15 years of ecosystem development at Chicken Creek catchment: conceptual framework, surprises and conclusions.

The Chicken Creek catchment was constructed as a research platform to study initial ecosystem development at the landscape scale (Hüttl et al. 2014). The underlying conceptual framework was based on the idea that 1. patterns and processes evolving during the very first phase of development will have a long-lasting impact on later ecosystem stages, 2. defined boundary conditions and knowledge about subsurface structures of a constructed catchment would allow to better upscale and integrate processes compared to natural catchments, and3. lower complexity of interacting components in young ecosystems allow to better understand the role of abiotic and biotic feedback mechanisms compared to mature systems.After completion of the construction in 2005 (Gerwin et al. 2009), a major challenge was to develop and install a cross-disciplinary long-term monitoring program for the 6 ha area to record major environmental parameters adapted to the development of the site (Schaaf et al. 2013).During its first 15 years, Chicken Creek showed a very dynamic development (Elmer et al 2013). Whereas the abiotic geosystem of the first 2-3 years was characterized by heavy erosion and sediment transport, primary succession by invading vegetation and the unexpected formation of soil crusts within few years resulted in more biotic-abiotic feedbacks that controlled catchment hydrology. Our observations over a period of 15 years indicate that even minor variations in initial substrate characteristics (e.g. texture) can have lasting impacts on geomorphical, hydrological and biological development like erosion intensity, groundwater levels or establishment of vegetation patterns.The time-series of monitoring data combined with a structure model of the catchment (Gerke et al. 2013) allowed the closure of the water balance by relatively simple calculations of water storage volumes and the estimation of evapotranspiration (Schaaf et al. 2017). From these data three stages of ecosystem development were derived which are characterized by increasing influence of biota and increasing system complexity.Elmer, M., Gerwin, W., Schaaf, W., Zaplata, M.K., Hohberg, K., Nenov, R., Bens, O. & Hüttl, R.F. 2013: Dynamics of initial ecosystem development at the artificial catchment Chicken Creek, Lusatia, Germany. Environ. Earth Sci., 69, 491-505.Gerke, H.H., Maurer, T. & Schneider, A., 2013: A Three-Dimensional Structure and Process Model for Integrated Hydro-Geo-Pedologic Analysis of a Constructed Hydrological Catchment. Vadose Zone Journal, 12.Gerwin, W., Schaaf, W., Biemelt, D., Fischer, A., Winter, S. & Hüttl, R.F., 2009: The artificial catchment "Chicken Creek" (Lusatia, Germany) - A landscape laboratory for interdisciplinary studies of initial ecosystem development. Ecological Engineering, 35, 1786-1796.Hüttl, R.F., Gerwin, W., Kögel-Knabner, I., Schulin, R., Hinz, C. & Subke, J.-A., 2014: Ecosystems in transition: interactions and feedbacks with an emphasis on the initial development. Biogeosciences, 11, 195-200.Schaaf, W., Elmer, M., Fischer, A., Gerwin, W., Nenov, R., Pretzsch, H., Seifert, S., Winter, S., Zaplata, M.K., 2013: Monitoring the formation of structures and patterns during initial development of an artificial catchment. Environ. Monit. Assess., 185, 5965-5986.Schaaf, W., Pohle, I., Maurer, T., Gerwin, W., Hinz, C. & Badorreck, A., 2017: Water Balance Dynamics during Ten Years of Ecological Development at Chicken Creek Catchment. Vadose Zone Journal, 16. [ABSTRACT FROM AUTHOR]