Catchment characteristics and soil and water chemistry of the San Francisco basin and subbasins, Ecuador

In this study, the Mean Transit Time and Mixing Model Analysis methods are combined to unravel the runoff generation process of the San Francisco River basin (73.5 km**2) situated on the Amazonian side of the Cordillera Real in the southernmost Andes of Ecuador. The montane basin is covered with cloud forest, sub-páramo, pasture and ferns. Nested sampling was applied for the collection of streamwater samples and discharge measurements in the main tributaries and outlet of the basin, and for the collection of soil and rock water samples. Weekly to biweekly water grab samples were taken at all stations in the period April 2007-November 2008. Hydrometric data, Mean Transit Time and Mixing Model Analysis allowed preliminary evaluation of the processes controlling the runoff in the San Francisco River basin. Results suggest that flow during dry conditions mainly consists of lateral flow through the C-horizon and cracks in the top weathered bedrock layer, and that all subcatchments have an important contribution of this deep water to runoff, no matter whether pristine or deforested. During normal to low precipitation intensities, when antecedent soil moisture conditions favour water infiltration, vertical flow paths to deeper soil horizons with subsequent lateral subsurface flow contribute most to streamflow. Under wet conditions in forested catchments, streamflow is controlled by near surface lateral flow through the organic horizon. Exceptionally, saturation excess overland flow occurs. By absence of the litter layer in pasture, streamflow under wet conditions originates from the A horizon, and overland flow.

Macroinvertebrate abundance in tropical Andean streams, Ecuador

Deforestation in the tropical Andes is affecting ecological conditions of streams, and determination of how much forest should be retained is a pressing task for conservation, restoration and management strategies. We calculated and analyzed eight benthic metrics (structural, compositional and water quality indices) and a physical-chemical composite index with gradients of vegetation cover to assess the effects of deforestation on macroinvertebrate communities and water quality of 23 streams in southern Ecuadorian Andes. Using a geographical information system (GIS), we quantified vegetation cover at three spatial scales: the entire catchment, the riparian buffer of 30 m width extending the entire stream length, and the local scale defined for a stream reach of 100 m in length and similar buffer width. Macroinvertebrate and water quality metrics had the strongest relationships with vegetation cover at catchment and riparian scales, while vegetation cover did not show any association with the macroinvertebrate metrics at local scale. At catchment scale, the water quality metrics indicate that ecological condition of Andean streams is good when vegetation cover is over 70%. Further, macroinvertebrate community assemblages were more diverse and related in catchments largely covered by native vegetation (>70%). Overall, our results suggest that retaining an important quantity of native vegetation cover within the catchments and a linkage between headwater and riparian forests help to maintain and improve stream biodiversity and water quality in Andean streams affected by deforestation. Also, this research proposes that a strong regulation focused to the management of riparian buffers can be successful when decision making is addressed to conservation/restoration of Andean catchments.

Macroinvertebrate abundance in montane tropical streams of varying land-use, 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.

(Figure 2) Mean discharge per day (total and baseflow part) of the San Francisco River and daily precipitation at station ECPL (Planta), in 2007

We investigated controls on the water chemistry of a South Ecuadorian cloud forest catchment which is partly pristine, and partly converted to extensive pasture. From April 2007 to May 2008 water samples were taken weekly to biweekly at nine different subcatchments, and were screened for differences in electric conductivity, pH, anion, as well as element composition. A principal component analysis was conducted to reduce dimensionality of the data set and define major factors explaining variation in the data. Three main factors were isolated by a subset of 10 elements (Ca2+, Ce, Gd, K+, Mg2+, Na+, Nd, Rb, Sr, Y), explaining around 90% of the data variation. Land-use was the major factor controlling and changing water chemistry of the subcatchments. A second factor was associated with the concentration of rare earth elements in water, presumably highlighting other anthropogenic influences such as gravel excavation or road construction. Around 12% of the variation was explained by the third component, which was defined by the occurrence of Rb and K and represents the influence of vegetation dynamics on element accumulation and wash-out. Comparison of base- and fast flow concentrations led to the assumption that a significant portion of soil water from around 30 cm depth contributes to storm flow, as revealed by increased rare earth element concentrations in fast flow samples. Our findings demonstrate the utility of multi-tracer principal component analysis to study tropical headwater streams, and emphasize the need for effective land management in cloud forest catchments.

