Physical and Regional Geography Research Group

Leuven, Belgium

Physical and Regional Geography Research Group

Leuven, Belgium
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Ashebir D.,Mekelle University | Ashebir D.,University of Natural Resources and Life Sciences, Vienna | Deckers T.,PCFruit Vzw Proefcentrum Fruitteelt | Nyssen J.,Ghent University | And 9 more authors.
Experimental Agriculture | Year: 2010

Lack of effective chilling during the dormant season is one of the major problems when apples are growing under a tropical climate. We evaluated the response of different apple cultivars (Golden Delicious, Gala, Fuji, Granny Smith and Jonagold) grown on M9 rootstock with different dormancy-management practices. The trials were carried out between 2004 and 2006 in a tropical mountain area (Tigray, Ethiopia), where chilling conditions are poor with the aim of improving and synchronizing the bud break and the blossoming period of these apple cultivars. Two-year-old well-feathered trees were planted in two experimental trial sites in a randomized complete block design. Trees were subjected to the following treatments in two sets of experiments: one defoliation per year only; two defoliations per year, one defoliation followed by 1% hydrogen cyanamide (Dormex) treatment; one defoliation followed by 2% Dormex treatment; one defoliation followed by 4% winter oil; one defoliation followed by 0.5% Dormex and 2% winter oil; and a control with no defoliation or dormancy breaking treatments. The results show positive effects of the dormancy breaking agents on the productivity of the trees after defoliation, with comparable results for the effectiveness of both Dormex and winter oil. There were no statistically significant differences between the Dormex doses. The defoliation treatment alone was not sufficient to break dormancy for the cultivars Golden Delicious, Granny Smith or Gala but showed promising results with dormancy breaking on Jonagold. Yields increased as a result of better flowering time synchronization within a tree but even with the dormancy treatments the length of the flowering period was still spread over five weeks, where under a more temperate climate it lasted two to three weeks. The average fruit weight of Jonagold and Granny Smith can be considered as a good fruit quality while the fruit of other diploid cultivars like Golden, Gala and Fuji were rather small, which indicates that fruit thinning by hand will be a necessity for these cultivars. Red colouration of the apples on the cultivars Gala and Jonagold was excellent and meets the standards necessary for commercialization of these fruits. The sugar concentration of the fruits and the fruit firmness at harvest was high. The results of these first trials indicate that it is possible to develop new apple production in the mountain region of Tigray, Ethiopia. Copyright © Cambridge University Press 2009.

Den Eeckhaut M.V.,Physical and Regional Geography Research Group | Den Eeckhaut M.V.,Research Foundation Flanders | Marre A.,University of Reims Champagne Ardenne | Poesen J.,Physical and Regional Geography Research Group
Geomorphology | Year: 2010

The vineyards of the Montagne de Reims are mostly planted on steep south-oriented cuesta fronts receiving a maximum of sun radiation. Due to the location of the vineyards on steep hillslopes, the viticultural activity is threatened by slope failures. This study attempts to better understand the spatial patterns of landslide susceptibility in the Champagne-Ardenne region by comparing a heuristic (qualitative) and a statistical (quantitative) model in a 1120 km2 study area. The heuristic landslide susceptibility model was adopted from the Bureau de Recherches Géologiques et Minières, the GEGEAA - Reims University and the Comité Interprofessionnel du Vin de Champagne. In this model, expert knowledge of the region was used to assign weights to all slope classes and lithologies present in the area, but the final susceptibility map was never evaluated with the location of mapped landslides. For the statistical landslide susceptibility assessment, logistic regression was applied to a dataset of 291 'old' (Holocene) landslides. The robustness of the logistic regression model was evaluated and ROC curves were used for model calibration and validation. With regard to the variables assumed to be important environmental factors controlling landslides, the two models are in agreement. They both indicate that present and future landslides are mainly controlled by slope gradient and lithology. However, the comparison of the two landslide susceptibility maps through (1) an evaluation with the location of mapped 'old' landslides and through (2) a temporal validation with spatial data of 'recent' (1960-1999; n = 48) and 'very recent' (2000-2008; n = 46) landslides showed a better prediction capacity for the statistical model produced in this study compared to the heuristic model. In total, the statistically-derived landslide susceptibility map succeeded in correctly classifying 81.0% of the 'old' and 91.6% of the 'recent' and 'very recent' landslides. On the susceptibility map derived from the heuristic model, on the other hand, only 54.6% of the 'old' and 64.0% of the 'recent' and 'very recent' landslides were correctly classified as unstable. Hence, the landslide susceptibility map obtained from logistic regression is a better tool for regional landslide susceptibility analysis in the study area of the Montagne de Reims. The accurate classification of zones with very high and high susceptibility allows delineating zones where viticulturists should be informed and where implementation of precaution measures is needed to secure slope stability. © 2009 Elsevier B.V. All rights reserved.

