Re-establishment of Danish streams: Restoration and maintenance measures

• 1. Prior to 1983 the Danish legislation concerning streams gave priority to drainage of water. The revision of The Watercourse Act gave balanced priority to drainage of water and environmental quality, focusing on an ecologically more appropriate maintenance practice and giving special provisions for stream restoration activities.
• 2. Different measures of single structure restoration have been used, the most common being replacement of weirs, dams or other obstacles by rapids, establishment of salmonid spawning grounds, and installation of new or improved fish ladders.
• 3. The most common stream channel restoration method is integrated use of a number of single structure measures. Establishment of a two-stage channel and re-opening of small piped streams have also been used. Stream valley restoration includes restoration of old meanders or establishment of a new sinuous channel and involves the adjacent riparian areas.
• 4. The changed stream maintenance practice involves a new strategy for dredging and cutting of weeds and bank vegetation in order to minimize the ecological damage caused by keeping a reasonable discharge capacity. In 1990, environmentally acceptable weed-cutting was performed in 37% of all municipal streams and the bank vegetation was left uncut in a third of the streams. Similarly, more than half of the county streams were maintained using hand scythes and in 74% of the streams the bank vegetation was left uncut.
• 5. Quantitatively, stream restoration has contributed little to the general improvement of Danish streams compared with changed maintenance practice. Stream restoration projects create public interest in the environmental quality of streams, but major improvements in the physical properties of Danish streams depend on future maintenance practice.
• 6. Due to major changes predicted in Danish agriculture many riparian areas and wetlands will reappear and the natural or semi-natural physical properties of streams will be re-established by natural processes or changed in maintenance practice. However, there will still be large areas with intensive agriculture, where environmental and agricultural interests must be balanced. The Danish experience has shown that this is possible.

     

Relationships between breeding waterbird abundance,diversity, and clear water status after the restoration of two shallow nutrient‐rich Danish lakes

1. Breeding waterbird communities have suffered globally from the effects of anthropogenic changes in water quality (especially nutrient enrichment) in recent decades, but few studies have demonstrated the positive effects of restorative actions.
2. Annual breeding waterbird surveys in the period 1977–2005 at two restored southern Danish lake basins (combining nutrient load reduction and biomanipulation) showed an up to five‐fold increase in abundance, and considerable changes in species richness and diversity, following restoration to clear water status in both lakes.
3. Parallel surveys at a third lake, which retained clear water quality throughout, offering a form of natural ‘control', showed no such changes over the same time period.
4. Consistent relationships between breeding waterbird abundance, species richness, and diversity with measures of water clarity (Secchi disc depth, chlorophyll a, and suspended matter) suggest that water clarity mainly drives the relationship; inverse relationships between these measures and total nitrogen and phosphorus were less consistent than for water clarity.
5. The results suggest that an improvement in water clarity plays a key role in restoring breeding waterbird communities and suggest that breeding waterbirds can be indicators of the success of lake restoration projects, but more studies are needed to confirm their wider utility under a variety of conditions.

     

Fetal Loss in a Group of Danish L x Y Sows: A Preliminary Study

Contents: The magnitude of fetal loss was studied in 13 Danish Landrace & Yorkshire (L&Y) crosses. The ovulation rate and number of fetuses were recorded following ovariohysterectomy on days 46–112 of pregnancy. On the basis of these figures the mean ovulation rate, litter size, fetal loss and transcornual migration were found to be 15.5., 12.2., 21.4% and 13.7%, respectively. It is concluded that the extent of fetal loss is smaller than expected from the literature .     

Comparison of parasite-specific immunoglobulin levels in two chicken lines during sustained infection with Ascaridia galli

Increasingly large numbers of poultry are held in production systems with access to outdoor areas. In these systems intestinal helminths are found with flock prevalences of up to 100%. Helminth infections influence chicken health negatively, which is why the following investigation has been performed.In the present experiment, 20 chickens of two inbred chicken lines containing the major histocompatibility complex (MHC) haplotypes, B14 and R5, were inoculated with 500 embryonated Ascaridia galli eggs. The A. galli-specific IgG titres of serum samples and the excretion of A. galli eggs in chicken faeces were measured for a period of 81 weeks.The level of excreted A. galli eggs measured as eggs per gram chicken faeces (EPG) varied greatly between chickens in each line. Significant differences were found between the two lines and with the R5 chickens reaching the highest levels. Likewise, the A. galli-specific IgG titres in serum differed significantly between the two lines, and an inverse relationship between infection level (EPG) and antibody titres was found. Although this inverse relationship suggests that humoral immunity may be involved in protection against A. galli infection, the high antibody titres did not prevent continued infection.     

