11 research outputs found
Ragweed as an Example of Worldwide Allergen Expansion
<p/> <p>Multiple factors are contributing to the expansion of ragweed on a worldwide scale. This review seeks to examine factors that may contribute to allergen expansion with reference to ragweed as a well-studied example. It is our hope that increased surveillance for new pollens in areas not previously affected and awareness of the influence the changing environment plays in allergic disease will lead to better outcomes in susceptible patients.</p
Oak (Quercus spp.) response to climate differs more among sites than among species in central Czech Republic
Climatic parameters are the main environmental factors affecting tree growth. The main aim of
the presented study was to determine whether different oak species growing under contrasting environmental
conditions show different sensitivity to climatic parameters. Four oak stands with Quercus robur,
Quercus petraea, Quercus polycarpa and Quercus dalechampii growing in the same area were evaluated. Standard
dendrochronological methods were used for sample preparation, ring width measurements, cross-dating,
chronology development, and the assessment of growth-climate response patterns. Although the species
grew under different environmental conditions, their local tree-ring chronologies are highly correlated. The
radial growth responses to climatic parameters differ slightly, but the response depends more on local site
conditions than on the oak species. At the same time, the strongest correlations between radial growth and
climatic parameters were identical among species and sites. The amount of water available in the soil was
the main climate-dependent factor limiting radial growth. Approximately since the 1990s, the distribution
of rainfalls within the growing season has changed at the expense of spring precipitation. The significance
of relative soil moisture content during spring for oak growth increased and the significance of summer
values decreased
Distribution of Invasive Species of Ambrosia L. Genus in the South Urals (Republic of Bashkortostan)
A new scenario for the Quaternary history of European beech populations: palaeobotanical evidence and genetic consequences
Here, palaeobotanical and genetic data for common beech (Fagus sylvatica) in Europe are used to evaluate the genetic consequences of long-term survival in refuge areas and postglacial spread. Four large datasets are presented, including over 400 fossil-pollen sites, 80 plant-macrofossil sites, and 450 and 600 modern beech populations for chloroplast and nuclear markers, respectively. The largely complementary palaeobotanical and genetic data indicate that: (i) beech survived the last glacial period in multiple refuge areas; (ii) the central European refugia were separated from the Mediterranean refugia; (iii) the Mediterranean refuges did not contribute to the colonization of central and northern Europe; (iv) some populations expanded considerably during the postglacial period, while others experienced only a limited expansion; (v) the mountain chains were not geographical barriers for beech but rather facilitated its diffusion; and (vi) the modern genetic diversity was shaped over multiple glacial-interglacial cycles. This scenario differs from many recent treatments of tree phylogeography in Europe that largely focus on the last ice age and the postglacial period to interpret genetic structure and argue that the southern peninsulas (Iberian, Italian and Balkan) were the main source areas for trees in central and northern Europ