Characterization of Nitrate-Reducing and Amino Acid–Using Bacteria Prominent in Nitrotoxin-Enriched Equine Cecal Populations

Horses can be at risk for nitropoisoning by consuming plants containing 3-nitro-1-propionic acid or 3-nitro-1-propanol and to a lesser extent by plants containing nitrate. Populations of equine cecal microbes enriched for enhanced rates of 3-nitro-1-propionic acid (NPA) or nitrate metabolism were cultured for NPA- or nitrate-metabolizing bacteria on basal enrichment medium or tryptose soy agar supplemented with either 5-mM NPA or nitrate and under H₂:CO₂ (20:80) as the energy source. After 72 hours, separated colonies picked from plates, or roll tubes were cultured in fresh broth medium for 72 hours and then identified by 16S rRNA gene sequencing. Isolates from the NPA-enriched populations were identified as Streptococcus lutetiensis (five strains), Escherichia coli (two strains), and Sporanaerobacter acetigens (one strain). Strains isolated from nitrate-enriched populations were identified as Escherichia coli (one strain) and Wolinella succinogenes (three strains). None of these strains degraded NPA. Enriched populations of equine cecal microbes, the isolated pure strains and the type strain of Denitrobacterium detoxificans, a competent NPA-metabolizing microbe, were examined using denaturing gradient gel electrophoresis (DGGE). The DGGE analysis indicated that none of the strains in the enriched population of equine cecal microbes were similar to D. detoxificans. However, we report for the first time the isolation of the anaerobic amino acid–using Sporanaerobacter acetigenes from the equine cecum.     

Estimation irrigation water requirements with derived crop coefficients for upland and paddy crops in ChiaNan Irrigation Association,Taiwan

Field experiments were performed at the HsuehChia Experimental Station from 1993 to 2001 to calculate the reference and actual crop evapotranspiration, derived the crop coefficient, and collected requirements input data for the CROPWAT irrigation management model to estimate the irrigation water requirements of paddy and upland crops at the ChiaNan Irrigation Association, Taiwan. For corn, the estimated crop coefficients were 0.40, 0.78, 0.89 and 0.71 in the initial, crop development, mid-season and late-season stages, respectively. Meanwhile, the estimated crop coefficients for sorghum were 0.44, 0.71, 0.87 and 0.62 in the four stages, respectively. Finally, for soybean, the estimated crop coefficients were 0.45, 0.89, 0.92 and 0.58 in the four stages, respectively. With implementation of REF-ET model and FAO 56 Penman–Monteith method, the annual reference evapotranspiration was 1268 mm for ChiaNan Irrigation Association.In the paddy fields, the irrigation water requirements and deep percolation are 962 and 295 mm, respectively, for the first rice crop, and 1114 and 296 mm for the second rice crop. Regarding the upland crops, the irrigation water requirements for spring and autumn corn are 358 and 273 mm, respectively, compared to 332 and 366 mm for sorghum, and 350 and 264 mm for soybean. For the irrigated scheme with single and double rice cropping patterns in the ChiaNan Irrigation Association, the CROPWAT model simulated results indicate that the annual crop water demands are 507 and 1019 mm, respectively, and the monthly water requirements peaked in October at 126 mm and in January at 192 mm, respectively.     

Effects of different soil conservation tillage approaches on soil nutrients,water use and wheat-maize yield in rainfed dry-land regions of North China

Excessive tillage compromises soil quality by causing severe water shortages that can lead to crop failure. Reports on the effects of conservation tillage on major soil nutrients, water use efficiency and gain yield in wheat (Triticum aestivum L.) and maize (Zea mays L.) in rainfed regions in the North China Plain are relatively scarce. In this work, four tillage approaches were tested from 2004 to 2012 in a randomized study performed in triplicate: one conventional tillage and three conservation tillage experiments with straw mulching (no tillage during wheat and maize seasons, subsoiling during the maize season but no tillage during the wheat season, and ridge planting during both wheat and maize seasons). Compared with conventional tillage, by 2012, eight years of conservation tillage treatments (no tillage, subsoiling and ridge planting) resulted in a significant increase in available phosphorus in topsoil (0–0.20 m), by 3.8%, 37.8% and 36.9%, respectively. Soil available potassium was also increased following conservation tillage, by 13.6%, 37.5% and 25.0%, and soil organic matter by 0.17%, 5.65% and 4.77%, while soil total nitrogen was altered by −2.33%, 4.21% and 1.74%, respectively. Meanwhile, all three conservation tillage approaches increased water use efficiency, by 19.1–28.4% (average 24.6%), 10.1–23.8% (average 15.9%) and 11.2–20.7% (average 15.7%) in wheat, maize and annual, respectively. Additionally, wheat yield was increased by 7.9–12.0% (average 10.3%), maize yield by 13.4–24.6% (average 17.4%) and rotation annual yield by 12.3–16.9% (average 14.1%). Overall, our findings demonstrate that subsoiling and ridge planting with straw mulching performed better than conventional tillage for enhancing major soil nutrients and improving grain yield and water use efficiency in rainfed regions in the North China Plain.     

