Baseline-Dependent Responses of Soil Organic Carbon Dynamics to Climate and Land Disturbances

Terrestrial carbon (C) sequestration through optimizing land use and management is widely considered a realistic option to mitigate the global greenhouse effect. But how the responses of individual ecosystems to changes in land use and management are related to baseline soil organic C (SOC) levels still needs to be evaluated at various scales. In this study, we modeled SOC dynamics within both natural and managed ecosystems in North Dakota of the United States and found that the average SOC stock in the top 20 cm depth of soil lost at a rate of 450 kg C ha−1 yr−1 in cropland and 110 kg C ha−1 yr−1 in grassland between 1971 and 1998. Since 1998, the study area had become a SOC sink at a rate of 44 kg C ha−1 yr−1. The annual rate of SOC change in all types of lands substantially depends on the magnitude of initial SOC contents, but such dependency varies more with climatic variables within natural ecosystems and with management practices within managed ecosystems. Additionally, soils with high baseline SOC stocks tend to be C sources following any land surface disturbances, whereas soils having low baseline C contents likely become C sinks following conservation management

Corn Belt soil carbon and macronutrient budgets with projected sustainable stover harvest

Corn (Zea mays L.) stover has been identified as a prime feedstock for biofuel production in the U.S. Corn Belt because of its perceived abundance and availability, but long-term stover harvest effects on regional nutrient budgets have not been evaluated. We defined the minimum stover requirement (MSR) to maintain current soil organic carbon levels and then estimated current and future soil carbon (C), nitrogen (N), phosphorus (P), and potassium (K) budgets for various stover harvest scenarios. Analyses for 2006 through 2010 across the entire Corn Belt indicated that currently, 28 Tg or 1.6 Mgha-1 of stover could be sustainably harvested from 17.95 million hectares (Mha) with N, P, and K removal of 113, 26, and 47 kg ha-1, respectively, and C removal for that period was estimated to be 4.55 MgCha-1. Assuming continued yield increases and a planted area of 26.74 Mha in 2050, 77.4 Tg stover (or 2.4 Mg ha-1) could be sustainably harvested with N, P, and K removal of 177, 37, and 72 kgha-1, respectively, along with C removal of ~6.57 MgCha-1. Although there would be significant variation across the region, harvesting only the excess over the MSR under current fertilization rates would result in a small depletion of soil N (- 5 ± 27 kg ha-1) and K (-20 ± 31 kgha-1) and a moderate surplus of P (36 ±18 kgha-1). Our 2050 projections based on continuing to keep the MSR, but having higher yields indicate that soil N and K deficits would become larger, thus emphasize the importance of balancing soil nutrient supply with crop residue removal

Corn Belt soil carbon and macronutrient budgets with projected sustainable stover harvest

Corn (Zea mays L.) stover has been identified as a prime feedstock for biofuel production in the U.S. Corn Belt because of its perceived abundance and availability, but long-term stover harvest effects on regional nutrient budgets have not been evaluated. We defined the minimum stover requirement (MSR) to maintain current soil organic carbon levels and then estimated current and future soil carbon (C), nitrogen (N), phosphorus (P), and potassium (K) budgets for various stover harvest scenarios. Analyses for 2006 through 2010 across the entire Corn Belt indicated that currently, 28 Tg or 1.6 Mgha-1 of stover could be sustainably harvested from 17.95 million hectares (Mha) with N, P, and K removal of 113, 26, and 47 kg ha-1, respectively, and C removal for that period was estimated to be 4.55 MgCha-1. Assuming continued yield increases and a planted area of 26.74 Mha in 2050, 77.4 Tg stover (or 2.4 Mg ha-1) could be sustainably harvested with N, P, and K removal of 177, 37, and 72 kgha-1, respectively, along with C removal of ~6.57 MgCha-1. Although there would be significant variation across the region, harvesting only the excess over the MSR under current fertilization rates would result in a small depletion of soil N (- 5 ± 27 kg ha-1) and K (-20 ± 31 kgha-1) and a moderate surplus of P (36 ±18 kgha-1). Our 2050 projections based on continuing to keep the MSR, but having higher yields indicate that soil N and K deficits would become larger, thus emphasize the importance of balancing soil nutrient supply with crop residue removal

