Influence of fertilized short-rotation forest plantations on nitrogen concentrations in groundwater     

L. Bergström  R. Johansson 《Soil Use and Management》1992,8(1):36-39

Abstract. The influence of intensively fertilized short-rotation forest plantations on nitrogen concentrations in groundwater was studied by piezometer readings and water sampling over a two-year period in a sandy field growing willow ( Salix spp.) and other species. The mineral-N content of the unsaturated zone was measured in soil samples collected to 0.9 m depth. Although piezometer readings suggested that deep groundwater could be affected, the concentrations of nitrate-N and ammonium-N were usually less than 1 mg per litre. There was also little mineral-N in the unsaturated zone, except for occasional peaks in the topsoil (0–30 cm) after application of fertilizer. We conclude that there is little risk of nitrogen contamination of groundwater in intensively cultured tree stands receiving up to 150 kg N/ha/yr as fertilizer. This is probably because willow can take up water and nitrogen from deep parts of the soil profile.  相似文献   

Resistance Reaction of Conifer Species (European Larch, Norway Spruce, Scots Pine) to Infection by Selected Necrotrophic Damping-off Pathogens     

M. Kacprzak  F.O. Asiegbu  G. Daniel  J. Stenlid  M. Mañka  M. Johansson 《European journal of plant pathology / European Foundation for Plant Pathology》2001,107(2):191-207

Three conifer species (European larch, Norway spruce, Scots pine) were investigated for their resistance to five damping-off pathogens (Rhizoctonia solani, Fusarium solani, F. oxysporum, F. culmorum, F. avenaceum). Inoculation of the primary roots of seedlings with these pathogens caused host cell death which did not prevent the invasive growth of these fungi; seedlings that had formed secondary and tertiary roots could overcome the infection to a significant degree. Infections with R. solani caused significant mortality to all the conifer species. In contrast, the tree species expressed different levels of resistance when challenged with the Fusarium isolates, with Norway spruce being the most resistant compared to uninoculated controls. Some of the Fusarium isolates were more pathogenic to certain hosts than others; F. oxysporum for European larch, F. avenaceum for Scots pine, F. solani for European larch; only F. culmorum was significantly pathogenic to Norway spruce. No significant differences in disease severity were observed at different soil pH (4.3–7.5). Disease progression was delayed at lower (10–15°C) rather than higher temperatures (20–25°C).  相似文献   

Effects of Growth Hormone on In Situ Culture of Bovine Preantral Follicles are Dose Dependent          下载免费PDF全文

CR Jimenez  JL de Azevedo  RG Silveira  J Penitente‐Filho  EL Carrascal‐Triana  AM Zolini  VR Araújo  CAA Torres 《Reproduction in domestic animals》2016,51(4):575-584

The objective of this study was to evaluate different concentrations of growth hormone (GH) on the development of bovine preantral follicles cultured included in the ovarian tissue (in situ) on the rates of morphologically normal, viable, primordial and developing follicles, as well as the oocyte and follicle diameter and ultrastructural analysis. Ovarian fragments collected from cows with no cross‐breeds defined were cultured in situ for 1 and 7 days in minimal essential medium (α‐MEM+) supplemented with different concentrations of recombinant human GH (0, 10, 25, 50 ng/ml). The ovarian fragments non‐cultured (control) and cultured were processed for classic histology, mechanical isolation and electron transmission microscopy (MET). The parameters underwent anova (Tukey′s and Dunnett′s tests) and chi‐square test (χ²). After 7 days of culture, the treatment with 50 ng/ml GH showed no differences with fresh control (p > 0.05) and had greater effectiveness than in the 0, 10 and 25 ng/ml GH concentrations of the morphologically normal follicles. Regarding the primordial follicles, a reduction was observed in the 50 ng/ml GH concentration concomitant with the significant increase in developing follicles, differing from both the fresh control and the other GH concentrations tested. In addition, 50 ng/ml GH showed a larger follicle and oocyte diameter when compared to the other treatments cultured. Similar structures were ultrastructurally observed in the control group, 50 ng/ml GH. Follicles cultured in 10 ng/ml GH showed nuclear invagination, vacuoles and lesioned basal membrane. Hence, it is concluded that 50 ng/ml GH is the most effective concentration for the development of preantral follicles cultured in situ.  相似文献   

Aboveground biomass production of a semi-arid southern African savanna: towards a new model     

Anthony R Palmer  Igshaan Samuels  Clement Cupido  Andiswa Finca  W Fransiska Kangombe  Isa AM Yunusa 《African Journal of Range and Forage Science》2016,33(1):43-51

Following a field campaign to determine the species composition, canopy cover, aboveground annual production and leaf area index (LAI) of the semi-arid savanna of north-western Namibia, we present a production model that can be used by graziers to determine the livestock carrying capacity. The model predicts the annual aboveground net primary production (ANPP) from regression equations of canopy cover by annual production fraction for plant functional classes. We tested the output of the model against another fully independent net primary production (NPP) model, namely the MODIS NPP product. The mean MODIS NPP for the 29 sites was 343 ± 22?kg dry matter (DM) ha^?1 y^?1 as opposed to 285 ± 142?kg DM ha^?1 y^?1 for the fAP model that used the regression method (p < 0.01). As a proof of concept, these landscape-scale ANPP values are used to calculate a recommended livestock carrying capacity for the Ehirovipuka Communal Conservancy, a 1 980 km² communal area with both wildlife and livestock populations. In addition, we also provide details of a field method for predicting landscape-scale LAI from line transect data. This approach can be used to ground reference the LAI values generated from the MODIS LAI product.  相似文献   