Nadal-Romero E.,CSIC - Pyrenean Institute of Ecology | Nadal-Romero E.,Physical and Regional Geography Research Group | Regues D.,CSIC - Pyrenean Institute of Ecology | Serrano-Muela P.,CSIC - Pyrenean Institute of Ecology
Pirineos | Year: 2010

The Inner Depression (Central Pyrenees) presents a great heterogeneity of land uses and vegetation covers. In this context, a hundred of badlands areas are distributed along the ranges of the Depression. This morphologies occurrence has been associated to the combination of different factors: bedrock, climate, deforestation, slope terracing and field crop abandonment. In this way, most of the hydrological basins show a mosaic of contrasted environments: badlands, meadows, meadows with shrubs and reforested slopes. This study presents the analyses of the hydrological response on the Araguás catchment, which is monitored for recording discharges from the most extreme environments: badlands and reforested slopes. The results show great differences on discharge generation, both by runoff generation processes and by its frequency and water volume. Reforested environments decreases flooding and erosion risks, but also generate a big reduction of water resources disposability.

Lasanta T.,CSIC - Pyrenean Institute of Ecology | Nadal-Romero E.,CSIC - Pyrenean Institute of Ecology | Nadal-Romero E.,Physical and Regional Geography Research Group | Serrano-Muela P.,CSIC - Pyrenean Institute of Ecology | And 2 more authors.
Pirineos | Year: 2010

The main landscape feature in the Pyrenean middle mountain is the presence of hillslopes occupies by old cultivated fields already abandoned, affected by different stages of plant colonization. By means of experimental plots, this paper studies runoff generation and sediment yield in two types of abandoned fields: (i) sloping fields previously cultivated with cereal and frequently fertilized; and (ii) fields corresponding to shifting agriculture, with scarce conservation measures. The results obtained were compared to a dense shrub cover plot. The abandoned plots yield much more water and sediment than the dense shrub cover, which shows a lower variability in the hydromorphological response. The progressive plant colonization of the two abandoned plots favoured the occurrence of a negative trend in runoff and erosion. This paper also demonstrated that the shifting agriculture fields yield more water and erosion than sloping fields, because of difficulties for plant succession.

Serrano-Muela P.,CSIC - Pyrenean Institute of Ecology | Regues D.,CSIC - Pyrenean Institute of Ecology | Nadal-Romero E.,CSIC - Pyrenean Institute of Ecology | Nadal-Romero E.,Physical and Regional Geography Research Group
Pirineos | Year: 2010

This paper analyses the stormflow response of the San Salvador forested catchment (0.92 km2) located in the Central Pyrenees, Spain. Using stormflow coefficient and discharge increment, the temporal variability of the rainfallrunoff relationship is analyzed at the event scale from hydrographs observed over a 7-year period. Results show that the storm-flow coefficient has a clear seasonal pattern with an alternance between a wet period, when the catchment is hydrologically responsive, and a dry summer period, when the catchment presents almost no reaction to any rainfall. The relationships of the storm-flow coefficient and discharge increment with several hydrological variables shows similar (but lower) correlations than usually observed in other Mediterranean or temperate catchments and demonstrates that the storm flow response is mainly depending on water table with rainfall depth and base flow as secondary factors. The marked seasonality observed in the San Salvador catchment is most likely accentuated by forest that cover all the catchment, but this deserves further investigations.

Lana-Renault N.,CSIC - Pyrenean Institute of Ecology | Lana-Renault N.,University Utrecht | Regues D.,CSIC - Pyrenean Institute of Ecology | Nadal-Romero E.,CSIC - Pyrenean Institute of Ecology | And 3 more authors.
Pirineos | Year: 2010

A small catchment affected by agricultural practices in the past, then progressively abandoned and naturally re-vegetated was monitored in the central Spanish Pyrenees. The results obtained over a 9-year period revealed the complexity of its hydrological and geomorphological behaviour. Several runoff generation processes can occur at the same time and in different parts of the catchment, depending on the water reserves conditions and rainfall characteristics. Sediment response is mainly controlled by the spatial and temporal dynamics of water and sediment contributing areas within the catchment. The sediment output illustrates the complexity of the geomorphic response of mountain environments modified by past farmland activities.

