@article{TschoepeWallschlaegerBurkartetal.2011, author = {Tsch{\"o}pe, Okka and Wallschl{\"a}ger, Hans-Dieter and Burkart, Michael and Tielb{\"o}rger, Katja}, title = {Managing open habitats by wild ungulate browsing and grazing a case-study in North-Eastern Germany}, series = {Applied vegetation science : official organ of the International Association for Vegetation Science}, volume = {14}, journal = {Applied vegetation science : official organ of the International Association for Vegetation Science}, number = {2}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1402-2001}, doi = {10.1111/j.1654-109X.2010.01119.x}, pages = {200 -- 209}, year = {2011}, abstract = {Question: Can wild ungulates efficiently maintain and restore open habitats? Location: Brandenburg, NE Germany. Methods: The effect of wild ungulate grazing and browsing was studied in three successional stages: (1) Corynephorus canescens-dominated grassland; (2) ruderal tall forb vegetation dominated by Tanacetum vulgare; and (3) Pinus sylvestris-pioneer forest. The study was conducted over 3 yr. In each successional stage, six paired 4 m(2)-monitoring plots of permanently grazed versus ungrazed plots were arranged in three random blocks. Removal of grazing was introduced de novo for the study. In each plot, percentage cover of each plant and lichen species and total cover of woody plants was recorded. Results: Wild ungulates considerably affected successional pathways and species composition in open habitats but this influence became evident in alteration of abundances of only a few species. Grazing effects differed considerably between successional stages: species richness was higher in grazed versus ungrazed ruderal and pioneer forest plots, but not in the Corynephorus sites. Herbivory affected woody plant cover only in the Pioneer forest sites. Although the study period was too short to observe drastic changes in species richness and woody plant cover, notable changes in species composition were still detected in all successional stages. Conclusion: Wild ungulate browsing is a useful tool to inhibit encroachment of woody vegetation and to conserve a species-rich, open landscape.}, language = {en} } @article{TschoepeTielboergerBurkart2002, author = {Tsch{\"o}pe, Okka and Tielb{\"o}rger, Katja and Burkart, Michael}, title = {Offenlandmanagement auf ehemaligen Truppen{\"u}bungspl{\"a}tzen}, year = {2002}, language = {de} } @article{TschoepeTielboerger2010, author = {Tsch{\"o}pe, Okka and Tielb{\"o}rger, Katja}, title = {The role of successional stage and small-scale disturbance for establishment of pioneer grass Corynephorus canescens}, issn = {1402-2001}, doi = {10.1111/j.1654-109X.2009.01072.x}, year = {2010}, abstract = {Question Which mechanisms promote the maintenance of the protected pioneer grass Corynephorus canescens in a mosaic landscape? Which are the interactive effects of small-scale disturbances, successional stage and year-to-year variation on early establishment probabilities of C. canescens? Location Brandenburg, NE Germany. Methods We measured emergence and survival rates over 3 yr in a sowing-experiment conducted in three successional stages (C. canescens- dominated site, ruderal forb site and pioneer forest) under two different regimes of mechanical ground disturbance (disturbed versus undisturbed control). Results Overall, disturbance led to higher emergence in a humid year and to lower emergence in a very dry year. Apparently, when soil moisture was sufficient, the main factor limiting C. canescens' establishment was competition, while in the dry year, water became the limiting factor. Survival rates were not affected by disturbance. In humid years, C. canescens emerged in higher numbers in open successional stages while in the dry year, emergence rates were higher in late stages, suggesting an important role of late successional stages for the persistence of C. canescens. Conclusions Our results suggest that small-scale disturbances can promote germination of C. canescens. However, disturbances should be carefully planned. The optimal strategy for promoting C. canescens is to apply disturbances just before seed dispersal and not during dry years. At the landscape scale, a mosaic of different vegetation types is beneficial for the protected pioneer grass as facilitation by late-successional species may be an important mechanism for the persistence of C. canescens, especially in dry years.