@book{WeberJoshi2009, author = {Weber, Ewald and Joshi, Jasmin Radha}, title = {Biologische Invasionen : Mechanismen, Auswirkungen, Chancen und Risiken}, series = {Neujahrsblatt / Naturforschende Gesellschaft in Z{\"u}rich}, volume = {212}, journal = {Neujahrsblatt / Naturforschende Gesellschaft in Z{\"u}rich}, publisher = {Verl. Koprint}, address = {Alpnach Dorf}, pages = {76 S. : Ill., graph. Darst., Kt.}, year = {2009}, abstract = {Die spontane Ausbreitung nicht-einheimischer oder exotischer Arten, unabsichtlich eingeschleppt bzw. absichtlich eingefuehrt, ist heute ein weltweit zu beobachtendes Phaenomen. Arten werden in grossem Umfang zwischen Kontinenten ausgetauscht und innerhalb der Kontinente verfrachtet; in erster Linie eine Folge des weltweiten Handels und Reiseverkehrs. Einige (aber nicht alle) dieser verwilderten Exoten breiten sich rasant aus und ihr Massenvorkommen zieht nachteilige Auswirkungen auf Mensch und Umwelt nach sich. Solche invasive Arten sind heutzutage ein zentrales Thema im internationalen Naturschutz und in der oekologischen Forschung. Die Ausbreitung invasiver Organismen, als biologische Invasionen bezeichnet, gilt mittlerweile neben Lebensraumzerstoerung als die zweitwichtigste Ursache des weltweiten Artenrueckganges. Die Mechanismen, die zu einer biologischen Invasion fuehren koennen, sind sehr vielfaeltig und beruhen auf Eigenschaften der Arten sowie des betreffenden neuen Lebensraumes. Offene Habitate mit geringem Konkurrenzdruck anderer Arten und ohne spezialisierte Frassfeinde und Pathogene zeigen sich als besonders anfaellig fuer die Besiedlung invasiver Arten. Unter invasive Arten fallen auch solche, die in der Land- und Forstwirtschaft Schaeden verursachen oder die Gesundheit des Menschen gefaehrden. In der Schweiz sind ueber 800 exotische Pflanzen-, Tier-, und Pilz-Arten etabliert, von diesen gelten 107 Arten als invasiv. Welche Massnahmen ergriffen werden sollen, richtet sich nach der Haeufigkeit der Art, aber auch nach der Zielsetzung. Die kostenguenstigsten Massnahmen sind praeventive Massnahmen. Die Gruende, wie es zu biologischen Invasionen kommen kann, welche Eigenschaften invasive Arten aufweisen, ob und wie schnell sich verschleppte Arten im neuen Verbreitungsgebiet evolutiv veraendern koennen, und welches die beste Strategie im Umgang mit invasiven Arten ist, ist Gegenstand dieser Schrift.}, language = {de} } @article{VanKleunenWeberFischer2010, author = {Van Kleunen, Mark and Weber, Ewald and Fischer, Markus}, title = {A meta-analysis of trait differences between invasive and non-invasive plant species}, issn = {1461-023X}, year = {2010}, abstract = {A major aim in ecology is identifying determinants of invasiveness. We performed a meta-analysis of 117 field or experimental-garden studies that measured pair-wise trait differences of a total of 125 invasive and 196 non-invasive plant species in the invasive range of the invasive species. We tested whether invasiveness is associated with performance-related traits (physiology, leaf-area allocation, shoot allocation, growth rate, size and fitness), and whether such associations depend on type of study and on biogeographical or biological factors. Overall, invasive species had significantly higher values than non-invasive species for all six trait categories. More trait differences were significant for invasive vs. native comparisons than for invasive vs. non-invasive alien comparisons. Moreover, for comparisons between invasive species and native species that themselves are invasive elsewhere, no trait differences were significant. Differences in physiology and growth rate were larger in tropical regions than in temperate regions. Trait differences did not depend on whether the invasive alien species originates from Europe, nor did they depend on the test environment. We conclude that invasive alien species had higher values for those traits related to performance than non-invasive species. This suggests that it might become possible to predict future plant invasions from species traits.