Most of the increased C sequestration occurred between age 6 and age 17 years and the Standard rate gave the same increase in C sequestration as the High rate.On average,there was no significant difference in growth rate between fertilised and unfertilised trees after the 17th growth year,but the increased growth ceased earlier at higher stand densities,and later at lower stand densities.Conclusions:This study indicates that 2–3 applications of the Standard rate would have been sufficient to achieve the increased C sequestration,with an applied N to C conversion ratio of 43–65 kg C⋅kg^(-1) N.Our results highlight that N fertilisation will become more widespread under greenhouse gas emissions trading schemes which en-courages forest management practices that improve C sequestration in young forests in New Zealand in particular and other countries in general.

Assessment on Carbon Sequestration Benefit of Fast-growing and High-yielding Forest Base Construction Program

Fast-growing and High-yielding Forests Base Construction Program is the only industrialization program of six key forestry programs. The main construction content is to plant 13.33 million hm fast-growing and high-yielding plantation in 18 provinces in China. According to the program planning and growth of different tree species, the biomass of this program is evaluated and the C sequestration is assessed in this paper. In the program period, the biomass of the program will reach 3.703 6×109 t, and the C storage will get 1.851 8×109 t. The program will have a great effect on raising the C pool function of forest vegetation.

Land-use induced changes in topsoil organic carbon stock of paddy fields using MODIS and TM/ETM analysis:A case study of Wujiang County,China

Topsoil soil organic carbon (SOC) that plays an important role in mitigating atmospheric carbon dioxide (CO_2) buildup is greatly affected by human activities.To evaluate the influence of land-use changes on SOC stocks in paddy soils,a new algorithm was developed by integrating MODIS (moderate resolution imaging spectral-radiometer) and TM/ETM data for timely monitoring the land-use change in Wujiang County.Thereafter,the land-use class-maps derived from MODIS and TM/ETM analyses were further used to estima...

Litter decomposition and C and N dynamics as affected by N additions in a semi-arid temperate steppe, Inner Mongolia of China

Litter decomposition is the fundamental process in nutrient cycling and soil carbon（C） sequestration in terrestrial ecosystems. The global-wide increase in nitrogen（N） inputs is expected to alter litter decomposition and,ultimately, affect ecosystem C storage and nutrient status. Temperate grassland ecosystems in China are usually N-deficient and particularly sensitive to the changes in exogenous N additions. In this paper, we conducted a 1,200-day in situ experiment in a typical semi-arid temperate steppe in Inner Mongolia to investigate the litter decomposition as well as the dynamics of litter C and N concentrations under three N addition levels（low N with 50 kg N/（hm2？a）（LN）, medium N with 100 kg N/（hm2？a）（MN）, and high N with 200 kg N/（hm2？a）（HN）） and three N addition forms（ammonium-N-based with 100 kg N/（hm2？a） as ammonium sulfate（AS）, nitrate-N-based with 100 kg N/（hm2？a） as sodium nitrate（SN）, and mixed-N-based with 100 kg N/（hm2？a） as calcium ammonium nitrate（CAN）） compared to control with no N addition（CK）. The results indicated that the litter mass remaining in all N treatments exhibited a similar decomposition pattern： fast decomposition within the initial 120 days, followed by a relatively slow decomposition in the remaining observation period（120–1,200 days）. The decomposition pattern in each treatment was fitted well in two split-phase models, namely, a single exponential decay model in phase I（〈398 days） and a linear decay function in phase II（≥398 days）. The three N addition levels exerted insignificant effects on litter decomposition in the early stages（〈398 days, phase I; P〉0.05）. However, MN and HN treatments inhibited litter mass loss after 398 and 746 days, respectively（P〈0.05）. AS and SN treatments exerted similar effects on litter mass remaining during the entire decomposition period（P〉0.05）. The effects of these two N addition forms differed greatly from those of CAN after 746 and 1,053 days, respectively（P〈0.05）. During the decomposition period, N concentrations in the decomposing litter increased whereas C concentrations decreased, which also led to an exponential decrease in litter C：N ratios in all treatments. No significant effects were induced by N addition levels and forms on litter C and N concentrations（P〉0.05）. Our results indicated that exogenous N additions could exhibit neutral or inhibitory effects on litter decomposition, and the inhibitory effects of N additions on litter decomposition in the final decay stages are not caused by the changes in the chemical qualities of the litter, such as endogenous N and C concentrations. These results will provide an important data basis for the simulation and prediction of C cycle processes in future N-deposition scenarios.