}, language = {en} } @article{TschoepeBurkartTielboerger2002, author = {Tsch{\"o}pe, Okka and Burkart, Michael and Tielb{\"o}rger, Katja}, title = {Habitat management in former military training area by means of Megaherbivores}, year = {2002}, language = {en} } @article{TittelBorkRoepkeetal.2000, author = {Tittel, J{\"o}rg and Bork, Rudolf and R{\"o}pke, Bj{\"o}rn and Geldmacher, Karl and Schnur, Tilo and Faust, Berno and Schaphoff, Sibyll and Dalchow, Claus and Woithe, Franka and Bronstert, Axel and Jeltsch, Florian and Jessel, Beate and Zschalich, Andrea and R{\"o}ßling, Holger and Spindler, Joris and Gaedke, Ursula and Tielb{\"o}rger, Katja and Kadmon, R. and M{\"u}ller, J. and Bissinger, Vera and Weithoff, Guntram and Wallschl{\"a}ger, Hans-Dieter and Wiegleb, Gerhard}, title = {Umweltforschung f{\"u}r das Land Brandenburg}, series = {Brandenburgische Umwelt-Berichte : BUB ; Schriftenreihe der Mathematisch-Naturwissenschaftlichen Fakult{\"a}t der Universit{\"a}t Potsdam}, volume = {8}, journal = {Brandenburgische Umwelt-Berichte : BUB ; Schriftenreihe der Mathematisch-Naturwissenschaftlichen Fakult{\"a}t der Universit{\"a}t Potsdam}, issn = {1434-2375}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-3828}, pages = {80 -- 134}, year = {2000}, abstract = {BISSINGER, V.; TITTEL, J.: Process rates and growth limiting factors of planktonic algae (Chlamydomonas sp.) from extremely acidic (pH 2,5 - 3) mining lakes in Germany ; BORK, H.-R. et al.: Erodierte Autos und Brunnen in Oregon, USA ; BRONSTERT, A. et al.: Bewirtschaftunsm{\"o}glichkeiten im Einzugsgebiet der Havel ; JELTSCH, F. et al.: Beweidung als Degradationsfaktor in ariden und semiariden Weidesystemen ; JELTSCH, F. et al.: Entstehung und Bedeutung r{\"a}umlicher Vegetationsstrukturen in Trockensavannen: Baum-Graskoexistenz und Artenvielfalt ; JESSEL, B. et al.: Bodenbewertung f{\"u}r Planungs- und Zulassungsverfahren in Brandenburg ; JESSEL, B.; ZSCHALICH, A.: Erarbeitung von Ausgleichs- und Ersatzmaßnahmen f{\"u}r die Wert- und Funktionselemente des Landschaftsbildes ; R{\"O}ßLING, H. et al.: Umsetzung von Ausgleichs- und Ersatzmaßnahmen beim Ausbau der Bundesautobahn A 9 ; SPINDLER, J.; GAEDKE, U.: Estimating production in plankton food webs from biomass size spectra and allometric relationships ; TIELB{\"O}RGER, K. et al.: Sukzessionsprozesse in einem Sandd{\"u}nengebiet nach Ausschluß von Beweidung ; TIELB{\"O}RGER, K. et al.: Populationsdynamische Funktionen von Ausbreitung und Dormanz ; TIELB{\"O}RGER, K. et al.: Raum-zeitliche Populationsdynamik von einj{\"a}hrigen W{\"u}stenpflanzen ; TITTEL, J. et al.: Ressourcennutzung und -weitergabe im planktischen Nahrungsnetz eines extrem sauren (pH 2,7) Tagebausees ; WALLSCHL{\"A}GER, D.; WIEGLEB, G.: Offenland-Management auf ehemaligen und in Nutzung befindlichen Truppen{\"u}bungspl{\"a}tzen im pleistoz{\"a}nen Flachland Nordostdeutschlands: Naturschutzfachliche Grundlagen und praktische Anwendungen ; WEITHOFF, G.; GAEDKE, U.: Planktische R{\"a}uber-Beute-Systeme: Experimentelle Untersuchung von {\"o}kologischen Synchronisationen}, language = {de} } @article{TielboergerPrasseBornkammetal.2000, author = {Tielb{\"o}rger, Katja and Prasse, R{\"u}diger and Bornkamm, Reinhard and Kadmon, Ronen and Tsoar, H.}, title = {Sukzessionsprozesse in einem Sandd{\"u}nengebiet nach Ausschluß von Beweidung}, year = {2000}, language = {de} } @article{TielboergerKadmonMuelleretal.2000, author = {Tielb{\"o}rger, Katja and Kadmon, Ronen and M{\"u}ller, Monika and Jeltsch, Florian}, title = {Populationsdynamische Funktionen von Ausbreitung und Dormanz}, year = {2000}, language = {de} } @article{TielboergerKadmonMuelleretal.2000, author = {Tielb{\"o}rger, Katja and Kadmon, Ronen and M{\"u}ller, Monika and Jeltsch, Florian}, title = {Raum-zeitliche Populationsdynamik von einj{\"a}hrigen W{\"u}stenpflanzen}, year = {2000}, language = {de} } @article{TielboergerKadmon1997, author = {Tielb{\"o}rger, Katja and Kadmon, Ronen}, title = {Relationships between shrubs and annual communities in a sandy desert ecosystem : a three-year study}, year = {1997}, abstract = {A field study was designed to investigate the effect of shrubs on the dynamics and structure of