Nadal-Romero E.,CSIC - Pyrenean Institute of Ecology | Nadal-Romero E.,Physical and Regional Geography Research Group | Regues D.,CSIC - Pyrenean Institute of Ecology
Progress in Physical Geography | Year: 2010

This study investigates the geomorphological dynamics of badland areas in the Araguás catchment (0.45 km2) in the Central Pyrenees. The genesis and development of badlands in the Central Pyrenees is favoured by the presence of Eocene marls and a markedly seasonal climate. The Araguás catchment has been monitored since 2004. Analysis of weathering processes and regolith dynamics showed that alternating freeze-thaw and wetting-drying cycles are the main causes of regolith development and weathering, and effectiveness and intensity of these processes is maximum in winter and summer. Evolution of the badland surfaces is related to regolith moisture level and temperature, closely associated with the season and slope exposure, which cause cyclical variations in regolith physical conditions. The most important effect associated with regolith dynamics is the temporal delay between maximum rainfall erosivity and variation in maximum surface runoff generation, reflected in seasonal differences in sediment transport. The dynamics of weathering and erosion processes affecting badland areas are the principal factors controlling geomorphological development, and the extreme hydrological and sedimentological responses of badlands are the main effects of such morphologies. From a hydrological point of view, badlands increase water production, and flood frequency relative to neighbouring areas; from a sedimentological point of view, suspended sediment transport from badland areas can reach amounts two or three orders of magnitude higher than other nearby environments. Given these results, possible responses of badland dynamics to altered hydroclimatic regime are briefly discussed. © The Author(s) 2010.

Serrano-Muela M.P.,CSIC - Pyrenean Institute of Ecology | Regues D.,CSIC - Pyrenean Institute of Ecology | Estela Nadal-Romero E.,Physical and Regional Geography Research Group
Cuaternario y Geomorfologia | Year: 2012

Throughfall and stemflow have been studied in a forest-covered catchment in the Central Spanish Pyrenees. The San Salvador catchment (0,92 km2) is located in the Aísa Valley, in which trends in plant cover evolution show an increase of the presence of open and dense forests, after the abandonment of agricultural activities since the middle of the 20th Century. San Salvador catchment shows a dense forest in all area (more than 90%). Pinus sylvestris, Fagus sylvatica and Quercus gr. faginea, forest patches alternate in the catchment according to altitude and shape of the slopes (concave, convex). Three open plots have been selected in the San Salvador catchment, corresponding to the three types of forest cover. The results (April 2006-April 2008) has demonstrated that the percentages of throughfall are associated with type of forest cover, due to differences in the morphology of the leaves and the foliage density. Thus, the species that causes a major interception is Fagus sylvatica, while Quercus gr. faginea and Pinus sylvestris has shown a similar enough seasonal behaviour, the last one more homogenous due to the invariable coverage.

van Dessela W.,Physical and Regional Geography Research Group | van Rompaeya A.,Physical and Regional Geography Research Group | Szilassib P.,University of Szeged
International Journal of Geographical Information Science | Year: 2011

The recent availability of regional-scale land use and land cover data made it possible to apply land use and land cover models at regional-, national-and even continental-scale levels. A commonly used modelling approach is based on the assessment of land cover probabilities by means of logistic regression equations. In most cases, however, the error involved in the parameterization of logistic regression equations is not known. In this article, the sensitivity of logistic regression parameterization for land use and land cover probability assessments is analysed by comparing the results using input maps from different sources. Land cover maps with a range of accuracy levels were collected for a sub-catchment of the Lake Balaton watershed in Hungary. The results show that the parameterization of the logistic regression coefficients is highly dependent on the quality of the input maps. Both the spatial pattern and the area covered by a specific land cover type have a direct influence on the error propagation in the land cover probability maps. These findings should be taken into account when interpreting the results of land use and land cover change models at regional- and national-scale levels. © 2011 Taylor & Francis.

Lana-Renault N.,University Utrecht | Nadal-Romero E.,IPE | Nadal-Romero E.,Physical and Regional Geography Research Group | Serrano-Muela P.,IPE | And 4 more authors.
IAHS-AISH Publication | Year: 2010

Three small basins with differing histories of land use in the central Pyrenees were studied to investigate and quantify their hydrological and sediment responses. The highly degraded Araguás basin reacted to most rainfall events, and discharge was mainly related to rainfall characteristics. The hydrological behaviour in the abandoned Arnás basin was more complex, with discharge being strongly related to water reserves and rainfall characteristics. In the forested San Salvador basin, spring was almost the only high flow period, and discharge was always related to preceding rainfall and to pre-event basin wetness. The hydrological behaviour of the three basins partially influenced their sediment responses. The sediment yield in the degraded basin was dominated by suspended sediment, and it was two orders of magnitude greater than estimated for vegetated basins. In the abandoned basin, suspended sediment was important but solutes dominated. In the forested basin, solutes largely dominated over suspended sediment. The results illustrate how land cover influences a basin's hydrological dynamics and sediment response. The data for the three basins will be useful for calibrating and validating hydrological and sedimentological models, and to predict streamflow and sediment transport responses under different land cover scenarios. Copyright © 2010 IAHS Press.

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