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- ecosystem development (2)
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BTU
The formation of erosion rills and gullies is a critical step in land surface development, but possibilities to study initial unaffected surface development under natural conditions and with well-defined initial and boundary conditions are rare. The objective of this study was to characterize rill network development from ’point zero’ in the artificially-created catchment ‘Hühnerwasser’. To ensure unaffected development, the study was largely restricted to the analysis of remotely-sensed data. We analyzed a series of photogrammetry-based digital elevation models (DEMs) for 10 points in time, over a period of five years and beginning with the initial state. The evolving erosion rill network was quantitatively described based on mapping from aerial photographs. DEMs and rill network maps were combined to specifically analyze the development of morphometry for different parts of the network and to characterize energy dissipation and connectivity. The restriction to remote-sensing data did not allow for analyzing specific processes governing rill network development, nevertheless, two major development phases could be characterized. We observed a phase of growth of the rill network along with variations in drainage patterns during the first two years of development and a subsequent phase of reduction of its area along with comparably stable patterns. Region-specific analysis of morphometry indicates that, besides effects of changing sediment characteristics and vegetation cover development, locally evolving hydro-geomorphic feedback cycles influenced this development. Results show an increasing similarity of overall statistical characteristics (e.g. drainage density) for two parts of the catchment, but a persistent influence of initial conditions on specific rill geometry. The observed development towards higher orderliness and increased connectivity is consistent with experiments and concepts on drainage network evolution across scales; however, we did not observe major influences of rill piracy and cross grading or a reduction of energy dissipation with network development.
Methoden der Fernerkundung gewinnen in der ökologischen Forschung zunehmend an Bedeutung und sind in vielen Bereichen bereits fest etabliert. Am Beispiel der Vegetationssukzession an und in einem neu angelegten Teich soll das Potential der GIS-basierten Auswertung von Luftbildern aufgezeigt werden. Das künstlich angelegte Wassereinzugsgebiet „Hühnerwasser“ im Bereich des Niederlausitzer Braunkohlentagebaus Welzow-Süd wird als Modell für die initiale Entwicklung eines Ökosystems genutzt. Für das Gebiet wurde im September 2005 mit Beendigung der Bauarbeiten der „Punkt Null" einer unbeeinflussten Sukzession definiert. Im am tiefsten
gelegenen Bereich der 6 ha großen Fläche wurde eine Senke geschaffen, in der sich in wenigen Monaten ein Teich mit einer Fläche von ca. 3.800 m² und einem Volumen von rund 4.000 m³ entwickelte. Seine maximale Tiefe betrug 2,4 m. Die Gebietsentwicklung wird im Rahmen eines umfangreichen Monitorings u.a. mit regelmäßigen Vegetationskartierungen erfasst. Etwa 20 % des ursprünglichen Seevolumens gingen innerhalb der ersten drei Jahre durch erosionsbedingte Sedimenteinträge aus dem Einzugsgebiet verloren. Durch den zunehmenden Rückhalt der Mittel- und Grobsande im sich im Teichzulaufbereich ausbildenden Schwemmfächer gelangten in der Folge überwiegend feinkörniges Sediment aus Ton und
Schluff (< 0,06 mm) in den Teich, die sich in den nördlichen und zentralen tieferen Bereichen ablagerten. Die fortschreitende Vegetationsentwicklung im Einzugsgebiet führte zudem zu einer Abnahme der Erosionsprozesse und begünstigte auch die rasche Ausbreitung von emersen und submersen Makrophyten im Teich und um den Teich herum. Die Ufervegetation erwies sich als wirksame Sedimentfalle, die dem weiteren Eintrag mineralischer Stoffe entgegenwirkte.
Zur Darstellung der Vegetationsentwicklung an und um den Teich herum wurden GIS-basierte Verfahren der Luftbildauswertung herangezogen. Zu Beginn der Vegetationsentwicklung dominierten am Gewässerrand Schilf (Phragmites australis) und mit deutlich geringerem
Deckungsgrad Breitblättriger Rohrkolben (Typha latifolia). Die Makrophyten-Besiedlung im Teich setzte sich aus drei Potamogeton-Arten (P. pectinatus, P. lucens und P. natans),
Myriophyllum spicatum und Chara globularis zusammen. Im Jahr 2009 war P. pectinatus die häufigste Makrophytenart im Teich, gefolgt von P. lucens und M. spicatum, P. natans und
Chara globularis. 2015 dominierten dann P. lucens und P. natans, Ch. globularis. P. pectinatus und M. spicatum wurden nicht mehr gefunden. Der Schilfgürtel erstreckte sich inzwischen auf nahezu alle Teichbereiche mit einer Wassertiefe von weniger als 1 m.
