Effects of simulated climate change on High Arctic soil arthropods at Alexandra Fiord, Nunavut, Canada using open-topped chambers.

January 2002

Abstract

The study of Arctic arthropods has been an ongoing project for decades. The relative simplicity of the ecological relationships in comparison to tropical or even temperate regions has made the Arctic an attractive study site. Relative simplicity, however, does not mean simple. The relationships between arthropods and their environment including interactions with plants, vertebrates and other arthropods are very complex and require a great deal of study to make sense of them. One of the main reasons Arctic arthropods have been studied recently, is their unique position to act as environmental indicators in regards to global warming. The increase in global temperature seen by many scientists is predicted to have its first and greatest effects in the global polar regions. Arthropods, being temperature and moisture sensitive, are prime candidates for basing climate change predictive models. The International Tundra Experiment (ITEX) open-topped chamber (OTC) program at Alexandra Fiord, Ellesmere Island, Nunavut, is one such study site where the arthropods are sampled from open field and OTC treatments. The OTCs increase the ambient air and soil temperatures by two to three degrees Celsius. By comparing populations of arthropods found in the two different areas, it is hoped that a model of population change can be created which will serve to indicate a climate shift. The use of arthropods should not convey the impression that the temperature change will be the direct cause of a fluctuation in population. It is possible that alterations in abundance of food sources as a result of increased temperatures will be the cause of population changes, as plants flourish or die back or as one species out-competes another for resources. Alternatively, changes in humidity levels may result in increased rates of desiccation, as occurs in some species of Collembola during periods of low humidity. During the summer of 2000, there was no significant difference found between the populations of OTC and control treatments of the most prevalent soil arthropods in the Arctic, the Collembola and the Acari. A number of possible reasons are given for this. The OTCs were researched and found to be adequate tools for the manipulation of temperature, but effects of other climatic variables could not be determined. The sampling plan used in 2000 was looked at and found to be of good design; however, some modifications are suggested.

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Forest Fragmentation and the Conservation of Native Arthropods

January 2002

Forest arthropods are important members of the forest ecosystem as they perform tasks such as decomposition and recycling of nutrients from dead plant and animal matter, pollination and seed dispersal, as well as provide non-essential services such as increasing human enjoyment of forests (Schowalter 1995). Over the past 8000 years human activities have disturbed forests as they are utilized for wood products or cleared to make way for urbanization and agriculture (Ozanne et al. 2000). Degradation of arthropod habitat world-wide is caused by deforestation, which results in either altered habitat in the form of forest fragments or remnants, or complete loss of habitat (Scudder 1996; Abensperg-Traun and Smith 1999). Many forest arthropods, such as Collembola and other flightless insects, are poor dispersers and may not be able to adapt quickly to rapid large scale habitat alterations and must therefore be protected to minimize risk of extinction after deforestation events (Winchester and Ring 1999). Arthropods are more abundant than all eukaryotes combined but are often overlooked in conservation efforts (Schowalter 1995; Scudder 1996). These efforts do not focus on arthropods for many reasons, including lack of information about specific arthropod groups such as Acari or Collembola (Winchester and Ring 1999; Ozanne et al. 2000; Basset 2001). British Columbia lacks information on arthropods, with only a few published works covering a couple of families of Diptera and Lepidoptera (Scudder 1996). Beyond broad generalities, we do not yet know the significance of the functional role of forest arthropods, which is important to allow for effective conservation of habitat and species. Protection of habitat in the form of old-growth, second-growth, or forest remnants is essential for effective conservation measures to ensure forest arthropod populations are maintained (Winchester 1997). The development of plantations is not an adequate protective measure for native forest arthropods.

Many forest arthropod species are currently at risk of local or total extinction because of anthropogenic alterations to their habitats (Scudder 1996; Winchester and Ring 1999). Centinelan extinctions, the extinction of species before they are discovered, are also a concern as little is known about the number of arthropod species actually present in forests (Winchester and Ring 1996). Numerous studies have shown that habitat fragmentation as a result of forestry or agriculture has negative effects on native arthropod communities such as increasing susceptibility of small populations to stochastic extinction events, loss of dispersion ability with increased distance between remnants and lowered habitat quality for reproduction, shelter and food availability (Buse and Good 1993; Bedford and Usher 1994; Greenberg and McGrane 1996; Watt et al. 1997; Winchester 1997; Abensperg-Traun and Smith 1999; Oliver et al. 2000; Davis et al. 2001). For example, fragmentation has been demonstrated to reduce the number of large prey items available for certain spiders in forests in the Tokyo area, resulting in decreases in number of spider species and individuals (Miyashita et al. 1998). Many of these forest arthropod species do not disperse effectively, and therefore the risk of extinction may be quite high (Hoekstra et al. 1995).

