Trends and uncertainties in Siberian indicators of 20th century warming

Estimates of past climate and future forest biomass dynamics are constrained by uncertainties in the relationships between growth and climatic variability and uncertainties in the instrumental data themselves. Of particular interest in this regard is the boreal-forest zone, where radial growth has historically been closely connected with temperature variability, but various lines of evidence have indicated a decoupling since about the 1960s. We here address this growth-vs.-temperature divergence by analyzing tree-ring width and density data from across Siberia, and comparing 20th century proxy trends with those derived from instrumental stations. We test the influence of approaches considered in the recent literature on the divergence phenomenon (DP), including effects of tree-ring standardization and calibration period, and explore instrumental uncertainties by employing both adjusted and nonadjusted temperature data to assess growth-climate agreement. Results indicate that common methodological and data usage decisions alter 20th century growth and temperature trends in a way that can easily explain the post-1960 DP. We show that (i) Siberian station temperature adjustments were up to 1.3 °C for decadal means before 1940, (ii) tree-ring detrending effects in the order of 0.6–0.8 °C, and (iii) calibration uncertainties up to about 0.4 °C over the past 110 years. Despite these large uncertainties, instrumental and tree growth estimates for the entire 20th century warming interval match each other, to a degree previously not recognized, when care is taken to preserve long-term trends in the tree-ring data. We further show that careful examination of early temperature data and calibration of proxy timeseries over the full period of overlap with instrumental data are both necessary to properly estimate 20th century long-term changes and to avoid erroneous detection of post-1960 divergence.     

Metabolism-linked Binding of Rubidium in the Free Space of Wheat Roots and its Relation to Active Uptake

Components of the initial uptake and active transport of rubidium were studied in potassium-starved and potassium-rich wheat plants. A metabolism-linked component of the initial uptake in the root was identified by means of DNP-treatment. It was shown that there is a direct proportionality between the magnitude of the metabolism-linked component of the initial uptake and the rate of active uptake. It is suggested that, in the free space, this metabolism-linked ion binding represents an initial step of the active ion transport preceding the subsequent carrier-mediated transport across the plasmalemma.     

Migration, stopover and moult of the Great Reed Warbler Acrocephalus arundinaceus in Ghana, West Africa

We studied Great Reed Warblers Acrocephalus arundinaceus at two localities in Ghana during the winter. In the north (Tono), the birds arrived from late September and conducted a rapid moult soon after arrival. Towards the end of moult, birds accumulated fat and disappeared from the site. In the south (Tafo), birds arrived from mid-November in fresh plumage. This seemed to be the final wintering area as birds stayed there during the winter. In March-April they again accumulated fat, although only small amounts, before spring migration back to breeding areas.     

The Presence of Cellulose in Heterocyst Envelopes of Blue-Green Algae and its Role in Relation to Nitrogen Fixation

The present study gives evidence for the presence of cellulose in the heterocyst envelope of blue-green algae by means of electron microscopy, cellulase treatments and specific staining and demonstrates the role of this cellulose for the protection of the heterocyst nitrogenase during acetylene reduction. Experiments with lysozyme and cellulase suggest that nitrogen fixation in heterocystous blue-green algae under aerobic conditions is functionally effective only when an intimate relationship exists between vegetative cells and heterocysts and both cell types have intact wall structures.     

PARTIAL CHARACTERIZATION OF A PUTATIVE 110kDa MYOSIN FROM THE GREEN ALGACHARA CORALLINABYIN VITROBINDING OF FLUORESCENT F-ACTIN

Using the binding of heterologous, rhodamine phalloidin-labelled F-actinin vitro, two F-actin binding proteins were identified in protein extracts from the green algaChara corallinaafter fractionation by anion exchange chromatography. The first protein, a putative myosin, released laterally bound F-actin at ATP-concentrations as low as 1μm ; equivalent concentrations of ADP were not effective. Binding of F-actin was inhibited by the sulfhydryl-alkylating agent N-ethylmaleimide (NEM). Binding of F-actin was also abolished by a monoclonal anti-myosin (J14) previously used for immunodetection and immunolocalization in internodal cells (Groliget al., 1988,Eur J Cell Biol 47 : 22–31). Immunoblotting with J14 detected a 110kDa polypeptide only in those protein fractions that had revealed ATP-sensitive binding of F-actin. The putative myosin bound with mediocre affinity to immobilized calmodulin and free Ca²⁺-concentration made no difference to this binding affinity. In contrast to the putative myosin, the second, less abundant protein revealed ATP-insensitive and end-wise binding to the microfilament and was not recognized by the anti-myosin antibody.     

Mitochondrial DNA and two perspectives on evolutionary genetics

This essay reviews comparative studies of animal mitochondrial DNA (mtDNA), with emphasis on findings made and ideas developed at Berkeley. It argues that such studies are bringing together two previous paths of progress in evolutionary biology. One path is that of those who worked far above the species level and were concerned with genealogical trees, time scales and the accumulation of new mutations on surviving molecular lineages. The other path is that of those who worked at and below the species level and were concerned mainly with population structure, migration and the frequencies of alleles that existed in an ancestral population. This fusion of paths is made possible by the high rate at which mutations accumulate on mtDNA lineages and by this molecule's uniparental and apparently haploid mode of inheritance. These properties make mtDNA a superb tool for building trees and time scales relating molecular lineages at and below the species level. In addition, owing to its mode of inheritance, mtDNA is more sensitive to bottlenecks in population size and to population subdivision than are nuclear genes. Joint comparative studies of both mtDNA and nuclear DNA variability give us valuable insights into how effective population size has varied through time. Such studies also give insight into the conditions under which mtDNA from one species can colonize another species.     

The impossibility of inverted suture lines in ammonites

The biological organization of ammonites does not permit a true inversion of suture lines to occur. However, the complex pattern of the ammonite phragmocone - nacreous septa, membrane coverings, siphuncle, and soft body - does show 'weak points' in growth regulation. This provides several instabilities which lead to a pseudo-inversion caused by mechanical compression of the saddles.