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Litter-Dwelling Arthropods

The Arthropoda phylum accounts for approximately three quarters of the Earth’s organisms (Yi, H. M., Andrew Ralph, 2011), inhabiting both water and land; they are the most diverse of taxa of invertebrates. Arthropods are characterized as having segmented bodies, bilateral symmetry, and exoskeletons made of chitin (Introduction to Phylum Arthropoda, 2012). Litter dwelling arthropods are those that inhabit the leaf litter, and it is these litter dwelling species that will be the topic of discussion for this paper.

Arthropods have been widely studied in scientific literature, likely due to the key role that they play in ecosystem function. For example, Arthropods play an important role in the decomposition of organic matter, maintaining soil structure and fertility, enabling flowering plant reproduction, nutrient cycling and regulating the populations of other organisms (Buddle et al. 2005; Danks 1992; Kremen et al. 1993 and Wiggins et al. 1991).

Due to the nature of Arthropods as highly adapted species, their habitat requirements are highly specific. As such, the nature of the habitat plays an important role in the composition of arthropod species found there (Buddle, 2006). As a consequence of their specific habitat requirements, arthropods are extremely susceptible to shocks that may alter their living environments. In fact, arthropods are often the first species to disappear in a threatened ecosystem. As such, arthropods have been widely used as bioindicators for pollution, habitat disturbance and climate change (Hawksworth and Ritchie 1993; McGeoch 1998).

The biodiversity of these organisms within an ecosystem is dependent on many factors, including the amount of sunlight exposure on the soil surface, moisture of the litter and the type of plants growing in the area (Hutchinson,2011). Human management of soils, particularly in agricultural fields, has shown to decrease arthropod species richness, and is a major cause of community depletions. Many arthropods prefer undisturbed areas because of the abundance of plant biomasses which can be fully utilized (Hooper, et al. 2000). It has also been suggested that the amount of vegetation cover over an arthropod habitat can be an influential factor contributing to the species composition. The abundance of many arthropod species is directly dependant on the abundance of edible plants and therefore edible biomass that the arthropods depend on.

From a slightly different perspective, it could be argued that it is the arthropod diversity that has a positive effect on vegetation cover, rather than the other way around. Many of the arthropods are able to decompose litter into nutrients that will eventually eluviate in the soil and will be used for plant growth. However, some arthropods negatively impact the vegetation. For example, an insect larvae dwelling beneath the tree’s bark causes the birch bark tree disease.

Litter-dwelling arthropods play an indispensable role in terms of both their function in natural environmental processes as well as their use as tools for scientific research. The latter reason is predominantly focused on the responsiveness of arthropods to environmental change, thus proving them valuable bioindicators. Hence, studying the composition of arthropod species within specific habitats can be used in managing and monitor environmental change

As such, we, a group of four McGill students taking a class in Environmental Biology, will be embarking on a project to assess the composition of arthropod species amongst different habitat types. Our research will take place in the Morgan Arboretum, a teaching, research, and education oriented forest reserve located near Sainte-Anne-de-Bellevue, Quebec. The project will aim to characterise species composition amongst different forest types within the Arboretum.

The Morgan Arboretum spans 245 hectares (Arboretum, 2006) and is divided into different areas, each comprised of different soil profiles. The variation in soil composition gives rise to distinct sections within the forest, which are delimited by their unique flora. Two specific sites within the Morgan Arboretum were selected: the Maple Square and the Upland region. These two locations strategically have very different characteristics. While the Maple Square is, as the name decrees, covered by maple trees, the Upland region is predominantly covered by pine and beech trees. The resulting leaf litter will be vastly different, harbouring dissimilar arthropod species.

An initial round of species collection has begun from the two forest sites using two different collection methods. The two locations are expected to yield different arthropod species composition.

The first collection method being used is pitfall traps.

Both of the Uplands and the Maple Square sites were staggered with six pitfall traps divided in three pairs.

The second method we are using is leaf litter sifting.

This method involved instantaneous data collection as leaf litter is sifted in situ and the species are stored for identification in the lab.