Water budget components
(2011)
Introduction
(2011)
Meteorology
(2010)
Our investigations at the artificial catchment ´Chicken Creek´ in Lusatia/Germany aim to disentangle and understand the feedback mechanisms and interrelationships of processes and their co-development with spatial and temporal structures and patterns by studying this initial, probably less complex ecosystem. Intensive measurements were carried out in the catchment with regard to the development of surface structures, hydrological patterns, and vegetation dynamics.
During the first seven years, considerable changes within the catchment were observed. Both internal and external factors could be identified as driving forces for the formation of structures and patterns in the artificial catchment. Initial structures formed by the construction process and initial substrate characteristics were decisive for the distribution and flow of water. External factors like episodic events triggered erosion and dissection during this initial phase, promoted by the low vegetation cover and the unconsolidated sandy substrate.
The transformation of the initial geo-system into areas with evolving terrestrial or aquatic characteristics and from a very episodic to a more permanent stream network and discharge, together with the observed vegetation dynamics increased site diversity and heterogeneity with respect to water and nutrient availability and transformation processes compared to the more homogenous conditions at point zero.
The processes and feedback mechanisms in the initial development of a new landscape may deviate in rates, intensity and dominance from those known from mature ecosystems. It is therefore crucial to understand these early phases of ecosystem development and to disentangle the increasingly complex interactions between the evolving terrestrial and aquatic, biotic and abiotic compartments of the system. Artificially created catchments could be a suitable tool to study these initial developments at the landscape scale under known, designed and defined boundary conditions.
The objective of this paper is to present observations, results from monitoring measurements, and preliminary conclusions about the development of patterns and structures during the first 5 years of development of an artificial catchment starting from point zero. We discuss the high relevance of initial system traits and external events for the system development and draw conclusions for further research. These investigations as part of a Collaborative Research Center, aim to disentangle and understand the feedback mechanisms and interrelationships of processes and their co-development with spatial and temporal structures and patterns by studying an initial, probably less complex ecosystem. Therefore, intensive measurements were carried out in the catchment with regard to the development of surface structures, hydrological patterns, vegetation dynamics, water chemistry, and element budgets. During the first 5 years, considerable changes within the catchment were observed. Both internal and external factors could be identified as driving forces for the formation of structures and patterns in the artificial catchment. Initial structures formed by the construction process and initial substrate characteristics were decisive for the distribution and flow of water. External factors like episodic events triggered erosion and dissection during this initial phase, promoted by the low vegetation cover, and the unconsolidated sandy substrate. The transformation of the initial geosystem into areas with evolving terrestrial or aquatic characteristics and from a very episodic to a more permanent stream network and discharge, together with the observed vegetation dynamics increased site diversity and heterogeneity with respect to water and nutrient availability and transformation processes compared with the more homogenous conditions at point zero. The processes and feedback mechanisms in the initial development of a new landscape may deviate in rates, intensity, and dominance from those known from mature ecosystems. It is therefore crucial to understand these early phases of ecosystem development and to disentangle the increasingly complex interactions between the evolving terrestrial and aquatic, biotic, and abiotic compartments of the system. Long-term monitoring of initial ecosystems may provide important data and parameters on processes and the crucial role of spatial and temporal structures and patterns to solve these problems. Artificially created catchments could be a suitable tool to study these initial developments at the landscape scale under known, designed, and defined boundary conditions.
We studied the role of strutures and processes and their feedbacks during initial ecosystem development in the artificial catchment Chicken Creek. During the first seven years, considerable changes within the catchment were observed. Both internal and external factors could be identified as driving forces for the formation of structures and patterns in the artificial catchment. Initial structures formed by the construction process and initial substrate
characteristics were decisive for the distribution and flow of water. External factors like episodic events triggered erosion and dissection during this initial phase, promoted by the low vegetation cover and the unconsolidated sandy substrate.
The transformation of the initial geo-system into areas with evolving terrestrial or aquatic characteristics and from a very episodic to a more permanent stream network and discharge, together with the observed vegetation dynamics increased site diversity and heterogeneity with respect to water and nutrient availability and transformation processes compared to the more homogenous conditions at point zero.
The processes and feedback mechanisms in the initial development of a new landscape may deviate in rates, intensity and dominance from those known from mature ecosystems. It is therefore crucial to understand these early phases of ecosystem development and to disentangle the increasingly complex interactions between the evolving terrestrial and aquatic, biotic and abiotic compartments of the system. Artificially created catchments could be a
suitable tool to study these initial developments at the landscape scale under known, designed and defined boundary conditions.