Biochar affects soil organic matter cycling and microbial functions but does not alter microbial community structure in a paddy soil

The application of biochar (BC) in conjunction with mineral fertilizers is one of the most promising management practices recommended to improve soil quality. However, the interactive mechanisms of BC and mineral fertilizer addition affecting microbial communities and functions associated with soil organic matter (SOM) cycling are poorly understood. We investigated the SOM in physical and chemical fractions, microbial community structure (using phospholipid fatty acid analysis, PLFA) and functions (by analyzing enzymes involved in C and N cycling and Biolog) in a 6-year field experiment with BC and NPK amendment. BC application increased total soil C and particulate organic C for 47.4-50.4% and 63.7-74.6%, respectively. The effects of BC on the microbial community and C-cycling enzymes were dependent on fertilization. Addition of BC alone did not change the microbial community compared with the control, but altered the microbial community structure in conjunction with NPK fertilization. SOM fractions accounted for 55% of the variance in the PLFA-related microbial community structure. The particulate organic N explained the largest variation in themicrobial community structure. Microbial metabolic activity strongly increased after BC addition, particularly the utilization of amino acids and amines due to an increase in the activity of proteolytic (L-leucine aminopeptidase) enzymes. These results indicate that microorganisms start to mine N from the SOM to compensate for high C:N ratios after BC application, which consequently accelerate cycling of stable N. Concluding, BC in combination with NPK fertilizer application strongly affected microbial community composition and functions, which consequently influenced SOM cycling. (C) 2016 Elsevier B.V. All rights reserved

Identification of nitrate source using isotopic and geochemical data in the lower reaches of the Yellow River irrigation district (China)

Nitrate contamination in both surface water and groundwater has received considerable attentions in irrigated agricultural areas. Nitrate concentrations, and its nitrogen and oxygen isotopic compositions, as well as oxygen and deuterium isotopic compositions and chloride concentrations of surface water and groundwater from a typical area in the lower reaches of the Yellow River irrigation district were analyzed to ascertain spatial variations of nitrate and its possible sources and transformations. The results of this study showed nitrate in the Yellow River mainly derived from mineralization of organic matter in sediments and nitrification of atmospheric deposition, and nitrate in other important tributaries were greatly affected by agricultural activities, especially synthetic fertilizer. Nitrate in irrigation canals which go through concentrated residential zone mainly originated from domestic effluent and experienced nitrification. Nitrate in groundwater is not only affected by surface nitrate sources, but also closely related to hydraulic conditions which make nitrate source discrimination more complex. In areas belonging to the Yellow River basin with shallow water tables, nitrate is mainly derived from synthetic fertilizer, and denitrification processes controlled nitrate isotopic compositions in extremely shallow groundwater with low hydraulic gradients. While in places belonging to the Haihe River basin with deep water table, groundwater nitrate is largely affected by mixing process of irrigation water. The main sources of nitrate in groundwater are manure and sewage and soil organic matter, while chemical fertilizer and atmospheric deposition in large amount of rainfall are its minor contributors

Potential impact of land use change on ecosystem services in China

Land use change can greatly alter spatial pattern and overall ecosystem service values (ESV). The goal of this study was to explore the likely effects of land use change on ESV in China. In this paper, the spatially explicit land use changes across China from 2010 to 2020 under the 2000s trend scenario and the planning scenario were projected using the Dyna-CLUE model. The ESV evaluation method was improved by adjusting the ESV coefficients using biomass data to reduce the generalization error of proxy-based method. The results revealed that between 2010 and 2020, total ESVincreased by 1798 and 2215 billion RMBa-1 under the 2000s trend scenario and the planning scenario, respectively. The spatial pattern of ESV in 2010 and 2020 presented a logical geographic distribution. The areas with ESV of 50,000 RMB ha(-1) a(-1) and higher occurred primarily in northeastern and southern China, while the areas with ESV of 5000 RMB ha(-1) a(-1) and lower were mainly located in northwestern China. The spatial differences between the two scenarios were insignificant except that the increase of ESV in southwestern China was more prominent in the planning scenario than that in the 2000s trend scenario, while the total ESV in 2020 under the planning scenario was larger than that in the 2000s trend scenario. The increase of ESV occurred mainly in northeastern, southern, and southeastern China due to forest growth and woodland expansion in 2020 compared with 2010. The results of this study can provide useful information for the public and land managers to consider

Anthropogenic and biogenic organic compounds in summertime fine aerosols (PM2.5) in Beijing, China

Ambient fine aerosol samples (PM2.5) were collected at an urban site (PKU) in Beijing and its upwind suburban site (Yufa) during the CAREBEIJING-2007 field campaign. Organic molecular compositions of the PM2.5 samples were studied for seven organic compound classes (sugars, lignin/resin acids, hydroxy-/polyacids, aromatic acids, biogenic SOA tracers, fatty acids and phthalates) using capillary GC/MS to better understand the characteristics and sources of organic aerosol pollution in Beijing. More than 60 individual organic species were detected in PM2.5 and were grouped into different compound classes based on their functional groups. Concentrations of total quantified organics at Yufa (469-1410 ng m(-3) average 1050 ng m(-3)) were slightly higher than those at PKU (523-1390 ng m(-3), 900 ng m(-3)). At both sites, phthalates were found as the most abundant compound class. Using a tracer-based method, the contributions of the biogenic secondary organic carbon (SOC) to organic carbon (OC) were 3.1% at PKU and 5.5% at Yufa, among which isoprene-SOC was the dominant contributor. In addition, most of the measured organic compounds were higher at Yufa than those at PKU, indicating a more serious pollution in its upwind region than in urban Beijing. (C) 2015 Elsevier Ltd. All rights reserved