Influence Of Shelter Research Articles

The influence of shelter on abundance of the invasive dandelion, Taraxacum officinale, at its northern range limit

The influence of shelter on abundance of the invasive dandelion, Taraxacum officinale, at its northern range limit

Spatial behaviour of sheep during the neonatal period: Preliminary study on the influence of shelter

Effective shelter has been demonstrated to reduce neonatal lamb mortality rates during periods of inclement weather. Periods of high wind speed and rainfall have been shown to influence shelter usage; however, it is not yet known how ewe factors such as breed, age and body condition score influence shelter-seeking behaviour. This study, conducted on a working upland farm in the UK, examined impact of artificial shelter on the biological and climatic factors that influence peri-parturient ewe behaviour. Pregnant ewes (n = 147) were randomly allocated between two adjacent fields which were selected for their similarity in size, topography, pasture management, orientation to the prevailing wind and available natural shelter. In one field, three additional artificial shelters were installed to increase the available shelter for ewes, this field was designated the Test field; no additional artificial shelter was provided in the second field which was used as the Control field. Individual ewes were observed every 2 h between 0800 and 1600 for 14 continuous days to monitor their location relative to shelter. Ewe breed (Aberfield and Highlander), age (2–8 years) and body condition score were considered as explanatory variables to explain flock and individual variance in shelter-seeking behaviour and the prevalence of issues which required the intervention of the shepherd, termed ‘shepherding problems’. Any ewe observed with dystocia, a dead or poor vigour lamb or who exhibited mismothering behaviour was recorded as a shepherding problem. The prevalence of these shepherding problems which necessitate human intervention represents arguably the most critical limiting factor for the successful management of commercial sheep flocks in outdoor lambing systems. Overall, ewes in the Test field with access to additional artificial shelter experienced fewer shepherding problems than those in the Control field (P < 0.05). A significant breed effect was also observed, with Highlander ewes more likely to seek shelter than Aberfield ewes (P < 0.001), and experiencing significantly fewer shepherding interventions (P < 0.05). These findings demonstrate the substantial and significant benefits to animal welfare and productivity that can be achieved through the provision of shelter in commercial, upland, outdoor lambing systems in the UK.

Reproductive success of Atlantic salmon (Salmo salar) mature male parr in a small river, the Nivelle: influence of shelters

Grimardias D, Merchermek N, Manicki A, Garnier J, Gaudin P, Jarry M, Beall E. Reproductive success of Atlantic salmon (Salmo salar) mature male parr in a small river, the Nivelle: influence of shelters. Ecology of Freshwater Fish 2010: 19: 510–519. © 2010 John Wiley &amp; Sons A/SAbstract – The breeding activity of a small population of Atlantic salmon (Salmo salar L.) was monitored on the Nivelle River in southwest France to estimate the overall contribution of mature male parr and the numbers involved in egg fertilisation. In the twelve redds sampled, 563 eggs were collected for parental assignment and the physical habitat was characterised to investigate the possible relationship between parr reproductive success and habitat complexity. The overall contribution of mature male parr was particularly high (87%, one of the highest estimates ever reported). Concerning habitat complexity, granulometry and shelter diversity were correlated with the number of parr breeders contributing to egg fertilisation in each redd. A complex habitat increased multiple paternity, which could affect the effective size and genetic variability of small salmon populations.

Influence of shelters and food resources on smoltification of juveniles of the Atlantic salmon Salmo salar

Influence of feeding conditions and of the presence of a various number of shelters in basins on development of differentiation of juveniles of Salmo salar at the age 1+ and formation of smolts were studied under experimental conditions. The experiments had been carried out on groups of ten fish. The influence of investigated factors turned out to be significant. Under normal feeding four times a day, the quantity of formed smolts depends on the number of shelters: the more shelters that are available, the fewer smolts appear in groups. The presence of one shelter is a strong stimulant enhancing aggressive activity towards conspecific individuals, resulting in destruction of some fish in the group. Under feeding once a day, i.e., under food shortage, more fish perished, and the number of smolts decreased as the fish did not accumulate a sufficient energy potential for the morphophysiological transformation. One of the potential mechanisms of development of differentiation of fish juveniles into parrs and future smolts is discussed, based on domination of some fish possessing the individual territory and exclusion of subdominant specimens into open water as a result of social interaction.

