Karl Auerswald | Technische Universität München (original) (raw)

Papers by Karl Auerswald

Hochwasserminderung im ländlichen Raum, 2020

Tracking Animal Migration with Stable Isotopes, 2019

ABSTRACT The isotopic turnover, which is a proxy for the metabolic rate, is gaining scientific im... more ABSTRACT The isotopic turnover, which is a proxy for the metabolic rate, is gaining scientific importance. It is quantified for an increasing range of organisms, from microorganisms over plants to animals including agricultural livestock. Additionally, the isotopic turnover is analyzed on different scales, from organs to organisms to ecosystems and even to the biosphere. In particular, the quantification of the isotopic turnover of specific tissues within the same organism, e.g. organs like liver and muscle and products like milk and faeces, has brought new insights to improve understanding of nutrient cycles and fluxes, respectively. Thus, the knowledge of isotopic turnover is important in many areas, including physiology, e.g. milk synthesis, ecology, e.g. soil retention time of water, and medical science, e.g. cancer diagnosis. So far, the isotopic turnover is quantified by applying time, cost and expertise intensive tracer experiments. Usually, this comprises two isotopic equilibration periods. A first equilibration period with a constant isotopic input signal is followed by a second equilibration period with a distinct constant isotopic input signal. This yields a smooth signal change from the first to the second signal in the object under consideration. This approach reveals at least three major problems. (i) The input signals must be controlled isotopically, which is almost impossible in many realistic cases like free ranging animals. (ii) Both equilibration periods may be very long, especially when the turnover rate of the object under consideration is very slow, which aggravates the first problem. (iii) The detection of small or slow pools is improved by large isotopic signal changes, but large isotopic changes also involve a considerable change in the input material; e.g. animal studies are usually carried out as diet-switch experiments, where the diet is switched between C3 and C4 plants, since C3 and C4 plants differ strongly in their isotopic signal. The additional change in nutrition induces changes in physiology that are likely to bias the estimation of the isotopic turnover. We designed an experiment with lactating cows which were successively exposed to the diet's natural isotopic variation and a diet-switch. We examined whether the same turnover information can be obtained from the natural (uncontrolled, short-term) isotopic variation as from the diet-switch experiment. Statistical methods to retrieve the turnover characteristics comprised multi-pool compartmental modeling for the diet-switch experiment as well as correlation analysis to perform wiggle-matching and quantification of autocorrelation (geostatistics) for the analysis of the natural variation. All three methods yielded similar results but differed in their strengths and weaknesses that will be highlighted. Combining the strengths of the new methods can make this tool even more advantageous than diet-switch experiments in many cases. In particular, the new approach empowers studying isotope turnover under a wider range of keepings, wildlife conditions and species, yielding turnover estimates that are not biased by changes in nutrition.

Environmental Science & Policy, 2016

Berichte zur deutschen Landeskunde

Zeitschrift für Pflanzenernährung und Bodenkunde, 1998

ABSTRACT Enrichment ratios (ER) are widely used to predict loss of sorbed nutrients or pesticides... more ABSTRACT Enrichment ratios (ER) are widely used to predict loss of sorbed nutrients or pesticides with runoff sediment, while ER is frequently neglected in studies which quantify past erosion from global fallout 137Cs losses. The ER of 137Cs (ER- 137Cs) in the soil loss and the subsequent depletion of 137Cs at the soil surface were determined for eight small watersheds (1.6–16.8 ha) with different soils and land use. Due to preferential loss of the clay fraction, the upper 5 mm of the soil surface was significantly depleted of 137Cs after a heavy storm. A total of 31 watershed-events were investigated with soil losses ranging between 1.2 and 480 kg-ha−1 and sediment concentrations between 1.98 and 54.1 gṁL−1 The correspondent ER-137Cs (mean: 1.72, range: 0.40–4.95) was positively correlated to the ER of clay, organic carbon, total nitrogen and calcium-acetate-lactate-extractable phosphorus (PCAL). A close correlation between ER-137Cs and ER-PCAL was also found for sediment samples of detention ponds, where most of the ER values were less than 1.0 due to depletion. Therefore, ER-PCAL seems to be a suitable estimate of ER-137Cs for both, erosion and deposition processes. Our findings strongly support the need for considering ER-137Cs, when ,37Cs data are used to assess rates and pattern of soil redistribution. Otherwise, soil loss will be overestimated in a range of about factor 2 in many cases.Die Anreicherung von 137Cs im Bodenabtrag kleiner, landwirtschaftlich genutzter EinzugsgebieteAnreicherungsverhältnisse (ER) werden häufig benutzt, um die Verluste von sedimentgebundenen Nährstoffen oder Pestiziden mit dem Oberfläcbenabfluß vorherzusagen. Bei Untersuchungen, welche die Erosion retrospektiv über den Verlust von Fallout-137Cs quantifizieren, werden ER dagegen häufig vernachlässigt. Die Anreicherung von 137Cs (ER-137Cs) im Bodenabtrag und die damit einhergehende Verarmung der Bodenoberfläche wurde für 8 kleine Einzugsgebiete (1.6–16.8 ha) mit unterschiedlichen Böden und Nutzungen untersucht. Der Uberproportionale Verlust der Tonfraktion führte nach einem heftigen Gewitterregen zur signifikanten Abreicherung von 137Cs in den obersten 5 mm des Bodens. Insgesamt wurden 31 Abflußereignisse untersucht mit Bodenabtragen von 1.2 bis 480 kgṁha−1 und Sedimentkonzentrationen von 1.98 bis 54.1 gṁL−1. ER-137Cs betrug im Mittel 1.72 (0.40–4.95) und korrelierte positiv mit dem ER von Ton, von organischem Kohlenstoff, Gesamtstickstoff und CAL-extrahierbarem Phosphat (PCAL). Eine enge Korrelation zwischen ER-137Cs und ER-PCAL wurde auch bei Sedimentproben kleiner Abfluß-Rückhaltebecken gefunden, bei denen wegen Abreicherung die ER meist kleiner als 1.0 waren. ER-PCAL erscheint daher gut geeignet zur Abschätzung von ER-137Cs, sowohl bei Erosions- als auch Depositionsprozessen. Die vorliegende Untersuchung bekräftigt die Forderung, ER-137Cs miteinzubeziehen, wenn 137Cs-Daten verwendet werden, um Ausmaß und Muster von Bodenumverlagerungen zu bestimmen. Andernfalls wird der Bodenabtrag in vielen Fallen etwa um den Faktor 2 überschätzt.