@article{HornHempelRistowetal.2015,
  author    = {Horn, Sebastian and Hempel, Stefan and Ristow, Michael and Rillig, Matthias C. and Kowarik, Ingo and Caruso, Tancredi},
  title     = {Plant community assembly at small scales: Spatial vs. environmental factors in a European grassland},
  series = {Acta oecologica : international journal of ecology},
  volume    = {63},
  journal   = {Acta oecologica : international journal of ecology},
  publisher = {Elsevier},
  address   = {Paris},
  issn      = {1146-609X},
  doi       = {10.1016/j.actao.2015.01.004},
  pages     = {56 -- 62},
  year      = {2015},
  abstract  = {Dispersal limitation and environmental conditions are crucial drivers of plant species distribution and establishment. As these factors operate at different spatial scales, we asked: Do the environmental factors known to determine community assembly at broad scales operate at fine scales (few meters)? How much do these factors account for community variation at fine scales? In which way do biotic and abiotic interactions drive changes in species composition? We surveyed the plant community within a dry grassland along a very steep gradient of soil characteristics like pH and nutrients. We used a spatially explicit sampling design, based on three replicated macroplots of 15 x 15, 12 x 12 and 12 x 12 m in extent. Soil samples were taken to quantify several soil properties (carbon, nitrogen, plant available phosphorus, pH, water content and dehydrogenase activity as a proxy for overall microbial activity). We performed variance partitioning to assess the effect of these variables on plant composition and statistically controlled for spatial autocorrelation via eigenvector mapping. We also applied null model analysis to test for non-random patterns in species co-occurrence using randomization schemes that account for patterns expected under species interactions. At a fine spatial scale, environmental factors explained 18\% of variation when controlling for spatial autocorrelation in the distribution of plant species, whereas purely spatial processes accounted for 14\% variation. Null model analysis showed that species spatially segregated in a non-random way and these spatial patterns could be due to a combination of environmental filtering and biotic interactions. Our grassland study suggests that environmental factors found to be directly relevant in broad scale studies are present also at small scales, but are supplemented by spatial processes and more direct interactions like competition. (C) 2015 Elsevier Masson SAS. All rights reserved.},
  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}
}