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Conduct Your Own Earthworm & Habitat StudiesIn this section of the web site you will find instructions and data sheets for conducting your own plot based earthworm surveys. We ask you to submit this data along with some basic habitat and location information to add to the growing database of the Great Lakes Worm Watch program. Answers to the most commonly asked questions when conducting your own surveys are provided below. For those who don’t want to do plot based surveys, but still want to contribute to our database, go to documenting an earthworm occurrence. Once your survey is completed, please mail photocopies of the completed data forms and any specimens you collected to us:
For those who are conducting plot based surveys, there are three levels of earthworm identification you can choose to provide us:
What Information and Data We Want You to Report?For all 3 levels of earthworm identification, we ask for some basic habitat information, earthworm sampling information and the numbers and/or biomass of earthworms you sampled; so that your data is as useable as possible for both anticipated and unanticipated uses! Jump down to details on what kind of earthworm data we are asking you to submit. General Site and Sampling InformationThis includes your site name (i.e. nature center, preserve, school forest, etc.) and contact information as well as the date of your sample (day/month/year) and the names of the observers or data collectors. Geographic Location of the habitat being sampledYou can get the latitude and longitude of your habitat using a GPS unit, off of a topographic map, or through one of many online mapping tools. Also be sure to include the NAD used for your location data (to find our what a NAD is click here) Here are links to a few. If you know of others, please let us know so we can provide links for others to use!
Habitat Being SampledA given site (nature center, school forest, etc.) may have several different habitat types (hardwood forests, conifer forests, restored prairie, wetlands, etc.). In general, you want to report your data for each habitat separately so the data sheet includes a section to help you describe your habitat in a general but valuable manner, including habitat type, current and past disturbance, habitat size, surrounding land use and some basic soil features. Basic Soil FeaturesThe level of impact of an earthworm invasion can, in part, be seen through the affects on the forest soils. When there are lots of earthworms the formerly thick forest floor (duff layer) composed of slowly decomposing leaves is eatten and mixed into the mineral soil below. So, for plot based surveys, we ask you to tell us how much exposed bare soil there is, some features of the forest floor, and to do a simple soil texture test. To read more about how, click here. If you want to explore other aspects fo the forest soils, click here check out the soil sampling methods section. Earthworm Sampling InformationHere you will record the sample plot size you used, the number of plots you sampled, the sample method(s) used, what sampling strategy you used to decide where to place your sample plots and what identification reference (if any) you used to identify your earthworms. See the frequently asked questions about these sampling questions below. Earthworm DataNo matter what level of earthworm identification you choose, the minimum data we ask you to submit is the density (number of earthworms) per sample plot. In addition to earthworm density, you could also submit the biomass of your earthworms per sample plot. Biomass data can be valuable when asking certain questions but is a bit trickier to calculate for earthworms than you might think. So if you are interested or motivated to do some simple measurements and use a spreadsheet to calculate biomass, we would appreciate the additional data. Learn more about how to calculate earthworm biomass or download a spreadsheet that will help you. Two other optional steps you can take with your data before submitting it are:
Remember, while there are several optional types of data you can submit (see the data sheets), the minimum we ask for is density per sample plot. ALL data submitted is valuable. Don’t be shy, submit what data you can given your goals and interest level! Commonly Asked Questions When Conducting Your Own Earthworm SurveysQ: How Do I Decide Which Sampling Methods To Use?A: There is no one method that is always better. It depends on the objectives of your particular study. For example, if your objective is to simply generate a complete species list the Flip & Strip method may be a good choice, but if your objective is to get data on relative abundance of different ecological groups or species the Liquid Extraction or Hand Sampling methods might be a good choice. Sometimes, a combination of sampling methods is best, especially if you want to see how the different methods can provide different results. See Earthworm Sampling Methods for descriptions of the most appropriate use of each sampling method, and remember to HAVE FUN! Q: How Do I Determine The Size And Shape Of My Sample Plots?A: For most studies of earthworms, a standard sample plot size of 33cm x 33cm is used. This area is large enough to be meaningful but small enough to be practically sampled using a range of methods (Hand Sampling, Liquid Extraction and Midden Counts). It also makes converting the data to “per m²” easy so your data can be readily compared to other peoples data (read more about converting your data to “per m²”) However, one plot of this size is rarely adequate to give a full and accurate sampling of the earthworm population for a site. So, you should plan on using multiple sample plots. Q: How Do I Determine How Many Samples To Collect?A: The general rule of thumb is that more samples are better. So, plan on collecting data from as many sample plots as you can given your time and resources. The minimum for any quality data is 3 sample plots, because you need at least 3 values to calculate a valid average. For more detailed strategies for determining how many samples are needed see the Research Methods. Q: How Do I Determine Where To Put My Sample Plots In My Site?A: When in doubt randomize! Like most organisms, earthworms are not evenly distributed across any given area they inhabit. So, it is wise to distribute your sample plots across your site in order to get the best average measurement for your site. One way to randomly place sample plots is to put a grid over a map or picture of your study site and then use dice or random numbers to decide which gird cell to sample. Read more details on determining where to sample. Q: How Do I Determine When to Sample?A: Two biological factors are important to consider when deciding when to sample for earthworms. First, earthworm populations are dominated by juveniles in the spring with more adults in the fall. Since most earthworms need to be adults in order to be identified to species, the best results will come from a fall sampling. However, don’t let this stop you from sampling at other times. You can still get interesting results and you may even want to consider sampling several times from spring through fall to see how the population changes with the season! Second, if soil conditions are too hot, dry or cold earthworms will become inactive and some can even enter a metabolically depressed state called aestivation (earthworm version of hibernation). If the earthworms are inactive, they will not respond as well to the liquid extraction method of sampling or some species may have moved deeper into the soil so they could be missed when using the hand sampling method. In the Great Lakes Region, earthworms are usually active between May – September. In early spring watch for the first earthworms on the sidewalk with spring rains as an indication that activity has begun. Mid-summer can be a time when soils are very dry and earthworms become inactive, so if you are planning a summer-time sampling, be aware of the soil moisture conditions. In the fall, earthworms usually become inactive soon after hard frosts begin, but if conditions remain warm later they will stay active too. September is usually a good bet for weather conditions and getting a lot of adult earthworms! Finally, you have to consider practical issues in the decision of when to sample as well. Do it when you can, but when interpreting your data, consider how the timing of your samples may have affected your results. |
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