Environmental changes in biodiversity hotspot ecosystems of
South Ecuador: RESPonse and feedback effECTs (FOR2730)

Abstract:

Trees in tropical dry forests (TDFs) have manifold drought coping strategies including succulence of different plant organs, wood anatomical traits and leaf phenology. As water availability to plants is the limiting factor for physiological activity, changes in precipitation patterns are assumed to have strong influences on tree phenology, growth and water turnover. Our objectives were to assess patterns in leaf phenology, radial stem circumference changes and sap flux responses to fluctuating moisture regimes of selected species. Based on these findings we evaluated the potential suitability as indicator species for climate change effects. The study was implemented at different elevational positions in a submontane dry forest of southern Ecuador. Annual rainfall is 600 mm with an eight months dry period; moisture availability slightly increases with altitude because of moist air coming from the Pacific. At three altitudes,we studied the tree species Ceiba trichistandra (leaf deciduous, stem succulent), Eriotheca ruizii (leaf deciduous, root succulent) and Erythrina velutina (leaf deciduous). Reversible stem swelling and shrinking was observed for all three species during the whole study period and at all positions at the altitudinal gradient. However, it was most pronounced and sensitive in the stem succulent C. trichistandra and at the lowest (driest) position. C. trichistandra flushed leaves at dry season intermittent rain events, and from dry to wet season leaf out was earlier, and in this period sap flux was high while stem circumference decreased. Length of the leaved periods of all species increased with altitude. Thus, clear differences among species, topographic positions, radial growth and tree water use patterns are revealed; especially C. trichistandra responded very sensitive to fluctuating moisture regimes with leaf phenology, sap flux and stem diameter variations, and can be regarded as a sensitive indicator for assessing climatic variations.

Abstract:

This report examines the impact of climate changes and variations in land use based on water samples taken from the alpine grassland ecosystem Páramo in the South of Ecuador. For this purpose, two monitoring points were identified, which hold a different level of anthropogenic influences. Predominantly, the Virgin area exists of natural Páramo. In contrast, the area of Chirimachay is by far more versatile since its components are natural Páramo, nature forest, livestock as well as trout farming. In order to analyse the climate in a diurnal and seasonal cycle, date of temperature and precip-itation has been evaluated. For the purpose of this report, fluxes of nitrogen-nitrate (N-NO3), chemical and biochemical oxygen demand (COD / BOD) and turbidity were analysed. In order to examine the fluxes, concentrations of the mentioned parameters were measured in a five minutes routine in the first step. Afterwards, they were multiplied with current discharge data. Analysis of the data does not illustrate a correlation between nutrient fluxes and air temperature. In terms of precipitation, however, it was possible to identify a relation to COB and BOD (given R=0,829 each in Chirimachay area) by using a linear correlation matrix. Additionally, in the Chirimachay area, evidence for a relation between precipitation and turbidity was found. Even though there is no linear correlation between N-NO3 and precipitation, it is still possible that there is another relation based on the characteristics of moving in soil during different environ-mental conditions. Furthermore, land use has different effects on each parameter. By using scatter plots and statis-tical tests it was possible to analyse the extent of differences in fluxes due to the specific land use. Therefore, N-NO3 fluxes are not influenced while COD, BOD, and on a minor scale, tur-bidity, are correlating to each other.

Abstract:

