Influence Of Spatial Position Research Articles

Interrelation between the straw chopping length and the design of straw chopper

The article deals with the process of straw chopping in straw chopper of a combine harvester. It shows the influence of straw chopper design on the straw chopping length; in particular the influence of spatial position of straw at the moment of its cutting, and of spacing of knives setting, on the chopping length. The possible variations of straw motion with chopping rotor knives after its chopping on the shearbar are described. The nature of motion of uncut straw with the chopping rotor, and the forces acting on the straw that slides over the rotor knives, are also described. The dead zone in the straw chopper is determined; it is an area between the body of chopper and the working surface of chopping rotor knives. Motion of straw in the dead zone does not lead to its chopping, because of the lack of possibility of its contact with rotor knives. The necessity of introducing of complementary units on the low wall of straw chopper body is substantiated; it leads to the intensification of straw chopping process by means of removing the straw flow from dead zone and increasing the probability of straw contact with rotor knives. The location of such units is determined. Reorientation of straw flow before and during its chopping not only reduces the straw chopping length, but also leads to the reduction of power consumed by straw chopper. This is due to both the reduction in cutting area, and the reduction in inertia of chopping rotor, because of decrease in number of knives.

Community structure of dung beetles in Amazonian savannas: role of fire disturbance, vegetation and landscape structure

Understanding the relative influence of environmental and spatial variables in driving variation in species diversity and composition is an important and growing area of ecological research. We examined how fire, local vegetation structure and landscape configuration interact to influence dung beetle communities in Amazonian savannas, using both hierarchical partitioning and variance partitioning techniques to quantify independent effects. We captured a total of 3,334 dung beetles from 15 species at 22 savanna plots in 2003. The species accumulation curve was close to reaching an asymptote at a regional scale, but curves were variable at the plot level where total abundance ranged from 17 to 410 individuals. Most plots were dominated by just three species that accounted for 87.7% of all individuals sampled. Hierarchical partitioning revealed the strong independent and positive effect of percentage forest cover in the surrounding landscape on total dung beetle abundance and species richness, and richness of uncommon species and the tunneler guild. Forest cover also had a negative effect on community evenness. None of the variables that related to fire affected community metrics. The minimal direct influence of fire was supported by variance partitioning: partialling out the influence of spatial position and vegetation removed all of the individual explanation attributable to fire, whereas 8% of the variance was explained by vegetation and 28% was explained by spatial variables (when partialling out effects of the other two variables). Space-fire and vegetation-fire joint effects explained 14 and 10% of the dung beetle community variability, respectively. These results suggest that much of the variation in dung beetle assemblages in savannas can be attributed to the spatial location of sites, forest cover (which increased the occurrence of uncommon species), and the indirect effects of fires on vegetation (that was also dependent on spatial location). Our study also highlights the utility of partitioning techniques for examining the importance of environment variables such as fire that can be strongly influenced by spatial location.

The distribution of pond snail communities across a landscape: separating out the influence of spatial position from local habitat quality for ponds in south-east Northumberland, UK

Ponds support a rich biodiversity because the heterogeneity of individual ponds creates, at the landscape scale, a diversity of habitats for wildlife. The distribution of pond animals and plants will be influenced by both the local conditions within a pond and the spatial distribution of ponds across the landscape. Separating out the local from the spatial is difficult because the two are often linked. Pond snails are likely to be affected by both local conditions, e.g. water hardness, and spatial patterns, e.g. distance between ponds, but studies of snail communities struggle distinguishing between the two. In this study, communities of snails were recorded from 52 ponds in a biogeographically coherent landscape in north-east England. The distribution of snail communities was compared to local environments characterised by the macrophyte communities within each pond and to the spatial pattern of ponds throughout the landscape. Mantel tests were used to partial out the local versus the landscape respective influences. Snail communities became more similar in ponds that were closer together and in ponds with similar macrophyte communities as both the local and the landscape scale were important for this group of animals. Data were collected from several types of ponds, including those created on nature reserves specifically for wildlife, old field ponds (at least 150 years old) primarily created for watering livestock and subsidence ponds outside protected areas or amongst coastal dunes. No one pond type supported all the species. Larger, deeper ponds on nature reserves had the highest numbers of species within individual ponds but shallow, temporary sites on farm land supported a distinct temporary water fauna. The conservation of pond snails in this region requires a diversity of pond types rather than one idealised type and ponds scattered throughout the area at a variety of sites, not just concentrated on nature reserves.

On putting the horse before the cart: Exploring conceptual bases of word order via acquisition of a miniature artificial language

In four experiments using preschool children, congruence between reference fields and name order in a miniature artificial language (MAL) was studied. In Experiment 1 the subjects learned names for two horses and two carts, and subsequently tried to learn an MAL using the names presented either in the horse-cart order or in reverse order (cart before horse). The former was more easily learned. In Experiment 2 the possible influence of spatial position and animacy in producing the effect was examined by using toy graders and toy boulders, with the former pushing the latter. Name order which represented grader plus boulder was more easily learned than the reverse (boulder name followed by grader name), suggesting that a property such as agency determines ease of acquisition. Experiments 3 and 4 repeated the first two, but using Fijian children. Fijian languages are considered to be subject-final. The patterns of results were the same as for English-speaking children, indicating that the effects are not dependent upon knowing English, a subject-initial language. The results are discussed in terms of possible semantic bases of word ordering, and are seen as giving support to a “naturalness” position, which asserts that it is appropriate to refer first to agents, then patients. They are also seen as contributing to the debate on whether semantically based word combinations in early language acquisition might serve as a device assisting entry to fully syntactic forms.