Simulating the effects of management practices on cropland soilorganic carbon changes in the Temperate Prairies Ecoregion of theUnited States from 1980 to 2012

Understanding the effects of management practices on soil organic carbon (SOC) is important for design-ing effective policies to mitigate greenhouse gas emissions in agriculture. In the Midwest United States,management practices in the croplands have been improved to increase crop production and reduce SOCloss since the 1980s. Many studies of SOC dynamics in croplands have been performed to understandthe effects of management, but the results are still not conclusive. This study quantified SOC dynam-ics in the Midwest croplands from 1980 to 2012 with the General Ensemble Biogeochemical ModellingSystem (GEMS) and available management data. Our results showed that the total SOC in the croplandsdecreased from 1190 Tg C in 1980 to 1107 TgC in 1995, and then increased to 1176 TgC in 2012. Contin-uous cropping and intensive tillage may have driven SOC loss in the early period. The increase of cropproduction and adoption of conservation tillage increased the total SOC so that the decrease in the totalSOC stock after 32 years was only 1%. The small change in average SOC did not reflect the large spatialvariations of SOC change in the region. Major SOC losses occurred in the north and south of the region,where SOC baseline values were high and cropland production was low. The SOC gains took place in thecentral part of the region where SOC baseline values were moderate and cropland production was higherthan the other areas. We simulated multiple land-use land-cover (LULC) change scenarios and analyzedthe results. The analysis showed that among all the LULC changes, agricultural technology that increasedcropland production had the greatest impact on SOC changes, followed by the tillage practices, changesin crop species, and the conversions of cropland to other land use. Information on management practiceinduced spatial variation in SOC can be useful for policy makers and farm managers to develop long-termmanagement strategies for increasing SOC sequestration in different areas

Chromosomal DNA deletion confers phage resistance to Pseudomonas aeruginosa.

Bacteria develop a broad range of phage resistance mechanisms, such as prevention of phage adsorption and CRISPR/Cas system, to survive phage predation. In this study, Pseudomonas aeruginosa PA1 strain was infected with lytic phage PaP1, and phage-resistant mutants were selected. A high percentage (~30%) of these mutants displayed red pigmentation phenotype (Red mutant). Through comparative genomic analysis, one Red mutant PA1r was found to have a 219.6 kb genomic fragment deletion, which contains two key genes hmgA and galU related to the observed phenotypes. Deletion of hmgA resulted in the accumulation of a red compound homogentisic acid; while A galU mutant is devoid of O-antigen, which is required for phage adsorption. Intriguingly, while the loss of galU conferred phage resistance, it significantly attenuated PA1r in a mouse infection experiment. Our study revealed a novel phage resistance mechanism via chromosomal DNA deletion in P. aeruginosa

Heavy Metal Distribution and Groundwater Quality Assessment for a Coastal Area on a Chinese Island

Chongming Island is located in the lower Yangtze Estuary in China. Due to the Leachate from a refuse landfill and the hydrodynamics of the Yangtze Estuary, the groundwater environment is particularly complicated on Chongming Island. Field observations were carried out around the landfill disposal site. The groundwater table, temperature, pH, salinity, and dissolved oxygen were measured in the field by portable equipment, and 192 water samples were collected at eight groundwater sites and one surface water site. Through laboratory analysis we found the highest measured concentration of Cr to be 54.07 μg/L, and the measured concentration of Zn was in the range of 8 1.1 μg/L to more than 200 μg/L, which were both higher than their background values. Strong correlations were found between the heavy metal (Cr, Ni, Cu) concentrations and physico-chemical characteristics (salinity and pH), which indicated that both the landfill and the tides played an important role in the distribution of heavy metal concentrations. Both the BM and PoS Indices were greater than their critical values near the disposal site, indicating groundwater pollution by heavy metals. We show that Cr and Ni are the major heavy metals causing groundwater contamination in the study region

Maleic anhydride-modified chicken ovalbumin as an effective and inexpensive anti-HIV microbicide candidate for prevention of HIV sexual transmission

