Restoration of degraded ecosystems in the Afromontane highlands of Ethiopia: comparison of plantations and natural regeneration§     

Abrham Abiyu  Demel Teketay  Gerhard Glatzel  Raf Aerts  Georg Gratzer 《Southern Forests》2017,79(2):103-108

The scale of deforestation in sub-Saharan Africa underscores the need for forest restoration. Information is scarce for evidence-based restoration options. Sown Senna didymobotrya, planted Ficus thonningii cuttings, sown S. didymobotrya and planted F. thonningii combined, and previously occurring native non-browse shrubs (NNS) were compared for their effect on selected plant nutrients and occurrence of Olea europaea subsp. cuspidata in north-west Ethiopia. The treatments were applied to experimental units established on previous grazing land. At the end of the fourth year, 60% of planted F. thonningii stakes survived. The leaf biomass production was encouraging. Senna didymobotrya attained close to 1 m height and crown width. Natural regeneration of O. europaea was observed only under previously occurring shrubs. Six previously occurring NNS species were identified. Soils immediately under these shrubs were richer in nutrients than between shrubs in the open spaces. Our results suggest that vegetative stakes and NNS could be promising tools for ecological restoration of decimated ecosystems in the highlands of Ethiopia. Management interventions, which aim at steering succession close to pre-disturbance forest community structure by facilitation, should be selective of the shrub species.  相似文献   

Effect of energy restriction and re-alimentation in Belgian Blue double-muscled beef cows on digestibility and metabolites     

Fiems LO  Vanacker JM  De Boever JL  van Caelenbergh W  Aerts JM  De Brabander DL 《Journal of animal physiology and animal nutrition》2007,91(1-2):54-61

Four groups of five non-lactating and non-pregnant Belgian Blue double-muscled (BBDM) cows were used to investigate the effect of energy level (E) on digestion, and blood and urine metabolites. The energy levels of the groups, applied indoors during a 140-day restriction period, were 100%, 90%, 80% or 70% of their energy requirements (E100, E90, E80, E70) respectively. Afterwards, animals grazed on the same swards for 203 days (re-alimentation period). Balance trials were conducted at the end of the restriction period (BT1) and at the end of the re-alimentation period (BT2). Blood was sampled at the end of these trials. Diets consisted of maize silage and straw (80/20 on a dry matter basis) and a mineral-vitamin premix, fed at the appropriate E during BT1, or maize silage and a mineral-vitamin premix, fed at 125% of the maintenance requirements, during BT2. Significant increases of the digestibility coefficients were found during BT1 when E decreased, resulting in a better net energy capture of 7% for E70 compared with E100 (p < 0.05). Slightly, but non-significantly higher digestibility coefficients were observed for decreasing E during BT2. Plasma concentrations of glucose and creatinine did not differ between treatments during BT1, while differences were found for triacylglycerols and alpha-amino nitrogen. A tendency for a linear increase was observed for non-esterified fatty acids with decreasing E. Differences in blood metabolite concentrations disappeared in BT2. Urinary creatinine excretion was not affected by E, while body nitrogen loss increased linearly with energy restriction in BT1. No differences were found during BT2, suggesting that non-lactating and non-pregnant BBDM cows are able to adapt to a cyclic change of body weight and body reserves. These data show that restricted cows mobilized body fat as well as body protein. It is concluded that the qualitative aspects of metabolism during energy restriction are comparable in double-muscled cows with those in non-double-muscled animals, although the magnitude of the effects may be different.  相似文献   

Site requirements of the endangered rosewood Dalbergiaoliveri in a tropical deciduous forest in northern Thailand     

Raf Aerts  Hugo Volkaert  Nalinee Roongruangsree  U-Tai Roongruangsree  Rony Swennen  Bart Muys 《Forest Ecology and Management》2009

Planting native trees may complement and accelerate natural regeneration and support recovery of biodiversity in degraded forests. Before planting trees, however, there is a need for species-specific site selection criteria. This study investigates the site requirements of a valuable but endangered rosewood species, Dalbergia oliveri, with the purpose of restoring degraded deciduous forest in northern Thailand.  相似文献   

Pinpointing the role of Aeromonas salmonicida in the development of skin ulcerations in common dab (Limanda limanda)     

Maaike Vercauteren  Evelien De Swaef  Annelies Maria Declercq  Johan Aerts  Bart Ampe  Snorre Gulla  Freddy Haesebrouck  Lisa Devriese  Annemie Decostere  Koen Chiers 《Journal of fish diseases》2020,43(3):347-357

Aeromonas salmonicida was isolated from ulcerations in common dab (Limanda limanda). An experiment was performed to pinpoint its role in ulceration development, considering the importance of the skin barrier and the pigmented and non-pigmented sides. The skin of dab was treated in three zones, one where scales and epidermis were removed, one where mucus was discarded and one non-treated zone. Fish were tagged to allow individual identification and challenged with A. salmonicida. Mortality and severity of the developing lesions were recorded for 21 days post-inoculation. Starting 12 days post-inoculation, mortality occurred gradually in challenged fish; however, no direct cause could be established. Both control fish and challenged fish developed ulcerations containing A. salmonicida. Sequencing of vapA gene revealed that isolates retrieved from both groups were distinct, suggesting the presence of A. salmonicida prior to the trial. Most ulcerations developed in zones where skin was removed, suggesting that abrasion might be a predisposing factor in ulceration development. Ulcerations were also observed at the insertion site of the tag, where exposed muscle tissue might have favoured the development of ulcerations. In conclusion, A. salmonicida seems to be involved in the development of skin ulcerations in dab, although the exact pathogenesis needs to be elucidated.  相似文献   

