Pollen percentage thresholds of Abies alba based on 13-year annual records of pollen deposition in modified Tauber traps: perspectives of application to fossil situations

Abies alba (fir), a submontane tree from Central European mountains and uplands, is of special interest for palaeoecological and palaeoclimate interpretations due to its sensitivity to air and soil humidity. Its present distribution limit in the uplands of SE Poland is still a matter of debate. In the Holocene fir expanded to Poland very late, but early fir populations are supposed to occur in the Šumava Mts (Czech Republic). The study aims: to estimate pollen thresholds for fir presence/absence in Bohemia (Czech Republic) and Poland on the basis of modified Tauber pollen traps; to use these thresholds for tracing fir presence in two pollen diagrams from Poland (Słone and Bezedna lakes) in the border zone between the Roztocze region (with fir forest stands today) and Polesie (where fir has never played an important role); and to investigate how the percentage presence/absence threshold can be used to trace the occurrence and abundance of fir trees in the Šumava Mts based on the pollen diagrams of Rokytecká slat' and Mrtvý luh. The fir pollen thresholds estimated in terms of PAR (pollen accumulation rates or pollen influx) range from 843 (grains cm− 2 year− 1) (Roztocze) to 61 (Krkonoše) and 49 (Šumava). Percentage thresholds range from 0.3% in Krkonoše where fir trees are not present within 4 km to 22% in fir-dominated woodland of the Roztocze, providing evidence of strong underrepresentation of fir in the pollen deposition. Application of these percentage thresholds to the Słone and Bezedna pollen diagrams indicates that occurrence of fir in the region is possible from 3.5 cal ky BP onwards, though the evidence is not decisive. In the Šumava, a low representation of fir pollen (1–2%) reflecting presence of scattered fir trees was detected as early as ca. 7.0 cal ky BP.

The pollen tube: a soft shell with a hard core

Plant cell expansion is controlled by a fine-tuned balance between intracellular turgor pressure, cell wall loosening and cell wall biosynthesis. To understand these processes, it is important to gain in-depth knowledge of cell wall mechanics. Pollen tubes are tip-growing cells that provide an ideal system to study mechanical properties at the single cell level. With the available approaches it was not easy to measure important mechanical parameters of pollen tubes, such as the elasticity of the cell wall. We used a cellular force microscope (CFM) to measure the apparent stiffness of lily pollen tubes. In combination with a mechanical model based on the finite element method (FEM), this allowed us to calculate turgor pressure and cell wall elasticity, which we found to be around 0.3 MPa and 20–90 MPa, respectively. Furthermore, and in contrast to previous reports, we showed that the difference in stiffness between the pollen tube tip and the shank can be explained solely by the geometry of the pollen tube. CFM, in combination with an FEM-based model, provides a powerful method to evaluate important mechanical parameters of single, growing cells. Our findings indicate that the cell wall of growing pollen tubes has mechanical properties similar to rubber. This suggests that a fully turgid pollen tube is a relatively stiff, yet flexible cell that can react very quickly to obstacles or attractants by adjusting the direction of growth on its way through the female transmitting tissue.

The European Modern Pollen Database (EMPD) project

Modern pollen samples provide an invaluable research tool for helping to interpret the quaternary fossil pollen record, allowing investigation of the relationship between pollen as the proxy and the environmental parameters such as vegetation, land-use, and climate that the pollen proxy represents. The European Modern Pollen Database (EMPD) is a new initiative within the European Pollen Database (EPD) to establish a publicly accessible repository of modern (surface sample) pollen data. This new database will complement the EPD, which at present holds only fossil sedimentary pollen data. The EMPD is freely available online to the scientific community and currently has information on almost 5,000 pollen samples from throughout the Euro-Siberian and Mediterranean regions, contributed by over 40 individuals and research groups. Here we describe how the EMPD was constructed, the various tables and their fields, problems and errors, quality controls, and continuing efforts to improve the available data.

Erratum to: The European Modern Pollen Database (EMPD) project

Unfortunately, the list of authors contains a number of duplications, omissions and other errors in the original publication of the article. The correct list appears in this erratum.

On trend estimation under monotone Gaussian subordination with long-memory: application to fossil pollen series

Fossil pollen data from stratigraphic cores are irregularly spaced in time due to non-linear age-depth relations. Moreover, their marginal distributions may vary over time. We address these features in a nonparametric regression model with errors that are monotone transformations of a latent continuous-time Gaussian process Z(T). Although Z(T) is unobserved, due to monotonicity, under suitable regularity conditions, it can be recovered facilitating further computations such as estimation of the long-memory parameter and the Hermite coefficients. The estimation of Z(T) itself involves estimation of the marginal distribution function of the regression errors. These issues are considered in proposing a plug-in algorithm for optimal bandwidth selection and construction of confidence bands for the trend function. Some high-resolution time series of pollen records from Lago di Origlio in Switzerland, which go back ca. 20,000 years are used to illustrate the methods.

Atlantoaxial epidural abscess secondary to grass awn migration in a dog.

A two-year-old female Lucerne Hound was presented with a one-week history of signs of progressive neck pain, inappetence, apathy, and an elevated rectal temperature. Findings of magnetic resonance imaging (MRI) were consistent with a foreign body abscess in the epidural space at the level of the first and second cervical vertebrae. A left-sided dorso-lateral atlantoaxial approach was performed, revealing an epidural abscess containing a grass awn. The clinical signs resolved within three days of surgery and the dog made a full recovery. This case report shows that grass awns can migrate to the atlantoaxial region in dogs and MRI findings lead to a suspicion of caudo-cranial migration within the spinal canal.