}, language = {en} } @article{Weber2011, author = {Weber, Ewald}, title = {Strong regeneration ability from rhizome fragments in two invasive clonal plants (Solidago canadensis and S. gigantea)}, series = {Biological invasions : unique international journal uniting scientists in the broad field of biological invasions}, volume = {13}, journal = {Biological invasions : unique international journal uniting scientists in the broad field of biological invasions}, number = {12}, publisher = {Springer}, address = {Dordrecht}, issn = {1387-3547}, doi = {10.1007/s10530-011-9977-y}, pages = {2947 -- 2955}, year = {2011}, abstract = {The two rhizomatous perennials Solidago canadensis and S. gigantea belong to the most widespread alien plants in Europe. Anecdotal observations suggest that they disperse also by rhizome fragments. For testing their resprouting ability, rhizome fragments of different sizes from both species were buried at four different soil depths (0, 5, 10 and 20 cm, respectively) in a common garden. Rhizome fragments of S. canadensis ranged 3-6 cm in length, those of S. gigantea 5-20 cm in length. Resprouting plants were harvested after 3 months and growth related traits measured to assess their vitality. Resprouting rate in S. gigantea was far higher than in S. canadensis (85 and 19\%, respectively). In S. gigantea, fragments of all sizes resprouted from all soil depths whereas none rhizome of S. canadensis emerged from 20 cm burial depth. In S. gigantea, size related traits showed significant interactions between fragment size and burial depth, but not relative shoot growth rate. At all burial depths, vitality of plants emerging from small rhizomes was lower than plants emerging from large rhizomes. Effects of rhizome size became stronger with increasing burial depth. The results show that both species are able to resprout from buried rhizome fragments, and that succesful regeneration is more likely to occur in S. gigantea. Managing these species should avoid any activities promoting rhizome fragmentation and dispersal of fragments.}, language = {en} } @article{KhurooWeberMaliketal.2011, author = {Khuroo, Anzar A. and Weber, Ewald and Malik, A. H. and Reshi, Zafar A. and Dar, G. H.}, title = {Altitudinal distribution patterns of the native and alien woody flora in Kashmir Himalaya, India}, series = {Environmental research}, volume = {111}, journal = {Environmental research}, number = {7}, publisher = {Elsevier}, address = {San Diego}, issn = {0013-9351}, doi = {10.1016/j.envres.2011.05.006}, pages = {967 -- 977}, year = {2011}, abstract = {Background: Many studies have shown that alien species richness pattern follows that of native species richness patterns along environmental gradients, without taking the specific composition of the two groups into account. Objectives: To compare species richness patterns of native and alien woody plants along an altitudinal gradient in Kashmir Himalaya, India, and to analyse the specific composition, e.g. proportion of life forms. Methods: Analysis of secondary data from published floristic inventories. The gradient (500-4800 m asl) was split into 100 m bands and presence/absence data for each species were obtained, for each band. Results: Species richness of both native and alien species followed a hump-shaped distribution. Alien species richness dropped faster above 2000 m asl than the native did. The ratio of trees to shrubs decreased monotonically along the gradient in native species, but showed a peak at c. 2500 m asl in alien species. Alien species flowered in average earlier than native species. Conclusions: The change of species richness of native and alien species along altitude is similar, but the proportion of life forms is not. Most likely both climatic and socio-economic factors affect alien species richness and its specific composition in the Kashmir Himalaya.}, language = {en} } @article{KhurooReshiMaliketal.2012, author = {Khuroo, Anzar A. and Reshi, Zafar A. and Malik, Akhtar H. and Weber, Ewald and Rashid, Irfan and Dar, G. H.}, title = {Alien flora of India taxonomic composition, invasion status and biogeographic affiliations}, series = {Biological invasions : unique international journal uniting scientists in the broad field of biological invasions}, volume = {14}, journal = {Biological invasions : unique international journal uniting scientists in the broad field of biological invasions}, number = {1}, publisher = {Springer}, address = {Dordrecht}, issn = {1387-3547}, doi = {10.1007/s10530-011-9981-2}, pages = {99 -- 113}, year = {2012}, abstract = {The wide knowledge gaps in invasion biology research that exist in the developing world are crucial impediments to the scientific management and global policymaking on biological invasions. In an effort to fill such knowledge