Organic Matter Enrichment and Aggregate Stabilization in a Severely Degraded Ultisol After Reforestation

Three types of soils： an eroded barren soil under continuous fallow, an eroded soil transplanted with Lespedeza shrubs （Lespedeza bieolor）, and an eroded soil transplanted with camphor tree （Cinnaraomum camphora） were investigated to quantify organic matter pools and aggregates in reforested soils using physical fractionation techniques and to determine aggregate stability in relation to the enrichment of soil organic carbon （SOC）. Soil organic matter （SOM） was physically fractionalized into free particulate organic matter （fPOM）, occluded particulate organic matter （oPOM）, and mineralassociated organic matter （mOM）. The SOM was concentrated on the surface soil （0 5 cm）, with an average C sequestration rate of 20-25 g C m^-2 year^-1 over 14 years. As compared to the eroded barren land, organic C content of fPOM, oPOM, and mOM fractions of the soil under Lespedeza and under camphor tree increased 12-15, 45-54, and 3.1-3.5 times, respectively. A linear relationship was found between aggregate stability and organic C （r^2 = 0.45, P 〈 0.01）, oPOM （r^2 = 0.34, P 〈 0.05）, and roOM （r^2 = 0.46, P 〈 0.01） of aggregates. The enrichment of organic C improved aggregate stability of the soil under Lespedeza but not that under camphor tree. However, further research is needed on the physical and biological processes involved in the interaction of soil aggregation and SOC sequestration in ecosystem.

Assessing productivity and carbon sequestration capacity of subtropical coniferous plantations using the process model PnET-CN

A generalized, lumped-parameter ecological model PnET-CN was calibrated and validated for a subtropical coniferous plantation in southern China. PnET-CN model describes the biogeochemical cycles of carbon （C） and nitrogen （N） and can assist in estimating carbon sequestration potential. For validation of PnET-CN, data from coniferous forest plantations in southern China was used. Simulated daily gross primary productivity （GPP） from 2005 to 2007 agreed well with observations （R2=0.56, S.D.=0.009）. Simulations of monthly soil respiration （Rs） from 2005-2007 agreed well with Rs observations （R2=0.67, S.D. =0.03）. Simu- lated annual net primary productivity （NPP） from 1998-2006 was 803＋33 gCm 2a-1, about 4% higher than NPP observation （752＋51 gCm-2a-1）. Simulations of annual NEP from 2005-2007 only overestimate 9 gCm-2a-1 （4%）, 4 gCm 2a-1 （1%） and 34 gCm 2a-1 （8%） compared to NEP observations, respectively. Simulated annual foliar N concentration （FolNCon） （1.09%） is 10% lower than observed monthly FolNCon （0.87%-1.58%）. Simulated annual N leaching （0.26 gNm-2） is about 10% lower than leaching observation （0.29 gNm-2）. PnET-CN model validation indicates that PnET-CN is capable to simulate daily GPP, annual NPP, annual NEP, monthly Rs, annual FolNCon and annual nitrate N leaching for subtropical coniferous planta- tions in southern China. The results obtained from the validation test revealed that PnET-CN model can be used to simulate carbon sequestration of planted coniferous forests in southern China to a high level of precision. Sensitivity analysis suggests that great care should be taken in developing generalizations as to how forests will respond to a changing climate. PnET-CN performed satisfactorily in comparison to other models that have already been calibrated and validated in coniferous planted subtropical forests in China. Based on PnET-CN validation and its comparison to other models, future improvement of PnET-CN should focus on seasonal foliar N dynamics and the effects of water stress on autotrophic respirations in subtropical coniferous plantations in southern China.