Chemical element concentrations and fluxes in the hydrological cycle of a mountain rain forest in southern Ecuador are influenced by annual seasonality, long term trends, inter-annual ENSO cycles and other environmental factors. Some knowledge about this processes was collected in previous studies. But little is known about how much of the variation in the data can be explained by those processes. Goal of this thesis is therefore to build linear models that explain the variation in element concentrations and fluxes in the incident precipitation and in the troughfall of an small forested catchment in southern Ecuador. The linear models contain seasonal terms, trend terms, ENSO temerature anomalie terms and environmental variable terms. For each analysed element four linear model were build to explain variation in concentrations and fluxes in incident precipitation and troughfall. The models contained all terms at the beginning and were then optimized to a model with only the significant terms for each element in each flux and concentration. By analysing a time series from 1998 to 2010 with monthly means of element concentrations of weekly measurements of troughfall and incident precipitation, and their resulting fluxes, the following hypothesis are tested. Namely seasonal terms are significantly explaining the variation in the concentrations and fluxes, longterm trends are explaining the variation, ENSO related temperature anomalies are explaining the variation and other environmental factors are explaining the variation. The findings showed that in 45 % of the models seasonality is significantly contributing to the explaining of the variation. A significant trend terms is part of 30% of the models and a significant ENSO term in 18%. The range of percentage of significant environmental variables starts with 16% for wind direction and 18% for flower or fruiting phenology. goes to 25 % and 31 % for fire activity and heavy rain activity respectively and finally goes to 57% for conductivity. To mention is that in this case conductivity is present in 90% of the conductivity models. The resulting R squares showed that the best models are the troughfall models. The best model here explains almost 80% of the variation, the median is around 50% of explained variation and the worst model explains 27 % of the variation. In the incident precipitation concentration and in the troughfall and incident precipitation fluxes the best models are between 30 and 40 % of explained variation, the median is about 20% for incident precipitation and between 10 and 15 % for the fluxes and the lowest values are about 5 %. The model quality test shows that the not crucial criteria of normal distribution ot the model residuals is violated in some models. The crucial temporal independence criteria is most likely violated in few models and in one model it is clearly violated. All in all the thesis could show that seasonality, trend, ENSO related temperature anomalies and the environmental variables fire activity, conductivity, wind direction, heavy rain, and flower and fruiting phenology are in various combinations contributing significantly to the explaining of the variation in concentration and fluxes of incident precipitation and troughfall. The models are strong in explaining the variation in cases like potassium troughfall concentration, where rainfall seasonality leads to big concentration variation, while in other cases, like magnesium incident precipitation concentrations, where little variation occurs and factors that are not included as model terms lead to clear patterns in the concentrations, the model can explain almost no variation.

Abstract:

Um das Vorhandensein und den Transport chemischer Elemente auf der Erde zu beschreiben, wird das Konzept der biogeochemischen Kreisläufe angewandt. Ein solches Element ist Phosphor, das wegen seiner Wichtigkeit als limitierendes oder co-limiterendes Element für das Pflanzenwachstum in tropischen Regenwäldern ausgewählt wurde. Am Beispiel eines Einzugsgebietes im tropischen Bergregenwald von Ecuador wird untersucht, wie sich die Phosphorkonzentrationen und Phosphorflüsse entlang des wassergebundenen Kresilaufs vom Freilandniederschlag bis hin zum Oberflächenabfluss sowohl zeitlich wie auch räumlich verhalten. Die untersuchten Daten umfassen die Wasserflüsse und die Konzentrationen von Orthophosphat und totalem gelösten Phosphat zwischen 1998 und 2010 als monatliche Mittel. Die räumliche Verteilung wird mit der Darstellung der Messwerte in Boxplots und der Suche nach räumlichen Mustern analysiert. Um nach saisonalen Prozessen zu suchen, wird einerseits ein lineares Modell, bestehend aus einer Sinus- und einer Cosinus-Funktion gebildet und auf Signfikanz und Aussagekraft, d.h. Erklärung der Variabilität durch das Modell anhang des Anteils an der Gesamtvariation getestet. Anderseits wird die Autokorrelation der Daten auf ein saisonales Muster untersucht. Ein allfälliger langfristiger Trend wird mit dem saisonalen Kendall-Test gesucht. Bei der Analyse der räumlichen Verteilung zeigt sich, dass sich die größten Phosphor-Konzentrationen und -Flüsse zwischen Bestandesniederschlag und organischer Auflage bewegen. Zudem ist der Eintrag durch den Freilandniederschlag größer als der Austrag im Oberflächenabfluss. Bei allen Wasserflüssen wurde eine jährliche Saisonalität festgestellt. Bei den Konzentrationen ist ein antizyklisches Verhalten zu den Wasserflüssen zu erkennen. Der Freilandniederschlag weist keine Saisonalität auf. Die größten Saisonalitäten sind zwischen Krone und organischer Auflage zu finden. Die Konzentrationen in den Saugkerzen und im Oberflächenabfluss sind nur schwach durch saisonale Prozesse geprägt. Bei den Flüssen zeigt nur der Bestandesniederschlag deutlich jährliche Saisonalität. Die Analyse der zeitlichen Trends zeigte keine langfristigen Trends, die auf eine Änderung externer Faktoren zurückzuführen sind. Interne Veränderungen im Pflanzenwachstum könnten für eine Zunahme im Stammabfluss und eine Abnahme der Lysimeterkonzentrationen (unter der organischen Auflage) verantwortlich sein. Bei der Analyse der Feueraktivität als möglicher Quelle für Phosphoreintrag wurden einzelne signifikante Beziehungen mit den Phosphorkonzentrationen gefunden.