gaps, we present here an inventory of the alien flora of India, based on systematic reviews and rigorous analyses of research studies (ca. 190) published over the last 120 years (1890-2010 AD), and updated with field records of the last two decades. Currently, the inventory comprises of 1,599 species, belonging to 842 genera in 161 families, and constitutes 8.5\% of the total Indian vascular flora. The three most species-rich families are Asteraceae (134 spp.), Papilionaceae (114 spp.) and Poaceae (106 spp.), and the three largest genera are Eucalyptus (25 spp.), Ipomoea (22 spp.), and Senna (21 spp.). The majority of these species (812) have no report of escaping from cultivation. Of the remaining subset of 787 species, which have either escaped from intentional cultivation, or spread after unintentional introduction, casuals are represented by 57 spp., casual/naturalised by 114 spp., naturalised by 257 spp., naturalised/invasive by 134 spp., and invasive by 225 spp. Biogeographically, more than one-third (35\%) of the alien flora in India has its native ranges in South America, followed by Asia (21\%), Africa (20\%), Europe (11\%), Australia (8\%), North America (4\%); and cryptogenic (1\%). The inventory is expected to serve as the scientific baseline on plant invasions in India, with implications for conservation of global biodiversity.}, language = {en} } @article{HeinkenWeber2013, author = {Heinken, Thilo and Weber, Ewald}, title = {Consequences of habitat fragmentation for plant species do we know enough?}, series = {Perspectives in plant ecology, evolution and systematics}, volume = {15}, journal = {Perspectives in plant ecology, evolution and systematics}, number = {4}, publisher = {Elsevier}, address = {Jena}, issn = {1433-8319}, doi = {10.1016/j.ppees.2013.05.003}, pages = {205 -- 216}, year = {2013}, abstract = {Habitat fragmentation is one of the most important causes for the decline of plant species. However, plants differing in phylogeny, habitat requirements and biology are likely to respond differently to habitat fragmentation. We ask whether case studies on the effects of habitat fragmentation conducted so far allow generalizations about its effects on the fitness and genetic diversity of populations of endangered plant species. We compared the characteristics of plant species endangered in Germany whose sensitivity to habitat fragmentation had been studied with those of the endangered species that had not been studied. We found strong discrepancies between the two groups with regard to their taxonomy and traits relevant to their sensitivity to habitat fragmentation. Monocots, graminoids, clonal, abiotically pollinated and self compatible species were underrepresented among the studied species, and most study species were from a few habitat types, in particular grasslands. We conclude that our current knowledge of the effects of habitat fragmentation on plant populations is not sufficient to provide widely applicable guidelines for species management. The selection of species studied so far has been biased toward species from certain habitats and species exhibiting traits that probably make them vulnerable to habitat fragmentation. Future studies should include community-wide approaches in different habitats, e.g. re-visitation studies in which the species pool is assessed at different time intervals, and population-biological studies of species from a wide range of habitats, and of different life forms and growth strategies. A more representative picture of the effects of habitat fragmentation would allow a better assessment of threats and more specific recommendations for optimally managing populations of endangered plants.}, language = {en} } @unpublished{CierjacksKowarikJoshietal.2013, author = {Cierjacks, Arne and Kowarik, Ingo and Joshi, Jasmin Radha and Hempel, Stefan and Ristow, Michael and von der Lippe, Moritz and Weber, Ewald}, title = {Biological flora of the british isles: robinia pseudoacacia}, series = {The journal of ecology}, volume = {101}, journal = {The journal of ecology}, number = {6}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0022-0477}, doi = {10.1111/1365-2745.12162}, pages = {1623 -- 1640}, year = {2013}, abstract = {This account presents information on all aspects of the biology of Robinia pseudoacacia L. that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of the British Isles: distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, and history and conservation.Robinia pseudoacacia, false acacia or black locust, is a deciduous, broad-leaved tree native to North America. The medium-sized, fast-growing tree is armed with spines, and extensively suckering. It has become naturalized in grassland, semi-natural woodlands and urban habitats. The tree is common in the south of the British Isles and in many other regions of Europe.Robinia pseudoacacia is a light-demanding pioneer species, which occurs primarily in disturbed sites on fertile to poor soils. The tree does not tolerate wet or compacted soils. In contrast to its native range, where it rapidly colonizes forest gaps and is replaced after 15-30years by more competitive tree species, populations in the secondary range can persist for a longer time, probably due to release from natural enemies.Robinia pseudoacacia reproduces sexually, and asexually by underground runners. Disturbance favours clonal growth and leads to an increase in the number of ramets. Mechanical stem damage and fires also lead to increased clonal recruitment. The tree benefits from di-nitrogen fixation associated with symbiotic rhizobia in root nodules. Estimated symbiotic nitrogen fixation rates range widely from 23 to 300kgha(-1)year(-1). The nitrogen becomes available to other plants mainly by the rapid decay of nitrogen-rich leaves.Robinia pseudoacacia is host to a wide range of fungi both in the native and introduced ranges. Megaherbivores are of minor significance in Europe but browsing by ungulates occurs in the native range. Among insects, the North American black locust gall midge (Obolodiplosis robiniae) is specific to Robinia and is spreading rapidly throughout Europe. In parts of Europe, Robinia pseudoacacia is considered an invasive non-indigenous plant and the tree is controlled. Negative impacts include shading and changes of soil conditions as a result of nitrogen fixation.}, language = {en} } @article{SeebensEsslDawsonetal.2015, author = {Seebens, Hanno and Essl, Franz and Dawson, Wayne and Fuentes, Nicol and Moser, Dietmar and Pergl, Jan and Pysek, Petr and van Kleunen, Mark and Weber, Ewald and Winter, Marten and Blasius, Bernd}, title = {Global trade will accelerate plant invasions in emerging economies under climate change}, series = {Global change biology}, volume = {21}, journal = {Global change biology}, number = {11}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1354-1013}, doi = {10.1111/gcb.13021}, pages = {4128 -- 4140}, year = {2015}, abstract = {Trade plays a key role in the spread of alien species and has arguably contributed to the recent enormous acceleration of biological invasions, thus homogenizing biotas worldwide. Combining data on 60-year trends of bilateral trade, as well as on biodiversity and climate, we modeled the global spread of plant species among 147 countries. The model results were compared with a recently compiled unique global data set on numbers of naturalized alien vascular plant species representing the most comprehensive collection of naturalized plant distributions currently available. The model identifies major source regions, introduction routes, and hot spots of plant invasions that agree well with observed naturalized plant numbers. In contrast to common knowledge, we show that the 'imperialist dogma,' stating that Europe has been a net exporter of naturalized plants since colonial times, does not hold for the past 60 years, when more naturalized plants were being imported to than exported from Europe. Our results highlight that the current distribution of naturalized plants is best predicted by socioeconomic activities 20 years ago. We took advantage of the observed time lag and used trade developments until recent times to predict naturalized plant trajectories for the next two decades. This shows that particularly strong increases in naturalized plant numbers are expected in the next 20 years for emerging economies in megadiverse regions. The interaction with predicted future climate change will increase invasions in northern temperate countries and reduce them in tropical and (sub) tropical regions, yet not by enough to cancel out the trade-related increase.