TY - GEN A1 - Köchy, Martin T1 - Stochastic time series of daily precipitation for the interior of Israel N2 - This contribution describes a generator of stochastic time series of daily precipitation for the interior of Israel from c. 90 to 900 mm mean annual precipitation (MAP) as a tool for studies of daily rain variability. The probability of rainfall on a given day of the year is described by a regular Gaussian peak curve function. The amount of rain is drawn randomly from an exponential distribution whose mean is the daily mean rain amount (averaged across years for each day of the year) described by a flattened Gaussian peak curve. Parameters for the curves have been calculated from monthly aggregated, long-term rain records from seven meteorological stations. Parameters for arbitrary points on the MAP gradient are calculated from a regression equation with MAP as the only independent variable. The simple structure of the generator allows it to produce time series with daily rain patterns that are projected under climate change scenarios and simultaneously control MAP. Increasing within-year variability of daily precipitation amounts also increases among-year variability of MAP as predicted by global circulation models. Thus, the time series incorporate important characteristics for climate change research and represent a flexible tool for simulations of daily vegetation or surface hydrology dynamics. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 029 KW - stochastische Zeitreihen KW - täglicher Niederschlag KW - Israel KW - Klimawandel KW - stochastic time series KW - daily precipitation KW - Israel KW - climate change Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-13155 ER - TY - GEN A1 - Köchy, Martin A1 - Tielbörger, Katja T1 - Hydrothermal time model of germination : parameters for 36 Mediterranean annual species based on a simplified approach N2 - Germination rates and germination fractions of seeds can be predicted well by the hydrothermal time (HTT) model. Its four parameters hydrothermal time, minimum soil temperature, minimum soil moisture, and variation of minimum soil moisture, however, must be determined by lengthy germination experiments at combinations of several levels of soil temperature and moisture. For some applications of the HTT model it is more important to have approximate estimates for many species rather than exact values for only a few species. We suggest that minimum temperature and variation of minimum moisture can be estimated from literature data and expert knowledge. This allows to derive hydrothermal time and minimum moisture from existing data from germination experiments with one level of temperature and moisture. We applied our approach to a germination experiment comparing germination fractions of wild annual species along an aridity gradient in Israel. Using this simplified approach we estimated hydrothermal time and minimum moisture of 36 species. Comparison with exact data for three species shows that our method is a simple but effective method for obtaining parameters for the HTT model. Hydrothermal time and minimum moisture supposedly indicate climate related germination strategies. We tested whether these two parameters varied with the climate at the site where the seeds had been collected. We found no consistent variation with climate across species, suggesting that variation is more strongly controlled by site-specific factors. N2 - Keimungsgeschwindigkeit und Anteil gekeimter Samen lassen sich gut mit dem Hydrothermalzeit-Modell bestimmen. Dessen vier Parameter Hydrothermalzeit, Mindesttemperatur, Mindestbodenfeuchte und Streuung der Mindestbodenfeuchte müssen jedoch durch aufwendige Keimungsversuche bei Kombinationen von mehreren Temperatur- und Feuchtigkeitsstufen bestimmt werden. Für manche Anwendungen des Hydrothermalzeit-Modells sind aber ungefähre Werte für viele Arten wichtiger als genaue Werte für wenige Arten. Wenn die Mindesttemperatur und die Streuung der Mindestfeuchte aus Veröffentlichungen und Expertenwissen geschätzt würde, können die Hydrothermalzeit und Mindestbodenfeuchte aus vorhandenen Daten von Keimungsversuchen mit nur einer Temperatur- und Feuchtigkeitsstufe berechnet werden. Wir haben unseren Ansatz auf einen Keimungsversuch zum Vergleich der Keimungsquote wilder einjähriger Arten entlang eines Trockenheitsgradienten in Israel angewendet. Mit diesem Ansatz bestimmten wir die Hydrothermalzeit und Mindestfeuchtigkeit von 36 Arten. Der Vergleich mit genauen Werten für drei Arten zeigt, dass mit unserem Ansatz Hydrothermalzeit-Parameter einfach und effektiv bestimmt werden können. Hydrothermalzeit und Mindestfeuchtigkeit sollten auch bestimmte klimabedingte Keimungsstrategien anzeigen. Deshalb testeten wir, ob diese zwei Parameter mit dem Klima am Ursprungsort der Samen zusammenhängen. Wir fanden jedoch keinen für alle Arten übereinstimmenden Zusammenhang, so dass die Unterschiede vermutlich stärker durch standörtliche als durch klimatische Ursachen hervorgerufen werden. