An 854-year tree-ring chronology of Scots pine for south-west Finland

A near-mil len nial tree-ring chro nol ogy (AD 1147–2000) is pre sented for south-west Fin land and an a lyzed us ing dendroclimatic meth ods. This is a com pos ite chro nol ogy com pris ing sam ples both from stand ing pine trees (Pinus sylvestris L.) and subfossil trunks as re cov ered from the lake sed i ments, with a to tal sam ple size of 189 tree-ring sample se ries. The se ries were dendrochronologically cross-dated to ex act cal en dar years to por tray vari abil ity in tree-ring widths on inter-an nual and lon ger scales. Al though the stud ied chro nol ogy cor re lates sta tis ti cally sig nif i cantly with other long tree-ring width chro nol o gies from Fin land over their com mon pe riod (AD 1520–1993), the south-west chro nol ogy did not ex hibit sim i larly strong mid-sum mer tem per a ture or spring/early-sum mer pre cip i ta tion sig nals in com par i son to pub lished chro nol o gies. On the other hand, the south-west chro nol ogy showed high est cor re la tions to the North At lan tic Os cil la tion in di ces in win ter/spring months, this as so ci a tion fol low ing a dendroclimatic fea ture com mon to pine chro nol o gies over the re gion and ad ja cent ar eas. Paleoclimatic com par i son showed that tree-rings had var ied sim i larly to cen tral Eu ro pean spring tem per a tures. It is pos tu lated that the col lected and dated tree-ring ma te rial could be stud ied for wood sur face reflectance (blue chan nel light in ten sity) and sta ble iso topes, which both have re - cently shown to cor re late notably well with sum mer tem per a tures

Tree height strongly affects estimates of water-use efficiency responses to climate and CO2 using isotopes

Various studies report substantial increases in intrinsic water-use efficiency (Wi), estimated using carbon isotopes in tree rings, suggesting trees are gaining increasingly more carbon per unit water lost due to increases in atmospheric CO2. Usually, reconstructions do not, however, correct for the effect of intrinsic developmental changes in Wi as trees grow larger. Here we show, by comparingWi across varying tree sizes at one CO2 level, that ignoring such developmental effects can severely affect inferences of trees' Wi. Wi doubled or even tripled over a trees' lifespan in three broadleaf species due to changes in tree height and light availability alone, and there are also weak trends for Pine trees. Developmental trends in broadleaf species are as large as the trends previously assigned to CO2 and climate. Credible future tree ring isotope studies require explicit accounting for species-specific developmental effects before CO2 and climate effects are inferred.Peer reviewe

A general modeling and visualization tool for comparing different members of a group: application to studying tau-mediated regulation of microtubule dynamics

<p>Abstract</p> <p>Background</p> <p>Innumerable biological investigations require comparing collections of molecules, cells or organisms to one another with respect to one or more of their properties. Almost all of these comparisons are performed manually, which can be susceptible to inadvertent bias as well as miss subtle effects. The development and application of computer-assisted analytical and interpretive tools could help address these issues and thereby dramatically improve these investigations.</p> <p>Results</p> <p>We have developed novel computer-assisted analytical and interpretive tools and applied them to recent studies examining the ability of 3-repeat and 4-repeat tau to regulate the dynamic behavior of microtubules in vitro. More specifically, we have developed an automated and objective method to define growth, shortening and attenuation events from real time videos of dynamic microtubules, and demonstrated its validity by comparing it to manually assessed data. Additionally, we have used the same data to develop a general strategy of building different models of interest, computing appropriate dissimilarity functions to compare them, and embedding them on a two-dimensional plot for visualization and easy comparison. Application of these methods to assess microtubule growth rates and growth rate distributions established the validity of the embedding procedure and revealed non-linearity in the relationship between the tau:tubulin molar ratio and growth rate distribution.</p> <p>Conclusion</p> <p>This work addresses the need of the biological community for rigorously quantitative and generally applicable computational tools for comparative studies. The two-dimensional embedding method retains the inherent structure of the data, and yet markedly simplifies comparison between models and parameters of different samples. Most notably, even in cases where numerous parameters exist by which to compare the different samples, our embedding procedure provides a generally applicable computational strategy to detect subtle relationships between different molecules or conditions that might otherwise escape manual analyses.</p