}, language = {en} } @article{HeinzeWernerWeberetal.2015, author = {Heinze, Johannes and Werner, Tony and Weber, Ewald and Rillig, Matthias C. and Joshi, Jasmin Radha}, title = {Soil biota effects on local abundances of three grass species along a land-use gradient}, series = {Oecologia}, volume = {179}, journal = {Oecologia}, number = {1}, publisher = {Springer}, address = {New York}, issn = {0029-8549}, doi = {10.1007/s00442-015-3336-0}, pages = {249 -- 259}, year = {2015}, abstract = {Biotic plant-soil interactions and land-use intensity are known to affect plant individual fitness as well as competitiveness and therefore plant-species abundances in communities. Therefore, a link between soil biota and land-use intensity on local abundance of plant species in grasslands can be expected. In two greenhouse experiments, we investigated the effects of soil biota from grassland sites differing in land-use intensity on three grass species that vary in local abundances along this land-use gradient. We were interested in those soil-biota effects that are associated with land-use intensity, and whether these effects act directly or indirectly. Therefore, we grew the three plant species in two separate experiments as single individuals and in mixtures and compared their performance. As single plants, all three grasses showed a similar performance with and without soil biota. In contrast, in mixtures growth of the species in response to the presence or absence of soil biota differed. This resulted in different soil-biota effects that tend to correspond with patterns of species-specific abundances in the field for two of the three species tested. Our results highlight the importance of indirect interactions between plants and soil microorganisms and suggest that combined effects of soil biota and plant-plant interactions are involved in structuring plant communities. In conclusion, our experiments suggest that soil biota may have the potential to alter effects of plant-plant interactions and therefore influence plant-species abundances and diversity in grasslands.}, language = {en} } @article{CochardEdwardsWeber2015, author = {Cochard, Roland and Edwards, Peter J. and Weber, Ewald}, title = {Post-ranching tree-grass interactions in secondary Acacia zanzibarica woodlands in coastal Tanzania - an experimental study}, series = {Applied vegetation science : official organ of the International Association for Vegetation Science}, volume = {18}, 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/avsc.12134}, pages = {297 -- 310}, year = {2015}, abstract = {Questions: We studied a humid savanna rangeland., abandoned in 2000, where intensive cattle grazing had led to widespread encroachment by Acacia zanzibarica. We asked whether the acacia trees were able to regenerate in the absence of domesJic livestock, either beneath acacia canopies or in artificial clearings. Location: Tropical coastal Tanzania (former Mkwaja Ranch, now in Saadani National Park). Methods: We set out a total of 48 plots on four sites in November 2001, and assigned them to three treatments: trees felled (FN), trees felled and the stumps poisoned (FP) with Triclopyr, and no intervention (controls, NN). We analysed soils of plots for texture and nutrients. In two wet (July 2002 and 2003) and one dry (February 2003) seasons we assessed grass and tree leaf biomass and transpiration rates, and counted acacia seedlings and resprouts. The effects of treatments (controlled for site and other co-variables) on grass growth and acacia rectaiitment were determined statistically using general linear models (GLM). Results: Acacia leaves had a much higher stomatal conductance than grasses, with the consequence that total evapotranspiration in woodland was higher than in clearings. In the wet seasons, grass biomass and seedling densities were significantly higher in clearings than in control plots, which we attributed to more.favourable moisture conditions, In the dry season, by contrast, we found no differences, and all seedlings had died. On FN plots, 71\% of stumps, and on FP plots, 11\% resprouted (coppicing), but only a quarter of these shoots survived until July 2003. Root suckering occurred spontaneously at low densities. No root suckers or resprouts grew beyond the grass layer. Conclusions: Acacia woodlands do not regenerate in the absence of cattle grazing, and tree cutting in combination with appropriate fire management could potentially accelerate re-establishment of open grassland. However, regeneration might occur in the future due to the increasing wildlife populations within the new national park.}, language = {en} }