Vernal pool

2014 is the “Year of the Vernal Pool.” Unofficially, that is. 2014 is the year I discovered that many animals — many habitat-specific odonates in particular — prefer vernal pools. In fact, a quick look at my blog posts tagged with the phrase “vernal pool” shows the oldest post is dated April 2014.

What is a vernal pool?

Vernal pools, also known as ephemeral wetlands, prairie potholes, whale wallows, sinks, and kettles are rain-filled depressions that amphibians use for breeding and laying egg masses. These pools can be as small as a puddle. They fill with water in the spring and are usually dried up by June or July. The reason some amphibians use these areas for breeding and laying egg masses is simple — they lack predators (fish) that eat their larvae. Source Credit: Amphibians and Vernal Pools, National Park Service.

Although the preceding quotation is focused on the reason amphibians prefer vernal pools, many odonates prefer fishless pools for the same reason as amphibians.

What does a vernal pool look like?

Many recent posts in my photoblog feature the phrase, “spotted near a vernal pool in the forest at Huntley Meadows Park.” The following photos show one of my favorite vernal pools at the park, as it appeared on 04 November 2014. This vernal pool is located in a small meadow in the forest — it isn’t very big and it’s not very deep, but it has proven to be a location favored by many uncommon odonates.

Related Resources:

• Stewardship of Vernal Pools, by Fairfax County Park Authority
• Vernal Pools, by Alonso Abugattas, Natural Resources Manager for Arlington County at Arlington County Parks and Recreation
• Amphibians and Vernal Pools, by National Park Service

Tech Tips: I used my Panasonic Lumix DMC-FZ150 superzoom camera to shoot the three preceding photos. The camera was set for manual focus and aperture priority; the lens was focused at the hyperfocal distance for an aperture of f/4, based upon the instructions provided in the excellent video tutorial by Graham Houghton, “Panasonic Lumix FZ camera easier manual focus method — super point-and-shoot tip.” Focusing at the hyperfocal distance is a technique used in landscape photography that maximizes depth-of-field. For example, when my camera is set for maximum wide angle at an aperture of f/4, everything is in focus from approximately three feet to infinity — that’s DEEP depth-of-field!

Look closely at the upper part of the full-size version of all three photos. The purple fringing that appears along the edges of some tree limbs is called chromatic aberration; color fringing occurs sometimes in photographs of high contrast subjects such as the dark tree limbs against a bright sky. Adobe Lightroom 5 features several photo editing tools that work well for removing chromatic aberration. If the images featured in this post were fine-art landscape photos, then I would edit the images to remove the chromatic aberration. In this case, the photos are intended to show what a vernal pool looks like, and they are good enough for that purpose, warts and all.

Copyright © 2014 Walter Sanford. All rights reserved.

Tags: Huntley Meadows Park, hyperfocal distance, odonate habitat, vernal pool