Multi-decadal changes in tundra environments and ecosystems: synthesis of the International Polar Year-Back to the Future project (IPY-BTF)

Understanding the responses of tundra systems to global change has global implications. Most tundra regions lack sustained environmental monitoring and one of the only ways to document multi-decadal change is to resample historic research sites. The International Polar Year (IPY) provided a unique opportunity for such research through the Back to the Future (BTF) project (IPY project #512). This article synthesizes the results from 13 papers within this Ambio Special Issue. Abiotic changes include glacial recession in the Altai Mountains, Russia; increased snow depth and hardness, permafrost warming, and increased growing season length in sub-arctic Sweden; drying of ponds in Greenland; increased nutrient availability in Alaskan tundra ponds, and warming at most locations studied. Biotic changes ranged from relatively minor plant community change at two sites in Greenland to moderate change in the Yukon, and to dramatic increases in shrub and tree density on Herschel Island, and in subarctic Sweden. The population of geese tripled at one site in northeast Greenland where biomass in non-grazed plots doubled. A model parameterized using results from a BTF study forecasts substantial declines in all snowbeds and increases in shrub tundra on Niwot Ridge, Colorado over the next century. In general, results support and provide improved capacities for validating experimental manipulation, remote sensing, and modeling studies.     

Oxidation of As(Ⅲ) by potassium permanganate

The oxidation of As(Ⅲ) with potassium permanganate was studied under conditions including pH, initial As(Ⅲ) concentration and dosage of Mn(Ⅶ). The results have shown that potassium permanganate was an effective agent for oxidizing of As(Ⅲ) in a wide pH range. The pH value of tested water was not a significant factor affecting the oxidation of As(Ⅲ) by Mn(Ⅶ). Although theoretical redox analyses suggest that Mn(Ⅶ) should have better performance in oxidization of As(Ⅲ) within lower pH ranges, the experimental results show that the oxidation efficiencies of As(Ⅲ) under basic and acidic conditions were similar, which may be due to the adsorption of As(Ⅲ) on the Mn(OH)2 and MnO2 resulting from the oxidation of As(Ⅲ).     

Sample preparation and biomass determination of SRF model mixture using cryogenic milling and the adapted balance method

The biogenic fraction of a simple solid recovered fuel (SRF) mixture (80 wt% printer paper/20 wt% high density polyethylene) is analyzed with the in-house developed adapted balance method (aBM). This fairly new approach is a combination of combustion elemental analysis (CHNS) and a data reconciliation algorithm based on successive linearisation for evaluation of the analysis results. This method shows a great potential as an alternative way to determine the biomass content in SRF. However, the employed analytical technique (CHNS elemental analysis) restricts the probed sample mass to low amounts in the range of a few hundred milligrams. This requires sample comminution to small grain sizes (<200 μm) to generate representative SRF specimen. This is not easily accomplished for certain material mixtures (e.g. SRF with rubber content) by conventional means of sample size reduction.This paper presents a proof of principle investigation of the sample preparation and analysis of an SRF model mixture with the use of cryogenic impact milling (final sample comminution) and the adapted balance method (determination of biomass content). The so derived sample preparation methodology (cutting mills and cryogenic impact milling) shows a better performance in accuracy and precision for the determination of the biomass content than one solely based on cutting mills. The results for the determination of the biogenic fraction are within 1–5% of the data obtained by the reference methods, selective dissolution method (SDM) and ¹⁴C-method (¹⁴C-M).     

Molekularbiologie der Gametenvereinigung

Contact between gametes takes place on a molecular basis via receptors on the surface of the egg coat. The functional part of this receptor glycoprotein is limited to the O-glycosidic-linked carbohydrate side chains, and a polypeptide chain of it may induce an acrosomal reaction on the sperm head, thereby inducing penetration of the sperm into the egg cell. Another function of sperm receptors is to block polyspermy, probably due to modification by limited proteolysis of the receptor glycoprotein. Fertilization is likely to be inhibited by steric hindrance of the receptor due to antibodies specific for glycoproteins of the egg coat. The study of gamete interactions on a molecular basis may serve as a model for intercellular recognition in general.     

Phonotaxis during walking and flight: are differences in selectivity due to predation pressure?

Female selectivity was tested in Tettigonia viridissima during two different phonotaxis situations; compensated walking and tethered flight. For two of the three temporal parameters that are important for call recognition in T. viridissima, selectivity was similar in the two situations. Selectivity for the third parameter (minimum interval duration between the double pulses) was much higher during walking than during flight: walking females responded only to stimuli with intervals of 28 ms or longer, while call models with intervals of 18 ms were attractive during flight. One interneuron (TN-1) is probably involved in filtering the minimum interval duration. As this neuron is also the most likely candidate for transmitting bat calls during flight, it is suggested that the selectivity differences between walking and flying might be due to the need for detecting predator signals during flight, when TN-1 would be occupied listening for bats. With TN-1 unavailable for song processing during flight, temporal selectivity for the minimum interval duration should be reduced, as was found here.