Ecohydrology and Groundwater Management Group

AA, Netherlands

Ecohydrology and Groundwater Management Group

AA, Netherlands
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Grant
Agency: Narcis | Branch: Project | Program: Completed | Phase: Technology | Award Amount: | Year: 2000

This project aims at exploiting a unique property of heterogeneous land. Because of the heterogeneity in the architecture of vegetation canopies, the local balance of energy in the canopy space changes significantly. The combination of thermal heterogeneity and canopy architecture determines a significant angular change in emitted radiance. This directional signal provides, therefore, a unique link between radiative and aerodynamic properties of terrestrial vegetation canopies. || The goal of the investigation is to model the exchange of water and heat at heterogeneous land using a measure of thermal heterogeneity of the land, based on multi-angular measurements of emitted radiance obtained with space- and airborne sensors. || There has been significant progress on several aspects. We have developed algorithms to estimate aerosol optical depth and total amount of water vapour in the atmospheric column between the land surface and the space - borne instrument. We have demonstrated that the directional measurements of emittance from space (ATSR-s on board the European Remote Sensing Satellites ERS 1 and 2) at just two view angles can provide useful estimates of foliage and soil temperature. We have also shown that these estimates lead to improved modelling of heat exchange between terrestrial biosphere and the atmosphere. By modelling radiative and convective processes within vegetation canopies we have evaluated the sensitivity of foliage and soil temperature to the fraction of ground covered by foliage and to the amount of water present in the soil. Finally we have produced synthetic images of directional emittance for a real terrestrial landscape. These synthetic images have been used for the evaluation of our approach to estimate foliage and soil temperature. || From our efforts to evaluate the methods developed through the investigation we have identified two areas of application: a) modelling the exchange of energy and water between heterogeneous terrestrial vegetation and the atmosphere in relation with weather forecasts; b) evaluation of irrigation management by separating soil evaporation from foliage transpiration on the basis of the separate determination of foliage and soil temperature. || The research was carried out in close cooperation with a large European team working towards the development of the SPECTRA mission of the European Space Agency. Field measurements used in this research were collected as part of larger experiments carried out in China. All case studies described in the publications generated by this investigation have been performed as part of cooperative projects in USA and Europe. Solid cooperative relationships have been established with colleagues in France, China and Spain.


Cirkel D.G.,KWR Watercycle Research Institute | Cirkel D.G.,Ecohydrology and Groundwater Management Group | Witte J.-P.M.,KWR Watercycle Research Institute | Witte J.-P.M.,VU University Amsterdam | And 3 more authors.
Ecohydrology | Year: 2014

Soil acidity is well known to affect the species composition of natural vegetation. The physiological adaptations of plants to soil acidity and related toxicity effects and nutrient deficiencies are, however, complex, manifold and hard to measure. Therefore, generally applicable quantifications of mechanistic plant responses to soil acidity are still not available. An alternative is the semi-quantitative and integrated response variable 'indicator value for soil acidity' (Rm). Although relationships between measured soil pH and Rm from various studies are usually strong, they often show systematic bias and still contain high residual variances. On the basis of a well-documented national dataset consisting of 91 vegetation plots and a dataset with detailed, within-plot, pH measurements taken at three periods during the growing season, it is shown that strong spatiotemporal variation of soil pH can be a critical source of systematic errors and statistical noise. The larger part of variation, however, could be explained by the moisture status of plots. For instance, Spearman's rho decreased from 93% for dry plots and 87% for moist plots to 59% for wet plots. The loss of relation between soil pH and Rm in the moderately acid to alkaline range at increasingly wetter plots is probably due to the establishment of aerenchyma-containing species, which are able to control their rhizosphere acidity. Adaptation to one site factor (oxygen deficit) apparently may induce indifference for other environmental factors (Fe2+, soil pH). For predictions of vegetation response to soil acidity, it is thus important to take the wetness of plots into account. © 2012 John Wiley & Sons, Ltd.


Grant
Agency: Narcis | Branch: Project | Program: Completed | Phase: Agriculture | Award Amount: | Year: 2007

In this research, we consider flow and transport via different routes towards surface water. The central hypothesis is that surface runoff may form a significant factor in the local water balance (which involves evapotranspiration, surface runoff, shallow flow, leaching and groundwater flow), even for relatively flat areas. The significance is due to two aspects, i.e., the volume of water that is involved and, more important, the implications for soil and groundwater quality. For this reason, a coupled model is developed, that for the local scale (one field) combines all water fluxes in three dimensions. This model is used to conduct sensitivity analyses, where simulations span several seasons and years, to assess (1) the importance of surface runoff in the water balance quantitatively, (2) the importance of the different model parameters in specific conditions/circumstances.


Grant
Agency: Narcis | Branch: Project | Program: Completed | Phase: Agriculture | Award Amount: | Year: 2007

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