Land cover and climate interactions of Andean páramo ecosystems – disentangling the hydro-biogeochemical response of a mountainous headwater catchment in Southern Ecuador

Monday, 6 June 2016
David Windhorst1, Sarah Schob1, Giovanny Mosquera1,2, Patricio Crespo2 and Lutz Breuer1, (1)Justus Liebig University Giessen, Institute for Landscape Ecology and Resources Management, Giessen, Germany, (2)Universidad de Cuenca, Departamento de Recursos Hídricos y Ciencias Ambientales & Facultad de Ciencias Agropecuarias, Cuenca, Ecuador
Abstract:
The páramo plays a crucial role in flow regulation, water supply and carbon storage. Climate (i.e. longer dry periods, higher temperatures) and land use change will affect the ecosystem´s water regulation capacity. Nevertheless, it remains unclear how this fragile ecosystem will react to those global changes.

To gain insights into temporal hydrological and biogeochemical functioning, we studied discharge and fluxes of BOD, COD, turbidity and nitrate in a headwater catchment (91 km²) in the páramo of south Ecuador. Measurements were conducted continuously (5 min) using in-situ UV-Vis spectrometers at two sites. The first one upstream in an area mostly covered with pristine páramo and the second one further downstream, which is increasingly influenced by anthropogenic land use.

Wavelet analysis was used to examine the continuous time series for local patterns and transient features of the hydrological and biogeochemical cycles. Wavelet coherencies between stream water chemistry and hydrological (discharge) as well as local climate (temperature, precipitation) characteristics were investigated. Storm flow event responses were analyzed to explore temporal changes and rotational patterns of concentration-discharge relations (hysteresis).

Results reveal a daily pattern in biogeochemical cycles and a strong connection between these cycles and rainfall events. Detected hysteresis showed high consistency at both sites. Turbidity and nitrate values rotated mainly clockwise, BOD counterclockwise. The rotation of COD was site-specific and might be influenced by vegetation cover and/or soil properties. Specific nutrient loads, calculated for both sides, significantly increased further downstream independent of the flow conditions and season.

Due to the consistency of the results for hysteresis loops, frequency patterns within the power spectra and detected wavelet coherencies, we suggest that those tools are suitable indicators of hydro-biogeochemical processes in the páramo.

<< Previous Abstract | Next Abstract >>