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 022 KW - Keimungsrate KW - Dormanz KW - Hydrothermalzeit-Modell KW - einjährige Pflanzen KW - Mittelmeerraum KW - germination rate KW - dormancy KW - hydrothermal time model KW - annual plant species KW - Mediterranean Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12406 ER - TY - GEN A1 - Schultze, Rainer H. A1 - Lemke, Matthias A1 - Löhmannsröben, Hans-Gerd T1 - Laser-induced fluorescence (LIF) spectroscopy for the in situ analysis of petroleum product-contaminated soils N2 - Contents: Introduction Experimental Techniques: The LIF demonstrator unit - The LIF demonstrator unit - The mobile LIF spectrometer OPTIMOS - Investigated petroleum products and soil samples Results and Discussion: Photophysical properties of the petroleum products LIF spectroscopic investigations of oil-spiked samples LIF spectroscopic investigations of real-world soils Conclusions T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 9 Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12271 ER - TY - GEN A1 - Heinken, Thilo A1 - Raudnitschka, Dorit T1 - Do wild ungulates contribute to the dispersal of vascular plants in central European forests by epizoochory? BT - A case study in NE Germany BT - Eine Fallstudie aus Nordostdeutschland N2 - The external dispersal ("epizoochory") of vascular plant diaspores (seeds and fruits) by roe deer and wild boar, i.e. the most common wild large mammals with a large home range in central Europe, was investigated in a 6.5-km² forest area in NE Germany dominated by mesic deciduous forests. The study involved brushing out the diaspores from the coats and hooves of 25 shot roe deer and nine wild boar. The results were compared with the forest vegetation of the study area. Whilst wild boar transported large amounts of various diaspores in the coat, the significance of roe deer for epizoochory was low due to their sleek fur and different behaviour compared to wild boar. Altogether, 55 vascular plant species were transported externally. Since only a limited number of seeds came from woodland habitats, the open landscape was at least as important as a source of attached seeds as the forest vegetation. Thus, most plant species occurring in the studied forest area, especially characteristic woodland herbs, showed no adaptations to epizoochorous dispersal, although being very abundant in the herb layer. We conclude that hoofed game play a particular role concerning the dispersal of ruderal and grassland species in the agricultural landscape of central Europe. However, the actual spread of some herb species in forests of northern Germany, e.g. Agrostis capillaris, Brachypodium sylvaticum, Deschampsia flexuosa, Galium aparine and Urtica dioica, may be mainly facilitated by wild ungulates. Though dispersal by large mammals is an important mechanism for long-distance dispersal of plants in general, our results suggest that most of the characteristic herb species of mesic deciduous forests have only low epizoochorous dispersal potentials. The implications for nature conservation and silviculture are discussed. N2 - Die Ausbreitung von Gefäßpflanzen-Diasporen (Samen und Früchte) durch äußerliche Anhaftung ("Epizoochorie") an Rehen und Wildschweinen, den beiden häufigsten Schalenwild-Arten in Mitteleuropa, wurde im 6,5 km² großen Forst Brieselang bei Berlin (Bundesland Brandenburg) untersucht, in dem mesophile Laubwälder vorherrschen. Dazu wurden die Felle und Hufe von 25 geschossenen Rehen und neun Wildschweinen ausgekämmt und die Diasporen anschließend bestimmt. Die Ergebnisse wurden mit der Waldvegetation verglichen. Während Wildschweine große Mengen verschiedener Diasporentypen transportierten, war die Bedeutung von Rehen für die Ausbreitung von Pflanzen auf Grund des glatten Fells und der im Vergleich zum Wildschwein unterschiedlichen Verhaltensweisen wesentlich geringer. Insgesamt wurden 55 Phanerogamenarten epizoochor transportiert. Da nur ein kleiner Teil der ausgebreiteten Pflanzen Waldhabitate bevorzugt, war das Offenland eine mindestens ebenso wichtige Quelle anhaftender Diasporen wie die Waldvegetation. Die meisten Waldpflanzenarten wurden nicht ausgebreitet; insbesondere solche Arten, die ausschließlich in Wäldern wachsen, wurden nicht nachgewiesen. Viele Pflanzenarten sind – vermutlich auf Grund ihrer Diasporenmorphologie – weitgehend vom Transport ausgeschlossen, obwohl sie sehr häufig in der Krautschicht des untersuchten Waldes vorkommen. Daher ist Schalenwild in der Agrarlandschaft Mitteleuropas vermutlich vor allem für die Ausbreitung von Ruderal-, Segetal- und Grünlandpflanzen von Bedeutung. Die Ausbreitung einiger Pflanzenarten der Krautschicht in norddeutschen Wäldern z.B. Agrostis capillaris, Brachypodium sylvaticum, Deschampsia flexuosa, Galium aparine und Urtica dioica, könnte jedoch wesentlich auf Schalenwild zurückgehen. Obwohl Großsäuger insgesamt ein wichtiger Vektor für die Fernausbreitung von Pflanzen sind, zeigt unsere Studie, dass die meisten charakteristischen Waldbodenpflanzen mesophiler Laubwälder kaum ausgebreitet werden, also nur ein geringes epizoochores Ausbreitungspotenzial aufweisen. Die Bedeutung der Ergebnisse für den Waldnaturschutz und den Waldbau wird diskutiert. T2 - Trägt Schalenwild durch Epizoochorie zur Ausbreitung von Gefäßpflanzen in mitteleuropäischen Wäldern bei? KW - Diasporenmorphologie KW - Epizoochorie KW - Brandenburg KW - Reh KW - Waldbodenpflanzen KW - Wildschwein KW - diaspore morphology KW - epizoochory KW - forest plant species KW - NE Germany