Development of a Rapid and Precise Method of Digital Image Analysis to Quantify Canopy Density and Structural Complexity

Estimation of canopy density is necessary for ecological research and woodland management. However, traditional manual methods are time consuming and subject to interobserver variability, while existing photographic methods usually require expensive fish-eye lenses and complex analysis. Here we introduce and test a new method of digital image analysis, CanopyDigi. This allows user-defined threshold to polarise the 256 grey shades of a standard monochrome bitmap into dark “canopy” and light “sky” pixels (the threshold being selected using false-colour images to ensure its suitability). Canopy density data are calculated automatically and rapidly, and, unlike many other common methods, aggregation data are obtainable using Morisita’s index to differentiate closed (diffuse light) and open (direct light) canopies. Results were highly repeatable in both homogeneous and heterogeneous woodland. Estimates correlated strongly with existing (nondigital) canopy techniques, but quicker and with significantly lower interobserver variability (CV = 3.74% versus 20.73%). We conclude that our new method is an inexpensive and precise technique for quantifying canopy density and aggregation

Electron Confinement, Orbital Ordering, and Orbital Moments in d0d^0-d1d^1 Oxide Heterostructures

The (SrTiO$_3$)$_m$/(SrVO$_3$)$_n$ $d^0-d^1$ multilayer system is studied with first principles methods through the observed insulator-to-metal transition with increasing thickness of the SrVO$_3$ layer. When correlation effects with reasonable magnitude are included, crystal field splittings from the structural relaxations together with spin-orbit coupling (SOC) determines the behavior of the electronic and magnetic structures. These confined slabs of SrVO$_3$ prefer $Q_{orb}$=($\pi,\pi$) orbital ordering of $\ell_z = 0$ and $\ell_z = -1$ ($j_z=-1/2$) orbitals within the plane, accompanied by $Q_{spin}$=(0,0) spin order (ferromagnetic alignment). The result is a SOC-driven ferromagnetic Mott insulator. The orbital moment of 0.75 $\mu_B$ strongly compensates the spin moment on the $\ell_z = -1$ sublattice. The insulator-metal transition for $n = 1 \to 5$ (occurring between $n$=4 and $n$=5) is reproduced. Unlike in the isoelectronic $d^0-d^1$ TiO$_2$/VO$_2$ (rutile structure) system and in spite of some similarities in orbital ordering, no semi-Dirac point [{\it Phys. Rev. Lett.} {\bf 102}, 166803 (2009)] is encountered, but the insulator-to-metal transition occurs through a different type of unusual phase. For n=5 this system is very near (or at) a unique semimetallic state in which the Fermi energy is topologically determined and the Fermi surface consists of identical electron and hole Fermi circles centered at $k$=0. The dispersion consists of what can be regarded as a continuum of radially-directed Dirac points, forming a "Dirac circle".Comment: 9 pages, 8 figure

Planet Earth: Our Unsustainable Biosphere

Planet Earth. Our home. Our only life-support system. Clearly then something to be regarded in the highest terms, to be respected, and to be protected at all costs. Yet in 2006, nothing seems further from the truth. The reality is that we are inhabiting an increasingly unstable and unsustainable biosphere

Are the ecological impacts of alien species misrepresented? A review of the “native good, alien bad” philosophy

The study of invasion ecology usually focuses on the negative impacts of alien species, while potential positive impacts are often overlooked. Understanding of biotic interactions may thus be skewed towards the negative, which could have important implications for ecological management and conservation. This article provides a comprehensive review of all types of impacts, both beneficial and detrimental, that can result from species translocation. An extensive review of literature on species introductions to terrestrial, freshwater and marine ecosystems and involving a wide range of taxa (including microorganisms, parasites, plants, insects, amphibians, reptiles, birds, mammals, fish and Crustacea) showed that, despite limited research into facilitative alien-native interactions, such interactions occur surprisingly frequently. Examples were found of introduced species acting as hosts, food sources, pollinators or seed dispersers for native species, as well as providing herbivory, predatory or parasite release. However, research showed that numerous negative interactions also occurred and combination impacts (when an alien benefits some natives but disadvantages others) were common. In many cases, the traditional view that biological invasions constitute a significant threat to native biota is both accurate and appropriate. Efforts to prevent translocation and control non-native species can be vital. However, the “native good, alien bad” maxim does not convey the complexity of invasion ecology: alien species do not axiomatically pose a threat to native biota. In order to move understanding of invasion ecology forward and to develop maximally-effective management strategies, facilitative alien-native interactions need to be added into the alien species debate