Discharge measurements and storm event chemistry at the San Francisco River station (Planta) in 2007-2008

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 Niña 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 6-8 kg/ha/y for Ca, 7-8 kg/ha/y for K, 4-5 kg/ha/y for Mg, 11-14 kg/ha/y for Na, 19-22 kg/ha/y for NO3 (i.e. 4.3-5.0 kg/ha/y NO3-N) 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.

(Tables 1-3) Water chemistry of cloud forest streams at baseflow conditions, Rio San Francisco, Ecuador

We investigated controls on the water chemistry of a South Ecuadorian cloud forest catchment which is partly pristine, and partly converted to extensive pasture. From April 2007 to May 2008 water samples were taken weekly to biweekly at nine different subcatchments, and were screened for differences in electric conductivity, pH, anion, as well as element composition. A principal component analysis was conducted to reduce dimensionality of the data set and define major factors explaining variation in the data. Three main factors were isolated by a subset of 10 elements (Ca2+, Ce, Gd, K+, Mg2+, Na+, Nd, Rb, Sr, Y), explaining around 90% of the data variation. Land-use was the major factor controlling and changing water chemistry of the subcatchments. A second factor was associated with the concentration of rare earth elements in water, presumably highlighting other anthropogenic influences such as gravel excavation or road construction. Around 12% of the variation was explained by the third component, which was defined by the occurrence of Rb and K and represents the influence of vegetation dynamics on element accumulation and wash-out. Comparison of base- and fast flow concentrations led to the assumption that a significant portion of soil water from around 30 cm depth contributes to storm flow, as revealed by increased rare earth element concentrations in fast flow samples. Our findings demonstrate the utility of multi-tracer principal component analysis to study tropical headwater streams, and emphasize the need for effective land management in cloud forest catchments.