annual plant communities in a sandy desert ecosystem. Densities of emerging and reproductive plants of all annual species were monitored in permanent quadrats located under shrubs and in open areas between shrubs during three successive years; a relatively dry one, a relatively wet one, and a very dry one. A total of 29 species were recorded in the study. Of these, 19 species did not show any evidence for differences in abundance between the two habitats. Nine species exhibited year-to-year variation in their responses to the shrub-opening gradient, being more common in a particular habitat during one year, and showing no response or even an opposite response during a different year. Only one species was consistently more abundant under shrubs throughout the whole study period, and no species was consistently more abundant in the openings. These findings contradict the hypothesis that annual species associated with desert shrub communities can be categorized into distinct groups based on their 'preference' for shrubs vs. openings. Ordination analyses of community-level patterns indicated that annual communities inhabiting the openings were more stable than those inhabiting the shrub habitat. The main lesson from this study is the importance of long-term observations in studies attempting to characterize community-level responses to environmental gradients.}, language = {en} } @article{TielboergerKadmon2000, author = {Tielb{\"o}rger, Katja and Kadmon, Ronen}, title = {Temporal environmental variation tips the balance between facilitation and interference in desert plants}, year = {2000}, abstract = {Recently, numerous studies have pointed to the importance of positive interactions in natural communities. There is now a broad consensus that the balance between negative and positive interactions should shift along environmental gradients, with competition prevailing under environmentally benign conditions and positive interactions dominating under harsh conditions. A commonly cited example of the importance of facilitation in harsh environments is the preference of desert annual plants for the areas under the canopy of shrubs. The recognition of apparently positive effects of desert shrubs on annuals, however, has been mostly based on density measurements, while fitness parameters of the understory plants have been ignored. Also, the temporal consistency of such effects has not been previously tested. Based on conceptual ideas about the balance between interference and facilitation, we predicted that positive effects of the shrubs on the understory should dominate in dry years, while in favorable years, negative effects would be stronger. We tested our hypothesis by measuring the direction and magnitude of the shrub effect on demographic responses of four desert annual plant species during four consecutive seasons of differing rainfall. The results contradicted our initial hypothesis. Depending on the species, the effect of the shrubs shifted from either negative to neutral or from neutral to positive with increasing annual rainfall. However, this trend was stronger for the effect of shrubs on plant reproductive success than on their densities. Our data highlight the importance of measuring fitness parameters in studies of plant-plant interactions. We suggest that the negative effects of shrubs on plant fitness were due to rainfall interception, while positive effects were related to increased nutrient availability beneath shrubs. However, the mechanisms by which the shrubs and annuals interact can only be resolved using an experimental approach. Our results contradict previous hypotheses about the relative importance of positive and negative interactions along environmental gradients. A simple conceptual model summarizing the proposed role of rainfall in determining the direction of shrub effects on their understory annuals is presented.}, language = {en} } @article{TielboergerKadmon2000, author = {Tielb{\"o}rger, Katja and Kadmon, Ronen}, title = {Indirect effects in a desert plant community : is competition among annuals more intense under shrub canopies?