The effects of long and short soil freezing-defrosting cycles on nitrifying microbial activity

An incubation experiment was conducted on chestnut soil microcosms to assess the impact of long and short cold shock on the rate of nitrification of ammonium-oxidizing bacteria and archaea. Significant reduction of nitrifying activity was observed after 2 weeks of cold shock, while 24-hour incubation at a low temperature did not affect the rate of nitrification of microorganisms. We assume that the prevalence of psychrophiles or mesophiles with a broad range of adaptation in the chestnut soil helps maintain a high level of nitrification in conditions of frequent fluctuations of high and low temperatures. Decreasing nitrifying activity after long freezing points to the death of a small pool of the least resistant organisms, which is associated with the peculiarities of the geographical location of chestnut soils and lack of long periods of soil freezing. The composition of communities of bacteria and archaea in the course of the experiments did not change, which was determined by denaturing gel electrophoresis (DGGE).     

Carbon dioxide,methane, and nitrous oxide fluxes in soil catena across the right bank of the Oka River (Moscow oblast)

The flux rates of carbon dioxide, methane, and nitrous oxide in the soils on autonomous, transitional, transitional-accumulative, and accumulative positions of a catena on the Oka River’s right bank (Moscow oblast) were assessed using the chamber method. The lowest rate of C-CO₂ emission (18.8–29.8 mg/m² per hour) was found for the gray forest soil in the autonomous position, and the highest rate (52.4–66.1 mg/m² per hour) was found for the alluvial meadow soil of the accumulative landscape. In the summer, the uptake of methane from the atmosphere exceeded its release from the soil at all the points of the catena (9–38 μg/m² per hour). The highest rate of the C-CH₄ uptake was observed for the soil in the transitional position. In the fall, the soils in the autonomous, transitional, and transitional-accumulative positions served as a sink of C-CH₄, and the soil of the accumulative position was a source of methane emission. The rate of the N-N₂O emission from the catena soils increased when going from the autonomous position to the accumulative one (0.41–11.2 μg/m² per hour). The spatial variation of the C-CO₂, C-CH₄, and N-N₂O fluxes within the catena was 33, 172, and 138%, respectively. The upper (0- to 10-cm) soil layer made the major contribution to the emission of carbon dioxide. This soil layer was characterized by its C-CH₄ uptake, and the emission of methane was typical for the deeper (0- to 20-cm) layer. The layers deeper than 10 and 20 cm emitted more N-N₂O than the surface layer.     

A correlation network approach to metabolic data analysis for tomato fruits

Network analysis of correlations between abundances of metabolites across tomato genotypes can help in unraveling the biological basis of organoleptic variation in tomato. We illustrate how to construct and interpret simple correlations networks using metabolic data collected on a diverse set of tomato genotypes. Various types of correlations are calculated and displayed in the form of networks. Interpretations on the basis of network analyses are compared to interpretations following principal components analysis.     

The Hymenopteran parasitoid complex associated with Coniesta ignefusalis (Hampson) (Lepidoptera: Crambidae) on Pearl millet in Mali

Phytoparasitica - Moths of Coniesta ignefusalis (Hampson) were collected by automatic light traps on millet field near Bamako in 2018. The light trap data shows three periods of moth flight. The...     

Maize (Zea mays L.) yield and soil properties as affected by no tillage in the black soils of China

A four-year tillage experiment on maize was conducted in the high latitude region of Northeast of China. The main objective of this study was to investigate the effects of different field tillage practices on maize grain yield, soil physical properties, and soil water and temperature dynamics in Northeast of China. The tillage practices included moldboard plow tillage (MOT), rotary tillage (ROT), reduced tillage (RET), combined tillage (COT), and no tillage (NOT). The surface soil water content at depths of 0–20 cm was higher under NOT compared with other tillage practices, but not different at the deeper soil depths in 2011. The soil temperatures under NOT and RET were lower than those under moldboard plow tillage and ROT at depths of 5 and 15 cm, respectively, measured at 9:00 am in 2005. From the hourly dynamics of soil temperature, the differences among the tillage practices mainly appeared during the daytime (from 8:00 am to 7:00 pm). Among all the practices, the average daily soil temperature under ROT was the highest, while that under NOT was the lowest. MOT, ROT, and RET had higher soil accumulative infiltration compared with NOT and COT. The surface soil bulk density under NOT was higher than or equal to that under the other four tillage practices. The maize yields under NOT were the lowest among all the tillage practices for three years straight. Meanwhile, the yields under MOT were the highest, which were about 47%, 61%, and 38% higher than those under NOT. NOT practice is not recommended for use in spring-planted maize under the high latitude humid cool climate Mollisol region in Northeast of China.     

Comparative analysis of soil DNA extraction methods to study various ammonium-oxidizing bacteria and archaea by PCR-DGGE

A comparative analysis of five methods of extraction and purification of soil DNA, including a modification of the authors, was performed for the further molecular investigation of various ammonium-oxidizing bacteria and archaea in soils. Experiments using soil samples from natural ecosystems and agroecosystems of the European area of Russia established that the amount of DNA extracted by different methods depended significantly on the type of soil. The subsequent molecular analysis (PCR-DGGE) of ribosomal (16S rRNA) and functional (amoA) genes demonstrated significant differences in the community structure of ammonium oxidizers depending on the method of DNA extraction. The best results were obtained for acidic soil (soddy-podzolic and gray forest soils) when using the method of Griffiths et al. [4] with our own modification. On the other hand, application of commercial DNA extraction kits was most efficient for soils with a high content of humus (black and chestnut soils). According to the results obtained, molecular analysis of soil microbe communities required selection of optimum conditions for DNA extraction, especially for soils with high contents of organic compounds and clay minerals at different pH levels.     

典型黑土区村级尺度侵蚀沟演变

侵蚀沟的演变是东北水土流失过程的重要方面.利用1968和2009年亚米级遥感影像,获取典型黑土区村级尺度的侵蚀沟分布、耕地垄向和土地利用数据,基于1∶1万地形图获取等高线、坡度、坡长和垄向坡度数据,在地理信息系统和遥感技术的支持下,分析典型黑土区41 a村级尺度侵蚀沟的动态变化及其影响因素.结果表明:1)41 a间,典型黑土区侵蚀沟密度有明显增加的趋势,基于分辨率为亚米级遥感影像解译的侵蚀沟密度较以往研究结果大幅增加;2)自然坡度0.25°～1.5°范围内为该区域侵蚀沟密度变化最大的区域,8°以上区域由于实施退耕还林措施,侵蚀沟密度降低;3)300～500 m坡长区域侵蚀沟密度出现极值;4)由于实施改垄措施,41 a后垄向坡度在0～0.25°范围内耕地面积增加,大于0.25°范围内耕地面积均减少.