Chukar Watering Patterns and Water Site Selection

We evaluated chukar (Alectoris chukar) watering patterns as well as habitat variables influencing water site selection in western Utah. Motion-sensing cameras and chukar dropping counts were primary techniques to evaluate watering patterns. We took vegetative and other habitat measurements at each water source (n = 43) to discriminate use from nonuse sites using logistic regression. Chukars watered during daylight hours with a modal hour from 1200 hours to 1300 hours daylight savings time. Annual patterns suggest limited use of water sources from November to May with first observed visits occurring in June and last observed visits in October. Shrub canopy cover was the only variable to discriminate between site types (P &spilt; 0.01). Cross validation showed a predictive success rate of 84%. Significant differences were found between use and nonuse sites in terms of security cover (P &spilt; 0.01), but not total cover (P &spigt; 0.05). Chukars seem to have a loose shrub canopy threshold near 11% that is likely due to predation risk. Water sources meeting this threshold received use, whereas those not meeting this threshold did not. Increasing shrub canopy cover above 11% did not translate into increased water source use. Managers might want to consider annual patterns when setting hunt season timing and structure as well as judging sites for new water developments based on shrub canopy cover. More generally, these results suggest a behavioral constraint on the use of water sources as a function of predation risk—we should expect other species to demonstrate similar behavioral constraints. These constraints must be considered in any effort to determine benefits or impacts of water developments.     

Yield and water consumption characteristics of wheat/maize intercropping with reduced tillage in an Oasis region

Higher irrigation quota for conventional farming causes substantial conflicts between water supply and demand in agriculture, and wind erosion near soil surface is one of the major causes of farmland degradation and desertification in arid areas. This research investigated the effect of the amounts of irrigation in combination with tillage practices on soil evaporation (E), water consumption (ET) characteristics, and grain yield performance and water use efficiency (WUE) for wheat (Triticum aestivum L.) intercropped with maize (Zea mays L.) in strip planting in an Oasis region. The field experiment, conducted at Wuwei station during 2008–2010, had two tillage systems (reduced tillage with wheat stubble retention vs. conventional tillage without stubble retention), and three (low, medium, and high) levels of irrigation, in a randomized complete block design. Averaged across three years, soil evaporation with medium and high levels of irrigation was 6.8% and 5.4% greater than that with low level of irrigation, respectively. Total water consumption of wheat/maize crops under the medium and high irrigation levels was 8.5% and 18.5% greater, respectively, than that under low irrigation. However, grain yields were similar under the medium and high levels of irrigation, so was WUE. The effect of tillage on the wheat/maize intercropping was inconsistent across years or among treatments: soil moisture at harvest was 3.0–7.6% greater in the fields with reduced tillage compared with those with conventional tillage in 2008 and 2009, but no difference was found in 2010; the E/ET ratio of reduced tillage was 9% lower than the ratio under conventional tillage in 2008, 3% higher in 2010, but no difference between the two tillage systems in 2009. Across three years, there was a general trend that the WUE of the wheat/maize intercropping system with reduced tillage was greater (by 4–11%) than that with conventional tillage. We conclude that a medium level of irrigation is sufficient to achieve crop yields and WUE equivalent to those under high level of irrigation, provided that a reduced tillage practice is applied to the wheat/maize intercropping in Oasis areas.     

Factors influencing earthworm communities in post-industrial areas of Krakow Soda Works

Application of earthworm in soil re-cultivation and re-creation in post-industrial ecosystems make a big challenge for temporal applied zoology. The sediments of the Krakow Soda Works “Solvay” have undergone land reclamation in different ways: older sediments traps were left without any re-cultivation practices; meanwhile the newest ones were reclaimed using standard method (new soil cover planted with combination of grass and leguminous plants). The effect of different treatments on community and population structure of earthworm was estimated during consecutive years 1999–2000. Six localities differing in time of establishment, reclamation processes, vegetation type and soil properties were chosen. Nine species were recorded, among which Aporrectodea caliginosa occurred in all localities, being also the most abundant. Two other species, Lumbricus rubellus and Dendrobaena octaedra, which are epigeic species, become most important in forest assemblages and were characteristic for communities of older succession processes. Abundance of adult forms as well as total biomass were significantly affected by soil depth (r = 0.75, P < 0.05, r = 0.917, P < 0.001, respectively). Species richness however was connected with higher amount of macroelements and average plant height. Shannon diversity index and its evenness negatively correlated only with forestation (r = –0.67, P < 0.05, r = –0.68, P < 0.05, respectively). Niche overlap (α Pianka) for all analysed species extracted two groups differing in environmental requirements. First contained epigeic earthworms, closely related to plant succession (PCA results), the other one grouped endogeic and anecique species correlated significantly with soil depth and plant density. Community structure of earthworms do not reflects succession changes in post-industrial habitats, but is strongly affected by microhabitat factors in local scale (mainly soil depth and plant density).     

