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--- en:talks:kiel-nov.2008 [2016/07/09 21:11] – external edit 127.0.0.1
+++ en:talks:kiel-nov.2008 [2024/04/10 10:03] (current) – external edit 127.0.0.1
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 === Example 1 - the riddle of transpiration and runoff ===
-->Betts et al. (2007) claim that an increase of runoff at a global scale can be related to an increase in CO<sub>2</sub> concentration. This conclusion is based on empirical data and series of  plot-scale experiments providing evidence of an effect of carbon-dioxide on transpiration. Hence, plot scale-data were used to explain a phenomenon that was observed on a global scale. Can this approach be justified? The attempt to reproduce this effect at the catchment scale and for the island of Cyprus with a model including plant growth, carbon dioxide effects on transpiration and nutrient constraints (SWAT2005) did not produce an effect of CO<sub>2</sub> on mean annual runoff. While, indeed, transpiration at the plot scale decreased for single plants, the overall effect on the catchment scale was canceled out by an increase in biomass resulting in higher LAI, compensating the decrease of transpiration from single plants. There are ([[EvaporationFeedback | more processes]]).
+->Betts et al. (2007) claim that an increase of runoff at a global scale can be related to an increase in CO<sub>2</sub> concentration. This conclusion is based on empirical data and series of  plot-scale experiments providing evidence of an effect of carbon-dioxide on transpiration. Hence, plot scale-data were used to explain a phenomenon that was observed on a global scale. Can this approach be justified? The attempt to reproduce this effect at the catchment scale and for the island of Cyprus with a model including plant growth, carbon dioxide effects on transpiration and nutrient constraints (SWAT2005) did not produce an effect of CO<sub>2</sub> on mean annual runoff. While, indeed, transpiration at the plot scale decreased for single plants, the overall effect on the catchment scale was canceled out by an increase in biomass resulting in higher LAI, compensating the decrease of transpiration from single plants.
 Hydrological and hydrogeological systems are networks that concentrate and funnel fluids to outlets. Plants adapt to the availability of water: Hence, plant communities concentrate along channels, flow paths, depressions and discharge areas and consume water that was recharged upstream. As a result net recharge decreases with increasing catchment size by secondary evaporation. These feedbacks also complicate basin response to climate changes. Higher rainfall and higher recharge can result in an expansion of discharge zones and in an adaptation and increase of vegetation density therein.