Soil Enzyme Activities and Organic Matter Composition Affected by 26 Years of Continuous Cropping

The study was to determine the long-term effects of subtropical monoculture and rotational cropping systems and fertilization on soil enzyme activities and soil C, N, and P levels. Cropping systems included continuous sorghum(Sorghum bicolor L.), cotton(Gossypium hirsutum L.), corn(Zea mays L.), and cotton/sorghum rotations after 26 years of treatment imposition. Soil under continuous sorghum and continuous corn had 15% and 11%, respectively, greater C concentrations than soil under continuous cotton.Organic C was 10% higher at 0–7.5 cm than at 7.5–15 cm. Total N followed similar trends with soil depth as organic C. Continuous sorghum had 19% higher total N than other crop species and rotations. With fertilization, continuous cotton had the highest total P at 0–7.5 cm and sorghum had the highest at 7.5–15 cm. Soil total P was 14% higher at 0–7.5 than at 7.5–15 cm, and fertilization increased 15% total P compared to unfertilized soil. Arylsulfatase, alkaline phosphatase, and β-d-glucosidase activity were the highest for sorghum and the lowest for cotton. Rotation increased enzyme activities compared to continuous cotton but not for continuous sorghum. Of all crop species and rotations, continuous cotton generally showed the lowest levels of organic matter and enzyme activities after 26 years. Fertilization significantly increased the yields for all cropping systems, but rotation had no significant effect on either sorghum or cotton lint yield compared to each crop grown in monoculture. Long-term cropping did not increase soil organic matter levels beyond short-term gains, indicating the difficulty in promoting C sequestration in subtropical soils.

Effects of Different Biochars on Pinus elliottii Growth,N Use Efficiency,Soil N_2O and CH_4 Emissions and C Storage in a Subtropical Area of China

Intensive management of planted forests may result in soil degradation and decline in timber yield with successive rotations. Biochars may be beneficial for plant production, nutrient uptake and greenhouse gas mitigation. Biochar properties vary widely and are known to be highly dependent on feedstocks, but their effects on planted forest ecosystem are elusive. This study investigated the effects of chicken manure biochar, sawdust biochar and their feedstocks on 2-year-old Pinus elliottii growth, fertilizer N use efficiency （NUE）, soil N20 and CH4 emissions, and C storage in an acidic forest soil in a subtropical area of China for one year. The soil was mixed with materials in a total of 8 treatments： non-amended control （CK）; sawdust at 2.16 kg m^-2 （SD）; chicken manure at 1.26 kg m^-2 （CM）; sawdust biochar at 2.4 kg m^-2 （SDB）; chicken manure biochar at 2.4 kg m^-2 （CMB）; 15N-fertilizer alone （10.23 atom% 15N） （NF）; sawdust biochar at 2.4 kg m^-2 plus lSN-fertilizer （SDBN） and chicken manure biochar at 2.4 kg m^-2 plus 15N-fertilizer （CMBN）. Results showed that the CMB treatment increased P. elliottii net primary production （aboveground biomass plus litterfall） and annual net C fixation （ANCF） by about 180% and 157%, respectively, while the the SDB treatment had little effect on P. eUiottii growth. The 15N stable isotope labelling technique revealed that fertilizer NUE was 22.7% in CK, 25.5% in the NF treatment, and 37.0% in the CMB treatment. Chicken manure biochar significantly increased soil pH, total N, total P, total K, available P and available K. Only 2% of the N in chicken manure biochar was available to the tree. The soil N20 emission and CH4 uptake showed no significant differences among the treatments. The apparent C losses from the SD and CM treatments were 35% and 61%, respectively; while those from the CMB and SDB treatments were negligible. These demonstrated that it is crucial to consider biochar properties while evaluating their effects on plant growth and C sequestration.