基于MODIS遥感数据计算无定河流域日蒸散

为研究无定河流域日蒸散分布规律，应用遥感数据、农业气象站测量数据及Nishida模型等对该流域日蒸散进行了模拟。首先用2001～2002年晴天中国科学院禹城生态试验站Lysimeter测量日蒸散验证模型，模拟与测量的日蒸散相关系数达到0.61。随后，用该模型计算了无定河流域日蒸散，发现无定河流域日蒸散存在较为明显的空间分布规律：2001～2003年连续3年的8月份日蒸散都表现为东北部蒸散明显小于西南部，这是因为东北部基本是荒漠而东南部多是农田，且8月份日蒸散基本在2～5 mm之间变化；从2001年8月份第222 d日蒸散空间分布看，无定河主干道两边蒸散显著高于其他位置，这是由于8月份无定河流域为多雨季节，河谷土壤水分较高的缘故；从2002年内变化来看，不同的土地利用/覆被类型日平均蒸散差别不显著。     

Arsenic biogeochemistry as affected by phosphorus fertilizer addition,redox potential and pH in a west Bengal (India) soil

This laboratory experiment systematically examines arsenic, iron, and phosphorus solubilities in soil suspensions as affected by addition of phosphorus fertilizer under different redox potential (Eh) and pH conditions. Under aerobic conditions, As solubility was low, however, under moderately reducing conditions (0, − 150 mV), As solubility significantly increased due to dissolution of iron oxy-hydroxides. Upon reduction to − 250 mV, As solubility was controlled by the formation of insoluble sulfides, and as a result soluble As contents significantly decreased. Soluble Fe concentration increased from moderate to highly anaerobic conditions; however, it decreased under aerobic conditions likely due to formation of insoluble oxy-hydroxides. A low pH, 5.5, led to increased soluble concentrations of As, Fe, and P. Finally, addition of P-fertilizers resulted in higher soluble P and As, even though the concentration of As did not increased after an addition rate of 600 mg P kg^− 1 soil.     

Depth-specific distribution and importance of nitrite-dependent anaerobic ammonium and methane-oxidising bacteria in an urban wetland

Anaerobic ammonium oxidation (anammox) and nitrite-dependent anaerobic methane oxidation (n-damo) are two recently discovered processes in the nitrogen cycle that are catalysed by anammox bacteria and n-damo bacteria, respectively. Here, the depth-specific distribution and importance of anammox bacteria and n-damo bacteria were studied in an urban wetland, Xixi Wetland, Zhejiang Province (China). Anammox bacteria related to Candidatus Brocadia, Candidatus Kuenenia and Candidatus Anammoxoglobus, and n-damo bacteria related to “Candidatus Methylomirabilis oxyfera” were present in the collected soil samples. The abundance of anammox bacteria (2.6–8.6 × 10⁶ copies g⁻¹ dry soil) in the shallow soils (0–10 cm and 20–30 cm) was higher than that (2.5–9.8 × 10⁵ copies g⁻¹ dry soil) in the deep soils, whereas the abundance of n-damo bacteria (0.6–1.3 × 10⁷ copies g⁻¹ dry soil) in the deep soils (50–60 cm and 90–100 cm) was higher than that (3.4–4.5 × 10⁶ copies g⁻¹ dry soil) in the shallow soils. Anammox activity was detected at all depths, and higher potential rates (12.1–21.4 nmol N₂ g⁻¹ dry soil d⁻¹) were observed at depths of 0–10 cm and 20–30 cm compared with the rates (3.5–8.7 nmol N₂ g⁻¹ dry soil d⁻¹) measured at depths of 50–60 and 90–100 cm. In contrast, n-damo was mainly occurred at depths of 50–60 cm and 90–100 cm with potential rates of 0.7–5.0 nmol CO₂ g⁻¹ dry soil d⁻¹. This study suggested the niche segregation of the anammox bacteria and n-damo bacteria in wetland soils, with anammox bacteria being active primarily in deep soils and n-damo bacteria being active primarily in shallow soils.