Palynology of sediment profiles from 30 lakes in Germany

Dieser Datensatz beinhaltet 70 Pollenprofile und begleitende sedimentologische Daten aus 30 Seen in Deutschland, die im Verlauf der 70er und 80er Jahre vom NlfB gekernt und analysiert wurden. Der Datenatz wurde im Rahmen des im folgenden beschriebenen Teilprojektes des DFG-Schwerpunktprogrammes "Wandel der Geo-Biosphäre" von Prof. Dr. Josef Merkt der wissenschaftlichen Gemeinschaft zur Verfügung gestellt. Im Projekt "Laminierte Seesedimente als Archive für Untersuchungen der Änderungen von Umweltbedingungen während Spätglazial und Holozän" wurden die laminierten Abschnitte von Sedimentprofilen aus oberschwäbischen, nordschweizerischen und norddeutschen Seen, die die letzten 15 000 Jahre umfassten, mikroskopisch ausgewertet. Ziel war es für Deutschland eine jahrgenaue Chronologie nach Kalenderjahren aufzustellen. Poster: Kleinmann, A, Merkt, J, Müller, H, Küster, H (1998) Holocene lake-level changes in Germany. Institute of Geobotany, University Hannover & Geological Survey of Lower Saxony, Hannover. (pdf hdl:10013/epic.31687.d001 280kB) Einführung: Die meisten Seen in Deutschland bestehen seit mehr als 15 000 Jahren und sind seit Jahrtausenden attraktiv für menschliche Besiedlung. In den Seeablagerungen ist die Geschichte der Umwelt nahezu ungestört und hoch aufgelöst konserviert. Pflanzliche und tierische Reste, wie z. B. Blütenstaub, Birkenfrüchte, Bucheckern, Algen, Wasserflöhe, Käfer, Muschelkrebse und Rädertierchen können Auskunft über die Entwicklung der Flora und Fauna, über Wärme- und Kälteperioden seit der letzten Eiszeit bis heute geben. Weitere Zeugen sind z.B. klastischer Eintrag (wie Sand), vulkanische Aschen, chemische Ausfällungen und eine jahreszeitliche Schichtung, die nur unter Sauerstoffausschluß entsteht. Ist der Seegrund belüftet, leben dort Tiere, die die oberen Zentimeter des Seebodens zur Nahrungssuche durchwühlen und dabei diese Schichtung zerstören. Ist der Seegrund ganzjährig unbelüftet, bleiben die klastischen Partikel, die organischen Reste, die chemischen Fällungen wie Siderit und Kalzit in der Reihenfolge liegen wie sie abgesunken sind. Die Reihenfolge spiegelt den Ablauf der Jahreszeiten wider: Goldalgen fallen im Frühjahr und die Mehrheit der Kieselalgen im Frühsommer und Sommer auf den Seeboden. Eisenkarbonat und Kalk werden im Sommer ausgeschieden, die klastischen und organischen Partikel sedimentieren im Winter. Die Jahresschichten liefern das zeitliche Gerüst in dem sich Klimaumschwünge, Seespiegeltiefstände und andere Ereignisse der Paläoumwelt jahrgenau fassen lassen. Auch die Landnutzung durch den Menschen ist aus Seeablagerungen abzulesen, wie z. B. erster Ackerbau, Rodungshochphasen in der Römerzeit und im Mittelalter, Aufforstung Anfang des 19. Jahrhunderts, bronzezeitliche und jüngere Erzverhüttungen, Industrialisierung, sogar Atombombentests und das Reaktorunglück von Tschernobyl 1986. Diese deuten das umwelt-wissenschaftliche Potential der Seesedimente an. Wesentliche Antworten, die in Seesedimenten stecken und entschlüsselt werden, sind die auf Fragen nach Klimaänderungen und ihren Folgen. Neben den bekannten vulkanischen Aschenlagen Laacher Tuff aus der Eifel, Saksunarvatn Tuff aus Island und Kilian/Vasset Tuff aus dem Massif Central werden weitere gesucht, da sie trennscharfe Leithorizonte sind und zur absoluten zeitlichen Korrelation von See zu See dienen. Daneben können regional unterschiedliche Vegetationsentwicklungen über isochrone Tephralagen einander zugeordnet werden. Mit der Erfassung möglichst vieler Sedimentparameter können Kriterien gefunden werden, mit denen die natürlichen von den anthropogenen Umweltveränderungen zu unterscheiden sind. Klimatisch unruhige Zeitabschnitte wie der Übergang Alleröd/Jüngere Tundrenzeit vor 12700 Kalenderjahren, der Übergang Spätglazial/Holozän vor 11560 Kalenderjahren und die 120 Jahre später einsetzende vorübergehende Abkühlung, die Rammelbeekphase, wurden analysiert, um Dauer, Verlauf und Folgeerscheinungen kennenzulernen. Als Methoden wurden eingesetzt: Mikrofaziesanalyse mit Dünnschliffen, Pollenanalyse, Mikrofaunauntersuchungen, anorganisch und organisch geochemische Analysen, Isotopenanalyse (delta13C, delta18O, AMS an terrestrischen Makroresten).

Distribution of gammaridean Amphipoda (Crustacea) in the Iberian deep sea basin (Table 2)

Four species of gammaridean Amphipoda are recorded from the Iberian deep sea basin at about 5000 m depth: Bathyceradocus iberiensis sp. n., Paracallisoma platepistomum sp. n., Parandaniexis cf. mirabilis Schellenberg, 1929, and Paragissa galatheae Barnard, 1961. The biology of the four species is discussed.