(searched for: doi:10.1299/jsmeb.49.583)
Frontiers in Earth Science, Volume 5; https://doi.org/10.3389/feart.2017.00085
Modern pollen spectra are an invaluable reference tool for paleoenvironmental and cultural landscape reconstructions, but the importance of knowing the pollen rain released from orchards remains underexplored. In particular, the role of cultivated trees is in past and current agrarian landscapes has not been fully investigated. Here, we present a pollen analysis of 70 surface soil samples taken from 12 olive groves in Basilicata and Tuscany, two regions of Italy that exemplify this cultivation in the Mediterranean basin. This study was carried out to assess the representativeness of Olea pollen in modern cultivations. Although many variables can influence the amount of pollen observed in soils, it was clear that most of the pollen was deposited below the trees in the olive groves. A rapid decline in the olive pollen percentages (c. 85% on average) was found when comparing samples taken from IN vs. OUT of each grove. The mean percentages of Olea pollen obtained from the archaeological sites close to the studied orchards suggest that olive groves were established far from the Roman farmhouses of Tuscany. Further south, in the core of the Mediterranean basin, the cultivation of Olea trees was likely situated approximately 500–1000 m from the rural sites in Basilicata, and dated from the Hellenistic to the Medieval period.
Aerobiologia, Volume 33, pp 407-416; https://doi.org/10.1007/s10453-017-9479-1
Source–distance relationships for pollen deposited directly into surface soil have been rarely undertaken, particularly for a single or isolated source, rather than a forest, grove or plantation. This study aimed to determine surface soil pollen deposition patterns from single, isolated source trees and to compare the results to Gaussian model curves for the same trees. Four isolated tree pollen sources were chosen in Worcester, UK: Carpinus betulus, Cedrus atlantica, Juglans nigra and Platanus acerifolia. Surface soil samples were collected at 1, 5 and then every 10 m, up to 100 m distance from the main trunk of each source along the prevailing wind direction during flowering. A Gaussian dispersion model was used to estimate source strength using tree height and width and wind speeds on days when flowering was occurring and when the wind direction flowed along the sampling transect. This model simulated the expected concentration and deposition along the sampling transect. Modelled and observed results showed that most pollen was deposited beneath the canopy (range 63–94%) in an exponentially decreasing curve and the tailing off started from around the outer edge of the canopy in most cases. The amount of pollen deposited at 50 m was no more than 2.6% of total deposition in the samples for any tree and at 100 m no more than 0.2%. Tree height, width and wind speed during the pollination period were found to be the main parameters affecting deposition away from the source.
Journal of Plant Ecology; https://doi.org/10.1093/jpe/rtw054
Aims: Species diversity and genetic diversity may be affected in parallel by similar environmental drivers. However, genetic diversity may also be affected independently by habitat characteristics. We aim at disentangling relationships between genetic diversity, species diversity and habitat characteristics of woody species in subtropical forest. Methods: We studied 11 dominant tree and shrub species in 27 plots in Gutianshan, China, and assessed their genetic diversity (Ar) and population differentiation (F’ST) with microsatellite markers. We tested if Ar and population specific F’ST were correlated to local species diversity and plot characteristics. Multi-model inference and model averaging were used to determine the relative importance of each predictor. Additionally we tested for isolation-by-distance and isolation-by-elevation by regressing pairwise F’ST against pairwise spatial and elevational distances. Important findings: Genetic diversity was not related to species diversity for any of the study species. Thus, our results do not support joint effects of habitat characteristics on these two levels of biodiversity. Instead, genetic diversity in two understory shrubs, Rhododendron simsii and Vaccinium carlesii, was affected by plot age with decreasing genetic diversity in successionally older plots. Population differentiation increased with plot age in Rhododendron simsii and Lithocarpus glaber. This shows that succession can reduce genetic diversity within, and increase genetic diversity between populations. Furthermore, we found four cases of isolation-by-distance and two cases of isolation-by-elevation. The former indicates inefficient pollen and seed dispersal by animals whereas the latter might be due to phenological asynchronies. These patterns indicate that succession can affect genetic diversity without parallel effects on species diversity and that gene flow in a continuous subtropical forest can be restricted even at a local scale.
The ANZIAM Journal, Volume 50, pp 365-380; https://doi.org/10.1017/s144618110900011x
This is a review of progress made since [R. McKibbin, “An attempt at modelling hydrothermal eruptions”, Proc. 11th New Zealand Geothermal Workshop 1989 (University of Auckland, 1989), 267–273] began development of a mathematical model for progressive hydrothermal eruptions (as distinct from “blasts”). Early work concentrated on modelling the underground process, while lately some attempts have been made to model the eruption jet and the flight and deposit of ejected material. Conceptually, the model is that of a boiling and expanding two-phase fluid rising through porous rock near the ground surface, with a vertical high-speed jet, dominated volumetrically by the gas phase, ejecting rock particles that are then deposited on the ground near the eruption site. Field observations of eruptions in progress and experimental results from a laboratory-sized model have confirmed the conceptual model. The quantitative models for all parts of the process are based on the fundamental conservation equations of motion and thermodynamics, using a continuum approximation for each of the components.