Ecology reaseach

Abundance and Distributional Variation of Dragonflies in a Forest in Response to Hydrology and Daily Ambient Temperatures.

This research concerns the dragonflies communities found at Kanahawa State Forest, in Charleston, West Virginia. The aim of the research is to determine where - and at what time of day - the dragonflies in this forest are most abundant. To this end, the number of dragonflies occurring at two study sites were recorded, for six weeks, from September 12th to October 31st.

Throughout the study, the following expectations were held: it was expected that the dragonflies would be more abundant in areas with more standing water, and that there would be more occurrences of dragonflies at midday when the temperatures were higher.

The hypotheses to be tested in this study are therefore:

That dragonflies are more abundant (i.e., there are more individuals of each species, and there are also more species) in areas with standing water, and That dragonflies, in general, will be more abundant at midday, due to their liking of higher temperatures.

Study Sites

The dragonfly communities were studied at two sites, the first of which is a lake (called Special Trout Regulation Area), the second is an open area, which has no shade, and which is full of light. A stream runs through the area, over which hang trees, which provide some shade. The two sites are a mile apart.

Methodology

The number of dragonflies, and the species of each dragonfly recorded, were observed at the two study sites, and were recorded. These assessments of dragonfly abundance were taken at certain time intervals throughout the day, over a six-week period, at 0800, 1200 and 1700.

Species Recorded at the Study Site

Five species of dragonfly were recorded from the sites, the Eastern Grayback (of the genus Tachopteryx); the Spotted Biddie (of the genus Cordulegaster); the 10-Spot (of the genus Celithemis); the Widow (of the genus Erythemis), and the White Tail (of the genus Plathemis). All of these dragonflies are common throughout North America, and in particular, around the Kanahawa State Forest.

Preliminary Results / General Observations

Over the whole time period, more dragonflies were seen at Site one (the lake) than at Site two (the stream). This tentatively supports hypothesis number one, which suggested that dragonflies were more likely to prefer standing water, rather than running water.

Further, as a general observation, more dragonflies were seen when it was hot than when conditions were bad, for example, rainy or grey, with no sun. Generally, more dragonflies were seen at 1200 and at 1700 than at the earlier observation time of 0800. This tentatively supports hypothesis two, which suggested that dragonflies were more likely to be seen when temperatures were high.