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61.
Pfeiffer DU Otte MJ Roland-Holst D Inui K Nguyen T Zilberman D 《Veterinary journal (London, England : 1997)》2011,(3):309-316
This paper analyses the publicly available data on the distribution and evolution of highly pathogenic avian influenza virus (HPAIV) H5N1 clades, whilst acknowledging the biases resulting from the non-random selection of isolates for gene sequencing. The data indicate molecular heterogeneity in the global distribution of HPAIV H5N1, in particular in different parts of East and Southeast Asia. Analysis of the temporal pattern of haemagglutinin clade data shows a progression from clade 0 (the ‘dominant’ clade between 1996 and 2002) to clade 1 (2003–2005) and then to clade 2.3.4 (2005 onwards). This process continuously produces variants, depending on the frequency of virus multiplication in the host population, which is influenced by geographical variation in poultry density, poultry production systems and also HPAI risk management measures such as vaccination. Increased multilateral collaboration needs to focus on developing enhanced disease surveillance and control targeted at evolutionary ‘hotspots’. 相似文献
62.
In this study, the effect of drying and rewetting on native P transformations in two red brown soils with different management history was investigated. Three treatments, T1 (constantly moist), T2 (dried for 4 days and then kept dry), T3 (rewetted after 4 days drying) were used. Drying and rewetting caused a rapid increase in microbial P (Pm) and labile organic P (labile Po) within 1 day and a gradual increase in available inorganic P (Colwell). These increases were only temporarily, as Pm and labile Po decreased with time and were at the same level as in the constantly moist soil by the end of the incubation period of 21 days. The effect of drying and rewetting on P transformations strongly depended on soil organic matter content, being more pronounced in the soil with high organic matter content, compared to the soil with low soil organic matter content. 相似文献
63.
Emile Benizri Christophe Nguyen Sophie Slezack-Deschaumes 《Soil biology & biochemistry》2007,39(5):1230-1233
The organic compounds released from roots (rhizodeposits) stimulate the growth of the rhizosphere microbial community. They may be responsible for the differences in the structure of the microbial communities commonly observed between the rhizosphere and the bulk soil. Rhizodeposits consists of a broad range of compounds including root mucilage. The aim of this study was to investigate if additions of maize root mucilage, at a rate of 70 μg C g−1 day−1 for 15 days, to an agricultural soil could affect the structure of the bacterial community. Mucilage additions moderately increased microbial C (+23% increase relative to control), which suggests that the turnover rate of microorganisms consuming this substrate was high. Consistent with this, the number of cultivable bacteria was enhanced by +450%. Catabolic (Biolog® GN2) and 16S-23S intergenic spacer fingerprints exhibited significant differences between control and mucilage treatments. These data indicate that mucilage can affect both the metabolic and genetic structure of the bacterial community as shown by a greater catabolic potential for carbohydrates. We concluded that mucilage is likely to significantly contribute to differences in the structure of the bacterial communities present in the rhizosphere compared to the bulk soil. 相似文献
64.
Van Minh Dang Hoa Thi Minh Duong Duy Hai Nguyen Lan Huong Nguyen 《Soil Science and Plant Nutrition》2020,66(2):379-388
ABSTRACT
In
-situ sorbent amendment is a relatively low-cost, low-impact approach for remediation of soil contaminated with heavy metals (HMs), and thus is considered a way to be favored in developing countries. In this study, materials of non-hazardous, alkaline agronomic and industrial by-products were used as sorbents to explore their capacity of in situ immobilization of multiple HMs in mining-impacted arable soil. These sorbents included fly ash (FA), biochar (BC) and apatite (AP) and they were implemented with varying ratios of combinations. Results of soil microcosm tests showed that after incubation for 90 days, concentrations of Pb, Zn, and Cd in their exchangeable forms determined by a sequential extraction method significantly decreased in amended soils, as opposed to the unamended control. Of the five sets of amendments, the composite of FA, BC, and AP resulted in the maximum reduction (up to 80%) in the mobility of Pb, Zn, and Cd in soils. The mechanisms underlying the immobilization of HMs in amended soils might involve processes of surface precipitation, ion exchange and complexation, in which the physicochemical properties of sorbent materials played an important role. The immobilization efficacy of sorbent amendments on HMs in soil was further supported by pot experiments in which significant inhibition of HM accumulation in the belowground and aboveground tissues of maize was observed after 50-day cultivation in amended soils as compared with control soil. Together, these results suggest that the application of cost-saving and environmentally friendly materials derived from wastes as sorbents to remediate soils contaminated with multiple HMs is promising for developing countries like Vietnam. 相似文献65.
