Coldest places on earth with angiosperm plant life

The highest elevation flowering plant ever recorded in Europe, a lush moss flora, one of the coldest places of permanent animal life (collembola, mites) and indications of mycorrhizal fungi were evidenced for the Dom summit (4,545m, central Swiss Alps) between solid siliceous rock at 4,505-4,543m, 46°N. Cushions of Saxifraga oppositifolia were found at 4,505 to 4,507m a.s.l. A large individual (possibly >30years old) was in full bloom on 12 August 2009. The 14C-dated oldest debris of the biggest moss, Tortula ruralis, suggests a 13year litter turnover. The thermal conditions at this outpost of plant life were assessed with a miniature data logger. The 2008/09 growing season had 66days with a daily mean rooting zone temperature >0°C in this high elevation micro-habitat (2-3cm below ground). The degree hours >0°C during this period summed up to 4,277°h corresponding to 178°d (degree days), the absolute winter minimum was −20.9°C and the absolute summer maximum 18.1°C. The mean temperature for the growing period was +2.6°C. All plant parts, including roots, experience temperatures below 0°C every night, even during the warmest part of the year. On clear summer days, plants may be physiologically active for several hours, and minimum night temperatures are clearly above the freezing tolerance of Saxifraga oppositifolia in the active state. In comparison with climate data for other extreme plant habitats in the Alps, Himalayas, in the Arctic and Antarctic, these data illustrate the life conditions at what is possibly the coldest place for angiosperm plant life on eart

Treelines Will be Understood Once the Functional Difference Between a Tree and a Shrub Is

Trees are taller than shrubs, grasses, and herbs. What is the disadvantage of being tall so that trees are restricted to warmer regions than low stature life forms? This article offers a brief review of the current state of biological treeline theory, and then explores the significance of tallness from a carbon balance, freezing resistance, and microclimatological perspective. It will be argued that having of a woody stem is neither a burden to the carbon balance nor does it add to the risk of freezing damage. The physiological means of trees to thrive in cold climates are similar to small stature plants, but due to their size, and, thus, closer aerodynamic coupling to air circulation, trees experience critically low temperatures at lower elevation and latitude than smaller plants. Hence, trees reach a limit at treeline for physical reasons related to their statur

Leaf turnover and herbivory in the tall tussock grass Festuca orthophylla in the Andean Altiplano

Tall grass tussocks dominate the Andean highlands above 3,800m a.s.l., with often no other life form contributing significantly to standing crop biomass and productivity, thus, representing the dominant source of fodder for camelid grazing. To assess the productivity of these semi-arid tropical rangelands (350mm of annual rainfall confined to a 4-5months rainy season) is challenging, given the ‘evergreen' nature of leaves and the unknown periodicity of leaf growth. The aim of this study was to explore the seasonal course of new foliage formation, foliage duration, and the response of leaf elongation and emergence to simulated llama grazing (clipping). The repeated census of Festuca orthophylla leaves in the Sajama National Park at 4,250m elevation (Bolivia) provided clear evidence that leaf production is not confined to the rainy season, but also occurs during the dry season. Our data revealed a mean leaf longevity of 141days for peripheral control tillers (unclipped) and 169days for central control tillers. Leaves grow slower and reach shorter length during the dry season compared to the rainy season, and peripheral tillers are always shorter but more vigorous than central tillers (shorter intervals between the emergence of two leaves). There was no stimulation of leaf growth in tillers that were clipped (no overcompensation). Overall, this study suggests ca. two-fold replacement of foliage per year. We explain the continued growth in the dry season by, on average, six times greater soil area occupied by roots than by the leaf canopy, and thus, much greater water availability per tussock than meteorological data would suggest. Wide spacing of tussocks and a large root-sphere mitigate the impact of periodic drought on tissue formation, providing year-round forage for llama

A test of treeline theory on a montane permafrost island

Trees have a common high elevation distribution limit at similar soil temperatures across the globe. Here we tested whether low temperature in the root zone alone can induce the well known dwarfing at the low temperature growth limit of trees by using a ``natural experiment`` with trees growing oil low elevation permafrost ground. At the natural high elevation treeline, both air (shoot) and soil (root) temperature are low, while at the montane permafrost site in the Swiss Jura Mountains, roots are cold, but not shoots. Soil temperature records confirmed that the low elevation study site resembles thermal conditions typical for the high elevation treeline. The warm air conditions have no ameliorating effect on tree growth. Irrespective of shoot temperatures, the root zone temperature and the associated metabolism appear to determine tree growth at this site. The test revealed a critical role of soil temperature, which by itself is sufficient to explain it growth limit of trees associated with a seasonal mean soil temperature at 10 cm depth of around 6 degrees C

Role of KIR3DS1 in Human Diseases

The function of natural killer (NK) cells is controlled by several activating and inhibitory receptors, including the family of killer-immunoglobulin-like receptors (KIRs). One distinctive feature of KIRs is the extensive number of various haplotypes generated by the gene content within the KIR gene locus as well as by highly polymorphic members of the KIR gene family, namely KIR3DL1/S1. Within the KIR3DL1/S1 gene locus, KIR3DS1 represents a conserved allelic variant and displays other unique features in comparison to the highly polymorphic KIR3DL1 allele. KIR3DS1 is present in all human populations and belongs to the KIR haplotype group B. KIR3DS1 encodes for an activating receptor featuring the characteristic short cytoplasmic tail and a positively charged residue within the transmembrane domain, which allows recruitment of the ITAM-bearing adaptor molecule DAP12. Although HLA class I molecules are thought to represent natural KIR ligands, and HLA-Bw4 molecules serve as ligands for KIR3DL1, the ligand for KIR3DS1 still needs to be identified. Despite the lack of formal evidence for an interaction of KIR3DS1 with HLA-Bw4-I80 or any other HLA class I subtype to date, a growing number of associations between the presence of KIR3DS1 and the outcome of viral infections have been described. Especially, the potential protective role of KIR3DS1 in combination with HLA-Bw4-I80 in the context of HIV-1 infection has been studied intensively. In addition, a number of recent studies have associated the presence or absence of KIR3DS1 with the occurrence and outcome of some malignancies, autoimmune diseases, and graft-versus-host disease (GVHD). In this review, we summarize the present knowledge regarding the characteristics of KIRD3S1 and discuss its role in various human diseases