Amelie Bücker

Solute behaviour and export rates in neotropical montane catchments under different land-uses

To improve our knowledge of the influence of land-use on solute behaviour and export rates in neotropical montane catchments we investigated total organic carbon (TOC), Ca, Mg, Na, K, NO3 and SO4 concentrations during April 2007-May 2008 at different flow conditions and over time in six forested and pasture-dominated headwaters (0.7-76 km²) in Ecuador. NO3 and SO4 concentrations decreased during the study period, with a continual decrease in NO3 and an abrupt decrease in February 2008 for SO4. We attribute this to changing weather regimes connected to a weakening La Nina event. Stream Na concentration decreased in all catchments, and Mg and Ca concentration decreased in all but the forested catchments during storm flow. Under all land-uses TOC increased at high flows. The differences in solute behaviour during storm flow might be attributed to largely shallow subsurface and surface flow paths in pasture streams on the one hand, and a predominant origin of storm flow from the organic layer in the forested streams on the other hand. Nutrient export rates in the forested streams were comparable to the values found in literature for tropical streams. They amounted to 68 kg/ha*y for Ca, 78 kg/ha*y for K, 45 kg/ha*y for Mg, 11-14 kg/ha*y for Na, 19-22 kg/ha*y for NO3 and 17 kg/ha*y for SO4. Our data contradict the assumption that nutrient export increases with the loss of forest cover. For NO3 we observed a positive correlation of export value and percentage forest cover.

The influence of land-use on macroinvertebrate communities in montane tropical streams - a case study from Ecuador.

Despite the importance of tropical montane cloud forest streams, studies investigating aquatic communities in these regions are rare and knowledge on the driving factors of community structure is missing. The objectives of this study therefore were to understand how land-use influences habitat structure and macroinvertebrate communities in cloud forest streams of southern Ecuador. We evaluated these relationships in headwater streams with variable land cover, using multivariate statistics to identify relationships between key habitat variables and assemblage structure, and to resolve differences in composition among sites. Results show that shading intensity, substrate type and pH were the environmental parameters most closely related to variation in community composition observed among sites. In addition, macroinvertebrate density and partly diversity was lower in forested sites, possibly because the pH in forested streams lowered to almost 5 during spates. Standard bioindicator metrics were unable to detect the changes in assemblage structure between disturbed and forested streams. In general, our results indicate that tropical montane headwater streams are complex and heterogeneous ecosystems with low invertebrate densities. We also found that some amount of disturbance, i.e. patchy deforestation, can lead at least initially to an increase in macroinvertebrate taxa richness of these streams.

Wassernutzung und Wassereffizienz in Landschaften

Wasser ist ein naturlicher Bestandteil unseres Lebens. Wir trinken es, waschen und kochen damit, wassern unsere Pflanzen und nutzen es auch sonst auf vielfaltige Weise als Roh- und Werkstoff. In Deutschland sind rund 99 Prozent der Bevolkerung an das Trinkwassernetz angeschlossen (UBA 2010a), sodass die jederzeitige und ausreichende Verfugbarkeit von Wasser selbstverstandlich geworden ist. Auserhalb der Stadte jedoch, an den land- und forstwirtschaftlichen Standorten und den Naturschutzflachen, zeigt sich ein anderes Bild. Hier entscheidet die naturliche Verfugbarkeit von Wasser unter anderem uber Ernteertrage, das Futterangebot fur Weidetiere, uber die Grundwassererneuerung und uber den Zustand der okosysteme. Kommt es zum Ungleichgewicht durch nicht nachhaltige Nutzung, Flachenversiegelung oder aufgrund unausgewogener Niederschlage, kann dies regional nachdruckliche und unerwunschte Folgen haben. Mehr als 80 Prozent der Flache Deutschlands sind landwirtschaftliche Flachen oder Wald (Destatis 2011).