}, year = {2000}, abstract = {An unresolved discussion in contemporary ecology deals with the relative importance of competition along environmental gradients. In deserts, local-scale differences in environmental productivity may be caused by the presence of shrubs, which represent a favorable habitat for annual populations within a nutrient-poor matrix. In this study, we attempted to test the hypothesis that facilitation of desert annuals by shrubs increase the intensity of competition among the annual plants. Such negative indirect effects have so far been ignored in studies about plant-plant interactions. We tested our hypothesis by measuring seedling survival and fecundity of four abundant annual plant species with and without neighbors in open areas and under shrub canopies in a sandy desert area. Our findings did not indicate indirect negative effects of shrubs on their understory annuals. Sensitivity to the presence of neighbors varied between species and surprisingly, the species with the smallest seeds was the only one which was not negatively affected by the presence of neighbors. In contrast to our hypothesis, there was no difference between the habitat types shrubs and openings in absolute and relative competition intensity. Our overall results suggest that negative indirect effects of shrubs are unimportant in determining demographic response of understory annual plants.}, language = {en} } @article{Tielboerger1997, author = {Tielb{\"o}rger, Katja}, title = {The vegetation of linear desert dunes in the north-western Negev, Israel}, year = {1997}, abstract = {In 1992, the flora and vegetation of an area of linear sand dunes at Nizzana, western Negev desert, Israel, was investigated. Seven different plant communities were found and a vegetation map of the research area was produced. The plant communities were distinguished by only the dominating perennial species. Nevertheless, the results of the study indicate, that also annual species may be suitable as a tool to distinguish between desert plant communities.}, language = {en} } @misc{ShiJasminRadhaTielboergeretal.2018, author = {Shi, Jun and Jasmin Radha, Jasmin and Tielb{\"o}rger, Katja and Verhoeven, Koen J. F. and Macel, Mirka}, title = {Costs and benefits of admixture between foreign genotypes and local populations in the field}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {647}, issn = {1866-8372}, doi = {10.25932/publishup-42503}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-425034}, pages = {10}, year = {2018}, abstract = {Admixture is the hybridization between populations within one species. It can increase plant fitness and population viability by alleviating inbreeding depression and increasing genetic diversity. However, populations are often adapted to their local environments and admixture with distant populations could break down local adaptation by diluting the locally adapted genomes. Thus, admixed genotypes might be selected against and be outcompeted by locally adapted genotypes in the local environments. To investigate the costs and benefits of admixture, we compared the performance of admixed and within-population F1 and F2 generations of the European plant Lythrum salicaria in a reciprocal transplant experiment at three European field sites over a 2-year period. Despite strong differences between site and plant populations for most of the measured traits, including herbivory, we found limited evidence for local adaptation. The effects of admixture depended on experimental site and plant population, and were positive for some traits. Plant growth and fruit production of some populations increased in admixed offspring and this was strongest with larger parental distances. These effects were only detected in two of our three sites. Our results show that, in the absence of local adaptation, admixture may boost plant performance, and that this is particularly apparent in stressful environments. We suggest that admixture between foreign and local genotypes can potentially be considered in nature conservation to restore populations and/or increase population viability, especially in small inbred or maladapted populations.