Gérald Domon

Temporal (1958–1993) and spatial patterns of land use changes in Haut-Saint-Laurent (Quebec, Canada) and their relation to landscape physical attributes

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.

Changing ruralities, changing landscapes: exploring social recomposition using a multi-scale approach

Abstract Changes in agricultural practices have led to declines in the farming population and significant changes within the landscape. Paradoxically, many rural areas are recording significant demographic growth. Given the extent of rural areas experiencing these changes, little attention has been devoted to the relationship between rural migration processes and landscape developments. Therefore, the various rural dynamics resulting from these phenomena merit closer investigation. Moreover, we should explore these complex processes at scales where they are most evident. Through the multi-scale research approach used in this study, these processes are investigated in their regional, local, and domestic contexts. As shown by regional typological outlines, the great diversity of the rural areas indicates an increasing dissociation between the agricultural and socio-demographic trajectories. From our local-scale study, changes in lot occupation revealed new residential settlement patterns induced by an influx of in-migrants. Specific landscape characteristics seem to be a determining force shaping these population flows. At the same time, these population movements have dissimilar influences on evolving landscape dynamics. With the exception of isolated agricultural abandonment trajectories, migrant relocation does not seem to affect specific local-scale land use development. However, it is significantly associated with individual domestic practices. These practices are indicative of the migrants identity in the rural landscape; further, they suggest specific values for the landscapes qualitative dimensions. These emerging urban and non-farming interests in rural landscapes challenge planning policies to guide the landscapes evolution for the benefit of its “producers” and “consumers”.

Vegetation Composition and Succession of Abandoned Farmland: Effects of Ecological, Historical and Spatial Factors

In North America, as well as in Europe, the mechanization and the modernization of the agricultural activities had strongly modified the agricultural landscapes. Originating from these transformations of the agricultural environment, abandoned farmlands remain poorly known environments. A holistic approach, including the analysis of ecological, historical and spatial factors, is used in order to understand the dynamics of these environments created by agricultural abandonment in southwestern Québec (Canada). The analysis of 36 abandoned farmlands in the study area reveals the existence of two ecological groups. The first ecological group is composed by abandoned farmlands originating from pasture and at the moment dominated by a spiny shrub vegetation. The second ecological group includes past cultivated field at the moment dominated by either hydric herbaceous and shrub vegetation. Abiotic ecological variables such as slope, surface stoniness, canopy opening and soil pH, as well as land-use history, and age of the abandoned farmlands, are major factors explaining the current state of abandoned farmlands. Succession vector analysis reveals a strong differentiation among abandoned farmlands as to their tree species regeneration. Possible management alternatives, such as reforestation, are proposed in order to integrate those new environments to the modern agricultural landscape.

Environmental, historical, and contextual determinants of vegetation cover: a landscape perspective

We formulated and tested models of relationships among determinants of vegetation cover in two agroforested landscapes of eastern North America (Haut Saint-Laurent, Quebec, Canada) that differed by the spatial arrangement of their geomorphic features and intensity of agricultural activities. Our landscape model compared the woody plots of each landscape in terms of the relative influence of environmental attributes, land use history (1958 – 1997), and spatial context (i.e., proximity of similar or contrasting land cover). Our vegetation model evaluated the relative contribution of the same sets of variables to the distributions of herbs, trees, and shrubs. Relationships were assessed using partial Mantel tests and path analyses. Significant environmental and contextual differences were found between the vegetation plots of the two landscapes, but disturbance history was similar. Our vegetation model confirms the dominant effect of historical factors on vegetation patterns. Whereas land-use history overrides environmental and contextual control for trees, herbaceous and shrub species are more sensitive to environmental conditions. Context is determinant only for understory species in older, less-disturbed plots. Results are discussed in relevance to vegetation dynamics in a landscape perspective that integrates interactions between environmental and human influences.

Factors affecting plant species distribution in hedgerows of southern Quebec.

Abstract Woody linear features of farmlands have received much attention as pools of diversity in European countries, but they have, in comparison, been little considered in eastern North American ecological studies. Here, we evaluate the relative contribution of environmental conditions, history of management practices within hedgerows, and adjacent land-use on herb and shrub species distribution in woody hedgerows of agricultural landscapes of southern Quebec, Canada. We pay particular attention to the distribution of forest herbs and weed species and identify the main factors that explain their presence. We also evaluate the amount of spatial structuring in the species data and explanatory variables. Our results show significant differences in species composition related to the unique influence of all sets of factors considered. Adjacent land-use (from intensive crop to fallow land) remains the best predictor of overall species distribution, followed by environmental conditions and history of management practices. The probability of finding forest herbs in hedgerows increases as intensity of adjacent agricultural practices (from intensive crop to fallow land) decreases. Potential weed species, on the other hand, are more likely to be found within narrow hedgerows adjacent to the more intensively managed fields. We discuss the results in terms of the interactions between the different determinants of plant diversity in hedgerows and demonstrate the necessity to distinguish between multiple structuring factors to devise proper conservation strategies. Such strategies will have to take into account the ecological as well as the agricultural exploitation context in which linear features are found to be effective.