Influence of changes in land use and earthworm activities on carbon and nitrogen dynamics in a steepland ecosystem in Northern Vietnam 总被引:1,自引:0,他引:1
66.
Regional Sediment Deficits in the Dutch Lowlands: Implications for Long-Term Land-Use Options (8 pp)
Michiel J. van der Meulen Ad J. F. van der Spek Ger de Lange Stephan H. L. L. Gruijters Serge F. van Gessel Buu-Long Nguyen Denise Maljers Jeroen Schokker Jan P. M. Mulder Rob A. A. van der Krogt 《Journal of Soils and Sediments》2007,7(1):9-16
Background, Aim and Scope
Coastal and river plains are the surfaces of depositional systems, to which sediment input is a parameter of key-importance.
Their habitation and economic development usually requires protection with dikes, quays, etc., which are effective in retaining
floods but have the side effect of retarding sedimentation in their hinterlands. The flood-protected Dutch lowlands (so-called
dike-ring areas) have been sediment-starved for up to about a millennium. In addition to this, peat decomposition and soil
compaction, brought about by land drainage, have caused significant land subsidence. Sediment deficiency, defined as the combined
effect of sediment-starvation and drainage-induced volume losses, has already been substantial in this area, and it is expected
to become urgent in view of the forecasted effects of climate change (sea-level rise, intensified precipitation and run-off).
We therefore explore this deficiency, compare it with natural (Holocene) and current human sediment inputs, and discuss it
in terms of long-term land-use options.
Materials and Methods:
We use available 3D geological models to define natural sediment inputs to our study area. Recent progress in large-scale
modelling of peat oxidation and compaction enables us to address volume loss associated with these processes. Human sediment
inputs are based on published minerals statistics. All results are given as first-order approximations.
Results:
The current sediment deficit in the diked lowlands of the Netherlands is estimated at 136 ± 67 million m3/a. About 85% of
this volume is the hypothetical amount of sediment required to keep up with sea-level rise, and 15% is the effect of land
drainage (peat decomposition and compaction). The average Holocene sediment input to our study area (based on a total of 145
km3) is ~14 million m3/a, and the maximum (millennium-averaged) input ~26 million m3/a. Historical sediment deficiency has
resulted in an unused sediment accommodation space of about 13.3 km3. Net human input of sediment material currently amounts
to ~23 million m3/a.
Discussion:
As sedimentary processes in the Dutch lowlands have been retarded, the depositional system's natural resilience to sea-level
rise is low, and all that is left to cope is human countermeasure. Preserving some sort of status quo with water management
solutions may reach its limits in the foreseeable future. The most viable long-term solutions therefore seem a combination
of allowing for more water in open country (anything from flood-buffer zones to open water) and raising lands that are to
be built up (enabling their lasting protection). As to the latter, doubling or tripling the use of filling sand in a planned
and sustained effort may resolve up to one half of the Dutch sediment deficiency problems in about a century.
Conclusions:
Conclusions, Recommendations and Perspectives. We conclude that sediment deficiency – past, present and future – challenges
the sustainable habitation of the Dutch lowlands. In order to explore possible solutions, we recommend the development of
long-term scenarios for the changing lowland physiography, that include the effects of Global Change, compensation measures,
costs and benefits, and the implications for long-term land-use options.
Recommendations and Perspectives:
- 相似文献
67.
Kazunori Minamikawa Huynh Cong Khanh Yasukazu Hosen Tran Sy Nam Nguyen Huu Chiem 《Soil Science and Plant Nutrition》2020,66(1):225-234
ABSTRACT Livestock production plays a leading role in agricultural land-use change. Producing biogas from livestock waste and subsequently using the biogas effluent as fertilizer for crops is a promising option to solve environmental problems resulting from expanding livestock production. However, it is difficult to promptly and accurately measure the nitrogen (N) concentration of effluent for farmers in developing countries, making precise N management difficult. The objectives of the current study were (1) to evaluate the feasibility of variable-timing, fixed-rate application of cattle biogas effluent using a leaf color chart (LCC) for rice (Oryza sativa L.) and (2) to determine the optimum LCC threshold for grain yield. We conducted two microcosm experiments in the Mekong Delta of Vietnam in 2018 using eight treatments of N-fertilizer application. In the Zero treatment, we applied no N. In the Estd treatment, we split-applied N as effluent (E) at fixed rate and timing as the standard method. In E2.75, E3.00, E3.25, E3.50, and E3.75, we applied effluent whenever the LCC value went below 2.75, 3.00, 3.25, 3.50, and 3.75, respectively. In U3.25, we applied N as urea (U) whenever the LCC value fell below 3.25. The total effluent-N application rate ranged from 90 to 210 kg N ha?1 season?1. Rice growth was normal but there was a substantial yield gap between the two microcosm experiments due to the seasonal difference in solar radiation. Rice yield tended to increase with increasing LCC threshold. There was a positive linear relationship between LCC and chlorophyll content (SPAD) values (R 2 = 0.73–0.79). Grain yield was well explained (R 2 = 0.70–0.89) by the seasonal mean LCC or SPAD value. Plant total N uptake increased with increasing LCC threshold, but the three calculated indices of N use efficiency (NUE) – apparent N recovery, agronomic NUE, and internal NUE – were not always improved with a higher LCC threshold. Our results showed that the tested variable-timing, fixed-rate strategy for the application of cattle biogas effluent was feasible and the optimum LCC threshold for grain production was 3.75 under the current microcosm conditions. 相似文献
68.
