Fire and gap dynamics over 300 years in an old-growth temperate forest

Questions What are the long-term patterns of wildfire occurrence and gap dynamics in an old-growth deciduous forest? Are there temporal patterns in fire and gap dynamics over the last ca. 300 yrs? How is drought related to fire occurrence? Are there temporal interactions between gap dynamics and fire? Location Lilley Cornett Woods Appalachian Research Station, Southeastern Kentucky, USA. LCW; 37°05′ N, 83°00′ W. Methods We cross-dated and analysed annually-resolved tree-ring data from 35 tree cross-sections in an old-growth deciduous forest to reconstruct historical fire and canopy disturbance and explore connections among these processes. Canopy disturbance patterns as indicated by tree growth release within this collection [fire history collection: (FHC)] were compared to cores from 26 trees collected in 1983 for the purposes of climate reconstruction [climate collection: (CC)]. Results Initiation dates in the FHC ranged from ca. 1670 to 1925. Thirty-three fire scars were identified from 1678 to 1956. The mean interval between fire events was 9.3 yrs, and there were many more fires after 1800 than before that date. Gap dynamics, as reconstructed through growth release detection, were relatively constant through the FHC record and were supported by a similar result in the CC. The mean number of years between detected release events was 5.2 yrs. Many individual trees, and the mean growth chronology for the FHC, indicate that many oak trees exhibit growth release after long periods of suppression and, after a final release, exhibit a step-change in growth rate suggesting canopy accession. Conclusions Fire and gap dynamics occurred through much of the last ca. 350 yrs in this old-growth forest. There was not evidence to support that these two processes were temporally linked – gap dynamics were ostensibly independent of fire occurrence. Even so, we posit that these two processes may have a synergistic effect on long-term dynamics, wherein fire ‘filters’ the seedling pool and gap openings provide canopy accession opportunities. We also note several instances where release events are associated with stand-wide growth increases suggesting large-scale canopy accession. These events could influence the overstorey composition of the forest for centuries

Differential induction of interferon stimulated genes between type I and type III interferons is independent of interferon receptor abundance.

It is currently believed that type I and III interferons (IFNs) have redundant functions. However, the preferential distribution of type III IFN receptor on epithelial cells suggests functional differences at epithelial surfaces. Here, using human intestinal epithelial cells we could show that although both type I and type III IFNs confer an antiviral state to the cells, they do so with distinct kinetics. Type I IFN signaling is characterized by an acute strong induction of interferon stimulated genes (ISGs) and confers fast antiviral protection. On the contrary, the slow acting type III IFN mediated antiviral protection is characterized by a weaker induction of ISGs in a delayed manner compared to type I IFN. Moreover, while transcript profiling revealed that both IFNs induced a similar set of ISGs, their temporal expression strictly depended on the IFNs, thereby leading to unique antiviral environments. Using a combination of data-driven mathematical modeling and experimental validation, we addressed the molecular reason for this differential kinetic of ISG expression. We could demonstrate that these kinetic differences are intrinsic to each signaling pathway and not due to different expression levels of the corresponding IFN receptors. We report that type III IFN is specifically tailored to act in specific cell types not only due to the restriction of its receptor but also by providing target cells with a distinct antiviral environment compared to type I IFN. We propose that this specific environment is key at surfaces that are often challenged with the extracellular environment

In Situ Hybridization and Reverse Transcription-Polymerase Chain Reaction Studies on the Expression of the GABAc Receptor ?1- and ?2-subunit Genes in Avian and Rat Brain

The pharmacological properties of homo-oligomeric channels formed by the GABA type A receptor-like ?l and ?2 polypeptides are very reminiscent of those of the GABA type C receptors that have been extensively characterized in the retina. Similar receptors have been reported to occur in certain brain regions of a variety of vertebrate species. We have used in situ hybridization to investigate the expression patterns of the ?1- and ? -polypeptide genes in the brain of the 1-day-old chick (Gallus domesticus) and the adult rat (Rattus norvegicus). Our results show that in the chick both the ?1- and ?2-subunit transcripts are present in the cerebellum, the optic tectum, the epithalamus and the nucleus pretectalis. However, the two messenger RNAs are often found in different populations of cells. Thus, only the ?1-subunit gene is expressed in the deep cerebellar nuclei, the dorsal thalamus, the ectostriatum and the tractus vestibulomesencephalicus, while only the ?2-subunit gene is transcribed in the nucleus habenularis lateralis and the nucleus isthmo-opticus. In contrast, neither of the ?-polypeptide messenger RNAs can be detected by in situ hybridization in the rat central nervous system. Reverse transcription-polymerase chain reaction amplification has been used to confirm the expression of the two ?-subunit genes in the chicken brain. Surprisingly, this highly sensitive technique also revealed transcription of these genes in the rat brain. We conclude that the ?l- and ?2-subunit genes are expressed at a much higher level in the avian brain than in the rat brain and that, at least in birds, subtypes of the GABC receptor exist

a comparison between 2004 and 2005 for a specific search in the field of biotechnology

Aim of this work was the analysis of the changes occurring in hit lists of selected search engines at two different points of time.The same search query was applied to the search engine Google and to the science search engine Scirus in August 2004 and in April 2005. The first 40 hits of each search have been analysed on the basis of predefined qualitative and quantitative parameters. Further an analysis of overlapping between search hits at the above mentioned time points has been carried out for each search engine separately.The results of this study has shown on one hand the existence of positive trends in the result lists of both search engines (less dead links, a higher precision in results) and on the other hand the role played by search engines themselves in the dynamic of result lists. The method applied here has shown to be useful for describing and measuring trends and changes in the search results of search engines over a time span.Das Ziel dieser Arbeit war die Identifizierung und Quantifizierung der Veränderungen in den Suchergebnissen aus ausgewählten Suchmaschinen im Jahresabstand.Eine Recherche mit der gleichen Suchabfrage ist mit der allgemeinen Suchmaschine Google und mit der wissenschaftlichen Suchmaschine Scirus im August 2004 und April 2005 durchgeführt worden. Die ersten 40 Treffer sind nach vordefinierten qualitativen und quantitativen Parametern analysiert worden. Weiters ist die Überlappung der Suchergebnissen für die oben genannten Abfragezeitpunkte je nach Suchmaschine getrennt bewertet worden.Die aus dieser Studie resultierenden Ergebnisse zeigen einerseits die Existenz von positiven Tendenzen in den Ergebnislisten der untersuchten Suchmaschinen (Verbesserungen in der Relevanz der Treffer, eine Verringerung der Anzahl an nicht abrufbaren Links, sowie ein Zuwachs an erzielter Information) und andererseits die Rolle der Websuchinstrumente selbst hinsichtlich den Veränderungen von Suchergebnissen bei einer Recherche im Web