Feathered competitors: what birds can teach ecologists about species interactions

Interspecific Competition in Birds. André A. Dhondt.\ud Oxford University Press, Oxford. 27 October 2011. pbk. pp 296. ISBN 978-0-19-958902-9

Statistics on Graphs, Exponential Formula and Combinatorial Physics

The concern of this paper is a famous combinatorial formula known under the name "exponential formula". It occurs quite naturally in many contexts (physics, mathematics, computer science). Roughly speaking, it expresses that the exponential generating function of a whole structure is equal to the exponential of those of connected substructures. Keeping this descriptive statement as a guideline, we develop a general framework to handle many different situations in which the exponential formula can be applied

CCRS proposal for evaluating LANDSAT-D MSS and TM data

Accomplishments in the evaluation of LANDSAT 4 data are reported. The objectives of the Canadian proposal are: (1) to quantify the LANDSAT-4 sensors and system performance for the purpose of updating the radiometric and geometric correction algorithms for MSS and for developing and evaluating new correction algorithms to be used for TM data processing; (2) to compare and access the degree to which LANDSAT-4 MSS data can be integrated with MSS imagery acquired from earlier LANDSAT missions; and (3) to apply image analysis and information extraction techniques for specific user applications such as forestry or agriculture

Phase Competition in Ln0.5a0.5mno3 Perovskites

Single crystals of the systems Pr0.5(Ca1-xSrx)0.5MnO3, (Pr1-yYy)0.5(Ca1-xSrx)0.5MnO3, and Sm0.5Sr0.5MnO3 were grown to provide a series of samples with fixed ratio Mn(III)/Mn(IV)=1 having geometric tolerance factors that span the transition from localized to itinerant electronic behavior of the MnO3 array. A unique ferromagnetic phase appears at the critical tolerance factor tc= 0.975 that separates charge ordering and localized-electron behavior for t<tc from itinerant or molecular-orbital behavior for t>tc. This ferromagnetic phase, which has to be distinguished from the ferromagnetic metallic phase stabilized at tolerance factors t>tc, separates two distinguishable Type-CE antiferromagnetic phases that are metamagnetic. Measurements of the transport properties under hydrostatic pressure were carried out on a compositions t a little below tc in order to compare the effects of chemical vs. hydrostatic pressure on the phases that compete with one another near t=tc.Comment: 10 pages. To be publised in Phys. Rev.

Developing a Supportive Framework for Learning on Biosciences Field Courses through Video-Based Resources

Field courses are an essential component of the undergraduate experience in many subjects, but are intensive and expensive for participating students. Unpreparedness often means time is used teaching the basics rather than challenging students in exciting and novel situations. Moreover, universal participation is not always possible. Video-based resources covering key concepts and techniques could help participant preparedness and could be used independently by non-participants. This reflective case study details a collaborative project in which students and instructors worked together to make conceptual and instructional videos during a highly applied biosciences field course in South Africa. In 2012, after training from a professional wildlife filmmaker, students were involved in planning, presenting, and filming 25 videos. Students benefited considerably from the filmmaking process as explaining concepts and filming techniques helped reinforce their understanding: an example of "see one, do one, teach one." The online, open-access videos were used by the 2013 cohort to increase preparedness and independently by non-participants to good effect, both internally and at several external institutions. New videos will be added each year to expand the resource base and allow students to gain from the filmmaking experience. This teaching and learning strategy is multidisciplinary, with relevance for a range of subjects

Structural, orbital, and magnetic order in vanadium spinels

Vanadium spinels (ZnV_2O_4, MgV_2O_4, and CdV_2O_4) exhibit a sequence of structural and magnetic phase transitions, reflecting the interplay of lattice, orbital, and spin degrees of freedom. We offer a theoretical model taking into account the relativistic spin-orbit interaction, collective Jahn-Teller effect, and spin frustration. Below the structural transition, vanadium ions exhibit ferroorbital order and the magnet is best viewed as two sets of antiferromagnetic chains with a single-ion Ising anisotropy. Magnetic order, parametrized by two Ising variables, appears at a tetracritical point.Comment: v3: streamlined introductio