<p>Abstract</p> <p>Background</p> <p>Previous studies have shown that 3-hydroxyphthalic anhydride (HP)-modified bovine milk protein, β-lactoglobulin (β-LG), is a promising microbicide candidate. However, concerns regarding the potential risk of prion contamination in bovine products and carcinogenic potential of phthalate derivatives were raised. Here we sought to replace bovine protein with an animal protein of non-bovine origin and substitute HP with another anhydride for the development of anti-HIV microbicide for preventing HIV sexual transmission.</p> <p>Results</p> <p>Maleic anhydride (ML), succinic anhydride (SU) and HP at different conditions and variable pH values were used for modification of proteins. All the anhydrate-modified globulin-like proteins showed potent anti-HIV activity, which is correlated with the percentage of modified lysine and arginine residues in the modified protein. We selected maleic anhydride-modified ovalbumin (ML-OVA) for further study because OVA is easier to obtain than β-LG, and ML is safer than HP. Furthermore, ML-OVA exhibited broad antiviral activities against HIV-1, HIV-2, SHIV and SIV. This modified protein has no or low <it>in vitro </it>cytotoxicity to human T cells and vaginal epithelial cells. It is resistant to trypsin hydrolysis, possibly because the lysine and arginine residues in OVA are modified by ML. Mechanism studies suggest that ML-OVA inhibits HIV-1 entry by targeting gp120 on HIV-1 virions and also the CD4 receptor on the host cells.</p> <p>Conclusion</p> <p>ML-OVA is a potent HIV fusion/entry inhibitor with the potential to be developed as an effective, safe and inexpensive anti-HIV microbicide.</p

Nose-to-brain delivery of self-assembled curcumin-lactoferrin nanoparticles: Characterization, neuroprotective effect and in vivo pharmacokinetic study

Curcumin (CUR) is a natural polyphenol extract with significant antioxidant and anti-inflammatory effects, which indicates its great potential for neuroprotection. Lactoferrin (LF), a commonly used oral carrier and targeting ligand, has not been reported as a multifunctional nanocarrier for nose-to-brain delivery. This study aims to develop a nose-to-brain delivery system of curcumin-lactoferrin nanoparticles (CUR-LF NPs) and to further evaluate the neuroprotective effects in vitro and brain accumulation in vivo. Herein, CUR-LF NPs were prepared by the desolvation method with a particle size of 84.8 ± 6.5 nm and a zeta potential of +22.8 ± 4.3 mV. The permeability coefficient of CUR-LF NPs (4.36 ± 0.79 × 10−6 cm/s) was 50 times higher than that of CUR suspension (0.09 ± 0.04 × 10−6 cm/s) on MDCK monolayer, indicating that the nanoparticles could improve the absorption efficiency of CUR in the nasal cavity. Moreover, CUR-LF NPs showed excellent protection against Aβ25-35-induced nerve damage in PC12 cells. In vivo pharmacokinetic studies showed that the brain-targeting efficiency of CUR-LF NPs via IN administration was 248.1%, and the nose-to-brain direct transport percentage was 59.7%. Collectively, nose-to-brain delivery of CUR-LF NPs is capable of achieving superior brain enrichment and potential neuroprotective effects

The General Ensemble Biogeochemical Modeling System (GEMS) and its Applications to Agricultural Systems in the United States

The General Ensemble Biogeochemical Modeling System (GEMS) (Liu, 2009; Liu et al., 2004c) was developed to integrate well-established ecosystem biogeochemical models with various spatial databases for the simulations of biogeochemical cycles over large areas. Figure 18.1 shows the overall structure of the GEMS. Some of the key components are described below. General Ensemble Biogeochemical Modeling System (GEMS) 310 Multiple Underlying Biogeochemical Models 310 Monte Carlo Simulations 311 Model Inputs: Management Practices and Others 311 Model Outputs 311 Data Assimilation 311 Simulation of Agricultural Practices: EDCM as an Example 312 Net Primary Production (NPP) and Improvements in Crop Genetics and Agronomics 312 Soil Carbon Dynamics 312 Impacts of Soil Erosion and Deposition 313 CH4 and N2O Fluxes 313 Study Areas and Modeling Design 314 Study Areas 314 Nebraska Eddy Flux Tower Sites 314 Regional Applications: Mississippi Valley and Prairie Potholes 315 Modeling Design 315 Results 316 Impacts of Management Practices on SOC at Site Scale 316 Quantification of Regional Carbon Stocks and GHG Fluxes 317 Prairie Pothole Region 317 Mississippi Valley 319 Discussion 32

Simulated responses of soil organic carbon stock to tillage management scenarios in the Northwest Great Plains

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