Development of a real-time computer vision system for tracking loose-housed pigs

Changes in regulations for livestock animals will in the near future call for loose-house pig breeding systems. These new systems will increase the workload for the farmers, as location and identification of animals will require more time than before. This paper presents a real-time computer vision system for tracking of pigs in loose-housed stables. The system will ease the workload for farmers in identification and locating individual animals. The system consists of a camera and a PC. The PC runs a tracking-algorithm, estimating the positions and identities of the pigs. The tracking algorithm operates in 2 steps. The first step builds up support maps, pointing to preliminary pig segments in each video frame. In the second step the support map segments are used to build up a 5D-Gaussian model of the individual pigs (i.e. position and shape). The system has software correction for fisheye distortion coming from the camera lens. The fisheye lens allows the camera to monitor a much larger area in the stable. The algorithms are developed in MatLab, implemented in C and runs in real-time. Experiments in the lab and in the stable demonstrate the robustness of the system. The system can track at least 3 pigs over a longer time span (more than 8 min) without loosing track and identity of the individual pigs in a realistic experiment.     

Genetics and biology of cytoplasmic male sterility and its applications in forage and turf grass breeding

Hybrid breeding can exploit heterosis and thus offers opportunities to maximize yield, quality and resistance traits in crop species. Cytoplasmic male sterility (CMS) is a widely applied tool for efficient hybrid seed production. Encoded in the mitochondrial genome, CMS is maternally inherited, and thus, it can be challenging to apply in breeding schemes of allogamous self‐incompatible plant species, such as perennial ryegrass. Starting with a general introduction to the origin and the function of mitochondria in plants, this review focuses on the genetics and biology of CMS systems in plants to identify conserved and system‐specific mechanisms. We examine prospects of comparative mitochondrial genomics to identify candidate genes and causative polymorphisms associated with CMS across species and discuss specificities, obstacles and potentials of CMS as a breeding tool for maximizing heterosis in forage grasses. The purpose of the review is to highlight the importance of CMS and hybrid breeding in grasses, with the aim of facilitating research and development of novel breeding strategies to address the future needs for food, feed and biomass production.     

Bimembrane diffusion probe for continuous recording of dissolved and entrapped bubble gas concentrations in peat

Peatlands are significant sources of the important greenhouse gas CH₄ and generally known as sinks for atmospheric CO₂ through peat accumulation. Accurate measurements of the subsurface concentrations of these gases are of pivotal importance for experimental studies improving our understanding of the dynamics and controls on the exchanges of these gases between peat soils and the atmosphere. In this paper we first briefly outline examples of different probe-based techniques for the determination of subsurface gas concentrations and thereafter we document the development and testing of two different membrane probe systems. Finally we discuss a few applications of the probes and show some results obtained by testing them in the laboratory.     

Mineralization of organic contaminants under aerobic and anaerobic conditions in sludge-soil mixtures

Background and Main Features  The mineralization of eight organic chemicals (surfactants, substituted aromatic compounds, di(2-ethylhexyl)phthalate and phenanthrene) was examined in sludge-soil mixtures under aerobic, denitrifying and methanogenic conditions. Results and Discussion  Most of the chemicals were extensively or partially mineralized under aerobic conditions with mineralization half-lives between 1.5 and 12.5 days. Linear tridecyl tetra ethoxylate, di(2-ethylhexyl)phthalate and 2,4-dinitrophenol were also mineralized partially under denitrifying conditions. No mineralization of the chemicals was observed under methanogenic conditions, with the exception of a minor mineralization of linear tridecyl tetraethoxylate. Conclusion  This study indicates that the examined organic chemicals may be rapidly degraded in sludge-amended fields under aerobic conditions, and that some of the chemicals may also be degraded during denitrification. Recommendations and Outlook  When investigating the degradation of sludge-bound chemicals in soil, it is relevant to consider both aerobic and anaerobic soil regimes due to spatial and temporal variations in the redox conditions within sludge and soil. The approach presented in this article may be used for evaluation of the long-term fate of sludge-bound chemicals in soil.     

Ancient experiments: forest biodiversity and soil nutrients enhanced by Native American middens

The legacy of ancient human practices can affect the diversity and structure of modern ecosystems. Here, we examined how prehistoric refuse dumps (“middens”) impacted soil chemistry and plant community composition in forests along the Chesapeake Bay by collecting vegetational and soil nutrient data. The centuries- to millennia-old shell middens had elevated soil nutrients compared to adjacent sites, greater vegetative cover, especially of herb and grass species, and higher species richness. Not only are middens important archaeological resources, they also offer a remarkable opportunity to test ecological hypotheses about nutrient addition over very long time scales. We found no evidence, for example, that elevated nutrients enhanced invasion by non-native species as predicted by the fluctuating resource hypothesis. However, we did find that elevated nutrients shifted community structure from woody species to herbaceous species, as predicted by the structural carbon-nutrient hypothesis. These results highlight the long-lasting effects that humans can have on abiotic and biotic properties of the natural environment, and suggest the potential for modern patterns of species’ distributions and abundances to reflect ancient human activities.     

鸡群整齐度的重要性

鸡群的整齐性有益于生产性能这个观点早已得到了大家的公认。为了追求更好的整齐度,营养学家们需要在满足畜禽需要的同时尽可能减少变异、降低安全系数,从而节省饲料成本和提高动物生产性能,尽管在养殖场中提高生产效率的方法不单单减少体重变异这一种。