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Somodi I.,Hungarian Academy of Sciences | Molnar Z.,Hungarian Academy of Sciences | Ewald J.,Weihenstephan-Triesdorf University of Applied Sciences
Journal of Vegetation Science | Year: 2012

In this paper, the concerns of Chiarucci et al. regarding use of the potential natural vegetation (PNV) concept are addressed, as voiced in the forum section of the Journal of Vegetation Science. First, we rectify some unfounded expectations concerning PNV, including a relationship with prehuman vegetation and phytosociology. Second, we point out issues that pose considerable challenges in PNV and require common agreement. Here, we address the issue of time and disturbance. We propose to use the static PNV concept as a baseline, a null model for landscape assessment and in comparisons. Instead of changing the PNV concept itself, we introduce a new term, potential future natural vegetation (PFV) to cover estimations of potential successional outcomes. Finally, we offer a new view of PNV with which we intend to make the use of PNV estimates more transparent. We formalize the PNV theory into a partial cause-effect model of vegetation that clearly states which effects on vegetation are factored out during its estimation. Further, we also propose to assess PNV in a probabilistic setting, rather than providing a single estimate for one location. This multiple PNV would reflect our uncertainty about the vegetation entity that could persist at the locality concerned. Such uncertainty arises from the overlap of environmental preferences of different mature vegetation types. Thus reformulated, we argue that the PNV concept has much to offer as a null model, especially in landscape ecology and in site comparisons in space and time. © 2012 International Association for Vegetation Science.

Zahner V.,Weihenstephan-Triesdorf University of Applied Sciences | Sikora L.,Bureau of Dendroavifaunistik | Pasinelli G.,Swiss Ornithological Institute
Forest Ecology and Management | Year: 2012

Cavity nesting birds invest considerable time and effort into the construction of nests. The investment can be particularly high for species such as the black woodpecker (Dryocopus martius) that selects living trees as nest substrates. However, the investment may be reduced if fungal rot is present to help soften the wood. We used Resistograph drills to objectively assess fungal decay and tested whether black woodpeckers preferred trees with heart rot as sites for cavity starts. In doing so we also examined the distribution of fungal decay across the tree radius, analysed location of cavity starts with respect to proximity to heart rot, and evaluated wood condition at fresh and old cavity starts. Heart rot was significantly more common in beeches (Fagus sylvatica) with cavity starts than in random reference beeches. Fungal decay was not evenly distributed across the tree radius, but was more prevalent both in the central and outer thirds than in the middle third. Distance to heart rot was smaller from cavity starts than from random drills, suggesting a preference to initiate cavities close to heart rot. Wood density at fresh cavity starts was significantly higher than at old cavity starts. Collectively, these findings imply that black woodpeckers prefer to excavate cavity starts in beeches with heart rot, which the woodpeckers can detect based on cues unavailable to humans. The decay is reducing the energy expenditure of the black woodpecker and is a part of the long time excavation strategy. The cavity starts are an important factor in the process of excavating the large black woodpecker cavities in beech that enhance biodiversity in managed forests. Future studies should attempt to uncover the mechanisms woodpeckers use in selecting the locations of cavity starts. © 2012 Elsevier B.V.

Millard B.L.,Harvard University | Niepel M.,Harvard University | Menden M.P.,Harvard University | Menden M.P.,Weihenstephan-Triesdorf University of Applied Sciences | And 3 more authors.
Nature Methods | Year: 2011

Whereas genomic data are universally machine-readable, data from imaging, multiplex biochemistry, flow cytometry and other cell- and tissue-based assays usually reside in loosely organized files of poorly documented provenance. This arises because the relational databases used in genomic research are difficult to adapt to rapidly evolving experimental designs, data formats and analytic algorithms. Here we describe an adaptive approach to managing experimental data based on semantically typed data hypercubes (SDCubes) that combine hierarchical data format 5 (HDF5) and extensible markup language (XML) file types. We demonstrate the application of SDCube-based storage using ImageRail, a software package for high-throughput microscopy. Experimental design and its day-to-day evolution, not rigid standards, determine how ImageRail data are organized in SDCubes. We applied ImageRail to collect and analyze drug dose-response landscapes in human cell lines at single-cell resolution. © 2011 Nature America, Inc. All rights reserved.

Franz C.,TU Dresden | Makeschin F.,TU Dresden | Weiss H.,Helmholtz Center for Environmental Research | Lorz C.,Weihenstephan-Triesdorf University of Applied Sciences
Science of the Total Environment | Year: 2014

The development of effective sediment management strategies is a key requirement in tropical areas with fast urban development, like Brasilia DF, Brazil, because of the limited resources available. Accurate identification and management of sediment sources areas, however, is hampered by the dearth of reliable information on the primary sources of sediment. Few studies have attempted to quantify the source of sediment within fast urbanizing, mixed used, tropical catchments. In this study, statistically verified composite fingerprints and a multivariate mixing model have been used to identify the main land use specific sources of sediment deposited in the artificial Lago Paranoá, Central Brazil. Because of the variability of urban land use types within the Lago Paranoá sub-catchments, the fingerprinting approach was additionally undertaking for the Riacho Fundo sub-catchment. The main contributions from individual source types (i.e. surface materials from residential areas, constructions sites, road deposited sediment, cultivated areas, pasture, farm tracks, woodland and natural gullies) varied between the whole catchment and the Riacho Fundo sub-catchment, reflecting the different proportions of land uses. The sediments deposited in the silting zones of the Lago Paranoá originate largely from urban sources (85. ±. 4%). Areas with (semi-) natural vegetation and natural gullies contribute 10. ±. 2% of the sediment yield. Agricultural sites have only a minor sediment contribution of about 5. ±. 4% within the whole catchment. Within the Riacho Fundo sub-catchment there is a significant contribution from urban (53. ±. 4%) source, such as residential areas with semi-detached housings (42. ±. 3%) with unpaved roads (12. ±. 3%) and construction sites (20. ±. 3%) and agricultural areas (31. ±. 2%). The relative contribution from land use specific sources to the sediment deposition in the silting zone of the Lago Paranoá demonstrated that most of the sediment is derived from sites with high anthropogenic impact. © 2013 Elsevier B.V.

Eckhardt K.,Weihenstephan-Triesdorf University of Applied Sciences
Hydrology and Earth System Sciences | Year: 2012

A sensitivity analysis for a well-established baseflow separation technique, a two parameter recursive digital filter, is presented. The sensitivity of the calculated baseflow index to errors or uncertainties of the two filter parameters and of the initial baseflow value is analytically ascertained. It is found that the influence of the initial baseflow value is negligible for long time series. The propagation of errors or uncertainties of the two filter parameters into the baseflow index is expressed by a dimensionless sensitivity index, the ratio between the relative error of the baseflow index and the relative error of the respective parameter. Representative index values are derived by application of the resulting equations to 65 North American catchments. In the mean the parameter a, the recession constant, has a stronger influence on the calculated baseflow index than the second filter parameter BFImax. This is favourable in that a can be determined by a recession analysis and therefore should be less uncertain. Whether this finding also applies for a specific catchment can easily be checked by means of the derived equations. © Author(s) 2012.

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