Optimal spatial harvest planning under risk of windthrow

This study solves the problem of optimal spatial harvest planning when forest stands are faced by risk of windthrow and the risk depends explicitly on the features of the stand and its neighbours as well as on the geographical structure and orientation of the forest. First, we estimate the optimal rotation age and expected net present value for a range of discount rates and windthrow hazards for an unprotected stand. Next, the influence of shelter is evaluated for a ‘forest’ with two stands. Two different windthrow probability models are analysed. Relative to the one-stand case, the optimal rotation age and the corresponding net present value change significantly when an extra stand is included. This is due to the shelter effect reducing the risk of windthrow. Shelter also increases the optimal rotation age from the lower limit, being the optimal rotation age of a single stand, towards the upper limit being the case without risk. The optimal rotation age is shown to depend on geographic orientation as well as the age difference between the two stands of the ‘forest’. For forests with a higher number of stands, the optimal rotation ages may increase considerably due to the shelter effect. To illustrate this, we investigate the optimal harvest policy for a ‘forest’ with four stands where one of the stands is surrounded by the three others. The sensitivity towards geographic orientation is again analysed. Finally, a ‘forest’ with 16 stands is investigated to exemplify how an optimal short-term policy can be identified for an even higher number of stands, though the optimal harvest ages cannot be calculated within reasonable time.

Alternative reproductive tactics in atlantic salmon: factors affecting mature parr success

In Atlantic salmon, as in most salmonids, males can mature early in the life cycle, as small freshwater fish, termed parr, and/or undergo a sea migration before maturing as full–size adults. The alternative life histories are contingent on environmental and social circumstances, such as growth rate, territory quality or any other factor that affects the individual9s state. In order to model the choice of life history in this group of commercially valuable species, it is necessary to understand not only the relative contribution of the different male types to subsequent generations, but also to know the factors that affect reproductive success in each type. In this paper we present the results of a study designed to investigate the factors that affect the reproductive success of mature parr. We used highly polymorphic minisatellite DNA markers to analyse paternity in a series of mating experiments where the number and body size of parr were manipulated. The fraction of eggs fertilized by mature parr ranged from 26 to 40 per cent, with individual parr fertilizing up to 26 per cent of the eggs. A strong positive correlation was found between parr size and reproductive success. The relative success of parr decreased with increasing parr number. Data from this and other studies on variation in the timing and degree of parr reproductive success are discussed in relation to the evolution of male mating strategies and life history in salmonids.

Influence of shelter on night temperatures, frost damage, and bud break of white spruce seedlings

Measurements of frost damage and bud-break phenology were made during the spring of 1993 and 1994 on planted white spruce (Piceaglauca (Moench) Voss) seedlings and on trembling aspen (Populustremuloides Michx.) suckers in combination with measurements of minimum air temperature and long-wave radiation in forest openings of different sizes and configurations (1.5-ha clearcut, 9 and 18 m wide strips, 9 and 18 m diameter circular openings and intact forest) near Chapleau, Ontario. The average minimum air temperature during early summer (May–June) decreased linearly as the sky view factor of the forest openings increased. The average difference in minimum air temperature between the forest and clearcut opening was nearly 3 °C for the period, and during clear night sky conditions, this temperature difference approached 6 °C. The difference in minimum temperature between the forest and clearcut during cloudy night sky conditions was slightly greater than 1 °C. Differences in minimum air temperature between the forest and each of the openings increased with decreasing incoming long-wave radiation. The largest differences occurred between the forest and the clearcut with low incoming long-wave radiation (cloudless nights). Minimum air temperatures in the 9-m strip and 9-m circle differed little from minimums in the forest under all long-wave radiation regimes. Moderation of air temperature on clear nights would be best achieved with sky view factors of less than 0.3, implying a maximum strip width of 0.6 tree heights and a maximum patch diameter of 2.2 tree heights. Damage to white spruce seedlings after a frost in the spring of 1993 increased with increasing sky view factor. Nearly 75% of the seedlings in the clear-cut had medium or heavy frost damage, while only 2% of the seedlings in the 9-m circle and forest were frost damaged. Opening size and configuration had little influence on the timing of bud break in either the white spruce seedlings or the trembling aspen suckers.