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References

Arboretum, M. (2012, June 2012) Retrieved Oct. 2012, from http://www.morganarboretum.org/fma/

Buddle, C. M., Langor, D. W., Pohl, G. R., & Spence, J. R. (2006). Arthropod responses to harvesting and wildfire: Implications for emulation of natural disturbance in forest management. Biological Conservation, 128(3), 346-357. doi: 10.1016/j.biocon.2005.10.002

Danks, H.V. (1992). Long life cycles in insects. Can. Ent. 124(1): 167-187

Hawksworth, D.L. and J.M. Ritchie. (1993). Biodiversity and Biosystematic Priorities: Microorganisms and Invertebrates. CAB International Wallingford UK. 70 pp. + annexes.

Hutchinson, L. ARTHROPOD BIODIVERSITY LAB: Teacher Template. Easton High School, Talbot County Public Schools, Maryland. http://www.enviroliteracy.org/pdf/materials/1244.pdf

Kremen, C., R.K. Colwell, T.L. Erwin, D.D. Murphy, R.F. Noss, M.A. Sanjayan. (1993). Terrestrial arthropod assemblages: their use in conservation planning. Conservation Biology 7(4): 796-808.

McGeogh, M. (1998). The Selection, Testing and Application of Terrestrial Insects As Bioindicators. Biological Reviews 73:2, 181-201
Morgan Arboretum Collection Plantings http://www.morganarboretum.org/ENGLISH/nature/trees.html\

Myers, P. 2001. “Arthropoda” (On-line), Animal Diversity Web. Accessed October 23, 2012 at http://animaldiversity.ummz.umich.edu/ accounts/Arthropoda/

Sanjayan. (1993). Terrestrial arthropod assemblages: their use in conservation planning. Conservation Biology 7(4): 796-808.

Schindler, B., Griffith, A., Jones, K. (2011) Factors Influencing Arthropod Diversity on Green Roofs. Cities and the Environment. Volume 4, issue 1, article 5.

UCMP Berkeley [Internet]. 2006. California:  Regents of the University of California [cited: Oct. 2012]. Available from: http://animaldiversity.ummz.umich.edu/accounts/Arthropoda/University of Minnesota, Introduction to Phylum Arthropoda, 2012. http://www.entomology.umn.edu/cues/4015/handouts/Orders.htm

Watson, and A. Ghani. 1999. Plant removals in perennial grassland: Vegetation dynamics, decomposers, soil biodiversity, and ecosystem properties. Ecological Monographs 69(4):535–568.

Wiggins, G.B. 1983. Entomology and society. Bull. ent. Soc. Am. 29: 27-29.

Wiggins, G.B., S.A. Marshall, J.A. Downes. (1991). The importance of research collections of terrestrial arthropods. A brief prepared by the Biological Survey of Canada (Terrestrial Arthropods). Bulletin of the Entomological Society of Canada 23(2), supplement 16 pp.

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About Crystal Ernst

Hakai Institute postdoctoral scholar at Simon Fraser University (B.C.)

8 comments on “Litter-Dwelling Arthropods

  1. Sounds like a really cool project!

    I know earthworms aren’t arthropods, but your mention of how arthropods affect nutrient cycling by decomposing the leaf litter made me think of the earthworm problem in my part of the country. I live in northern Wisconsin, and while earthworms aren’t native here, we have introduced European species. They change the forest floor vegetation in a lot of ways and can have a negative effect on native wildlife like ground-nesting songbirds.

    • First off, thanks! We’re aware that earthworms can speed up nutrient cycling to the point that exposes the roots and increases the chance of soil erosion due to water runoff, but we don’t think arthropods have the same effect (fortunately!). To keep our project manageable, we’re keeping our research focused on arthropods.

  2. Sounds like a great way to get some hands on learning. Are your pitfall traps baited or passive? You can find some incredibly interesting arthropods using baited methods. I’ve had some great success with a little bit of hamburger, or even via the accidental introduction of a vole or shrew to the carrion bate (poor little fellows).

  3. Very cool! There are many interesting arthropods hiding under the leaves, it’s a grab bag of taxa. I’ve heard leaf litter described as a miniature rainforest due the diversity it holds. If you get any millipedes, try putting them under a UV light–some groups fluoresce.

  4. Obviously plants and trees are great for the sinuses as well.
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