}, language = {en} } @article{SchiffersTielboerger2006, author = {Schiffers, Katja and Tielb{\"o}rger, Katja}, title = {Ontogenetic shifts in interactions among annual plants}, doi = {10.1111/j.1365-2745.2006.01097.x}, year = {2006}, abstract = {1.Interactions among plants are key processes that strongly influence the structure and dynamics of plant populations and communities. However, most empirical studies of plant-plant inter­actions failed to repeatedly measure the plants? response to neighboring individuals and thereby neglected possible changes in interactions through­out the life history of the plants.2.Here, we tested the hypo­thesis that competition between annual species intensifies from early to late life history stages. To test this hypothesis, we sequentially measured interactions at different levels of water stress. 3.For this purpose, we con­ducted neighbor-removal experiments in three study sites located along a climatic gradient in Israel. The two annual species Biscutella didyma and Hymenocarpos circinnatus were used as target plants. They grew with and without neighbors in their natural habitats. Five response variables, according to the consecutive life-history stages, (seedling survival, juvenile biomass, adult survival, number of seeds and final biomass) were recorded through­out the whole growing season. 4.The results suggest that direction and inten­sity of inter­actions varied consider­ably between environ­ments and life stages. On average, growth-related response variables indicated higher competition intensity at the productive end of the climatic gradient, while survival indicated either facilitation at the dry end or no trend along the gradient. 5.Considering the temporal aspect, moderate facili­tation short after germi­nation shifted to strong compe­tition at the end of the growing season. 6.Our results highlight that the outcome of experi­mental studies on plant-plant inter­actions may not only depend on the environ­mental productivity but even more on the life stage at which a target plant is found.}, language = {en} } @article{SchiffersSchurrTielboergeretal.2008, author = {Schiffers, Katja and Schurr, Frank Martin and Tielb{\"o}rger, Katja and Urbach, Carsten and Moloney, Kirk A. and Jeltsch, Florian}, title = {Dealing with virtual aggregation : a new index for analysing heterogeneous point patterns}, issn = {0906-7590}, doi = {10.1111/j.0906-7590.2008.05374.x}, year = {2008}, language = {en} } @article{PetruTielboergerBelkinetal.2006, author = {Petru, Martina and Tielb{\"o}rger, Katja and Belkin, Ruthie and Sternberg, Marcelo and Jeltsch, Florian}, title = {Life history variation in an annual plant under two opposing environmental constraints along an aridity gradient}, doi = {10.1111/j.2005.0906-7590.04310.x}, year = {2006}, abstract = {Environmental gradients represent an ideal framework for studying adaptive variation in the life history of plant species. However, on very steep gradients, largely contrasting conditions at the two gradient ends often limit the distribution of the same species across the whole range of environmental conditions. Here, we study phenotypic variation in a winter annual crucifer Biscutella didyma persisting along a steep gradient of increasing rainfall in Israel. In particular, we explored whether the life history at the arid end of the gradient indicates adaptations to drought and unpredictable conditions, while adaptations to the highly competitive environment prevail at the mesic Mediterranean end. We examined several morphological and reproductive traits in four natural populations and in populations cultivated in standard common environment. Plants from arid environments were faster in phenological development, more branched in architecture and tended to maximize reproduction, while the Mediterranean plants invested mainly in vertical vegetative growth. Differences between cultivation and field in diaspore production were very large for arid populations as opposed to Mediterranean ones, indicating a larger potential to increase reproduction under favorable conditions. Our overall findings indicate two strongly opposing selective forces at the two extremes of the aridity gradient, which result in contrasting strategies within the studied annual plant species}, language = {en} } @article{OeserStroncikMoskwaetal.2018, author = {Oeser, Ralf Andreas and Stroncik, Nicole and Moskwa, Lisa-Marie and Bernhard, Nadine and Schaller, Mirjam and Canessa, Rafaella and van den Brink, Liesbeth and K{\"o}ster, Moritz and Brucker, Emanuel and Stock, Svenja and Pablo Fuentes, Juan and Godoy, Roberto and Javier Matus, Francisco and Oses Pedraza, Romulo and