Modeling Carbon Dynamics in Paddy Soils in Jiangsu Province of China with Soil Databases Differing in Spatial Resolution

A number of process-based models have been developed for quantifying carbon(C)sequestration in agro-ecosystems.The DeNitrification-DeComposition(DNDC)model was used to simulate and quantify long-term(1980-2008)soil organic carbon(SOC)dynamics in the important rice-producing province,Jiangsu,China.Changes in SOC storages were estimated from two soil databases differing in spatial resolution:a county database consisting of 68 polygons and a soil patch-based database of 701 polygons for all 3.7 Mha of rice fields in Jiangsu.The simulated SOC storage with the coarse resolution county database ranged between 131.0-320.6 Tg C in 1980 and 170.3-305.1 Tg C in 2008,respectively,while that estimated with the fine resolution database was 201.6 and 216.2 Tg C in 1980 and 2008,respectively.The results modeled with the soil databases differing in spatial resolution indicated that using the soil input data with higher resolution substantially increased the accuracy of the modeled results;and when lacking detailed soil datasets,the DNDC model,parameterized with the most sensitive factor(MSF) method to cope with attribute uncertainty,could still produce acceptable results although with deviations of up to 60% for the case study reported in this paper.

Feeding Biochar to Cows:An Innovative Solution for Improving Soil Fertility and Farm Productivity

Addition of biochar produced through thermal decomposition of biomass has been seen as a strategy to improve soils and to sequester carbon （C）, but wide scale implementation of the technology requires to devise innovative profitable solutions. To develop biochar utilisation with an integrated system approach, an innovative program was implemented in 2012 on a 53-ha farm in Western Australia to determine the costs and benefits of integrating biochar with animal husbandry and improvement of pastures. Biochar was mixed with molasses and fed directly to cows. The dung-biochar mixture was incorporated into the soft profile by dung beetles. We studied the changes in soil properties over 3 years. Biochar extracted from fresh dung and from the soil to a depth of 40 cm was characterised. A preliminary financial analysis of the costs and benefits of this integrated approach was also undertaken. The preliminary investigation results suggested that this strategy was effective in improving soil properties and increasing returns to the farmer. It was also concluded that the biochar adsorbed nutrients from the cow＇s gut and from the dung. Dung beetles could transport this nutrient-rich biochar into the soil profile. There was little evidence that the recalcitrant component of the biochar was reduced through reactions inside the gut or on/in the soil. Further research is required to quantify the long-term impact of integrating biochar and dung beetles into the rearing of cows.

Soil Carbon and Nitrogen in Response to Perennial Bioenergy Grass, Cover Crop and Nitrogen Fertilization

Cover crop and nitrogen （N） fertilization may maintain soil organic matter under bioenergy perennial grass where removal of aboveground biomass for feedstock to produce cellulosic ethanol can reduce soil quality. We evaluated the effects of cover crops and N fertilization rates on soil organic carbon （C） （SOC）, total N （STN）, ammonium N （NH4-N）, and nitrate N （NO3-N） contents at the 0-5, 5-15, and 15-30 cm depths under perennial bioenergy grass from 2010 to 2014 in the southeastern USA. Treatments included unbalanced combinations of perennial bioenergy grass, energy cane （Saccharum spontaneum L.） or elephant grass （Pennisetum pur- pureum Schumazh.）, cover crop, crimson clover （Trifolium incarnatum L.）, and N fertilization rates （0, 100, and 200 kg N ha-l）. Cover crop biomass and C and N contents were greater in the treatment of energy cane with cover crop and 100 kg N ha-1 than in the treatment of energy cane and elephant grass. The SOC and STN contents at 0-5 and 5-15 cm were 9%-20% greater in the treatments of elephant grass with cover crop and with or without 100 kg N ha-1 than in most of the other treatments. The soil NO3-N content at 0--5 cm was 31%-45% greater in the treatment of energy cane with cover crop and 100 kg N ha-1 than in most of the other treatments. The SOC sequestration increased from 0.1 to 1.0 Mg C ha-1 year-1 and the STN sequestration from 0.03 to 0.11 Mg N ha-1 year-1 from 2010 to 2014 for various treatments and depths. In contrast, the soil NH4-N and NO3-N contents varied among treatments, depths, and years. Soil C and N storages can be enriched and residual NO3-N content can be reduced by using elephant grass with cover crop and with or without N fertilization at a moderate rate.