KW - roe deer KW - wild boar Y1 - 2002 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-5850 ER - TY - GEN A1 - Heinken, Thilo T1 - Migration of an annual myrmecochore BT - a four year experiment with Melampyrum pratense L. N2 - A seed sowing experiment was conducted in a mixed secondary woodland on acidic soils in NE Germany with Melampyrum pratense, an annual ant-dispersed forest herb which lacks a natural population in the study area, but is abundant in similar habitats. Each set of 300 seeds was sown within one square metre at three sites in 1997, and the development of the populations was recorded from 1998 onward. Additionally, seed fall patterns were studied in a natural population by means of adhesive cardboard. All trials resulted in the recruitment of populations, which survived and increased in both individual number and area, up to the year 2001. Thus, local distribution of Melampyrum pratense is dispersallimited. Total individual number increased from 105 to 3,390, and total population area from 2.07 to 109.04 m². Migration occurred in all directions. Mean migration rate was 0.91 m per year, and the highest migration rate was 6.48 m. No individual was recorded beyond 7.63 m from the centres of the sawn squares after three years, suggesting exclusive short-distance dispersal. As primary dispersal enables only distances of up to 0.25 m, ants are presumed to be the main dispersal vectors. Despite differences in individual number and colonization patterns, migration rates did not differ significantly between the populations, but were significantly higher in 2001 due to an increased population size. Colonization patterns were characterized by a rapid, negative exponential decrease of population density with increasing distance from the sown plot, suggesting a colonization by establishment of more or less isolated outposts of individuals and a subsequent gradual infill of the gaps between. My results resemble myrmecochorous dispersal distances in temperate woodlands, and migration rates and patterns across ecotones from ancient to recent deciduous forests. They may function as a colonization model of Melampyrum pratense after accidental long-distance dispersal. KW - artificial introduction KW - colonization KW - dispersal KW - myrmecochory KW - NE Germany KW - woodland herb Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-5865 ER - TY - GEN A1 - Hoppert, Michael A1 - Reimer, Rudolph A1 - Kemmling, Anne A1 - Schröder, Annekatrin A1 - Günzl, Bettina A1 - Heinken, Thilo T1 - Structure and reactivity of a biological soil crust from a xeric sandy soil in Central Europe N2 - The investigation was designed to explore the structure, composition and activity of a biological soil crust on an acidic, sandy soil from a temperate climate. The crust covers several hundreds of square meters on the hilltop of a large terminal moraine. The conjugate alga Zygogonium ericetorum forms the essential matrix for the crust, a dense web of algal filaments with interspersed lichens and mosses. The crust is composed of three layers, with an uppermost layer consisting nearly entirely of a dense algal mat. In lower layers, a parasitic fungus, penetrating the algal cells, is another important component of the crust community. In this soil crust, photosynthetic and respiratory activity is stabilized at low water activities. KW - biological soil crust KW - desiccation tolerance KW - electron microscopy KW - Fusarium oxysporum KW - Zygogonium ericetorum Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-5872 ER - TY - GEN A1 - Köchy, Martin A1 - Wilson, Scott D. T1 - Variation in nitrogen deposition and available soil nitrogen in a forest–grassland ecotone in Canada N2 - Regional variation in nitrogen (N) deposition increases plant productivity and decreases species diversity, but landscape- or local-scale influences on N deposition are less well-known. Using ion-exchange resin, we measured variation of N deposition and soil N availability within Elk Island National Park in the ecotone between grassland and boreal forest in western Canada. The park receives regionally high amounts of atmospheric N deposition (22 kg ha⁻¹ yr⁻¹). N deposition was on average higher ton clayrich luvisols than on brunisols, and areas burned 1 – 15 years previously received more atmospheric N than unburned sites. We suggest that the effects of previous fires and soil type on deposition rate act through differences in canopy structure. The magnitude of these effects varied with the presence of ungulate grazers (bison, moose, elk) and vegetation type (forest, shrubland, grassland). Available soil N (ammonium and nitrate) was higher in burned than unburned sites in the absence of grazing, suggesting an effect of deposition. On grazed sites, differences between fire treatments were small, presumably because the removal of biomass by grazers reduced the effect of fire. Aspen invades native grassland in this region, and our results suggest that fire without grazing might reinforce the expansion of forest into grassland facilitated by N deposition. KW - fire KW - grazing KW - vegetation type KW - soil type KW - shrubland KW - forest invasion KW - subboreal KW - aspen parkland KW - Canada Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-5768 ER -