This past month I have been working at Black Rock Forest, a research and educational forest located in Cornwall, NY. I am interested in the changes in mesofauna, soil-dwelling animals that are about a few millimeters in size, to forest disturbances. If you want to learn more about soil biodiversity and why my project is important, you can watch my video featured in Breaking Bio Blitz in the previous post. This post will focus on my fieldwork and the methods I have been using to collect all the animals living on the soil.
The forest disturbance part of my project was inspired by an on-going long-term experiment at Black Rock Forest. Named the “Future of Oak Forests Study,” this project was initiated in 2008, and includes different tree girdling experiments, with an emphasis on the girdling of red oak trees to simulate an increasingly common scenario where sudden oak death takes over a forest. A smaller portion of this experiment includes herbivore exclosures, where parts of the forest are fenced off in order to prevent feeding by large and medium herbivores which, at Black Rock, are deer. You can read about the experiment here.
Photo: A girdled red oak tree, Black Rock Forest, October 2013
Working in these experimental plots is a unique experience. In certain areas, you are surrounded by girdled trees, which are trees that have been sawed around the trunk at breast height so the trees are still standing but are functionally dead. In herbivore exclosures, the vegetation, light intensity and overall appearance of the forest is very different.
Many studies in this experiment area have obviously focused on the aboveground response of vegetation to the removal and death of oaks and the removal of major herbivores. I am interested in what was going on in the soil and leaf litter. In order to collect mesofauna, which are so small that you can only really see their general form with the naked eye, I had to collect leaf litter at the surface of the forest floor and soils at different depths. I used a soil corer, which is made up to two, very heavy parts: a slam hammer, to drive down into the soil and a metal cylinder, to collect the soil. By placing the metal cylinder upright on top of the soil, after the leaf litter has been removed, I lift the hammer and drive it down into the ground about 10 centimeters, which is sometimes a lot more difficult than one would expect. Once the cylinder was full of soil (and not rocks, which I found to be very problematic in certain areas of the forest), I had to gently extract it from the ground and place the soil into (properly labeled) bags. I took many, many cores in different part of the experimental area for both mesofauna collection as well as soil physical and chemical properties analysis.
Photos: My Berlese funnel set-up, Black Rock Forest, July 2014
Once I collected all my soils and leaf litter, the mesofauna had to be collected from the different mediums. The outstanding and universally applied method of doing this type of arthropod extraction is a Berlese funnel. The principle of a Berlese funnel is to use both heat and light to drive the animals out of the medium and into vials of ethanol to be collected and sorted later. The leaf litter and soils were placed into large funnels resting below a light bulb, the source of heat and light, with the end of the funnel falling into a vial of ethanol. By letting the soils and leaf litter dry out for three days, I expected to get most of the arthropods and other animals to migrate away from the light bulb and fall into the ethanol. As of right now, all my soils and leaf litter have been “extracted” and I have a bunch of ethanol vials filled with mesofauna and other animals and arthropods to be counted and sorted. I’m hoping to be able to identify the major mesofauna groups (as well as a few subgroups) and determine whether or not the forest disturbances are having a significant effect on these communities.
Though I’m sad that my fieldwork and funnel days are over, I am looking forward to seeing all the litter critters that have been living in the leaf litter and soil under the microscope as I start the next part of my summer research.