Uptake of NH
inf4sup+
-N by streambed biota of mountain brooks was studied in the alpine zone of the High Tatra Mountains. Experiments were performed involving in situ dosing of ammonium directly to the acidified stream and incubations of ammonium and streambed bryophytes in enclosures within a range of pH from 4.45 to 8.10.NH
inf4sup+
-N uptake length decreased with decreasing stream discharge, while comparable values of discharge-normalized uptake lengths were found during two in situ experiments.Maximum uptake rates of NH
inf4sup+
-N obtained during the incubation of bryophytes (6 to 11 mg m–2 h–1) were comparable with results of two in situ experiments (8 and 12 mg m–2 h–1). The average NH
inf4sup+
-N uptake rates observed during incubations lasting 3 to 5 hours (4.3 mg m–2 h–1) were not related to the pH of stream water. Nitrification of about 50% of the NH
inf4sup+
-N added was observed in non-acidified streams, but was negligible in acidified streams. Significant photoinhibition of nitrification was observed in non-acidified streams during enclosure experiments. 相似文献
Bei den jüngsten Ausgrabungen am hallstattzeitlichen Fürstengrabhügel Magdalenenberg bei Villingen wurden vorzüglich erhaltene und autochthone Pflanzenreste geborgen, darunter 30 Arten von Bryophyten. Diese ließen sich folgenden rezenten ökologischsoziologischen Gruppen zuordnen: Halbtrockenrasen-Arten, Arten verdichteter Erdblößen, Waldboden-Bewohner, Arten frischer bis nasser Standorte, Euryöke. Durch aktualistischen Vergleich der Moos-Synusien mit heutigen Pflanzengesellschaften im gleichen Naturraum ließ sich entschlüsseln, daß das Gelände damals mit extensiv beweideten Halbtrockenrasen bewachsen war; die Tätigkeit der Hügelbauer spiegelt sich in einer Überlagerung mit “Ruderalmoosen” wider. Durch Samenpflanzen-Funde konnte die Rekonstruktion weiter präzisiert und abgesichert werden. 相似文献
Xylans are known to be major cellulose-linking polysaccharides in secondary cell walls in higher plants. We used two monoclonal antibodies (LM10 and LM11) for a comparative immunocytochemical analysis of tissue and cell distribution of xylans in a number of taxa representative of all major tracheophyte and bryophyte lineages. The results show that xylans containing the epitopes recognized by LM10 and LM11 are ubiquitous components of secondary cell walls in vascular and mechanical tissues in all present-living tracheophytes. In contrast, among the three bryophyte lineages, LM11 binding was detected in specific cell-wall layers in pseudoelaters and spores in the sporophyte of hornworts, while no binding was observed with either antibody in the gametophyte or sporophyte of liverworts and mosses. The ubiquitous occurrence of xylans containing LM10 and LM11 epitopes in tracheophytes suggests that the appearance of these polysaccharides has been a pivotal event for the evolution of highly efficient vascular and mechanical tissues. LM11 binding in the sporophyte of hornworts, indicating the presence of relatively highly substituted xylans (possibly arabinoxylans), separates these from the other bryophytes and is consistent with recent molecular data indicating a sister relationship of the hornworts with tracheophytes. 相似文献
Abstract. The purpose of this study is to evaluate and to quantify the influence of management on the epiphytic species composition in Danish Fagus sylvatica forests. Trunks were chosen at random within selected blocks in both managed and unmanaged Fagus stands.117 trunks in 43 sample plots in three forests were investigated. Cover was estimated for 72 lichens, 29 bryophytes and two fungi on vertical trunks 0.3 ‐2 m above ground. 18 explanatory variables were recorded and arranged in three groups: eight management‐related variables, six micro‐climatic‐ and soil variables, and four geographical‐ and geological variables. Canonical Correspondence Analysis was used to test and to quantify the explaining power of the three groups of variables applying the variation partitioning approach. Detrended Correspondence Analysis was used to evaluate whether important gradients were ignored. It was concluded that the traditional ‘shelterwood uniform system’ used in Fagus forests has a marked influence on the epiphytic species composition. Thus, management‐related variables explained more than one third of the total variation explained, which equals 10.9% of the total variation. Microclimatic and soil variables explained 9.0%, and geographical and geological variables explained 6.0%. The following three recommendations are suggested to reduce the significant influence of management on the epiphytic species composition. First, it should be attempted to ensure a continuous occurrence of some big trees per ha to be left for natural death and decomposition. Second, regular thinning is necessary, especially in the first part of rotation. Third, a multi‐layered forest, where wind and desiccation effects are minimized, is recommended. 相似文献
Oviposition habits of a univoltine mammalophilic blackfly, Prosimulium kiotoense Shiraki, were investigated at a stream in Kyushu Island, Japan. The flies oviposited on bryophyte mosses growing on river bank rock surfaces. The eggs were laid singly, but large irregular egg masses were often formed because many females oviposited within the same small areas. Wet sites with dense bryophyte cover at heights between 0 and 15 cm above water level were selected for oviposition. Oviposition activity was observed in the latter half of April. P. kioteonse females came to the site to lay eggs after 11.00 hours in the morning, when air temperature rose to about 15 degrees C. Peak ovipositional activity occurred between 12.00 and 14.00 hours. 相似文献
Background: Liverwort heath is considered in Scotland to be one of the vegetation types most vulnerable to environmental change, yet detailed insights into its dynamics are lacking.
Aims: To assess the nature and extent of plant compositional changes in liverwort heath over 50 years and relate this to environmental change drivers.
Methods: Vegetation plots previously recorded 20 and 50 years ago were re-surveyed to assess changes in species composition, plot-level species richness and between-plot variability, using several β-diversity indices and partitioning. The environmental indicator values of the species that showed most change were used to identify the environmental drivers of change.
Results: Liverwort heath in north-west Scotland has undergone compositional changes over 50 years, becoming more heterogeneous, and losing some of its distinct character. Dwarf shrubs and specialist liverworts have decreased, while graminoids have increased. Partitioning of change in β diversity indicated that mainly changes in species richness, rather than species turnover, have driven the taxonomic differentiation over time. Grazing, eutrophication and warmer and drier conditions were found to be potentially important drivers of the observed vegetation change.
Conclusions: Our results highlight the vulnerability of liverwort heath to environmental change. 相似文献
In this study, the urban bryophyte flora of the city of Cologne (W. Germany) was studied. A total of 143 bryophyte taxa (17 hepatics and 126 mosses) were recorded within the metropolitan area of Cologne. Three species were newly recorded for North Rhine‐Westphalia: Hannediella heimii, Schistidium helveticum and Tortula schimperi. Thirteen species red‐listed in NRW were recorded, among them hardly endangered: Bryum intermedium and Syntrichia laevipila and extinction endangered: Syntrichia papillosa. The temperate biogeographic element prevails among Cologne bryophytes. According to frequency of recordance, only 11 species are widespread over the urban area of which three are hepatics. 相似文献