Arthropods with strong dispersal mechanisms may make use of forest remnants as stepping stones, or they may function as a metapopulation which effectively increases their population size. Movement between fragments depends on the distance between fragments and the nature of the matrix in which they are embedded. For species that do not have good dispersal abilities, dispersal might not be possible if the fragment is isolated. Other species, such as ants and termites which disperse aerially, may be able to colonize distant fragments if intervening spaces are not too large. In agricultural settings, the distance between fragments is often substantial and the intervening area hostile, limiting the chances of colonization and the development of a metapopulation dynamic (Abensperg-Traun and Smith 1999). The conservation of forest remnants is therefore an important effort. McWilliam and Death (1998) support the conservation of forest fragments to minimize losses of arthropod diversity. In a harvested forest, larger remnants result in higher probabilities that endemic populations of arthropods will remain extant and that population density and species richness will be higher (Ozanne et al. 2000).

Deforestation and the replacement of the forest with a plantation does not allow for the conservation of the original arthropods. Forest arthropod species richness and diversity in old-growth forests and mature second-growth forests have been shown to differ greatly from that of plantations. Plantations, which are often forest monocultures, are very susceptible to pest outbreaks and disease, and support lower abundance and fewer species of the native fauna (Schowalter 1989; Schowalter 1995). However, selective logging of forests has been shown to have significant positive effects upon soil arthropod communities in a coastal redwood forest by increasing the numbers of macrophytophages and decreasing the numbers of arthropod predators, although the community structure is slightly different than the original (Hoekstra et al. 1995). To effectively conserve forest arthropods, focus must be placed on conservation of habitat. The control of forest harvesting and the expansion of cities and agriculture is vital, as well as education of the public on the importance of arthropods to the forest. Selective logging, decreasing the need for plantations, may be an option to diminish the damage done to arthropod habitat during deforestation. To understand the processes by which arthropods interact with the forest environment, in-depth studies of arthropod species must be undertaken by universities, governments and private researchers, which will lead to more enlightened conservation methods (Wilson 1999). Without these steps, the loss of arthropods and changes in species composition may be detrimental to forest processes as a whole (Winchester 1997).

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A review of the MERIS sensor and its applications.

April 2001

Introduction

MERIS, the Medium Resolution Imaging Spectrometer sensor, which is to be flown on ENVISAT-1, is one of the newest projects being completed by the European Space Agency (ESA). ENVISAT-1 is tentatively scheduled to be launched in July 2001 with a total of 11 sensors onboard including a SAR radar sensor (ESA, 2000). MERIS will be a multi-purpose sensor designed to gather data for a number of applications at regional to global scales (Dawson, 2000). The primary objective of MERIS will be to look at ocean colour, both in the open ocean and in coastal areas, and secondarily study atmospheric constituents associated with clouds, water vapour and aerosols and finally to look at land vegetation parameters (International, 2001). The oceanographic portion of the MERIS mission will consist of data collection focusing on photosynthetic potential (chlorophyll concentrations) and concentrations of yellow substance (Gelbstoff) and suspended mineral materials. The atmospheric applications will be used to study clouds, as well as to provide very accurate assessments of aerosols and atmospheric turbidity, which will aid in atmospheric corrections. The land portion of the mission will look at vegetation and the data may be used to help determine biomass and productivity (Rast, 1999, Moore, 1999 and Verstraete, 1999).

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The interactions of light creating iridescence in Morpho species butterfly wing scales.

April 2001 - Poster

Abstract

The blue iridescent colouration of Morpho species butterfly wings is the result of light interacting with the microscopic structure of wing scales. These scales are composed of cuticle, a complex of proteins, lipids and other molecules. Scales may contain an absorbing pigment such as melanin, in small quantities. The main mechanism of iridescence is interference caused by thin-film structures in the scales. Different configurations of thin-film structures are responsible for colour changes seen when a wing is looked at from different angles. A scanning electron microscope (SEM) was used to look closely at the structure of wing scales of the species Morpho peleides and the interaction of light with the architecture was discussed.

A review of wing scale architecture in relation to colour production in Morpho peleides, Danaus plexippus and Papilio memnon ssp wings.

Greg Smith and Cassie Holcomb, April 2001 - Poster

Abstract

Scales are the cuticular features that give butterflies their beautiful, multi-coloured wings. Scales are flattened macrosetae, which have specific structural and chemical properties that help to determine the colour that we see (Ghiradella, 1998). The purpose of the study was to determine differences in scale microstructure producing different colours in three species: Danaus plexippus Linnaeus, Morpho peleides Kollar and Papilio memnon ssp. Images taken by a scanning electron microscope (SEM) were used to measure differences in ridge and crossrib arrangement. Although ridges were spaced approximately equally (2 micrometers) in each species, crossribs were different in structure and size. We concluded that scale morphology does differ between species but are unsure of the direct effect on the colour projected by a wing.