Role of some environmental variables in trout abundance models using neural networks

Neural networks provide a black box model for explaining and predicting trout abundance with 8 environmental variables. This work investigates the specific effect of each variable, by inputting fictitious configurations of explanatory variables and by checking the responses of the model. The comparison between this response of the model to environmental variables on one hand, and results from field observations on the other hand, shows similarities and indicates neural network modelling can be trusted. The elevation appears to be the major explanatory factor. The influence of shelters, bottom velocity and Froude number also play an important role. When considered separately, depth does not have a notable influence on the density of trout. Such confirmations of field observations suggest that these models can be used to obtain a clear identification and hierarchization of the factors influencing the abundance of trout and the mode of action of the factors. This approach can be extended to other applications in quantitative ecology in which non-linear relationships are usually observed.

Influence of shelter on soil sorting by wind erosion — a case study

Textural analyses were conducted in order to quantify the soil status in two nearby fields with 80 m and 200 m spacing of shelter hedges. Surface soil samples in the more wind exposed field show a significantly ( P < 0.001) lower content (approximately 8%) of silt + clay particles (< 0.063 mm) compared to the more sheltered field. A different intensity of wind erosion between the fields over a period of approximately 45 years (since shelter hedges in the area were high enough to act as windbreaks) is stipulated to account for the difference in soil composition. Also, in samples taken at a depth of 0–25 cm, a lower proportion (approximately 4%) of silt + clay material is observed. Here the difference is explained by ploughing of the wind eroded surface, causing a recurring downward transport of remaining coarser particles. Soil samples collected in 1988 and 1990 indicate that the progression toward a coarser soil texture is not linear, but rather fluctuates between the seasons owing to a varying wind climate, crop cover and soil conditions. Whereas no spatial pattern was apparent in the wind-exposed field, samples taken from the sheltered field showed a lower content of fine particles both at the surface and at 0–25 cm beneath the surface in the central and southeastern parts. This indicates that these parts have been most exposed to wind erosion, which is consistent with the orientation of the shelter hedges and the dominating wind erosion directions.

Influence of Shelter and Feeding Practices on Channel Catfish Fingerling Production

Abstract The influence of shelter and two feeding methods on the growth, yield, survival, and feed conversion of channel catfish (Ictalurus punctatus) was investigated. Channel catfish fry (mean, 0.035 g) were stocked into earthen ponds at 378,600 fish/hectare. Six 400-m2 ponds had a l-m × 1.5-m floating rubber mat as a shelter and six had no shelter. Feed was given in the form of moist, 10-cm-diameter balls or as a dry crumbled feed twice a day at an initial rate of 5 kg/hectare. The greatest net yield of fingerlings was obtained where no shelter was provided and feed was given as crumbles. Average net yield was 116.9 kg/hectare greater in ponds without shelter. Ponds receiving a crumbled feed had a 113.7 kg/hectare greater net yield than those given a moist feed ball. Survival was 18.9 percentage points greater in ponds without shelter.

The influence of shelter and the hypothetical effect of fire severity on the postfire establishment of conifers from seed

Surface-charred organic matter is a common but unfavourable postfire seedbed in eastern Canada. Slatted screens providing 0, 25, 50, and 75% cover were used to shelter 1-m2 charred plots from direct sunlight. Plots were sown with four conifer species. Jack pine (Pinnsbanksiana Lamb.) established abundantly on all plots and dominated on unsheltered areas. As shelter increased, eastern white pine (Pinusstrobus L.), and eventually balsam fir (Abiesbalsamea (L.) Mill.) and black spruce (Piceamariana (Mill.) B.S.P.) increased in number. Thus, the size and composition of the seedling community depended upon the amount of shelter given. To test whether postfire herbaceous and shrub vegetation could have a similar effect, seeds were sown on pairs of charred 1-m2 plots. Vegetation was removed weekly from one plot of each pair. Removal of vegetation decreased the establishment of balsam fir and black spruce but not red pine (Pinusresinosa Ait.). It was concluded that, during the first growing season, changes in vegetation cover produce changes in establishment similar to those found using slatted screens. Increasing fire severity (organic matter consumption) may reduce the postfire vegetation cover. A hypothetical model is presented, linking the establishment of the above five species to fire severity.

The Influence of Shelter and Weeds on Early Growth of Sitka Spruce and Lodgepole Pine

The Influence of Shelter and Weeds on Early Growth of Sitka Spruce and Lodgepole Pine