Influence of edaphic factors on the spatial structure of inland halophytic communities: a case study in China

In order to understand the influence of edaphic factors on the spatial structure of inland halophytic plant communities, a 2.6 km2 study site, located on the lower fringe of the alluvial fan of the Hutubi River, in an arid region of China, was sampled and mapped. 105 patches were found to be homogeneous in species composition. Plant species and their coverage were recorded in each patch. 45 patches were randomly selected for the measurement of edaphic variables. A map with quadrat locations and boundaries of patches was digitized into a GIS and related to the vegetation and edaphic data matrices. CCA was used to evaluate the relative impor- tance of edaphic factors in explaining the variation of the species assemblages and to identify the ecological preferences of species. The spatial structure of the communities and the main edaphic factors were analyzed using correlograms, Man- tel correlograms and clustering under constraint of spatial contiguity. Gradient analysis showed that there are two distinct veg- etation gradients in the study area, one of which is determined mainly by soil moisture (determined by depth to the water table), and the other by soil salinity (determined by electrical conductivity and hydrolytic alkalinity of the first soil layer). However, spatial analyses showed that at the sampling scale the halophytic communities in the study area are structured along one main spatial gradient determined by the water table level. Similar spatial autocorrelation structures between the factors related to the first soil layer and the communities, given our sampling scale, could not be detected. Our results suggest that the relative importance of the effects of different edaphic factors on the spatial structure of halophytic commu- nities is scale-dependent. The partitioning of species variation indicates that in addition to edaphic factors, other factors, such as biotic interactions, may play an important role in structur- ing these communities.

The transformations of the natural landscapes of the Haut-Saint-Laurent (Québec) and their implications on future resource management

Abstract Owing to its late colonization, (circa 1800), the region of the Haut-Saint-Laurent of Quebec is of high interest for the study of the transformations of the natural landscapes of North-Eastern America. Fourteen years of work by a multidisciplinary team and the utilization of some little-used data sources (notary deeds, nominative censuses), make the considerable scope of these changes evident. First, wetlands have been altered by human activities to the point that alder scrub is invading the marshes and black spruce has been eradicated from the bogs. Secondly, after a rapid expansion during the 19th century, agricultural use is now in steady decline on areas covered by morainic deposits. Thirdly, forest exploitation has changed precolonial vegetation to the point that what was once perceived as a climatic climax (sugar maple-hickory) is now understood to be an anthropic climax. Overall, the various studies discussed in this paper lead to the conclusion that todays Haut-Saint-Laurent landscapes are in need of reconstruction. This reconstruction must take into account the new rural context, where agriculture is no longer the dominant activity, and must utilize the theories and methods of landscape ecology.

Analysis of landscape pattern change trajectories within areas of intensive agricultural use: case study in a watershed of southern Québec, Canada

This study aimed at capturing the spatial variability of landscape patterns and their trajectories of change from 1950 to 2000 within a watershed, which is representative of areas of intensive agricultural use. After an analysis of landscape features changes for the entire watershed based on aerial photographs, hierarchical clustering analysis provided a typology of landscape patterns for the cadastral lots. Following that, the trajectory of change of each lot was characterized (nature, importance, direction, rate of change). Seven types of landscape patterns are distinguished by the relative importance of different classes of landscape features and 51 trajectories of change were identified for the lots. The analysis shows that although the majority of lots were subjected to a homogenization of their landscape patterns since 1950, this trend is not entirely uniform and that since 2000 it occurs alongside trends towards diversification of certain landscape features on some lots. Furthermore, nearly a third of the lots are not following the main trajectories of change detected. Thus, the results suggest that extrinsic forces (policies, technologies) that are directing main changes in areas of intensive agricultural use toward uniformity could be modulated by internal forces (uses and values of the population). A better understanding of theses internal forces seems crucial to manage landscapes. From a methodology standpoint, although the hierarchical clustering analyses appear useful for understanding the spatial and temporal variability of landscape patterns, particular attention must be given to validating the typology chosen to characterize them.

The dynamics of the forest landscape of Haut-Saint-Laurent (Quebec, Canada): interactions between biophysical factors, perceptions and policy

Abstract Whereas the environmental consequences of changes in the agroforestry landscape are becoming better documented, an understanding of the factors which lead to these changes is proving more than ever necessary. Only such an understanding can help to identify the appropriate strategies that will take these consequences into account. The present paper shows how such an understanding can be reached through a simultaneous analysis of the landscape from historical, biophysical, social and contextual perspectives. To do so, an analytical model that takes into account those perspectives is presented and used for analysing the major changes which have marked the wooded portion of the agroforestry landscape in southern Quebec. The model first reveals the obvious underutilization of the forestry potential of the area and the extreme vulnerability of the woodlands with regard to agricultural usage. It then shows that, although the essentially agricultural perception of the land held by the landowners seems at stake, the phenomena observed are intimately linked with the historical relationship between the biophysical characteristics of the territory and the context in which its resources are exploited. The scarcity of conifers and the poor quality of deciduous stands coupled with the importance of programmes aimed at boosting agricultural production have turned the woodlands into residual agricultural areas. While the necessity of increasing forest production on privately held forest lands is now acknowledged, the strategies now being developed will have to give consideration simultaneously to the social, biophysical and political components. Specifically, they should emphasize the relative importance of the private forest and pay attention to the individuals most likely to undertake forestry activities. They must also accord priority to the development of woodlots which, while presenting the highest long-term production potential, offer the least production constraints in the short term. Finally, they should promote management practices that make for the improvement of the stands (clearing, thinning, etc.).

The landscape history of Godmanchester (Quebec, Canada): two centuries of shifting relationships between anthropic and biophysical factors

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 25xa0years, 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.