The effect of an early-season short-term heat pulse on plant recruitment in the Arctic

Climate change will cause large-scale plant migration. Seedling recruitment constitutes a bottleneck in the migration process but is itself climate-dependent. We tested the effect of warming on early establishment of three Arctic pioneer species, while holding other environmental variables constant. Seeds and bulbils were sown in artificial gaps in dry Arctic tundra and subjected to a 13-day heating of the soil surface by 2–8°C, simulating temperature increases ranging from the general summer warming to heat waves projected to occur more frequently with global warming. All species showed decreased establishment with increasing soil surface temperature. The short-term heat pulse decreased establishment of Polygonum viviparum and Saxifraga cernua, whereas establishment of Cerastium alpinum decreased with temperature due to more permanent natural variation in micro-climate. The treatment effects increased by the quadrat of the temperature increase. Warming and in particular heat waves may result in declining establishment of Arctic plants in dry tundra regions. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Are soil biota buffered against climatic extremes? An experimental test on testate amoebae in arctic tundra (Qeqertarsuaq,West Greenland)

Climate warming is likely to have pronounced impacts on soil biota in arctic ecosystems. In a warmer climate, heatwaves are more frequent and intense, but it is unclear to what extent soil communities are buffered against this. We studied the effects of an artificially induced heatwave on the structure of testate amoebae communities in dry heath tundra in Qeqertarsuaq (Disko Island, West Greenland) during the summer of 2003. While the heatwave was severe enough to induce significant leaf mortality in the aboveground vegetation, overall testate amoebae abundance did not react to the difference in temperature. However, in the heated plots transient shifts in species populations occurred during the exposure, followed by increases in species richness weeks after the heatwave had ended. The most important taxa appearing after the heating period belonged to bacterivorous genera, in agreement with a transient peak in bacterial colony forming units, caused by the heatwave. Lobose testate amoebae resisted the heating and its associated desiccation better than their filose counterparts.     

Altered response to nitrogen supply of mixed grassland communities in a future climate: a controlled environment microcosm study

Few studies have investigated whether responses to nutrient supply of mixed plant communities change under combined elevated CO₂ and climate warming. In this study we analyzed the response of constructed temperate grassland communities to five levels of nitrogen (N) supply, ranging from 0 to 150 kg N ha^?1, under two climate scenarios. Biomass of the plant communities responded positively to N supply in the current climate, but was insensitive to N supply in the future climate. This altered response was not the result of a changing response from a single species, but all species seemed to contribute to it. The weaker response in the future climate was caused by changes in N uptake rather than by changes in nitrogen use efficiency, as community N stocks showed the same response pattern as community biomass. Climate change apparently modified the relation between fertilizer N addition and plant available N.     

Biosystematic studies of the Rumex acetosella complex V. Cytogeography and morphology in the Czech Socialistic Republic and a part of Lower Austria (Austria)

A cytogeographical and morphological (fruit-types and leaf-shape) study of the crítícal Rumex acetosella aggregate has been made on the basis of 38 population samples, for the most part from the Czech Socialistic Republic. In the genecological respect the populations from Bohemia and those from North and West Moravia fit into the pattern earlier found in West and Central Europe (i.e. they are 6x, mainly angiocarpous, and have non-dissected leaf lobes). Samples from the xerothermic region of South Moravia and parts of Slovakia and adjacent Austria are thought to be related to the Balkan population group (mainly 4x, gymnocarpous and with much dissected—multifid—leaf lobes). Evidence of introgressíve hybridisation from the 4x into the 6x ploidy-level has been found in the region of the well known migration route through the Moravian Gate.     

Intrauterine insemination (IUI) as a first-line treatment in developing countries and methodological aspects that might influence IUI success

⁴ Correspondence address. E-mail: willem.ombelet{at}telenet.be It is generally accepted that intrauterine insemination (IUI)should be preferred to more invasive and expensive techniquesof assisted reproduction and be offered as a first-choice treatmentin cases of unexplained and moderate male factor subfertility.Scientific validation of this strategy is rather difficult becauseliterature is rather confusing and not conclusive. IUI is proveneasier to perform, less invasive and less expensive than othermethods of assisted reproduction. Effectivity has been documentedin controlled studies under the condition that the inseminatingmotile count exceeds more than 1 million motile spermatozoa.Risks are minimal, provided the multiple gestation incidencecan be reduced to an acceptable level and provided at leastone tube is patent. Therefore, in developing countries, reflectionon the implementation and use of IUI as a first-line treatmentfor most cases of non-tubal infertility seems mandatory. Thecosts are minimal, training is easy, quality control possibleand severe complications are almost non-existing. In cases ofunexplained infertility or combined male subfertility and ovulatorydysfunction, correction and/or ovarian stimulation with clomiphenecitrate (CC) is probably the best strategy from a cost–benefitpoint of view unless CC-resistancy has been proven in whichthe use of low-dose gonadotrophins is necessary.