Diagnosis and ultrasonographic appearance of hepatic metastasis in six cases of canine appendicular osteosarcoma (2005–2013)          下载免费PDF全文

L Cesario  LD Garrett  AM Barger  RT O'Brien  TM Fan 《Australian veterinary journal》2016,94(5):160-165

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Negative pressure wound therapy using a portable single‐use device for free skin grafts on the distal extremity in seven dogs          下载免费PDF全文

AJ Miller  RG Cashmore  AM Marchevsky  M Havlicek  PM Brown  SM Fearnside 《Australian veterinary journal》2016,94(9):309-316

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Peste des petits ruminants in wild ungulates     

Aziz-ul-Rahman  Jonas Johansson Wensman  Muhammad Abubakar  Muhammad Zubair Shabbir  Paul Rossiter 《Tropical animal health and production》2018,50(8):1815-1819

Peste des petits ruminants (PPR) is a contagious viral disease of domestic small ruminants. It also affects wild ungulates but there are comparatively few studies of the incidence of natural infection, clinical signs and pathology, and confirmation of the virus, and in these species. In this article, we list the wild ungulates in which PPRV infection has been confirmed and summarize available information about the presentation of the disease, its identification, and impact of virus on wildlife populations. Considering recent reports of outbreaks by the World Organization for Animal Health (OIE), it is important to understand the transmission of this disease within wildlife populations in PPR endemic regions.  相似文献   

Obtaining Wisent early blastocyst in vitro is a basic for protection and creation of biodiversity for this threatened species          下载免费PDF全文

AM Duszewska  P Gręda  M Baraniewicz  W Bielecki  W Niżański  A Partyka  M Tracz  Z Nowak  A Chełmońska‐Soyta  W Olech 《Reproduction in domestic animals》2018,53(3):818-821

Wisent, or European bison (Bison bonasus), is listed as “vulnerable” on the IUCN Red List of Threatened Species and is therefore protected by international law. For the first time, a Wisent embryo has been obtained in vitro. This procedure creates a new opportunity to protect and increase Wisent reproductive potential and thereby opens new possibilities for the establishment of a controlled and broad reserve of the gene pool.  相似文献   

Effect of intermittent drought on grain yield and quality of rice (Oryza sativa L.) grown in Rwanda     

Alphonsine Mukamuhirwa  Helena Persson Hovmalm  Rodomiro Ortiz  Obedi Nyamangyoku  Maria Luisa Prieto–Linde  Anders Ekholm  Eva Johansson 《Journal of Agronomy and Crop Science》2020,206(2):252-262

The climate change will contribute drought and temperature extremes to rice growing systems, especially when cultivated in equatorial regions. To evaluate opportunities to cultivate and breed drought-tolerant rice, seven rice cultivars were evaluated in Rwanda for recurring morphological drought scores, grain yield and components, and quality characteristics. The cultivation conditions, that is site and drought treatment, impacted morphological drought scores, growth and yield attributes, while cultivar affected quality attributes. Thus, site showed a higher impact on grain yield and components than drought and cultivar, with generally a reduced grain yield at the low-temperature site, as a result of low spikelet fertility. Morphological drought scores were generally increased by drought, while drought at the reproductive stage at the high-temperature site was negative for yield and its components. The cultivars “Intsindagirabigega” and “Jyambere” were adapted to high-temperature site conditions. The cultivar “Intsindagirabigega” had the highest amylose content, and “Mpembuke,” the highest antioxidant capacity. Thus, climate change with increased temperature and drought extremes may increase rice productivity in cool areas, while especially drought at reproductive stage will be detrimental in low altitude areas with high temperature. Cultivar variation indicated opportunities for selection and breeding of climate change tolerant rice cultivars which should be of immediate priority.  相似文献   

Saintpaulias in their natural environment with notes on their present status in Tanzania and Kenya     

Dick R. Johansson 《Biological conservation》1978,14(1):45-62

Several species of the genus Saintpaulia, popularly known as Usambara violets, have become a remarkable success as indoor plants in Europe and the USA. Their ancestors, some twenty species in total, live in mountains and near the coast in Tanzania and Kenya. The Saintpaulias require a very special environment since they are sensitive to drought and to competition from other plants. Thus, most species live on steep rock surfaces in dense shade where few other plants thrive. The Usambara violets in cultivation are mostly referred to as Saintpaulia ionantha. Previous records of this species refere to a restricted area near Tanga in Tanzania where today it is very rare because of changes in the environment. Tree-felling to create farmland or to obtain firewood has exposed the previously shaded limestone cliffs, making them unsuitable as habitat for Saintpaulia ionantha.Generally speaking, disturbance of the environment by clearance of trees and bushes is the main threat to the survival of most species, particularly those which occur in the lowlands.  相似文献