Responses of baldcypress (Taxodium distichum) seedlings to soil moisture were studied to test the hypothesis that flooding may lead to seedling's higher susceptibility to drought. Treatments included a well-watered but drained control (C), continuously flooded (CF), control followed by drought (CD), and flooded followed by drought (FD). Gas exchange values revealed no significant effects on net photosynthetic rate (PN) in response to flooding. In contrast, after the onset of drought, PN was significantly reduced in CD and FD plants. Significant growth reductions under mild drought conditions indicated that baldcypress seedlings were drought sensitive. However, comparison of gas exchange rates and growth responses between CD and FD plants indicated that prior flooding had no detectable effect on subsequent sensitivity of baldcypress to drought. These findings explain baldcypress persistence in wetland habitats characterized by periodic flooding and mild drought. and J. M. Elcan, S. R. Pezeshki.
The large copper butterfly, Lycaena dispar batavus, a subspecies of much conservation interest, is host-specific to the great water dock, Rumex hydrolapathum, but little is known of the relationship between herbivore and host in wild populations. This study investigated the distribution of both R. hydrolapathum plants and L. d. batavus eggs in four different habitat types within the Weerribben National Park, The Netherlands, during the summer of 1993. As expected, host plant distribution strongly influenced that of its herbivore. Further, both species had significantly aggregated distributions, and that of R. hydrolapathum was in agreement with the negative binomial model. Host plant selection for oviposition showed no significant relationship with physical plant characteristics, such as plant height and the number of leaves, and at the scale studied, habitat type was of only limited influence. The possible influence of the vegetational architecture surrounding host plants is discussed.
a1_The Pantanal is the largest wetland in the world with extremely high plant and animal diversity, but large areas have been invaded by Vochysia divergens Pohl (Vochysiaceae), a tree that is native to the Amazon Basin, and Curatella americana L. (Dilleniaceae), a tree that is native to the Brazilian savanna (cerrado). V. divergens is reportedly floodadapted, thus its ability to invade the Pantanal may not be surprising, but the invasion of C. americana is counterintuitive, because this species is adapted to the
well-drained soils of the cerrado. Thus, we were interested in comparing the photosynthetic capacity, in terms of CO2 conductance, carboxylation, and electron transport of these species over a seasonal flooding cycle. Given that V. divergens is reportedly flood-adapted, we predicted that this species would have a higher photosynthetic capacity than C. americana, especially under flooding. To test this hypothesis we measured the photosynthetic CO2 response (PN/Cc) of V. divergens and C. americana within 1 year to determine, if photosynthetic capacity varied systematically over time and between species. Contrary to our hypothesis, V. divergens did not always have a higher photosynthetic capacity than C. americana. Rather, species differences were influenced by temporal variations in flooding and the leaf age. Leaf CO2 assimilation and photosynthetic capacity of both species were lower during the flood period, but the differences were not statistically significant. The physiological performance of both species was strongly related to leaf N and P concentrations, but P limitation appeared to be more important than N limitation for these species and ecosystem. Photosynthetic capacity was higher and more stable for V. divergens, but such an advantage did not result in a statistically significant increase in PN., a2_Our results suggest that both species are tolerant to flooding even though they are adapted to very different hydrological conditions. Such physiological plasticity, especially for C. americana, might be a key feature for the ability to survive and persist in the seasonally flooded Pantanal., H. J. Dalmagro ... [et al.]., and Obsahuje bibliografii
Půdní vlhkost má velký vliv na biodiverzitu lesní vegetace a extrémní situace jako povodně nebo sucho mohou biodiverzitu významně měnit. K těmto přirozeným faktorům se přidává působení člověka, které v dlouhodobém měřítku vedlo k vysoušení krajiny. Lesní mokřady byly odvodňovány kvůli hospodářským výnosům a teprve v současné době se lesní mokřady postupně snažíme obnovovat., Soil moisture has a strong influence on the biodiversity of forest vegetation. Extreme situations such as flooding or drought can significantly change biodiversity. In addition to these natural factors, the human impact has led to long-term desiccation on the landscape scale. Forest wetlands were drained to promote management production. Only recently can efforts to restore forest wetlands be observed., and Radim Hédl.
Species richness and above-ground biomass of vascular plants and bryophytes of poor acidic fens (the Sphagno recurvi-Caricion canescentis alliance), rich Sphagnum fens (the Caricion fuscae and Sphagno warnstorfii-Tomenthypnion alliances) and calcareous spring fens (the Caricion davallianae alliance including tufa-forming spring fens) were studied. The study area was in the western parts of the Outer Carpathians in the border region of the Czech and Slovak Republics. The numbers of species were recorded in plots ranging from 0.00196 to 16m2 and correlated with chemical factors and above-ground biomass. The chemical properties of springwater (mainly pH, conductivity, Ca2+, Mg2+) were the main factors influencing the species richness of vascular plants. Tufa-forming calcareous fen communities (Carici flavae-Cratoneuretum) had the highest species richness of vascular plants. In contrast, the highest species richness of bryophytes occurred at pHneutral sites, in peat forming calcareous fen communities (Valeriano-Caricetum flavae) and in those with Sphagnum warnstorfii and S. teres. Bryophyte species richness of small plots was correlated with the iron concentration in the springwater. The differences in species richness of calcareous fens were related to the mowing regime. Litter mass had a negative effect on the species richness of vascular plants. Mosses responded to high amounts of litter or vascular plant biomass by a significant decrease in biomass. Two types of Sphagnum fens: (a) strongly dominated by Sphagnum flexuosum or S. palustre (rich in phosphates) and (b) polydominant (poor in phosphates), were also compared. In the former, the slope of the regression for the dependence of bryophyte species richness on plot size was less steep.
Vlha pestrá (Merops apiaster) je teplomilný ptačí druh uzpůsobený k lovu hmyzu. Proto patří k obyvatelům převážně subtropických a tropických oblastí, ale v opakovaných vlnách osídlovala i různá místa střední Evropy. Postupná expanze druhu probíhá i v České republice. Článek popisuje možnosti podpory hnízdění vlhy pestré na příkladu mokřadu Betlém na jižní Moravě., Merops apiaster is a termophilic insectivorous bird species. Hence it primarily inhabits subtropical and tropical regions, but it has also repeatedly settled in various Central European sites. The species is also gradually expanding in the Czech Republic. This article describes the possibility of supporting bee-eater nesting based on the example of the Betlém wetlands in southern Moravia., and Miroslav Šebela.