Modeling combined continuous and ordinal outcomes in a clustered setting     

Christel?FaesEmail author  Helena?Geys  Marc?Aerts  Geert?Molenberghs  Paul?J.?Catalano 《Journal of Agricultural, Biological & Environmental Statistics》2004,9(4):515-530

Measurements of both continuous and categorical outcomes appear in many statistical problems. One such example is the study of teratology and developmental toxicity, where both the probability that a live fetus is malformed (ordinal) or of low birth weight (continuous) are important measures in the context of teratogenicity. Although multivariate methods of the analysis of continuous outcomes are well understood, methods for jointly continuous and discrete outcomes are less familiar. We propose a likelihood-based method that is an extension of the Plackett-Dale approach. Specification of the full likelihood will be avoided using pseudo-likelihood methodology. The estimation of safe dose levels as part of quantitative risk assessment will be illustrated based on a developmental toxicity experiment of diethylene glycol dimethyl ether in mice.  相似文献   

Liquid chromatographic determination of carbadox in complete feeds, premixes, and concentrates: interlaboratory study     

R M Aerts  G A Werdmuller 《Journal of the Association of Official Analytical Chemists》1988,71(3):484-490

A liquid chromatographic (LC) method previously published for the determination of carbadox in finished feeds and premixes was slightly modified and tested in an interlaboratory study. The feed samples are extracted with methanol-acetonitrile (50 + 50) after wetting with water. The extracts are purified over a short alumina column. An aliquot of the eluate is analyzed with reverse phase liquid chromatography with ultraviolet detection. Before the actual interlaboratory study, a prestudy with 2 familiarization feed samples was performed. For the interlaboratory study, 2 series of meal and pelleted samples were prepared with carbadox from different suppliers. Eight collaborating laboratories received 6 feed samples previously milled and ground and 4 pelleted samples which had to be ground by the collaborator's in-house method. Collaborators also received 3 carbadox concentrates (about 10% w/w) and 4 premix samples derived from the concentrates (about 1% w/w). Coefficients of variation under reproducibility conditions were 8.3% for meal samples and 4.9% for pellets. A minor but significant effect was noted for the influence of pelleting temperature on the carbadox content. A minor and insignificant effect was observed for the influence of the milling and grinding procedure on the carbadox content. Alumina cleanup of 1% premixes was not essential, although the resulting chromatograms were cleaner. A slight difference in reproducibility was observed with concentrates (10%) when 0.2 or 0.5 g sample size was used, although the average carbadox concentration found was the same. For premixes and concentrates, coefficients of variation under reproducibility conditions were low, ranging from 2.9 to 7.5%.  相似文献   

Surface runoff and seed trapping efficiency of shrubs in a regenerating semiarid woodland in northern Ethiopia     

Raf Aerts  Wouter Maes  Eva November  Mintesinot Behailu  Jean Poesen  Jozef Deckers  Martin Hermy  Bart Muys 《CATENA》2006

In forest restoration areas in northern Ethiopia, natural regeneration of Olea europaea ssp. cuspidata only occurs under pioneer shrubs. To assess the impact of erosion on the spatial distribution of Olea recruits, secondary dispersal of olive seeds by surface runoff was determined in and near the micro-environment of two important pioneers (Acacia etbaica and Euclea racemosa). We hypothesized that (1) Olea seeds deposited under the protective crowns of shrubs are less likely to be lost by surface wash than seeds in the bare inter-plant areas and (2) that seeds in the latter are more prone to be translocated by runoff to microsites under shrubs than to open areas.  相似文献   

Polyolefin spheres from metallocenes supported on noninteracting polystyrene   总被引：1，自引：0，他引：1  

SB Roscoe  JMJ Frechet  JF Walzer  AJ Dias 《Science (New York, N.Y.)》1998,280(5361):270-273

To obviate the destructive interaction of highly reactive metallocene catalysts with classical silica-based supports while retaining the advantage of supported catalysts, a noninteracting polystyrene support was developed. Supported catalysts for the polymerization of alpha-olefins are prepared by treating lightly cross-linked, chloromethylated polystyrene beads consecutively with a secondary amine, an ammonium salt of a weakly coordinating anion, and a neutral dialkylmetallocene. Catalytic sites are distributed homogeneously throughout the support particle, and the polymerization occurs within the bead, in contrast to traditional surface-supported metallocene catalysts. The copolymerization of ethylene and 1-hexene at 40 degreesC affords discrete spherical polyolefin beads with a size (0.3 to 1.4 millimeters) that varies according to the polymerization time.  相似文献   

Monitoring milk for chloramphenicol residues by an immunoassay (Quik‐card®)     

J. F. M. Nouws  J. Laurensen  M. M. L. Aerts 《The Veterinary quarterly》2013,33(4):270-272

Summary

An easy to perform immunoassay method (Quik‐card®) for monitoring milk on the presence of chloramphenicol residues exceeding 5 to 10 ppb is described, as well as an extraction and preconcentration method utilising a Sep‐pak® silica cartridge, which enables the detection of CAP residues in milk in concentrations exceeding 1 ppb by HPLC and 0.1 ppb by the immunoassay.  相似文献   

End-weight prediction in broiler growth     

Cangar O  Aerts JM  Vranken E  Berckmans D 《British poultry science》2006,47(3):330-335

1. Two different methods, categorised as input-output and single output models, were evaluated for slaughter weight prediction of broiler chickens. The input-output models included linear and non-linear recursive modelling with a time-varying model structure, whereas the output models consisted only of empirical growth equations and several growth curve fitting techniques. 2. The results suggested that a simple linear growth curve fitting method gives the greatest accuracy in a prediction horizon of 4 d or less. Error is minimised to an average of 0.14% when 4 d of past information is used to fit a line to predict the end weight one day ahead.  相似文献