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51.
In the last few years, landscape researchers have sought to understand temporal and spatial patterns of landscape changes in order to develop comprehensive models of land cover dynamics. To do so, most studies have used similar methods to quantify structural patterns, usually by comparing various landscape structural indices through time. Whereas the necessity for complementary approaches which might provide insights into landscape dynamics at some finer scale relevant to local managers has been expressed, few studies have proposed alternative methodologies. Moreover, the important relationship between the physical constraints of the landscape and land use dynamics has been seldom emphasized. Here we propose a methodological outline which was applied to the study of a rural landscape of Southern Quebec, Canada, to detect spatial and temporal (1958 to 1993) patterns of land cover changes at field, patch and landscape level. We then relate these patterns to the underlying physical structure of landscape elements using GIS and canonical correspondence analyses. We use the different geomorphological deposit types as stable discriminant factors which may constrain land use.Canonical correspondence analyses showed relations of land use and land use changes to the physical attributes of the landscape elements, whereas spatial analyses revealed very dynamic patterns at finer spatial and temporal scales. They highlighted the fact that not only the physical attributes of the landscape elements but also their spatial configuration were important determinants of land use dynamics in this area. Thus more land use changes occurred at the boundary between geomorphological deposit types than in any other locations. This trend is apparent for specific small-size changes (e.g. forest to crop), but not for the large-size ones (e.g. abandoned land to forest). Although land use changes are triggered by socioeconomic forces in this area, these changes are nevertheless constrained by the underlying physical landscape structure. A thorough comprehension of historical changes will enhance our capability to predict future landscape dynamics and devise more effective landscape management strategies. 相似文献
52.
Effect of precalving intramammary treatment with pirlimycin in nulliparous Holstein heifers 总被引:2,自引:0,他引:2 下载免费PDF全文
Jean-Philippe Roy Denis Du Tremblay Luc DesCteaux Serge Messier Daniel Scholl mile Bouchard 《Canadian journal of veterinary research》2007,71(4):283-291
A clinical trial was conducted to determine whether prepartum intramammary pirlimycin reduces the proportion of nulliparous heifers with intramammary infection (IMI) during early lactation and improves milk production. Quarter milk samples were collected from 428 heifers, systematically allocated to treatment and control groups, 6 to 12 d before the expected calving date and 2 to 8 d after calving. At the prepartum visit, heifers in the treatment group (n = 219) received an infusion of pirlimycin hydrochloride in all 4 quarters; the control heifers (n = 209) received no infusions. Intramammary infection was detected in 69% of the heifers and 33% of the quarters before calving. After calving, the proportion of treated heifers with IMI was significantly lower than the proportion of control heifers (31% versus 45%). Staphylococcus aureus was isolated from 10% of the heifers and 3% of the quarters before calving. After calving, the proportion of IMIs due to S. aureus was significantly lower in the treated heifers than in the control heifers (5.6% versus 10%). Antibiotic treatment increased the percentage of cures and prevented new IMIs caused by gram-positive bacteria after calving. The incidence of new IMIs caused by gram-negative bacteria and yeast was higher among treated heifers than among control heifers. There was no overall effect of treatment on milk production, but there was a significant interaction effect of treatment and the interval between treatment and calving. An increase of 302 kg of milk was observed when antibiotic treatment was applied more than 1 wk before calving. Treatment did not affect the milk somatic cell count on the 1st 3 test days after calving. 相似文献
53.
Taking into consideration ecological aspects in land management requires an understanding of the processes and dynamics that
create landscapes. To achieve this understanding demands that landscapes be studied as a biophysical and social reality, and
that phenomena be analyzed within a historical perspective. Based on the research of a multidisciplinary team over the last
25 years, this paper proposes to reconstitute the landscape of Godmanchester (Quebec, Canada) from the pre-colonial period
(1785) to today (2005). Using various methods and sources of data, seven stages of evolution were identified: (1) the pre-colonial
period, (2) the first settlements, (3) the first agricultural developments, (4) the maximum development of agricultural activities,
(5) the concentration of agricultural activities, (6) the intensification of agricultural activities, and (7) the importance
of new amenities. First, these results allowed us to identify three sets of fundamental factors that are necessary to understanding
the landscape changes, the geomorphological characteristics, the socio-economic demands, and the technological transformations.
Second, the results highlight the key elements and the perspectives that are appropriate to their comprehension, in order
to be able to direct the future evolution of the landscapes. This requires that transformations be analyzed from mid-term
to long-term perspectives, that the consequences of the changes, as well as the opportunities that they generate, are well
understood, and finally that relationships be drawn between the biophysical, anthropic, and technological factors responsible
for these transformations. This paper concludes with the idea that the creation of landscapes occurs through actions brought
about by social demands and by the adjustment of technologies according to the biophysical characteristics of the territories. 相似文献
54.
A multiscale framework for landscape analysis: Object-specific analysis and upscaling 总被引:13,自引:0,他引:13
Landscapes are complex systems that require a multiscale approach to fully understand, manage, and predict their behavior. Remote sensing technologies represent the primary data source for landscape analysis, but suffer from the modifiable areal unit problem (MAUP). To reduce the effects of MAUP when using remote sensing data for multiscale analysis we present a novel analytical and upscaling framework based on the spatial influence of the dominant objects composing a scene. By considering landscapes as hierarchical in nature, we theorize how a multiscale extension of this object-specific framework may assist in automatically defining critical landscape thresholds, domains of scale, ecotone boundaries, and the grain and extent at which scale-dependent ecological models could be developed and applied through scale. 相似文献
55.