Summary Topsoils (0–75 mm) from four different soil types were collected from stock camp and non-camp (main grazing area) areas of grazed pastures in New Zealand, which had been fertilised annually with superphosphate for more than 15 years, in order to assess the effects of grazing animals on the status and distribution of soil S fractions and organic matter. These soils were analysed for organic C, total N, total S, C-bonded S, hydriodic acid-reducible S, 0.01 M CaCl2, and 0.04 M Ca(H2PO4)2-extractable S fractions, and soil pH. Soil inorganic and organic S fractions extracted by NaHCO3 and NaOH extractants were also determined. The results obtained showed that camp soils contain higher soil pH, organic C, total N, total S, organic (C-bonded S and hydriodic acid-reducible S) and inorganic S fractions, NaHCO3-and NaOH-extractable soil S fractions but a lower anion retention capacity than non-camp soils, attributed to a higher return of plant litter and animal excreta to camp soils. In both soils, total S, organic S, C-bonded S, and hydriodic acid-reducible S were significantly correlated with organic C (r0.90***, ***P0.001) and total N (r0.95***), suggesting that C, N, and S are integral components of soil organic matter. However, C: N : S ratios tended to be lower in camp (60: 5.6: 1–103: 7.2: 1) than in non-camp soils (60:6.1:1–117:8.3:1). Most (>95%) of the total soil S in camp and non-camp soils is present as organic S, while the remainder is readily soluble and adsorbed S (i.e. Ca(H2PO4)2-extractable S). C-bonded S and hydriodic acid-reducible S constituted 55%–74% and 26%–45% of total S, respectively, reflecting a regular return of plant litter and animal excreta to the grazed pastures. NaHCO3, and especially NaOH, extracted significantly higher amounts of total soil S (13%–22% and 49%–75%, respectively) than Ca(H2PO4)2 or CaCl2 (<5%). In addition, NaHCO3 and NaOH-extractable soil S fractions were significantly rorrelated with soil organic S (r0.94***), C-bonded S (r0.90***) and hydriodic acid-reducible soil S (r0.93***). Differences between soils in either camp or non-camp areas were related to their sulphate retention capacities, as soils with high sulphate retention capacities (>45%) contain higher levels of C-bonded and hydriodic acid-reducible S fractions than those of low sulphate retention soils (<10%). Long-term annual superphosphate applications significantly increased the accumulation of soil organic and inorganic S fractions, and organic C and total N in the topsoil, although this accumulation did not occur when the superphosphate application rates were increased from 188 to 376 kg ha-1 year-1. 相似文献
69.
70.
Nguyen Vu SON James Kenn CHAMBERS Makoto NAKATA Yasutsugu MIWA Hiroyuki NAKAYAMA Kazuyuki UCHIDA 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2022,84(2):208
This report described the histopathological and immunohistochemical features of cutaneous mast cell tumor (MCT) in six hedgehogs. The hedgehogs presented single cutaneous mass with ulcer and crusting. Histologically, the neoplastic lesions were characterized by the proliferation of well-differentiated mast cells (3 cases), and atypical mast cells (3 cases) with one atypical histiocytic morphology. Immunohistochemically, tumor cells were positive for KIT and mast cell tryptase, and were negative for Iba-1. In well-differentiated MCT, all patients were clinically improved and survived more than 365 days after surgical excision, whereas an atypical histiocytic MCT showed aggressive behavior with re-recurrence, and the animal died 115 days after surgery. These findings suggest that, compatible with other animals, well-differentiated MCT has a better prognosis in hedgehogs. 相似文献