Osses McIntyre, Pablo and Paulino, Leandro and Seguel, Oscar and Bader, Maaike Y. and Boy, Jens and Dippold, Michaela A. and Ehlers, Todd and K{\"u}hn, Peter and Kuzyakov, Yakov and Leinweber, Peter and Scholten, Thomas and Spielvogel, Sandra and Spohn, Marie and Ubernickel, Kirstin and Tielb{\"o}rger, Katja and Wagner, Dirk and von Blanckenburg, Friedhelm}, title = {Chemistry and microbiology of the Critical Zone along a steep climate and vegetation gradient in the Chilean Coastal Cordillera}, series = {Catena : an interdisciplinary journal of soil science, hydrology, geomorphology focusing on geoecology and landscape evolution}, volume = {170}, journal = {Catena : an interdisciplinary journal of soil science, hydrology, geomorphology focusing on geoecology and landscape evolution}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0341-8162}, doi = {10.1016/j.catena.2018.06.002}, pages = {183 -- 203}, year = {2018}, abstract = {From north to south, denudation rates from cosmogenic nuclides are similar to 10 t km(-2) yr(-1) at the arid Pan de Aziicar site, similar to 20 t km(2) yr(-1) at the semi-arid site of Santa Gracia, -60 t km(-2) yr(-1) at the Mediterranean climate site of La Campana, and similar to 30 t km(-2) yr(-1) at the humid site of Nahuelbuta. A and B horizons increase in thickness and elemental depletion or enrichment increases from north (similar to 26 degrees S) to south (similar to 38 degrees S) in these horizons. Differences in the degree of chemical weathering, quantified by the chemical depletion fraction (CDF), are significant only between the arid and sparsely vegetated site and the other three sites. Differences in the CDF between the sites, and elemental depletion within the sites are sometimes smaller than the variations induced by the bedrock heterogeneity. Microbial abundances (bacteria and archaea) in saprolite substantially increase from the arid to the semi-arid sites. With this study, we provide a comprehensive dataset characterizing the Critical Zone geochemistry in the Chilean Coastal Cordillera. This dataset confirms climatic controls on weathering and denudation rates and provides prerequisites to quantify the role of biota in future studies.}, language = {en} } @article{MoloneyHolzapfelTielboergeretal.2009, author = {Moloney, Kirk A. and Holzapfel, Claus and Tielb{\"o}rger, Katja and Jeltsch, Florian and Schurr, Frank Martin}, title = {Rethinking the common garden in invasion research}, issn = {1433-8319}, doi = {10.1016/j.ppees.2009.05.002}, year = {2009}, abstract = {In common garden experiments, a number of genotypes are raised in a common environment in order to quantify the genetic component of phenotypic variation. Common gardens are thus ideally suited for disentangling how genetic and environmental factors contribute to the success of invasive species in their new non-native range. Although common garden experiments are increasingly employed in the study of invasive species, there has been little discussion about how these experiments should be designed for greatest utility. We argue that this has delayed progress in developing a general theory of invasion biology. We suggest a minimum optimal design (MOD) for common garden studies that target the ecological and evolutionary processes leading to phenotypic differentiation between native and invasive ranges. This involves four elements: (A) multiple, strategically sited garden locations, involving at the very least four gardens (2 in the native range and 2 in the invaded range); (B) careful consideration of the genetic design of the experiment; (C) standardization of experimental protocols across all gardens; and (D) care to ensure the biosafety of the experiment. Our understanding of the evolutionary ecology of biological invasions will be greatly enhanced by common garden studies, if and only if they are designed in a more systematic fashion, incorporating at the very least the MOD suggested here.