E Bouchard D Daignault D Blanger Y Couture 《The Canadian veterinary journal. La revue veterinaire canadienne》1994,35(12):770-774
A retrospective study on 159 cesareans on dairy cows referred between 1985 and 1989 to the veterinary teaching hospital is reported. The objective of the study was to evaluate the probability and the factors associated with survival and subsequent calving. The risk of dying for the cows was 24% following surgery. The risk of dying differed if the cow had an emphysematous, dead, or live calf; it was 63%, 21%, and 14%, respectively. Of all the cows returned to the farm and for which there was a breeding recorded, 64% calved again. But only 28% of all the cows returned home and, therefore, only 17% of all the referred cases calved again. We used multivariate analysis to obtain a predictive model on prognosis following surgery. The prognosis was only influenced by the calf condition at admission. 相似文献
56.
In agricultural landscapes, most studies have investigated the influence of the spatial pattern of forest patches on other ecological phenomena and processes, such as animal movement and biodiversity. However, few have focused on explaining the spatial pattern of the forest patches themselves. Understanding how these patterns relate to the processes that generate them is fundamental in developing a sound theory of landscape ecology, and in devising rational management strategies. In this paper, the pattern of the overall forest patches, as well as the pattern of deciduous and coniferous patches in an agricultural landscape of Southern Quebec, Canada, were analyzed and related to landscape physical attributes and land use, using remote sensing, geographic information systems and statistical methods. Results show that the role of landscape physical attributes on forest patch pattern has been modified by land use. In the study area, coniferous or deciduous patches are not associated with a specific surface deposit. In addition, physical attributes explain only a small proportion of the abundance of conifers on past abandoned land compared with land-use factors. Physical attributes only indirectly influence the forest pattern because they strongly influence the land-use practices. Our results reveal a conifer recovery process with the abandonment of agricultural land. On past abandoned land, conifers expand with increasing stand age, mostly by invasion from neighboring coniferous patches. Spatially, coniferous patches are usually located on the margins of the overall forest patches, and they are connected to non-forest land-use types such as crop and pasture, the latter being the most important. By showing the importance of some coniferous forest types that did not exist in the precolonial forest, a new perspective emerges when landscape, especially, land-use dynamics are taken into account. 相似文献
57.
Recurrent and synchronous spruce budworm (SBW) outbreaks have important impacts in boreal and sub-boreal forest ecosystems of North America. This study examines the early phase of an outbreak that was developing across a 268,000 km2 area over a period of 9 years (2003–2011). The territory was subdivided in 225 km2 cells, and the relative influence of forest composition, elevation, forest age, average degree-days and soil drainage were examined during three development phases of the outbreak: initial epicenter location, relatively long-distance spread (cell-to-cell expansion), and expansion inside individual cells (within-cell expansion). The results indicate that elevation is the most determinant variable for initial epicenter location. Other variables that were identified as important for outbreak development by previous studies, such as forest composition and average degree-days, were not so important during this phase. However, forest composition and average degree-days were important factors during the cell-to-cell and within-cell expansion phases. Separating outbreak development in distinct phases also allowed to integrate phase-specific spatial and temporal covariates that were highly significant in the models, such as distance from previous year defoliations during the cell-to-cell expansion phase, and the proportion of defoliated stands during the preceding year for the within-cell expansion phase. Overall, this study provides limited evidence that patterns of SBW outbreak expansion could be altered by reducing host tree species abundance in the forest [mainly balsam fir (Abies balsamea) in this region]. More generally, this study suggests that the influence of environmental variables on SBW outbreak development is clearly phase-dependent, and that this landscape-level, process-based approach could be useful to forecast insect outbreak development in forest ecosystems. 相似文献
58.
59.
•Introduction
The agricultural landscape in Eastern Canada has drastically changed in the last decades. Whilst certain forest communities are disappearing, post-agricultural forests are emerging from old fields colonized by fast-growing tree species. 相似文献60.
Comparison of feed intake,body weight gain,enteric methane emission and relative abundance of rumen microbes in steers fed sainfoin and lucerne silages under western Canadian conditions 下载免费PDF全文
K. Bouchard K. M. Wittenberg G. Legesse E. Khafipour K. E. Buckley K. H. Ominski 《Grass and Forage Science》2015,70(1):116-129
Beef cattle are major contributors of enteric methane (CH4) emissions in Canada. Feeding forages containing condensed tannins (CT) has been suggested as a means of reducing enteric CH4 emissions and improving production efficiency. Sainfoin (Onobrychis viciifolia) is one of the CT‐containing legumes, which has also been recognized to have several additional beneficial properties. This study compared sainfoin silage (SS) and lucerne (Medicago sativa) silage (LS) with respect to animal performance, enteric CH4 production, abundance of selected rumen microbes and selected serum parameters in yearling steers during a Canadian winter. Sainfoin silage in our study contained approximately 12 g CT kg?1 dry matter (DM), a level which did not adversely affect silage palatability as steers fed SS experienced higher DM intake. However, animals fed LS and SS had similar body weight gain over the course of the trial. Feeding SS resulted in lower blood urea nitrogen concentrations and relative abundance of methanogenic archaea in rumen fluid. Yet, microbial population shifts fell short of exerting significant influence on enteric CH4 emissions. This study suggests that under western Canadian growing and animal‐rearing conditions, sainfoin is not yet competitive with lucerne forage with respect to enteric CH4 emissions or animal productivity warranting further research and development. 相似文献