Thierry Brossard

A Quantitative Approach to the Visual Evaluation of Landscape

A method for describing landscape in the countryside and evaluating its impact on the real-estate market is suggested. Four databases with different resolutions (7, 30, 150, and 1,000 m) are used to simulate the visual properties of landscape in the depth of the field of view. The databases, comprising digital elevation models and land use images, are processed by a raster geographical information system. A model that simulates the relationship of visibility among all the points in a given space is devised and used to produce variables that are taken as explanatory variables in a hedonic regression. On this basis, the significant contribution of several landscape features to housing prices is estimated and then mapped. The study area is located in the urban fringe of Dijon (France). A total of 4,352 houses with known price, position, and landscape amenities provide the information for calibrating the hedonic model. The results confirm that landscape amenities influence house prices. Landscapes and visible features more than 100 to 200 m away all have insignificant hedonic prices. In this study area, forests and farmland in the immediate vicinity of houses have positive prices, whereas roads have negative ones.

Mapping and analysing arctic vegetation : evaluating a method coupling numerical classification of vegetation data with SPOT satellite data in a probability model

Vegetation and environmental data were collected at 266 sampling points distributed in a regular manner along transects covering the Broggerhalvoya peninsula, on the north-western coast of Spitsbergen. Transects with sampling points were drawn in advance on aerial photographs. The analysis of releves and collection of ground data along transects represent an efficient, representative and precise way of sampling. The vegetation data were classified and 19 plant communities distinguished. The plant communities were subjected to detrended correspondence analysis (DCA). Among the recorded variables, moisture is the one with the highest correlation along axes one and two, and reflects a coincidental moisture and vegetation cover gradient. The vegetation component responsible for this positive correlation is the bryophytes. Likewise, the TWINSPAN classification confirms this gradient in a dendrogram reflecting the hierarchical structure of the plant communities. Plant communities constitute the base of a statis...

Modelling index of thermophily by means of a multi-source database on Broggerhalvoya Peninsula (Svalbard)

In the Arctic, plant species are at their physiological tolerance limit. Anthropogenic induced climate changes may thus have fundamental consequences on arctic plant life in the near future. Summer temperatures are by far the most important factor determining the general distribution of plants over large areas. According to different meteorological stations, mean July temperature on Svalbard is in the range 2-6°C. Nevertheless, there are large local gradients in the Svalbard landscape. A method has been developed that uses the plants as climate indicators. This index of thermophily uses the whole species diversity, with increasing values based on increasing concentrations of plants requiring higher temperatures within the temperature range cited from Svalbard above. This index can be useful for predicting scenarios about development of arctic vegetation due to the global change effects if we can determine the environmental factors controlling its spatial variation. The function of these environmental variables is analysed according to a regional and a local scale. At each scale, modelling index of thermophily values distribution is done within a GIS, using different variables as predictors. At the regional scale, covering the Brøggerhalvøya peninsula, spatial distribution of index values is correlated with latitude and longitude and shows a continentality effect. At the local scale, other predictors like topography (gradient, aspect, altitude) and satellite data (NDVI, temperature from TM6, classification results) are tested. Finally, a combination of the models for the different scales enables us to map the distribution of index of thermophily.

Recent spatial development of Svalbard strandflat vegetation over a period of 31 years

Vegetation succession was analysed at the forefields of two glaciers in Svalbard over an interval of 31 years (1975–2006). In 1975, 85 sampling sites were positioned along transects extending from the coastline to the glacier fronts: botanical observations were made at each sampling site. This protocol allowed us to carry out new observations in 2006 under the same conditions. Thus, it was possible to undertake a botanical assessment of species and taxa, and to see how the vegetation has changed with reference to a typology established by coupling correspondence analysis and ascending hierarchical classification. Vegetation succession at the sampling sites was also measured by using vectors positioned in the multidimensional space of correspondence analysis. In this way, the changes over the interval between seven vegetation types were plotted and mapped, and the colonization process was calibrated and dated against a series of reference stages, mainly since the end of the Little Ice Age.

Interindividual Differences in a Set of Biological Rhythms Documented During the High Arctic Summer (79°N) In Three Healthy Subjects

The High Arctic summer with its permanent sunlight provides a situation in which one of the natural synchronizers, the light-dark alternation, is minimal. During the summers of 1981 and 1982 three healthy right-handed geographers who were performing field studies in Svalbard as part of their own research volunteered to document, 4-6 times per 24 hr for respectively 63, 141 and 147 days, a set of circadian rhythms: self-rated fatigue, oral temperature, grip strength of both hands, heart rate and times of awakening and retiring. Tests were performed before departure from France, in Svalbard (79 degrees N latitude) where their daily activities were often strenuous, and after returning to France. Time series were treated individually according to three methods: display of data as a function of time, cosinor analyses to quantify rhythm parameters, and spectral analyses to estimate component periods of rhythms. Circadian parameters such as period and acrophase of activity-rest, oral temperature and fatigue rhythms were not altered. On the other hand, the circadian rhythm in grip strength was altered: the period differed from 24 hr in one subject, while grip strength acrophase of the left, but not the right, hand of the other two subjects was phase shifted during the sojourn in Svalbard. A prominent circahemidian (about 12 hr) rhythm was observed in two subjects for their heart rate in Svalbard, while a prominent circadian rhythm (differing from exactly 24 hr) was observed in France associated with a small circahemidian component.