Interactive effects of elevated CO2 and nitrogen fertilization levels on photosynthesized carbon allocation in a temperate spring wheat and soil system

Increasing atmospheric CO2 concentration impacts the terrestrial carbon(C) cycle by affecting plant photosynthesis, the flow of photosynthetically fixed C belowground, and soil C pool turnover. For managed agroecosystems, how and to what extent the interactions between elevated CO2 and N fertilization levels influence the accumulation of photosynthesized C in crops and the incorporation of photosynthesized C into arable soil are in urgent need of exploration.We conducted an experiment simulating elevated CO2 with spring wheat(Triticum aestivum L.) planted in growth chambers.13C-enriched CO2 with an identical 13C abundance was continuously supplied at ambient and elevated CO2 concentrations(350 and 600 μmol mol-1, respectively) until wheat harvest.Three levels of N fertilizer application(equivalent to 80, 120, and 180 kg N ha-1 soil) were supplied for wheat growth at both CO2 concentrations. During the continuous 62-d 13CO2 labeling period, elevated CO2 and increased N fertilizer application increased photosynthesized C accumulation in wheat by 14%–24% and 11%–20%, respectively, as indicated by increased biomass production, whereas the C/N ratio in the roots increased under elevated CO2 but declined with increasing N fertilizer application levels. Wheat root deposition induced 1%–2.5% renewal of soil C after 62 d of 13CO2 labeling. Compared to ambient CO2, elevated CO2 increased the amount of photosynthesized C incorporated into soil by 20%–44%. However, higher application rates of N fertilizer reduced the net input of root-derived C in soil by approximately 8% under elevated CO2. For the wheat-soil system, elevated CO2 and increased N fertilizer application levels synergistically increased the amount of photosynthesized C. The pivotal role of plants in photosynthesized C accumulation under elevated CO2 was thereby enhanced in the short term by the increased N application. Therefore, robust N management could mediate C cycling and sequestration by influencing the interactions between plants and soil in agroecosystems under elevated CO2.

Biochar addition to vineyard soils:effects on soil functions,grape yield and wine quality

In response to increasing concerns over climate change,soil health and wine quality,grape growers are seeking new practices(e.g.,biochar application)to minimize their environmental footprint while increasing productivity and the quality of their products.To explore the potential of biochar-based amendments to achieve these goals in wine grape production,vineyard trials were established in the fall of 2018.Two Oregon sites were chosen with distinct soil types and climates(Willamette Valley and Rogue Valley)but planted with the same grapevine scion/rootstock Pinot noir combination.Four treatments were applied under vines at each location:no biochar-no tillage(NT);no biochar+tillage(B0);18 tons ha^(−1)biochar+tillage(B18);35 tons ha^(−1)biochar+tillage(B35).In 2019,a suite of soil health,plant,and crop variables were measured,and wines were produced after harvest.The incorporation of biochar modified the chemical and physical composition of soils at the two studied locations,increasing the bioavailability of carbon and nitrogen,their gravimetric water content and the concentration of plant available micro and macro nutrients.No responses of plant physiology parameters or productivity at either site were found after biochar incorporation when compared with controls.Conversely,a significant and gradual decrease in the amount of wine tannins was found as a result of biochar application in wines produced from grapes from the Woodhall location.Long-term field experiments are required to assess the effects of biochar on soil properties,vine physiol-ogy,productivity,and grape and wine quality several years after incorporation.

Modeling mass transfer of CO_2 in brine at high pressures by chemical potential gradient

To investigate long-term CO2 behavior in geological formations and quantification of possible CO2 leaks, it is crucial to inves- tigate the potential mobility of CO2 dissolved in brines over a wide range of spatial and temporal scales and density distribu- tions in geological media. In this work, the mass transfer of aqueous CO2 in brines has been investigated by means of a chemi- cal potential gradient model based on non-equilibrium thermodynamics in which the statistical associating fluid theory equa- tion of state was used to calculate the fugacity coefficient of CO2 in brine. The investigation shows that the interracial concen- tration of aqueous CO2 and the corresponding density both increase with increasing pressure and decreasing temperature; the effective diffusion coefficients decrease initially and then increase with increasing pressure; and the density of the CO2-disolved brines increases with decreasing CO2 pressure in the CO2 dissolution process. The aqueous CO2 concentration profiles obtained by the chemical potential gradient model are considerably different from those obtained by the concentration gradient model, which shows the importance of considering non-ideality, especially when the pressure is high.