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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. Source


Zang C.,TU Munich | Pretzsch H.,TU Munich | Rothe A.,Weihenstephan-Triesdorf University of Applied Sciences
Trees - Structure and Function | Year: 2012

In this study, we provide a detailed analysis of tree growth and water status in relation to climate of three major species of forest trees in lower regions of Bavaria, Southern Germany: Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and common oak (Quercus robur). Tree-ring chronologies and latewood δ 13C were used to derive measures for drought reaction across trees of different dimensions: growth reduction associated with drought years, long-term growth/climate relations and stomatal control on photosynthesis. For Scots pine, growth/climate relations indicated a stronger limitation of radial growth by high summer temperatures and low summer precipitation in smaller trees in contrast to larger trees. This is corroborated by a stronger stomatal control on photosynthesis for smaller pine trees under average conditions. In dry years, however, larger pine trees exhibited stronger growth reductions. For Norway spruce, a significantly stronger correlation of tree-ring width with summer temperatures and summer precipitation was found for larger trees. Additionally, for Norway spruce there is evidence for a change in competition mode from size-asymmetric competition under conditions with sufficient soil water supply to a more size-symmetric competition under dry conditions. Smaller oak trees showed a weaker stomatal control on photosynthesis under both dry and average conditions, which is also reflected by a significantly faster recovery of tree-ring growth after extreme drought events in smaller oak trees. The observed patterns are discussed in the context of the limitation-caused matter partitioning hypothesis and possible species-specific ontogenetic modifications. © 2011 Springer-Verlag. Source


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. Source


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. Source


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. Source

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