}, language = {en} } @article{MetzvonOppenTielboerger2015, author = {Metz, Johannes and von Oppen, Jonathan and Tielb{\"o}rger, Katja}, title = {Parental environmental effects due to contrasting watering adapt competitive ability, but not drought tolerance, in offspring of a semi-arid annual Brassicaceae}, series = {The journal of ecology}, volume = {103}, journal = {The journal of ecology}, number = {4}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0022-0477}, doi = {10.1111/1365-2745.12411}, pages = {990 -- 997}, year = {2015}, abstract = {Parental effects (PE) can be adaptive and improve offspring performance when parents and offspring experience similar environmental conditions. However, it is unknown whether adaptive PE exist also in habitats where such similarity is unlikely due to strong temporal variation. In particular, we do not know whether PE can adapt offspring to fluctuating levels of neighbour competition in such habitats. Here, we tested for adaptive PE in terms of two key environmental factors in a semi-arid annual system, competition and drought. While rainfall was stochastic in the study site, the competitive environment was partly predictable: higher plant densities followed after favourable (rainy) years due to high seed production. We therefore expected PE to adapt the offspring's competitive ability to these (predictable) fluctuations in plant densities, rather than to adapt the offspring's drought tolerance to the (unpredictable) occurrence of intensified drought. Parental plants of Biscutella didyma, an annual Brassicaceae, were raised under favourable watering and under drought conditions. Offspring performance was then tested under a full-factorial combination of two neighbour regimes and six watering levels in the glasshouse. Offspring of parents grown under favourable conditions were stronger competitors. This was associated with a small shift in phenology but not with higher parental seed provisioning. Offspring from parents grown under drought showed no improved drought tolerance. Moreover, no PE were detectable when offspring were grown without neighbours. Our results suggest a novel path of adaptive PE: higher competitive ability was induced in offspring that were more likely to experience high neighbour densities. Together with the lack of adaptive PE towards drought tolerance, this emphasizes that a correlation between parental and offspring environment is crucial for adaptive PE to evolve. Our results also call for the inclusion of competitive effects in future PE studies.Synthesis. This study demonstrates the important role of adaptive PE for plant fitness (regarding competition) but also their limits (regarding drought) in temporally variable environments, based on the predictability of the respective environmental factor.}, language = {en} } @article{KoechyTielboerger2007, author = {K{\"o}chy, Martin and Tielb{\"o}rger, Katja}, title = {Hydrothermal time model of germination : parameters for 36 Mediterranean annual species based on a simplified approach}, issn = {1439-1791}, doi = {10.1016/j.baae.2006.04.002}, year = {2007}, abstract = {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.Abstract auch auf deutsch vorhanden:Keimungsgeschwindigkeit und Anteil gekeimter Samen lassen sich gut mit dem Hydrothermalzeit-Modell bestimmen. Dessen vier Parameter Hydrothermalzeit, Mindesttemperatur, Mindestbodenfeuchte und Streuung der Mindestbodenfeuchte m{\"u}ssen jedoch durch aufwendige Keimungsversuche bei Kombinationen von mehreren Temperatur- und Feuchtigkeitsstufen bestimmt werden. F{\"u}r manche Anwendungen des Hydrothermalzeit-Modells sind aber ungef{\"a}hre Werte f{\"u}r viele Arten wichtiger als genaue Werte f{\"u}r wenige Arten. Wenn die Mindesttemperatur und die Streuung der Mindestfeuchte aus Ver{\"o}ffentlichungen und Expertenwissen gesch{\"a}tzt w{\"u}rde, k{\"o}nnen 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 einj{\"a}hriger Arten entlang eines Trockenheitsgradienten in Israel angewendet. Mit diesem Ansatz bestimmten wir die Hydrothermalzeit und Mindestfeuchtigkeit von 36 Arten. Der Vergleich mit genauen Werten f{\"u}r drei Arten zeigt, dass mit unserem Ansatz Hydrothermalzeit-Parameter einfach und effektiv bestimmt werden k{\"o}nnen. Hydrothermalzeit und Mindestfeuchtigkeit sollten auch bestimmte klimabedingte Keimungsstrategien anzeigen. Deshalb testeten wir, ob diese zwei Parameter mit dem Klima am Ursprungsort der Samen zusammenh{\"a}ngen. Wir fanden jedoch keinen f{\"u}r alle Arten {\"u}bereinstimmenden Zusammenhang, so dass die Unterschiede vermutlich st{\"a}rker durch stand{\"o}rtliche als durch klimatische Ursachen hervorgerufen werden.}, language = {en} }